SALT, ACID GENERATOR, RESIN, RESIST COMPOSITION AND METHOD FOR PRODUCING RESIST PATTERN

Abstract

A salt represented by formula (I), an acid generator, a resin, and a resist composition including the same.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a salt, an acid generator, a resin, a resist composition and a method for producing a resist pattern.

Description of the Related Art

JP 2007-197718 A mentions a salt represented by the following formula.

SUMMARY OF THE INVENTION

The present invention provides a salt forming a resist pattern with resolution which is better than that of a resist pattern formed by the above resist compositions.

The present invention includes the following inventions.

[1] A salt represented by formula (I):

wherein, in formula (I),

R¹ and R² each independently represent a hydroxy group, —O—R¹⁰, —O—CO—O—R¹⁰ or —O-L1-CO—O—R¹⁰,

L¹ represents an alkanediyl group having 1 to 6 carbon atoms,

R⁴, R⁵, R⁷ and R⁸ each independently represent a halogen atom, a haloalkyl group having 1 to 12 carbon atoms or a hydrocarbon group having 1 to 18 carbon atoms, the hydrocarbon group may have a substituent, and —CH₂— included in the haloalkyl group and the hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO₂—,

R¹⁰ represents an acid-labile group,

A¹ and A² each independently represent a hydrocarbon group having 1 to 20 carbon atoms, the hydrocarbon group may have a substituent, and —CH₂— included in the hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO₂—,

m1 represents an integer of 1 to 5, and when m1 is 2 or more, a plurality of groups in parentheses may be the same or different from each other,

m2 represents an integer of 0 to 5, and when m2 is 2 or more, a plurality of groups in parentheses may be the same or different from each other,

m4 represents an integer of 0 to 4, and when m4 is 2 or more, a plurality of R⁴ may be the same or different from each other,

m5 represents an integer of 0 to 4, and when m5 is 2 or more, a plurality of R⁵ may be the same or different from each other,

m7 represents an integer of 0 to 4, and when m7 is 2 or more, a plurality of R⁷ may be the same or different from each other,

m8 represents an integer of 0 to 5, and when m8 is 2 or more, a plurality of R⁸ may be the same or different from each other,

in which 1≤m1+m7≤5, 0≤m2+m8≤5,

Q^b1 and Q^b2 each independently represent a hydrogen atom, a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms or an alkyl group having 1 to 6 carbon atoms,

L^b1 represents a divalent saturated hydrocarbon group having 1 to 24 carbon atoms, —CH₂— included in the divalent saturated hydrocarbon group may be replaced by —O— or —CO—, and a hydrogen atom included in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group,

Y^b1 represents a single bond or an alicyclic hydrocarbon group having 3 to 24 carbon atoms which may have a substituent, and —CH₂— included in the alicyclic hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO₂—,

R^bb1 represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom,

X¹⁰ represents a single bond, *—O—**, *—CO—O—**, *—O—CO—O—** or *-Ax-Ph-Ay-**,

Ph represents a phenylene group which may have a substituent,

Ax represents one bond species selected from the group consisting of a single bond, an ether bond, a thioether bond, an ester bond and a carbonic acid ester bond,

Ay represents one bond species selected from the group consisting of a single bond, an ether bond, a thioether bond, an ester bond and a carbonic acid ester bond,

* and ** represent bonding sites, and * represents a bonding site to carbon atoms to which —R^bb1 is bonded, and

L¹⁰ represents a single bond or a hydrocarbon group having 1 to 36 carbon atoms which may have a substituent, and —CH₂— included in the hydrocarbon group may be replaced by —O—, —S—, —SO₂— or —CO—.

[2] The salt according to [1], wherein A¹ is ***—X⁰1-L⁰¹- or ***L⁰¹-X⁰¹—, A² is ***—X⁰²-L⁰²- or ***-L⁰²-X⁰²—, X⁰¹ and X⁰² each independently represent —O—, —CO—, —S— or —SO₂—, L⁰¹ and L⁰² each independently represent a single bond or a hydrocarbon group having 1 to 18 carbon atoms, the hydrocarbon group may have a substituent, and —CH₂— included in the hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO₂—, and *** represents a bonding site to the benzene ring to which R¹ or R² is bonded.[3] The salt according to [2], wherein X⁰¹ and X⁰² are each independently —O— or —S—.[4] The salt according to [2] or [3], wherein L⁰¹ and L⁰² are each independently a single bond or an alkanediyl group having 1 to 6 carbon atoms (—CH₂— included in the alkanediyl group may be replaced by —O— or —CO—).[5] The salt according to any one of [1] to [4], wherein R¹ and R² are each independently a hydroxy group, —O—R¹⁰ or —O-L¹-CO—O—R¹⁰.[6] The salt according to any one of [1] to [5], wherein the acid-labile group as for R¹⁰ is a group represented by formula (1a) or a group represented by formula (2a):

wherein, in formula (1a), R^aa1, R^aa2 and R^aa3 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group obtained by combining these groups, or R^aa1 and R^aa2 may be bonded to each other to form an alicyclic hydrocarbon group having 3 to 20 carbon atoms together with carbon atoms to which R^aa1 and R^aa2 are bonded, and

* represents a bonding site:

wherein, in formula (2a), R^aa1′ and R^aa2′ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, R^aa3′ represents a hydrocarbon group having 1 to 20 carbon atoms, or R^aa2′ and R^aa3′ may be bonded to each other to form a heterocyclic group having 3 to 20 carbon atoms together with —C—X^a— to which R^aa2′ and R^aa3′ are bonded, and —CH₂— included in the hydrocarbon group and the heterocyclic group may be replaced by —O— or —S—,

X^a represents an oxygen atom or a sulfur atom, and

* represents a bonding site.

[7] The salt according to any one of [1] to [6], wherein Y^b1 is a single bond or an alicyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent (—CH₂— included in the alicyclic hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO₂—).[8] The salt according to [7], wherein Y^b1 is a cyclohexanediyl group, an adamantanediyl group, a norbornanediyl group, an adamantanelactonediyl group or a norbornanelactonediyl group.[9] The salt according to any one of [1] to [8], wherein X10 is a single bond or a group represented by any one of formula (X¹⁰-1) to formula (X¹⁰-10):

wherein, in formula (X¹⁰-1) to formula (X¹⁰-10),

* and ** are bonding sites, and * represents a bonding site to carbon atoms to which —R^bb1 is bonded,

Rx represents a halogen atom, a hydroxy group, an alkyl fluoride group having 1 to 6 carbon atoms, an alkyl group having 1 to 18 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and

mx represents an integer of 0 to 4. [10] The salt according to [9], wherein X¹⁰ is a single bond or a group represented by any one of formula (X¹⁰-1) and formula (X¹⁰-5′) to formula (X¹⁰-6′):

wherein, in formula (X¹⁰-1) and formula (X¹⁰-5′) to formula (X¹⁰-6′),

* and ** are bonding sites, and * represents a bonding site to carbon atoms to which —R^bb1 is bonded.

[11] The salt according to any one of [1] to [10], wherein L¹⁰ is a single bond, an alkanediyl group having 1 to 6 carbon atoms (in which —CH₂— included in the alkanediyl group may be replaced by —O— or —CO—), a cyclic hydrocarbon group having 3 to 18 carbon atoms (in which the cyclic hydrocarbon group may have a substituent, and —CH₂— included in the cyclic hydrocarbon group may be replaced by —O—, —S—, —SO₂— or —CO—) or a group obtained by combining an alkanediyl group having 1 to 6 carbon atoms with a cyclic hydrocarbon group having 3 to 18 carbon atoms (in which the cyclic hydrocarbon group may have a substituent, —CH₂— included in the alkanediyl group may be replaced by —O— or —CO—, and —CH₂— included in the cyclic hydrocarbon group may be replaced by —O—, , —S—, —SO₂— or —CO—).[12] An acid generator comprising the salt according to any one of [1] to [11] or a structural unit derived from the salt according to any one of [1] to [11].[13] A resin including a structural unit derived from the salt according to any one of [1] to [11].[14] A resist composition comprising the acid generator according to [12].[15] The resist composition according to [14], comprising the salt represented by formula (I), and a resin including a structural unit having an acid-labile group.[16] The resist composition according to [14], comprising a resin including the structural unit derived from the salt represented by formula (I), wherein the resin including a structural unit derived from the salt represented by formula (I) further includes a structural unit having an acid-labile group.[17] The resist composition according to [16], further comprising the salt represented by formula (I).[18] The resist composition according to any one of [15] to[17], wherein the structural unit having an acid-labile group includes at least one selected from the group consisting of a structural unit represented by formula (a1-0), a structural unit represented by formula (a1-1) and a structural unit represented by formula (a1-2):

wherein, in formula (a1-0), formula (a1-1) and formula (a1-2), L^a01, L^a1 and L^a2 each independently represent —O— or *—O—(CH₂)_k1—CO—O—, k1 represents an integer of 1 to 7, and * represents a bonding site to —CO—,

R^a01, R^a4 and R^a5 each independently represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom,

R^a02, R^a03 and R^a04 each independently represent an alkyl group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group obtained by combining these groups,

R^a6 and R^a7 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group formed by combining these groups,

m1′ represents an integer of 0 to 14,

n1 represents an integer of 0 to 10, and

n1′ represents an integer of 0 to 3.

[19] The resist composition according to any one of [15] to [18], wherein the resin including a structural unit having an acid-labile group further includes a structural unit represented by formula (a2-A):

wherein, in formula (a2-A),

R^a50 represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom,

R^a51 represents a halogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, an alkoxyalkoxy group having 2 to 12 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, an acryloyloxy group or a methacryloyloxy group,

A^a50 represents a single bond or *—X^a51-(A^a52-X^a52)_nb— and * represents a bonding site to carbon atoms to which —R^a50 is bonded,

A^a52 represents an alkanediyl group having 1 to 8 carbon atoms, X^a51 and X^a52 each independently represent —O—, —CO—O— or —O—CO—,

nb represents 0 or 1, and

mb represents an integer of 0 to 4, and when mb is an integer of 2 or more, a plurality of R^a51 may be the same or different from each other.

[20] The resist composition according to any one of [14] to [19], further comprising a salt represented by formula (B1):

wherein, in formula (B1),

Q^b1 and Q^b2 each independently represent a hydrogen atom, a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms or an alkyl group having 1 to 6 carbon atoms,

L^b1 represents a divalent saturated hydrocarbon group having 1 to 24 carbon atoms, —CH₂— included in the divalent saturated hydrocarbon group may be replaced by —O— or —CO—, and a hydrogen atom included in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group,

Y represents a methyl group which may have a substituent, or an alicyclic hydrocarbon group having 3 to 24 carbon atoms which may have a substituent, and —CH₂— included in the alicyclic hydrocarbon group may be replaced by —O—, —S—, —SO₂— or —CO—, and

Z⁺ represents an organic cation.

[21] The resist composition according to any one of [14] to [20], further comprising a salt generating an acid having an acidity lower than that of an acid generated from the salt represented by formula (I).[22] A method for producing a resist pattern, which comprises:

• • (1) a step of applying the resist composition according to any one of [14] to [21] on a substrate,
  • (2) a step of drying the applied composition to form a composition layer,
  • (3) a step of exposing the composition layer,
  • (4) a step of heating the exposed composition layer, and
  • (5) a step of developing the heated composition layer.

It is possible to produce a resist pattern with satisfactory resolution by using a resist composition which uses a salt of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the present specification, “(meth)acrylic monomer” means “at least one of acrylic monomer and methacrylic monomer”. Descriptions such as “(meth)acrylate” and “(meth)acrylic acid” have the same meaning. In groups mentioned in the present specification, regarding groups capable of having both a linear structure and a branched structure, they may have either the linear or branched structure. “Combined group” means a group in which two or more exemplified groups are bonded by appropriately varying their valences, bonding forms and the like. “Derived” or “Induced” means that a polymerizable C═C bond included in the molecule becomes a —C—C— group (single bond) by polymerization. When stereoisomers exist, all stereoisomers are included.

In the present specification, “solid component of the resist composition” means the total amount of components in which the below-mentioned solvent (E) is removed from the total amount of the resist composition.

<Salt Represented by Formula (I)>

The present invention relates to a salt represented by formula (I) (hereinafter sometimes referred to as “salt (I)”).

Of the salt (I), the side having positive charge is sometimes referred to as “cation (I)”, and the side having negative charge is sometimes referred to as “anion (I)”.

[Cation (I)]

The cation (I) of the salt represented by formula (I) is a cation represented by formula (I-C).

wherein, in formula (I-C), all symbols are the same as defined in formula (I).

Examples of the alkanediyl group in L¹ included in R¹ and R² include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group and a hexane-1,6-diyl group; and

branched alkanediyl groups such as an ethane-1,1-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diyl group, a pentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group.

L¹ is preferably an alkanediyl group having 1 to 3 carbon atoms, and more preferably a methylene group.

The acid-labile group as for R¹⁰ included in R¹ and R² means a group in which a leaving group having a group represented by R¹⁰ is eliminated by contacting with an acid (e.g. trifluoromethanesulfonic acid) to form a carboxy group or a hydroxy group.

The acid-labile group is preferably a group represented by formula (1a) (hereinafter sometimes referred to as “acid-labile group (1a)”) or a group represented by formula (2a) (hereinafter sometimes referred to as “acid-labile group (2a)”):

wherein, in formula (1a), R^aa1, R^aa2 and R^aa3 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group obtained by combining these groups, or R^aa1 and R^aa2 may be bonded to each other to form an alicyclic hydrocarbon group having 3 to 20 carbon atoms together with carbon atoms to which R^aa1 and R^aa2 are bonded, and

* represents a bonding site:

wherein, in formula (2a), R^aa1′ and R^aa2′ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, R^aa3′ represents a hydrocarbon group having 1 to 20 carbon atoms, or R^aa2′ and R^aa3′ may be bonded to each other to form a heterocyclic group having 3 to 20 carbon atoms together with —C—X^a— to which R^aa2′ and R^aa3′ are bonded, and —CH₂— included in the hydrocarbon group and the heterocyclic group may be replaced by —O— or —S—,

X^a represents an oxygen atom or a sulfur atom, and

* represents a bonding site.

Examples of the alkyl group as for R^aa1, R^aa2 and R^aa3 include a methyl group, an ethyl group, a propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group and the like. The number of carbon atoms of the alkyl group as for R^aa1, R^aa2 and R^aa3 is preferably 1 to 6, more preferably 1 to 4, and still more preferably 1 to 3.

Examples of the alkenyl group as for R^aa1, R^aa2 and R^aa3 include an ethenyl group, a propenyl group, an isopropenyl group, a butenyl group, an isobutenyl group, a tert-butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, an isooctenyl group and a nonenyl group.

The alicyclic hydrocarbon group as for R^aa1, R^aa2 and R^aa3 may be either monocyclic or polycyclic. Examples of the monocyclic alicyclic hydrocarbon group include cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group and a cyclooctyl group. Examples of the polycyclic alicyclic hydrocarbon group include a decahydronaphthyl group, an adamantyl group, a norbornyl group and the following groups (* represents a bonding site). The number of carbon atoms of the alicyclic hydrocarbon group as for R^aa1, R^aa2 and R^aa3 is preferably 3 to 16, and more preferably 3 to 12.

Examples of the aromatic hydrocarbon group as for R^aa1, R^aa2 and R^aa3 include aryl groups such as a phenyl group, a naphthyl group, an anthryl group, a biphenyl group and a phenanthryl group. The number of carbon atoms of the aromatic hydrocarbon group as for R^aa1, R^aa2 and R^aa3 is preferably 6 to 14, and more preferably 6 to 10.

Examples of the combined group include groups obtained by combining the above-mentioned alkyl group and alicyclic hydrocarbon group (e.g., alkylcycloalkyl groups or cycloalkylalkyl groups, such as a methylcyclohexyl group, a dimethylcyclohexyl group, a methylnorbornyl group, a cyclohexylmethyl group, an adamantylmethyl group, an adamantyldimethyl group and a norbornylethyl group), aralkyl groups such as a benzyl group, aromatic hydrocarbon groups having an alkyl group (a p-methylphenyl group, a p-tert-butylphenyl group, a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a 2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group, etc.), aromatic hydrocarbon groups having an alicyclic hydrocarbon group (a p-cyclohexylphenyl group, a p-adamantylphenyl group, etc.), aryl-cycloalkyl groups such as a phenylcyclohexyl group, and the like.

When R^aa1 and R^aa2 are bonded to each other to form an alicyclic hydrocarbon group together with carbon atoms to which R^aa1 and R^aa2 are bonded, examples of —C(R^aa1) (R^aa2) (R^aa3) include the following groups. The alicyclic hydrocarbon group preferably has 3 to 16 carbon atoms, and more preferably 3 to 12 carbon atoms. * represents a bonding site to —O—.

Examples of the group represented by formula (1a) include a 1,1,1-trialkyl group (a group in which R^aa1, R^aa2 and R^aa3 are alkyl groups in formula (1a), and preferably a tert-butyl group), a 2-alkyladamantan-2-yl group (a group in which R^aa1, R^aa2, and carbon atom to which R^aa1 and R^aa2 are bonded form an adamantyl group, and R^aa3 is an alkyl group in formula (1a)) and a 1-(adamantan-1-yl)-1,1-dialkyl group (a group in which R^aa1 and R^aa2 are alkyl groups, and R^aa3 is an adamantyl group in formula (1a)).

Examples of the hydrocarbon group as for R^aa1′, R^aa2′ and R^aa3′ include an alkyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and groups formed by combining these groups.

Examples of the alkyl group and the alicyclic hydrocarbon group include the same groups as exemplified in R^aa1, R^aa2 and R^aa3.

Examples of the aromatic hydrocarbon group include aryl groups such as a phenyl group, a naphthyl group, an anthryl group, a biphenyl group and a phenanthryl group.

Examples of the combined group include groups obtained by combining the above-mentioned alkyl group and alicyclic hydrocarbon group (e.g., cycloalkylalkyl groups or alkylcycloalkyl groups, such as a methylcyclohexyl group, a dimethylcyclohexyl group, a methylnorbornyl group, a cyclohexylmethyl group, an adamantylmethyl group, an adamantyldimethyl group and a norbornylethyl group), aralkyl groups such as a benzyl group, aromatic hydrocarbon groups having an alkyl group (a p-methylphenyl group, a p-tert-butylphenyl group, a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a 2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group, etc.), aromatic hydrocarbon groups having an alicyclic hydrocarbon group (a p-cyclohexylphenyl group, a p-adamantylphenyl group, etc.), aryl-cycloalkyl groups such as a phenylcyclohexyl group, and the like.

When R^aa2′ and R^aa3′ are bonded to each other to form a heterocyclic group together with carbon atoms and X^a to which R^aa2′ and R^aa3′ are bonded, examples of —C(R^aa1′) (R^aa2′)—X^a—(R^aa3′) include the following groups. * represents a bonding site.

At least one of R^aa1′ and R^aa2′ is preferably a hydrogen atom.

Specific examples of the acid-labile group (1a) include the following groups. * represents a bonding site,

Specific examples of the acid-labile group (2a) include the following groups. * represents a bonding site.

The bonding site of R¹ and R² to the benzene ring may be each independently the o-position, the m-position or the p-position, with respect to the bonding site of A¹ and A², respectively. Particularly, R¹ and R² are each independently bonded preferably at the p-position or the m-position, and more preferably at the p-position, with respect to the bonding site of A¹ and A², respectively.

Preferably, R¹ and R² are each independently a hydroxy group, —O—R¹⁰ or —O-L¹-CO—O—R¹⁰, and more preferably —O—R¹⁰ or —O-L¹-CO—O—R¹⁰.

When m1 is 2 or more, or when m2 or m3 is 1 or more and a plurality of R¹⁰ are present, a plurality of R¹⁰ may be the same or different from each other.

Examples of the halogen atom as for R⁴, R⁵, R⁷ and R⁸ include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

The haloalkyl group having 1 to 12 carbon atoms as for R⁴, R⁵, R⁷ and R⁸ represents an alkyl group having 1 to 12 carbon atoms which has a halogen atom, and examples thereof include an alkyl fluoride group having 1 to 12 carbon atoms, an alkyl chloride group having 1 to 12 carbon atoms, an alkyl bromide group having 1 to 12 carbon atoms, an alkyl iodide group having 1 to 12 carbon atoms and the like. Examples of the haloalkyl group include a perfluoroalkyl group having 1 to 12 carbon atoms (a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, a nonafluorobutyl group, etc.), a 2,2,2-trifluoroethyl group, a 3,3,3-trifluoropropyl group, a 4,4,4-trifluorobutyl group, a 3,3,4,4,4-pentafluorobutyl group, a chloromethyl group, a bromomethyl group, an iodomethyl group and the like. The number of carbon atoms of the haloalkyl group is preferably 1 to 9, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

Examples of the hydrocarbon group having 1 to 18 carbon atoms as for R⁴, R⁵, R⁷ and R⁸ include a chain hydrocarbon group such as an alkyl group or an alkanediyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and groups formed by combining these groups.

Examples of the alkyl group include linear or branched alkyl groups, for example, alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, a decyl group, an undecyl group and a dodecyl group

The alkanediyl group is a linear or branched alkanediyl group, and examples thereof include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group and a hexane-1,6-diyl group; and

branched alkanediyl groups such as an ethane-1,1-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diyl group, a pentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group.

The number of carbon atoms of the chain hydrocarbon group is preferably 1 to 12, more preferably 1 to 9, still more preferably 1 to 6, yet more preferably 1 to 4, and further preferably 1 to 3.

The alicyclic hydrocarbon group may be either monocyclic or polycyclic, and examples thereof include groups shown below. The bonding site can be any position.

Specific examples of the monocyclic alicyclic hydrocarbon group include monocyclic cycloalkyl groups such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group and a cyclododecyl group. Examples of the polycyclic alicyclic hydrocarbon group include polycyclic cycloalkyl groups such as a decahydronaphthyl group, an adamantyl group and a norbornyl group. The number of carbon atoms of the alicyclic hydrocarbon group is preferably 3 to 18, more preferably 3 to 16, and still more preferably 3 to 12.

Examples of the aromatic hydrocarbon group include a phenyl group, a naphthyl group, a biphenyl group, an anthryl group, a phenanthryl group, a binaphthyl group and the like. The number of carbon atoms of the aromatic hydrocarbon group is preferably 6 to 18, more preferably 6 to 14, and still more preferably 6 to 10.

Examples of the group formed by combining two or more groups of the chain hydrocarbon group, the alicyclic hydrocarbon group and the aromatic hydrocarbon group include groups formed by combining an aromatic hydrocarbon group with a chain hydrocarbon group (e.g., the aromatic hydrocarbon group-alkanediyl group-*, the alkyl group-aromatic hydrocarbon group-*, the alkyl group-aromatic hydrocarbon group-alkanediyl group-*, and —CH₂— included in the alkanediyl group and the alkyl group may be replaced by —O—, —CO—, —S— or —SO₂—), groups formed by combining an alicyclic hydrocarbon group with a chain hydrocarbon group (e.g., the alicyclic hydrocarbon group-alkanediyl group-*, the alkyl group-alicyclic hydrocarbon group-*, the alkyl group-alicyclic hydrocarbon group-alkanediyl group-*, and —CH₂— included in the alicyclic hydrocarbon group, the alkanediyl group and the alkyl group may be replaced by —O—, —CO—, —S— or —SO₂—) and groups formed by combining an aromatic hydrocarbon group with an alicyclic hydrocarbon group (e.g., the aromatic hydrocarbon group-alicyclic hydrocarbon group-*, the alicyclic hydrocarbon group-aromatic hydrocarbon group-* and —CH₂— included in the alicyclic hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO₂—). * represents a bonding site.

Examples of the aromatic hydrocarbon group-alkanediyl group-* include aralkyl groups such as a benzyl group and a phenethyl group.

Examples of the alkyl group-aromatic hydrocarbon group-* include a tolyl group, a xylyl group, a cumenyl group and the like.

Examples of the alicyclic hydrocarbon group-alkanediyl group-* include cycloalkylalkyl groups such as a cyclohexylmethyl group, a cyclohexylethyl group, a 1-(adamantan-1-yl)methyl group and a 1-(adamantan-1-yl)-1-methylethyl group.

Examples of the alkyl group-alicyclic hydrocarbon group-* include cycloalkyl groups having an alkyl group, such as a methylcyclohexyl group, a dimethylcyclohexyl group and a 2-alkyladamantan-2-yl group.

Examples of the aromatic hydrocarbon group-alicyclic hydrocarbon group-* include a phenylcyclohexyl group and the like.

Examples of the alicyclic hydrocarbon group-aromatic hydrocarbon group-* include a cyclohexylphenyl group and the like.

In combination, two or more of alicyclic hydrocarbon groups, aromatic hydrocarbon groups and chain hydrocarbon groups may be respectively combined. Any group of the combined groups may also be bonded to the benzene ring.

When —CH₂— included in the haloalkyl group or hydrocarbon group represented by R⁴, R⁵, R⁷ and R⁸ is replaced by —O—, —CO—, —S—, or —SO₂—, the number of carbon atoms before replacement is taken as the total number of the haloalkyl group or hydrocarbon group. The number may be either 1, or 2 or more.

Examples of the group in which —CH₂— included in the haloalkyl group and the hydrocarbon group is replaced by —O—, —S—, —SO₂— or —CO— include a hydroxy group (a group in which —CH₂— included in the methyl group is replaced by —O—), a thiol group (a group in which —CH₂— included in the methyl group is replaced by —S—), a carboxy group (a group in which —CH₂—CH₂— included in the ethyl group is replaced by —O—CO—), an alkoxy group (a group in which —CH₂— at any position included in the alkyl group is replaced by —O—), an alkoxycarbonyl group (a group in which —CH₂—CH₂— at any position included in the alkyl group is replaced by —O—CO—), an alkylcarbonyl group (a group in which —CH₂— at any position included in the alkyl group is replaced by —CO—), an alkylcarbonyloxy group (a group in which —CH₂—CH₂— at any position included in the alkyl group is replaced by —CO—O—), an alkylthio group (a group in which —CH₂— at any position included in the alkyl group is replaced by —S—), an alkylsulfonyl group (a group in which —CH₂— at any position included in the alkyl group is replaced by —SO₂—), an oxy group (a group in which —CH₂— included in the methylene group is replaced by —O—), a carbonyl group (a group in which —CH₂— included in the methylene group is replaced by —CO—), a thio group (a group in which —CH₂— included in the methylene group is replaced by —S—), a sulfonyl group (a group in which —CH₂— included in the methylene group is replaced by —SO₂—), an alkanediyloxy group (a group in which —CH₂— at any position included in the alkanediyl group is replaced by —O—), an alkanediyloxycarbonyl group (a group in which —CH₂—CH₂— at any position included in the alkanediyl group is replaced by —O—CO—), an alkanediylcarbonyl group (a group in which —CH₂— at any position included in the alkanediyl group is replaced by —CO—), an alkanediylcarbonyloxy group (a group in which —CH₂—CH₂— at any position included in the alkanediyl group is replaced by —CO—O—), an alkanediylthio group (a group in which —CH₂— at any position included in the alkanediyl group is replaced by —S—), an alkanediylsulfonyl group (a group in which —CH₂— at any position included in the alkanediyl group is replaced by —SO₂—), a cycloalkoxy group, a cycloalkylalkoxy group, an alkoxycarbonyloxy group, an aromatic hydrocarbon group-carbonyloxy group, an aromatic hydrocarbon group-carbonyl group, an aromatic hydrocarbon group-oxy group, a haloalkoxy group (a group in which —CH₂— at any position included in the haloalkyl group is replaced by —O—), a haloalkoxycarbonyl group (a group in which —CH₂—CH₂— at any position included in the haloalkyl group is replaced by —O—CO—), a haloalkylcarbonyl group (a group in which —CH₂— at any position included in the haloalkyl group is replaced by —CO—), a haloalkylcarbonyloxy group (a group in which —CH₂—CH₂— at any position included in the haloalkyl group is replaced by —CO—O—), and a group obtained by combining two or more of these groups.

Examples of the alkoxy group include alkoxy groups having 1 to 17 carbon atoms, for example, a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, an octyloxy group, a 2-ethylhexyloxy group, a nonyloxy group, a decyloxy group, an undecyloxy group and the like. The number of carbon atoms of the alkoxy group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

The alkoxycarbonyl group, the alkylcarbonyl group and the alkylcarbonyloxy group represent a group in which a carbonyl group or a carbonyloxy group is bonded to the above-mentioned alkyl group or alkoxy group.

Examples of the alkoxycarbonyl group include alkoxycarbonyl groups having 2 to 17 carbon atoms, for example, a methoxycarbonyl group, an ethoxycarbonyl group, a butoxycarbonyl group and the like. Examples of the alkylcarbonyl group include alkylcarbonyl groups having 2 to 18 carbon atoms, for example, an acetyl group, a propionyl group and a butyryl group. Examples of the alkylcarbonyloxy group include alkylcarbonyloxy groups having 2 to 17 carbon atoms, for example, an acetyloxy group, a propionyloxy group, a butyryloxy group and the like. The number of carbon atoms of the alkoxycarbonyl group is preferably 2 to 11, more preferably 2 to 6, still more preferably 2 to 4, and yet more preferably 2 or 3. The number of carbon atoms of the alkylcarbonyl group is preferably 2 to 12, more preferably 2 to 6, still more preferably 2 to 4, and yet more preferably 2 or 3. The number of carbon atoms of the alkylcarbonyloxy group is preferably 2 to 11, more preferably 2 to 6, still more preferably 2 to 4, and yet more preferably 2 or 3. Examples of the alkylthio group include alkylthio groups having 1 to 17 carbon atoms, for example, a methylthio group, an ethylthio group, a propylthio group, a butylthio group, a pentylthio group, a hexylthio group, an octylthio group, a 2-ethylhexylthio group, a nonylthio group, a decylthio group, an undecylthio group and the like. The number of carbon atoms of the alkylthio group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

Examples of the alkylsulfonyl group include alkylsulfonyl groups having 1 to 17 carbon atoms, for example, a methylsulfonyl group, an ethylsulfonyl group, a propylsulfonyl group, a butylsulfonyl group, a pentylsulfonyl group, a hexylsulfonyl group, an octylsulfonyl group, a 2-ethylhexylsulfonyl group, a nonylsulfonyl group, a decylsulfonyl group, an undecylsulfonyl group and the like. The number of carbon atoms of the alkylsulfonyl group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

Examples of the alkanediyloxy group include alkanediyloxy groups having 1 to 17 carbon atoms, for example, a methyleneoxy group, an ethyleneoxy group, a propanediyloxy group, a butanediyloxy group, a pentanediyloxy group and the like. The number of carbon atoms of the alkanediyloxy group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

Examples of the alkanediyloxycarbonyl group include alkanediyloxycarbonyl groups having 2 to 17 carbon atoms, for example, a methyleneoxycarbonyl group, an ethyleneoxycarbonyl group, a propanediyloxycarbonyl group, a butanediyloxycarbonyl group and the like. Examples of the alkanediylcarbonyl group include alkanediylcarbonyl groups having 2 to 18 carbon atoms, for example, a methylenecarbonyl group, an ethylenecarbonyl group, a propanediylcarbonyl group, a butanediylcarbonyl group, a pentanediylcarbonyl group and the like. Examples of the alkanediylcarbonyloxy group include alkanediylcarbonyloxy groups having 2 to 17 carbon atoms, for example, a methylenecarbonyloxy group, an ethylenecarbonyloxy group, a propanediylcarbonyloxy group, a butanediylcarbonyloxy group and the like. The number of carbon atoms of the alkanediyloxycarbonyl group is preferably 2 to 11, more preferably 2 to 6, still more preferably 2 to 4, and yet more preferably 2 or 3. The number of carbon atoms of the alkanediylcarbonyl group is preferably 2 to 12, more preferably 2 to 6, still more preferably 2 to 4, and yet more preferably 2 or 3. The number of carbon atoms of the alkanediylcarbonyloxy group is preferably 2 to 11, more preferably 2 to 6, still more preferably 2 to 4, and yet more preferably 2 or 3.

Examples of the alkanediylthio group include alkanediylthio groups having 1 to 17 carbon atoms, for example, a methylenethio group, an ethylenethio group, a propylenethio group and the like. The number of carbon atoms of the alkanediylthio group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

Examples of the alkanediylsulfonyl group include alkanediylsulfonyl groups having 1 to 17 carbon atoms, for example, a methylenesulfonyl group, an ethylenesulfonyl group, a propylenesulfonyl group and the like. The number of carbon atoms of the alkanediylsulfonyl group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

Examples of the cycloalkoxy group include cycloalkoxy groups having 3 to 17 carbon atoms, for example, a cyclohexyloxy group and the like. Examples of the cycloalkylalkoxy group include cycloalkylalkoxy groups having 4 to 17 carbon atoms, for example, a cyclohexylmethoxy group and the like. Examples of the alkoxycarbonyloxy group include alkoxycarbonyloxy groups having 2 to 16 carbon atoms, for example, a butoxycarbonyloxy group and the like. Examples of the aromatic hydrocarbon group-carbonyloxy group include aromatic hydrocarbon group-carbonyloxy groups having 7 to 17 carbon atoms, for example, a benzoyloxy group and the like. Examples of the aromatic hydrocarbon group-carbonyl group include aromatic hydrocarbon group-carbonyl groups having 7 to 18 carbon atoms, for example, a benzoyl group and the like. Examples of the aromatic hydrocarbon group-oxy group include aromatic hydrocarbon group-oxy groups having 6 to 17 carbon atoms, for example, a phenyloxy group and the like.

Examples of the haloalkoxy group, the haloalkoxycarbonyl group, the haloalkylcarbonyl group and the haloalkylcarbonyloxy group include haloalkoxy groups having 1 to 11 carbon atoms, haloalkoxycarbonyl groups having 2 to 11 carbon atoms, haloalkylcarbonyl groups having 2 to 12 carbon atoms and haloalkylcarbonyloxy groups having 2 to 11 carbon atoms, for example, groups in which one or more hydrogen atoms of the above-mentioned groups are substituted with a halogen atom.

Examples of the group in which —CH₂— included in the alicyclic hydrocarbon group is replaced by —O—, —S—, —SO₂— or —CO— include the following groups. Of the following groups, it is possible to exemplify groups in which —O— is replaced by —S— or —CO— is replaced by —SO₂—, respectively. The bonding site can be any position.

Examples of the substituent which may be possessed by the hydrocarbon group as for R⁴, R⁵, R⁷ and R⁸ include a halogen atom, a cyano group and an alkyl group having 1 to 12 carbon atoms (—CH₂— included in the alkyl group may be replaced by —O— or —CO—).

Examples of the halogen atom include the same groups as mentioned above.

Examples of the alkyl group having 1 to 12 carbon atoms include the same groups as mentioned above.

When —CH₂— included in the alkyl group as the substituent is replaced by —O— or —CO—, the number of carbon atoms before replacement is taken as the total number of the alkyl group. Examples of the replaced group include a hydroxy group, a carboxy group, an alkoxy group, an alkoxycarbonyl group, an alkylcarbonyl group, an alkylcarbonyloxy group and the like.

Examples of the alkoxy group, the alkoxycarbonyl group, the alkylcarbonyl group and the alkylcarbonyloxy group include an alkoxy group having 1 to 11 carbon atoms, an alkoxycarbonyl group having 2 to 11 carbon atoms, an alkylcarbonyl group having 2 to 12 carbon atoms and an alkylcarbonyloxy group having 2 to 11 carbon atoms, and include the same groups as mentioned above.

The hydrocarbon group may have one substituent or a plurality of substituents.

Examples of the hydrocarbon group as for A¹ and A² include linear or branched chain hydrocarbon groups (e.g., an alkanediyl group, etc.), monocyclic or polycyclic alicyclic hydrocarbon groups, aromatic hydrocarbon groups and the like, and the hydrocarbon group may be groups formed by combining two or more of these groups. The number of carbon atoms of the hydrocarbon group is preferably 1 to 19, more preferably 1 to 18, still more preferably 1 to 16, yet more preferably 1 to 14, and further preferably 1 to 12.

Examples of the chain hydrocarbon group include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diyl group, a dodecane-1,12-diyl group, a tridecane-1,13-diyl group, a tetradecane-1,14-diyl group, a pentadecane-1,15-diyl group, a hexadecane-1,16-diyl group and a heptadecane-1,17-diyl group; and

branched alkanediyl groups such as an ethane-1,1-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diyl group, a pentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group.

The number of carbon atoms of the chain hydrocarbon group is preferably 1 to 18, more preferably 1 to 12, still more preferably 1 to 9, yet more preferably 1 to 6, further preferably 1 to 4, and still further preferably 1 to 3.

The alicyclic hydrocarbon group may be either monocyclic or polycyclic, and examples thereof include groups show below. The bonding site can be any position.

Specific examples thereof include monocyclic alicyclic hydrocarbon groups which are monocyclic cycloalkanediyl groups such as a cyclobutane-1,3-diyl group, a cyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group and a cyclooctane-1,5-diyl group; and polycyclic alicyclic hydrocarbon groups which are polycyclic cycloalkanediyl groups such as a norbornane-1,4-diyl group, a norbornane-2,5-diyl group, an adamantane-1,5-diyl group and an adamantane-2,6-diyl group.

The number of carbon atoms of the alicyclic hydrocarbon group is preferably 3 to 18, more preferably 3 to 16, still more preferably 3 to 12, and yet more preferably 3 to 10.

Examples of the aromatic hydrocarbon group include aromatic hydrocarbon groups, for example, arylene groups such as a phenylene group, a naphthylene group, an anthrylene group, a biphenylene group and a phenanthrylene group. The number of carbon atoms of the aromatic hydrocarbon group is preferably 6 to 18, more preferably 6 to 14, and still more preferably 6 to 10.

Examples of the group formed by combining two or more groups include groups formed by combining an alicyclic hydrocarbon group with an alkanediyl group, groups formed by combining an aromatic hydrocarbon group with an alkanediyl group, and groups formed by combining an alicyclic hydrocarbon group with an aromatic hydrocarbon group. In combination, two or more of chain hydrocarbon groups, alicyclic hydrocarbon groups and aromatic hydrocarbon groups may be respectively combined. Any group may be bonded to the benzene ring.

Examples of the group formed by combining an alicyclic hydrocarbon group with an alkanediyl group include a -divalent alicyclic hydrocarbon group-alkanediyl group-, an -alkanediyl group-divalent alicyclic hydrocarbon group-alkanediyl group-, an -alkanediyl group-divalent alicyclic hydrocarbon group- and the like.

Examples of the group formed by combining an aromatic hydrocarbon group with an alkanediyl group include a -divalent aromatic hydrocarbon group-alkanediyl group-, an -alkanediyl group-divalent aromatic hydrocarbon group-alkanediyl group-, an -alkanediyl group-divalent aromatic hydrocarbon group- and the like.

Examples of the group formed by combining an alicyclic hydrocarbon group with an aromatic hydrocarbon group include an -aromatic hydrocarbon group-alicyclic hydrocarbon group-, an -alicyclic hydrocarbon group-aromatic hydrocarbon group-, an -alicyclic hydrocarbon group-aromatic hydrocarbon group—an alicyclic hydrocarbon group—and the like.

In A¹ and A², when —CH₂— included in the hydrocarbon group is replaced by —O—, —CO—, —S— or —SO₂—, the number of carbon atoms before replacement is taken as the total number of the hydrocarbon group. The number may be either 1, or 2 or more, and is preferably 1 to 3.

Examples of the group in which —CH₂— included in the hydrocarbon group is replaced by —O—, —CO—, —S— or —SO₂— include a hydroxy group (a group in which —CH₂— included in the methyl group is replaced by —O—), a carboxy group (a group in which —CH₂—CH₂— included in the ethyl group is replaced by —O—CO—), a thiol group (a group in which —CH₂— included in the methyl group is replaced by —S—), an alkoxy group (a group in which —CH₂— at any position included in the alkyl group is replaced by —O—), an alkoxycarbonyl group (a group in which —CH₂—CH₂— at any position included in the alkyl group is replaced by —O—CO—), an alkylcarbonyl group (a group in which —CH₂— at any position included in the alkyl group is replaced by —CO—), an alkylcarbonyloxy group (a group in which —CH₂—CH₂— at any position included in the alkyl group is replaced by —CO—O—), an alkylthio group (a group in which —CH₂— at any position included in the alkyl group is replaced by —S—), an alkylsulfonyl group (a group in which —CH₂— at any position included in the alkyl group is replaced by —SO₂—), an oxy group (a group in which —CH₂— included in the methylene group is replaced by —O—), a carbonyl group (a group in which —CH₂— included in the methylene group is replaced by —CO—), a thio group (a group in which —CH₂— included in the methylene group is replaced by —S—), a sulfonyl group (a group in which —CH₂— included in the methylene group is replaced by —SO₂—), an alkanediyloxy group (a group in which —CH₂— at any position included in the alkanediyl group is replaced by —O—), an alkanediyloxycarbonyl group (a group in which —CH₂—CH₂— at any position included in the alkanediyl group is replaced by —O—CO—), an alkanediylcarbonyl group (a group in which —CH₂— at any position included in the alkanediyl group is replaced by —CO—), an alkanediylcarbonyloxy group (a group in which —CH₂—CH₂— at any position included in the alkanediyl group is replaced by —CO—O—), an alkanediylsulfonyl group (a group in which —CH₂— at any position included in the alkanediyl group is replaced by —SO₂—), an alkanediylthio group (a group in which —CH₂— at any position included in the alkanediyl group is replaced by —S—), a cycloalkoxy group, a cycloalkylalkoxy group, an alkoxycarbonyloxy group, an aromatic hydrocarbon group-carbonyloxy group, an aromatic hydrocarbon group-carbonyl group, an aromatic hydrocarbon group-oxy group, a group obtained by combining two or more groups of these groups, and the like.

Examples of the alkoxy group include alkoxy groups having 1 to 19 carbon atoms, for example, a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, an octyloxy group, a 2-ethylhexyloxy group, a nonyloxy group, a decyloxy group, an undecyloxy group and the like. The number of carbon atoms of the alkoxy group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

The alkoxycarbonyl group, the alkylcarbonyl group and the alkylcarbonyloxy group represent a group in which a carbonyl group or a carbonyloxy group is bonded to the above-mentioned alkyl group or alkoxy group.

Examples of the alkoxycarbonyl group include alkoxycarbonyl groups having 2 to 19 carbon atoms, for example, a methoxycarbonyl group, an ethoxycarbonyl group, a butoxycarbonyl group and the like. Examples of the alkylcarbonyl group include alkylcarbonyl groups having 2 to 20 carbon atoms, for example, an acetyl group, a propionyl group and a butyryl group. Examples of the alkylcarbonyloxy group include alkylcarbonyloxy groups having 2 to 19 carbon atoms, for example, an acetyloxy group, a propionyloxy group, a butyryloxy group and the like. The number of carbon atoms of the alkoxycarbonyl group is preferably 2 to 11, more preferably 2 to 6, still more preferably 2 to 4, and yet more preferably 2 or 3. The number of carbon atoms of the alkylcarbonyl group is preferably 2 to 12, more preferably 2 to 6, still more preferably 2 to 4, and yet more preferably 2 or 3. The number of carbon atoms of the alkylcarbonyloxy group is preferably 2 to 11, more preferably 2 to 6, still more preferably 2 to 4, and yet more preferably 2 or 3. Examples of the alkylthio group include alkylthio groups having 1 to 19 carbon atoms, for example, a methylthio group, an ethylthio group, a propylthio group, a butylthio group and the like. The number of carbon atoms of the alkylthio group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

Examples of the alkylsulfonyl group include alkylsulfonyl groups having 1 to 19 carbon atoms, for example, a methylsulfonyl group, an ethylsulfonyl group, a propylsulfonyl group and the like. The number of carbon atoms of the alkylsulfonyl group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

Examples of the alkanediyloxy group include alkanediyloxy group having 1 to 19 carbon atoms, for example, a methyleneoxy group, an ethyleneoxy group, a propanediyloxy group, a butanediyloxy group, a pentanediyloxy group and the like. The number of carbon atoms of the alkanediyloxy group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

Examples of the alkanediyloxycarbonyl group include alkanediyloxycarbonyl groups having 2 to 19 carbon atoms, for example, a methyleneoxycarbonyl group, an ethyleneoxycarbonyl group, a propanediyloxycarbonyl group, a butanediyloxycarbonyl group and the like. Examples of the alkanediylcarbonyl group include alkanediylcarbonyl groups having 2 to 20 carbon atoms, for example, a methylenecarbonyl group, an ethylenecarbonyl group, a propanediylcarbonyl group, a butanediylcarbonyl group, a pentanediylcarbonyl group and the like. Examples of the alkanediylcarbonyloxy group include alkanediylcarbonyloxy groups having 2 to 19 carbon atoms, for example, a methylenecarbonyloxy group, an ethylenecarbonyloxy group, a propanediylcarbonyloxy group, a butanediylcarbonyloxy group and the like. The number of carbon atoms of the alkanediyloxycarbonyl group is preferably 2 to 11, more preferably 2 to 6, still more preferably 2 to 4, and yet more preferably 2 or 3. The number of carbon atoms of the alkanediylcarbonyl group is preferably 2 to 12, more preferably 2 to 6, still more preferably 2 to 4, and yet more preferably 2 or 3. The number of carbon atoms of the alkanediylcarbonyloxy group is preferably 2 to 11, more preferably 2 to 6, still more preferably 2 to 4, and yet more preferably 2 or 3.

Examples of the alkanediylsulfonyl group include alkanediylsulfonyl groups having 1 to 19 carbon atoms, for example, a methylenesulfonyl group, an ethylenesulfonyl group, a propylenesulfonyl group and the like. The number of carbon atoms of the alkanediylsulfonyl group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

Examples of the alkanediylthio group include alkanediylthio groups having 1 to 19 carbon atoms, for example, a methylenethio group, an ethylenethio group, a propylenethio group and the like. The number of carbon atoms of the alkanediylthio group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

Examples of the cycloalkoxy group include cycloalkoxy groups having 3 to 19 carbon atoms, for example, a cyclohexyloxy group and the like. Examples of the cycloalkylalkoxy group include cycloalkylalkoxy groups having 4 to 19 carbon atoms, for example, a cyclohexylmethoxy group and the like. Examples of the alkoxycarbonyloxy group include alkoxycarbonyloxy groups having 2 to 18 carbon atoms, for example, a butoxycarbonyloxy group and the like. Examples of the aromatic hydrocarbon group-carbonyloxy group include aromatic hydrocarbon group-carbonyloxy groups having 7 to 19 carbon atoms, for example, a benzoyloxy group and the like. Examples of the aromatic hydrocarbon group-carbonyl group include aromatic hydrocarbon group-carbonyl groups having 7 to 20 carbon atoms, for example, a benzoyl group and the like. Examples of the aromatic hydrocarbon group-oxy group include aromatic hydrocarbon group-oxy groups having 6 to 19 carbon atoms, for example, a phenyloxy group and the like.

Examples of the group in which —CH₂— included in the alicyclic hydrocarbon group is replaced by —O—, —CO—, —S— or —SO₂— include groups shown below. Examples of the group also include groups in which —O— is replaced by —S— or —CO— is replaced by —SO₂—, respectively, among the groups shown below. The bonding site can be any position.

Examples of the substituent which may be possessed by the hydrocarbon group as for A¹ and A² include the same groups as mentioned as for R⁴, R⁵, R⁷ and R⁸.

It is preferable that A¹ and A² are each independently a hydrocarbon group having 1 to 20 carbon atoms (the hydrocarbon group may have a substituent, and —CH₂— included in the hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO₂—, in which at least one of —CH₂— included in the hydrocarbon group is replaced by —O—, —CO—, —S— or —SO₂—). Specifically, it is more preferable that A¹ is ***-L⁰¹-X⁰¹-L⁰¹²- and A² is ***-L⁰²¹-X⁰²-L⁰²²- (X⁰¹ and X⁰² each independently represent —O—, —CO—, —S— or —SO₂—, L⁰¹¹, L⁰¹², L⁰²¹ and L⁰²² each independently represent a single bond or a hydrocarbon group having 1 to 19 carbon atoms, the hydrocarbon group may have a substituent, and —CH₂— included in the hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO₂—, in which the total number of carbon atoms of L⁰¹1 and L⁰¹² is 0 to 19, the total number of carbon atoms of L⁰²¹ and L⁰²² is 0 to 19, and *** represents a bonding site to the benzene ring to which R¹ and R² are bonded). It is still more preferable that A¹ is ***—X⁰¹-L⁰¹- or ***-L⁰¹-X⁰¹— and A² is ***—X⁰²-L⁰²- or ***-L⁰²-X⁰²—(X⁰¹ and X⁰² each independently represent —O—, —CO—, —S— or —SO₂—, L⁰¹ and L⁰² each independently represent a single bond or a hydrocarbon group having 1 to 19 carbon atoms, the hydrocarbon group may have a substituent, —CH₂— included in the hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO₂—, and *** represents a bonding site to the benzene ring to which R¹ and R² are bonded). A¹ and A² are preferably those having no substituent, except for replacement by —O—, —CO—, —S— or —SO₂—.

Examples of the hydrocarbon group having 1 to 19 carbon atoms as for L⁰¹¹, L⁰¹², L⁰²¹, L⁰²², L⁰1 and L⁰² (the hydrocarbon group may have a substituent, and —CH₂— included in the hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO₂—) include the same groups as mentioned as for A¹ and A² in the range of 1 to 19 carbon atoms.

Preferably, X⁰¹ and X⁰² are each independently —O— or —S—, and more preferably —O—.

Preferably, L⁰¹¹, L⁰¹², L⁰²¹, L⁰²², L⁰¹ and L⁰² are each independently a single bond or a hydrocarbon group having 1 to 18 carbon atoms (—CH₂— included in the hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO₂—), more preferably a single bond or a hydrocarbon group having 1 to 12 carbon atoms (—CH₂— included in the hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO₂—), still more preferably a single bond or a chain hydrocarbon group having 1 to 9 carbon atoms (—CH₂— included in the chain hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO₂—), yet more preferably a single bond or an alkanediyl group having 1 to 6 carbon atoms (—CH₂— included in the alkanediyl group may be replaced by —O— or —CO—), further preferably a single bond or an alkanediyl group having 1 to 4 carbon atoms (—CH₂— included in the alkanediyl group may be replaced by —O— or —CO—), and still further preferably a single bond or an alkanediyl group having 1 to 3 carbon atoms (—CH₂— included in the alkanediyl group may be replaced by —O— or —CO—). Of these, a single bond, a methylene group, an ethane-1,1-diyl group, a propane-1,1-diyl group, a propane-2,2-diyl group, a carbonyl group, a carbonyloxy group, a carbonyloxymethylene group, an ethyleneoxy group, a methylenecarbonyloxymethylene group or an ethyleneoxycarbonyl group is preferable, and a single bond, a methylene group or a carbonyl group is more preferable.

The bonding site of A¹ and A² to the benzene ring to which I⁺ is bonded may be each independently the o-position, the m-position or the p-position, with respect to the bonding site of I⁺, respectively. Particularly, they are each independently bonded preferably at the p-position or the m-position, with respect to the bonding site of I⁺. More specifically, when m1 and m2 are 1, A¹ and A² are each independently bonded preferably at the m-position or the p-position, and more preferably at the p-position, with respect to the bonding site of I⁺, respectively. When m1 and m2 are 2, it is preferable that one of A¹ and one of A² are each independently bonded at the o-position or the m-position and one of A¹ and one of A² are each independently bonded at the o-position or the m-position, and it is more preferable that two of A¹ and two of A² are each independently bonded at the m-position, with respect to the bonding site of I⁺, respectively. When m1 and m2 are 3, it is preferable that two of A¹ and two of A² are each independently bonded at the o-position or the m-position and one of A¹ and one of A² are each independently bonded at the p-position or the m-position, and it is more preferable that two of A¹ and two of A² are each independently bonded at the m-position and one of A¹ and one of A² are each independently bonded at the p-position, with respect to the bonding site of I⁺, respectively. When m1 and m2 are 4, it is preferable that two of A¹ and two of A² are each independently bonded at the o-position or the m-position and two of A¹ and two of A² are each independently bonded at the p-position or the m-position, and it is more preferable that two of A¹ and two of A² are each independently bonded at the o-position and two of A¹ and two of A² are each independently bonded at the m-position, with respect to the bonding site of I⁺, respectively.

m1 is preferably 1, 2, 3 or 4, more preferably 1, 2 or 3, still more preferably 1 or 2, and yet more preferably 1.

m2 is preferably 0, 1, 2, 3 or 4, more preferably 0, 1, 2 or 3, still more preferably 0, 1 or 2, and yet more preferably 0 or 1.

m4 is preferably 0, 1, 2 or 4, more preferably 0, 1 or 2, and still more preferably 0 or 1.

m5 is preferably 0, 1, 2 or 4, more preferably 0, 1 or 2, and still more preferably 0 or 1.

m7 is preferably 0, 1, 2 or 3, more preferably 0, 1 or 2, and still more preferably 0 or 1.

m8 is preferably 0, 1, 2, 3 or 4, more preferably 0, 1, 2 or 3, still more preferably 0, 1 or 2, and yet more preferably 0 or 1.

R⁴ and R⁵ each independently represent a halogen atom, a haloalkyl group having 1 to 6 carbon atoms or an alkyl group having 1 to 6 carbon atoms (—CH₂— included in the haloalkyl group and the alkyl group may be replaced by —O— or —CO—), more preferably a halogen atom, an alkyl fluoride group having 1 to 4 carbon atoms or an alkyl group having 1 to 4 carbon atoms (—CH₂— included in the alkyl group may be replaced by —O— or —CO—), still more preferably a fluorine atom, an iodine atom, a perfluoroalkyl group having 1 to 4 carbon atoms, or an alkyl group having 1 to 4 carbon atoms (—CH₂— included in the alkyl group may be replaced by —O— or —CO—), yet more preferably a fluorine atom, an iodine atom, perfluoroalkyl group having 1 to 4 carbon atoms, a hydroxy group, an alkoxy group having 1 to 3 carbon atoms or an alkyl group having 1 to 4 carbon atoms, further preferably a fluorine atom, an iodine atom, a perfluoroalkyl group having 1 to 3 carbon atoms, a hydroxy group or an alkoxy group having 1 to 3 carbon atoms, and still further preferably a fluorine atom, an iodine atom, a trifluoromethyl group, a methoxy group, an ethoxy group or a hydroxy group.

The bonding site of R⁴ and R⁵ to the benzene ring may be each independently the o-position, the m-position or the p-position, with respect to the bonding site of A¹ and A², respectively. Particularly, when m4 and m5 are 1, R⁴ and R⁵ are each independently bonded preferably at the p-position or the m-position, and more preferably at the m-position, with respect to the bonding site of A¹ and A², respectively. When m4 and m5 are 2, it is preferable that one of R⁴ and one of R⁵ are each independently bonded at the o-position or the m-position and one of R⁴ and one of R⁵ are each independently bonded at the p-position or the m-position, and it is more preferable that two of R⁴ and two of R⁵ are each independently bonded at the m-position, with respect to the bonding site of A¹ and A², respectively. When m4 and m5 are 3, it is preferable that two of R⁴ and two of R⁵ are each independently bonded at the o-position or the m-position and one of R⁴ and one of R⁵ are each independently bonded at the p-position or the m-position, and it is more preferable that one of R⁴ and one of R⁵ are each independently bonded at the o-position, and two of R⁴ and two of R⁵ are each independently bonded at the m-position, with respect to the bonding site of A¹ and A², respectively. When m4 and m5 are 4, it is preferable that two of R⁴ and two of R⁵ are each independently bonded at the o-position or the m-position and two of R⁴ and two of R⁵ are each independently bonded at the p-position or the m-position, and it is more preferable that two of R⁴ and two of R⁵ are each independently bonded at the o-position, and two of R⁴ and two of R⁵ are each independently bonded at the m-position, with respect to the bonding site of A¹ and A², respectively.

In another embodiment, at least one of one or more R⁴ and R⁵ may have an acid-labile group, R⁴ and R⁵ may be each independently the same groups as for R¹ and R², and when R¹ is —O—R¹⁰, one or two R⁴ is/are preferably —O—R¹⁰ which is the same as for R¹, and when R¹ is —O—CO—O—R¹⁰, one or two R⁴ is/are preferably —O—CO—O—R¹⁰ which is the same as for R¹, and when R¹ is —O-L¹-CO—O—R¹⁰, one or two R⁴ is/are preferably —O-L¹-CO—O—R¹⁰ which is the same as for R¹. A combination of R² and R⁵ is the same as a combination of R¹ and R⁴.

Preferably, R⁷ and R⁸ each independently represent a halogen atom, a haloalkyl group having 1 to 6 carbon atoms or an alkyl group having 1 to 6 carbon atoms (—CH₂— included in the haloalkyl group and the alkyl group may be replaced by —O— or —CO—), more preferably a halogen atom, an alkyl fluoride group having 1 to 4 carbon atoms or an alkyl group having 1 to 4 carbon atoms (—CH₂— included in the alkyl group may be replaced by —O— or —CO—), still more preferably a fluorine atom, an iodine atom, a perfluoroalkyl group having 1 to 4 carbon atoms or an alkyl group having 1 to 4 carbon atoms (—CH₂— included in the alkyl group may be replaced by —O— or —CO—), and yet more preferably a fluorine atom, an iodine atom, a trifluoromethyl group, a hydroxy group, a methoxy group, a methyl group or a t-butyl group.

The bonding site of R⁷ and R⁸ to the benzene ring may be each independently the o-position, the m-position or the p-position, with respect to the bonding site of I⁺, respectively. Particularly, when m7 and m8 are 1, R⁷ and R⁸ are each independently bonded preferably at the o-position or the p-position, with respect to the bonding site of I⁺, respectively. When m7 and m8 are 2, it is preferable that one of R⁷ and one of R⁸ are each independently bonded at the o-position or the m-position and one of R⁷ and one of R⁸ are each independently bonded at the p-position or the m-position, and it is more preferable that one of R⁷ and one of R⁸ are each independently bonded at the m-position and one of R⁷ and one of R⁸ are each independently bonded at the p-position or the m-position, with respect to the bonding site of I⁺, respectively. When m7 and m8 are 3, it is preferable that two of R⁷ and two of R⁸ are each independently bonded at the o-position or the m-position and one of R⁷ and one of R⁸ are each independently bonded at the p-position or the m-position, and it is more preferable that two of R⁷ and two of R⁸ are each independently bonded at the m-position and one of R⁷ and one of R⁸ are each independently bonded at the p-position, with respect to the bonding site of I⁺, respectively. When m7 and m8 are 4, it is preferable that two of R⁷ and two of R⁸ are each independently bonded at the o-position or the m-position and two of R⁷ and two of R⁸ are each independently bonded at the p-position or the m-position, and it is more preferable that two of R⁷ and two of R⁸ are each independently bonded at the m-position and one of R⁷ and one of R⁸ are each independently bonded at the o-position and one of R⁷ and one of R⁸ are each independently bonded at the p-position, with respect to the bonding site of I⁺, respectively.

m1 and m2 are preferably 1, or m1 and m2 are preferably 2, respectively.

In the embodiment of the case where m2=0, it is preferable that m8 is 1 and R⁸ is a branched alkyl group having 3 or 4 carbon atoms.

In the embodiment of the case where m4 is 2, it is preferable that one of two R⁴ is an iodine atom or a fluorine atom and the other one is a hydroxy group, and it is more preferable that a hydroxy group is bonded at the p-position, with respect to the bonding site of I⁺.

Examples of the cation (I) represented by formula (I-C) include a cation represented by formula (I-C-1) (hereinafter sometimes referred to as “cation (I-C-1)”):

wherein, in formula (I-C-1),

symbols R¹, R², R⁴, R⁵, R⁷, R⁸, m1, m2, m4, m5, m7, m8, L⁰¹, L⁰², X⁰¹ and X⁰² are the same as mentioned above.

The bonding site of X⁰¹ and X⁰² to the benzene ring is each independently the same bonding site of A¹ and A² to the benzene ring.

Examples of the cation (I) of the salt (I) include cations represented by the following formula (I-c-1) to formula (I-c-160).

[Anion (I)]

The anion (I) of a salt represented by formula (I) is an anion represented by formula (I-A):

wherein, in formula (I-A), all symbols are the same as defined in formula (I).

Examples of the perfluoroalkyl group represented by Q^b1 and Q^b2 include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butyl group, a perfluorotert-butyl group, a perfluoropentyl group and a perfluorohexyl group.

Examples of the alkyl group represented by Q^b1 and Q^b2 include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group and a hexyl group.

Preferably, at least one of Q1 and Q² includes a fluorine atom or a perfluoroalkyl group, more preferably each independently is a fluorine atom or a perfluoroalkyl group, still more preferably each independently is a fluorine atom or a trifluoromethyl group, and yet more preferably both of them are fluorine atoms.

Examples of the divalent saturated hydrocarbon group in L^b1 include a linear alkanediyl group, a branched alkanediyl group, a monocyclic or polycyclic divalent alicyclic saturated hydrocarbon group, or the divalent saturated hydrocarbon group may be a group formed by combining two or more of these groups.

Specific examples thereof include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diyl group, a dodecane-1,12-diyl group, a tridecane-1,13-diyl group, a tetradecane-1,14-diyl group, a pentadecane-1,15-diyl group, a hexadecane-1,16-diyl group and a heptadecane-1,17-diyl group;

branched alkanediyl groups such as an ethane-1,1-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diyl group, a pentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group;

monocyclic divalent alicyclic saturated hydrocarbon groups such as a cyclobutane-1,3-diyl group, a cyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group and a cyclooctane-1,5-diyl group; and

polycyclic divalent alicyclic saturated hydrocarbon groups such as a norbornane-1,4-diyl group, a norbornane-2,5-diyl group, an adamantane-1,5-diyl group and an adamantane-2,6-diyl group.

The group in which —CH₂— included in the divalent saturated hydrocarbon group represented by L^b1 is replaced by —O— or —CO— includes, for example, a group represented by any one of formula (b1-1) to formula (b1-3). In groups represented by formula (b1-1) to formula (b1-3) and groups represented by formula (b1-4) to formula (b1-11) which are specific examples thereof, * and ** represent a bonding site, and * represents a bonding site to —Y^b1

In formula (b1-1),

L^b2 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, and a hydrogen atom included in the saturated hydrocarbon group may be substituted with a fluorine atom,

L^b3 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, a hydrogen atom included in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and —CH₂— included in the saturated hydrocarbon group may be replaced by —O— or —CO—, and

the total number of carbon atoms of L^b2 and L^b3 is 22 or less.

In formula (b1-2),

L^b4 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, and a hydrogen atom included in the saturated hydrocarbon group may be substituted with a fluorine atom,

L^b5 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, a hydrogen atom included in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and —CH₂— included in the saturated hydrocarbon group may be replaced by —O— or —CO—, and the total number of carbon atoms of L^b4 and L^bs is 22 or less.

In formula (b1-3),

L^b6 represents a single bond or a divalent saturated hydrocarbon group having 1 to 23 carbon atoms, a hydrogen atom included in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group,

L^b7 represents a single bond or a divalent saturated hydrocarbon group having 1 to 23 carbon atoms, a hydrogen atom included in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and —CH₂— included in the saturated hydrocarbon group may be replaced by —O— or —CO—, and

the total number of carbon atoms of L^b6 and L^b7 is 23 or less.

In groups represented by formula (b1-1) to formula (b1-3), when —CH₂— included in the saturated hydrocarbon group is replaced by —O— or —CO—, the number of carbon atoms before replacement is taken as the number of carbon atoms of the saturated hydrocarbon group.

Examples of the divalent saturated hydrocarbon group include those which are the same as the divalent saturated hydrocarbon group of L^b1.

L^b2 is preferably a single bond, a methylene group, —CH(CF₃)— or —C(CF₃)₂—.

L^b3 is preferably a divalent saturated hydrocarbon group having 1 to 4 carbon atoms.

L^b4 is preferably a divalent saturated hydrocarbon group having 1 to 8 carbon atoms, a hydrogen atom included in the divalent saturated hydrocarbon group may be substituted with a fluorine atom, and more preferably a methylene group, —CH(CF₃)— or —C(CF₃)₂—.

L^b5 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.

L^b6 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 4 carbon atoms, and a hydrogen atom included in the saturated hydrocarbon group may be substituted with a fluorine atom.

L^b7 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, a hydrogen atom included in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and —CH₂— included in the divalent saturated hydrocarbon group may be replaced by —O— or —CO—.

The group in which —CH₂— included in the divalent saturated hydrocarbon group represented by L^b1 is replaced by —O— or —CO— is preferably a group represented by formula (b1-1) or formula (b1-3).

Examples of the group represented by formula (b1-1) include groups represented by formula (b1-4) to formula (b1-8).

In formula (b1-4),

L^b8 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, and a hydrogen atom included in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group.

In formula (b1-5),

L^b9 represents a divalent saturated hydrocarbon group having 1 to 20 carbon atoms, and —CH₂— included in the divalent saturated hydrocarbon group may be replaced by —O— or —CO—.

L^b10 represents a single bond or a divalent saturated hydrocarbon group having 1 to 19 carbon atoms, and a hydrogen atom included in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and the total number of carbon atoms of L^b9 and L^b10 is 20 or less.

In formula (b1-6),

L^b11 represents a divalent saturated hydrocarbon group having 1 to 21 carbon atoms,

L^b12 represents a single bond or a divalent saturated hydrocarbon group having 1 to 20 carbon atoms, and a hydrogen atom included in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and the total number of carbon atoms of L^b11 and L^b12 is 21 or less.

In formula (b1-7),

L^b13 represents a divalent saturated hydrocarbon group having 1 to 19 carbon atoms,

L^b14 represents a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and —CH₂— included in the divalent saturated hydrocarbon group may be replaced by —O— or —CO—,

L^b15 represents a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and a hydrogen atom included in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and the total number of carbon atoms of L^b13 to L^b15 is 19 or less.

In formula (b1-8),

L^b16 represents a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and —CH₂— included in the divalent saturated hydrocarbon group may be replaced by —O— or —CO—,

L^b17 represents a divalent saturated hydrocarbon group having 1 to 18 carbon atoms,

L^b18 represents a single bond or a divalent saturated hydrocarbon group having 1 to 17 carbon atoms, and a hydrogen atom included in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and the total number of carbon atoms of L^b16 to L^b18 is 19 or less.

L^b8 is preferably a divalent saturated hydrocarbon group having 1 to 4 carbon atoms.

L^b9 is preferably a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.

L^b10 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 19 carbon atoms, and more preferably a single bond or a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.

L^b11 is preferably a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.

L^b12 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.

L^b13 is preferably a divalent saturated hydrocarbon group having 1 to 12 carbon atoms.

L^b14 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 6 carbon atoms.

L^b15 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and more preferably a single bond or a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.

L^b16 is preferably a divalent saturated hydrocarbon group having 1 to 12 carbon atoms.

L^b17 is preferably a divalent saturated hydrocarbon group having 1 to 6 carbon atoms.

L^b18 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 17 carbon atoms, and more preferably a single bond or a divalent saturated hydrocarbon group having 1 to 4 carbon atoms.

Examples of the group represented by formula (b1-3) include groups represented by formula (b1-9) to formula (b1-11).

In formula (b1-9),

L^b19 represents a single bond or a divalent saturated hydrocarbon group having 1 to 23 carbon atoms, and a hydrogen atom included in the saturated hydrocarbon group may be substituted with a fluorine atom,

L^b20 represents a single bond or a divalent saturated hydrocarbon group having 1 to 23 carbon atoms, and a hydrogen atom included in the saturated hydrocarbon group may be substituted with a fluorine atom, a hydroxy group or an alkylcarbonyloxy group, —CH₂— included in the alkylcarbonyloxy group may be replaced by —O— or —CO—, and a hydrogen atom included in the alkylcarbonyloxy group may be substituted with a hydroxy group, and

the total number of carbon atoms of L^b19 and L^b20 is 23 or less.

In formula (b1-10),

L^b21 represents a single bond or a divalent saturated hydrocarbon group having 1 to 21 carbon atoms, and a hydrogen atom included in the saturated hydrocarbon group may be substituted with a fluorine atom,

L^b22 represents a single bond or a divalent saturated hydrocarbon group having 1 to 21 carbon atoms,

L^b23 represents a single bond or a divalent saturated hydrocarbon group having 1 to 21 carbon atoms, and a hydrogen atom included in the saturated hydrocarbon group may be substituted with a fluorine atom, a hydroxy group or an alkylcarbonyloxy group, —CH₂— included in the alkylcarbonyloxy group may be replaced by —O— or —CO—, and a hydrogen atom included in the alkylcarbonyloxy group may be substituted with a hydroxy group, and

the total number of carbon atoms of L^b21, L^b22 and L^b23 is 21 or less.

In formula (b1-11),

L^b24 represents a single bond or a divalent saturated hydrocarbon group having 1 to 20 carbon atoms, and a hydrogen atom included in the saturated hydrocarbon group may be substituted with a fluorine atom,

L^b23 represents a divalent saturated hydrocarbon group having 1 to 21 carbon atoms,

L^b26 represents a single bond or a divalent saturated hydrocarbon group having 1 to 20 carbon atoms, a hydrogen atom included in the saturated hydrocarbon group may be substituted with a fluorine atom, a hydroxy group or an alkylcarbonyloxy group, —CH₂— included in the alkylcarbonyloxy group may be replaced by —O— or —CO—, and a hydrogen atom included in the alkylcarbonyloxy group may be substituted with a hydroxy group, and

in which, the total number of carbon atoms of L^b24, L^b25 and L^b26 is 21 or less.

In the group represented by formula (b1-9) to the group represented by formula (b1-11), when a hydrogen atom included in the saturated hydrocarbon group is substituted with an alkylcarbonyloxy group, the number of carbon atoms before replacement is taken as the number of carbon atoms of the saturated hydrocarbon group.

Examples of the alkylcarbonyloxy group include an acetyloxy group, a propionyloxy group, a butyryloxy group, a cyclohexylcarbonyloxy group, an adamantylcarbonyloxy group and the like.

Examples of the group represented by formula (b1-4) include the followings.

Examples of the group represented by formula (b1-5) include the followings.

Examples of the group represented by formula (b1-6) include the followings.

Examples of the group represented by formula (b1-7) include the followings.

Examples of the group represented by formula (b1-8) include the followings.

Examples of the group represented by formula (b1-2) include the followings.

Examples of the group represented by formula (b1-9) include the followings.

Examples of the group represented by formula (b1-10) include the followings.

Examples of the group represented by formula (b1-11) include the followings.

Examples of the alicyclic hydrocarbon group in which —CH₂— included in the alicyclic hydrocarbon group represented by Y^b1 is not replaced by —O—, —S—, —SO₂— or —CO— include groups represented by formula (Y1) to formula (Y11) and formula (Y36) to formula (Y38).

When —CH₂— included in the alicyclic hydrocarbon group represented by Y^b1 is replaced by —O—, —S—, —SO₂— or —CO—, the number may be 1, or 2 or more. Examples of such group include groups represented by formula (Y12) to formula (Y35) and formula (Y39) to formula (Y43). —O— or —CO— of the groups represented by formula (Y12) to formula (Y35) and formula (Y39) to formula (Y43) may be replaced by —S— or —SO₂—. The bonding site can be any position.

The alicyclic hydrocarbon group represented by Y^b1 is preferably a group represented by any one of formula (Y1) to formula (Y20), formula (Y26), formula (Y27), formula (Y30), formula (Y31) and formula (Y39) to formula (Y43), more preferably a group represented by formula (Y11), formula (Y15), formula (Y16), formula (Y20), formula (Y26), formula (Y27), formula (Y30), formula (Y31), formula (Y39), formula (Y40), formula (Y42) or formula (Y43), and still more preferably a group represented by formula (Y11), formula (Y15), formula (Y20), formula (Y26), formula (Y27), formula (Y30), formula (Y31), formula (Y39), formula (Y40), formula (Y42) or formula (Y43).

Examples of the substituent of the alicyclic hydrocarbon group represented by Y^b1 include a halogen atom, a hydroxy group, a cyano group, an alkyl group having 1 to 16 carbon atoms which may be substituted with a hydroxy group (—CH₂— included in the alkyl group may be replaced by —O— or —CO—), an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, an aralkyl group having 7 to 21 carbon atoms, a glycidyloxy group, a —(CH₂)_{j a}—CO—O—R^b1 group or a —(CH₂)_{j a}—O—CO—R^b1 group (wherein R^b1 represents an alkyl group having 1 to 16 carbon atoms, an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group obtained by combining these groups, —CH₂— included in the alkyl group and the alicyclic hydrocarbon group may be replaced by —O—, —SO₂— or —CO—, and a hydrogen atom included in the alkyl group, the alicyclic hydrocarbon group and the aromatic hydrocarbon group may be substituted with a hydroxy group or a fluorine atom, and ja represents an integer of 0 to 4).

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

Examples of the alicyclic hydrocarbon group include a cyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, a dimethylcyclohexyl group, a cycloheptyl group, a cyclooctyl group, a norbornyl group, an adamantyl group and the like. The alicyclic hydrocarbon group may have a chain hydrocarbon group, and examples thereof include a methylcyclohexyl group, a dimethylcyclohexyl group and the like. The number of carbon atoms of the alicyclic hydrocarbon group is preferably 3 to 12, and more preferably 3 to 10.

Examples of the aromatic hydrocarbon group include aryl groups such as a phenyl group, a naphthyl group, an anthryl group, a biphenyl group and a phenanthryl group. The aromatic hydrocarbon group may have a chain hydrocarbon group or an alicyclic hydrocarbon group, and preferred are aromatic hydrocarbon groups which have a chain hydrocarbon group having 1 to 18 carbon atoms (a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a p-methylphenyl group, a p-ethylphenyl group, a p-tert-butylphenyl group, a 2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group, etc.) and aromatic hydrocarbon groups which have an alicyclic hydrocarbon group having 3 to 18 carbon atoms (a p-adamantylphenyl group, a p-cyclohexylphenyl group, etc.). The number of carbon atoms of the aromatic hydrocarbon group is preferably 6 to 14, and more preferably 6 to 10.

Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group and the like. The number of carbon atoms of the alkyl group is preferably 1 to 12, more preferably 1 to 6, and still more preferably 1 to 4.

Examples of the alkyl group substituted with a hydroxy group include hydroxyalkyl groups such as a hydroxymethyl group and a hydroxyethyl group.

Examples of the aralkyl group include a benzyl group, a phenethyl group, a phenylpropyl group, a naphthylmethyl group and a naphthylethyl group.

Examples of the group in which —CH₂— included in the alkyl group is replaced by —O—, —SO₂— or —CO— include an alkoxy group, an alkylsulfonyl group, an alkoxycarbonyl group, an alkylcarbonyl group, an alkylcarbonyloxy group, or a group obtained by combining these groups.

Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, an octyloxy group, a decyloxy group and a dodecyloxy group. The number of carbon atoms of the alkoxy group is preferably 1 to 12, more preferably 1 to 6, and still more preferably 1 to 4.

Examples of the alkylsulfonyl group include a methylsulfonyl group, an ethylsulfonyl group, a propylsulfonyl group and the like. The number of carbon atoms of the alkylsulfonyl group is preferably 1 to 12, more preferably 1 to 6, and still more preferably 1 to 4.

Examples of the alkoxycarbonyl group include a methoxycarbonyl group, an ethoxycarbonyl group, a butoxycarbonyl group and the like. The number of carbon atoms of the alkoxycarbonyl group is preferably 2 to 12, more preferably 2 to 6, and still more preferably 2 to 4.

Examples of the alkylcarbonyl group include an acetyl group, a propionyl group and a butyryl group. The number of carbon atoms of the alkylcarbonyl group is preferably 2 to 12, more preferably 2 to 6, and still more preferably 2 to 4.

Examples of the alkylcarbonyloxy group include an acetyloxy group, a propionyloxy group, a butyryloxy group and the like. The number of carbon atoms of the alkylcarbonyloxy group is preferably 2 to 12, more preferably 2 to 6, and still more preferably 2 to 4.

Examples of the combined group include a group obtained by combining an alkoxy group with an alkyl group, a group obtained by combining an alkoxy group with an alkoxy group, a group obtained by combining an alkoxy group with an alkylcarbonyl group, a group obtained by combining an alkoxy group with an alkylcarbonyloxy group and the like.

Examples of the group obtained by combining an alkoxy group with an alkyl group include alkoxyalkyl groups such as a methoxymethyl group, a methoxyethyl group, an ethoxyethyl group, an ethoxymethyl group and the like. The number of carbon atoms of the alkoxyalkyl group is preferably 2 to 12, more preferably 2 to 6, and still more preferably 2 to 4.

Examples of the group obtained by combining an alkoxy group with an alkoxy group include alkoxyalkoxy groups such as a methoxymethoxy group, a methoxyethoxy group, an ethoxymethoxy group, an ethoxyethoxy group and the like. The number of carbon atoms of the alkoxyalkoxy group is preferably 2 to 12, more preferably 2 to 6, and still more preferably 2 to 4.

Examples of the group obtained by combining an alkoxy group with an alkylcarbonyl group include alkoxyalkylcarbonyl groups such as a methoxyacetyl group, a methoxypropionyl group, an ethoxyacetyl group, an ethoxypropionyl group and the like. The number of carbon atoms of the alkoxyalkylcarbonyl group is preferably 3 to 13, more preferably 3 to 7, and still more preferably 3 to 5.

Examples of the group obtained by combining an alkoxy group with an alkylcarbonyloxy group include alkoxyalkylcarbonyloxy groups such as a methoxyacetyloxy group, a methoxypropionyloxy group, an ethoxyacetyloxy group, an ethoxypropionyloxy group and the like. The number of carbon atoms of the alkoxyalkylcarbonyloxy group is preferably 3 to 13, more preferably 3 to 7, and still more preferably 3 to 5.

Examples of the group in which —CH₂— included in the alicyclic hydrocarbon group is replaced by —O—, —SO₂— or —CO— include groups represented by formula (Y12) to formula (Y35) and formula (Y39) to formula (Y43).

Particularly, the alicyclic hydrocarbon group in Y^b1 (—CH₂— included in the alicyclic hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO₂—) is preferably an alicyclic hydrocarbon group having 3 to 18 carbon atoms (—CH₂— included in the alicyclic hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO₂—), more preferably a group represented by any one of formula (w1-1) to formula (w1-24), still more preferably a group represented by any one of formula (w1-1) to formula (w1-6) and formula (w1-12) to formula (w1-24), and yet more preferably a group represented by any one of formula (w1-1) to formula (w1-3), formula (w1-15) and formula (w1-22):

wherein, in formula (w1-1) to formula (w1-24),

—CH₂— included in the group may be replaced by —O—, —S—, —CO— or —SO₂—. The bonding site is any position.

Y^b1 is preferably a single bond or an alicyclic hydrocarbon group having 3 to 24 carbon atoms which may have a substituent, more preferably a single bond or an alicyclic hydrocarbon group having 3 to 20 carbon atoms which may have a substituent, still more preferably a single bond or an alicyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent, and yet more preferably a cyclohexanediyl group which may have a substituent, an adamantanediyl group which may have a substituent, a norbornanediyl group which may have a substituent, an adamantanelactonediyl group which may have a substituent or a norbornanelactonediyl group which may have a substituent, and —CH₂— constituting the alicyclic hydrocarbon group, the cyclohxanediyl group, the adamantanediyl group or the norbornanediyl group may be replaced by —O—, —S—, —CO— or —SO₂—.

The substituent which may be possessed by Y^b1 is preferably a hydroxy group, a halogen atom, a cyano group, an alkyl group having 1 to 12 carbon atoms which may be substituted with a hydroxy group (—CH₂— included in the alkyl group may be replaced by —O— or —CO—) or an alicyclic hydrocarbon group having 3 to 12 carbon atoms, and more preferably a hydroxy group, a halogen atom, a cyano group, an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms. Examples of the halogen atom, the alkyl group, the alkoxy group and the alicyclic hydrocarbon group include the same groups as mentioned above. Of these, a fluorine atom, a hydroxy group, a methyl group or an ethyl group is preferable.

Examples of the halogen atom as for R^bb1 include the same halogen atoms as mentioned as for R⁴, R⁵, R⁷ and R⁸. Examples of the alkyl group which may have a halogen atom as for R^bb1 include the same alkyl groups and haloalkyl groups as mentioned as for R⁴, R⁵, R⁷ and R⁸ as long as the upper limit of the number of carbon atoms permits.

R^bb1 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, still more preferably a hydrogen atom or a methyl group, and yet more preferably a methyl group.

When X¹⁰ is a group represented by *-Ax-Ph-Ay-**, it is preferably a linking group represented by the following formula (X¹⁰).

In formula (X¹⁰), Ax represents bond species bonded to carbon atoms to which R^bb1 is bonded, and represents one bond species selected from the group consisting of a single bond, an ether bond, a thioether bond, an ester bond and a carbonic acid ester bond.

Ay represents bond species to which L¹⁰ is bonded, and represents one bond species selected from the group consisting of a single bond, an ether bond, a thioether bond, an ester bond and a carbonic acid ester bond.

When either Ax or Ay is a single bond, the other is preferably one selected from the group consisting of an ether bond, a thioether bond, an ester bond and a carbonic acid ester bond.

Rx represents a halogen atom, a hydroxy group, an alkyl fluoride group having 1 to 6 carbon atoms, an alkyl group having 1 to 18 carbon atoms or an alkoxy group having 1 to 6 carbon atoms. Of these, a fluorine atom, an iodine atom, a trifluoromethyl group, a methyl group or an ethyl group is preferable.

mx represents an integer of 0 to 4, and preferably 0, 1 or 2. When mx is an integer of 2 or more, a plurality of Rx may be the same or different from each other.

The bonding site of Ay in the phenylene group is preferably the m-position or the p-position, and more preferably the p-position, with respect to a bonding site of Ax.

Examples of X¹⁰ include groups represented by the following formula (X¹⁰-1) to formula (X¹⁰-10). * and ** represent bonding sites, and * represents a bonding site to carbon atoms to which —R^bb1 is bonded.

Specific examples of the groups represented by formula (X¹⁰-3) to formula (X¹⁰-10) include groups represented by the following formulas.

Particularly, X¹⁰ is preferably a single bond or a group represented by any one of formula (X¹⁰-1) and formula (X¹⁰-3′) to formula (X¹⁰-10′), more preferably a single bond or a group represented by any one of formula (X¹⁰-1), formula (X¹⁰-4′), formula (X¹⁰-5′), formula (X¹⁰-6′) and formula (X¹⁰-10′), and still more preferably a single bond, a group represented by formula (X¹⁰-1), a group represented by formula (X¹⁰-5′) or a group represented by formula (X¹⁰-6′).

The hydrocarbon group having 1 to 36 carbon atoms as for L¹⁰ includes divalent aliphatic hydrocarbon groups (divalent chain hydrocarbon groups and divalent alicyclic hydrocarbon groups, such as an alkanediyl group, an alkenediyl group and an alkynedyl group), divalent aromatic hydrocarbon groups and the like, and may be divalent hydrocarbon groups obtained by combining two or more of these groups.

Examples of the alkanediyl group include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diyl group and a dodecane-1,12-diyl group; and

branched alkanediyl groups such as an ethane-1,1-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diyl group, a pentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group.

Examples of the alkenediyl group include an ethenediyl group, a propenediyl group, an isopropenediyl group, a butenediyl group, an isobutenediyl group, a tert-butenediyl group, a pentenediyl group, a hexenediyl group, a heptenediyl group, an octenediyl group, an isooctenediyl group and a nonenediyl group.

Examples of the alkynedyl group include an ethynediyl group, a propynediyl group, an isopropynediyl group, a butynediyl group, an isobutynediyl group, a tert-butynediyl group, a pentynediyl group, a hexynediyl group, an octynediyl group, a nonynediyl group and the like.

The number of carbon atoms of the chain hydrocarbon group is preferably 1 to 12, more preferably 1 to 9, still more preferably 1 to 6, yet more preferably 1 to 4, and further preferably 1 to 3.

The divalent alicyclic hydrocarbon group may be monocyclic, polycyclic or spiro ring. Examples of the divalent alicyclic hydrocarbon group include groups shown below. The bonding site can be any position.

Specifically, examples of the monocyclic divalent alicyclic hydrocarbon group include monocyclic cycloalkanediyl groups such as a cyclobutane-1,3-diyl group, a cyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group, a cyclohexene-3,6-diyl group and a cyclooctane-1,5-diyl group; and examples of the polycyclic divalent alicyclic hydrocarbon group include polycyclic cycloalkanediyl groups such as a norbornane-1,4-diyl group, a norbornane-2,5-diyl group, a 5-norbornene-2,3-diyl group, an adamantane-1,5-diyl group and an adamantane-2,6-diyl group.

The number of carbon atoms of the alicyclic hydrocarbon group is preferably 3 to 18, more preferably 3 to 16, and still more preferably 3 to 12.

Examples of the divalent aromatic hydrocarbon group include a phenylene group, a naphthylene group, an anthrylene group, a biphenylene group, a phenanthrylene group and the like. The number of carbon atoms of the aromatic hydrocarbon group is preferably 6 to 18, more preferably 6 to 14, and still more preferably 6 to 10.

Examples of the hydrocarbon group obtained by combining two or more groups include groups obtained by combining an alkanediyl group, an alicyclic hydrocarbon group and/or an aromatic hydrocarbon group, and examples thereof include an -alicyclic hydrocarbon group-alkanediyl group-, an -alkanediyl group-alicyclic hydrocarbon group-, an -alkanediyl group-alicyclic hydrocarbon group-alkanediyl group-, an -alkanediyl group-aromatic hydrocarbon group-, an -aromatic hydrocarbon group-alkanediyl group- and the like.

—CH₂— included in the hydrocarbon group having 1 to 36 carbon atoms as for L¹⁰ may be replaced by —O—, —S—, —CO— or —SO₂—.

When the hydrocarbon group having 1 to 36 carbon atoms as for L¹⁰ has a substituent, or when —CH₂— included in the hydrocarbon group is replaced by —O—, —S—, —CO— or —SO₂—, the number of carbon atoms before replacement is taken as the number of carbon atoms of the hydrocarbon group.

Examples of the group in which —CH₂— included in the hydrocarbon group is replaced by —O—, —S—, —SO₂— or —CO— include a hydroxy group (a group in which —CH₂— included in the methyl group is replaced by —O—), a carboxy group (a group in which —CH₂—CH₂— included in the ethyl group is replaced by —O—CO—), a thiol group (a group in which —CH₂— included in the methyl group is replaced by —S—), an alkoxy group (a group in which —CH₂— at any position included in the alkyl group is replaced by —O—), an alkoxycarbonyl group (a group in which —CH₂—CH₂— at any position included in the alkyl group is replaced by —O—CO—), an alkylcarbonyl group (a group in which —CH₂— at any position included in the alkyl group is replaced by —CO—), an alkylcarbonyloxy group (a group in which —CH₂—CH₂— at any position included in the alkyl group is replaced by —CO—O—), an oxy group (a group in which —CH₂— included in the methylene group is replaced by —O—), a carbonyl group (a group in which —CH₂— included in the methylene group is replaced by —CO—), a thio group (a group in which —CH₂— included in the methylene group is replaced by —S—), a sulfonyl group (a group in which —CH₂— included in the methylene group is replaced by —SO₂—), an alkanediyloxy group (a group in which —CH₂— at any position included in the alkanediyl group is replaced by —O—), an alkanediyloxycarbonyl group (a group in which —CH₂—CH₂— at any position included in the alkanediyl group is replaced by —O—CO—), an alkanediylcarbonyl group (a group in which —CH₂— at any position included in the alkanediyl group is replaced by —CO—), an alkanediylcarbonyloxy group (a group in which —CH₂—CH₂— at any position included in the alkanediyl group is replaced by —CO—O—), an alkylthio group (a group in which —CH₂— at any position included in the alkyl group is replaced by —S—), an alkylsulfonyl group (a group in which —CH₂— at any position included in the alkyl group is replaced by —SO₂—), an alkanediylthio group (a group in which —CH₂— at any position included in the alkanediyl group is replaced by —S—), an alkanediylsulfonyl group (a group in which-CH₂— at any position included in the alkanediyl group is replaced by —SO₂—), a cycloalkoxy group, a cycloalkylalkoxy group, an alkoxycarbonyloxy group, an aromatic hydrocarbon group-carbonyloxy group, an aromatic hydrocarbon group-carbonyl group, aromatic hydrocarbon group-oxy group, a group obtained by combining two or more of these groups and the like.

Examples of the alkoxy group include alkoxy groups having 1 to 17 carbon atoms, for example, a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, an octyloxy group, a 2-ethylhexyloxy group, a nonyloxy group, a decyloxy group, an undecyloxy group and the like. The number of carbon atoms of the alkoxy group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3. The alkoxycarbonyl group, the alkylcarbonyl group and the alkylcarbonyloxy group represent a group in which a carbonyl group or a carbonyloxy group is bonded to the above-mentioned alkyl group or alkoxy group.

Examples of the alkoxycarbonyl group include alkoxycarbonyl groups having 2 to 17 carbon atoms, for example, a methoxycarbonyl group, an ethoxycarbonyl group, a butoxycarbonyl group and the like. Examples of the alkylcarbonyl group include alkylcarbonyl groups having 2 to 18 carbon atoms, for example, an acetyl group, a propionyl group and a butyryl group. Examples of the alkylcarbonyloxy group include alkylcarbonyloxy groups having 2 to 17 carbon atoms, for example, an acetyloxy group, a propionyloxy group, a butyryloxy group and the like. The number of carbon atoms of the alkoxycarbonyl group, the alkylcarbonyl group and the alkylcarbonyloxy group is preferably 2 to 11, more preferably 2 to 6, still more preferably 2 to 4, and yet more preferably 2 to 3.

Examples of the alkanediyloxy group include alkanediyloxy groups having 1 to 17 carbon atoms, for example, a methyleneoxy group, an ethyleneoxy group, a propanediyloxy group, a butanediyloxy group, a pentanediyloxy group and the like. The number of carbon atoms of the alkanediyloxy group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

Examples of the alkanediyloxycarbonyl group include alkanediyloxycarbonyl groups having 2 to 17 carbon atoms, for example, a methyleneoxycarbonyl group, an ethyleneoxycarbonyl group, a propanediyloxycarbonyl group, a butanediyloxycarbonyl group and the like. Examples of the alkanediylcarbonyl group include alkanediylcarbonyl groups having 2 to 18 carbon atoms, for example, a methylenecarbonyl group, an ethylenecarbonyl group, a propanediylcarbonyl group, a butanediylcarbonyl group, a pentanediylcarbonyl group and the like. Examples of the alkanediylcarbonyloxy group include alkanediylcarbonyloxy groups having 2 to 17 carbon atoms, for example, a methylenecarbonyloxy group, an ethylenecarbonyloxy group, a propanediylcarbonyloxy group, a butanediylcarbonyloxy group and the like. The number of carbon atoms of the alkanediyloxycarbonyl group, the alkanediylcarbonyl group and the alkanediylcarbonyloxy group is preferably 2 to 11, more preferably 2 to 6, still more preferably 2 to 4, and yet more preferably 2 to 3.

Examples of the alkylthio group include alkylthio groups having 1 to 17 carbon atoms, for example, a methylthio group, an ethylthio group, a propylthio group and the like. The number of carbon atoms of the alkylthio group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

Examples of the alkylsulfonyl group include alkylsulfonyl groups having 1 to 17 carbon atoms, for example, a methylsulfonyl group, an ethylsulfonyl group, a propylsulfonyl group and the like. The number of carbon atoms of the alkylsulfonyl group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

Examples of the alkanediylthio group include alkanediylthio groups having 1 to 17 carbon atoms, for example, a methylenethio group, an ethylenethio group, a propylenethio group and the like. The number of carbon atoms of the alkanediylthio group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

Examples of the alkanediylsulfonyl group include alkanediylsulfonyl groups having 1 to 17 carbon atoms, for example, a methylenesulfonyl group, an ethylenesulfonyl group, a propylenesulfonyl group and the like. The number of carbon atoms of the alkanediylsulfonyl group is preferably 1 to 11, more preferably 1 to 6, still more preferably 1 to 4, and yet more preferably 1 to 3.

Examples of the cycloalkoxy group include cycloalkoxy groups having 3 to 17 carbon atoms, for example, a cyclohexyloxy group and the like. Examples of the cycloalkylalkoxy group include cycloalkylalkoxy groups having 4 to 17 carbon atoms, for example, a cyclohexylmethoxy group and the like. Examples of the alkoxycarbonyloxy group include alkoxycarbonyloxy group having 2 to 16 carbon atoms, for example, a butoxycarbonyloxy group and the like. The number of carbon atoms of the cycloalkoxy group and the cycloalkylalkoxy group is preferably 3 to 11, and more preferably 3 to 6. The number of carbon atoms of the alkoxycarbonyloxy group is preferably 2 to 11, more preferably 2 to 6, still more preferably 2 to 4, and yet more preferably 2 to 3. Examples of the aromatic hydrocarbon group-carbonyloxy group include aromatic hydrocarbon group-carbonyloxy groups having 7 to 17 carbon atoms, for example, a benzoyloxy group and the like. Examples of the aromatic hydrocarbon group-carbonyl group include aromatic hydrocarbon group-carbonyl groups having 7 to 18 carbon atoms, for example, a benzoyl group and the like. Examples of the aromatic hydrocarbon group-oxy group include aromatic hydrocarbon group-oxy groups having 6 to 17 carbon atoms, for example, a phenyloxy group and the like.

Examples of the group in which —CH₂— included in the alicyclic hydrocarbon group is replaced by —O—, —S—, —CO— or —SO₂— include the following groups. —O— or —CO— of the following groups may be replaced by —S— or —SO₂—. The bonding site can be any position.

Examples of the substituent which may be possessed by the hydrocarbon group as for L¹⁰ include a halogen atom, a cyano group and the like.

By the group in which —CH₂— included in the hydrocarbon group as for L¹⁰ is replaced by —O— or —CO—, L¹⁰ can substantially have substituents such as a hydroxy group, a carboxy group, an alkoxy group, an alkoxycarbonyl group, an alkylcarbonyl group and an alkylcarbonyloxy group.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

The hydrocarbon group having 1 to 36 carbon atoms as for L¹⁰ may have one substituent or a plurality of substituents.

L¹⁰ is preferably a single bond, an alkanediyl group having 1 to 6 carbon atoms (in which —CH₂— included in the alkanediyl group may be replaced by —O— or —CO—), a cyclic hydrocarbon group having 3 to 18 carbon atoms (in which the cyclic hydrocarbon group may have a substituent, and —CH₂— included in the cyclic hydrocarbon group may be replaced by —O—, —S—, —SO₂— or —CO—) or a group obtained by combining an alkanediyl group having 1 to 6 carbon atoms with a cyclic hydrocarbon group having 3 to 18 carbon atoms (in which the cyclic hydrocarbon group may have a substituent, —CH₂— included in the alkanediyl group may be replaced by —O— or —CO—, and —CH₂— included in the cyclic hydrocarbon group may be replaced by —O—, —S—, —SO₂— or —CO—), more preferably a single bond, an alkanediyl group having 1 to 4 carbon atoms (in which —CH₂— included in the alkanediyl group may be replaced by —O— or —CO—), an alicyclic hydrocarbon group having 3 to 18 carbon atoms (in which —CH₂— included in the alicyclic hydrocarbon group may be replaced by —O—, —S—, —SO₂— or —CO—), an aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent, a group obtained by combining an alkanediyl group having 1 to 4 carbon atoms with an alicyclic hydrocarbon group having 3 to 18 carbon atoms (in which —CH₂— included in the alkanediyl group may be replaced by —O— or —CO—, and —CH₂— included in the alicyclic hydrocarbon group may be replaced by —O—, —S—, —SO₂— or —CO—) or a group obtained by combining an alkanediyl group having 1 to 4 carbon atoms with an aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent (—CH₂— included in the alkanediyl group may be replaced by —O— or —CO—), still more preferably a single bond, an alkanediyl group having 1 to 4 carbon atoms (in which —CH₂— included in the alkanediyl group may be replaced by —O— or —CO—), an alicyclic hydrocarbon group having 3 to 18 carbon atoms (in which —CH₂— included in the alicyclic hydrocarbon group may be replaced by —O— or —CO—), a phenylene group which may have a substituent, a group obtained by combining an alkanediyl group having 1 to 4 carbon atoms with an alicyclic hydrocarbon group having 3 to 18 carbon atoms (in which —CH₂— included in the alkanediyl group may be replaced by —O— or —CO—, and —CH₂— included in the alicyclic hydrocarbon group may be replaced by —O— or —CO—) or a group obtained by combining an alkanediyl group having 1 to 4 carbon atoms with a phenylene group which may have a substituent (in which —CH₂— included in the alkanediyl group may be replaced by —O— or —CO—), and yet more preferably a single bond or alkanediyl group having 1 to 4 carbon atoms (in which —CH₂— included in the alkanediyl group may be replaced by —O— or —CO—).

Examples of the anion (I) include the following anions.

It is also possible to exemplify, as specific examples of the anion (I), an anion in which the methyl group corresponding to R^bb1 of formula (I) is substituted with a hydrogen atom, in anions represented by formula (I-a-1) to formula (I-a-14). Of these, anions represented by formula (I-a-1) to formula (I-a-6) are preferable.

Specific examples of the salt (I) include salts obtained by optionally combining the above-mentioned cations and anions. Specific examples of the salt (I) are shown in the following table.

In the following table, the respective symbols represent symbols imparted to structures showing the above-mentioned anions and cations, and “to” represents that the salt (I) and the anion (I) correspond, respectively. For example, the salt (I-1) is a salt composed of an anion represented by formula (I-a-1) and a cation represented by formula (I-c-1), and is a salt shown below. The salt (I-2) is a salt composed of an anion represented by formula (I-a-2) and a cation represented by formula (I-c-1), and the salt (I-15) is a salt composed of an anion represented by formula (I-a-1) and a cation represented by formula (I-c-2)

TABLE 1
Salt (I)	Anion (I)	Cation (I)
(I-1) to (I-14)	(I-a-1) to (I-a-14)	(I-c-1)
(I-15) to (I-28)	(I-a-1) to (I-a-14)	(I-c-2)
(I-29) to (I-42)	(I-a-1) to (I-a-14)	(I-c-3)
(I-43) to (I-56)	(I-a-1) to (I-a-14)	(I-c-4)
(I-57) to (I-70)	(I-a-1) to (I-a-14)	(I-c-5)
(I-71) to (I-84)	(I-a-1) to (I-a-14)	(I-c-6)
(I-85) to (I-98)	(I-a-1) to (I-a-14)	(I-c-7)
(I-99) to (I-112)	(I-a-1) to (I-a-14)	(I-c-8)
(I-113) to (I-126)	(I-a-1) to (I-a-14)	(I-c-9)
(I-127) to (I-140)	(I-a-1) to (I-a-14)	(I-c-10)
(I-141) to (I-154)	(I-a-1) to (I-a-14)	(I-c-11)
(I-155) to (I-168)	(I-a-1) to (I-a-14)	(I-c-12)
(I-169) to (I-182)	(I-a-1) to (I-a-14)	(I-c-13)
(I-183) to (I-196)	(I-a-1) to (I-a-14)	(I-c-14)
(I-197) to (I-210)	(I-a-1) to (I-a-14)	(I-c-15)
(I-211) to (I-224)	(I-a-1) to (I-a-14)	(I-c-16)
(I-225) to (I-238)	(I-a-1) to (I-a-14)	(I-c-17)
(I-239) to (I-252)	(I-a-1) to (I-a-14)	(I-c-18)
(I-253) to (I-266)	(I-a-1) to (I-a-14)	(I-c-19)
(I-267) to (I-280)	(I-a-1) to (I-a-14)	(I-c-20)
(I-281) to (I-294)	(I-a-1) to (I-a-14)	(I-c-21)
(I-295) to (I-308)	(I-a-1) to (I-a-14)	(I-c-22)
(I-309) to (I-322)	(I-a-1) to (I-a-14)	(I-c-23)
(I-323) to (I-336)	(I-a-1) to (I-a-14)	(I-c-24)
(I-337) to (I-350)	(I-a-1) to (I-a-14)	(I-c-25)
(I-351) to (I-364)	(I-a-1) to (I-a-14)	(I-c-26)
(I-365) to (I-378)	(I-a-1) to (I-a-14)	(I-c-27)
(I-379) to (I-392)	(I-a-1) to (I-a-14)	(I-c-28)
(I-393) to (I-406)	(I-a-1) to (I-a-14)	(I-c-29)
(I-407) to (I-420)	(I-a-1) to (I-a-14)	(I-c-30)
(I-421) to (I-434)	(I-a-1) to (I-a-14)	(I-c-31)
(I-435) to (I-448)	(I-a-1) to (I-a-14)	(I-c-32)
(I-449) to (I-462)	(I-a-1) to (I-a-14)	(I-c-33)
(I-463) to (I-476)	(I-a-1) to (I-a-14)	(I-c-34)
(I-477) to (I-490)	(I-a-1) to (I-a-14)	(I-c-35)
(I-491) to (I-504)	(I-a-1) to (I-a-14)	(I-c-36)
(I-505) to (I-518)	(I-a-1) to (I-a-14)	(I-c-37)
(I-519) to (I-532)	(I-a-1) to (I-a-14)	(I-c-38)
(I-533) to (I-546)	(I-a-1) to (I-a-14)	(I-c-39)
(I-547) to (I-560)	(I-a-1) to (I-a-14)	(I-c-40)
(I-561) to (I-574)	(I-a-1) to (I-a-14)	(I-c-41)
(I-575) to (I-588)	(I-a-1) to (I-a-14)	(I-c-42)
(I-589) to (I-602)	(I-a-1) to (I-a-14)	(I-c-43)
(I-603) to (I-616)	(I-a-1) to (I-a-14)	(I-c-44)
(I-617) to (I-630)	(I-a-1) to (I-a-14)	(I-c-45)
(I-631) to (I-644)	(I-a-1) to (I-a-14)	(I-c-46)
(I-645) to (I-658)	(I-a-1) to (I-a-14)	(I-c-47)
(I-659) to (I-672)	(I-a-1) to (I-a-14)	(I-c-48)
(I-673) to (I-686)	(I-a-1) to (I-a-14)	(I-c-49)
(I-687) to (I-700)	(I-a-1) to (I-a-14)	(I-c-50)
(I-701) to (I-714)	(I-a-1) to (I-a-14)	(I-c-51)
(I-715) to (I-728)	(I-a-1) to (I-a-14)	(I-c-52)
(I-729) to (I-742)	(I-a-1) to (I-a-14)	(I-c-53)
(I-743) to (I-756)	(I-a-1) to (I-a-14)	(I-c-54)
(I-757) to (I-770)	(I-a-1) to (I-a-14)	(I-c-55)
(I-771) to (I-784)	(I-a-1) to (I-a-14)	(I-c-56)
(I-785) to (I-798)	(I-a-1) to (I-a-14)	(I-c-57)
(I-799) to (I-812)	(I-a-1) to (I-a-14)	(I-c-58)
(I-813) to (I-826)	(I-a-1) to (I-a-14)	(I-c-59)
(I-827) to (I-840)	(I-a-1) to (I-a-14)	(I-c-60)
(I-841) to (I-854)	(I-a-1) to (I-a-14)	(I-c-61)
(I-855) to (I-868)	(I-a-1) to (I-a-14)	(I-c-62)
(I-869) to (I-882)	(I-a-1) to (I-a-14)	(I-c-63)
(I-883) to (I-896)	(I-a-1) to (I-a-14)	(I-c-64)
(I-897) to (I-910)	(I-a-1) to (I-a-14)	(I-c-65)
(I-911) to (I-924)	(I-a-1) to (I-a-14)	(I-c-66)
(I-925) to (I-938)	(I-a-1) to (I-a-14)	(I-c-67)
(I-939) to (I-952)	(I-a-1) to (I-a-14)	(I-c-68)
(I-953) to (I-966)	(I-a-1) to (I-a-14)	(I-c-69)
(I-967) to (I-980)	(I-a-1) to (I-a-14)	(I-c-70)
(I-981) to (I-994)	(I-a-1) to (I-a-14)	(I-c-71)
(I-995) to (I-1008)	(I-a-1) to (I-a-14)	(I-c-72)
(I-1009) to (I-1022)	(I-a-1) to (I-a-14)	(I-c-73)
(I-1023) to (I-1036)	(I-a-1) to (I-a-14)	(I-c-74)
(I-1037) to (I-1050)	(I-a-1) to (I-a-14)	(I-c-75)
(I-1051) to (I-1064)	(I-a-1) to (I-a-14)	(I-c-76)
(I-1065) to (I-1078)	(I-a-1) to (I-a-14)	(I-c-77)
(I-1079) to (I-1092)	(I-a-1) to (I-a-14)	(I-c-78)
(I-1093) to (I-1106)	(I-a-1) to (I-a-14)	(I-c-79)
(I-1107) to (I-1120)	(I-a-1) to (I-a-14)	(I-c-80)
(I-1121) to (I-1134)	(I-a-1) to (I-a-14)	(I-c-81)
(I-1135) to (I-1148)	(I-a-1) to (I-a-14)	(I-c-82)
(I-1149) to (I-1162)	(I-a-1) to (I-a-14)	(I-c-83)
(I-1163) to (I-1176)	(I-a-1) to (I-a-14)	(I-c-84)
(I-1177) to (I-1190)	(I-a-1) to (I-a-14)	(I-c-85)
(I-1191) to (I-1204)	(I-a-1) to (I-a-14)	(I-c-86)
(I-1205) to (I-1218)	(I-a-1) to (I-a-14)	(I-c-87)
(I-1219) to (I-1232)	(I-a-1) to (I-a-14)	(I-c-88)
(I-1233) to (I-1246)	(I-a-1) to (I-a-14)	(I-c-89)
(I-1247) to (I-1260)	(I-a-1) to (I-a-14)	(I-c-90)
(I-1261) to (I-1274)	(I-a-1) to (I-a-14)	(I-c-91)
(I-1275) to (I-1288)	(I-a-1) to (I-a-14)	(I-c-92)
(I-1289) to (I-1302)	(I-a-1) to (I-a-14)	(I-c-93)
(I-1303) to (I-1316)	(I-a-1) to (I-a-14)	(I-c-94)
(I-1317) to (I-1330)	(I-a-1) to (I-a-14)	(I-c-95)
(I-1331) to (I-1344)	(I-a-1) to (I-a-14)	(I-c-96)
(I-1345) to (I-1358)	(I-a-1) to (I-a-14)	(I-c-97)
(I-1359) to (I-1372)	(I-a-1) to (I-a-14)	(I-c-98)
(I-1373) to (I-1386)	(I-a-1) to (I-a-14)	(I-c-99)
(I-1387) to (I-1400)	(I-a-1) to (I-a-14)	(I-c-100)
(I-1401) to (I-1414)	(I-a-1) to (I-a-14)	(I-c-101)
(I-1415) to (I-1428)	(I-a-1) to (I-a-14)	(I-c-102)
(I-1429) to (I-1442)	(I-a-1) to (I-a-14)	(I-c-103)
(I-1443) to (I-1456)	(I-a-1) to (I-a-14)	(I-c-104)
(I-1457) to (I-1470)	(I-a-1) to (I-a-14)	(I-c-105)
(I-1471) to (I-1484)	(I-a-1) to (I-a-14)	(I-c-106)
(I-1485) to (I-1498)	(I-a-1) to (I-a-14)	(I-c-107)
(I-1499) to (I-1512)	(I-a-1) to (I-a-14)	(I-c-108)
(I-1513) to (I-1526)	(I-a-1) to (I-a-14)	(I-c-109)
(I-1527) to (I-1530)	(I-a-1) to (I-a-14)	(I-c-110)
(I-1541) to (I-1554)	(I-a-1) to (I-a-14)	(I-c-111)
(I-1555) to (I-1568)	(I-a-1) to (I-a-14)	(I-c-112)
(I-1569) to (I-1582)	(I-a-1) to (I-a-14)	(I-c-113)
(I-1583) to (I-1596)	(I-a-1) to (I-a-14)	(I-c-114)
(I-1597) to (I-1610)	(I-a-1) to (I-a-14)	(I-c-115)
(I-1611) to (I-1624)	(I-a-1) to (I-a-14)	(I-c-116)
(I-1625) to (I-1638)	(I-a-1) to (I-a-14)	(I-c-117)
(I-1639) to (I-1652)	(I-a-1) to (I-a-14)	(I-c-118)
(I-1653) to (I-1666)	(I-a-1) to (I-a-14)	(I-c-119)
(I-1667) to (I-1680)	(I-a-1) to (I-a-14)	(I-c-120)
(I-1681) to (I-1694)	(I-a-1) to (I-a-14)	(I-c-121)
(I-1695) to (I-1708)	(I-a-1) to (I-a-14)	(I-c-122)
(I-1709) to (I-1722)	(I-a-1) to (I-a-14)	(I-c-123)
(I-1723) to (I-1736)	(I-a-1) to (I-a-14)	(I-c-124)
(I-1737) to (I-1750)	(I-a-1) to (I-a-14)	(I-c-125)
(I-1751) to (I-1764)	(I-a-1) to (I-a-14)	(I-c-126)
(I-1765) to (I-1778)	(I-a-1) to (I-a-14)	(I-c-127)
(I-1779) to (I-1792)	(I-a-1) to (I-a-14)	(I-c-128)
(I-1793) to (I-1806)	(I-a-1) to (I-a-14)	(I-c-129)
(I-1807) to (I-1820)	(I-a-1) to (I-a-14)	(I-c-130)
(I-1821) to (I-1834)	(I-a-1) to (I-a-14)	(I-c-131)
(I-1835) to (I-1848)	(I-a-1) to (I-a-14)	(I-c-132)
(I-1849) to (I-1862)	(I-a-1) to (I-a-14)	(I-c-133)
(I-1863) to (I-1876)	(I-a-1) to (I-a-14)	(I-c-134)
(I-1877) to (I-1890)	(I-a-1) to (I-a-14)	(I-c-135)
(I-1891) to (I-1904)	(I-a-1) to (I-a-14)	(I-c-136)
(I-1905) to (I-1918)	(I-a-1) to (I-a-14)	(I-c-137)
(I-1919) to (I-1932)	(I-a-1) to (I-a-14)	(I-c-138)
(I-1933) to (I-1946)	(I-a-1) to (I-a-14)	(I-c-139)
(I-1947) to (I-1960)	(I-a-1) to (I-a-14)	(I-c-140)
(I-1961) to (I-1974)	(I-a-1) to (I-a-14)	(I-c-141)
(I-1975) to (I-1988)	(I-a-1) to (I-a-14)	(I-c-142)
(I-1989) to (I-2002)	(I-a-1) to (I-a-14)	(I-c-143)
(I-2003) to (I-2016)	(I-a-1) to (I-a-14)	(I-c-144)
(I-2017) to (I-2030)	(I-a-1) to (I-a-14)	(I-c-145)
(I-2031) to (I-2044)	(I-a-1) to (I-a-14)	(I-c-146)
(I-2045) to (I-2058)	(I-a-1) to (I-a-14)	(I-c-147)
(I-2059) to (I-2072)	(I-a-1) to (I-a-14)	(I-c-148)
(I-2073) to (I-2086)	(I-a-1) to (I-a-14)	(I-c-149)
(I-2087) to (I-2100)	(I-a-1) to (I-a-14)	(I-c-150)
(I-2101) to (I-2114)	(I-a-1) to (I-a-14)	(I-c-151)
(I-2115) to (I-2128)	(I-a-1) to (I-a-14)	(I-c-152)
(I-2129) to (I-2142)	(I-a-1) to (I-a-14)	(I-c-153)
(I-2143) to (I-2156)	(I-a-1) to (I-a-14)	(I-c-154)
(I-2157) to (I-2170)	(I-a-1) to (I-a-14)	(I-c-155)
(I-2171) to (I-2184)	(I-a-1) to (I-a-14)	(I-c-156)
(I-2185) to (I-2198)	(I-a-1) to (I-a-14)	(I-c-157)
(I-2199) to (I-2212)	(I-a-1) to (I-a-14)	(I-c-158)
(I-2213) to (I-2226)	(I-a-1) to (I-a-14)	(I-c-159)
(I-2227) to (I-2240)	(I-a-1) to (I-a-14)	(I-c-160)

Of these, the salt (I) is preferably salt (I-1) to salt (I-6), salt (I-15) to salt (I-20), salt (I-29) to salt (I-34), salt (I-43) to salt (I-48), salt (I-57) to salt (I-62), salt (I-71) to salt (I-76), salt (I-85) to salt (I-90), salt (I-99) to salt (I-104), salt (I-113) to salt (I-118), salt (I-127) to salt (I-132), salt (I-141) to salt (I-146), salt (I-155) to salt (I-160), salt (I-169) to salt (I-174), salt (I-183) to salt (I-188), salt (I-197) to salt (I-202), salt (I-211) to salt (I-216), salt (I-225) to salt (I-230), salt (I-239) to salt (I-244), salt (I-253) to salt (I-258), salt (I-267) to salt (I-272), salt (I-281) to salt (I-286), salt (I-295) to salt (I-300), salt (I-309) to salt (I-314), salt (I-323) to salt (I-328), salt (I-337) to salt (I-342), salt (I-351) to salt (I-356), salt (I-365) to salt (I-370), salt (I-379) to salt (I-384), salt (I-393) to salt (I-398), salt (I-407) to salt (I-412), salt (I-421) to salt (I-426), salt (I-435) to salt (I-440), salt (I-449) to salt (I-454), salt (I-463) to salt (I-468), salt (I-477) to salt (I-482), salt (I-491) to salt (I-496), salt (I-505) to salt (I-510), salt (I-519) to salt (I-524), salt (I-533) to salt (I-538), salt (I-547) to salt (I-552), salt (I-561) to salt (I-566), salt (I-575) to salt (I-580), salt (I-589) to salt (I-594), salt (I-603) to salt (I-608), salt (I-617) to salt (I-622), salt (I-631) to salt (I-636), salt (I-645) to salt (I-650), salt (I-659) to salt (I-664), salt (I-673) to salt (I-678), salt (I-687) to salt (I-692), salt (I-701) to salt (I-706), salt (I-715) to salt (I-720), salt (I-729) to salt (I-734), salt (I-743) to salt (I-748), salt (I-757) to salt (I-762), salt (I-771) to salt (I-776), salt (I-785) to salt (I-790), salt (I-799) to salt (I-804), salt (I-813) to salt (I-818), salt (I-827) to salt (I-832), salt (I-841) to salt (I-846), salt (I-855) to salt (I-860), salt (I-869) to salt (I-874), salt (I-883) to salt (I-888), salt (I-897) to salt (I-902), salt (I-911) to salt (I-916), salt (I-925) to salt (I-930), salt (I-939) to salt (I-944), salt (I-953) to salt (I-958), salt (I-967) to salt (I-972), salt (I-981) to salt (I-986), salt (I-995) to salt (I-1000), salt (I-1009) to salt (I-1014), salt (I-1023) to salt (I-1028), salt (I-1037) to salt (I-1042), salt (I-1051) to salt (I-1056), salt (I-1065) to salt (I-1070), salt (I-1079) to salt (I-1084), salt (I-1093) to salt (I-1098), salt (I-1107) to salt (I-1112), salt (I-1121) to salt (I-1126), salt (I-1135) to salt (I-1140), salt (I-1149) to salt (I-1154), salt (I-1163) to salt (I-1168), salt (I-1177) to salt (I-1182), salt (I-1191) to salt (I-1196), salt (I-1205) to salt (I-1210), salt (I-1219) to salt (I-1224), salt (I-1233) to salt (I-1238), salt (I-1247) to salt (I-1252), salt (I-1261) to salt (I-1266), salt (I-1275) to salt (I-1280), salt (I-1289) to salt (I-1294), salt (I-1303) to salt (I-1308), salt (I-1317) to salt (I-1322), salt (I-1331) to salt (I-1336), salt (I-1345) to salt (I-1350), salt (I-1359) to salt (I-1364), salt (I-1373) to salt (I-1378), salt (I-1387) to salt (I-1392), salt (I-1401) to salt (I-1406), salt (I-1415) to salt (I-1420), salt (I-1429) to salt (I-1434), salt (I-1443) to salt (I-1448), salt (I-1457) to salt (I-1462), salt (I-1471) to salt (I-1476), salt (I-1485) to salt (I-1490), salt (I-1499) to salt (I-1504), salt (I-1513) to salt (I-1518), salt (I-1527) to salt (I-1532), salt (I-1541) to salt (I-1546), salt (I-1555) to salt (I-1560), salt (I-1569) to salt (I-1574), salt (I-1583) to salt (I-1588), salt (I-1597) to salt (I-1602), salt (I-1611) to salt (I-1616), salt (I-1625) to salt (I-1630), salt (I-1639) to salt (I-1644), salt (I-1653) to salt (I-1658), salt (I-1667) to salt (I-1672), salt (I-1681) to salt (I-1686), salt (I-1695) to salt (I-1700), salt (I-1709) to salt (I-1714), salt (I-1723) to salt (I-1728), salt (I-1737) to salt (I-1742), salt (I-1751) to salt (I-1756), salt (I-1765) to salt (I-1770), salt (I-1779) to salt (I-1784), salt (I-1793) to salt (I-1798), salt (I-1807) to salt (I-1812), salt (I-1821) to salt (I-1826), salt (I-1835) to salt (I-1840), salt (I-1849) to salt (I-1854), salt (I-1863) to salt (I-1868), salt (I-1877) to salt (I-1882), salt (I-1891) to salt (I-1896), salt (I-1905) to salt (I-1910), salt (I-1919) to salt (I-1924), salt (I-1933) to salt (I-1938), salt (I-1947) to salt (I-1952), salt (I-1961) to salt (I-1966), salt (I-1975) to salt (I-1980), salt (I-1989) to salt (I-1994), salt (I-2003) to salt (I-2008), salt (I-2017) to salt (I-2022), salt (I-2031) to salt (I-2036), salt (I-2045) to salt (I-2050), salt (I-2059) to salt (I-2064), salt (I-2073) to salt (I-2078), salt (I-2087) to salt (I-2092), salt (I-2101) to salt (I-2106), salt (I-2115) to salt (I-2120), salt (I-2129) to salt (I-2134), salt (I-2143) to salt (I-2148), salt (I-2157) to salt (I-2162), salt (I-2171) to salt (I-2176), salt (I-2185) to salt (I-2190), salt (I-2199) to salt (I-2204), salt (I-2213) to salt (I-2218) and salt (I-2227) to salt (I-2232)

<Method for Producing Salt (I)>

The salt (I) can be produced by reacting a salt represented by formula (I-a) with a salt represented by formula (I-b) in the presence of a catalyst, in a solvent:

wherein symbols R¹, R², R⁴, R⁵, R⁷, R⁸, R^bb1, m1, m2, m4, m5 m7, m8, A¹, A², Q^b1, Q^b2, L_b1, Y^b1, L¹⁰ are X¹⁰ are the same as defined above, and

L^b2 represents a group in which —(CO)_(1-nn)—O— is eliminated form L^b1 end. nn represents 0 or 1.

Examples of the catalyst include carbonyldiimidazole, a base catalyst (dimethylaminopyridine) and the like.

Examples of the solvent include chloroform, monochlorobenzene, acetonitrile and the like.

The reaction temperature is usually 15° C. to 80° C., and the reaction time is usually 0.5 to 24 hours.

Examples of the salt represented by formula (I-a) include salts represented by the following formulas. These salts can be easily produced by a known production method.

Examples of the compound represented by formula (I-b) compounds represented by the following formulas. These compound are easily available on the market, or can be easily produced by a known production method.

[Structural Unit Derived from Salt Represented by Formula (I)]

The structural unit derived from a salt represented by formula (I) is a structural unit represented by formula (IP) (hereinafter sometimes referred to as “structural unit (IP)). Such structural unit (IP) functions as an acid generator similarly to the salt (I), and also functions as a structural unit constituting a compound or a resin.

[Resin Including Structural Unit (IP) Derived from Salt Represented by Formula (I)]

The resin of the present invention is a resin including a structural unit (IP) derived from a salt represented by formula (I) (hereinafter sometimes referred to as “resin (Ap)”)

wherein, in formula (IP), symbols R¹, R², R⁴, R³, R⁷, R⁸, R^bb1, m1, m2, m4, m5, m7, m8, A¹, A², Q^b1, Q^b2, L^b1, Y^b1, X¹⁰ and L¹⁰ are the same as defined above.

The structural unit (IP) indicates a state where a double bond of CH₂═C—R^bb1 included in the salt (I) is cleaved.

The resin (Ap) may be either a homopolymer including the structural unit (IP) alone, or a copolymer including two or more structural units (IP).

The resin (Ap) may include a structural unit other than the structural unit (IP). As mentioned later, examples of the structural unit other than the structural unit (IP) include a structural unit having an acid-labile group (hereinafter sometimes referred to as “structural unit (a1)”), a structural unit having no acid-labile group (hereinafter sometimes referred to as “structural unit (s)”), other structural unit (hereinafter sometimes referred to as “structural unit (t)”) and a structural unit known in the relevant field. Here, the “acid-labile group” means a group having a leaving group which is eliminated by contact with an acid, thus converting a constitutional unit into a constitutional unit having a hydrophilic group (e.g. a hydroxy group or a carboxy group).

The content of the structural unit (IP) is usually 0.1 mol % or more, preferably 0.5 mol % or more, more preferably 0.8 mol % or more, and still more preferably 1 mol % or more, based on all structural units of the resin (Ap). The content is also usually 100 mol % or less, preferably 50 mol % or less, more preferably 30 mol % or less, and still more preferably 10 mol % or less. Specifically, the content is usually 0.1 to 100 mol %, preferably 0.5 to 50 mol %, more preferably 0.8 to 30 mol %, and still more preferably 1 to 10 mol %.

As mentioned later, when the resin (Ap) is used for a resist composition, it may include, in addition to the structural unit (IP), a structural unit (a1).

As mentioned later, when the resin (Ap) is used for a resist composition, regardless of whether or not the structural unit (a1) is included, it may be used in combination with a resin including a structural unit (a1) (hereinafter sometimes referred to as “resin (A)”) and/or a resin other than the resin (A). Hereinafter, the resin (Ap) and/or the resin (A) is/are sometimes referred to as “resin (A) and/or the like”.

It is preferable that the resin (Ap) and the resin (A) each further include a structural unit other than the structural unit (a1), respectively.

Examples of the structural unit other than the structural unit (a1) include a structural unit having no acid-labile group (hereinafter sometimes referred to as “structural unit (s)”), other structural unit (hereinafter sometimes referred to as “structural unit (t)”) and a structural unit known in the relevant field.

<Structural Unit (a1)>

The structural unit (a1) is derived from a monomer having an acid-labile group (hereinafter sometimes referred to as “monomer (a1)”).

The acid-labile group contained in the resin (A) or the like is preferably a group represented by formula (1) (hereinafter also referred to as group (1)) and/or a group represented by formula (2) (hereinafter also referred to as group (2)):

wherein, in formula (1), R^a1, R^a2 and R^a3 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group obtained by combining these groups, or R^a1 and R^a2 are bonded to each other to form a nonaromatic hydrocarbon ring having 3 to 20 carbon atoms together with carbon atoms to which R^a1 and R^a2 are bonded,

ma and na each independently represent 0 or 1, and at least one of ma and na represents 1, and

* represents a bonding site:

wherein, in formula (2), R^a1′ and R^a2′ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, R^a3′ represents a hydrocarbon group having 1 to 20 carbon atoms, or R^a2′ and R^a3′ are bonded to each other to form a heterocyclic ring having 3 to 20 carbon atoms together with carbon atoms and X to which R^a2′ and R^a3′ are bonded, and —CH₂— included in the hydrocarbon group and the heterocyclic ring may be replaced by —O— or —S—,

X represents an oxygen atom or a sulfur atom,

na′ represents 0 or 1, and

* represents a bonding site.

Examples of the alkyl group in R^a1, R^a2 and R^a3 include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group and the like.

Examples of the alkenyl group in R^a1, R^a2 and R^a3 include an ethenyl group, a propenyl group, an isopropenyl group, a butenyl group, an isobutenyl group, a tert-butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, an isooctenyl group and a nonenyl group.

The alicyclic hydrocarbon group in R^a1, R^a2 and R^a3 may be either monocyclic or polycyclic. Examples of the monocyclic alicyclic hydrocarbon group include cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group and a cyclooctyl group. Examples of the polycyclic alicyclic hydrocarbon group include a decahydronaphthyl group, an adamantyl group, a norbornyl group and the following groups (* represents a bonding site). The number of carbon atoms of the alicyclic hydrocarbon group of R^a1, R^a2 and R^a3 is preferably 3 to 16.

Examples of the aromatic hydrocarbon group in R^a1, R^a2 and R^a3 include aryl groups such as a phenyl group, a naphthyl group, an anthryl group, a biphenyl group and a phenanthryl group.

Examples of the combined group include groups obtained by combining the above-mentioned alkyl group and alicyclic hydrocarbon group (e.g., alkylcycloalkyl groups or cycloalkylalkyl groups, such as a methylcyclohexyl group, a dimethylcyclohexyl group, a methylnorbornyl group, a cyclohexylmethyl group, an adamantylmethyl group, an adamantyldimethyl group and a norbornylethyl group), aralkyl groups such as a benzyl group, aromatic hydrocarbon groups having an alkyl group (a p-methylphenyl group, a p-tert-butylphenyl group, a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a 2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group, etc.), aromatic hydrocarbon groups having an alicyclic hydrocarbon group (a p-cyclohexylphenyl group, a p-adamantylphenyl group, etc.), aryl-cycloalkyl groups such as a phenylcyclohexyl group, and the like.

Preferably, ma is 0 and na is 1.

When R^a1 and R^a2 are bonded to each other to form a nonaromatic hydrocarbon ring, examples of —C(R^a1) (R^a2) (R^a3) include the following rings. The nonaromatic hydrocarbon ring preferably has 3 to 12 carbon atoms. * represents a bonding site to —O—.

Examples of the hydrocarbon group in R^a1′, R^a2′ and R^a3′ include an alkyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and groups formed by combining these groups.

Examples of the alkyl group, the alicyclic hydrocarbon group, the aromatic hydrocarbon group, and groups formed by combining these groups include those which are the same as mentioned in R^a1, R^a2 and R^a3.

When R^a2′ and R^a3′ are bonded to each other to form a heterocyclic ring together with carbon atoms and X to which

R^a2′ and R^a3′ are bonded, examples of —C(R^a1′) (R^a2′)—X—R^a3′ include the following rings. * represents a bonding site.

At least one of R^a1′ and R^a2′ is preferably a hydrogen atom.

na′ is preferably 0.

Examples of the group (1) include the following groups.

A group wherein, in formula (1), R^a1, R^a2 and R^a3 are alkyl groups, ma=0 and na=1. The group is preferably a tert-butoxycarbonyl group.

A group wherein, in formula (1), R^a1 and R^a2 are bonded to each other to form an adamantyl group together with carbon atoms to which R^a1 and R^a2 are bonded, R^a3 is an alkyl group, ma=0 and na=1.

A group wherein, in formula (1), R^a1 and R^a2 are each independently an alkyl group, R^a3 is an adamantyl group, ma=0 and na=1.

Specific examples of the group (1) include the following groups. * represents a bonding site.

Specific examples of the group (2) include the following groups. * represents a bonding site.

The monomer (a1) is preferably a monomer having an acid-labile group and an ethylenic unsaturated bond, and more preferably a (meth)acrylic monomer having an acid-labile group.

Of the (meth)acrylic monomers having an acid-labile group, those having an alicyclic hydrocarbon group having 5 to 20 carbon atoms are preferably exemplified. When a resin (A) including a structural unit derived from a monomer (a1) having a bulky structure such as an alicyclic hydrocarbon group is used in a resist composition, it is possible to improve the resolution of a resist pattern.

The structural unit derived from a (meth)acrylic monomer having a group (1) includes a structural unit represented by formula (a1-0) (hereinafter sometimes referred to as structural unit (a1-0)), a structural unit represented by formula (a1-1) (hereinafter sometimes referred to as structural unit (a1-1)) or a structural unit represented by formula (a1-2) (hereinafter sometimes referred to as structural unit (a1-2)). Preferably, the structural unit is at least one structural unit selected from the group consisting of a structural unit (a1-0), a structural unit (a1-1) and a structural unit (a1-2), and more preferably at least one structural unit selected from the group consisting of a structural unit (a1-1) and a structural unit (a1-2). These structural units may be used alone, or two or more structural units may be used in combination.

In formula (a1-0), formula (a1-1) and formula (a1-2),

L^a01, L^a1 and L^a2 each independently represent —O— or *—O—(CH₂)_k1—CO—O—, k1 represents an integer of 1 to 7, and * represents a bonding site to —CO—,

R^a01, R^a4 and R^a5 each independently represent a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom,

R^a02, R^a03 and R^a04 each independently represent an alkyl group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group obtained by combining these groups,

R^a6 and R^a7 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group obtained by combining these groups,

m1′ represents an integer of 0 to 14,

n1 represents an integer of 0 to 10, and

n1′ represents an integer of 0 to 3.

R^a01, R^a4 and R^a5 are preferably a hydrogen atom or a methyl group, and more preferably a methyl group.

L^a01, L^a1 and L^a2 are preferably an oxygen atom or *—O—(CH₂)_k01—CO—O— (in which k01 is preferably an integer of 1 to 4, and more preferably 1), and more preferably an oxygen atom.

Examples of the alkyl group, the alicyclic hydrocarbon group, the aromatic hydrocarbon group, and groups obtained by combining these groups in R^a02, R^a03 and R^a04 include the same groups as mentioned as for R^a1, R^a2 and R^a3 of the group (1).

Examples of the alkyl group, the alkenyl group, the alicyclic hydrocarbon group, the aromatic hydrocarbon group, and groups obtained by combining these groups in R^a6 and R^a7 include the same groups as mentioned as for R^a1, R^a2 and R^a3 of formula (1).

The alkyl group in R^a02, R^a03 and R^a04 is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group or an ethyl group, and still more preferably a methyl group.

The alkyl group in R^a6 and R^a7 is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group, an ethyl group, an isopropyl group or a t-butyl group, and still more preferably an ethyl group, an isopropyl group or a t-butyl group.

The alkenyl group in R^a6 and R^a7 is preferably an alkenyl group having 2 to 6 carbon atoms, and more preferably an ethenyl group, a propenyl group, an isopropenyl group or a butenyl group.

The number of carbon atoms of the alicyclic hydrocarbon group as for R^a02, R^a03, R^a04, R^a6 and R^a7 is preferably 5 to 12, and more preferably 5 to 10.

The number of carbon atoms of the aromatic hydrocarbon group of R^a02, R^a03, R^a04, R^a56 and R^a7 is preferably 6 to 12, and more preferably 6 to 10.

The total number of carbon atoms of the group obtained by combining the alkyl group with the alicyclic hydrocarbon group is preferably 18 or less.

The total number of carbon atoms of the group obtained by combining the alkyl group with the aromatic hydrocarbon group is preferably 18 or less.

R^a02 and R^a03 are preferably an alkyl group having 1 to 6 carbon atoms or an aromatic hydrocarbon group having 6 to 12 carbon atoms, and more preferably a methyl group, an ethyl group, a phenyl group or a naphthyl group.

R^a04 is preferably an alkyl group having 1 to 6 carbon atoms or an alicyclic hydrocarbon group having 5 to 12 carbon atoms, and more preferably a methyl group, an ethyl group, a cyclohexyl group or an adamantyl group.

Preferably, R^a6 and R^a7 are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms or an aromatic hydrocarbon group having 6 to 12 carbon atoms, more preferably a methyl group, an ethyl group, an isopropyl group, a t-butyl group, an ethenyl group, a phenyl group or a naphthyl group, and still more preferably an ethyl group, an isopropyl group, a t-butyl group, an ethenyl group or a phenyl group.

m1′ is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1′ is preferably 0 or 1.

The structural unit (a1-0) includes, for example, a structural unit represented by any one of formula (a1-O—1) to formula (a1-O—18) and a structural unit in which a methyl group corresponding to R^a01 in the structural unit (a1-0) is substituted with a hydrogen atom, a halogen atom, a haloalkyl group or other alkyl groups, and is preferably a structural unit represented by any one of formula (a1-O—1) to formula (a1-O—10), formula (a1-O—13) and formula (a1-O—14).

The structural unit (a1-1) includes, for example, structural units derived from the monomers mentioned in JP 2010-204646 A. Of these structural units, a structural unit represented by any one of formula (a1-1-1) to formula (a1-1-7) and a structural unit in which a methyl group corresponding to R^a4 in the structural unit (a1-1) is substituted with a hydrogen atom, a halogen atom, a haloalkyl group or other alkyl groups are preferable, and a structural unit represented by any one of formula (a1-1-1) to formula (a1-1-4) is more preferable.

Examples of the structural unit (a1-2) include a structural unit represented by any one of formula (a1-2-1) to formula (a1-2-14), and a structural unit in which a methyl group corresponding to R^as in the structural unit (a1-2) is substituted with a hydrogen atom, a halogen atom, a haloalkyl group or other alkyl groups, and a structure unit represented by any one of formula (a1-2-2), formula (a1-2-5), formula (a1-2-6) and formula (a1-2-10) to formula (a1-2-14) is preferable.

When the resin (A) or the like includes a structural unit (a1-0) and/or a structural unit (a1-1) and/or a structural unit (a1-2), the total content of them is usually 10 mol % or more, preferably 15 mol % or more, more preferably 20 mol % or more, still more preferably 25 mol % or more, and yet more preferably 30 mol % or more, based on all structural units of the resin (A) or the like. The total content is also usually 95 mol % or less, preferably 90 mol % or less, more preferably 85 mol % or less, and still more preferably 70 mol % or less, based on all structural units of the resin (A) or the like. Specifically, the total content is usually 10 to 95 mol %, preferably 15 to 90 mol %, more preferably 20 to 85 mol %, still more preferably 25 to 70 mol %, and yet more preferably 30 to 70 mol %, based on all structural units of the resin (A) or the like.

When the resin (A) or the like includes a structural unit (a1-0), the content is usually 5 mol % or more, and preferably 10 mol % or more, based on all structural units of the resin (A) or the like. The content is also usually 80 mol % or less, preferably 75 mol % or less, and more preferably 70 mol % or less, based on all structural units of the resin (A) or the like. Specifically, the content is usually 5 to 80 mol %, preferably 5 to 75 mol %, and more preferably 10 to 70 mol %, based on all structural units of the resin (A) or the like.

When the resin (A) or the like includes a structural unit (a1-1) and/or a structural unit (a1-2), the total content of them is usually 10 mol % or more, preferably 15 mol % or more, more preferably 20 mol % or more, still more preferably 25 mol % or more, and yet more preferably 30 mol % or more, based on all structural units of the resin (A) or the like. The total content is also usually 95 mol % or less, preferably 90 mol % or less, more preferably 85 mol % or less, still more preferably 80 mol % or less, yet more preferably 75 mol % or less, and further preferably 70 mol % or less, based on all structural units of the resin (A) or the like. Specifically, the total content is usually 10 to 90 mol %, preferably 15 to 85 mol %, more preferably 15 to 80 mol %, still more preferably 20 to 80 mol %, yet more preferably 20 to 75 mol %, and further preferably 20 to 70 mol %, based on all structural units of the resin (A) or the like.

In the structural unit (a1), examples of the structural unit having a group (2) include a structural unit represented by formula (a1-4) (hereinafter sometimes referred to as “structural unit (a1-4)”):

wherein, in formula (a1-4),

R^a32 represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom,

R^a33 represents a halogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, an alkoxyalkoxy group having 2 to 12 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, an acryloyloxy group or a methacryloyloxy group,

A^a30 represents a single bond or *—X^a31-(A^a32-X^a32)_nc, and * represents a bonding site to carbon atoms to which —R^a32 is bonded,

A^a32 represents an alkanediyl group having 1 to 8 carbon atoms,

X^a31 and X^a32 each independently represent —O—, —CO—O— or —O—CO—,

nc represents 0 or 1,

la represents an integer of 0 to 4, and when la is an integer of 2 or more, a plurality of R^a33 may be the same or different from each other, and

R^a34 and R^a35 each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, R^a36 represents a hydrocarbon group having 1 to 20 carbon atoms, or R^a35 and R^a36 are bonded to each other to form a divalent hydrocarbon group having 2 to 20 carbon atoms together with —C—O— to which R^a35 and R^a36 are bonded, and —CH₂— included in the hydrocarbon group and the divalent hydrocarbon group may be replaced by —O— or —S—.

Examples of the halogen atom in R^a32 and R^a33 include a fluorine atom, a chlorine atom and a bromine atom.

Examples of the alkyl group having 1 to 6 carbon atoms which may have a halogen atom in R^a32 include a trifluoromethyl group, a difluoromethyl group, a methyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a propyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, a perfluoropentyl group, a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, a hexyl group and a perfluorohexyl group.

R^a32 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group or an ethyl group, and still more preferably a hydrogen atom or a methyl group.

Examples of the alkyl group in R^a33 include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group and a hexyl group. The alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group or an ethyl group, and still more preferably a methyl group.

Examples of the alkoxy group in R^a33 include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy group and a hexyloxy group. The alkoxy group is preferably an alkoxy group having 1 to 4 carbon atoms, more preferably a methoxy group or an ethoxy group, and still more preferably a methoxy group.

Examples of the alkoxyalkyl group in R^a33 include a methoxymethyl group, an ethoxyethyl group, a propoxymethyl group, an isopropoxymethyl group, a butoxymethyl group, a sec-butoxymethyl group and a tert-butoxymethyl group. The alkoxyalkyl group is preferably an alkoxyalkyl group having 2 to 8 carbon atoms, more preferably a methoxymethyl group or an ethoxyethyl group, and still more preferably a methoxymethyl group.

Examples of the alkoxyalkoxy group in R^a33 include a methoxymethoxy group, a methoxyethoxy group, an ethoxymethoxy group, an ethoxyethoxy group, a propoxymethoxy group, an isopropoxymethoxy group, a butoxymethoxy group, a sec-butoxymethoxy group and a tert-butoxymethoxy group. The alkoxyalkoxy group is preferably an alkoxyalkoxy group having 2 to 8 carbon atoms, and more preferably a methoxyethoxy group or an ethoxyethoxy group.

Examples of the alkylcarbonyl group in R^a33 include an acetyl group, a propionyl group and a butyryl group. The alkylcarbonyl group is preferably an alkylcarbonyl group having 2 to 3 carbon atoms, and more preferably an acetyl group.

Examples of the alkylcarbonyloxy group in R^a33 include an acetyloxy group, a propionyloxy group and a butyryloxy group. The alkylcarbonyloxy group is preferably an alkylcarbonyloxy group having 2 to 3 carbon atoms, and more preferably an acetyloxy group.

R^a33 is preferably a halogen atom, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms or an alkoxyalkoxy group having 2 to 8 carbon atoms, more preferably a fluorine atom, an iodine atom, a hydroxy group, a methyl group, a methoxy group, an ethoxy group, an ethoxyethoxy group or an ethoxymethoxy group, and still more preferably a fluorine atom, an iodine atom, a hydroxy group, a methyl group, a methoxy group or an ethoxyethoxy group.

Examples of the *—X^a31-(A^a32-X^a32)_nc— include *—O—, *—CO—O—, *—O—CO—, *—CO—O-A^a32-CO—O—, *—O—CO-A^a32-O—, *—O-A^a32-CO—O—, *—CO—O-A^a32-O—CO— and *—O—CO-A^a32-O—CO. Of these, *—CO—O—, *—CO—O-A^a32-CO—O— or *—O-A^a32-CO—O— is preferable.

Examples of the alkanediyl group include a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group.

A^a32 is preferably a methylene group or an ethylene group.

A^a30 is preferably a single bond, *—CO—O— or *—CO—O-A^a32-CO—O—, more preferably a single bond, *—CO—O— or *—CO—O—CH₂—CO—O—, and still more preferably a single bond or *—CO—O—.

la is preferably 0, 1 or 2, more preferably 0 or 1, and still more preferably 0.

Examples of the hydrocarbon group in R^a34, R^a35 and R^a36 include an alkyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and groups obtained by combining these groups.

Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group and the like.

The alicyclic hydrocarbon group may be either monocyclic or polycyclic. Examples of the monocyclic alicyclic hydrocarbon group include cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group and a cyclooctyl group. Examples of the polycyclic alicyclic hydrocarbon group include a decahydronaphthyl group, an adamantyl group, a norbornyl group, and the following groups (* represents a bonding site).

Examples of the aromatic hydrocarbon group include aryl groups such as a phenyl group, a naphthyl group, an anthryl group, a biphenyl group and a phenanthryl group.

Examples of the combined group include groups obtained by combining the above-mentioned alkyl group and alicyclic hydrocarbon group (e.g., alkylcycloalkyl groups or cycloalkylalkyl groups, such as a methylcyclohexyl group, a dimethylcyclohexyl group, a methylnorbornyl group, a cyclohexylmethyl group, an adamantylmethyl group, an adamantyldimethyl group and a norbornylethyl group), aralkyl groups such as a benzyl group, aromatic hydrocarbon groups having an alkyl group (a p-methylphenyl group, a p-tert-butylphenyl group, a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a 2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group, etc.), aromatic hydrocarbon groups having an alicyclic hydrocarbon group (a p-cyclohexylphenyl group, a p-adamantylphenyl group, etc.), aryl-cycloalkyl groups such as a phenylcyclohexyl group and the like. Particularly, examples of R^a36 include an alkyl group having 1 to 18 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group formed by combining these groups.

R^a34 is preferably a hydrogen atom.

R^a35 is preferably a hydrogen atom, an alkyl group having 1 to 12 carbon atoms or an alicyclic hydrocarbon group having 3 to 12 carbon atoms, and more preferably a methyl group or an ethyl group.

The hydrocarbon group of R^a36 is preferably an alkyl group having 1 to 18 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group formed by combining these groups, and more preferably an alkyl group having 1 to 18 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms or an aralkyl group having 7 to 18 carbon atoms. The alkyl group and the alicyclic hydrocarbon group in R^a36 are preferably unsubstituted. The aromatic hydrocarbon group in R^a36 is preferably an aromatic ring having an aryloxy group having 6 to 10 carbon atoms. —OC(R^a34) (R^a35)—O—R^a36 in the structural unit (a1-4) is eliminated by contacting with an acid (e.g., p-toluenesulfonic acid) to form a hydroxy group. —OC(R^a34) (R^a35)—O—R^a36 is preferably bonded at the m-position or the p-position, and more preferably the p-position of the benzene ring.

The structural unit (a1-4) includes, for example, structural units derived from the monomers mentioned in JP 2010-204646 A. The structural unit preferably includes structural units represented by formula (a1-4-1) to formula (a1-4-24) and a structural unit in which a hydrogen atom corresponding to R^a32 in the structural unit (a1-4) is substituted with a halogen atom, a haloalkyl group or an alkyl group, and more preferably structural units represented by formula (a1-4-1) to formula (a1-4-5), formula (a1-4-10), formula (a1-4-13), formula (a1-4-14), formula (a1-4-19) and formula (a1-4-20).

When the resin (A) or the like includes the structural unit (a1-4), the content is preferably 3 to 80 mol %, more preferably 5 to 75 mol %, still more preferably 7 to 70 mol %, yet more preferably 7 to 65 mol %, and further preferably 10 to 60 mol %, based on the total of all structural units of the resin (A) or the like.

The structural unit derived from a (meth)acrylic monomer having a group (2) also includes a structural unit represented by formula (a1-5) (hereinafter sometimes referred to as “structural unit (a1-5)”):

wherein, in formula (a1-5),

R^a8 represents an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, a hydrogen atom or a halogen atom,

Z^a1 represents a single bond or *—(CH₂)_h3—CO-L⁵⁴-, h3 represents an integer of 1 to 4, and * represents a bonding site to L⁵¹,

L⁵¹, L⁵², L⁵³ and L⁵⁴ each independently represent —O— or —S—,

s1 represents an integer of 1 to 3, and

s1′ represents an integer of 0 to 3.

The halogen atom includes a fluorine atom and a chlorine atom and is preferably a fluorine atom.

Examples of the alkyl group having 1 to 6 carbon atoms which may have a halogen atom include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a fluoromethyl group and a trifluoromethyl group.

In formula (a1-5), R^a8 is preferably a hydrogen atom, a methyl group or a trifluoromethyl group,

L⁵ 1 is preferably an oxygen atom,

one of L⁵² and L⁵³ is preferably —O— and the other one is preferably —S—,

s1 is preferably 1,

s1′ is preferably an integer of 0 to 2, and

Z^a1 is preferably a single bond or *—CH₂—CO—O—.

The structural unit (a1-5) includes, for example, structural units derived from the monomers mentioned in JP 2010-61117 A. Of these structural units, structural units represented by formula (a1-5-1) to formula (a1-5-4) are preferable, and structural units represented by formula (a1-5-1) or formula (a1-5-2) are more preferable.

When the resin (A) or the like includes the structural unit (a1-5), the content is preferably 1 to 50 mol %, more preferably 3 to 45 mol %, still more preferably 5 to 40 mol %, and yet more preferably 5 to 30 mol %, based on all structural units of the resin (A) or the like.

The structural unit (a1) also includes the following structural units.

When the resin (A) or the like includes structural units such as (a1-3-1) to (a1-3-7), the content is preferably 10 to 95 mol %, more preferably 15 to 90 mol %, still more preferably 20 to 85 mol %, yet more preferably 20 to 70 mol %, and particularly preferably 20 to 60 mol %, based on all structural units of the resin (A) or the like.

The structural unit (a1) also includes the following structural units.

When the resin (A) or the like includes structural units such as (a1-6-1) to (a1-6-3), the content is preferably 10 to 60 mol %, more preferably 15 to 55 mol %, still more preferably 20 to 50 mol %, yet more preferably 20 to 45 mol %, and particularly preferably 20 to 40 mol %, based on all structural units of the resin (A) or the like.

<Structural Unit (s)>

The structural unit (s) is derived from a monomer having no acid-labile group (hereinafter sometimes referred to as “monomer (s)”). It is possible to use, as the monomer from which the structural unit (s) is derived, a monomer having no acid-labile group known in the resist field.

The structural unit (s) preferably has a hydroxy group or a lactone ring. When a resin including a structural unit having a hydroxy group and having no acid-labile group (hereinafter sometimes referred to as “structural unit (a2)”) and/or a structural unit having a lactone ring and having no acid-labile group (hereinafter sometimes referred to as “structural unit (a3)”) is used in the resist composition of the present invention, it is possible to improve the resolution of a resist pattern and the adhesion to a substrate.

<Structural Unit (a2)>

The structural unit (a2) is a structural unit represented by formula (a2) and has an alcoholic hydroxy group or phenolic hydroxy group:

wherein, in formula (a2),

R^a50 represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom,

A^a50 represents a single bond or *—X^a51-(A^a52-X^a52)_nb— and * represents a bonding site to carbon atoms to which —R^a50 is bonded,

A^a52 represents an alkanediyl group having 1 to 8 carbon atoms,

X^a51 and X^a52 each independently represent —O—, —CO—O— or —O—CO—,

nb represents 0 or 1,

W^a50 represents a cyclic hydrocarbon group having 5 to 12 carbon atoms which may have a substituent,

L^a50 represents a single bond or a chain hydrocarbon group having 1 to 12 carbon atoms which may have a fluorine atom, and

ma50 represents an integer of 1 to 5.

Examples of the halogen atom in R^a50 include a fluorine atom, a chlorine atom and a bromine atom.

Examples of the alkyl group having 1 to 6 carbon atoms which may have a halogen atom in R^a50 include a trifluoromethyl group, a difluoromethyl group, a methyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a propyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, a perfluoropentyl group, a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, a hexyl group and a perfluorohexyl group. The number of carbon atoms of the alkyl group is preferably 1 to 4, more preferably 1 to 3, and still more preferably 1 or 2.

R^a50 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group or an ethyl group, and still more preferably a hydrogen atom or a methyl group.

Examples of the alkanediyl group as for A^a52 in A^a50 include a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group. The number of carbon atoms of the alkanediyl group is preferably 1 to 6, more preferably 1 to 4, still more preferably 1 to 3, and yet more preferably 1 or 2.

A^a52 is preferably a methylene group or an ethylene group.

Examples of *—X^a51-(A^a52-X^a52)_nb— include *—O—, *—CO—O—, *—O—CO—, *—CO—O-A^a52-CO—O—, *—O—CO-A^a52-O—, *—O-A^a52-CO—O—, *—CO—O-A^a52-O—CO— and *—O—CO-A^a52-O—CO—. Of these, *—CO—O—, *—CO—O-A^a52-CO—O— or *—O-A^a52-CO—O— is preferable.

A^a50 is preferably a single bond, *—CO—O— or *—CO—O-A^a52-CO—O—, more preferably a single bond, *—CO—O— or *—CO—O—CH₂—CO—O—, and still more preferably a single bond or *—CO—O—.

Examples of the cyclic hydrocarbon group as for W^a50 include a divalent alicyclic hydrocarbon group and a divalent aromatic hydrocarbon group.

Examples of the monocyclic divalent alicyclic hydrocarbon group in W^a50 include monocyclic cycloalkanediyl groups such as a cyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group and a cyclooctane-1,5-diyl group. Examples of the polycyclic divalent alicyclic hydrocarbon group include polycyclic cycloalkanediyl groups such as a norbornane-1,4-diyl group, a norbornane-2,5-diyl group, an adamantane-1,5-diyl group and an adamantane-2,6-diyl group.

The number of carbon atoms of the alicyclic hydrocarbon group is preferably 6 to 12, and more preferably 6 to 10.

Examples of the divalent aromatic hydrocarbon group in W^a50 include a phenylene group and a naphthyl group.

The number of carbon atoms of the aromatic hydrocarbon group is preferably 6 to 12, and more preferably 6 to 10. Examples of the substituent which may be possessed by the cyclic hydrocarbon group having 5 to 12 carbon atoms as for W^a50 include a halogen atom, a hydroxy group, an alkyl group having 1 to 12 carbon atoms, a haloalkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, an alkoxyalkoxy group having 2 to 12 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, an acryloyloxy group or a methacryloyloxy group. The number of substituents possessed by W^a50 may be 1, or 2 or more.

Examples of the halogen atom include a fluorine atom, a chlorine atom and a bromine atom.

Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group and a hexyl group. The number of carbon atoms of the alkyl group is preferably 1 to 6, more preferably 1 to 4, and still more preferably 1 to 3. The alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group or an ethyl group, and still more preferably a methyl group.

Examples of the haloalkyl group include a trifluoromethyl group, a difluoromethyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutyl group, a perfluoropentyl group, a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a perfluorohexyl group, a chloromethyl group, a bromomethyl group, an iodomethyl group and the like. The number of carbon atoms of the haloalkyl group is preferably 1 to 6, more preferably 1 to 4, and still more preferably 1 to 3.

Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a sec-butoxy group and a tert-butoxy group. The number of carbon atoms of the alkoxy group is preferably 1 to 6, more preferably 1 to 4, and still more preferably 1 to 3. The alkoxy group is preferably an alkoxy group having 1 to 4 carbon atoms, more preferably a methoxy group or an ethoxy group, and still more preferably a methoxy group.

Examples of the alkoxyalkyl group include a methoxymethyl group, an ethoxyethyl group, a propoxymethyl group, an isopropoxymethyl group, a butoxymethyl group, a sec-butoxymethyl group and a tert-butoxymethyl group. The alkoxyalkyl group is preferably an alkoxyalkyl group having 2 to 8 carbon atoms, more preferably a methoxymethyl group or an ethoxyethyl group, and still more preferably a methoxymethyl group.

Examples of the alkoxyalkoxy group include a methoxymethoxy group, a methoxyethoxy group, an ethoxymethoxy group, an ethoxyethoxy group, a propoxymethoxy group, an isopropoxymethoxy group, a butoxymethoxy group, a sec-butoxymethoxy group and a tert-butoxymethoxy group. The alkoxyalkoxy group is preferably an alkoxyalkoxy group having 2 to 8 carbon atoms, and more preferably a methoxyethoxy group or an ethoxyethoxy group.

Examples of the alkylcarbonyl group include an acetyl group, a propionyl group and a butyryl group. The alkylcarbonyl group is preferably an alkylcarbonyl group having 2 to 3 carbon atoms, and more preferably an acetyl group.

Examples of the alkylcarbonyloxy group include an acetyloxy group, a propionyloxy group and a butyryloxy group. The alkylcarbonyloxy group is preferably an alkylcarbonyloxy group having 2 to 3 carbon atoms, and more preferably an acetyloxy group.

The substituent of the cyclic hydrocarbon group as for W^a50 is preferably a halogen atom, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms or an alkoxyalkoxy group having 2 to 8 carbon atoms, more preferably a fluorine atom, an iodine atom, a hydroxy group, a methyl group, a methoxy group, an ethoxy group, an ethoxyethoxy group or an ethoxymethoxy group, and still more preferably a fluorine atom, an iodine atom, a hydroxy group, a methyl group, a methoxy group or an ethoxyethoxy group.

Examples of the chain hydrocarbon group having 1 to 12 carbon atoms as for L^a50 include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diyl group and a dodecane-1,12-diyl group; and branched alkanediyl groups such as an ethane-1,1-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diyl group, a 1-methylpropane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a 1-dimethylpropane-1,3-diyl group, a pentane-2,4-diyl group, a pentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group.

The number of carbon atoms of the chain hydrocarbon group is preferably 1 to 10, more preferably 1 to 8, still more preferably 1 to 6, and yet more preferably 1 to 4.

The number of fluorine atoms possessed by L^a50 may be 1, or 2 or more.

ma50 is preferably an integer of 1 to 4, and more preferably an integer of 1 to 3.

When a resist pattern is produced from the resist composition of the present invention, in the case of using, as an exposure source, high energy rays such as KrF excimer laser (248 nm), electron beam or extreme ultraviolet light (EUV), a structural unit (a2) having a phenolic hydroxy group is preferably used, and the below-mentioned structural unit (a2-A) is more preferably used, as the structural unit (a2). When using ArF excimer laser (193 nm) or the like, a structural unit (a2) having an alcoholic hydroxy group is preferably used, and the below-mentioned a structural unit (a2-1) is more preferably used, as the structural unit (a2). The structural unit (a2) may be included alone, or two or more structural units may be included.

In the structural unit (a2), examples of the structural unit having a phenolic hydroxy group include a structural unit represented by formula (a2-A) (hereinafter sometimes referred to as “structural unit (a2-A)”):

wherein, in formula (a2-A),

R^a50 represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, R^a51 represents a halogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, an alkoxyalkoxy group having 2 to 12 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, an acryloyloxy group or a methacryloyloxy group,

A^a50 represents a single bond or *—X^a51-(A^a52-X^a52)_nb and * represents a bonding site to carbon atoms to which —R^a50 is bonded,

A^a52 represents an alkanediyl group having 1 to 8 carbon atoms,

X^a51 and X^a52 each independently represent —O—, —CO—O— or —O—CO—,

nb represents 0 or 1, and

mb represents an integer of 0 to 4, and when mb is an integer of 2 or more, a plurality of R^a51 may be the same or different from each other.

Examples of R^a50 and A^a50 include the same groups as mentioned in formula (a2).

Examples of the halogen atom in R^a50 include a fluorine atom, a chlorine atom and a bromine atom.

Examples of the alkyl group in R^a51 include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group and a hexyl group. The alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group or an ethyl group, and still more preferably a methyl group.

Examples of the alkoxy group in R^a51 include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a sec-butoxy group and a tert-butoxy group. The alkoxy group is preferably an alkoxy group having 1 to 4 carbon atoms, more preferably a methoxy group or an ethoxy group, and still more preferably a methoxy group.

Examples of the alkoxyalkyl group in R^a51 include a methoxymethyl group, an ethoxyethyl group, a propoxymethyl group, an isopropoxymethyl group, a butoxymethyl group, a sec-butoxymethyl group and a tert-butoxymethyl group. The alkoxyalkyl group is preferably an alkoxyalkyl group having 2 to 8 carbon atoms, more preferably a methoxymethyl group or an ethoxyethyl group, and still more preferably a methoxymethyl group.

Examples of the alkoxyalkoxy group in R^a51 include a methoxymethoxy group, a methoxyethoxy group, an ethoxymethoxy group, an ethoxyethoxy group, a propoxymethoxy group, an isopropoxymethoxy group, a butoxymethoxy group, a sec-butoxymethoxy group and a tert-butoxymethoxy group. The alkoxyalkoxy group is preferably an alkoxyalkoxy group having 2 to 8 carbon atoms, and more preferably a methoxyethoxy group or an ethoxyethoxy group.

Examples of the alkylcarbonyl group in R^a51 include an acetyl group, a propionyl group and a butyryl group. The alkylcarbonyl group is preferably an alkylcarbonyl group having 2 to 3 carbon atoms, and more preferably an acetyl group.

Examples of the alkylcarbonyloxy group in R^a51 include an acetyloxy group, a propionyloxy group and a butyryloxy group. The alkylcarbonyloxy group is preferably an alkylcarbonyloxy group having 2 to 3 carbon atoms, and more preferably an acetyloxy group.

R^a51 is preferably a halogen atom, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms or an alkoxyalkoxy group having 2 to 8 carbon atoms, more preferably a fluorine atom, an iodine atom, a hydroxy group, a methyl group, a methoxy group, an ethoxy group, an ethoxyethoxy group or an ethoxymethoxy group, and still more preferably a fluorine atom, an iodine atom, a hydroxy group, a methyl group, a methoxy group or an ethoxyethoxy group.

mb is preferably 0, 1 or 2, and more preferably 0 or 1.

At least one hydroxy group is preferably bonded at the m-position or the p-position of the benzene ring. When having two or more hydroxy groups, two hydroxy groups are preferably bonded at the m-position and the p-position, respectively.

Examples of the structural unit (a2-A) include structural units derived from the monomers mentioned in JP 2010-204634 A and JP 2012-12577 A.

Examples of the structural unit (a2-A) include structural units represented by formula (a2-2-1) to formula (a2-2-24), and a structural unit in which a methyl group corresponding to R^a50 in the structural unit (a2-A) is substituted with a hydrogen atom, a halogen atom, a haloalkyl group or other alkyl groups in structural units represented by formula (a2-2-1) to formula (a2-2-24). The structural unit (a2-A) is preferably structural units represented by formula (a2-2-1) to formula (a2-2-4), a structural unit represented by formula (a2-2-6), a structural unit represented by formula (a2-2-8), structural units represented by formula (a2-2-12) to formula (a2-2-18), and a structural unit in which a methyl group corresponding to R^a50 in the structural unit (a2-A) is substituted with a hydrogen atom in structural units represented by formula (a2-2-1) to formula (a2-2-4), a structural unit represented by formula (a2-2-6), a structural unit represented by formula (a2-2-8) and structural units represented by formula (a2-2-12) to formula (a2-2-18), more preferably a structural unit represented by formula (a2-2-3), a structural unit represented by formula (a2-2-4), a structural unit represented by formula (a2-2-8), structural units represented by formula (a2-2-12) to formula (a2-2-14), a structural unit represented by formula (a2-2-18), and a structural unit in which a methyl group corresponding to R^a50 in the structural unit (a2-A) is substituted with a hydrogen atom in a structural unit represented by formula (a2-2-3), a structural unit represented by formula (a2-2-4), a structural unit represented by formula (a2-2-8), structural units represented by formula (a2-2-12) to formula (a2-2-14) and a structural unit represented by formula (a2-2-18), and still more preferably a structural unit represented by formula (a2-2-3), a structural unit represented by formula (a2-2-4), a structural unit represented by formula (a2-2-8), and a structural unit in which a methyl group corresponding to R^a50 in the structural unit (a2-A) is substituted with a hydrogen atom in a structural unit represented by formula (a2-2-3), a structural unit represented by formula (a2-2-4) and a structural unit represented by formula (a2-2-8).

When the structural unit (a2-A) is included in the resin (A) or the like, the content of the structural unit (a2-A) is preferably 5 mol % or more, more preferably 10 mol % or more, still more preferably 15 mol % or more, and yet more preferably 20 mol % or more, based on all structural units. The content is also preferably 80 mol % or less, more preferably 70 mol % or less, and still more preferably 65 mol % or less, based on all structural units. Specifically, the content is preferably 5 to 80 mol %, more preferably 10 to 70 mol %, still more preferably 15 to 65 mol %, and yet more preferably 20 to 65 mol %, based on all structural units.

The structural unit (a2-A) can be included in the resin (A) or the like by polymerizing, for example, with a structural unit (a1-4) and treating with an acid such as p-toluenesulfonic acid. The structural unit (a2-A) can also be included in the resin (A) or the like by polymerizing with acetoxystyrene and treating with an alkali such as tetramethylammonium hydroxide.

Examples of the structural unit (a2-A) also include a structural unit represented by the following formula (a2-A1) (hereinafter sometimes referred to as “structural unit (a2-A1)”) and a structural unit represented by the following formula (a2-A2) (hereinafter sometimes referred to as “structural unit (a2-A2)”):

wherein, in formula (a2-A1) and formula (a2-A2),

R^a50 and A^a50 are respectively the same as defined in formula (a2),

mb1 represents an integer of 0 to 4,

R^a52 represents a halogen atom,

R^a53 represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, an alkoxyalkoxy group having 2 to 12 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, an acryloyloxy group or a methacryloyloxy group, and

mb2 and mb3 each independently represent an integer of 0 to 4, and when mb2 is 2 or more, a plurality of R^a52 may be the same or different from each other, and when mb3 is 2 or more, a plurality of R^a53 may be the same or different from each other and satisfies 1≤mb2+mb34.

Examples of the halogen atom as for R^a52 include the same halogen atoms as in the substituent of the cyclic hydrocarbon group as for W^a30 and R^a51. The halogen atom as for R^a52 is preferably a fluorine atom or an iodine atom.

Examples of the alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms, the alkoxyalkyl group having 2 to 12 carbon atoms, the alkoxyalkoxy group having 2 to 12 carbon atoms, the alkylcarbonyl group having 2 to 4 carbon atoms, the alkylcarbonyloxy group having 2 to 4 carbon atoms, the acryloyloxy group or the methacryloyloxy group as for R^a53 include the same as the alkyl group, the alkoxy group, the alkoxyalkyl group, the alkoxyalkoxy group, the alkylcarbonyl group, the alkylcarbonyloxy group, the acryloyloxy group or the methacryloyloxy group in the substituent of the cyclic hydrocarbon group as for W^a30 and R^a51, and a methyl group, a methoxy group, an ethoxy group, an ethoxyethoxy group or an ethoxymethoxy group is more preferable, and a methoxy group or an ethoxyethoxy group is still more preferable.

mb1 is preferably an integer of 0 to 3, more preferably an integer of 0 to 2, and still more preferably 0 or 1.

mb2 is preferably an integer of 0 to 3, more preferably an integer of 1 to 3, and still more preferably 1 or 2.

mb3 is preferably an integer of 0 to 3, more preferably an integer of 0 to 2, and still more preferably 0 or 1.

Examples of the structural unit having an alcoholic hydroxy group in the structural unit (a2) include a structural unit represented by formula (a2-1) (hereinafter sometimes referred to as “structural unit (a2-1)”):

wherein, in formula (a2-1),

L^a3 represents —O— or *—O—(CH₂)_k2—CO—O—,

k2 represents an integer of 1 to 7, and * represents a bonding site to —CO—,

R^a14 represents a hydrogen atom or a methyl group,

R^a15 and R^a16 each independently represent a hydrogen atom, a methyl group or a hydroxy group, and

o1 represents an integer of 0 to 10.

In formula (a2-1), L^a3 is preferably —O— or —O—(CH₂)_f1—CO—O— (f1 represents an integer of 1 to 4), and more preferably —O—,

R^a14 is preferably a methyl group,

R^a15 is preferably a hydrogen atom,

R^a16 is preferably a hydrogen atom or a hydroxy group, and

o1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

The structural unit (a2-1) includes, for example, structural units derived from the monomers mentioned in JP 2010-204646 A. A structural unit represented by any one of formula (a2-1-1) to formula (a2-1-6) is preferable, a structural unit represented by any one of formula (a2-1-1) to formula (a2-1-4) is more preferable, and a structural unit represented by formula (a2-1-1) or formula (a2-1-3) is still more preferable.

When the resin (A) or the like includes the structural unit (a2-1), the content is usually 1 mol % or more, and preferably 2 mol % or more, based on all structural units of the resin (A) or the like. The content is also usually 45 mol % or less, preferably 40 mol % or less, more preferably 35 mol % or less, still more preferably 20 mol % or less, and yet more preferably 10 mol % or less, based on all structural units of the resin (A) or the like. Specifically, the content is usually 1 to 45 mol %, preferably 1 to 40 mol %, more preferably 1 to 35 mol %, still more preferably 1 to 20 mol %, and yet more preferably 1 to 10 mol %, based on all structural units of the resin (A) or the like.

Examples of the structural unit having an alcoholic hydroxy group in the structural unit (a2) include a structural unit represented by formula (a2-B) (hereinafter sometimes referred to as “structural unit (a2-B)”):

wherein, in formula (a2-B),

R^a50 and A^a50 are the same as defined in formula (a2), respectively,

R^a54 and R^a55 each independently represent an alkyl fluoride group having 1 to 4 carbon atoms,

L^a51 represents a single bond or an alkanediyl group having 1 to 3 carbon atoms, and the alkanediyl group may be substituted with a fluorine atom,

R^a56 represents a halogen atom, a hydroxy group, a haloalkyl group having 1 to 4 carbon atoms or an alkyl group having 1 to 12 carbon atoms, and —CH₂— included in the alkyl group may be replaced by —O— or —CO—,

mb4 represents an integer of 1 to 3, and when mb4 is 2 or more, a plurality of R^a54, R^a55 and L^a5 each may be the same or different from each other, and

mb5 represents an integer of 0 to 4, and when mb5 is 2 or more, a plurality of R^a56 may be the same or different from each other, in which 1≤mb4+mb55.

Examples of the alkyl fluoride group having 1 to 4 carbon atoms as for R^a54 and R^a55 include a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a 3,3,3-trifluoropropyl group, a 4,4,4-trifluorobutyl group and the like. R^a54 and R^a55 are preferably a trifluoromethyl group.

Examples of the alkanediyl group having 1 to 3 carbon atoms as for L^a51 include a methylene group, an ethane-1,1-diyl group, a propane-1,1-diyl group, a propane-2,2-diyl group and the like. L^a51 is preferably a single bond or a methylene group.

Examples of the halogen atom as for R^a56 include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

The haloalkyl group having 1 to 4 carbon atoms in R^a56 represents an alkyl group having 1 to 4 carbon atoms which has a halogen atom, and examples thereof include a chloromethyl group, a bromomethyl group, a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a perfluorobutyl and the like.

Examples of the alkyl group having 1 to 12 carbon atoms in R^a56 include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group and a nonyl group. The number of carbon atoms of the alkyl group is preferably 1 to 9, more preferably 1 to 6, and still more preferably 1 to 4.

When —CH₂— included in the alkyl group represented by R^a55 is replaced by —O— or —CO—, the number of carbon atoms before replacement is taken as the total number of the alkyl group. R^a56 may also have a hydroxy group (a group in which —CH₂— included in the methyl group is replaced by —O—), a carboxyl group (a group in which —CH₂—CH₂— included in the ethyl group is replaced by —O—CO—), an alkoxy group having 1 to 11 carbon atoms (a group in which —CH₂— included in the alkyl group having 2 to 12 carbon atoms is replaced by —O—), an alkoxycarbonyl group having 2 to 11 carbon atoms (a group in which —CH₂—CH₂— included in the alkyl group having 3 to 12 carbon atoms is replaced by —O—CO—), an alkylcarbonyl group having 2 to 12 carbon atoms (a group in which —CH₂— included in the alkyl group having 2 to 12 carbon atoms is replaced by —CO—) and an alkylcarbonyloxy group having 2 to 11 carbon atoms (a group in which —CH₂—CH₂— included in the alkyl group having 3 to 12 carbon atoms is replaced by —CO—O—).

Particularly, R^a56 is preferably a halogen atom, a haloalkyl group having 1 to 4 carbon atoms or an alkyl group having 1 to 12 carbon atoms (—CH₂— included in the alkyl group may be replaced by —O— or —CO—).

mb4 is preferably 1 or 2, more preferably 1, and still more preferably mb4 is 1 and the group in parentheses is bonded at the para-position.

mb5 is preferably an integer of 0 to 2, more preferably 0 or 1, and still more preferably 0.

The structural unit (a2-B) is more preferably a structural unit represented by the following formula (a2-B1) (hereinafter sometimes referred to as “structural unit (a2-B1)”):

wherein, in formula (a2-B1),

R^a57 represents a hydrogen atom or a methyl group,

A^a53 represents a single bond or *—CO—O—, and * represents a bonding site to carbon atoms to which —R^a57 is bonded, and

R^a56, mb4 and mb5 are the same as defined in formula (a2-B), respectively.

In formula (a2-B1), R^a57 is preferably a hydrogen atom.

A^a53 is preferably a single bond.

Examples of the structural unit (a2-B) include structural units mentioned below.

It is possible to exemplify structural units in which the hydrogen atom corresponding to R^a57 is substituted with a methyl group in structural units represented by formula (a2-B-1) to formula (a2-B-8), and structural units in which the methyl group corresponding to R^a57 is substituted with a hydrogen atom in structural units represented by formula (a2-B-9) to formula (a2-B-16) as specific examples of the structural unit (a2-B). Of these, structural units represented by formula (a2-B-1) to formula (a2-B-8) are preferable, structural units represented by formula (a2-B-1) to formula (a2-B-4) are more preferable, and a structural unit represented by formula (a2-B-1) is still more preferable.

When the resin (A) or the like includes the structural unit (a2-B), the content is preferably 3 mol % or more, more preferably 5 mol % or more, and still more preferably 10 mol % or more, based on all structural units of the resin (A) or the like. The content is also preferably 80 mol % or less, more preferably 75 mol % or less, still more preferably 70 mol % or less, and yet more preferably 65 mol % or less, based on all structural units of the resin (A) or the like. Specifically, the content is preferably 3 to 80 mol %, more preferably 5 to 75 mol %, still more preferably 10 to 70 mol %, and yet more preferably 10 to 65 mol %, based on all structural units of the resin (A) or the like.

<Structural Unit (a3)>

The lactone ring possessed by the structural unit (a3) may be a monocyclic ring such as a β-propiolactone ring, a γ-butyrolactone ring or a 5-valerolactone ring, or a condensed ring of a monocyclic lactone ring and the other ring. Preferably, a γ-butyrolactone ring, an adamantanelactone ring or a bridged ring including a γ-butyrolactone ring structure (e.g., a structural unit represented by the following formula (a3-2)) is exemplified.

The structural unit (a3) is preferably a structural unit represented by formula (a3-1), formula (a3-2), formula (a3-3) or formula (a3-4). These structural units may be included alone, or two or more structural units may be included:

wherein, in formula (a3-1), formula (a3-2), formula (a3-3) and formula (a3-4),

L^a4, L^a5 and L^a6 each independently represent —O— or a group represented by *—O—(CH₂)_k3—CO—O— (k3 represents an integer of 1 to 7),

L^a7 represents —O—, *—O-L^a8-O—, *—O-L^a8-CO—O—, *—O-L^a8-CO—O-L^a9-CO—O— or *—O-L^a8-O—CO-L^a9-_,

L^a8 and L^a9 each independently represent an alkanediyl group having 1 to 6 carbon atoms,

* represents a bonding site to a carbonyl group,

R^a18, R^a19, R^a20 and R^a24 each independently represent an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, a hydrogen atom or a halogen atom,

X^a3 represents —CH₂— or an oxygen atom, R^a21 represents an aliphatic hydrocarbon group having 1 to 4 carbon atoms,

R^a22, R^a23 and R^a25 each independently represent a carboxy group, a cyano group or an aliphatic hydrocarbon group having 1 to 4 carbon atoms,

p1 represents an integer of 0 to 5,

q1 represents an integer of 0 to 3,

r1 represents an integer of 0 to 3,

w1 represents an integer of 0 to 8, and when p1, q1, r1 and/or w1 is/are 2 or more, a plurality of R^a21, R^a22, R^a23 and/or R^a25 may be the same or different from each other.

Examples of the aliphatic hydrocarbon group in R^a21, R^a22, R^a23 and R^a25 include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group and a tert-butyl group.

Examples of the halogen atom in R^a18, R^a19, R^a20 and R^a24 include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

Examples of the alkyl group in R^a18, R^a19, R^a20 and R^a24 include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group and a hexyl group, and the alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, and more preferably a methyl group or an ethyl group.

Examples of the alkyl group having a halogen atom in R^a18, R^a19, R^a20 and R^a24 include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butyl group, a perfluorotert-butyl group, a perfluoropentyl group, a perfluorohexyl group, a trichloromethyl group, a tribromomethyl group, a triiodomethyl group and the like.

Examples of the alkanediyl group in L^a8 and L^a9 include a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group.

In formula (a3-1) to formula (a3-3), preferably, L^a4 to L^a6 are each independently —O— or a group in which k3 is an integer of 1 to 4 in *—O—(CH₂)_k3—CO—O—, more preferably —O— and *—O—CH₂—CO—O—, and still more preferably an oxygen atom,

R^a18 to R^a21 are preferably a methyl group,

preferably, R^a22 and R^a23 are each independently a carboxy group, a cyano group or a methyl group, and

preferably, p1, q1 and r1 are each independently an integer of 0 to 2, and more preferably 0 or 1.

In formula (a3-4), R^a24 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group or an ethyl group, and still more preferably a hydrogen atom or a methyl group,

R^a25 is preferably a carboxy group, a cyano group or a methyl group,

L^a7 is preferably —O— or *—O-L^a8-CO—O—, and more preferably —O—, —O—CH₂—CO—O— or —O—C₂H₄—CO—O—, and

w1 is preferably an integer of 0 to 2, and more preferably 0 or 1.

Particularly, formula (a3-4) is preferably formula (a3-4)′:

wherein R^a24 and L^a7 are the same as defined above.

Examples of the structural unit (a3) include structural units derived from the monomers mentioned in JP 2010-204646 A, the monomers mentioned in JP 2000-122294 A and the monomers mentioned in JP 2012-41274 A. The structural unit (a3) is preferably a structural unit represented by any one of formula (a3-1-1), formula (a3-1-2), formula (a3-2-1), formula (a3-2-2), formula (a3-3-1), formula (a3-3-2) and formula (a3-4-1) to formula (a3-4-12), and structural units in which methyl groups corresponding to R^a18, R^a19, R^a2 0 and R^a24 in formula (a3-1) to formula (a3-4) are substituted with hydrogen atoms in the above structural units.

When the resin (A) or the like includes the structural unit (a3), the total content is usually 1 mol % or more, preferably 3 mol % or more, more preferably 5 mol % or more, and still more preferably 10 mol % or more, based on all structural units of the resin (A) or the like. The total content is also usually 70 mol % or less, preferably 65 mol % or less, and more preferably 60 mol % or less, based on all structural units of the resin (A) or the like. Specifically, the total content is usually 1 to 70 mol %, preferably 3 to 65 mol %, and more preferably 5 to 60 mol %, based on all structural units of the resin (A) or the like.

Each content of the structural unit (a3-1), the structural unit (a3-2), the structural unit (a3-3) or the structural unit (a3-4) is preferably 1 mol % or more, more preferably 3 mol % or more, and still more preferably 5 mol % or more, based on all structural units of the resin (A) or the like. Each content of the structural unit (a3-1), the structural unit (a3-2), the structural unit (a3-3) or the structural unit (a3-4) is also preferably 60 mol % or less, more preferably 55 mol % or less, and still more preferably 50 mol % or less, based on all structural units of the resin (A) or the like. Specifically, each content of the structural unit (a3-1), the structural unit (a3-2), the structural unit (a3-3) or the structural unit (a3-4) is preferably 1 to 60 mol %, more preferably 3 to 55 mol %, and still more preferably 5 to 50 mol %.

<Structural Unit (a4)>

Examples of the structural unit (a4) include the following structural unit:

wherein, in formula (a4),

R⁴¹ represents a hydrogen atom or a methyl group, and

R⁴² represents a saturated hydrocarbon group having 1 to 24 carbon atoms which has a halogen atom, and —CH₂— included in the saturated hydrocarbon group may be replaced by —O— or —CO—.

Examples of the chain saturated hydrocarbon group represented by R⁴² include a chain saturated hydrocarbon group and a monocyclic or polycyclic alicyclic saturated hydrocarbon group, and groups formed by combining these groups.

Examples of the chain saturated hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a decyl group, a dodecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group and an octadecyl group.

Examples of the monocyclic or polycyclic alicyclic saturated hydrocarbon group include cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group and a cyclooctyl group; and polycyclic alicyclic saturated hydrocarbon groups such as a decahydronaphthyl group, an adamantyl group, a norbornyl group, and the following groups (* represents a bonding site).

Examples of the group formed by combination include groups formed by combining one or more alkyl groups or one or more alkanediyl groups with one or more alicyclic saturated hydrocarbon groups, and include an alkanediyl group-alicyclic saturated hydrocarbon group, an alicyclic saturated hydrocarbon group-alkyl group, an alkanediyl group-alicyclic saturated hydrocarbon group-alkyl group and the like.

Examples of the structural unit (a4) include a structural unit represented by formula (a4-0), a structural unit represented by formula (a4-1), and a structural unit represented by formula (a4-4):

wherein, in formula (a4-0),

R⁵⁴ represents a hydrogen atom or a methyl group,

L^4a represents a single bond or an alkanediyl group having 1 to 4 carbon atoms,

L^3a represents a perfluoroalkanediyl group having 1 to 8 carbon atoms or a perfluorocycloalkanediyl group having 3 to 12 carbon atoms, and

R⁶⁴ represents a hydrogen atom or a fluorine atom.

Examples of the alkanediyl group in L^4a include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group and a butane-1,4-diyl group; and branched alkanediyl groups such as an ethane-1,1-diyl group, a propane-1,2-diyl group, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group and a 2-methylpropane-1,2-diyl group.

Examples of the perfluoroalkanediyl group in L³a include a difluoromethylene group, a perfluoroethylene group, a perfluoroethylfluoromethylene group, a perfluoropropane-1,3-diyl group, a perfluoropropane-1,2-diyl group, a perfluoropropane-2,2-diyl group, a perfluorobutane-1,4-diyl group, a perfluorobutane-2,2-diyl group, a perfluorobutane-1,2-diyl group, a perfluoropentane-1,5-diyl group, a perfluoropentane-2,2-diyl group, a perfluoropentane-3,3-diyl group, a perfluorohexane-1,6-diyl group, a perfluorohexane-2,2-diyl group, a perfluorohexane-3,3-diyl group, a perfluoroheptane-1,7-diyl group, a perfluoroheptane-2,2-diyl group, a perfluoroheptane-3,4-diyl group, a perfluoroheptane-4,4-diyl group, a perfluorooctane-1,8-diyl group, a perfluorooctane-2,2-diyl group, a perfluorooctane-3,3-diyl group, a perfluorooctane-4,4-diyl group and the like.

Examples of the perfluorocycloalkanediyl group in L³a include a perfluorocyclohexanediyl group, a perfluorocyclopentanediyl group, a perfluorocycloheptanediyl group, a perfluoroadamantanediyl group and the like.

L^4a is preferably a single bond, a methylene group or an ethylene group, and more preferably a single bond or a methylene group.

L^3a is preferably a perfluoroalkanediyl group having 1 to 6 carbon atoms, and more preferably a perfluoroalkanediyl group having 1 to 3 carbon atoms.

Examples of the structural unit (a4-0) include the following structural units, and structural units in which a methyl group corresponding to R⁵⁴ in the structural unit (a4-0) in the following structural units is substituted with a hydrogen atom:

wherein, in formula (a4-1),

R^a41 represents a hydrogen atom or a methyl group,

R^a42 represents a saturated hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, and —CH₂— included in the saturated hydrocarbon group may be replaced by —O— or —CO—,

A^a41 represents an alkanediyl group having 1 to 6 carbon atoms which may have a substituent or a group represented by formula (a-g1), in which at least one of A^a41 and R^a42 has, as a substituent, a halogen atom (preferably a fluorine atom):

[in which, in formula (a-g1),

s represents 0 or 1,

A^a42 and A^a44 each independently represent a divalent saturated hydrocarbon group having 1 to 5 carbon atoms which may have a substituent,

A^a43 represents a single bond or a divalent saturated hydrocarbon group having 1 to 5 carbon atoms which may have a substituent,

X^a41 and X^a42 each independently represent —O—, —CO—, —CO—O— or —O—CO—, in which the total number of carbon atoms of A^a42,

A^a43, A^a44, X^a41 and X^a42 is 7 or less], and

* represents a bonding site and * at the right side represents a bonding site to —O—CO—R^a42.

Examples of the saturated hydrocarbon group in R^a42 include a chain saturated hydrocarbon group and a monocyclic or polycyclic alicyclic saturated hydrocarbon group, and groups formed by combining these groups.

Examples of the chain saturated hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a decyl group, a dodecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group and an octadecyl group.

Examples of the monocyclic or polycyclic alicyclic saturated hydrocarbon group include cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group and a cyclooctyl group; and polycyclic alicyclic saturated hydrocarbon groups such as a decahydronaphthyl group, an adamantyl group, a norbornyl group, and the following groups (* represents a bonding site).

Examples of the group formed by combination include groups formed by combining one or more alkyl groups or one or more alkanediyl groups with one or more alicyclic saturated hydrocarbon groups, for example, an -alkanediyl group-alicyclic saturated hydrocarbon group, an -alicyclic saturated hydrocarbon group-alkyl group, an -alkanediyl group-alicyclic saturated hydrocarbon group-alkyl group and the like.

Examples of the substituent possessed by R^a42 include at least one selected from the group consisting of a halogen atom and the group consisting of the group represented by formula (a-g3). Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and a fluorine atom is preferable:

*—X^a43-A^a45  (a-g3)

wherein, in formula (a-g3),

X^a43 represents an oxygen atom, a carbonyl group, *—O—CO— or *—CO—O—,

A^a45 represents a saturated hydrocarbon group having 1 to 17 carbon atoms which may have a halogen atom, and

* represents a bonding site to R^a42.

In R^a42—X^a43-A^a45, when R^a42 has no halogen atom, A^a45 represents a saturated hydrocarbon group having 1 to 17 carbon atoms having at least one halogen atom.

Examples of the saturated hydrocarbon group in A^a45 include alkyl groups such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a decyl group, a dodecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group and an octadecyl group; monocyclic alicyclic hydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group and a cyclooctyl group; and polycyclic alicyclic hydrocarbon groups such as a decahydronaphthyl group, an adamantyl group, a norbornyl group and the following groups (* represents a bonding site).

Examples of the group formed by combination include groups obtained by combining one or more alkyl groups or one or more alkanediyl groups with one or more alicyclic hydrocarbon groups, for example, an -alkanediyl group-alicyclic hydrocarbon group, an -alicyclic hydrocarbon group-alkyl group, an -alkanediyl group-alicyclic hydrocarbon group-alkyl group and the like.

R^a42 is preferably a saturated hydrocarbon group which may have a halogen atom, and more preferably an alkyl group having a halogen atom and/or a saturated hydrocarbon group having a group represented by formula (a-g3).

When R^a42 is a saturated hydrocarbon group having a halogen atom, a saturated hydrocarbon group having a fluorine atom is preferable, a perfluoroalkyl group or a perfluorocycloalkyl group is more preferable, a perfluoroalkyl group having 1 to 6 carbon atoms is still more preferable, and a perfluoroalkyl group having 1 to 3 carbon atoms is particularly preferable. Examples of the perfluoroalkyl group include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group, a perfluoroheptyl group and a perfluorooctyl group. Examples of the perfluorocycloalkyl group include a perfluorocyclohexyl group and the like.

When R^a42 is a saturated hydrocarbon group having a group represented by formula (a-g3), the total number of carbon atoms of R^a42 is preferably 15 or less, and more preferably 12 or less, including the number of carbon atoms included in the group represented by formula (a-g3). When having the group represented by formula (a-g3) as the substituent, the number thereof is preferably 1.

When R^a42 is a saturated hydrocarbon group having the group represented by formula (a-g3), R^a42 is still more preferably a group represented by formula (a-g2):

*-A^a46-X^a44-A^a47  (a-g2)

wherein, in formula (a-g2),

A^a46 represents a divalent saturated hydrocarbon group having 1 to 17 carbon atoms which may have a halogen atom,

X^a44 represents **—O—CO— or **—CO—O— (** represents a bonding site to A^a46),

A^a47 represents a saturated hydrocarbon group having 1 to 17 carbon atoms which may have a halogen atom, the total number of carbon atoms of A^a46, A^a47 and

X^a44 is 18 or less, and at least one of A^a46 and A^a47 has at least one halogen atom, and

* represents a bonding site to a carbonyl group.

The number of carbon atoms of the saturated hydrocarbon group as for A^a46 is preferably 1 to 6, and more preferably 1 to 3.

The number of carbon atoms of the saturated hydrocarbon group as for A^a47 is preferably 4 to 15, and more preferably 5 to 12, and A^a47 is still more preferably a cyclohexyl group or an adamantyl group.

Preferred structures of the group represented by formula (a-g2) are the following structures (* represents a bonding site to a carbonyl group).

Examples of the alkanediyl group in A^a41 include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group and a hexane-1,6-diyl group; and branched alkanediyl groups such as a propane-1,2-diyl group, a butane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a 1-methylbutane-1,4-diyl group and a 2-methylbutane-1,4-diyl group.

Examples of the substituent in the alkanediyl group represented by A^a41 include a hydroxy group and an alkoxy group having 1 to 6 carbon atoms.

A^a41 is preferably an alkanediyl group having 1 to 4 carbon atoms, more preferably an alkanediyl group having 2 to 4 carbon atoms, and still more preferably an ethylene group.

Examples of the divalent saturated hydrocarbon group represented by A^a42, A^a43 and A^a44 in the group represented by formula (a-g1) include a linear or branched alkanediyl group and a monocyclic or polycyclic divalent alicyclic saturated hydrocarbon group, and divalent saturated hydrocarbon groups formed by combining an alkanediyl group and a divalent alicyclic saturated hydrocarbon group. Specific examples thereof include a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a 1-methylpropane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group and the like.

Examples of the substituent of the divalent saturated hydrocarbon group represented by A^a42, A^a43 and A^a44 include a hydroxy group and an alkoxy group having 1 to 6 carbon atoms.

s is preferably 0.

In the group represented by formula (a-g1), examples of the group in which X^a42 is —O—, —CO—, —CO—O— or —O—CO-include the following groups. In the following exemplification, * and ** each represent a bonding site, and ** represents a bonding site to —O—CO—R^a42.

Examples of the structural unit represented by formula (a4-1) include the following structural units, and structural units in which a methyl group corresponding to A^a41 in the structural unit represented by formula (a4-1) in the following structural units is substituted with a hydrogen atom.

Examples of the structural unit represented by formula (a4-1) include a structural unit represented by formula (a4-2) and a structural unit represented by formula (a4-3):

wherein, in formula (a4-2),

R^f3 represents a hydrogen atom or a methyl group,

L⁴⁴ represents an alkanediyl group having 1 to 6 carbon atoms, and —CH₂— included in the alkanediyl group may be replaced by —O— or —CO—,

R^f6 represents a saturated hydrocarbon group having 1 to 20 carbon atoms having a fluorine atom, and

the upper limit of the total number of carbon atoms as for L⁴⁴ and R^f6 is 21.

Examples of the alkanediyl group having 1 to 6 carbon atoms as for L⁴⁴ include the same groups as mentioned as for A^a41.

Examples of the saturated hydrocarbon group as for R^f6 include the same groups as mentioned as for R⁴².

The alkanediyl group in L⁴⁴ is preferably an alkanediyl group having 2 to 4 carbon atoms, and more preferably an ethylene group.

The structural unit represented by formula (a4-2) includes, for example, structural units represented by formula (a4-1-1) to formula (a4-1-11). A structural unit in which a methyl group corresponding to R^f5 in the structural unit (a4-2) is substituted with a hydrogen atom is also exemplified as the structural unit represented by formula (a4-2).

wherein, in formula (a4-3),

R^f7 represents a hydrogen atom or a methyl group,

L⁵ represents an alkanediyl group having 1 to 6 carbon atoms, A^f13 represents a divalent saturated hydrocarbon group having 1 to 18 carbon atoms which may have a fluorine atom,

X^f12 represents *—O—CO— or *—CO—O— (* represents a bonding site to A^f13),

A^f14 represents a saturated hydrocarbon group having 1 to 17 carbon atoms which may have a fluorine atom, and

at least one of A^f13 and A^f14 has a fluorine atom, and the upper limit of the total number of carbon atoms of L³, A^f13 and A^f14 is 20.

Examples of the alkanediyl group in L³ include those which are the same as mentioned as for the alkanediyl group as for A^a41.

The divalent saturated hydrocarbon group which may have a fluorine atom in A^f13 is preferably a divalent chain saturated hydrocarbon group which may have a fluorine atom and a divalent alicyclic saturated hydrocarbon group which may have a fluorine atom, and more preferably a perfluoroalkanediyl group.

Examples of the divalent chain saturated hydrocarbon group which may have a fluorine atom include alkanediyl groups such as a methylene group, an ethylene group, a propanediyl group, a butanediyl group and a pentanediyl group; and perfluoroalkanediyl groups such as a difluoromethylene group, a perfluoroethylene group, a perfluoropropanediyl group, a perfluorobutanediyl group and a perfluoropentanediyl group.

The divalent alicyclic saturated hydrocarbon group which may have a fluorine atom may be either monocyclic or polycyclic. Examples of the monocyclic group include a cyclohexanediyl group and a perfluorocyclohexanediyl group. Examples of the polycyclic group include an adamantanediyl group, a norbornanediyl group, a perfluoroadamantanediyl group and the like.

Examples of the saturated hydrocarbon group and the saturated hydrocarbon group which may have a fluorine atom as for A^f14 include the same groups as mentioned as for R^a42. Of these groups, preferred are fluorinated alkyl groups such as a trifluoromethyl group, a difluoromethyl group, a methyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a propyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, a perfluoropentyl group, a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, a hexyl group, a perfluorohexyl group, a heptyl group, a perfluoroheptyl group, an octyl group and a perfluorooctyl group; a cyclopropylmethyl group, a cyclopropyl group, a cyclobutylmethyl group, a cyclopentyl group, a cyclohexyl group, a perfluorocyclohexyl group, an adamantyl group, an adamantylmethyl group, an adamantyldimethyl group, a norbornyl group, a norbornylmethyl group, a perfluoroadamantyl group, a perfluoroadamantylmethyl group and the like.

In formula (a4-3), L⁵ is preferably an ethylene group. The divalent saturated hydrocarbon group as for A^f13 is preferably a group including a divalent chain saturated hydrocarbon group having 1 to 6 carbon atoms and a divalent alicyclic saturated hydrocarbon group having 3 to 12 carbon atoms, and more preferably a divalent chain saturated hydrocarbon group having 2 to 3 carbon atoms.

The saturated hydrocarbon group as for A^f14 is preferably a group which has a chain saturated hydrocarbon group having 3 to 12 carbon atoms and an alicyclic saturated hydrocarbon group having 3 to 12 carbon atoms, and more preferably a group which has a chain saturated hydrocarbon group having 3 to 10 carbon atoms and an alicyclic saturated hydrocarbon group having 3 to 10 carbon atoms. Of these groups, A^fl4 is preferably a group which has an alicyclic saturated hydrocarbon group having 3 to 12 carbon atoms, and more preferably a cyclopropylmethyl group, a cyclopentyl group, a cyclohexyl group, a norbornyl group and an adamantyl group.

The structural unit represented by formula (a4-3) includes, for example, structural units represented by formula (a4-1′-1) to formula (a4-1′-11). A structural unit in which a methyl group corresponding to R^f7 in the structural unit (a4-3) is substituted with a hydrogen atom is also exemplified as the structural unit represented by formula (a4-3).

It is also possible to exemplify, as the structural unit (a4), a structural unit represented by formula (a4-4):

wherein, in formula (a4-4),

R^f21 represents a hydrogen atom or a methyl group,

A^f21 represents —(CH₂)_j1—, —(CH₂)_j2—O—(CH₂)_j3— or —(CH₂)_j4—CO—O— (CH₂)_j5—, j1 to j5 each independently represent an integer of 1 to 6, and

R^f22 represents a saturated hydrocarbon group having 1 to 10 carbon atoms having a fluorine atom.

Examples of the saturated hydrocarbon group of R^f22 include those which are the same as the saturated hydrocarbon group represented by R^a42. R^f22 is preferably an alkyl group having 1 to 10 carbon atoms which has a fluorine atom or an alicyclic hydrocarbon group having 1 to 10 carbon atoms which has a fluorine atom, more preferably an alkyl group having 1 to 10 carbon atoms which has a fluorine atom, and still more preferably an alkyl group having 1 to 6 carbon atoms which has a fluorine atom.

In formula (a4-4), A^f21 is preferably —(CH₂)_j1—, more preferably an ethylene group or a methylene group, and still more preferably a methylene group.

The structural unit represented by formula (a4-4) includes, for example, the following structural units and structural units in which a methyl group corresponding to

R^f21 in the structural unit (a4-4) is substituted with a hydrogen atom in structural units represented by the following formulas.

When the resin (A) or the like includes the structural unit (a4), the content is preferably 1 to 20 mol %, more preferably 2 to 15 mol %, and still more preferably 3 to 10 mol %, based on all structural units of the resin (A) or the like.

<Structural Unit (a5)>

Examples of a non-leaving hydrocarbon group possessed by the structural unit (a5) include groups having a linear, branched or cyclic hydrocarbon group. Of these, the structural unit (a5) is preferably a group having an alicyclic hydrocarbon group.

The structural unit (a5) includes, for example, a structural unit represented by formula (a5-1):

wherein, in formula (a5-1),

R⁵¹ represents a hydrogen atom or a methyl group,

R⁵² represents an alicyclic hydrocarbon group having 3 to 18 carbon atoms, and a hydrogen atom included in the alicyclic hydrocarbon group may be substituted with an aliphatic hydrocarbon group having 1 to 8 carbon atoms, and

L⁵⁵ represents a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and —CH₂— included in the saturated hydrocarbon group may be replaced by —O— or —CO—.

The alicyclic hydrocarbon group in R⁵² may be either monocyclic or polycyclic. The monocyclic alicyclic hydrocarbon group includes, for example, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group and a cyclohexyl group. The polycyclic alicyclic hydrocarbon group includes, for example, an adamantyl group and a norbornyl group.

The aliphatic hydrocarbon group having 1 to 8 carbon atoms includes, for example, alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group and a 2-ethylhexyl group.

Examples of the alicyclic hydrocarbon group having a substituent includes a 3-methyladamantyl group and the like.

R⁵² is preferably an unsubstituted alicyclic hydrocarbon group having 3 to 18 carbon atoms, and more preferably an adamantyl group, a norbornyl group or a cyclohexyl group.

Examples of the divalent saturated hydrocarbon group in L⁵⁵ include a divalent chain saturated hydrocarbon group and a divalent alicyclic saturated hydrocarbon group, and a divalent chain saturated hydrocarbon group is preferable.

The divalent chain saturated hydrocarbon group includes, for example, alkanediyl groups such as a methylene group, an ethylene group, a propanediyl group, a butanediyl group and a pentanediyl group.

The divalent alicyclic saturated hydrocarbon group may be either monocyclic or polycyclic. Examples of the monocyclic alicyclic saturated hydrocarbon group include cycloalkanediyl groups such as a cyclopentanediyl group and a cyclohexanediyl group. Examples of the polycyclic divalent alicyclic saturated hydrocarbon group include an adamantanediyl group and a norbornanediyl group.

The group in which —CH₂— included in the divalent saturated hydrocarbon group represented by L⁵⁵ is replaced by —O— or —CO— includes, for example, groups represented by formula (L1-1) to formula (L1-4). In the following formulas, * and ** each represent a bonding site, and * represents a bonding site to an oxygen atom:

wherein, in formula (L1-1),

X^x1 represents *—O—CO— or *—CO—O— (* represents a bonding site to L^x1),

L^x1 represents a divalent aliphatic saturated hydrocarbon group having 1 to 16 carbon atoms,

L^x2 represents a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 15 carbon atoms, and

the total number of carbon atoms of L^x1 and L^x2 is 16 or less.

In formula (L1-2),

L^x3 represents a divalent aliphatic saturated hydrocarbon group having 1 to 17 carbon atoms,

L^x4 represents a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 16 carbon atoms, and

the total number of carbon atoms of L^x3 and L^x4 is 17 or less.

In formula (L1-3),

L^x5 represents a divalent aliphatic saturated hydrocarbon group having 1 to 15 carbon atoms,

L^x6 and L^x7 each independently represent a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 14 carbon atoms, and

the total number of carbon atoms of L^x5, L^x6 and L^x7 is 15 or less.

In formula (L1-4), L^x8 and L^x9 represent a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 12 carbon atoms,

W^x1 represents a divalent alicyclic saturated hydrocarbon group having 3 to 15 carbon atoms, and

the total number of carbon atoms of L^x8, L^x9 and W^x1 is 15 or less.

L^x1 is preferably a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, and more preferably a methylene group or an ethylene group.

L^x2 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, and more preferably a single bond.

L^x3 is preferably a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms.

L^x4 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms.

L^x5 is preferably a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, and more preferably a methylene group or an ethylene group.

L^x6 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, and more preferably a methylene group or an ethylene group.

L^x7 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms.

L^x8 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, and more preferably a single bond or a methylene group.

L^x9 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, and more preferably a single bond or a methylene group.

W^x1 is preferably a divalent alicyclic saturated hydrocarbon group having 3 to 10 carbon atoms, and more preferably a cyclohexanediyl group or an adamantanediyl group.

The group represented by formula (L1-1) includes, for example, the following divalent groups.

The group represented by formula (L1-2) includes, for example, the following divalent groups.

The group represented by formula (L1-3) includes, for example, the following divalent groups.

The group represented by formula (L1-4) includes, for example, the following divalent groups.

L⁵⁵ is preferably a single bond or a group represented by formula (L1-1).

Examples of the structural unit (a5-1) include the following structural units and structural units in which a methyl group corresponding to R⁵¹ in the structural unit (a5-1) in the following structural units is substituted with a hydrogen atom.

When the resin (A) or the like includes the structural unit (a5), the content is preferably 1 to 30 mol %, more preferably 2 to 20 mol %, and still more preferably 3 to 15 mol %, based on all structural units of the resin (A) or the like.

<Structural Unit (a6)>

The structural unit (a6) is a structural unit having an —SO₂— group, and it is preferable to have an —SO₂— group in a side chain.

The structural unit having an —SO₂— group may have a linear structure having an —SO₂— group, a branched structure having an —SO₂— group, or a cyclic structure (monocyclic and polycyclic structure) having an —SO₂— group. The structural unit is preferably a structural unit which has a cyclic structure having an —SO₂— group, and more preferably a structural unit which has a cyclic structure (sultone ring) having —SO₂—O—.

Examples of the sultone ring include rings represented by the following formula (T¹-1), formula (T¹-2), formula (T¹-3) and formula (T¹-4). The bonding site can be any position. The sultone ring may be monocyclic, and is preferably polycyclic. The polycyclic sultone ring means a bridged ring which has —SO₂—O— as an atomic group constituting the ring, and examples thereof include rings represented by formula (T¹-1) and formula (T¹-2). The sultone ring may have, as the atomic group constituting the ring, a heteroatom, in addition to —SO₂—O—, like the ring represented by formula (T¹-2). Examples of the heteroatom include an oxygen atom, a sulfur atom or a nitrogen atom, and an oxygen atom is preferable.

The sultone ring may have a substituent, and examples of the substituent include an alkyl group having 1 to 12 carbon atoms which may have a halogen atom or a hydroxy group, a halogen atom, a hydroxy group, a cyano group, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, a glycidyloxy group, an alkoxycarbonyl group having 2 to 12 carbon atoms and an alkylcarbonyl group having 2 to 4 carbon atoms.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group and a decyl group, and the alkyl group is preferably an alkyl group having 1 to 6 carbon atoms, and more preferably a methyl group.

Examples of the alkyl group having a halogen atom include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butyl group, a perfluorotert-butyl group, a perfluoropentyl group, a perfluorohexyl group, a trichloromethyl group, a tribromomethyl group and a triiodomethyl group, and a trifluoromethyl group is preferable.

Examples of the alkyl group having a hydroxy group include hydroxyalkyl groups such as a hydroxymethyl group and a 2-hydroxyethyl group.

Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, an octyloxy group, a decyloxy group and a dodecyloxy group.

Examples of the aryl group include a phenyl group, a naphthyl group, an anthryl group, a p-methylphenyl group, a p-tert-butylphenyl group, a p-adamantylphenyl group, a tolyl group, a xylyl group, a cumyl group, a mesityl group, a biphenyl group, a phenanthryl group, a 2,6-diethylphenyl group and a 2-methyl-6-ethylphenyl group.

Examples of the aralkyl group include a benzyl group, a phenethyl group, a phenylpropyl group, a naphthylmethyl group and a naphthylethyl group.

Examples of the alkoxycarbonyl group include groups in which an alkoxy group is bonded with a carbonyl group, such as a methoxycarbonyl group or an ethoxycarbonyl group, and preferably include an alkoxycarbonyl group having 6 or less carbon atoms and more preferably include a methoxycarbonyl group.

Examples of the alkylcarbonyl group include an acetyl group, a propionyl group and a butyryl group.

From the viewpoint that it is easy to produce a monomer from which the structural unit (a6) is derived, a sultone ring having no substituent is preferable.

The sultone ring is preferably a ring represented by the following formula (T1′):

wherein, in formula (T1′),

X¹¹ represents an oxygen atom, a sulfur atom or a methylene group,

R⁴¹ represents an alkyl group having 1 to 12 carbon atoms which may have a halogen atom or a hydroxy group, a halogen atom, a hydroxy group, a cyano group, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, a glycidyloxy group, an alkoxycarbonyl group having 2 to 12 carbon atoms, or an alkylcarbonyl group having 2 to 4 carbon atoms, ma represents an integer of 0 to 9, and when ma is 2 or more, a plurality of R⁴¹ may be the same or different, and

the bonding site may be any position.

X¹¹ is preferably an oxygen atom or a methylene group, and more preferably a methylene group.

Examples of R⁴¹ include those which are the same as the substituent of the sultone ring, and an alkyl group having 1 to 12 carbon atoms which may have a halogen atom or a hydroxy group is preferable.

ma is preferably 0 or 1, and more preferably 0.

Examples of the ring represented by formula (T1′) include the following rings. The bonding site may be any position. Particularly, the bonding site is preferably the 1-position or the 3-position.

It is preferable that the structural unit having an —SO₂— group further has a group derived from a polymerizable group. Examples of the polymerizable group include a vinyl group, an acryloyl group, a methacryloyl group, an acryloyloxy group, a methacryloyloxy group, an acryloylamino group, a methacryloylamino group, an acryloylthio group, a methacryloylthio group and the like.

Particularly, the monomer from which the structural unit (a6) is derived is preferably a monomer having an ethylenically unsaturated bond, and more preferably a (meth)acrylic monomer.

The structural unit (a6) is preferably a structural unit represented by formula (a6-0):

wherein, in formula (a6-0),

R^x represents an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, a hydrogen atom or a halogen atom,

A^xx represents an oxygen atom, —N(R^c)— or a sulfur atom,

A^x represents a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and —CH₂— included in the saturated hydrocarbon group may be replaced by —O—, —CO— or —N(R^d)—,

X¹¹, R⁴¹ and ma have the same meanings as above, and

R^c and R^d each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

Examples of the halogen atom as for R^x include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

Examples of the alkyl group as for R^x include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group and an n-hexyl group, and an alkyl group having 1 to 4 carbon atoms is preferable, and a methyl group or an ethyl group is more preferable.

Examples of the alkyl group having a halogen atom as for R^x include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butyl group, a perfluorotert-butyl group, a perfluoropentyl group, a perfluorohexyl group, a trichloromethyl group, a tribromomethyl group and a triiodomethyl group.

R^x is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group or an ethyl group, and still more preferably a hydrogen atom or a methyl group.

Examples of the divalent saturated hydrocarbon group as for A^x include a linear alkanediyl group, a branched alkanediyl group and a monocyclic or polycyclic divalent alicyclic saturated hydrocarbon group, and the divalent saturated hydrocarbon group may be those obtained by combining two or more of these groups.

Specific examples thereof include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diyl group, a dodecane-1,12-diyl group, a tridecane-1,13-diyl group, a tetradecane-1,14-diyl group, a pentadecane-1,15-diyl group, a hexadecane-1,16-diyl group, a heptadecane-1,17-diyl group, an ethane-1,1-diyl group, a propane-1,1-diyl group and a propane-2,2-diyl group;

branched alkanediyl groups such as a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group;

monocyclic divalent alicyclic saturated hydrocarbon groups which are cycloalkanediyl groups such as a cyclobutane-1,3-diyl group, a cyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group and a cyclooctane-1,5-diyl group; and polycyclic divalent alicyclic saturated hydrocarbon groups such as a norbornane-1,4-diyl group, a norbornane-2,5-diyl group, an adamantane-1,5-diyl group and an adamantane-2,6-diyl group.

The bonding site to the sultone ring as for A^x can be any position and is preferably the 1-position.

Examples of the structural unit (a6-0) include the following structural units.

Of these, structural units represented by formula (a6-1), formula (a6-2), formula (a6-6), formula (a6-7), formula (a6-8) and formula (a6-12) are preferable, and structural units represented by formula (a6-1), formula (a6-2), formula (a6-7) and (a6-8) are more preferable.

When the resin (A) or the like includes the structural unit (a6), the content is preferably 1 to 50 mol %, more preferably 2 to 40 mol %, and still more preferably 3 to 30 mol %, based on all structural units of the resin (A) or the like.

The resin (A) is preferably a resin including a structural unit (a1). Particularly, the resin (Ap) is more preferably a resin composed of a structural unit (IP), a structural unit (a1) and a structural unit (s), that is, a copolymer of a salt (I), a monomer (a1) and a monomer (s). The resin (A) including no structural unit (IP) is preferably a resin composed of a structural unit (a1) and a structural unit (s), that is, a copolymer of a monomer (a1) and a monomer (s).

The structural unit (a1) is preferably at least one selected from the group consisting of a structural unit (a1-0), a structural unit (a1-1) and a structural unit (a1-2) (preferably the structural unit having a cyclohexyl group or a cyclopentyl group), more preferably at least two, and still more preferably at least two selected from the group consisting of a structural unit (a1-1) and a structural unit (a1-2).

The structural unit (s) is preferably at least one selected from the group consisting of a structural unit (a2) and a structural unit (a3). The structural unit (a2) is preferably a structural unit (a2-1) or a structural unit (a2-A). The structural unit (a3) is preferably at least one selected from the group consisting of a structural unit represented by formula (a3-1), a structural unit represented by formula (a3-2) and a structural unit represented by formula (a3-4).

The respective structural units constituting the resin (A) or the like may be used alone, or two or more structural units may be used in combination. Using a monomer from which these structural units are derived, it is possible to produce by a known polymerization method (e.g., radical polymerization method). The content of the respective structural units included in the resin (A) or the like can be adjusted according to the amount of the monomer used in the polymerization.

The weight-average molecular weight of the resin (A) and the resin (Ap) is preferably 2,000 or more (more preferably 2,500 or more, and still more preferably 3,000 or more), and 50,000 or less (more preferably 30,000 or less, and still more preferably 15,000 or less). In the present specification, the weight-average molecular weight is a value determined by gel permeation chromatography under the conditions mentioned in Examples. The structural unit (IP) may constitute a dimer, a trimer, and a compound having a weight-average molecular weight of less than 2,000.

[Acid Generator]

The acid generator of the present invention is an acid generator including a salt (I) or a structural unit (IP). The structural unit (IP) can be included as a compound or a resin obtained by polymerizing a plurality thereof. In the acid generator, the salt (I) may be used alone, or two or more thereof may be used in combination. The compound or resin including the structural unit (IP) may be used alone, or two or more thereof may be used in combination. The acid generator of the present invention may include both the salt (I) and the structural unit (IP).

The acid generator of the present invention may include, in addition to the salt (I), an acid generator known in the resist field (hereinafter sometimes referred to as “acid generator (B)” or “second acid generator”). The acid generator (B) will be mentioned later.

When the acid generator include the salt (I) and the acid generator (B), a ratio of the content of the salt (I) to that of the acid generator (B) (mass ratio, salt (I):acid generator (B)) is usually 1:99 to 99:1, preferably 2:98 to 98:2, more preferably 5:95 to 95:5, still more preferably 10:90 to 90:10, yet more preferably 15:85 to 85:15, and particularly preferably 40:60 to 60:40.

[Resist Composition]

The resist composition of the present invention includes the acid generator of the present invention. The acid generator here may be a resin (Ap) including a structural unit (IP). The resist composition of the present invention may include the acid generator (B) including no acid generator of the present invention, and may include resin including no structural unit (IP). Here, the resin including no structural unit (IP) may be either a resin including a structural unit (a1) having an acid-labile group, or a resin including no structural unit (a1). However, the resist composition of the present invention includes at least one of the salt (I) and the structural unit (IP), and may include both of them. That is, the resist composition of the present invention may include an acid generator including the structural unit (IP) of the present invention or the salt (I) of the present invention. The structural unit (IP) may be in a form of either compound or resin. In other words, the resist composition of the present invention may include, as the acid generator, a resin (Ap) and/or a resin (A), and a salt (I). The resist composition of the present invention preferably include a resin including a structural unit (a1) having an acid-labile group. That is, the resist composition preferably includes at least:

• • (a) a salt (I) and a resin (A) including a structural unit (a1) having an acid-labile group,
  • (b) a resin (Ap) including a structural unit (IP) and a structural unit (a1) having an acid-labile group, or
  • (c) a resin (Ap) including a structural unit (IP) and a resin (A) including a structural unit (a1) having an acid-labile group.

Of these, preferred is a resist composition which includes a resin (Ap) including a structural unit (IP) and a structural unit (a1) having an acid-labile group. Two or more resins (A) and/or resins (Ap) may be included.

It is preferable that the resist composition of the present invention further includes a quencher (hereinafter sometimes referred to as “quencher (C)”) and/or a solvent (hereinafter sometimes referred to as “solvent (E)”). The resist composition of the present invention may further include a resin (A) or the like other than the resins mentioned above.

<Resin Other than Resin (A) or the Like>

The resist composition of the present invention may use a resin (Ap) and a resin (A) in combination with a resin other than the resin (Ap) and the resin (A). Examples of the resin other than the resin (Ap) and the resin (A) include a resin (AX) including the same structural unit as that of the resin (A), except that no structural unit (a1) is included in the above-mentioned resin (A), a resin including a structural unit (a4) and/or a structural unit (a5) (including neither structural unit (IP) nor structural unit (a1), hereinafter sometimes referred to as “resin (X)”) and the like.

Examples of the resin (AX) include a resin including a structural unit (a2), and a resin including a structural unit (a2-A) is preferable.

In the resin (AX), the content of the structural unit (a2-A) is preferably 5 mol % or more, more preferably 10 mol % or more, and still more preferably 15 mol % or more, and is preferably 80 mol % or less, and more preferably 70 mol % or less, based on the total of all structural units of the resin (AX).

Examples of the structural unit, which may be further included in the resin (X), include a structural unit (a2), a structural unit (a3) and structural units derived from other known monomers. Particularly, the resin (X) is preferably a resin composed only of a structural unit (a4) and/or a structural unit (a5), and more preferably a resin composed only of a structural unit (a4).

When the resin (X) includes a structural unit (a4), the content is usually 20 mol % or more, preferably 30 mol % or more, more preferably 40 mol % or more, and still more preferably 45 mol % or more, based on all structural units of the resin (X). The content is usually 100 mol % or less, preferably 80 mol % or less, more preferably 70 mol % or less, still more preferably 60 mol % or less, and yet more preferably 55 mol % or less, based on all structural units of the resin (X). Specifically, the content is usually 20 to 100 mol %, preferably 20 to 80 mol %, more preferably 30 to 70 mol %, still more preferably 40 to 60 mol %, and yet more preferably 45 to 55 mol %, based on all structural units of the resin (X). When the resin (X) includes a structural unit (a5), the content is usually 20 mol % or more, preferably 30 mol % or more, more preferably 40 mol % or more, and still more preferably 45 mol % or more, based on all structural units of the resin (X). The content is usually 100 mol % or less, preferably 80 mol % or less, more preferably 70 mol % or less, still more preferably 60 mol % or less, and yet more preferably 55 mol % or less, based on all structural units of the resin (X). Specifically, the content is usually 20 to 100 mol %, preferably 20 to 80 mol %, more preferably 30 to 70 mol %, still more preferably 40 to 60 mol %, and yet more preferably 45 to 55 mol %, based on all structural units of the resin (X). When the resin (X) includes a structural unit (a4) and a structural unit (a5), the total content is usually 40 mol % or more, preferably 60 mol % or more, more preferably 70 mol % or more, and still more preferably 80 mol % or more, based on all structural units of the resin (X). The total content is usually 100 mol % or less, based on all structural units of the resin (X). Specifically, the total content is usually 40 to 100 mol %, preferably 60 to 100 mol %, more preferably 70 to 100 mol %, and still more preferably 80 to 100 mol %, based on all structural units of the resin (X).

The respective structural unit constituting the resin (AX) and the resin (X) may be used alone, or two or more structural units may be used in combination. Using a monomer from which these structural units are derived, it is possible to produce by a known polymerization method (e.g., radical polymerization method). The content of the respective structural units included in the resin (AX) and the resin (X) can be adjusted according to the amount of the monomer used in the polymerization.

The weight-average molecular weight of the resin (AX) and the resin (X) is preferably 6,000 or more (more preferably 7,000 or more) and 80,000 or less (more preferably 60,000 or less). The resin (AX) and the resin (X) may comprise the oligomer in which the weight-average molecular weight is less than 6,000. The measurement means of the weight-average molecular weight of the resin (AX) and the resin (X) is the same as in the case of the resin (A) or the like.

When the resist composition of the present invention includes the resin (X), the content is preferably 1 to 60 parts by mass, more preferably 1 to 50 parts by mass, still more preferably 1 to 40 parts by mass, yet more preferably 1 to 30 parts by mass, and further preferably 1 to 8 parts by mass, based on 100 parts by mass of the resin (A) or the like.

The content of the resin (A) or the like in the resist composition is preferably 80% by mass or more and 99% by mass or less, and more preferably 90% by mass or more and 99% by mass or less, based on the solid component of the resist composition. The content of the resin (Ap) is preferably 80% by mass or more and 99% by mass or less, and more preferably 90% by mass or more and 99% by mass or less, based on the solid component of the resist composition. When including resins other than the resin (A) or the like, the total content of the resin (A) or the like and resins other than the resin (A) or the like is preferably 80% by mass or more and 99% by mass or less, and more preferably 90% by mass or more and 99% by mass or less, based on the solid component of the resist composition. In the present specification, “solid component of resist composition” means the total of components in which the below-mentioned solvent (E) is removed from the total amount of the resist composition. The solid component of the resist composition and the content of the resin thereto can be measured by a known analysis means such as liquid chromatography or gas chromatography.

<Acid Generator>

The acid generator of the present invention may be either an acid generator including only a salt (I) and/or a structural unit (IP), or an acid generator including a salt (I) and/or a structural unit (IP) and an acid generator (B) which is known in the resist field.

The acid generator used in the resist composition of the present invention may be used alone, or two or more thereof may be used in combination.

Either nonionic or ionic acid generator may be used as the acid generator (B). Examples of the nonionic acid generator include sulfonate esters (e.g., 2-nitrobenzyl ester, aromatic sulfonate, oxime sulfonate, N-sulfonyloxyimide, sulfonyloxyketone, diazonaphthoquinone 4-sulfonate), sulfones (e.g., disulfone, ketosulfone, sulfonyldiazomethane) and the like. Typical examples of the ionic acid generator include onium salts containing an onium cation (e.g., diazonium salt, phosphonium salt, sulfonium salt, iodonium salt). Examples of the anion of the onium salt include sulfonic acid anion, sulfonylimide anion, sulfonylmethide anion and the like.

Specific examples of the acid generator (B) include compounds generating an acid upon exposure to radiation mentioned in JP 63-26653 A, JP 55-164824 A, JP 62-69263 A, JP 63-146038 A, JP 63-163452 A, JP 62-153853 A, JP 63-146029 A, U.S. Pat. Nos. 3,779,778, 3,849,137, DE Patent No. 3914407 and EP Patent No. 126,712. Compounds produced by a known method may also be used. Two or more acid generators (B) may also be used in combination.

The acid generator (B) is preferably a salt represented by formula (B1) (hereinafter sometimes referred to as “acid generator (B1)”):

wherein, in formula (B1),

Q^b1 and Q^b2 each independently represent a hydrogen atom, a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms or an alkyl group having 1 to 6 carbon atoms.

L^b1 represents a divalent saturated hydrocarbon group having 1 to 24 carbon atoms, —CH₂— included in the divalent saturated hydrocarbon group may be replaced by —O— or —CO—, and a hydrogen atom included in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group,

Y represents a methyl group which may have a substituent or an alicyclic hydrocarbon group having 3 to 24 carbon atoms which may have a substituent, and —CH₂— included in the alicyclic hydrocarbon group may be replaced by —O—, —S—, —SO₂— or —CO—, and Z1⁺ represents an organic cation.

Examples of Q^b1, Q^b2 and L^b1 in formula (B1) include the same one as for Q^b1, Q^b2 and L^b1 in formula (I).

Examples of the alicyclic hydrocarbon group having 3 to 24 carbon atoms which may have a substituent (—CH₂— included in the alicyclic hydrocarbon group may be replaced by —O—, —S—, —SO₂— or —CO—) in Y include the same one as for Y^b1 in formula (I).

When the alicyclic hydrocarbon group represented by Y is a spiro ring containing an oxygen atom, such as formula (Y28) to formula (Y35), formula (Y39) to formula (Y40), formula (Y42) or formula (Y43), the alkanediyl group between two oxygen atoms preferably has one or more fluorine atoms. Of alkanediyl groups included in a ketal structure, it is preferable that a methylene group adjacent to the oxygen atom is not substituted with a fluorine atom.

Examples of the substituent of the methyl group represented by Y include a halogen atom, a hydroxy group, an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, a glycidyloxy group, a —(CH₂)_{j a}—CO—O—R^b1 group or a —(CH₂)_{j a}—O—CO—R^b1 group (wherein R^b1 represents an alkyl group having 1 to 16 carbon atoms, an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group obtained by combining these groups, ja represents an integer of 0 to 4, —CH₂— included in the alkyl group and the alicyclic hydrocarbon group may be replaced by —O—, —SO₂— or —CO—, a hydrogen atom included in the alkyl group, the alicyclic hydrocarbon group and the aromatic hydrocarbon group may be substituted with a hydroxy group or a fluorine atom).

Y is preferably an alicyclic hydrocarbon group having 3 to 24 carbon atoms which may have a substituent, more preferably an alicyclic hydrocarbon group having 3 to 20 carbon atoms which may have a substituent, still more preferably an alicyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent, and yet more preferably an adamantyl group which may have a substituent, or a norbornyl group which may have a substituent, and —CH₂— constituting the alicyclic hydrocarbon group, the adamantyl group or the norbornyl group may be replaced by —O—, —S—, —SO₂— or —CO—. Specifically, the followings are exemplified.

Of these, Y is preferably an adamantyl group, a hydroxyadamantyl group, an oxoadamantyl group, a norbornanelactone group, or groups represented by formula (Y42), formula (Y100) to formula (Y114) and formula (Y134) to formula (Y139), and particularly preferably a hydroxyadamantyl group, an oxoadamantyl group, a group including these groups, or groups represented by formula (Y42), formula (Y100) to formula (Y114) and formula (Y134) to formula (Y139).

The anion in the salt represented by formula (B1) is preferably anions represented by formula (B1-A-1) to formula (B1-A-65) [hereinafter sometimes referred to as “anion (B1-A-1)” according to the number of formula], and more preferably anion represented by any one of formula (B1-A-1) to formula (B1-A-4), formula (B1-A-9), formula (B1-A-10), formula (B1-A-24) to formula (B1-A-33), formula (B1-A-36) to formula (B1-A-40) and formula (B1-A-47) to formula (B1-A-65).

Rⁱ² to Rⁱ⁷ each independently represent, for example, an alkyl group having 1 to 4 carbon atoms, and preferably a methyl group or an ethyl group. Rⁱ⁸ is, for example, a chain hydrocarbon group having 1 to 12 carbon atoms, preferably an alkyl group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group having 5 to 12 carbon atoms, or a group formed by combining these groups, and more preferably a methyl group, an ethyl group, a cyclohexyl group or an adamantyl group. L^A41 is a single bond or an alkanediyl group having 1 to 4 carbon atoms. Q^b1 and Q^b2 are the same as defined above.

Specific examples of the anion in the salt represented by formula (B1) include anions mentioned in JP 2010-204646 A.

The anion in the salt represented by formula (B1) preferably includes anions represented by formula (B1a-1) to formula (B1a-43).

Of these, an anion represented by any one of formula (B1a-1) to formula (B1a-4), formula (B1a-7) to formula (B1a-11), formula (B1a-14) to formula (B1a-30) and formula (B1a-35) to formula (B1a-43) is preferable.

Examples of the sulfonylimide anion include the followings.

Examples of the sulfonylmethide anion include the followings.

Examples of the organic cation of Z⁺ include an organic onium cation, an organic sulfonium cation, an organic iodonium cation, an organic ammonium cation, a benzothiazolium cation and an organic phosphonium cation. Of these, an organic sulfonium cation and an organic iodonium cation are preferable, and an arylsulfonium cation is more preferable. Specific examples thereof include a cation represented by any one of formula (b2-1) to formula (b2-4) (hereinafter sometimes referred to as “cation (b2-1)” according to the number of formula).

In formula (b2-1) to formula (b2-4),

R^b4 to R^b6 each independently represent a chain hydrocarbon group having 1 to 30 carbon atoms, an alicyclic hydrocarbon group having 3 to 36 carbon atoms or an aromatic hydrocarbon group having 6 to 36 carbon atoms, a hydrogen atom included in the chain hydrocarbon group may be substituted with a hydroxy group, an alkoxy group having 1 to 12 carbon atoms, an alicyclic hydrocarbon group having 3 to 12 carbon atoms or an aromatic hydrocarbon group having 6 to 18 carbon atoms, a hydrogen atom included in the alicyclic hydrocarbon group may be substituted with a halogen atom, an aliphatic hydrocarbon group having 1 to 18 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms or a glycidyloxy group, and a hydrogen atom included in the aromatic hydrocarbon group may be substituted with a halogen atom, a hydroxy group, an aliphatic hydrocarbon group having 1 to 18 carbon atoms, an alkyl fluoride group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms.

R^b4 and R^b5 may be bonded to each other to form a ring together with sulfur atoms to which R^b4 and R^b5 are bonded, and —CH₂— included in the ring may be replaced by —O—, —S— or —CO—,

R^b7 and R^b8 each independently represent a halogen atom, a hydroxy group, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, an alkyl fluoride group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms,

m2 and n2 each independently represent an integer of 0 to 5,

when m2 is 2 or more, a plurality of R^b7 may be the same or different, and when n2 is 2 or more, a plurality of R^b8 may be the same or different,

R^b9 and R^b10 each independently represent a chain hydrocarbon group having 1 to 36 carbon atoms or an alicyclic hydrocarbon group having 3 to 36 carbon atoms,

R^b9 and R^b10 may be bonded to each other to form a ring together with sulfur atoms to which R^b9 and R^b10 are bonded, and —CH₂— included in the ring may be replaced by —O—, —S— or —CO—,

R^b11 represents a hydrogen atom, a chain hydrocarbon group having 1 to 36 carbon atoms, an alicyclic hydrocarbon group having 3 to 36 carbon atoms or an aromatic hydrocarbon group having 6 to 18 carbon atoms,

R^b12 represents a chain hydrocarbon group having 1 to 12 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms or an aromatic hydrocarbon group having 6 to 18 carbon atoms, a hydrogen atom included in the chain hydrocarbon group may be substituted with an aromatic hydrocarbon group having 6 to 18 carbon atoms, a hydrogen atom included in the aromatic hydrocarbon group may be substituted with an alkoxy group having 1 to 12 carbon atoms or an alkylcarbonyloxy group having 1 to 12 carbon atoms,

R^b11 and R^b12 may be bonded to each other to form a ring, including —CH—CO— to which R^b11 and R^b12 are bonded, and —CH₂— included in the ring may be replaced by —O—, —S— or —CO—,

R^b13 to R^b18 each independently represent a halogen atom, a hydroxy group, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, an alkyl fluoride group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms,

R^b13 and R^b14 may be bonded to each other to form a ring containing a sulfur atom together with the benzene ring to which R^b13 and R^b14 are bonded, and —CH₂— included in the ring may be replaced by —O—, —S— or —CO—,

L^b31 represents a sulfur atom or an oxygen atom, o2, p2, s2 and t2 each independently represent an integer of 0 to 5,

q2 and r2 each independently represent an integer of 0 to 4,

u2 represents 0 or 1, and when o2 is 2 or more, a plurality of R^b13 are the same or different, when p2 is 2 or more, a plurality of R^b14 are the same or different, when q2 is 2 or more, a plurality of

R^b15 are the same or different, when r2 is 2 or more, a plurality of R^b16 are the same or different, when s2 is 2 or more, a plurality of R^b17 are the same or different, and when t2 is 2 or more, a plurality of R^b18 are the same or different.

When u2 is 0, any one of o2, p2, q2 and r2 is preferably 1 or more and at least one of R^b13 to R^b16 is preferably a halogen atom, and when u2 is 1, any one of o2, p2, s2, t2, q2 and r2 is preferably 1 or more and at least one of R^b13 to R^b18 is preferably a halogen atom.

Further, when u2 is 0, r2 is preferably 1 or more, and more preferably 1. When u2 is 0 and r2 is 1 or more, R^b16 is preferably a halogen atom.

The aliphatic hydrocarbon group represents a chain hydrocarbon group and an alicyclic hydrocarbon group.

Examples of the chain hydrocarbon group include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group and a 2-ethylhexyl group.

Particularly, the chain hydrocarbon group of R^b9 to R^b12 preferably has 1 to 12 carbon atoms.

The alicyclic hydrocarbon group may be either monocyclic or polycyclic, and examples of the monocyclic alicyclic hydrocarbon group include cycloalkyl groups such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group and a cyclodecyl group. Examples of the polycyclic alicyclic hydrocarbon group include a decahydronaphthyl group, an adamantyl group, a norbornyl group and the following groups.

Particularly, the alicyclic hydrocarbon group of R^b9 to R^b12 preferably has 3 to 18 carbon atoms, and more preferably 4 to 12 carbon atoms.

Examples of the alicyclic hydrocarbon group in which a hydrogen atom is substituted with an aliphatic hydrocarbon group include a methylcyclohexyl group, a dimethylcyclohexyl group, a 2-methyladamantan-2-yl group, a 2-ethyladamantan-2-yl group, a 2-isopropyladamantan-2-yl group, a methylnorbornyl group, an isobornyl group and the like. In the alicyclic hydrocarbon group in which a hydrogen atom is substituted with an aliphatic hydrocarbon group, the total number of carbon atoms of the alicyclic hydrocarbon group and the aliphatic hydrocarbon group is preferably 20 or less.

The alkyl fluoride group represents an alkyl group having 1 to 12 carbon atoms which has a fluorine atom, and examples thereof include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a perfluorobutyl group and the like. The number of carbon atoms of the alkyl fluoride group is preferably 1 to 9, more preferably 1 to 6, still more preferably 1 to 4.

Examples of the aromatic hydrocarbon group include aryl groups such as a phenyl group, a biphenyl group, a naphthyl group and a phenanthryl group. The aromatic hydrocarbon group may have a chain hydrocarbon group or an alicyclic hydrocarbon group, and examples thereof include an aromatic hydrocarbon group having a chain hydrocarbon group (a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a p-ethylphenyl group, a p-tert-butylphenyl group, a 2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group, etc.) and an aromatic hydrocarbon group having an alicyclic hydrocarbon group (a p-cyclohexylphenyl group, a p-adamantylphenyl group, etc.). When the aromatic hydrocarbon group has a chain hydrocarbon group or an alicyclic hydrocarbon group, a chain hydrocarbon group having 1 to 18 carbon atoms and an alicyclic hydrocarbon group having 3 to 18 carbon atoms are preferable.

Examples of the aromatic hydrocarbon group in which a hydrogen atom is substituted with an alkoxy group include a p-methoxyphenyl group and the like.

Examples of the chain hydrocarbon group in which a hydrogen atom is substituted with an aromatic hydrocarbon group include aralkyl groups such as a benzyl group, a phenethyl group, a phenylpropyl group, a trityl group, a naphthylmethyl group and a naphthylethyl group.

Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, an octyloxy group, a decyloxy group and a dodecyloxy group.

Examples of the alkylcarbonyl group include an acetyl group, a propionyl group and a butyryl group.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

Examples of the alkylcarbonyloxy group include a methylcarbonyloxy group, an ethylcarbonyloxy group, a propylcarbonyloxy group, an isopropylcarbonyloxy group, a butylcarbonyloxy group, a sec-butylcarbonyloxy group, a tert-butylcarbonyloxy group, a pentylcarbonyloxy group, a hexylcarbonyloxy group, an octylcarbonyloxy group and a 2-ethylhexylcarbonyloxy group.

The ring formed by bonding R^b4 and R^bs each other, together with sulfur atoms to which R^b4 and R^bs are bonded, may be a monocyclic, polycyclic, aromatic, nonaromatic, saturated or unsaturated ring. This ring includes a ring having 3 to 18 carbon atoms and is preferably a ring having 4 to 18 carbon atoms. The ring containing a sulfur atom includes a 3-membered to 12-membered ring and is preferably a 3-membered to 7-membered ring and includes, for example, the following rings and the like. * represents a bonding site.

The ring formed by combining R^b9 and R^b10 together may be a monocyclic, polycyclic, aromatic, nonaromatic, saturated or unsaturated ring. This ring includes a 3-membered to 12-membered ring and is preferably a 3-membered to 7-membered ring. The ring includes, for example, a thiolan-1-ium ring (tetrahydrothiophenium ring), a thian-1-ium ring, a 1,4-oxathian-4-ium ring and the like.

The ring formed by combining R^b11 and R^b12 together may be a monocyclic, polycyclic, aromatic, nonaromatic, saturated or unsaturated ring. This ring includes a 3-membered to 12-membered ring and is preferably a 3-membered to 7-membered ring. Examples thereof include an oxocycloheptane ring, an oxocyclohexane ring, an oxonorbornane ring, an oxoadamantane ring and the like.

Of cation (b2-1) to cation (b2-4), a cation (b2-1) is preferable.

Examples of the cation (b2-1) include the following cations.

Examples of the cation (b2-2) include the following cations.

Examples of the cation (b2-3) include the following cations.

Examples of the cation (b2-4) include the following cations.

The acid generator (B) is a combination of the anion mentioned above and the organic cation mentioned above, and these can be optionally combined. The acid generator (B) preferably includes a combination of an anion represented by any one of formula (B1a-1) to formula (B1a-4), formula (B1a-7) to formula (B1a-11), formula (B1a-14) to formula (B1a-30) and formula (B1a-35) to formula (B1a-43) with a cation (b2-1), a cation (b2-2), a cation (b2-3) or a cation (b2-4).

The acid generator (B) preferably includes those represented by formula (B1-1) to formula (B1-60). Of these, those containing an arylsulfonium cation are preferable and those represented by formula (B1-1) to formula (B1-3), formula (B1-5) to formula (B1-7), formula (B1-11) to formula (B1-14), formula (B1-20) to formula (B1-26), formula (B1-29) and formula (B1-31) to formula (B1-60) are particularly preferable.

In the resist composition of the present invention, the content of the acid generator is preferably 0.1% by mass or more and 99.9% by mass or less, more preferably 1% by mass or more and 45% by mass or less, still more preferably 1% by mass or more and 40% by mass or less, and yet preferably 3% by mass or more and 40% by mass or less, based on the solid content of the resist composition. When including the resin (A) or the like, the content of the acid generator is preferably 1 part by mass or more and 45 parts by mass or less, more preferably 1 part by mass or more and 40 parts by mass or less, and still more preferably 3 parts by mass or more and 35 parts by mass or less, based on 100 parts by mass of the resin (A) or the like.

<Solvent (E)>

The content of the solvent (E) in the resist composition is usually 90% by mass or more and 99.9% by mass or less, preferably 92% by mass or more and 99% by mass or less, and more preferably 94% by mass or more and 99% by mass or less. The content of the solvent (E) can be measured, for example, by a known analysis means such as liquid chromatography or gas chromatography.

Examples of the solvent (E) include glycol ether esters such as ethylcellosolve acetate, methylcellosolve acetate and propylene glycol monomethyl ether acetate; glycol ethers such as propylene glycol monomethyl ether; esters such as ethyl lactate, butyl acetate, amyl acetate and ethyl pyruvate; ketones such as acetone, methyl isobutyl ketone, 2-heptanone and cyclohexanone; and cyclic esters such as γ-butyrolactone. The solvent (E) may be used alone, or two or more solvents may be used.

<Quencher (C)>

Examples of the quencher (C) include a salt generating an acid having an acidity lower than that of an acid generated from an acid generator (a salt (I), a structural unit (IP) and an acid generator (B1)), and a basic nitrogen-containing organic compound. The content of the quencher (C) is preferably about 0.01 to 15% by mass, more preferably about 0.01 to 10% by mass, still more preferably about 0.1 to 8% by mass, and yet more preferably about 0.1 to 7% by mass, based on the amount of the solid component of the resist composition.

<Salt Generating Acid Having Acidity Lower than that of Acid Generated from Acid Generator>

The acidity in a salt generating an acid having an acidity lower than that of an acid generated from the acid generator is indicated by the acid dissociation constant (pKa). Regarding the salt generating an acid having an acidity lower than that of an acid generated from the acid generator, the acid dissociation constant of an acid generated from the salt usually meets the following inequality: −3<pKa, preferably −1<pKa<7, and more preferably 0<pKa<5.

Examples of the salt generating an acid having an acidity lower than that of an acid generated from the acid generator include salts represented by the following formulas, a salt represented by formula (D) mentioned in JP 2015-147926 A (hereinafter sometimes referred to as “weak acid inner salt (D)”), and salts mentioned in JP 2012-229206 A, JP 2012-6908 A, JP 2012-72109 A, JP 2011-39502 A and JP 2011-191745 A. The salt generating an acid having an acidity lower than that of an acid generated from the acid generator is preferably a salt generating a carboxylic acid having an acidity lower than that of an acid generated from the acid generator (salt having a carboxylic acid anion), more preferably a weak acid inner salt (D), and still more preferably a diphenyliodonium salt containing a phenyl group substituted with a carboxylic acid anion among the weak acid inner salt (D).

Examples of the weak acid inner salt (D) is preferably a diphenyliodonium salt having an iodonium cation to which two phenyl groups are bonded, and a carboxylic acid anion substituted with at least one phenyl group of two phenyl groups bonded to the iodonium cation, and specific examples thereof include a salt represented by the following formula:

wherein, in formula (D),

R^D1 and R^D2 each independently represent a hydrocarbon group having 1 to 12 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an acyl group having 2 to 7 carbon atoms, an acyloxy group having 2 to 7 carbon atoms, an alkoxycarbonyl group having 2 to 7 carbon atoms, a nitro group or a halogen atom, and

m′ and n′ each independently represent an integer of 0 to 4, and when m′ is 2 or more, a plurality of R^D1 may be the same or different, and when n′ is 2 or more, a plurality of R^D2 may be the same or different.

Examples of the hydrocarbon group as for R^D1 and R^D2 include a chain hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and a group formed by combining these groups.

Examples of the chain hydrocarbon group include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, a nonyl group and the like.

The alicyclic hydrocarbon group may be either monocyclic or polycyclic, or may be either saturated or unsaturated. Examples thereof include cycloalkyl groups such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cyclononyl group and a cyclododecyl group, a norbornyl group, an adamantyl group and the like.

Examples of the aromatic hydrocarbon group include aryl groups such as a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenyl group, a 4-ethylphenyl group, a 4-propylphenyl group, a 4-isopropylphenyl group, a 4-butylphenyl group, a 4-t-butylphenyl group, a 4-hexylphenyl group, a 4-cyclohexylphenyl group, an anthryl group, a p-adamantylphenyl group, a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a biphenyl group, a phenanthryl group, a 2,6-diethylphenyl group and a 2-methyl-6-ethylphenyl group.

Examples of the group formed by combining these groups include an alkyl-cycloalkyl group, a cycloalkyl-alkyl group, an aralkyl group (e.g., a phenylmethyl group, a 1-phenylethyl group, a 2-phenylethyl group, a 1-phenyl-1-propyl group, a 1-phenyl-2-propyl group, a 2-phenyl-2-propyl group, a 3-phenyl-1-propyl group, a 4-phenyl-1-butyl group, a 5-phenyl-1-pentyl group, a 6-phenyl-1-hexyl group, etc.) and the like.

Examples of the alkoxy group include a methoxy group, an ethoxy group and the like.

Examples of the acyl group include an acetyl group, a propanoyl group, a benzoyl group, a cyclohexanecarbonyl group and the like.

Examples of the acyloxy group include a group obtained by bonding an oxy group (—O—) to the above acyl group.

Examples of the alkoxycarbonyl group include a group obtained by bonding a carbonyl group (—CO—) to the above alkoxy group.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and the like.

Preferably, R^D1 and R^D2 each independently represent an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an acyl group having 2 to 4 carbon atoms, an acyloxy group having 2 to 4 carbon atoms, an alkoxycarbonyl group having 2 to 4 carbon atoms, a nitro group or a halogen atom.

Preferably, m′ and n′ are each independently an integer of 0 to 2, and more preferably 0, and when m′ is 2 or more, a plurality of R^D1 may be the same or different, and when n′ is 2 or more, a plurality of R^D2 may be the same or different.

More specifically, the following salts are exemplified.

Examples of the basic nitrogen-containing organic compound include amine and an ammonium salt. Examples of the amine include an aliphatic amine and an aromatic amine. Examples of the aliphatic amine include a primary amine, a secondary amine and a tertiary amine.

Examples of the amine include 1-naphthylamine, 2-naphthylamine, aniline, diisopropylaniline, 2-, 3- or 4-methylaniline, 4-nitroaniline, N-methylaniline, N,N-dimethylaniline, diphenylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, triethylamine, trimethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, methyldibutylamine, methyldipentylamine, methyldihexylamine, methyldicyclohexylamine, methyldiheptylamine, methyldioctylamine, methyldinonylamine, methyldidecylamine, ethyldibutylamine, ethyldipentylamine, ethyldihexylamine, ethyldiheptylamine, ethyldioctylamine, ethyldinonylamine, ethyldidecylamine, dicyclohexylmethylamine, tris[2-(2-methoxyethoxy)ethyl]amine, triisopropanolamine, ethylenediamine, tetramethylenediamine, hexamethylenediamine, 4,4′-diamino-1,2-diphenylethane, 4,4′-diamino-3,3′-dimethyldiphenylmethane, 4,4′-diamino-3,3′-diethyldiphenylmethane, 2,2′-methylenebisaniline, imidazole, 4-methylimidazole, pyridine, 4-methylpyridine, 1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane, 1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene, 1,3-di(4-pyridyl)propane, 1,2-di(4-pyridyloxy)ethane, di(2-pyridyl)ketone, 4,4′-dipyridyl sulfide, 4,4′-dipyridyl disulfide, 2,2′-dipyridylamine, 2,2′-dipicolylamine, bipyridine and the like, preferably an aromatic amine such as diisopropylaniline, and more preferably 2,6-diisopropylaniline.

Examples of the ammonium salt include tetramethylammonium hydroxide, tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide, tetrahexylammonium hydroxide, tetraoctylammonium hydroxide, phenyltrimethylammonium hydroxide, 3-(trifluoromethyl)phenyltrimethylammonium hydroxide, tetra-n-butylammonium salicylate and choline.

<Other Components>

The resist composition of the present invention may also include components other than the components mentioned above (hereinafter sometimes referred to as “other components (F)”). The other components (F) are not particularly limited and it is possible to use various additives known in the resist field, for example, sensitizers, dissolution inhibitors, surfactants, stabilizers and dyes.

<Preparation of Resist Composition>

The resist composition of the present invention can be prepared by mixing a salt represented by formula (I) or a compound or resin including a structural unit represented by formula (IP), and if necessary, a resin (A) or the like, an acid generator (B), resins other than the resin (A) or the like, a solvent (E), a quencher (C) and other components (F). The order of mixing these components is any order and is not particularly limited. It is possible to select, as the temperature during mixing, appropriate temperature from 10 to 40° C., according to the type of the resin, the solubility in the solvent (E) of the resin and the like. It is possible to select, as the mixing time, appropriate time from 0.5 to 24 hours according to the mixing temperature. The mixing means is not particularly limited and it is possible to use mixing with stirring.

After mixing the respective components, the mixture is preferably filtered through a filter having a pore diameter of about 0.003 to 0.2 μm.

<Method for Producing Resist Pattern>

The method for producing a resist pattern of the present invention include:

• • (1) a step of applying the resist composition of the present invention on a substrate,
  • (2) a step of drying the applied composition to form a composition layer,
  • (3) a step of exposing the composition layer,
  • (4) a step of heating the exposed composition layer, and
  • (5) a step of developing the heated composition layer.

The resist composition can be usually applied on a substrate using a conventionally used apparatus, such as a spin coater. Examples of the substrate include inorganic substrates such as a silicon wafer, and organic substrates in which a resist film is formed on the surface. Before applying the resist composition, the substrate may be washed, and an organic antireflection film may be formed on the substrate.

The solvent is removed by drying the applied composition to form a composition layer. Drying is performed by evaporating the solvent using a heating device such as a hot plate (so-called “prebake”), or a decompression device. The heating temperature is preferably 50 to 200° C. and the heating time is preferably 10 to 180 seconds. The pressure during drying under reduced pressure is preferably about 1 to 1.0×10⁵ Pa.

The composition layer thus obtained is usually exposed using an aligner. The aligner may be a liquid immersion aligner. It is possible to use, as an exposure source, various exposure sources, for example, exposure sources capable of emitting laser beam in an ultraviolet region such as KrF excimer laser (wavelength of 248 nm), ArF excimer laser (wavelength of 193 nm) and F₂ excimer laser (wavelength of 157 nm), an exposure source capable of emitting harmonic laser beam in a far-ultraviolet or vacuum ultra violet region by wavelength-converting laser beam from a solid-state laser source (YAG or semiconductor laser), an exposure source capable of emitting electron beam or extreme ultraviolet light (EUV) and the like. In the present specification, such exposure to radiation is sometimes collectively referred to as “exposure”. The exposure is usually performed through a mask corresponding to a pattern to be required. When electron beam is used as the exposure source, exposure may be performed by direct writing without using the mask.

The exposed composition layer is subjected to a heat treatment (so-called “post-exposure bake”) to promote the deprotection reaction in an acid-labile group. The heating temperature is usually about 50 to 200° C., and preferably about 70 to 150° C. It is also possible to perform a chemical treatment (silylation) which adjusts the hydrophilicity or hydrophobicity of the resin on a surface side of the composition after heating. Before performing the development, the steps of application of the resist composition, drying, exposure and heating may be repeatedly performed on the exposed composition layer.

The heated composition layer is usually developed with a developing solution using a development apparatus. Examples of the developing method include a dipping method, a paddle method, a spraying method, a dynamic dispensing method and the like. The developing temperature is preferably, for example, 5 to 60° C. and the developing time is preferably, for example, 5 to 300 seconds. It is possible to produce a positive resist pattern or negative resist pattern by selecting the type of the developing solution as follows.

When the positive resist pattern is produced from the resist composition of the present invention, an alkaline developing solution is used as the developing solution. The alkaline developing solution may be various aqueous alkaline solutions used in this field. Examples thereof include aqueous solutions of tetramethylammonium hydroxide and (2-hydroxyethyl)trimethylammonium hydroxide (commonly known as choline). The surfactant may be contained in the alkaline developing solution.

It is preferable that the developed resist pattern is washed with ultrapure water and then water remaining on the substrate and the pattern is removed.

When the negative resist pattern is produced from the resist composition of the present invention, a developing solution containing an organic solvent (hereinafter sometimes referred to as “organic developing solution”) is used as the developing solution.

Examples of the organic solvent contained in the organic developing solution include ketone solvents such as 2-hexanone and 2-heptanone; glycol ether ester solvents such as propylene glycol monomethyl ether acetate; ester solvents such as butyl acetate; glycol ether solvents such as propylene glycol monomethyl ether; amide solvents such as N,N-dimethylacetamide; and aromatic hydrocarbon solvents such as anisole.

The content of the organic solvent in the organic developing solution is preferably 90% by mass or more and 100% by mass or less, more preferably 95% by mass or more and 100% by mass or less, and still more preferably the organic developing solution is substantially composed of the organic solvent.

Particularly, the organic developing solution is preferably a developing solution containing butyl acetate and/or 2-heptanone. The total content of butyl acetate and 2-heptanone in the organic developing solution is preferably 50% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and still more preferably the organic developing solution is substantially composed of butyl acetate and/or 2-heptanone.

The surfactant may be contained in the organic developing solution. A trace amount of water may be contained in the organic developing solution.

During development, the development may be stopped by replacing by a solvent with the type different from that of the organic developing solution.

The developed resist pattern is preferably washed with a rinsing solution. The rinsing solution is not particularly limited as long as it does not dissolve the resist pattern, and it is possible to use a solution containing an ordinary organic solvent which is preferably an alcohol solvent or an ester solvent.

After washing, the rinsing solution remaining on the substrate and the pattern is preferably removed.

<Applications>

The resist composition of the present invention is suitable as a resist composition for exposure of KrF excimer laser, a resist composition for exposure of ArF excimer laser, a resist composition for exposure of electron beam (EB) or a resist composition for exposure of EUV, particularly a resist composition for exposure of electron beam (EB) or a resist composition for exposure of EUV, and the resist composition is useful for fine processing of semiconductors.

EXAMPLES

The present invention will be described more specifically by way of Examples. Percentages and parts expressing the contents or amounts used in the Examples are by mass unless otherwise specified.

The weight-average molecular weight is a value determined by gel permeation chromatography. Analysis conditions of gel permeation chromatography are as follows.

• • Column: TSKgel Multipore HXL-M×3+guardcolumn (manufactured by TOSOH CORPORATION)
  • Eluent: tetrahydrofuran
  • Flow rate: 1.0 mL/min
  • Detector: RI detector
  • Column temperature: 40° C.
  • Injection amount: 100 μl
  • Molecular weight standards: polystyrene standard (manufactured by TOSOH CORPORATION)

Structures of compounds were confirmed by measuring a molecular ion peak using mass spectrometry (LC: Model 1100, manufactured by Agilent Technologies, Inc., and MASS: Model LC/MSD, manufactured by Agilent Technologies, Inc.). The value of this molecular ion peak in the following Examples is indicated by “MASS”.

Example 1: Synthesis of Salt Represented by Formula (I-561)

9.58 Parts of a salt represented by formula (I-561-a) and 50 parts of chloroform were mixed, and after stirring at 23° C. for 30 minutes, 1.62 parts of a compound represented by formula (I-1-b) was added, followed by temperature rise to 50° C. and further stirring at 50° C. for 2 hours. To the reaction mixture thus obtained, 2.50 parts of a compound represented by formula (I-1-c) was added, followed by stirring at 50° C. for 10 hours. The reaction mixture thus obtained was cooled to 23° C. and 25 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. To the organic layer thus obtained, 25 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 3 parts of acetonitrile and 30 parts of tert-butyl methyl ether were added to the concentrated residue, and after stirring at 23° C. for 30 minutes, the supernatant was removed, followed by concentration to obtain 9.69 parts of a salt represented by formula (1-561).

MASS (ESI (+) Spectrum): M⁺ 782.9

MASS (ESI (−) Spectrum): M⁻ 407.1

Example 2: Synthesis of Salt Represented by Formula (I-1653)

9.58 Parts of a salt represented by formula (I-1653-a) and 50 parts of chloroform were mixed, and after stirring at 23° C. for 30 minutes, 1.62 parts of a compound represented by formula (I-1-b) was added, followed by temperature rise to 50° C. and further stirring at 50° C. for 2 hours. To the reaction mixture thus obtained, 2.50 parts of a compound represented by formula (I-1-c) was added, followed by stirring at 50° C. for 10 hours. The reaction mixture thus obtained was cooled to 23° C. and then 25 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. To the organic layer thus obtained, 25 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 3 parts of acetonitrile and 30 parts of tert-butyl methyl ether were added to the concentrated residue, and after stirring at 23° C. for 30 minutes, the supernatant was removed, followed by concentration to obtain 9.91 parts of a salt represented by formula (I-1653).

MASS (ESI (+) Spectrum): M⁺ 782.9

MASS (ESI (−) Spectrum): M⁻ 407.1

Example 3: Synthesis of Salt Represented by Formula (I-1654)

2.64 Parts of a compound represented by formula (I-2-c) and 50 parts of chloroform were mixed, and after stirring at 23° C. for 30 minutes, 1.62 parts of a compound represented by formula (I-1-b) was added, followed by temperature rise to 50° C. and further stirring at 50° C. for 2 hours. To the reaction mixture thus obtained, 9.44 parts of a salt represented by formula (I-1654-a) was added, followed by stirring at 50° C. for 10 hours. The reaction mixture thus obtained was cooled to 23° C. and then 25 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. To the organic layer thus obtained, 25 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 3 parts of acetonitrile and 30 parts of tert-butyl methyl ether were added to the concentrated residue, and after stirring at 23° C. for 30 minutes, the supernatant was removed, followed by concentration to obtain 10.23 parts of a salt represented by formula (I-1654).

MASS (ESI (+) Spectrum): M⁺ 782.9

MASS (ESI (−) Spectrum): M⁻ 407.1

Example 4: Synthesis of Salt Represented by Formula (I-1667)

9.00 Parts of a salt represented by formula (I-1667-a) and 50 parts of chloroform were mixed, and after stirring at 23° C. for 30 minutes, 1.62 parts of a compound represented by formula (I-1-b) was added, followed by temperature rise to 50° C. and further stirring at 50° C. for 2 hours. To the reaction mixture thus obtained, 2.50 parts of a compound represented by formula (I-1-c) was added, followed by stirring at 50° C. for 10 hours. The reaction mixture thus obtained was cooled to 23° C. and then 25 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. To the organic layer thus obtained, 25 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 3 parts of acetonitrile and 30 parts of tert-butyl methyl ether were added to the concentrated residue, and after stirring at 23° C. for 30 minutes, the supernatant was removed, followed by concentration to obtain 8.12 parts of a salt represented by formula (I-1667).

MASS (ESI (+) Spectrum): M⁺ 724.9

MASS (ESI (−) Spectrum): M⁻ 407.1

Example 5: Synthesis of Salt Represented by Formula (I-1737)

13.20 Parts of a salt represented by formula (I-1737-a) and 50 parts of chloroform were mixed, and after stirring at 23° C. for 30 minutes, 1.62 parts of a compound represented by formula (I-1-b) was added, followed by temperature rise to 50° C. and further stirring at 50° C. for 2 hours. To the reaction mixture thus obtained, 2.50 parts of a compound represented by formula (I-1-c) was added, followed by stirring at 50° C. for 10 hours. The reaction mixture thus obtained was cooled to 23° C. and then 25 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. To the organic layer thus obtained, 25 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 3 parts of acetonitrile and 30 parts of tert-butyl methyl ether were added to the concentrated residue, and after stirring at 23° C. for 30 minutes, the supernatant was removed, followed by concentration to obtain 12.65 parts of a salt represented by formula (I-1737).

MASS (ESI (+) Spectrum): M⁺ 1144.7

MASS (ESI (−) Spectrum): M⁻ 407.1

Example 6: Synthesis of Salt Represented by Formula (I-2158)

2.64 Parts of a compound represented by formula (I-2-c) and 50 parts of chloroform were mixed, and after stirring at 23° C. for 30 minutes, 1.62 parts of a compound represented by formula (I-1-b) was added, followed by temperature rise to 50° C. and further stirring at 50° C. for 2 hours. To the reaction mixture thus obtained, 9.44 parts of a salt represented by formula (I-2158-a) was added, followed by stirring at 50° C. for 10 hours. The reaction mixture thus obtained was cooled to 23° C. and then 25 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. To the organic layer thus obtained, 25 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 3 parts of acetonitrile and 30 parts of tert-butyl methyl ether were added to the concentrated residue, and after stirring at 23° C. for 30 minutes, the supernatant was removed, followed by concentration to obtain 11.19 parts of a salt represented by formula (I-2158).

MASS (ESI (+) Spectrum): M⁺ 782.9

MASS (ESI (−) Spectrum): M⁻ 407.1

Example 7: Synthesis of Salt Represented by Formula (I-2214)

2.64 Parts of a compound represented by formula (1-2-c) and 50 parts of chloroform were mixed, and after stirring at 23° C. for 30 minutes, 1.62 parts of a compound represented by formula (I-1-b) was added, followed by temperature rise to 50° C. and further stirring at 50° C. for 2 hours. To the reaction mixture thus obtained, 10.93 parts of a salt represented by formula (I-2214-a) was added, followed by stirring at 50° C. for 10 hours. The reaction mixture thus obtained was cooled to 23° C. and then 25 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. To the organic layer thus obtained, 25 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 3 parts of acetonitrile and 30 parts of tert-butyl methyl ether were added to the concentrated residue, and after stirring at 23° C. for 30 minutes, the supernatant was removed, followed by concentration to obtain 12.86 parts of a salt represented by formula (I-2214).

MASS (ESI (+) Spectrum): M⁺ 931.0

MASS (ESI (−) Spectrum): M⁻ 407.1

Example 8: Synthesis of Salt Represented by Formula (I-1962)

2.64 Parts of a compound represented by formula (I-2-c) and 50 parts of chloroform were mixed, and after stirring at 23° C. for 30 minutes, 1.62 parts of a compound represented by formula (I-1-b) was added, followed by temperature rise to 50° C. and further stirring at 50° C. for 2 hours. To the reaction mixture thus obtained, 13.06 parts of a salt represented by formula (I-1962-a) was added, followed by stirring at 50° C. for 10 hours. The reaction mixture thus obtained was cooled to 23° C. and then 25 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. To the organic layer thus obtained, 25 parts of ion-exchanged water was added, and after stirring at 23° C. for 30 minutes, the organic layer was isolated through separation. This water washing operation was repeated five times. The organic layer thus obtained was concentrated and then 3 parts of acetonitrile and 30 parts of tert-butyl methyl ether were added to the concentrated residue, and after stirring at 23° C. for 30 minutes, the supernatant was removed, followed by concentration to obtain 14.08 parts of a salt represented by formula (I-1962).

MASS (ESI (+) Spectrum): M⁺ 1144.7

MASS (ESI (−) Spectrum): M⁻ 407.1

Synthesis of Resin

Compounds (monomers) used in synthesis of a resin (A) are shown below. Hereinafter, these compounds are referred to as “monomer (a1-1-3)” according to the formula number.

Example 9 [Synthesis of Resin A¹]

Using a monomer (a1-1-3), a monomer (a1-2-6), a monomer (a2-1-3), a monomer (a3-4-2), 4-acetoxystyrene and a monomer (I-561) as monomers, these monomers were mixed in a molar ratio of 20:35:3:12:25:5 [monomer (a1-1-3):monomer (a1-2-6):monomer (a2-1-3):monomer (a3-4-2):4-acetoxystyrene:monomer (I-561)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) as initiators were added in the amounts of 1.2 mol % and 3.6 mol % based on the amount of all monomers, followed by heating at 73° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous 25% tetramethylammonium hydroxide solution was added, followed by stirring for 12 hours and further isolation through separation. The organic layer thus recovered was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin A¹ having a weight-average molecular weight of about 5.3×10³ in a yield of 60%. This resin A¹ has the following structural units.

Example 10 [Synthesis of Resin A²]

Using a monomer (a1-1-3), a monomer (a1-2-6), a monomer (a2-1-3), a monomer (a3-4-2), 4-acetoxystyrene and a monomer (I-1653) as monomers, these monomers were mixed in a molar ratio of 20:35:3:12:25:5 [monomer (a1-1-3):monomer (a1-2-6):monomer (a2-1-3):monomer (a3-4-2):4-acetoxystyrene:monomer (I-1653)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) as initiators were added in the amounts of 1.2 mol % and 3.6 mol % based on the amount of all monomers, followed by heating at 73° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous 25% tetramethylammonium hydroxide solution was added, followed by stirring for 12 hours and further isolation through separation. The organic layer thus recovered was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin A² having a weight-average molecular weight of about 5.4×10³ in a yield of 63%. This resin A² has the following structural units.

Example 11 [Synthesis of Resin A³]

Using a monomer (a1-1-3), a monomer (a1-2-6), a monomer (a2-1-3), a monomer (a3-4-2), 4-acetoxystyrene and a monomer (I-1654) as monomers, these monomers were mixed in a molar ratio of 20:35:3:12:25:5 [monomer (a1-1-3):monomer (a1-2-6):monomer (a2-1-3):monomer (a3-4-2):4-acetoxystyrene:monomer (I-1654)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) as initiators were added in the amounts of 1.2 mol % and 3.6 mol % based on the amount of all monomers, followed by heating at 73° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous 25% tetramethylammonium hydroxide solution was added, followed by stirring for 12 hours and further isolation through separation. The organic layer thus recovered was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin A³ having a weight-average molecular weight of about 5.5×10³ in a yield of 65%. This resin A³ has the following structural units.

Example 12 [Synthesis of Resin A⁴]

Using a monomer (a1-1-3), a monomer (a1-2-6), a monomer (a2-1-3), a monomer (a3-4-2), 4-acetoxystyrene and a monomer (I-1667) as monomers, these monomers were mixed in a molar ratio of 20:35:3:12:25:5 [monomer (a1-1-3):monomer (a1-2-6):monomer (a2-1-3):monomer (a3-4-2):4-acetoxystyrene:monomer (I-1667)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) as initiators were added in the amounts of 1.2 mol % and 3.6 mol % based on the amount of all monomers, followed by heating at 73° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous 25% tetramethylammonium hydroxide solution was added, followed by stirring for 12 hours and further isolation through separation. The organic layer thus recovered was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin A⁴ having a weight-average molecular weight of about 5.3×10³ in a yield of 60%. This resin A⁴ has the following structural units.

Example 13 [Synthesis of Resin A⁵]

Using a monomer (a1-1-3), a monomer (a1-2-6), a monomer (a2-1-3), a monomer (a3-4-2), 4-acetoxystyrene and a monomer (I-1737) as monomers, these monomers were mixed in a molar ratio of 20:35:3:12:25:5 [monomer (a1-1-3):monomer (a1-2-6):monomer (a2-1-3):monomer (a3-4-2):4-acetoxystyrene:monomer (I-1737)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) as initiators were added in the amounts of 1.2 mol % and 3.6 mol % based on the amount of all monomers, followed by heating at 73° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous 25% tetramethylammonium hydroxide solution was added, followed by stirring for 12 hours and further isolation through separation. The organic layer thus recovered was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin A⁵ having a weight-average molecular weight of about 5.4×10³ in a yield of 63%. This resin A⁵ has the following structural units.

Example 14 [Synthesis of Resin A⁶]

Using a monomer (a1-1-3), a monomer (a1-2-6), a monomer (a2-1-3), a monomer (a3-4-2), 3,4-diacetoxystyrene and a monomer (I-1654) as monomers, these monomers were mixed in a molar ratio of 20:35:3:12:25:5 [monomer (a1-1-3):monomer (a1-2-6):monomer (a2-1-3):monomer (a3-4-2):3,4-diacetoxystyrene:monomer (I-1654)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) as initiators were added in the amounts of 1.2 mol % and 3.6 mol % based on the amount of all monomers, followed by heating at 73° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous 25% tetramethylammonium hydroxide solution was added, followed by stirring for 12 hours and further isolation through separation. The organic layer thus recovered was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin A⁶ having a weight-average molecular weight of about 5.5×10³ in a yield of 64%. This resin A⁶ has the following structural units.

Example 15 [Synthesis of Resin A⁷]

Using a monomer (a1-2-6), a monomer (a2-1-3), a monomer (a3-4-2), 4-acetoxystyrene and a monomer (I-1654) as monomers, these monomers were mixed in a molar ratio of 55:3:12:25:5 [monomer (a1-2-6):monomer (a2-1-3):monomer (a3-4-2):4-acetoxystyrene:monomer (I-1654)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) as initiators were added in the amounts of 1.2 mol % and 3.6 mol % based on the amount of all monomers, followed by heating at 73° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous 25% tetramethylammonium hydroxide solution was added, followed by stirring for 12 hours and further isolation through separation. The organic layer thus recovered was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin A⁷ having a weight-average molecular weight of about 5.4×10³ in a yield of 86%. This resin A⁷ has the following structural units.

Example 16 [Synthesis of Resin A⁸]

Using a monomer (a1-2-6), a monomer (a2-1-3), a monomer (a3-4-2), 3,4-diacetoxystyrene and a monomer (I-1654) as monomers, these monomers were mixed in a molar ratio of 55:3:12:25:5 [monomer (a1-2-6):monomer (a2-1-3):monomer (a3-4-2):3,4-diacetoxystyrene:monomer (I-1654)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) as initiators were added in the amounts of 1.2 mol % and 3.6 mol % based on the amount of all monomers, followed by heating at 73° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous 25% tetramethylammonium hydroxide solution was added, followed by stirring for 12 hours and further isolation through separation. The organic layer thus recovered was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin A⁸ having a weight-average molecular weight of about 5.5×10³ in a yield of 80%. This resin A⁸ has the following structural units.

Example 17 [Synthesis of Resin A⁹]

Using a monomer (a1-2-6), a monomer (a2-1-3), a monomer (a3-4-2), 3-acetoxystyrene and a monomer (I-1654) as monomers, these monomers were mixed in a molar ratio of 55:3:12:25:5 [monomer (a1-2-6):monomer (a2-1-3):monomer (a3-4-2):3-acetoxystyrene:monomer (I-1654)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) as initiators were added in the amounts of 1.2 mol % and 3.6 mol % based on the amount of all monomers, followed by heating at 73° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous 25% tetramethylammonium hydroxide solution was added, followed by stirring for 12 hours and further isolation through separation. The organic layer thus recovered was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin A⁹ having a weight-average molecular weight of about 5.6×10³ in a yield of 78%. This resin A⁹ has the following structural units.

Example 18 [Synthesis of Resin A¹⁰]

Using a monomer (a1-2-6), a monomer (a2-1-3), a monomer (a3-4-2), 4-acetoxystyrene and a monomer (I-2158) as monomers, these monomers were mixed in a molar ratio of 55:3:12:25:5 [monomer (a1-2-6):monomer (a2-1-3):monomer (a3-4-2):4-acetoxystyrene:monomer (I-2158)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) as initiators were added in the amounts of 1.2 mol % and 3.6 mol % based on the amount of all monomers, followed by heating at 73° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous 25% tetramethylammonium hydroxide solution was added, followed by stirring for 12 hours and further isolation through separation. The organic layer thus recovered was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin A¹⁰ having a weight-average molecular weight of about 5.7×10³ in a yield of 88%. This resin A¹⁰ has the following structural units.

Example 19 [Synthesis of Resin A¹¹]

Using a monomer (a1-2-6), a monomer (a2-1-3), a monomer (a3-4-2), 4-acetoxystyrene and a monomer (I-2214) as monomers, these monomers were mixed in a molar ratio of 55:3:12:25:5 [monomer (a1-2-6):monomer (a2-1-3):monomer (a3-4-2):4-acetoxystyrene:monomer (I-2214)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) as initiators were added in the amounts of 1.2 mol % and 3.6 mol % based on the amount of all monomers, followed by heating at 73° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous 25% tetramethylammonium hydroxide solution was added, followed by stirring for 12 hours and further isolation through separation. The organic layer thus recovered was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin A¹¹ having a weight-average molecular weight of about 5.8×10³ in a yield of 86%. This resin A¹¹ has the following structural units.

Example 20 [Synthesis of Resin A¹²]

Using a monomer (a1-2-6), a monomer (a2-1-3), a monomer (a3-4-2), 4-acetoxystyrene and a monomer (I-1962) as monomers, these monomers were mixed in a molar ratio of 55:3:12:25:5 [monomer (a1-2-6):monomer (a2-1-3):monomer (a3-4-2):4-acetoxystyrene:monomer (I-1962)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) as initiators were added in the amounts of 1.2 mol % and 3.6 mol % based on the amount of all monomers, followed by heating at 73° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous 25% tetramethylammonium hydroxide solution was added, followed by stirring for 12 hours and further isolation through separation. The organic layer thus recovered was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin A¹² having a weight-average molecular weight of about 5.6×10³ in a yield of 82%. This resin A¹² has the following structural units.

Example 21 [Synthesis of Resin A¹³]

Using a monomer (a1-2-6), a monomer (a2-1-3), a monomer (a3-4-2), 4-acetoxystyrene and a monomer (I-2158) as monomers, these monomers were mixed in a molar ratio of 50:3:10:25:12 [monomer (a1-2-6):monomer (a2-1-3):monomer (a3-4-2):4-acetoxystyrene:monomer (I-2158)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) as initiators were added in the amounts of 1.2 mol % and 3.6 mol % based on the amount of all monomers, followed by heating at 73° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous 25% tetramethylammonium hydroxide solution was added, followed by stirring for 12 hours and further isolation through separation. The organic layer thus recovered was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin A¹³ having a weight-average molecular weight of about 5.6×10³ in a yield of 77%. This resin A¹³ has the following structural units.

Synthesis Example 1[Synthesis of Resin AX1]

Using a monomer (a1-1-3), a monomer (a1-2-6), a monomer (a2-1-3), a monomer (a3-4-2), 4-acetoxystyrene and a monomer (IX-1) as monomers, these monomers were mixed in a molar ratio of 20:35:3:12:25:5 [monomer a(a1-1-3):monomer (a1-2-6):monomer (a2-1-3):monomer (3-4-2):4-acetoxystyrene:monomer (IX-1)], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) as initiators were added in the amounts of 1.2 mol % and 3.6 mol % based on the amount of all monomers, followed by heating at 73° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous 25% tetramethylammonium hydroxide solution was added, followed by stirring for 12 hours and further isolation through separation. The organic layer thus recovered was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin AX1 having a weight-average molecular weight of about 5.4×10³ in a yield of 63%. This resin AX1 has the following structural units.

Synthesis Example 2[Synthesis of Resin AA1]

Using a monomer (a1-1-3), a monomer (a1-2-6), a monomer (a2-1-3), a monomer (a3-4-2) and 4-acetoxystyrene as monomers, these monomers were mixed in a molar ratio of 20:35:3:15:27 [monomer (a1-1-3):monomer (a1-2-6):monomer (a2-1-3):monomer (a3-4-2):4-acetoxystyrene], and then this monomer mixture was mixed with methyl isobutyl ketone in the amount of 1.5 mass times the total mass of all monomers. To the mixture thus obtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) as initiators were added in the amounts of 1.2 mol % and 3.6 mol % based on the amount of all monomers, followed by heating at 73° C. for about 5 hours. Thereafter, to the polymerization reaction solution thus obtained, an aqueous 25% tetramethylammonium hydroxide solution was added, followed by stirring for 12 hours and further isolation through separation. The organic layer thus recovered was poured into a large amount of n-heptane to precipitate a resin, followed by filtration and recovery to obtain a resin AA1 having a weight-average molecular weight of about 5.5×10³ in a yield of 68%. This resin AA1 has the following structural units.

<Preparation of Resist Composition>

As shown in Table 2, the following components were mixed and the mixture thus obtained was filtered through a fluororesin filter having a pore diameter of 0.2 μm to prepare resist compositions.

TABLE 2
Resist		Acid		Quencher
composition	Resin	generator	Salt (I)	(C)	PB/PEB
Composition 1	AA1 =	—	I-561 =	C1 =	100° C./
	10 parts		1.5 parts	0.35 part	130° C.
Composition 2	AA1 =	—	I-1653 =	C1 =	100° C./
	10 parts		1.5 parts	0.35 part	130° C.
Composition 3	AA1 =	—	I-1654 =	C1 =	100° C./
	10 parts		1.5 parts	0.35 part	130° C.
Composition 4	AA1 =	—	I-1667 =	C1 =	100° C./
	10 parts		1.5 parts	0.35 part	130° C.
Composition 5	AA1 =	—	I-1737 =	C1 =	100° C./
	10 parts		1.5 parts	0.35 part	130° C.
Composition 6	A3 =	B1-25 =	—	C1 =	100° C./
	10 parts	0.5 part		0.35 part	130° C.
Composition 7	A3 =	—	I-1654 =	C1 =	100° C./
	10 parts		0.5 part	0.35 part	130° C.
Composition 8	A3 =	—	—	C1 =	100° C./
	10 parts			0.35 part	130° C.
Composition 9	A1 =	B1-25 =	—	C1 =	100° C./
	10 parts	0.5 part		0.35 part	130° C.
Composition 10	A2 =	B1-25 =	—	C1 =	100° C./
	10 parts	0.5 part		0.35 part	130° C.
Composition 11	A4 =	B1-25 =	—	C1 =	100° C./
	10 parts	0.5 part		0.35 part	130° C.
Composition 12	A5 =	B1-25 =	—	C1 =	100° C./
	10 parts	0.5 part		0.35 part	130° C.
Composition 13	A6 =	B1-25 =	—	C1 =	100° C./
	10 parts	0.5 part		0.35 part	130° C.
Composition 14	A7 =	B1-25 =	—	C1 =	100° C./
	10 parts	0.5 part		0.35 part	130° C.
Composition 15	A8 =	B1-25 =	—	C1 =	100° C./
	10 parts	0.5 part		0.35 part	130° C.
Composition 16	A9 =	B1-25 =	—	C1 =	100° C./
	10 parts	0.5 part		0.35 part	130° C.
Composition 17	A2 =	—	I-1653 =	C1 =	100° C./
	10 parts		0.5 part	0.35 part	130° C.
Composition 18	A2 =	—	—	C1 =	100° C./
	10 parts			0.35 part	130° C.
Composition 19	A4 =	—	I-1667 =	C1 =	100° C./
	10 parts		0.5 part	0.35 part	130° C.
Composition 20	A4 =	—	—	C1 =	100° C./
	10 parts			0.35 part	130° C.
Composition 21	A5 =	—	I-1737 =	C1 =	100° C./
	10 parts		0.5 part	0.35 part	130° C.
Composition 22	A5 =	—	—	C1 =	100° C./
	10 parts			0.35 part	130° C.
Composition 23	A9 =	B1-25 =	—	C1 =	100° C./
	10 parts	0.5 part		0.35 part	130° C.
Composition 24	A10 =	B1-25 =	—	C1 =	100° C./
	10 parts	0.5 part		0.35 part	130° C.
Composition 25	A11 =	B1-25 =	—	C1 =	100° C./
	10 parts	0.5 part		0.35 part	130° C.
Composition 26	A12 =	B1-25	—	C1 =	100° C./
	10 parts	0.5 part		0.35 part	130° C.
Composition 27	A13 =	B1-25 =	—	C1 =	100° C./
	10 parts	0.5 part		0.35 part	130° C.
Composition 28	A12 =	—		C1 =	100° C./
	10 parts			0.35 part	130° C.
Composition 29	A12 =	—	I-1962 =	C1 =	100° C./
	10 parts		0.5 part	0.35 part	130° C.
Composition 30	A13 =	—	—	C1 =	100° C./
	10 parts			0.35 part	130° C.
Composition 31	—	—	I-1962 =	C1 =	100° C./
			10 parts	0.35 part	130° C.
Comparative	AA1 =	IX-1 =	—	C1 =	100° C./
Composition 1	10 parts	1.5 parts		0.35 part	130° C.
Comparative	AX1	B1-25 =	—	C1 =	100° C./
Composition 2	10 parts	0.5 part		0.35 part	130° C.
Comparative	AX1 =	IX-1 =	—	C1 =	100° C./
Composition 3	10 parts	0.5 part		0.35 part	130° C.
Comparative	AX1 =	—	—	C1 =	100° C./
Composition 4	10 parts			0.35 part	130° C.

<Resin>

A¹ to A¹³, AX1, AA1: Resin A¹ to Resin A¹³, Resin AX1, Resin AA1

<Salt (I)>

• • I-561: Salt represented by Formula (I-561)
  • I-1653: Salt represented by Formula (I-1653)
  • I-1654: Salt represented by Formula (I-1654)
  • I-1667: Salt represented by Formula (I-1667)
  • I-1737: Salt represented by Formula (I-1737)
  • I-1962: Salt represented by Formula (I-1962)

<Acid Generator>

B1-25: Salt represented by Formula (B1-25); synthesized by the method mentioned in JP 2011-126869 A

IX-1: synthesized by the method shown in JP 2007-197718 A

<Quencher (C)>

C1: synthesized by the method mentioned in JP 2011-39502 A

<Solvent>

Compositions 1 to 25, Comparative Compositions 1 to 4

Propylene glycol monomethyl ether acetate 400 parts
Propylene glycol monomethyl ether 100 parts
γ-Butyrolactone                  5 parts

Compositions 26 to 31

	Methyl 2-hydroxyisobutyrate	400	parts
	Propylene glycol monomethyl ether	100	parts
	γ-Butyrolactone	5	parts

(Evaluation of Exposure of Resist Composition with Electron Beam: Development with Organic Solvent)

Each 6 inch-diameter silicon wafer was treated with hexamethyldisilazane on a direct hot plate at 90° C. for 60 seconds. A resist composition was spin-coated on the silicon wafer in such a manner that the thickness of the composition layer became 0.04 μm. Then, the coated silicon wafer was prebaked on the direct hot plate at the temperature shown in the column “PB” of Table 2 for 60 seconds to form a composition layer. Using an electron-beam direct-write system (“ELS-F125 125 keV”, manufactured by ELIONIX INC.), line and space patterns (pitch of 36 to 72 nm/line width of 18 to 36 nm) were directly written on the composition layer formed on the wafer were directly written on the composition layer formed on the while changing the exposure dose stepwise.

After exposure, post-exposure baking was performed on the hot plate at the temperature shown in the column “PEB” of Table 2 for 60 second. Next, the composition layer on this silicon wafer was developed with butyl acetate (manufactured by Tokyo Chemical Industry Co., Ltd.) as a developer at 23° C. for 20 seconds using the dynamic dispensing method to obtain resist patterns.

In the resist patterns thus obtained, effective sensitivity was defined as the exposure dose at which a ratio of the line width to the space width of 36 nm-line and space patterns with a pitch of became 1:1.

<Evaluation of Resolution>

In the effective sensitivity, the resist pattern was observed by a scanning electron microscope, and the minimum line width to be resolved was defined as the resolution. The results are shown in Table 3. The resolution (nm) is shown.

	TABLE 3
		Resist composition	Resolution
	Example 22	Composition 1	18 nm
	Example 23	Composition 2	18 nm
	Example 24	Composition 3	18 nm
	Example 25	Composition 4	18 nm
	Example 26	Composition 5	18 nm
	Example 27	Composition 6	18 nm
	Example 28	Composition 7	18 nm
	Example 29	Composition 8	18 nm
	Example 30	Composition 9	18 nm
	Example 31	Composition 10	18 nm
	Example 32	Composition 11	18 nm
	Example 33	Composition 12	18 nm
	Example 34	Composition 13	18 nm
	Example 35	Composition 14	18 nm
	Example 36	Composition 15	18 nm
	Example 37	Composition 16	18 nm
	Example 38	Composition 17	18 nm
	Example 39	Composition 18	18 nm
	Example 40	Composition 19	18 nm
	Example 41	Composition 20	18 nm
	Example 42	Composition 21	18 nm
	Example 43	Composition 22	18 nm
	Example 44	Composition 23	18 nm
	Example 45	Composition 24	18 nm
	Example 46	Composition 25	18 nm
	Example 47	Composition 26	18 nm
	Example 48	Composition 27	18 nm
	Example 49	Composition 28	18 nm
	Example 50	Composition 29	18 nm
	Example 51	Composition 30	18 nm
	Example 52	Composition 31	18 nm
	Comparative Example 1	Comparative	28 nm
		Composition 1
	Comparative Example 2	Comparative	26 nm
		Composition 2
	Comparative Example 3	Comparative	26 nm
		Composition 3
	Comparative Example 4	Comparative	28 nm
		Composition 4

As is apparent from the above results, a salt of the present invention and a resist composition including the salt exhibit satisfactory resolution.

A resist composition including a salt of the present invention exhibits satisfactory resolution, and is therefore useful for fine processing of semiconductors.

Claims

1. A salt represented by formula (I):

2. The salt according to claim 1, wherein A1 is ***—X01-L01- or ***-L01-X01—,A2 is ***—X02-L02- or ***-L02-X02—,X01 and X02 each independently represent —O—, —CO—, —S— or —SO2—,L01 and L02 each independently represent a single bond or a hydrocarbon group having 1 to 18 carbon atoms, the hydrocarbon group may have a substituent, and —CH2— included in the hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO2—, and*** represents a bonding site to the benzene ring to which R1 or R2 is bonded.

3. The salt according to claim 2, wherein X01 and X02 are each independently —O— or —S—.

4. The salt according to claim 2, wherein L01 and L02 are each independently a single bond or an alkanediyl group having 1 to 6 carbon atoms (—CH2— included in the alkanediyl group may be replaced by —O— or —CO—).

5. The salt according to claim 1, wherein R1 and R2 are each independently a hydroxy group, —O—R10 or —O-L1-CO—O—R10.

6. The salt according to claim 1, wherein the acid-labile group as for R10 is a group represented by formula (1a) or a group represented by formula (2a):

7. The salt according to claim 1, wherein Yb1 is a single bond or an alicyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent (—CH2— included in the alicyclic hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO2—).

8. The salt according to claim 7, wherein Yb1 is a cyclohexanediyl group, an adamantanediyl group, a norbornanediyl group, an adamantanelactonediyl group or a norbornanelactonediyl group.

9. The salt according to claim 1, wherein X10 is a single bond or a group represented by any one of formula (X10-1) to formula (X10-10):

10. The salt according to claim 9, wherein X10 is a single bond or a group represented by any one of formula (X10-1), formula (X10-5′) and formula (X10-6′):

11. The salt according to claim 1, wherein L10 is a single bond, an alkanediyl group having 1 to 6 carbon atoms (in which —CH2— included in the alkanediyl group may be replaced by —O— or —CO—), a cyclic hydrocarbon group having 3 to 18 carbon atoms (in which the cyclic hydrocarbon group may have a substituent, and —CH2— included in the cyclic hydrocarbon group may be replaced by —O—, —S—, —SO2— or —CO—) or a group obtained by combining an alkanediyl group having 1 to 6 carbon atoms with a cyclic hydrocarbon group having 3 to 18 carbon atoms (in which the cyclic hydrocarbon group may have a substituent, —CH2— included in the alkanediyl group may be replaced by —O— or —CO—, and —CH2— included in the cyclic hydrocarbon group may be replaced by —O—, —S—, —SO2— or —CO—).

12. An acid generator comprising the salt according to claim 1 or a structural unit derived from the salt according to claim 1.

13. A resin including a structural unit derived from the salt according to claim 1.

14. A resist composition comprising the acid generator according to claim 12.

15. The resist composition according to claim 14, comprising the salt represented by formula (I), and a resin including a structural unit having an acid-labile group.

16. The resist composition according to claim 14, comprising a resin including the structural unit derived from the salt represented by formula (I), wherein the resin including a structural unit derived from the salt represented by formula (I) further includes a structural unit having an acid-labile group.

17. The resist composition according to claim 16, further comprising the salt represented by formula (I).

18. The resist composition according to claim 15, wherein the structural unit having an acid-labile group includes at least one selected from the group consisting of a structural unit represented by formula (a1-0), a structural unit represented by formula (a1-1) and a structural unit represented by formula (a1-2):

19. The resist composition according to claim 15, wherein the resin including a structural unit having an acid-labile group further includes a structural unit represented by formula (a2-A):

20. The resist composition according to claim 14, further comprising a salt represented by formula (B1):

21. The resist composition according to claim 14, further comprising a salt generating an acid having an acidity lower than that of an acid generated from the salt represented by formula (I).

22. A method for producing a resist pattern, which comprises: (1) a step of applying the resist composition according to claim 14 on a substrate,(2) a step of drying the applied composition to form a composition layer,(3) a step of exposing the composition layer,(4) a step of heating the exposed composition layer, and(5) a step of developing the heated composition layer.