Resist composition

Abstract

A resist composition which contains a resin (A1) which has a structural unit represented by formula (I), a structural unit represented by formula (II) and a structural unit having an acid-labile group, and an acid generator:

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Application No. 2015-128326 filed on Jun. 26, 2015. The entire disclosures of Japanese Application No. 2015-128326 is incorporated hereinto by reference.

BACKGROUND

1. Field of the Invention

The disclosure relates to a resist composition.

2. Related Art

A resist composition which includes a resin having a combination of structural units below is described in Patent document of JP2001-278919A.

A resist composition which includes a resin having a combination of structural units below is described in Patent document of JP2005-208509A.

SUMMARY

The disclosure provides following inventions of <1> to <4>.

<1> A resist composition which contains

a resin (A1) which has

• • a structural unit represented by formula (I),
  • a structural unit represented by formula (II) and
  • a structural unit having an acid-labile group, and

an acid generator:

wherein R¹ represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that may have a halogen atom,

R^a25 in each occurrence represents a carboxy group, a cyano group or a C₁ to C₄ aliphatic hydrocarbon group,

A¹ represents a single bond, *-A²-O—, *-A²-CO—O—, *-A²-CO—O— A³-CO—O— or *-A²-O—CO— A³-O— where * represents a binding position to an oxygen atom,

A² and A³ independently represents a C₁ to C₆ alkanediyl group, and

w1 represents an integer of 0 to 8,

wherein R² represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that may have a halogen atom,

L¹ represents a single bond or *-L²-CO—O-(L³-CO—O)_g— where * represents a binding position to an oxygen atom,

L² and L³ independently represent a C₁ to C₁₂ divalent hydrocarbon group,

g represents 0 or 1, and

R3 represents a C1 to C12 linear or branched alkyl group except for a tertiary alkyl group.

<2> The resist composition according to <1>, wherein

L¹ is a single bond.

<3> The resist composition according to <1> or <2>, wherein

R³ is a C2 to C8 linear alkyl group.

<4> The resist composition according to any one of <1> to <3> further comprising a resin (A2) which has a structural unit having a fluorine atom and no structural unit having an acid-labile group.

<5> The resist composition according to any one of <1> to <4>, wherein

a mole ratio of the structural unit (II) is 0.5 to 15% by mole with respect to the total structural units of the resin (A1).

<6> A method for producing a resist pattern comprising steps (1) to (4);

(1) applying the resist composition according to any one of <1> to <5> onto a substrate;

(2) drying the applied composition to form a composition layer;

(3) exposing the composition layer; and

(4) developing the exposed composition layer.

DETAILED DESCRIPTION OF DISCLOSURE

“(Meth)acrylic monomer” means a monomer having a structure of “CH2═CH—CO—” or “CH2=C(CH3)-CO—”, as well as “(meth)acrylate” and “(meth)acrylic acid” mean “an acrylate or methacrylate” and “an acrylic acid or methacrylic acid,” respectively. Herein, chain structure groups such as a chain aliphatic hydrocarbon group include those having a linear structure and those having a branched structure. An aromatic hydrocarbon group includes a group having an aromatic ring and a chain hydrocarbon group bonded to the aromatic ring. The indefinite articles “a” and “an” are taken as the same meaning as “one or more”.

In the specification, the term “solid components” means components other than solvents in a resist composition.

<Resist Composition>

The resist composition of the disclosure contains a resin (A1) and an acid generator (which is sometimes referred to as “acid generator (B)”).

The resist composition may further contain a resin which has a structural unit having a fluorine atom and no structural unit having an acid-labile group, which is sometimes referred to as “resin (A2)”.

Further, the resist composition preferably contains a quencher (which is sometimes referred to as “quencher (C)”) and/or a solvent (which is sometimes referred to as “solvent (E)”) in addition to the resin (A1) and the acid generator (B).

<Resin (A1)>

The resin (A1) has

a structural unit represented by formula (I) (which is sometimes referred to as “structural unit (I)”),

a structural unit represented by formula (II) (which is sometimes referred to as “structural unit (II)”) and

a structural unit having an acid-labile group (which is sometimes referred to as “structural unit (a1)”).

Here the “acid-labile group” means a group having a leaving group capable of detaching by contacting with an acid to thereby form a hydrophilic group such as a hydroxy or carboxy group.

The resin (A1) further has a structural unit having no acid-labile group (which is sometimes referred to as “structural unit (s)”).

<Structural Unit (I)>

The structural unit (I) is a structural unit represented by formula (I).

In the formula, R¹ represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that may have a halogen atom,

R^a25 in each occurrence represents a carboxy group, a cyano group or a C₁ to C₄ aliphatic hydrocarbon group,

A¹ represents a single bond, *-A²-O—, *-A²-CO—O—, *-A²-CO—O— A³-CO—O— or *-A²-O—CO— A³-O— where * represents a binding position to an oxygen atom,

A² and A³ independently represents a C₁ to C₆ alkanediyl group, and

w1 represents an integer of 0 to 8.

Examples of the halogen atom for R¹ include fluorine, chlorine, bromine and iodine atoms.

Examples of the alkyl group for R¹ include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl and n-hexyl groups, preferably a C₁ to C₄ alkyl group, more preferably a methyl group and an ethyl group.

Examples of the alkyl group having a halogen atom for R¹ include trifluoromethyl, perfluoroethyl, perfluoropropyl, perfluoro-isopropyl, perfluorobutyl, perfluoro-sec-butyl, perfluoro-tert-butyl, perfluoropentyl, perfluorohexyl, tricloromethyl, tribromomethyl and triiodomethyl groups.

R¹ is preferably a hydrogen atom or a C₁ to C₄ alkyl group, 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 aliphatic hydrocarbon group for R^a25 include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl and tert-butyl groups.

Examples of the alkanediyl group for A² and A³ include methylene, ethylene, propane-1,3-diyl, propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, butane-1,3-diyl, 2-methylpropane-1,3-diyl, 2-methylpropane-1,2-diyl, pentane-1,4-diyl and 2-methylbutane-1,4-diyl groups.

A¹ is preferably a single bond, or *-A²-CO—O—, and more preferably a single bond, —CH₂—CO—O— or —C₂H₄—CO—O—.

The binding position of A¹ to the homo-adamantane ring may be any of positions such as 1-position to 9-position below, and preferably 2-position.

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

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

Examples of the structural unit (I) include the structural units represented by the formula (I-1) to formula (I-12) and these in which a methyl group corresponding to R¹ has been replaced by a hydrogen atom. Among them, the structural unis represented by formula (I-1) to formula (I-6) are preferred.

The structural unit (I) is derived from a monomer represented by formula (I′) (which is sometimes referred to as “monomer (I′)”).

In the formula, R¹, A¹, R^a25 and w1 are as defined above.

The monomer (I′) represented by formula (I′-1), that is the monomer of formula (I′)-A¹ is *—CH₂—CO—O— where * is a binding position to —CO—O— can be produced by reacting a compound represented by the formula (I′-1-a) with a compound represented by the formula (I′-1-b) in a solvent.

In the formulae, R¹, R^a25 and w1 are as defined above.

Preferred examples of the solvent include methylene chloride, tetrahydrofuran and acetonitrile.

The reaction can be conducted at temperature of preferably −5° C. to 80° C., for 0.5 to 24 hours.

The compound represented by formula (I′-1-a) can be produced by reacting a compound represented by the formula (I′-1-c) with a compound represented by the formula (I′-1-d) in a solvent.

In the formulae, R¹ is as defined above.

Preferred examples of the solvent include methylene chloride, tetrahydrofuran and acetonitrile.

The reaction can be conducted at temperature of preferably −5° C. to 80° C., for 0.5 to 24 hours. A condensation catalyst such as dicyclohexylcarbodiimide may be used for the reaction.

Example of the compound represented by formula (I′-1-c) include a compound represented by formula below.

Monomers (I′) can be produced from a compound corresponding to the compound represented by the formula (I′-1-c) such as compounds having CH2=CH(R′)—CO—O-A¹-Alcin which R¹ and A¹ are as defined above, and A^1c is a hydrogen atom or a monovalent group capable of being modified. The compounds represented by formulae (I′-1-c) and (I′-1-d) are available on the market.

Examples of the monomer (I′) include the monomers represented by formula (I′-1) to formula (I′-12) and these in which a methyl group corresponding to R¹ has been replaced by a hydrogen atom.

The proportion of the structural unit (I) is preferably 1% by mole to 80% by mole, more preferably 2% by mole to 75% by mole, still more preferably 3% by mole to 70% by mole, and further still more preferably 5% by mole to 65% by mole, and in particular preferably 20% by mole to 60% by mole, with respect to the total structural units (100% by mole) constituting the resin (A1).

<Structural Unit (II)>

The structural unit (II) is represented by formula (II).

In the formula, R² represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that may have a halogen atom,

L¹ represents a single bond or *-L²-CO—O-(L³-CO—O)_g— where * represents a binding position to an oxygen atom,

L² and L³ independently represent a C₁ to C₁₂ divalent hydrocarbon group,

“g” represents 0 or 1, and

R³ represents a C₁ to C₁₂ linear or branched alkyl group except for a tertiary alkyl group.

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

Examples of a C₁ to C₆ alkyl group that may have a halogen atom include an unsubstituted alkyl group such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl and n-hexyl groups, and a haloalkyl group such as trifluoromethyl, perfluoroethyl, perfluoropropyl, perfluoro-isopropyl, perfluorobutyl, perfluoro-sec-butyl, perfluoro-tert-butyl, perfluoropentyl, perfluorohexyl, tricloromethyl, tribromomethyl and triiodomethyl groups, preferably an unsaturated C₁ to C₄ alkyl group, and more preferably a methyl group and an ethyl group.

R² is preferably a hydrogen atom or a C₁ to C₄ alkyl group, and more preferably a hydrogen atom, a methyl or an ethyl group, and still more preferably a hydrogen atom or a methyl group.

Examples of the saturated hydrocarbon group for L² and L³ include an alkanediyl group, a divalent alicyclic hydrocarbon group, a divalent aromatic hydrocarbon group and a combination thereof.

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

Examples of the divalent alicyclic hydrocarbon group include the monocyclic group such as cyclobutane-1,3-diyl, cyclopentane-1,3-diyl, cyclohexane-1,4-diyl and cyclooctane-1,5-diyl groups, and the polycyclic group such as norbornane-1,4-diyl, norbornane-2,5-diyl, adamantane-1,5-diyl and adamantane-2,6-diyl groups.

Examples of the divalent aromatic hydrocarbon group include an aryl group such as phenylene, naphthylene, anthrylene, p-methylphenylene, p-tert-butylphenylene, p-adamantanephenylene, tolylene, xylylene, cumenylene, mesitylene, biphenylene, phenanthrene, 2,6-diethylphenylene and 2-methyl-6-ethylphenylene groups.

L¹ is preferably a single bond or a *-L²-CO—O—, more preferably a single bond or *—CH₂—CO—O—, and still more preferably a single bond.

Examples of the C₁ to C₁₂ alkyl group for R³ include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, n-undecyl and n-dodecyl groups.

R³ is preferably a C₁ to C₈ linear alkyl group, more preferably a C₂ to C₈ linear alkyl group, still more preferably a C₃ to C₈ linear alkyl group, in particular preferably a C₄ to C₈ linear alkyl group, further in particular preferably a n-propyl, n-butyl, n-hexyl or n-octyl group, further still in particular preferably n-butyl, n-hexyl or n-octyl group.

Examples of the structural unit (II) include the structural units represented by formulae (II-1) to (II-12) and those in which a methyl group corresponding to R² has been replaced by a hydrogen atom.

Among them, the structural units represented by formulae (II-1) to (II-6) and (II-8) are preferred, and those represented by formulae (II-1), (II-3), (II-6) and (II-8) are more preferred.

The structural unit (II) is derived from a monomer represented by formula (II′), which monomer is sometimes referred to as “monomer (II′)”.

In the formula, L¹, R² and R³ are as defined above.

Examples of the monomer (II′) include the structural units represented by formulae (II′-1) to (II′-12) and those in which the methyl group corresponding to R² has been replaced by a hydrogen atom.

The monomer (II′) is available on the market.

The proportion of the structural unit (II) is preferably 0.5 to 15% by mole, more preferably 1 to 10% by mole, still more preferably 1 to 8% by mole, and further still more preferably 1 to 6% by mole, with respect to the total structural units (100% by mole) of the resin (A1).

<Structural Unit (a1)>

The resin (A1) has the structural unit (a1) in addition to the structural unit (I) and the structural unit (II).

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

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

In the resin (A1), the acid-labile group which the structural unit (a1) has is preferably the following one of formula (1) and formula (2).

In the formula, R^a1 to R^a3 independently represent a C₁ to C₈ alkyl group, a C₃ to C₂₀ alicyclic hydrocarbon group or combination thereof, or R^a1 and R^a2 may be bonded together with a carbon atom bonded thereto to form a C₃ to C₂₀ divalent alicyclic hydrocarbon group,

na represents an integer of 0 or 1, and

* represents a binding position.

In the formula, R^a1′ and R^a2′ independently represent a hydrogen atom or a C₁ to C₁₂ hydrocarbon group, R^a3′ represents a C₁ to C₂₀ hydrocarbon group, or R^a2′ and R^a3′ may be bonded together with a carbon atom and X bonded thereto to form a divalent C₃ to C₂₀ heterocyclic group, and a methylene group contained in the hydrocarbon group or the divalent heterocyclic group may be replaced by an oxygen atom or sulfur atom,

X represents —O— or —S—, and

* represents a binding position.

Examples of the alkyl group for R^a1 to R^a3 include methyl, ethyl, propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl and n-octyl groups.

Examples of the alicyclic hydrocarbon group for R^a1 to R^a3 include monocyclic groups such as a cycloalkyl group, i.e., cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl groups, and polycyclic hydrocarbon groups such as decahydronaphtyl, adamantyl and norbornyl groups as well as groups below. * represents a binding position.

The alicyclic hydrocarbon group of R^a1 to R^a3 preferably has 3 to 16 carbon atoms.

Examples of groups combining the alkyl group and the alicyclic hydrocarbon group include methylcyclohexyl, dimethylcyclohexyl, methylnorbornyl, cyclohexylmethyl, adamantylmethyl and norbornyletyl groups.

na is preferably an integer of 0.

When R^a1 and R^a2 are bonded together to form a divalent alicyclic hydrocarbon group, examples of the group represented by —C(R^a1)(R^a2)(R^a3) include groups below. The divalent alicyclic hydrocarbon group preferably has 3 to 12 carbon atoms. * represent a binding position to —O—.

Specific examples of the group represented by formula (1) include 1,1-dialkylalkoxycarbonyl group (a group represented by formula (1) in which R^a1 to R^a3 are alkyl groups, preferably tert-butoxycarbonyl group),

2-alkyladamantane-2-yloxycarbonyl group (a group represented by formula (1) in which R^a1, R^a2 and a carbon atom form adamantyl group, and R^a3 is alkyl group), and

1-(adamantane-1-yl)-1-alkylalkoxycarbonyl group (a group represented by formula (1) in which R^a1 and R^a2 are alkyl group, and R^a3 is adamantyl group).

The hydrocarbon group for R^a1′ to R^a3 includes an alkyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group and a combination thereof.

Examples of the alkyl group and the alicyclic hydrocarbon group are the same examples as described above.

Examples of the aromatic hydrocarbon group include an aryl group such as phenyl, naphthyl, anthryl, p-methylphenyl, p-tert-butylphenyl, p-adamantylphenyl, tolyl, xylyl, cumenyl, mesityl, biphenyl, phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenyl groups.

Examples of the divalent heterocyclic group formed by binding with R^a2′ and R^a3′ include groups below. * represents a binding position.

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

Specific examples of the group represented by formula (2) include a group below. * represents a binding position.

Among the (meth)acrylic monomer having an acid-labile group, a monomer having a C₅ to C₂₀ alicyclic hydrocarbon group is preferred. When a resin (A1) having a structural unit derived from a monomer (a1) having a bulky structure such as the alicyclic hydrocarbon group is used for a resist composition, the resist composition having excellent resolution tends to be obtained.

Examples of a structural unit derived from the (meth)acrylic monomer having the group represented by formula (1) preferably include structural units represented by formula (a1-0), formula (a1-1) and formula (a1-2) below. These may be used as one kind of the structural unit or as a combination of two or more kinds of the structural units. The structural unit represented by formula (a1-0), the structural unit represented by formula (a1-1) and a structural unit represented by formula (a1-2) are sometimes referred to as “structural unit (a1-0)”, “structural unit (a1-1)” and “structural unit (a1-2)”), respectively, and monomers deriving the structural unit (a1-0), the structural unit (a1-1) and the structural unit (a1-2) are sometimes referred to as “monomer (a1-0)”, “monomer (a1-1)” and “monomer (a1-2)”), respectively.

In the formula, L^a01 represents —O— or *—O—(CH₂)_k01—CO—O—,

k01 represents an integer of 1 to 7,

* represents a binding position to —CO—,

R^a01 represents a hydrogen atom or a methyl group, and

R^a02, R^a03 and R^a04 independently represent a C₁ to C₈ alkyl group, a C₃ to C₁₈ alicyclic hydrocarbon group or combination thereof.

In the formula, L^a1 and L^a2 independently represent —O— or *—O—(CH₂)_k1—CO—O—,

k1 represents an integer of 1 to 7,

* represents a binding position to —CO—,

R^a4 and R^a5 independently represent a hydrogen atom or a methyl group,

R^a6 and R^a7 independently represent a C₁ to C₈ alkyl group, a C₃ to C₁₈ alicyclic hydrocarbon group or a combination thereof,

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.

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

Examples of the alkyl group, an alicyclic hydrocarbon group and combination thereof for R^a02, R^a03 and R^a04 are the same examples as the group described in R^a1 to R^a3 in formula (1).

The alkyl group for R^a02, R^a03 and R^a04 is preferably a C₁ to C₆ alkyl group.

The alicyclic hydrocarbon group for R^a02, R^a03 and R^a04 is preferably a C₃ to C₈ alicyclic hydrocarbon group, more preferably a C₃ to C₆ alicyclic hydrocarbon group.

The group formed by combining the alkyl group and the alicyclic hydrocarbon group has preferably 18 or less of carbon atom. Examples of those groups include methylcyclohexyl, dimethylcyclohexyl, methylnorbornyl, methyladamantyl, cyclohexylmethyl, methyl cyclohexylmethyl, adamantylmethyl and norbornylmethyl groups.

R^a02 and R^a03 is preferably a C₁ to C₆ alkyl group, more preferably a methyl group or an ethyl group.

R^a04 is preferably a C₁ to C₆ alkyl group or a C₅ to C₁₂ alicyclic hydrocarbon group, more preferably a methyl, ethyl, cyclohexyl or adamantyl group.

L^a1 and L^a2 are preferably —O— or *—O—(CH₂)_k1′—CO—O— in which k1′ represents an integer of 1 to 4 and more preferably 1, still more preferably —O—.

R^a4 and R^a5 are preferably a methyl group.

Examples of the alkyl group, an alicyclic hydrocarbon group and a combination thereof for R^a6 and R^a7 are the same examples as the group described in R^a1 to R^a3 in formula (1).

The alkyl group for R^a6 and R^a7 is preferably a C₁ to C₆ alkyl group.

The alicyclic hydrocarbon group for R^a6 and R^a7 is preferably a C₃ to C₈ alicyclic hydrocarbon group, more preferably a C₃ to C₆ alicyclic hydrocarbon 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, and more preferably 1.

Examples of the monomer (a1-0) preferably include monomers represented by formula (a1-0-1) to formula (a1-0-12) and these in which a methyl group corresponding to R^a01 has been replaced by a hydrogen atom, and more preferably monomers represented by formula (a1-0-1) to formula (a1-0-10) below.

Examples of the monomer (a1-1) include monomers described in JP 2010-204646A. Among them, the monomers are preferably monomers represented by formula (a1-1-1) to formula (a1-1-8), and more preferably monomers represented by formula (a1-1-1) to formula (a1-1-4) below.

Examples of the monomer (a1-2) include the monomers represented by formula (a1-2-1) to formula (a1-2-12), and preferably monomers represented by formula (a1-2-3), formula (a1-2-4), formula (a1-2-9) and formula (a1-2-10), and more preferably monomer represented by formula (a1-2-3) and formula (a1-2-9) below.

When the resin (A1) has the structural unit (a1-0), the structural unit (a1-1) and/or the structural unit (a1-2), the total proportion thereof is generally 10 to 95% by mole, preferably 15 to 90% by mole, more preferably 20 to 85% by mole, with respect to the total structural units (100% by mole) of the resin (A1).

Further, examples of the structural unit (a1) having a group represented by formula (1) include a structural unit presented by formula (a1-3). The structural unit represented by formula (a1-3) is sometimes referred to as “structural unit (a1-3)”. The monomer from which the structural unit (a1-3) is derived is sometimes referred to as “monomer (a1-3)”.

In the formula, R^a9 represents a carboxy group, a cyano group, a —COOR^a13, a hydrogen atom or a C₁ to C₃ aliphatic hydrocarbon group that may have a hydroxy group,

R^a13 represents a C₁ to C₈ aliphatic hydrocarbon group, a C₃ to C₂₀ alicyclic hydrocarbon group or a group formed by combining thereof, a hydrogen atom contained in the aliphatic hydrocarbon group and the alicyclic hydrocarbon group may be replaced by a hydroxy group, a methylene group contained in the aliphatic hydrocarbon group and the alicyclic hydrocarbon group may be replaced by an oxygen atom or a carbonyl group, and

R^a10, R^a11 and R^a12 independently represent a C₁ to C₈ alkyl hydrocarbon group, a C₃ to C₂₀ alicyclic hydrocarbon group or a group formed by combining them, or R^a10 and R^a11 may be bonded together with a carbon atom bonded thereto to form a C₁ to C₂₀ divalent alicyclic hydrocarbon group.

Examples of the aliphatic hydrocarbon group that may have a hydroxy group for R^a9 include methyl, ethyl, propyl, hydroxymethyl and 2-hydroxyethyl groups.

Examples of —COOR^a13 group include a group in which a carbonyl group is bonds to the alkoxy group, such as methoxycarbonyl and ethoxycarbonyl groups.

Examples of the C₁ to C₈ aliphatic hydrocarbon group for R^a13 include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, 2-ethylhexyl and n-octyl groups.

Examples of the C₃ to C₂₀ alicyclic hydrocarbon group for R^a13 include cyclopentyl, cyclopropyl, adamantyl, adamantylmetyl, 1-(adamantyl-1-yl)-methylethyl, 2-oxo-oxolane-3-yl, 2-oxo, oxolane-4-yl groups.

Examples of the alkyl group for R^a10 to R^a12 include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, 2-ethylhexyl and n-octyl groups.

Examples of the alicyclic hydrocarbon group for R^a10 and R^a12 include monocyclic hydrocarbon groups such as a cycloalkyl group, i.e., cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, methylcyclohexyl, dimethylcyclohexyl, cycloheptyl, cyclooctyl, cycloheptyl and cyclodecyl groups; and polycyclic hydrocarbon groups such as decahydronaphtyl, adamantyl, 2-alkyl-2-adamantyl, 1-(adamantane-1-yl) alkane-1-yl, norbornyl, methylnorbornyl and isobornyl groups.

When R^a10 and R^a11 is bonded together with a carbon atom bonded thereto to form a divalent alicyclic hydrocarbon group, examples of the group represented by —C(R^a10)(R^a11)(R^a12) include groups below.

Examples of the monomer (a1-3) include tert-butyl 5-norbornene-2-carboxylate, 1-cyclohexyl-1-methylethyl 5-norbornene-2-carboxylate, 1-methylcyclohexyl 5-norbornene-2-carboxylate, 2-methy-2-adamantane-2-yl 5-norbornene-2-carboxylate, 2-ethyl-2-adamantane-2-yl 5-norbornene-2-carboxylate, 1-(4-methycyclohexyl)-1-methylethyl 5-norbornene-2-carboxylate, 1-(4-hydroxycyclohexyl)-1-methylethyl 5-norbornene-2-carboxylate, 1-methyl-(4-oxocyclohexyl)-1-ethyl 5-norbornene-2-carboxylate, and 1-(1-adamantane-1-yl)-1-methylethyl 5-norbornene-2-carboxylate.

The resin (A1) having a structural unit (a1-3) can improve the resolution of the obtained resist composition because it has a bulky structure, and also can improve a dry-etching tolerance of the obtained resist composition because of a rigid norbornene ring having been incorporated into a main chain of the resin (A1).

When the resin (A1) has the structural unit (a1-3), the proportion thereof is generally 10% by mole to 95% by mole, preferably 15% by mole to 90% by mole, and more preferably 20% by mole to 85% by mole, with respect to the total structural units constituting the resin (A1) (100% by mole).

Examples of a structural unit (a1) having a group represented by formula (2) include a structural unit represented by formula (a1-4). The structural unit is sometimes referred to as “structural unit (a1-4)”.

In the formula, R^a32 represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that may have a halogen atom,

R^a33 in each occurrence independently represent a halogen atom, a hydroxy group, a C₁ to C₆ alkyl group, a C₁ to C₆ alkoxy group, a C₂ to C₄ acyl group, a C₂ to C₄ acyloxy group, an acryloyloxy group or methacryloyloxy group,

1a represents an integer 0 to 4,

R^a34 and R^a35 independently represent a hydrogen atom or a C₁ to C₁₂ hydrocarbon group; and

R^a36 represents a C₁ to C₂₀ hydrocarbon group, or R^a35 and R^a36 may be bonded together with a C—O bonded thereto to form a C₃ to C₂₀ divalent heterocyclic group, and a methylene group contained in the hydrocarbon group or the divalent heterocyclic group may be replaced by an oxygen atom or sulfur atom.

Examples of the alkyl group for R^a32 and R^a33 include methyl, ethyl, propyl, isopropyl, butyl, pentyl and hexyl groups. The alkyl group is preferably a C₁ to C₄ alkyl group, and more preferably a methyl group or an ethyl group, and still more preferably a methyl group.

Examples of the halogen atom for R^a32 and R^a33 include fluorine, chlorine, bromine and iodine atoms.

Examples of the alkyl group that may have a halogen atom include trifluoromethyl, difluoromethyl, methyl, perfluoromethyl, 1,1,1-trifluoroethyl, 1,1,2,2-tetrafluoroethyl, ethyl, perfluoropropyl, 1,1,1,2,2-pentafluoropropyl, propyl, perfluorobutyl, 1,1,2,2,3,3,4,4-octafluorobutyl, butyl, perfluoropentyl, 1,1,1,2,2,3,3,4,4-nonafluoropentyl, n-pentyl, n-hexyl and n-perfluorohexyl groups.

Examples of an alkoxy group include methoxy, ethoxy, propoxy, butoxy, pentyloxy, and hexyloxy groups. The alkoxy group is preferably a C₁ to C₄ alkoxy group, more preferably a methoxy group or an ethoxy group, and still more preferably a methoxy group.

Examples of the acyl group include acetyl, propanonyl and butylyl groups.

Examples of the acyloxy group include acetyloxy, propanonyloxy and butylyloxy groups.

Examples of the hydrocarbon group for R^a34 and R^a35 are the same examples as described in R^a1′ to R^a2′ in formula (2).

Examples of hydrocarbon group for R^a36 include a C₁ to C₁₈ alkyl group, a C₃ to C₁₈ alicyclic hydrocarbon group, a C₆ to C₁₈ aromatic hydrocarbon group and a combination thereof.

In formula (a1-4), R^a32 is preferably a hydrogen atom.

R^a33 is preferably a C₁ to C₄ alkoxy group, more preferably a methoxy group or an ethoxy group, and still more preferably a methoxy group.

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

R^a34 is preferably a hydrogen atom.

R^a35 is preferably a C₁ to C₁₂ hydrocarbon group, and more preferably a methyl group or an ethyl group.

The hydrocarbon group for R^a36 is preferably a C₁ to C₁₈ alkyl group, a C₃ to C₁₈ alicyclic hydrocarbon group, a C₆ to C₁₈ aromatic hydrocarbon group and a combination thereof, and more preferably a C₁ to C₁₈ alkyl group, a C₃ to C₁₈ alicyclic hydrocarbon group or a C₇ to C₁₈ aralkyl group. The alkyl group and the alicyclic hydrocarbon group for R^a36 is preferably not substituted. When the aromatic hydrocarbon group of R^a36 has a substituent, the substituent is preferably a C₆ to C₁₀ aryloxy group.

Examples of the monomer from which a structural unit (a1-4) is derived include monomers described in JP 2010-204646A. Among them, the monomers are preferably monomers represented by formula (a1-4-1) to formula (a1-4-7), and more preferably monomers represented by formula (a1-4-1) to formula (a1-4-5) below.

When the resin (A1) has the structural unit (a1-4), the proportion thereof is generally 10% by mole to 95% by mole, preferably 15% by mole to 90% by mole, more preferably 20% by mole to 85% by mole, with respect to the total structural units constituting the resin (A1) (100% by mole).

Examples of a structural unit having an acid-labile group, which is derived from a (meth)acrylic, monomer include a structural unit represented by formula (a1-5). Such structural unit is sometimes referred to as “structural unit (a1-5)”.

In the formula, R^a8 represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that may have a halogen atom,

Z_a1 represents a single bond or *—(CH₂)_h3—CO-L⁵⁴,

h3 represents an integer of 1 to 4,

* represents a binding position to L⁵¹,

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

s1 represents an integer of 1 to 3, and

s1′ represents an integer of 0 to 3.

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

Examples of the alkyl group that may have a halogen atom include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, fluoromethyl and trifluoromethyl groups.

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

L⁵¹ is preferably —O—,

L⁵² and L⁵³ are independently preferably —O— or —S—, and more preferably one is —O— and another is —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— where * represents a binding position to L⁵¹.

Examples of a monomer from which a structural unit (a1-5) is derived include a monomer described in JP 2010-61117A. Among them, the monomers are preferably monomers represented by formula (a1-5-1) to formula (a1-5-4), and more preferably monomers represented by formula (a1-5-1) to formula (a1-5-2) below.

When the resin (A1) has the structural unit (a1-5), the proportion thereof is generally 1% by mole to 50% by mole, preferably 3% by mole to 45% by mole, and more preferably 5% by mole to 40% by mole, with respect to the total structural units (100% by mole) constituting the resin (A1).

Examples of a structural unit (a1) in a resin (A1) is preferably at least one, more preferably two or more of the structural units selected from the structural unit (a1-0), the structural unit (a1-1), the structural unit (a1-2) and the structural unit (a1-5), still more preferably a combination of the structural unit (a1-1) and the structural unit (a1-2), a combination of the structural unit (a1-1) and the structural unit (a1-5), a combination of the structural unit (a1-1) and the structural unit (a1-0), a combination of the structural unit (a1-2) and the structural unit (a1-0), a combination of the structural unit (a1-5) and the structural unit (a1-0), a combination of the structural unit (a1-0), the structural unit (a1-1) and the structural unit (a1-2), a combination of the structural unit (a1-0), the structural unit (a1-1) and the structural unit (a1-5), in particular preferably a combination of the structural unit (a1-1) and the structural unit (a1-2), and a combination of the structural unit (a1-1) and the structural unit (a1-5).

<Structural Unit (s)>

The structural unit (s) is derived from a monomer having no acid-labile group, which monomer is sometimes referred to as “monomer (s)”.

For the monomer (s) from which a structural unit (s) is derived, a known monomer having no acid-labile group can be used.

As the structural unit (s), preferred is a structural unit having a hydroxy group or a lactone ring but having no acid-labile group. When the resist composition contains a resin which has a structural unit (s) having a hydroxy group (such structural unit is sometimes referred to as “structural unit (a2)”) and/or a structural unit (s) having a lactone ring (such structural unit is sometimes referred to as “structural unit (a3)”), the adhesiveness of resist obtained therefrom to a substrate and resolution of resist pattern tend to be improved.

<Structural Unit (a2)>

A hydroxy group which the structural unit (a2) has may be an alcoholic hydroxy group or a phenolic hydroxy group.

When KrF excimer laser lithography (248 nm), or high-energy irradiation such as electron beam or EUV (extreme ultraviolet) is used for the resist composition, the structural unit having a phenolic hydroxy group is preferably used as structural unit (a2).

When ArF excimer laser lithography (193 nm) is used, the structural unit having an alcoholic hydroxy group is preferably used as structural unit (a2), and the structural represented by formula (a2-1) is more preferred.

The structural unit (a2) may be used as one kind of the structural unit or as a combination of two or more kinds of the structural units.

Examples of the structural unit (a2) having a phenolic hydroxy group include the structural unit represented by formula (a2-0) (which structural unit is sometimes referred to as “structural unit (a2-0)”).

In the formula, R^a30 represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that may have a halogen atom,

R^a31 in each occurrence independently represents a halogen atom, a hydroxy group, a C₁ to C₆ alkyl group, a C₁ to C₆ alkoxy group, a C₂ to C₄ acyl group, a C₂ to C₄ acyloxy group, an acryloyl group or methacryloyl group, and ma represents an integer 0 to 4.

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

Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, n-pentyl and n-hexyl groups.

Examples of a C₁ to C₆ alkyl group that may have a halogen atom for R^a35 include trifluoromethyl, difluoromethyl, methyl, perfluoromethyl, 1,1,1-trifluoroethyl, 1,1,2,2-tetrafluoroethyl, ethyl, perfluoropropyl, 1,1,1,2,2-pentafluoropropyl, propyl, perfluorobutyl, 1,1,2,2,3,3,4,4-octafluorobutyl, butyl, perfluoropentyl, 1,1,1,2,2,3,3,4,4-nonafluoropentyl, n-pentyl, n-hexyl and n-perfluorohexyl groups. R^a30 is preferably a hydrogen atom or a C₁ to C₄ alkyl group, and 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 a C₁ to C₆ alkoxy group for R^a31 include methoxy, ethoxy, propoxy, t-butoxy, pentyloxy and hexyloxy groups. R^a31 is preferably a C₁ to C₄ alkoxy group, more preferably a methoxy group and an ethoxy group, and still more preferably a methoxy group.

Examples of the acyl group for R^a31 include acetyl, propanonyl and butylyl groups.

Examples of the acyloxy group for R^a31 include acetyloxy, propanonyloxy and butylyloxy groups.

ma is preferably 0, 1 or 2, more preferably 0 or 1, still more preferably 0.

Examples of a monomer from which the structural unit (a2-0) is derived include monomers described in JP2010-204634A.

The structural unit (a2-0) is preferably a structural unit represented below. Among them, structural units represented by formula (a2-0-1), formula (a2-0-2), formula (a2-0-3) and formula (a2-0-4) are preferred, and structural units represented by formula (a2-0-1) and formula (a2-0-2) are more preferred.

The resin (A1) which has the structural unit (a2-0) can be produced, for example, by polymerizing a monomer where its phenolic hydroxy group has been protected with a suitable protecting group, followed by deprotection. The deprotection is carried in such a manner that an acid-labile group in the structural unit (a1) is significantly impaired. Examples of the protecting group for a phenolic hydroxy group include an acetyl group.

When the resin (A1) has the structural unit (a2-0) having the phenolic hydroxy group, the proportion thereof is generally 5% by mole to 95% by mole, preferably 10% by mole to 80% by mole, more preferably 15% by mole to 80% by mole, with respect to the total structural units (100% by mole) constituting the resin (A1).

Examples of the structural unit (a2) having alcoholic hydroxy group include the structural unit represented by formula (a2-1) (which is sometimes referred to as “structural unit (a2-1)”).

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

k2 represents an integer of 1 to 7,

* represents a binding position 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—, —O—(CH₂)_f1—CO—O—, here 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.

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

Examples of the monomer from which the structural unit (a2-1) is derived include monomers described in JP 2010-204646A. Among them, the monomers are preferably monomers represented by formula (a2-1-1) to formula (a2-1-6), more preferably structural units represented by formula (a2-1-1) to formula (a2-1-4), and still more preferably structural units represented by formula (a2-1-1) and formula (a2-1-3) below.

When the resin (A1) has the structural unit (a2-1), the proportion thereof is generally 1% by mole to 45% by mole, preferably 1% by mole to 40% by mole, more preferably 1% by mole to 35% by mole, and still more preferably 2% by mole to 20% by mole, with respect to the total structural units (100% by mole) constituting the resin (A1).

<Structural Unit (a3)>

The lactone ring included in the structural unit (a3) may be a monocyclic compound such as β-propiolactone, γ-butyrolactone, 6-valerolactone, or a condensed ring of monocyclic lactone ring with another ring. Examples of the lactone ring preferably include γ-butyrolactone or bridged ring with γ-butyrolactone.

Examples of the structural unit (a3) include structural units represented by any of formula (a3-1), formula (a3-2) and formula (a3-3). These structural units may be used as one kind of the structural unit or as a combination of two or more kind of the structural units.

In the formula, La⁴ represents *—O— or *—O—(CH₂)_k3—CO—O—, k3 represents an integer of 1 to 7, * represents a binding position to a carbonyl group,

R^a18 represents a hydrogen atom or a methyl group,

R^a21 in each occurrence represents a C₁ to C₄ aliphatic hydrocarbon group, and

p1 represents an integer of 0 to 5,

L^a5 represents *—O— or *—O—(CH₂)_k3—CO—O—, k3 represents an integer of 1 to 7, * represents a binding position to a carbonyl group,

R^a9 represents a hydrogen atom or a methyl group,

R^a22 in each occurrence represents a carboxy group, a cyano group or a C₁ to C₄ aliphatic hydrocarbon group,

q1 represents an integer of 0 to 3,

L^a6 represents *—O— or *—O—(CH₂)_k3—CO—O—, k3 represents an integer of 1 to 7, * represents a binding position to a carbonyl group,

R^a20 represents a hydrogen atom or a methyl group,

R^a23 in each occurrence represents a carboxy group, a cyano group or a C₁ to C₄ aliphatic hydrocarbon group, and

r1 represents an integer of 0 to 3.

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

In formulae (a3-1) to (a3-3), L^a4 to L⁶ is independently preferably —O—, *—O—(CH₂)_k3′—CO—O—, here k3′ represents an integer of 1 to 4, more preferably —O— or *—O—CH₂—CO—O—, and still more preferably —O—.

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

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

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

Examples of the monomer from which the structural unit (a3) is derived include monomers described in JP 2010-204646A, monomers described in JP2000-122294A and monomers described in JP2012-41274A. The structural units are preferably structural units represented by formula (a3-1-1) to formula (a3-1-4), formula (a3-2-1) to formula (a3-2-4), formula (a3-3-1) to formula (a3-3-4), more preferably structural units represented by formula (a3-1-1) to formula (a3-1-2), formula (a3-2-3), formula (a3-2-4), and still more preferably structural units represented by formula (a3-1-1) or formula (a3-2-3) below.

When the resin (A1) has the structural unit (a3), the total proportion thereof is preferably 5% by mole to 70% by mole, more preferably 10% by mole to 65% by mole, still more preferably 10% by mole to 60% by mole, with respect to the total structural units (100% by mole) constituting the resin (A1).

The proportion of each structural unit represented by formula (a3-1), formula (a3-2) and formula (a3-3) is preferably 5% by mole to 60% by mole, more preferably 5% by mole to 50% by mole, still more preferably 10% by mole to 50% by mole, with respect to the total structural units (100% by mole) constituting the resin (A1).

<Structural Units>

Examples of the structural unit further include a structural unit which may have a fluorine atom (which is sometimes referred to as “structural unit (a4)”), and a structural unit having a non-leaving hydrocarbon group (which is sometimes referred to as “structural unit (a5)”). Hereinafter, the structural units (a4) and (a5) are collectively referred to as “structural unit (t)”.

<Structural Unit (a4)>

Examples of the structural unit (a4) include the structural units represented by formula (a4-0).

In the formula, R⁵ represents a hydrogen atom or a methyl group,

L⁵ represent a single bond or a C₁ to C₄ saturated aliphatic hydrocarbon group,

L³ represents a C₁ to C₈ perfluoroalkanediyl group or a C₃ to C₁₂ perfluorocycloalkanediyl group, and

R⁶ represents a hydrogen atom or a fluorine atom.

Examples of the saturated aliphatic hydrocarbon group for L⁵ include a linear alkanediyl group such as methylene, ethylene, propane-1,3-diyl, butane-1,4-diyl, and a branched alkanediyl group such as ethane-1,1-diyl, propane-1,2-diyl, butane-1,3-diyl, 2-methylpropane-1,3-diyl and 2-methylpropane-1,2-diyl groups.

Examples of the perfluoroalkanediyl group for L³ include difluoromethylene, perfluoroethylene, perfluoroethylmethylene, perfluoropropane-1,3-diyl, perfluoropropane-1,2-diyl, perfluoropropane-2,2-diyl, perfluorobutane-1,4-diyl, perfluorobutane-2,2-diyl, perfluorobutane-1,2-diyl, perfluoropentane-1,5-diyl, perfluoropentane-2,2-diyl, perfluoropentane-3,3-diyl, perfluorohexane-1,6-diyl, perfluorohexane-2,2-diyl, perfluorohexane-3,3-diyl, perfluoroheptane-1,7-diyl, perfluoroheptane-2,2-diyl, perfluoroheptane-3,4-diyl, perfluoroheptane-4,4-diyl, perfluorooctan-1,8-diyl, perfluorooctan-2,2-diyl, perfluorooctan-3,3-diyl and perfluorooctan-4,4-diyl groups.

Examples of the perfluorocycloalkanediyl group for L³ include perfluorocyclohexanediyl, perfluorocyclopentanediyl, perfluorocycloheptanediyl and perfluoroadamantanediyl groups.

L⁵ is preferably a single bond, a methylene or an ethylene group, and more preferably a single bond or a methylene group.

L³ is preferably a C₁ to C₆ perfluoroalkanediyl group, more preferably a C₁ to C₃ perfluoroalkanediyl group.

Examples of the structural unit (a4-0) include structural units represented by formula (a4-0-1) to formula (a4-0-32).

Examples of the structural unit (a4) include the structural units represented by formula (a4-1).

In the formula, R^a41 represents a hydrogen atom or a methyl group,

R^a42 represents an optionally substituted C₁ to C₂₀ hydrocarbon group where a methylene group may be replaced by an oxygen atom or a carbonyl group, and

A^a41 represents an optionally substituted C₁ to C₆ alkanediyl group or a group represented by formula (a-g1):

wherein s represents 0 or 1,

A^a42 and A^a44 independently represent an optionally substituted C₁ to C₅ aliphatic hydrocarbon group,

A^a43 in occurrence represents a single bond or an optionally substituted C₁ to C₅ aliphatic hydrocarbon group, and

X^a41 and X^a42 independently represent —O—, —CO—, —CO—O— or —O—CO—, provided that the total carbon number contained in the group of A^a42, A^a43, A^a44, X^a41 and X^a42 is 7 or less, and

at least one of A^a41 and R^a42 has a halogen atom as a substituent, and

* and ** represent a binding position, and * represents a binding position to —O—CO— R^a42.

The hydrocarbon group for R^a42 includes a chain aliphatic hydrocarbon group, a cyclic aliphatic hydrocarbon group, an aromatic hydrocarbon group and a combination thereof.

The hydrocarbon group may have a carbon-carbon unsaturated bond, is preferably a chain aliphatic hydrocarbon group, a cyclic saturated aliphatic hydrocarbon group and a combination thereof.

The saturated aliphatic hydrocarbon group is preferably a linear or a branched alkyl group, a monocyclic or a polycyclic alicyclic hydrocarbon group, and an aliphatic hydrocarbon group combining an alkyl group with an alicyclic hydrocarbon group.

Examples of the chain aliphatic hydrocarbon group include an alkyl group such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-decyl, n-dodecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl and n-octadecyl groups. Examples of the cyclic aliphatic hydrocarbon group include a monocyclic hydrocarbon group, i.e., cycloalkyl group such as cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl groups; and polycyclic hydrocarbon groups such as decahydronaphtyl, adamantyl and norbornyl groups as well as groups below. * represents a binding position.

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

Examples of the substituent of R^a42 include a halogen atom or a group represented by formula (a-g3).*—x^a47-A^a45  (a-g3)

In the formula, X^a43 represent an oxygen atom, a carbonyl group, a carbonyloxy group or an oxycarbonyl group,

A^a45 represents a C₁ to C₁₇ aliphatic hydrocarbon group that has a halogen atom, and

* represents a binding position.

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

Examples of the aliphatic hydrocarbon group for A^a45 are the same examples as the group of R^a42.

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

When R^a42 is an aliphatic hydrocarbon group having a halogen atom, an aliphatic hydrocarbon group having a fluorine atom is preferred, a perfluoroalkyl group or a perfulorocycloalkyl group are more preferred, a C₁ to C₆ perfluoroalkyl group is still more preferred, a C₁ to C₃ perfluoroalkyl group is particularly preferred.

Examples of the perfluoroalkyl group include perfluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, perfluoropentyl, perfluorohexyl, perfluoroheptyl and perfluorooctyl groups. Examples of the perfluorocycloalkyl group include perfluorocyclohexyl group.

When R^a42 is an aliphatic hydrocarbon group having the group represented by formula (a-g3), the total carbon number contained in the aliphatic hydrocarbon group including the group represented by formula (a-g3) is preferably 15 or less, more preferably 12 or less. The number of the group represented by formula (a-g3) is preferably one when the group represented by formula (a-g3) is the substituent.

The aliphatic hydrocarbon having the group represented by formula (a-g3) is more preferably a group represented by formula (a-g2):*-A^a46-Z^a44-A⁴⁷  (a-g2)

wherein A^a46 represents a C₁ to C₁₇ aliphatic hydrocarbon group that may have a halogen atom,

X^a44 represent a carbonyloxy group or an oxycarbonyl group,

A^a47 represents a C₁ to C₁₇ aliphatic hydrocarbon group that may have a halogen atom,

provided that the total carbon number contained in the group of A^a46, X^a44 and A^a47 is 18 or less,

at least one of A^a46 and A^a47 has a halogen atom, and

* represents a binding position to carbonyl group.

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

The carbon number of the aliphatic hydrocarbon group of A^a47 is preferably 4 to 15, and more preferably 5 to 12, and cyclohexyl and adamantyl groups are still more preferred as the aliphatic hydrocarbon group.

Preferred structure represented by formula (a-g2), *-A^a46-X^a44-A^a47, include the following ones.

Examples of the alkanediyl group for A^a41 include a linear alkanediyl group such as methylene, ethylene, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl and hexane-1,6-diyl groups;

a branched alkanediyl group such as propane-1,2-diyl, butan-1,3-diyl, 2-methylpropane-1,2-diyl, 1-methylpropane-1,4-diyl, 2-methylbutane-1,4-diyl groups.

Examples of the substituent of the alkanediyl group of A^a41 include a hydroxy group and a C₁ to C₆ alkoxy group.

Examples of the substituent of the alkanediyl of A⁴¹ include a hydroxy group and a C₁ to C₆ alkoxy group.

A^a41 is preferably a C₁ to C₄ alkanediyl group, more preferably a C₂ to C₄ alkanediyl group, and still more preferably an ethylene group.

In the group represented by formula (a-g1) (which is sometimes referred to as “group (a-g1)”), the aliphatic hydrocarbon group for A^a42, A^a43 and A^a44 may have a carbon-carbon unsaturated bond, is preferably a saturated aliphatic hydrocarbon group.

The saturated aliphatic hydrocarbon group is preferably a linear or a branched alkyl group, a monocyclic or a polycyclic alicyclic hydrocarbon group, and an aliphatic hydrocarbon group combining an alkyl group with an alicyclic hydrocarbon group.

Examples of the aliphatic hydrocarbon group for A^a42, A^a43 and A^a44 include methylene, ethylene, propane-1,3-diyl, propane-1,2-diyl, butane-1,4-diyl, 1-methylpropane-1,3-diyl, 2-methylpropane-1,3-diyl and 2-methylpropane-1,2-diyl groups.

Examples of the substituent of the aliphatic hydrocarbon group of A^a42, A^a43 and A^a44 include a hydroxy group and a C₁ to C₆ alkoxy group.

s is preferably 0.

Examples of the group (a-g1) in which X^a42 represents an oxygen atom, a carbonyl group, a carbonyloxy group or an oxycarbonyl group include the following ones. In the formula, * and ** each represent a binding position, and ** represents a binding position to —O—CO—R^a42.

The structural unit represented by formula (a4-1) is preferably structural units represented by formula (a4-2) and formula (a4-3).

In formula (a4-2), R^f1 represents a hydrogen atom or a methyl group,

A^f1 represent a C₁ to C₆ alkanediyl group, and

R^f represents a C₁ to C₁₀ hydrocarbon group that has a fluorine atom.

Examples of the alkanediyl group for A^f1 include a chain alkanediyl group such as methylene, ethylene, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl and hexane-1,6-diyl groups; and

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

The hydrocarbon group for R^f2 includes an aliphatic hydrocarbon group and an aromatic hydrocarbon group. The aliphatic hydrocarbon group includes chain aliphatic hydrocarbon groups and cyclic aliphatic hydrocarbon groups, and a combination thereof. The aliphatic hydrocarbon group is preferably an alkyl group and an alicyclic hydrocarbon group.

Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl and 2-ethylhexyl groups.

Examples of the alicyclic hydrocarbon group include any of a monocyclic group and a polycyclic group. Examples of the monocyclic alicyclic hydrocarbon group include a cycloalkyl group such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and cyclodecyl groups. Examples of the polycyclic hydrocarbon groups include decahydronaphthyl, adamantyl, 2-alkyladamantane-2-yl, 1-(adamantane-1-yl) alkane-1-yl, norbornyl, methylnorbornyl and isobornyl groups.

Examples of the hydrocarbon group having a fluorine atom for R^f2 include an alkyl group having a fluorine atom and an alicyclic hydrocarbon group having a fluorine atom.

Specific examples of an alkyl group having a fluorine atom include a fluorinated alkyl group such as difluoromethyl, trifluoromethyl, 1,1-difluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, perfluoroethyl, 1,1,2,2-tetrafluoropropyl, 1,1,2,2,3,3-hexafluoropropyl, perfluoroethylmethyl, 1-(trifluoromethyl)-1,2,2,2-tetrafluoroethyl, 1-(trifluoromethyl)-2,2,2-trifluoroethyl, perfluoropropyl, 1,1,2,2-tetrafluorobutyl, 1,1,2,2,3,3-hexafluorobutyl, 1,1,2,2,3,3,4,4-octafluorobutyl, perfluorobutyl, 1,1-bis(trifluoromethyl)methyl-2,2,2-trifluoroethyl, 2-(perfluoropropyl)ethyl, 1,1,2,2,3,3,4,4-octafluoropentyl, perfluoropentyl, 1,1,2,2,3,3,4,4,5,5-decafluoropentyl, 1,1-bis(trifluoromethyl)2,2,3,3,3-pentafluoropropyl, 2-(perfluorobutyl)ethyl, 1,1,2,2,3,3,4,4,5,5-decafluorohexyl, 1,1,2,2,3,3,4,4,5,5,6,6-dodeca fluorohexyl, perfluoropentylmethyl and perfluorohexyl groups.

Examples of the alicyclic hydrocarbon group having a fluorine atom include a fluorinated cycloalkyl group such as perfluorocyclohexyl and perfluoroadamantyl groups.

In formula (a4-2), A^f1 is preferably a C₂ to C₄ alkanediyl group, and more preferably ethylene group.

R^f2 is preferably a C₁ to C₆ fluorinated alkyl group.

In formula, R^f11 represents a hydrogen atom or a methyl group,

A^f11 represent a C₁ to C₆ alkanediyl group,

A^f13 represents a C₁ to C₁₈ aliphatic hydrocarbon group that may has a fluorine atom,

X^f12 represents an oxycarbonyl group or a carbonyloxy group, and

A^f14 represents a C₁ to C₁₇ aliphatic hydrocarbon group that may has a fluorine atom,

provided that at least one of A^f13 and A^f14 represents an aliphatic hydrocarbon group having a fluorine atom.

Examples of the alkanediyl group for A^f11 are the same examples as the alkanediyl group of A^f1.

Examples of the aliphatic hydrocarbon group for A^f13 include a divalent chain or cyclic aliphatic hydrocarbon group, and a combination thereof. The aliphatic hydrocarbon group may have a carbon-carbon unsaturated bond, and is preferably a saturated aliphatic hydrocarbon group.

The aliphatic hydrocarbon group that may has a fluorine atom for A^f13 preferably include the saturated aliphatic hydrocarbon group that may has a fluorine atom, and more preferably a perfuloroalkandiyl group.

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

The divalent cyclic aliphatic hydrocarbon group that may have a fluorine atom may be a group having a monocyclic or polycyclic group.

Examples of the monocyclic aliphatic hydrocarbon group include cyclohexanediyl and perfluorocyclohexanediyl groups.

Examples of the polycyclic aliphatic hydrocarbon group include adamantanediyl, norbornanediyl, and perfluoroadamantanediyl groups.

Examples of the aliphatic hydrocarbon group for A^f14 include a chain or cyclic hydrocarbon group, and a combination thereof. The aliphatic hydrocarbon group may have a carbon-carbon unsaturated bond, and is preferably a saturated aliphatic hydrocarbon group.

The aliphatic hydrocarbon group that may have a fluorine atom for A^f14 is preferably the saturated aliphatic hydrocarbon group that may have a fluorine atom.

Examples of the chain aliphatic hydrocarbon group that may have a fluorine atom include trifluoromethyl, difluoromethyl, methyl, perfluoromethyl, 1,1,1-trifluoroethyl, 1,1,2,2-tetrafluoroethyl, ethyl, perfluoropropyl, 1,1,1,2,2-pentafluoropropyl, propyl, perfluorobutyl, 1,1,2,2,3,3,4,4-octafluorobutyl, butyl, perfluoropentyl, 1,1,1,2,2,3,3,4,4-nonafluoropentyl, pentyl, hexyl, perfluorohexyl, hepthyl, perfluoroheptyl, octyl and perfluorooctyl groups.

The cyclic aliphatic hydrocarbon group that may have a halogen atom may be a monocyclic or polycyclic group. Examples of the group containing the monocyclic aliphatic hydrocarbon group include cyclopropylmethyl, cyclopropyl, cyclobutylmethyl, cyclopentyl, cyclohexyl and perfluorocyclohexyl groups. Examples of the group containing the polycyclic aliphatic hydrocarbon group include adamantyl, adamantylmethyl, norbornyl, norbornylmethyl, perfluoroadamantyl and perfluoroadamantylmethyl groups

In the formula (a4-3), A^f11 is preferably an ethylene group.

The aliphatic hydrocarbon group for A^f13 is preferably a C₁ to C₆ aliphatic hydrocarbon group, more preferably a C₂ to C₃ aliphatic hydrocarbon group.

The aliphatic hydrocarbon group of A^f14 is preferably a C₃ to C₁₂ aliphatic hydrocarbon group, more preferably a C₃ to C₁₀ aliphatic hydrocarbon group. Among them, A^f14 is preferably a group containing a C₃ to C₁₂ alicyclic hydrocarbon group, more preferably cyclopropylmethyl, cyclopentyl, cyclohexyl, norbornyl and adamantyl groups.

Examples of the structural unit represented by formula (a4-2) include structural units represented by formula (a4-1-1) to formula (a4-1-22).

Examples of the structural unit represented by formula (a4-3) include structural units presented by formula (a4-1′-1) to formula (A4-1′-22).

Examples of the structural unit (a4) further include a structural unit presented by formula (a4-4):

wherein 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 independently represents an integer of 1 to 6, and

R^f22 represents a C₁ to C₁₀ hydrocarbon group having a fluorine atom.

Examples of the hydrocarbon group having a fluorine atom for R^z2 are the same examples as the hydrocarbon group described in R^f2 in formula (a4-2). R^f22 is preferably a C₁ to C₁₀ alkyl group having a fluorine atom or a C₃ to C₁₀ alicyclic hydrocarbon group having a fluorine atom, more preferably a C₁ to C₁₀ alkyl group having a fluorine atom, and still more preferably a C₁ to C₆ alkyl group having a fluorine atom.

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

Examples of the structural unit represented by formula (a4-4) include the following ones.

When the resin (A1) has the structural unit (a4), the proportion thereof is preferably 1 to 20% by mole, more preferably 2 to 15% by mole, still more preferably 3 to 10% by mole, with respect to the total structural units (100% by mole) of the resin (A1).

<Structural Unit (a5)>

Examples of the non-leaving hydrocarbon group in the structural unit (a5) include a chain, branched or cyclic hydrocarbon group. Among them, the structural unit (a5) is preferably a structural unit containing an alicyclic hydrocarbon group.

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

wherein R^s5 represents a hydrogen atom or a methyl group,

R⁵² represents a C₃ to C₁₈ alicyclic hydrocarbon group where a hydrogen atom may be replaced by a C₁ to C₈ aliphatic hydrocarbon group or a hydroxy group, provided that a hydrogen atom contained in the carbon atom bonded to L⁵⁵ is not replaced by the C₁ to C₈ aliphatic hydrocarbon group, and

L⁵⁵ represents a single bond or a C₁ to C₁₈ divalent saturated hydrocarbon group where a methylene group may be replaced by an oxygen atom or a carbonyl group.

Examples of the alicyclic hydrocarbon group of R^s2 include a monocyclic group or polycyclic group. Examples of the monocyclic alicyclic hydrocarbon group include cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl groups. Examples of the polycyclic hydrocarbon group include adamantyl and norbornyl groups.

Examples of the C₁ to C₈ aliphatic hydrocarbon group include an alkyl group such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, 2-ethylhexyl and n-octyl groups.

Examples of the alicyclic hydrocarbon group having a substituent include 3-hydroxyadamantyl and 3-methyladamantyl.

R⁵² is preferably an unsubstituted C₃ to C₁₈ alicyclic hydrocarbon group, and more preferably adamantyl, norbornyl and cyclohexyl groups.

Examples of the divalent saturated hydrocarbon group of L⁵⁵ include a divalent aliphatic saturated hydrocarbon group and a divalent alicyclic saturated hydrocarbon group, and a divalent aliphatic saturated hydrocarbon group is preferred.

Examples of the divalent aliphatic saturated hydrocarbon group include an alkanediyl group such as methylene, ethylene, propanediyl, butanediyl and pentanediyl groups.

Examples of the divalent alicyclic saturated hydrocarbon group include a monocyclic group and a polycyclic group. Examples of the monocyclic alicyclic saturated hydrocarbon groups include cycloalkanediyl such as cyclopentanediyl and cyclohexanediyl groups. Examples of the polycyclic saturated hydrocarbon groups include adamantanediyl and norbornanediyl groups.

Examples of the saturated hydrocarbon group in which a methylene group has been replaced by an oxygen atom or a carbonyl group include groups represented by formula (L1-1) to formula (L1-4). In the formula (L1-1) to formula (L1-4), * represents a binding position to an oxygen atom.

In the formula, X^X1 represents an oxycarbonyl group or a carbonyloxy group,

L^X1 represents a C₁ to C₁₆ divalent saturated aliphatic hydrocarbon group,

L^X2 represents a single bond or a C₁ to C₁₈ divalent saturated hydrocarbon group,

provided that the total carbon number contained in the group of L^X1 and L^X2 is 16 or less;

L^X3 represents a single bond or a C₁ to C₁₇ divalent saturated aliphatic hydrocarbon group,

L^X4 represents a single bond or a C₁ to C₁₆ divalent saturated hydrocarbon group,

provided that the total carbon number contained in the group of L^X3 and L^X4 is 17 or less;

L^X5 represents a C₁ to C₁₅ divalent saturated aliphatic hydrocarbon group,

L^X6 and L^X7 independently represent a single bond or a C₁ to C₁₄ divalent saturated hydrocarbon group,

provided that the total carbon number contained in the group of L^X5, L^X6 and L^X7 is 15 or less,

L^X8 and L^X9 independently represent a single bond or a C₁ to C₁₂ divalent saturated hydrocarbon group,

W^X1 represents a C₃ to C₁₅ divalent saturated alicyclic hydrocarbon group,

provided that the total carbon number contained in the group of L^X8, L^X9 and W^X1 is 15 or less.

L^X1 is preferably a C₁ to C⁸ divalent saturated aliphatic hydrocarbon group, and more preferably a methylene group or an ethylene group.

L^X2 is preferably a single bond or a C₁ to C₈ divalent saturated aliphatic hydrocarbon group, and more preferably a single bond.

L^X3 is preferably a C₁ to C₈ divalent saturated aliphatic hydrocarbon group.

L^X4 is preferably a single bond or a C₁ to C₈ divalent saturated aliphatic hydrocarbon group.

L^X5 is preferably a C₁ to C₈ divalent saturated aliphatic hydrocarbon group, and more preferably a methylene group or an ethylene group.

L^X6 is preferably a single bond or a C₁ to C₈ divalent saturated aliphatic hydrocarbon group, and more preferably a methylene group or an ethylene group.

L^X7 is preferably a single bond or a C₁ to C₈ divalent saturated aliphatic hydrocarbon group.

L^X8 is preferably a single bond or a C₁ to C₈ divalent saturated aliphatic hydrocarbon group, and more preferably a single bond or a methylene group.

L^X9 is preferably a single bond or a C₁ to C₈ divalent saturated aliphatic hydrocarbon group, and more preferably a single bond or a methylene group.

W^X1 is preferably a C₃ to C₁₀ divalent saturated alicyclic hydrocarbon group, and more preferably a cyclohexanediyl group or an adamantanediyl group.

Examples of the group represented by formula (L1-1) include the following ones.

Examples of the group represented by formula (L1-2) include the following ones.

Examples of the group represented by formula (L1-3) include the following ones.

Examples of the group represented by formula (L1-4) include the following ones.

L⁵⁵ is preferably a single bond, methylene group, ethylene group or the groups represented by formula (L1-1), and more preferably a single bond or the groups represented by formula (L1-1).

Examples of the structural unit (a5-1) include the following ones.

Examples of the structural unit (a5) include the structural units of the formulae (a5-1-1) to (a5-1-18) in which a methyl group corresponding to R⁵¹ has been replaced by a hydrogen atom.

When the resin (A1) has the structural unit (a5), the proportion thereof is preferably 1 to 30% by mole, more preferably 2 to 20% by mole, and still more preferably 3 to 15% by mole, with respect to the total structural units (100% by mole) of the resin (A1).

In the resin (A1), the mole ratio of the structural unit (I): the structural unit (II): the structural unit (a1) may be (10 to 65): (0.5 to 15): (20 to 89.5), preferably (20 to 60): (1 to 12): (28 to 79), and more preferably (30 to 60): (2 to 12):28 to 68). In this case that the resin (A1) consists of the structural unit (I), the structural unit (II), and the structural unit (a1), the total mole of the structural unit (I), the structural unit (II) and the structural unit (a1) is 100.

The resin (A1) preferably has a resin having the structural unit (I), the structural unit (II), the structural unit (a1) and the structural unit (s), more preferably has the structural unit (I), the structural unit (II), the structural unit (a1), the structural unit (a2) and the structural unit (a3).

In the resin (A1), the structural unit (a1) is preferably at least one of the structural unit (a1-1) and the structural unit (a1-2) (preferably the structural unit having a cyclohexyl group or a cyclopentyl group), and more preferably is the structural unit (a1-1). The resin (A1) preferably has both the structural unit (a1-1) and the structural unit (a1-2).

The resin (A1) has preferably at least one of the structural unit (a2) and the structural unit (a3). The structural unit (a2) is preferably the structural unit represented by formula (a2-1). The structural unit (a3) is preferably at least one of the structural units (a3-1) and (a3-2).

The proportion of the structural unit derived from the monomer having an adamantyl group (in particular, the structural unit (a1-1)) in the resin (A1) is preferably 15% by mole or more with respect to the structural units (a1). As the mole ratio of the structural unit derived from the monomer having an adamantyl group increases within this range, the dry etching resistance of the resulting resist improves.

The resin (A1) can be produced by a known polymerization method, for example, radical polymerization method, using one or more kinds of monomers as described above. The proportions of the structural units in the resin (A1) can be adjusted by changing the amount of a monomer used in polymerization.

The weight average molecular weight of the resin (A1) 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).

The weight average molecular weight is a value determined by gel permeation chromatography using polystyrene as the standard product. The detailed condition of this analysis is described in Examples.

<Resin (A2)>

The resin (A2), which has a structural unit having a fluorine atom and no structural unit having an acid-labile group, is generally a resin having the structural unit (a4) and no structural unit (a1), and preferably a resin having the structural unit (a4-0).

When the resin (A2) has the structural unit (a4), the proportion thereof is preferably 40% by mole or more, more preferably 45% by mole or more, and still more preferably 50% by mole or, with respect to the total structural units (100% by mole) of the resin (A2).

The resin (A2) may further have the structural unit (a2), the structural unit (a3), the structural unit (a5) and/or the well-known structural unit in the art, which resin preferably further has the structural unit (a5).

The resin (A2) can be produced by a known polymerization method, for example, radical polymerization method, using one or more kind(s) of monomers as described above. The proportions of the structural units in the resin (A2) can be adjusted by changing the amount of a monomer used in polymerization.

The weight average molecular weight of the resin (A2) is preferably 5,000 or more (more preferably 6,000 or more), and 80,000 or less (more preferably 60,000 or less).

When the resist composition includes the resin (A2), the proportion thereof is preferably 1 to 60 parts by mass, more preferably 1 to 50 parts by mass, and still more preferably 1 to 40 parts by mass, in particular preferably 2 to 30 parts by mass, with respect to 100 parts by mass of the resin (A1).

The total proportion of the resin (A1) and the resin (A2) is preferably 80% by mass to 99% by mass, more preferably 90% by mass to 99% by mass, with respect to the total amount of solid components of the resist composition.

The proportion of the solid components in the resist composition and that of the resins in the solid components can be measured with a known analytical method such as liquid chromatography and gas chromatography.

<Acid Generator (B)>

The acid generator is a compound which can be decomposed by light to generate an acid. The acid acts catalytically to the resin (A1), resulting in removing a leaving group from the resin.

The acid generator (B) may be an ionic acid generator or a non-ionic acid generator. The acid generator (B) may be used any an ionic acid generator and a non-ionic acid generator. Examples of the nonionic compounds for the acid generator include organic halogenated compounds; sulfonate esters, e.g. 2-nitrobenzylester, aromatic sulfonates, oximesulfonate, N-sulfonyloxyimide, sulfonyloxyketone, and diazonaphtoquione 4-sulfonate; sulfones, e.g., disulfone, ketosulfone, and sulfonium diazomethane. The ionic compounds for the acid generator include onium salts having an onium cation, e.g., diazonium salts, phosphonium salts, sulfonium salts and iodonium salts. Examples of the anions of onium salt include a sulfonic acid anion, a sulfonylimide anion, sulfonylmethide anion.

As the acid generator, the compounds giving an acid by radiation can be used, which are mentioned in JP63-26653A1, JP55-164824A1, JP62-69263A1, JP63-146038A1, JP63-163452A1, JP62-153853A1, JP63-146029A1, U.S. Pat. No. 3,779,778B1, U.S. Pat. No. 3,849,137B1, DE3914407 and EP126,712A1. The acid generator for the resist composition can be produced by the method described in the above-mentioned documents.

The acid generator is preferably a fluorine-containing compound, more preferably a salt represented by formula (B1) (which is sometimes referred to as “acid generator (B1)”):

wherein Q¹ and Q² each respectively represent a fluorine atom or a C₁ to C₆ perfluoroalkyl group,

L^b1 represents a C₁ to C₂₄ divalent saturated hydrocarbon group where a methylene group may be replaced by an oxygen atom or a carbonyl group and a hydrogen atom may be replaced by a hydroxyl group or fluorine atom, and

Y represents an optionally substituted methyl group or an optionally substituted C₃ to C₁₈ alicyclic hydrocarbon group where a methylene group may be replaced by an oxygen atom, a carbonyl group or a sulfonyl group, and

Z⁺ represents an organic cation.

Examples of the perfluoroalkyl group of Q¹ and Q² include trifluoromethyl, perfluoroethyl, perfluoropropyl, perfluoro-isopropyl, perfluorobutyl, perfluoro-sec-butyl, perfluoro-tert-butyl, perfluoropentyl and perfluorohexyl groups.

Q¹ and Q² independently are preferably trifluoromethyl or fluorine atom, and both of Q¹ and Q² are more preferably a fluorine atom.

Examples of the divalent saturated hydrocarbon group of L^b1 include any of a chain or a branched alkanediyl group, a divalent mono- or a poly-alicyclic saturated hydrocarbon group, and a combination thereof.

Specific examples of the chain alkanediyl group include methylene, ethylene, propane-1,3-diyl, propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl, undecane-1,11-diyl, dodecane-1,12-diyl, tridecane-1,13-diyl, tetradecane-1,14-diyl, pentadecane-1,15-diyl, hexadecane-1,16-diyl, heptadecane-1,17-diyl groups.

Specific examples of the branched chain alkanediyl group include ethane-1,1-diyl, propane-1,1-diyl, propane-1,2-diyl, propane-2,2-diyl, pentane-1,4-diyl, pentane-2,4-diyl, 2-methylpropane-1,3-diyl, 2-methylpropane-1,2-diyl and 2-methylbutane-1,4-diyl groups.

Specific examples of the mono-alicyclic saturated hydrocarbon group include a cycloalkanediyl group such as cyclobutan-1,3-diyl, cyclopentan-1,3-diyl, cyclohexane-1,4-diyl and cyclooctan-1,5-diyl groups.

Specific examples of the poly-alicyclic saturated hydrocarbon group include norbornane-1,4-diyl, norbornane-2,5-diyl, adamantane-1,5-diyl and adamantane-2,6-diyl groups.

Examples of the saturated hydrocarbon group of L^b1 in which a methylene group has been replaced by oxygen atom or a carbonyl group include the following groups represented by formula (b1-1) to formula (b1-3):

wherein L^b2 represents a single bond or a C to C₂₂ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom;

L^b3 represents a single bond or a C₁ to C₂₂ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom or a hydroxy group, and a methylene group may be replaced by an oxygen atom or a carbonyl group;

provided that the total carbon number contained in the group of L^b2 and L^b3 is 22 or less;

L^b4 represents a single bond or a C₁ to C₂₂ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom;

L^b5 represents a single bond or a C₁ to C₂₂ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom or a hydroxy group, and a methylene group may be replaced by an oxygen atom or a carbonyl group;

provided that the total carbon number contained in the group of L^b4 and L^b5 is 22 or less;

L^b6 represents a single bond or a C₁ to C₂₃ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom or a hydroxy group;

L^b7 represents a single bond or a C₁ to C₂₃ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom or a hydroxy group, and a methylene group may be replaced by an oxygen atom or a carbonyl group;

provided that the total carbon number contained in the group of L^b6 and L^b7 is 23 or less, and

* represents a binding position to —Y.

In formula (b1-1) to formula (b1-3), when a methylene group has been replaced by an oxygen atom or a carbonyl group, the carbon number of the saturated hydrocarbon group corresponds to the number of the carbon atom before replacement.

Examples of the divalent saturated hydrocarbon group are the same examples as the divalent saturated hydrocarbon group of L^b.

L^b2 is preferably a single bond.

L^b3 is preferably a C₁ to C₄ divalent saturated hydrocarbon group.

L^b4 is preferably a C₁ to C₈ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom.

L^b5 is preferably a single bond or a C₁ to C₈ divalent saturated hydrocarbon group.

L^b6 is preferably a single bond or a C₁ to C₄ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom.

L^b7 is preferably a single bond or a C₁ to C₁₈ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom or a hydroxy group, and where a methylene group may be replaced by an oxygen atom or a carbonyl group.

Among these, the group represented by the formula (b1-1) or the formula (b1-3) is preferred.

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

wherein L^b represents a single bond or a C₁ to C₂₂ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom or a hydroxy group;

L^b9 represents a C₁ to C₂₀ divalent saturated hydrocarbon group;

L^b10 represents a single bond or a C₁ to C₁₉ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom or a hydroxy group;

provided that the total carbon number contained in the group of L^b9 and L^b10 is 20 or less;

L^b11 represents a C₁ to C₂₁ divalent saturated hydrocarbon group;

L^b12 represents a single bond or a C₁ to C₂₀ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom or a hydroxy group;

provided that the total carbon number contained in the group of L^b11 and L^b12 is 21 or less;

L^b13 represents a C₁ to C₁₉ divalent saturated hydrocarbon group;

L^b14 represents a single bond or a C₁ to C₁₈ divalent saturated hydrocarbon group;

L^b15 represents a single bond or a C₁ to C₁₈ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom or a hydroxy group;

provided that the total carbon number contained in the group of L^b13, L^b14 and L^b15 is 19 or less;

L^b16 represents a C₁ to C₁₈ divalent saturated hydrocarbon group;

L^b17 represents a C₁ to C₁₈ divalent saturated hydrocarbon group;

L^b18 represents a single bond or a C₁ to C₁₇ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom or a hydroxy group;

provided that the total carbon number contained in the group of L^b16, L^b17 and L^b18 is 19 or less.

L^b8 is preferably a C₁ to C₄ divalent saturated hydrocarbon group.

L^b9 is preferably a C₁ to C₈ divalent saturated hydrocarbon group.

L^b10 is preferably a single bond or a C₁ to C₁₉ divalent saturated hydrocarbon group, and more preferably a single bond or a C₁ to C₈ divalent saturated hydrocarbon group.

L^b11 is preferably a C₁ to C₈ divalent saturated hydrocarbon group.

L^b12 is preferably a single bond or a C₁ to C₈ divalent saturated hydrocarbon group.

L^b13 is preferably a C₁ to C₁₂ divalent saturated hydrocarbon group.

L^b14 is preferably a single bond or a C₁ to C₆ divalent saturated hydrocarbon group.

L^b15 is preferably a single bond or a C₁ to C₁₈ divalent saturated hydrocarbon group, and more preferably a single bond or a C₁ to C₈ divalent saturated hydrocarbon group.

L^b16 is preferably a C₁ to C₁₂ divalent saturated hydrocarbon group.

L^b17 is preferably a C₁ to C₆ divalent saturated hydrocarbon group.

L^b18 is preferably a single bond or a C₁ to C₁₇ divalent saturated hydrocarbon group, and more preferably a single bond or a C₁ to C₄ divalent saturated hydrocarbon group.

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

wherein L^b19 represents a single bond or a C₁ to C₂₃ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom;

L^b20 represent a single bond or a C₁ to C₂₃ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom, a hydroxy group or an acyloxy group, and a methylene group contained in an acyloxy group may be replaced by an oxygen atom or a carbonyl group, and a hydrogen atom contained in an acyloxy group may be replaced by a hydroxy group,

provided that the total carbon number contained in the group of L^b19 and L^b20 is 23 or less;

L^b21 represents a single bond or a C₁ to C₂₁ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom;

L^b22 represents a single bond or a C₁ to C₂₁ divalent saturated hydrocarbon group;

L^b23 represents a single bond or a C₁ to C₂₁ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom, a hydroxy group or an acyloxy group, and a methylene group contained in an acyloxy group may be replaced by an oxygen atom or a carbonyl group, and a hydrogen atom contained in an acyloxy group may be replaced by a hydroxy group,

provided that the total carbon number contained in the group of L^b21, L^b22 and L^b23 is 21 or less;

L^b24 represents a single bond or a C₁ to C₂₀ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom;

L^b25 represents a single bond or a C₁ to C₂₁ divalent saturated hydrocarbon group;

L^b26 represents a single bond or a C₁ to C₂₀ divalent saturated hydrocarbon group where a hydrogen atom may be replaced by a fluorine atom, a hydroxy group or an acyloxy group, and a methylene group contained in an acyloxy group may be replaced by an oxygen atom or a carbonyl group, and a hydrogen atom contained in an acyloxy group may be replaced by a hydroxy group,

provided that the total carbon number contained in the group of L^b24, L^b25 and L^b26 is 21 or less.

In formula (b1-9) to formula (b1-11), when a hydrogen atom has been replaced by an acyloxy group, the carbon number of the saturated hydrocarbon group corresponds to the number of the carbon atom, CO and O in addition to the carbon number of the saturated hydrocarbon group.

For formula (b1-9) to formula (b1-11), examples of the divalent saturated hydrocarbon group include an alkanediyl and a monocyclic or polycyclic divalent saturated hydrocarbon group, and a combination of two or more such groups.

Examples of the acyloxy group include acetyloxy, propionyloxy, butyryloxy, cyclohexylcarbonyloxy and adamantylcarbonyloxy groups.

Examples of the acyloxy group having a substituent include oxoadamantylcarbonyloxy, hydroxyadamantylcarbonyloxy, oxocyclohexylcarbonyloxy and hydroxycyclohexylcarbonyloxy groups.

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

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

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

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

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

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

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

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

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

Examples of the monovalent alicyclic hydrocarbon group of Y include groups represented by formula (Y1) to formula (Y11).

Examples of the monovalent alicyclic hydrocarbon group of Y in which a methylene group has been replaced by an oxygen atom, a carbonyl group or a sulfonyl group include groups represented by formula (Y12) to formula (Y38).

Y may have a ketal ring formed by bonding a C₁ to C₈ alkanediyl group together with two oxygen atoms which have been replaced from two hydrogen atom contained in the alicyclic hydrocarbon group. The ketal ring may be formed from two oxygen atoms each bonded to a carbon atom different to one another. When Y is a spiro ring represented by any of formula (Y28) to (Y33), the alkanediyl group between two oxygen atoms preferably has a fluorine atom. In the ketal ring, a methylene group bonded to the oxygen atom preferably has no fluorine atom.

Among these, the alicyclic hydrocarbon group is preferably any one of groups represented by the formula (Y1) to the formula (Y20), the formula (Y30), and the formula (Y31), more preferably any one of groups represented by the formula (Y11), (Y15), (Y16), (Y20), (Y30) or (Y31), and still more preferably group represented by the formula (Y11), (Y15) or (Y30).

Examples of the substituent for the alicyclic group of Y include a halogen atom, a hydroxyl group, a C₁ to C₁₂ alkyl group, a hydroxy group-containing C₁ to C₁₂ alkyl group, a C₃ to C₁₆ monovalent alicyclic hydrocarbon group, a C₁ to C₁₂ alkoxy group, a C₆ to C₁₈ monovalent aromatic hydrocarbon group, a C₇ to C₂₁ aralkyl group, a C₂ to C₄ acyl group, a glycidyloxy group and —(CH₂)_j2—O—CO—R^b1— in which R^b1 represents an C₁ to C₁₆ alkyl group, a C₃ to C₁₆ monovalent alicyclic hydrocarbon group, or a C₆ to C₁₈ monovalent aromatic hydrocarbon group, and j2 represents an integer of 0 to 4.

Examples of the hydroxy group-containing alkyl group include hydroxymethyl and hydroxyethyl groups

Examples of the alkoxyl group include methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, decyloxy and dodecyloxy groups.

Examples of the monovalent aromatic hydrocarbon group include an aryl group such as phenyl, naphthyl, anthryl, p-methylphenyl, p-tert-butylphenyl, p-adamantylphenyl, tolyl, xylyl, cumenyl, mesityl, biphenyl, phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenyl groups.

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

Examples of the acyl group include acetyl, propionyl and butyryl groups.

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

Examples of Y include the groups below. * represents a binding position to L^b1.

When Y is a methyl group and L^b1 is a C₁ to C₁₇ divalent chain or branched saturated hydrocarbon group, a —CH₂— which is bonded to Y and is in the divalent chain or branched saturated hydrocarbon group is preferably replaced by an oxygen atom or a carbonyl group.

Y is preferably a C₃ to C₁₈ monovalent alicyclic hydrocarbon group that may have a substituent, more preferably an adamantyl group which may have a substituent and in which methylene group may be replaced by an oxygen atom, a carbonyl group or a sufonyl group, and still more preferably an adamantyl group, a hydroxyadamantyl group, an oxoadamantyl group or a group below.

The sulfonic acid anion in the salt represented by formula (B1) is preferably an anions represented by formula (B1-A-1) to formula (B1-A-46), and more preferably an anions represented by formula (B1-A-1) to formula (B1-A-4), formula (B1-A-9), formula (B1-A-10), formulae (B1-A-24) to (B1-A-33) and formulae (B1-A-36) to (B1-A-46), below.

In formula (B1-A-1) to formula (B1-A-46), Rⁱ² to Rⁱ⁷ independently represent a C₁ to C₄ alkyl group, and preferably a methyl group or an ethyl group. Rⁱ⁸ represent a C₁ to C₁₂ aliphatic hydrocarbon group, preferably a C₁ to C₄ alkyl group, a C₅ to C₁₂ monovalent alicyclic hydrocarbon group or a group formed by a combination thereof, more preferably a methyl group, an ethyl group, a cyclohexyl group or an adamantyl group. L⁴ represents a single bond or a C₁ to C₄ alkanediyl group. Q¹ and Q² represent the same meaning as defined above.

Specific examples of the sulfonic acid anion in the salt represented by formula (B1) include anions mentioned in JP2010-204646A1.

Among them, preferred examples of the sulfonic acid anion for the salt represented by formula (B1) include anions represented by formulae (B1a-1) to (B1a-22).

In formula (B1-A-1) to formula (B1-A-46), Rⁱ² to Rⁱ⁷ independently represent a C₁ to C₄ alkyl group, and preferably a methyl group or an ethyl group. Rⁱ⁸ represent a C₁ to C₁₂ aliphatic hydrocarbon group, preferably a C₁ to C₄ alkyl group, a C₅ to C₁₂ monovalent alicyclic hydrocarbon group or a group formed by a combination thereof, more preferably a methyl group, an ethyl group, a cyclohexyl group or an adamantyl group. L⁴ represents a single bond or a C₁ to C₄ alkanediyl group. Q¹ and Q² represent the same meaning as defined above.

Specific examples of the sulfonic acid anion in the salt represented by formula (B1) include anions mentioned in JP2010-204646A1.

Among them, preferred examples of the sulfonic acid anion for the salt represented by formula (B1) include anions represented by formulae (B1a-1) to (B1a-22).

Among them, preferred examples of the sulfonic acid anion include anions represented by formulae (B1a-1) to (B1a-3), (B1a-7) to (B1a-16), (B1a-18), (B1a-19) and (B1a-22).

Examples of the organic cation represented by Z⁺ include an organic onium cation such as an organic sulfonium cation, an organic iodonium cation, an organic ammonium cation, a benzothiazolium cation and an organic phosphonium cation, and an organic sulfonium cation and an organic iodonium cation are preferred, and an arylsulfonium cation is more preferred.

Z⁺ of the formula (B1) is preferably represented by any of the formula (b2-1) to the formula (b2-4):

wherein R^b4, R^b5 and R^b6 independently represent a C₁ to C₃₀ aliphatic hydrocarbon group, a C₃ to C₃₆ alicyclic hydrocarbon group or a C₆ to C₃₆ aromatic hydrocarbon group, a hydrogen atom contained in an aliphatic hydrocarbon group may be replaced by a hydroxy group, a C₁ to C₁₂ alkoxy group, a C₃ to C₁₂ alicyclic hydrocarbon group or a C₆ to C₁₈ aromatic hydrocarbon group, a hydrogen atom contained in an alicyclic hydrocarbon group may be replaced by a halogen atom, a C₁ to C₁₈ aliphatic hydrocarbon group, a C₂ to C₄ acyl group or a glycidyloxy group, a hydrogen atom contained in an aromatic hydrocarbon group may be replaced by a halogen atom, a hydroxy group or a C₁ to C₁₂ alkoxy group, or R^b4 and R^b5 may be bonded together with a sulfur atom bonded thereto to form a sulfur-containing ring, a methylene group contained in the ring may be replaced by an oxygen atom, a —SO— or a carbonyl group;

R^b7 and R^b8 in each occurrence independently represent a hydroxy group, a C₁ to C₁₂ aliphatic hydrocarbon group or a C₁ to C₁₂ alkoxy group,

m2 and n2 independently represent an integer of 0 to 5;

R^b9 and R^b10 each independently represent a C₁ to C₃₆ aliphatic hydrocarbon group or a C₃ to C₃₆ alicyclic hydrocarbon group, or R^b9 and R^b10 may be bonded together with a sulfur atom bonded thereto to form a sulfur-containing ring, and a methylene group contained in the ring may be replaced by an oxygen atom, a —SO— or a carbonyl group;

R^b11 represents a hydrogen atom, a C₁ to C₃₆ aliphatic hydrocarbon group, a C₃ to C₃₆ alicyclic hydrocarbon group or a C₆ to C₁₈ aromatic hydrocarbon group;

R^b12 represents a C₁ to C₁₂ aliphatic hydrocarbon group, a C₃ to C₁₈ alicyclic hydrocarbon group and a C₆ to C₁₈ aromatic hydrocarbon group, a hydrogen atom contained in an aliphatic hydrocarbon group may be replaced by a C₆ to C₁₈ aromatic hydrocarbon group, and a hydrogen atom contained in an aromatic hydrocarbon group may be replaced by a C₁ to C₁₂ alkoxy group or a C₁ to C₁₂ alkyl carbonyloxy group;

R^b11 and R^b12 may be bonded together with —CH—CO— bonded thereto to form a ring, and a methylene group contained in the ring may be replaced by an oxygen atom, a —SO— or a carbonyl group;

R^b13, R^b14, R^b15, R^b16, R^b17 and R^b18 in each occurrence independently represent a hydroxy group, a C₁ to C₁₂ aliphatic hydrocarbon group or a C₁ to C₁₂ alkoxy group;

L^b11 represents —S— or —O—;

o2, p2, s2 and t2 independently represent an integer of 0 to 5;

q2 or r2 independently represent an integer of 0 to 4; and

u2 represents an integer of 0 or 1.

Examples of the aliphatic group preferably include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-octyl and 2-ethylhexyl groups. Among these, the aliphatic hydrocarbon group of R^b9 to R^b12 is preferably a C₁ to C₁₂ aliphatic hydrocarbon group.

Examples of the alicyclic hydrocarbon group preferably include monocyclic groups such as a cycloalkyl group, i.e., cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl groups; and polycyclic groups such as decahydronaphtyl, adamantyl and norbornyl groups as well as the following groups. * represents a binding position.

Among these, the alicyclic hydrocarbon group of R^b9 to R^b12 is preferably a C₃ to C₁₈ alicyclic hydrocarbon group, and more preferably a C₄ to C₁₂ alicyclic hydrocarbon group.

Examples of the alicyclic hydrocarbon group where a hydrogen atom may be replaced by an aliphatic hydrocarbon group include methylcyclohexyl, dimethylcyclohexyl, 2-alkyladamantane-2-yl, methylnorbornyl and isobornyl groups. In the alicyclic hydrocarbon group where a hydrogen atom may be replaced by an aliphatic hydrocarbon group, the total carbon number of the alicyclic hydrocarbon group and the aliphatic hydrocarbon group is preferably 20 or less.

Examples of the aromatic hydrocarbon group preferably include an aryl group such as phenyl, tolyl, xylyl, cumenyl, mesityl, p-ethylphenyl, p-tert-butylphenyl, p-cyclohexylphenyl, p-adamantylphenyl, biphenyl, naphthyl, phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenyl groups.

When the aromatic hydrocarbon includes an aliphatic hydrocarbon group or an alicyclic hydrocarbon group, a C₁ to C₁₈ aliphatic hydrocarbon group or a C₃ to C₁₈ alicyclic hydrocarbon group is preferred.

Examples of the aromatic hydrocarbon group where a hydrogen atom may be replaced by an alkoxy group include a p-methoxyphenyl group.

Examples of the aliphatic hydrocarbon group where a hydrogen atom may be replaced by an aromatic hydrocarbon group include an aralkyl group such as benzyl, phenethyl phenylpropyl, trityl, naphthylmethyl and naphthylethyl groups.

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

Examples of the acyl group include acetyl, propionyl and butyryl groups.

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

Examples of the alkylcarbonyloxy group include methylcarbonyloxy, ethylcarbonyloxy, n-propylcarbonyloxy, isopropylcarbonyloxy, n-butylcarbonyloxy, sec-butylcarbonyloxy, tert-butyl carbonyloxy, pentylcarbonyloxy, hexylcarbonyloxy, octylcarbonyloxy and 2-ethylhexylcarobonyloxy groups.

The sulfur atom-containing ring which is formed by R^b4 and R^b5 may be a monocyclic or polycyclic group, which may be an aromatic or non-aromatic group, and which may be a saturated or unsaturated group. The ring is preferably a ring having 3 to 18 carbon atoms, and more preferably a ring having 4 to 13 carbon atoms. Examples of the sulfur atom-containing ring include a 3- to 12-membered ring, preferably a 3- to 7-membered ring, examples thereof include the following rings.

Examples of the ring formed by R^b9 and R^b10 may be any of monocyclic, polycyclic, aromatic, non-aromatic, saturated and unsaturated rings. The ring may be a 3- to 12-membered ring, preferably a 3- to 7-membered ring. Examples of the ring include thiolane-1-ium ring (tetrahydrothiophenium ring), thian-1-ium ring and 1,4-oxathian-4-ium ring.

Examples of the ring formed by R^b11 and R^b12 may be any of monocyclic, polycyclic, aromatic, non-aromatic, saturated and unsaturated rings. The ring may be a 3- to 12-membered ring, preferably a 3- to 7-membered ring. Examples of the ring include oxocycloheptane ring, oxocyclohexane ring, oxonorbornane ring and oxoadamantane ring.

Among the cations represented by formula (b2-1) to formula (b2-4), the cation represented by formula (b2-1) is preferred.

Examples of the cation represented by formula (b2-1) include the following ones.

Examples of the cation represented by formula (b2-2) include the following ones.

Examples of the cation represented by formula (b2-3) include the following ones.

Examples of the cation represented by formula (b2-4) include the following ones.

The acid generator (B1) is generally a compound which consists of the above sulfonate anion with an organic cation. The above sulfonic acid anion and the organic cation may optionally be combined. Preferred combination is a combination of any of the anion represented by the formula (B1a-1) to the formula (B1a-3), the formula (B1a-7) to the formula (B1a-19) and the formula (B1a-22) and the cation represented by the formula (b2-1) or the formula (b2-3).

Preferred acid generators (B1) are represented by formulae (B1-1) to (B1-40). Among them, the acid generator (B1) represented by formulae (B1-1), (B1-2), (B1-3), (B1-5), (B1-6), (B1-7), (B1-11), (B1-12), (B1-13), (B1-14), (B1-17), (B1-20), (B1-21), (B1-23), (B1-24), (B1-25), (B1-26), (B1-29), (B1-31), (B1-32), (B1-33), (B1-34), (B1-35), (B1-36), (B1-37), (B1-38), (B1-39) and (B1-40) which contain arylsulfonium cation are preferred.

The proportion of the acid generator (B1) is preferably 30% by mass or more, and 100% by mass or less, more preferably 50% by mass or more, and 100% by mass or less, and still more preferably substantially 100% by weight, with respect to 100% by mass of total acid generator (B).

In the resist composition of the disclosure, the proportion of the acid generator (B) is preferably 1 parts by mass or more and more preferably 3 parts by mass or more, and preferably 30 parts by mass or less and more preferably 25 parts by mass or less with respect to 100 parts by mass of the resin (A1).

In the resist composition of the disclosure, the acid generator (B) can be used as one kind of the salt or as two or more kinds of them.

<Solvent (E)>

The proportion of a solvent (E) is 90% by mass or more, preferably 92% by mass or more, and more preferably 94% by mass or more, and also preferably 99% by mass or less and more preferably 99.9% by mass or less of the total amount of the resist composition. The proportion of the solvent (E) can be measured with a known analytical method such as, for example, liquid chromatography and gas chromatography.

Examples of the solvent (E) include glycol ether esters such as ethylcellosolve acetate, methylcellosolve acetate and propyleneglycolmonomethylether acetate; glycol ethers such as propyleneglycolmonomethylether; 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. These solvents may be used as a single solvent or as a mixture of two or more solvents.

<Quencher>

The resist composition of the present disclosure may contain a quencher such as a basic nitrogen-containing organic compound and a salt which generates an acid lower in acidity than an acid generated from the acid generators and which is sometimes referred to as “weak acid salt”.

The proportion of the quencher is preferably 0.01% by mass to 5% by mass with respect to the total amount of solid components of the resist composition.

Examples of the basic nitrogen-containing organic compound include an amine and ammonium salts. The amine may be an aliphatic amine or an aromatic amine. The aliphatic amine includes any of a primary amine, secondary amine and tertiary amine.

Specific examples of the amine include 1-naphtylamine, 2-naphtylamine, 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, ethylene diamine, tetramethylene diamine, hexamethylene diamine, 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 and bipyridine. Among them, diisopropylaniline is preferred, particularly 2,6-diisopropylaniline is more preferred.

Specific examples of the ammonium salt include tetramethylammonium hydroxide, tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide, tetrahexylammonium hydroxide, tetraoctylammonium hydroxide, phenyltrimethyl ammonium hydroxide, 3-(trifluoromethyl)phenyltrimethylammonium hydroxide, tetra-n-butyl ammonium salicylate and choline.

The “acidity” for the weak acid salt can be represented by acid dissociation constant, pKa, of an acid generated from a weak acid salt. Examples of the weak acid salt include a salt generating an acid of pKa represents generally more than −3, preferably −1 to 7, and more preferably 0 to 5.

Specific examples of the weak acid salt include the following salts, the weak acid inner salt of formula (D), and salts as disclosed in JP2012-229206A1, JP2012-6908A1, JP2012-72109A1, JP2011-39502A1 and JP2011-191745A1, preferably the salt of formula (D).

wherein R^D1 and R^D2 in each occurrence independently represent a C₁ to C₁₂ hydrocarbon group, a C₁ to C₆ alkoxy group, a C₂ to C₇ acyl group, a C₂ to C₇ acyloxy group, a C₂ to C₇ alkoxycarbonyl group, a nitro group or a halogen atom, and

m′ and n′ independently represent an integer of 0 to 4.

The hydrocarbon group for R^D1 and R^D2 includes any of an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group and a combination thereof.

Examples of the aliphatic hydrocarbon group include an alkyl group such as methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, pentyl, hexyl and nonyl groups.

The alicyclic hydrocarbon group is any one of monocyclic or polycyclic hydrocarbon group, and saturated or unsaturated hydrocarbon group. Examples thereof include a cycloalkyl group such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclononyl and cyclododecyl groups; adamantyl and norbornyl groups. The alicyclic hydrocarbon group is preferably saturated hydrocarbon group.

Examples of the aromatic hydrocarbon group include an aryl group such as phenyl, 1-naphthyl, 2-naphthyl, 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 4-ethylphenyl, 4-propylphenyl, 4-isopropylphenyl, 4-butylphenyl, 4-tert-butylphenyl, 4-hexylphenyl, 4-cyclohexylphenyl, anthryl, p-adamantylphenyl, tolyl, xylyl, cumenyl, mesityl, biphenyl, phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenyl groups.

Examples of the combination thereof include an alkyl-cycloalkyl, a cycloalkyl-alkyl, aralkyl (e.g., phenylmethyl, 1-phenylethyl, 2-phenylethyl, 1-phenyl-1-propyl, 1-phenyl-2-propyl, 2-phenyl-2-propyl, 3-phenyl-1-propyl, 4-phenyl-1-butyl, 5-phenyl-1-pentyl and 6-phenyl-1-hexyl groups) groups.

Examples of the alkoxy group include methoxy and ethoxy groups.

Examples of the acyl group include acetyl, propanonyl, benzoyl and cyclohexanecarbonyl groups.

Examples of the acyloxy group include a group in which oxy group (—O—) bonds to an acyl group.

Examples of the alkoxycarbonyl group include a group in which the carbonyl group (—CO—) bonds to the alkoxy group.

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

In the formula (D), R^D1 and R^D2 in each occurrence independently preferably represent a C₁ to C₈ alkyl group, a C₃ to C₁₀ cycloalkyl group, a C₁ to C₆ alkoxy group, a C₂ to C₄ acyl group, a C₂ to C₄ acyloxy group, a C₂ to C₄ alkoxycarbonyl group, a nitro group or a halogen atom.

m′ and n′ independently preferably represent an integer of 0 to 3, more preferably an integer of 0 to 2, and more preferably 0.

Specific examples of the weak acid inner salt include the following ones.

The weak acid inner salt of formula (D) can be produced by a method described in “Tetrahedron Vol. 45, No. 19, p 6281-6296”. Also, commercially available compounds can be used as the compound (D).

In the resist composition of the present disclosure, the proportion of the salt which generates an acid weaker in acidity than an acid generated from the acid generator, for example, the weak acid inner salt (D) is preferably 0.01% by mass to 5% by mass, more preferably 0.01% by mass to 4% by mass, and still more preferably 0.01% by mass to 3% by mass with respect to total amount of solid components of the resist composition.

<Other Ingredient>

The resist composition can also include other ingredient (which is sometimes referred to as “other ingredient (F)”). The other ingredient (F) includes various additives such as sensitizers, dissolution inhibitors, surfactants, stabilizers, and dyes, as needed.

<Preparing the Resist Composition>

The present resist composition can be prepared by mixing the resin (A1) and acid generator (B) as well as the resin (A2), the quencher such as the weak acid inner salt (D), the solvent (E) and the other ingredient (F), as needed. There is no particular limitation on the order of mixing. The mixing may be performed in an arbitrary order. The temperature of mixing may be adjusted to an appropriate temperature within the range of 10 to 40° C., depending on the kinds of the resin and solubility in the solvent (E) of the resin. The time of mixing may be adjusted to an appropriate time within the range of 0.5 to 24 hours, depending on the mixing temperature. There is no particular limitation to the tool for mixing. An agitation mixing may be adopted.

After mixing the above ingredients, the present resist compositions can be prepared by filtering the mixture through a filter having about 0.003 to 0.2 μm of its pore diameter.

<Method for Producing Resist Pattern>

The method for producing a resist pattern of the present disclosure includes the steps of:

(1) applying the resist composition of the present disclosure onto a substrate;

(2) drying the applied composition to form a composition layer;

(3) exposing the composition layer;

(4) heating the exposed composition layer, and

(5) developing the heated composition layer.

Applying the resist composition onto the substrate can generally be carried out through the use of a resist application device, such as a spin coater known in the field of semiconductor microfabrication technique. Examples of the substrate include inorganic substrates such as silicon wafer. The substrate may be washed, and an organic antireflection film may be formed on the substrate by use of a commercially available antireflection composition, before the application of the resist composition.

The solvent evaporates from the resist composition to form a composition layer. Drying the composition on a substrate, for example, can be carried out using a heating device such as a hotplate (so-called “prebake”), a decompression device, or a combination thereof. The temperature is preferably within the range of 50 to 200° C. The time for heating is preferably 10 to 180 seconds. The pressure is preferably within the range of 1 to 1.0×10⁵ Pa.

The composition layer thus obtained is generally exposed using an exposure apparatus or a liquid immersion exposure apparatus. The exposure is generally carried out using with various types of exposure light source, such as irradiation with ultraviolet lasers, i.e., KrF excimer laser (wavelength: 248 nm), ArF excimer laser (wavelength: 193 nm), F₂ excimer laser (wavelength: 157 nm), irradiation with harmonic laser light of far-ultraviolet or vacuum ultra violet wavelength-converted laser light from a solid-state laser source (YAG or semiconductor laser or the like), or irradiation with electron beam or EUV or the like. The composition layer is preferably exposed using a liquid immersion exposure apparatus with ArF excimer laser. In the specification, such exposure to radiation is sometimes referred to be collectively called as exposure. The exposure is generally carried out through a mask that corresponds to the desired pattern. When electron beam is used as the exposure light source, exposure directly to a composition film can be carried out without using a mask.

After exposure, the composition layer is subjected to a heat treatment (so-called “post-exposure bake”) to promote the deprotection reaction. The heat treatment can be carried out using a heating device such as a hotplate. The heating temperature is generally in the range of 50 to 200° C., preferably in the range of 70 to 150° C.

The developing of the baked composition film is usually carried out with a developer using a development apparatus. Developing can be conducted in the manner of dipping method, paddle method, spray method and dynamic dispensing method. Temperature for developing is generally 5 to 60° C. The time for developing is preferably 5 to 300 seconds.

The resist pattern obtained from the resist composition may be a positive one or a negative one by selecting suitable developer.

The development for obtaining a positive resist pattern is usually carried out with an alkaline developer. The alkaline developer to be used may be any one of various alkaline aqueous solution used in the art. Generally, an aqueous solution of tetramethylammonium hydroxide or (2-hydroxyethyl)trimethylammonium hydroxide (commonly known as “choline”) is often used. The surfactant may be contained in the alkaline developer.

After development, the resist pattern formed is preferably washed with ultrapure water, and the residual water remained on the resist film or on the substrate is preferably removed therefrom.

The development for obtaining a negative resist pattern is usually carried out with a developer containing an organic solvent. The organic solvent to be used may be any one of various organic solvents used in the art, examples of which include ketone solvents such as 2-hexanone, 2-heptanone; glycol ether ester solvents such as propyleneglycolmonomethylether acetate; ester solvents such as the butyl acetate; glycol ether solvents such as the propyleneglycolmonomethylether; amide solvents such as N,N-dimethylacetamide; aromatic hydrocarbon solvents such as anisole.

In the developer containing an organic solvent, the amount of organic solvents is preferably 90% by mass to 100% by mass, more preferably 95% by mass to 100% by mass of the developer. The developer still more preferably consists essentially of organic solvents.

Among them, the developer containing an organic solvent preferably contains butyl acetate and/or 2-heptanone. In the developer containing an organic solvent, the total amount of butyl acetate and 2-heptanone is preferably 50% by mass to 100% by mass of the developer, more preferably 90% by mass to 100% by mass of the developer. The developer still more preferably consists essentially of butyl acetate and/or 2-heptanone.

Developers containing an organic solvent may contain a surfactant. Also, the developer containing an organic solvent may include a little water.

The developing with a developer containing an organic solvent can be finished by replacing the developer by another solvent.

After development, the resist pattern formed is preferably washed with a rinse agent. Such rinse agent is not unlimited provided that it does not detract a resist pattern. Examples of the agent include solvents which contain organic solvents other than the above-mentioned developers, such as alcohol agents or ester agents.

After washing, the residual rinse agent remained on the substrate or photoresist film is preferably removed therefrom.

<Application>

The resist composition of the present disclosure is useful for excimer laser lithography such as with ArF, KrF, electron beam (EB) exposure lithography or extreme-ultraviolet (EUV) exposure lithography, and is more useful for electron beam (EB) exposure lithography, ArF excimer laser exposure lithography and extreme-ultraviolet (EUV) exposure lithography.

The resist composition of the present disclosure can be used in semiconductor microfabrication.

EXAMPLES

All percentages and parts expressing the contents or amounts used in the Examples and Comparative Examples are based on mass, unless otherwise specified.

The weight average molecular weight is a value determined by gel permeation chromatography.

Column: TSK gel Multipore HXL-M×3+guardcolumn (Tosoh Co. Ltd.)

Eluant: tetrahydrofuran

Flow rate: 1.0 mL/min.

Detecting device: RI detector

Column temperature: 40° C.

Injection amount: 100 μL

Standard material for calculating molecular weight: standard polystyrene (Tosoh Co. ltd.)

Structures of compounds were determined by mass spectrometry (Liquid Chromatography: 1100 Type, manufactured by AGILENT TECHNOLOGIES LTD., Mass Spectrometry: LC/MSD Type, manufactured by AGILENT TECHNOLOGIES LTD.). The value of the peak in the mass spectrometry is referred to as “MASS”.

Synthesis Example 1: Synthesis of the Salt Represented by the Formula (B1-21)

The compound represented by the formula (B1-21-b) was produced according to a method recited in JP2008-209917A1.

Into a reactor, 30.00 parts of compound represented by the formula (B1-21-b) and 35.50 parts of salt represented by the formula (B1-21-a), 100 parts of chloroform and 50 parts of ion exchanged water were charged and stirred at 23° C. for about 15 hours. The obtained reaction mixture, which had two layers, was separated into a chloroform layer therefrom. To the chloroform layer, 30 parts of ion exchanged water was added and washed with it. These steps were conducted five times. Then the washed layer was concentrated, and then, 100 parts of tert-butyl methyl ether was added to the obtained residues and the obtained mixture was stirred at 23° C. for about 30 minutes. The resulting mixture was filtrated to provide 48.57 parts of salt represented by the formula (B1-21-c).

Into a reactor, 20.00 parts of salt represented by the formula (B1-21-c), 2.84 parts of compound represented by the formula (B1-21-d) and 250 parts of monochlorobenzene were charged and stirred at 23° C. for 30 minutes. To the resulting mixture, 0.21 parts of copper (II) dibenzoate was added and the obtained mixture was stirred at 100° C. for 1 hour. The reaction mixture was concentrated, and then, 200 parts of chloroform and 50 parts of ion exchanged water were added to the obtained residues and the obtained mixture was stirred at 23° C. for 30 minutes, followed by separating an organic layer to wash with water. 50 parts of ion exchanged water was added to the obtained organic layer, and the obtained mixture was stirred at 23° C. for 30 minutes, followed by separating an organic layer. The washing step with water was conducted five times. The obtained organic layer was concentrated, and then the obtained residues were dissolved in 53.51 parts of acetonitrile. Then the mixture was concentrated, and then 113.05 parts of tert-butyl methyl ether was added thereto and the obtained mixture was stirred, followed by filtrating it to provide 10.47 parts of the salt represented by the formula (B1-21).

MASS (ESI(+)Spectrum): M+237.1

MASS (ESI(−)Spectrum): M−339.1

Synthesis Example 2: Synthesis of the Salt Represented by the Formula (B1-22)

Into a reactor, 11.26 parts of salt represented by the formula (B1-21-a), 10 parts of compound represented by the formula (B1-22-b), 50 parts of chloroform and 25 parts of ion exchanged water were charged and stirred at 23° C. for about 15 hours. The obtained reaction mixture, which had two layers, was separated into a chloroform layer therefrom. To the chloroform layer, 15 parts of ion exchanged water were added and washed with it: These steps were conducted five times. Then the washed layer was concentrated, and then 50 parts of tert-butyl methyl ether was added to the obtained residues, and the obtained mixture was stirred at 23° C. for about 30 minutes. The resulting mixture was filtrated to provide 11.75 parts of the salt represented by the formula (B1-22-c).

Into a reactor, 11.71 parts of a salt represented by the formula (B1-22-c), 1.70 parts of a compound represented by the formula (B1-21-d) and 46.84 parts of monochlorobenzene were charged and stirred at 23° C. for 30 minutes. To the resulting mixture, 0.12 parts of copper (II) dibenzoate was added and the obtained mixture was stirred at 100° C. for 30 minutes. The reaction mixture was concentrated, and then 50 parts of chloroform and 12.50 parts of ion exchanged water were added to the obtained residues, and the obtained mixture was stirred at 23° C. for 30 minutes, followed by separating an organic layer to wash with water. 12.50 parts of ion exchanged water was added to the obtained organic layer and the obtained mixture was stirred at 23° C. for 30 minutes, followed by separating an organic layer to wash with water. The washing step with water was conducted eight times. Then the obtained organic layer was concentrated, and then 50 parts of tert-butyl methyl ether were added thereto and the obtained mixture was stirred, followed by filtrating it to provide 6.84 parts of the salt represented by the formula (B1-22).

MASS (ESI(+)Spectrum): M+237.1

MASS (ESI(−)Spectrum): M−323.0

Synthesis Examples of Resins

The monomers used for Synthesis Examples of the resins are shown below. These monomers are referred to as “monomer (X)” where “(X)” is the symbol of the formula representing the structure of each monomer.

Synthesis Example 3: Synthesis of Resin A1-1

Monomer (a1-1-3), monomer (a1-2-9), monomer (a2-1-1), monomer (I′-2) and monomer (II′-1) were mixed together with the mole ratio of monomer (a1-1-3):monomer (a1-2-9):monomer (a2-1-1):monomer (a3-2-1):monomer (I′-2):monomer (II′-1) is 18.5:18.5:5:55:3, and propyleneglycolmonomethylether acetate was added thereto in the amount equal to 1.5 times by mass of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the solution in the amounts of 1% by mole and 3% by mole respectively with respect to the total amount of monomers, and the resultant mixture was heated at 75° C. for about 5 hours. Then, the obtained reaction mixture was poured into a large amount of a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. The obtained resin was dissolved in propyleneglycolmonomethylether acetate to obtain a solution, and the solution was poured into a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. These operations were conducted twice to provide the resin having a weight average molecular weight of about 8100 in 83% yield. This resin, which had the structural units of the following formulae, was referred to Resin A1-1.

Synthesis Example 4: Synthesis of Resin A1-2

Monomer (a1-1-3), monomer (a1-2-9), monomer (a2-1-1), monomer (I′-2) and monomer (II′-1) were mixed together with the mole ratio of monomer (a1-1-3):monomer (a1-2-9):monomer (a2-1-1):monomer (a3-2-1):monomer (I′-2):monomer (II′-1) is 18.5:18.5:3:54:6, and propyleneglycolmonomethylether acetate was added thereto in the amount equal to 1.5 times by mass of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the solution in the amounts of 1% by mole and 3% by mole respectively with respect to the total amount of monomers, and the resultant mixture was heated at 73° C. for about 5 hours. Then, the obtained reaction mixture was poured into a large amount of a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. The obtained resin was dissolved in propyleneglycolmonomethylether acetate to obtain a solution, and the solution was poured into a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. These operations were conducted twice to provide the resin having a weight average molecular weight of about 7900 in 84% yield. This resin, which had the structural units of the following formulae, was referred to Resin A1-2.

Synthesis Example 5: Synthesis of Resin A1-3

Monomer (a1-1-3), monomer (a1-2-9), monomer (a2-1-1), monomer (I′-2) and monomer (II′-1) were mixed together with the mole ratio of monomer (a1-1-3):monomer (a1-2-9):monomer (a2-1-1):monomer (a3-2-1):monomer (I′-2):monomer (II′-1) is 20:20:3:48:9, and propyleneglycolmonomethylether acetate was added thereto in the amount equal to 1.5 times by mass of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the solution in the amounts of 0.95% by mole and 2.85% by mole respectively with respect to the total amount of monomers, and the resultant mixture was heated f at 73° C. for about 5 hours. Then, the obtained reaction mixture was poured into a large amount of a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. The obtained resin was dissolved in propyleneglycolmonomethylether acetate to obtain a solution, and the solution was poured into a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. These operations were conducted twice to provide the resin having a weight average molecular weight of about 7800 in 80% yield. This resin, which had the structural units of the following formulae, was referred to Resin A1-3.

Synthesis Example 6: Synthesis of Resin A1-4

Monomer (a1-1-3), monomer (a1-2-9), monomer (a3-2-1), monomer (I′-2) and monomer (II′-1) were mixed together with the mole ratio of monomer (a1-1-3):monomer (a1-2-9):monomer (a2-1-1):monomer (a3-2-1):monomer (I′-2):monomer (II′-1) is 18.5:18.5:19:40:3, and propyleneglycolmonomethylether acetate was added thereto in the amount equal to 1.5 times by mass of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the solution in the amounts of 1% by mole and 3% by mole respectively with respect to the total amount of monomers, and the resultant mixture was heated at 73° C. for about 5 hours. Then, the obtained reaction mixture was poured into a large amount of a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. The obtained resin was dissolved in propyleneglycolmonomethylether acetate to obtain a solution, and the solution was poured into a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. These operations were conducted twice to provide the resin having a weight average molecular weight of about 7500 in 78% yield. This resin, which had the structural units of the following formulae, was referred to Resin A1-4.

Synthesis Example 7: Synthesis of Resin A1-5

Monomer (a1-1-1), monomer (I′-2) and monomer (II′-1) were mixed together with the mole ratio of monomer (a1-1-1):monomer (I′-2):monomer (II′-1) is 45:45:10, and propyleneglycolmonomethylether acetate was added thereto in the amount equal to 1.5 times by mass of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the solution in the amounts of 1% by mole and 3% by mole respectively with respect to the total amount of monomers, and the resultant mixture was heated at 73° C. for about 5 hours. Then, the obtained reaction mixture was poured into a large amount of a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. The obtained resin was dissolved in propyleneglycolmonomethylether acetate to obtain a solution, and the solution was poured into a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. These operations were conducted twice to provide the resin having a weight average molecular weight of about 8500 in 76% yield. This resin, which had the structural units of the following formulae, was referred to Resin A1-5

Synthesis Example 8: Synthesis of Resin A1-6

Monomer (a1-1-3), monomer (a1-2-11), monomer (a2-1-1), monomer (I′-2) and monomer (II′-1) were mixed together with the mole ratio of monomer (a1-1-3):monomer (a1-2-11):monomer (a2-1-1):monomer (I′-2):monomer (II′-1) is 18.5:18.5:5:55:3, and propyleneglycolmonomethylether acetate was added thereto in the amount equal to 1.5 times by mass of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the solution in the amounts of 1% by mole and 3% by mole respectively with respect to the total amount of monomers, and the resultant mixture was heated at 75° C. for about 5 hours. Then, the obtained reaction mixture was poured into a large amount of a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. The obtained resin was poured into a mixture of methanol and ion exchanged water and filtrated to provide the resin having a weight average molecular weight of about 8300 in 78% yield. This resin, which had the structural units of the following formulae, was referred to Resin A1-6.

Synthesis Example 9: Synthesis of Resin A1-7

Monomer (a1-1-3), monomer (a1-2-11), monomer (a2-1-1), monomer (I′-2) and monomer (11′-6) were mixed together with the mole ratio of monomer (a1-1-3):monomer (a1-2-11):monomer (a2-1-1):monomer (I′-2):monomer (II′-6) is 18.5:18.5:5:55:3, and propyleneglycolmonomethylether acetate was added thereto in the amount equal to 1.5 times by mass of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the solution in the amounts of 1% by mole and 3% by mole respectively with respect to the total amount of monomers, and the resultant mixture was heated at 75° C. for about 5 hours. Then, the obtained reaction mixture was poured into a large amount of a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. The obtained resin was poured into a mixture of methanol and ion exchanged water and filtrated to provide the resin having a weight average molecular weight of about 8500 in 78% yield. This resin, which had the structural units of the following formulae, was referred to Resin A1-7.

Synthesis Example 10: Synthesis of Resin A1-8

Monomer (a1-1-3), monomer (a1-2-11), monomer (a2-1-1), monomer (I′-2) and monomer (II′-8) were mixed together with the mole ratio of monomer (a1-1-3):monomer (a1-2-11):monomer (a2-1-1):monomer (I′-2):monomer (II′-8) is 18.5:18.5:5:55:3, and propyleneglycolmonomethylether acetate was added thereto in the amount equal to 1.5 times by mass of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the solution in the amounts of 1% by mole and 3% by mole respectively with respect to the total amount of monomers, and the resultant mixture was heated at 75° C. for about 5 hours. Then, the obtained reaction mixture was poured into a large amount of a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. The obtained resin was poured into a mixture of methanol and ion exchanged water and filtrated to provide the resin having a weight average molecular weight of about 8300 in 75% yield. This resin, which had the structural units of the following formulae, was referred to Resin A1-8.

Synthesis Example 11: Synthesis of Resin A1-9

Monomer (a1-1-3), monomer (a1-2-11), monomer (a3-2-1), monomer (I′-2) and monomer (II′-1) were mixed together with the mole ratio of monomer (a1-1-3):monomer (a1-2-11):monomer (a3-2-1):monomer (I′-2):monomer (II′-1) is 18.5:18.5:19:40:3, and propyleneglycolmonomethylether acetate was added thereto in the amount equal to 1.5 times by mass of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the solution in the amounts of 1% by mole and 3% by mole respectively with respect to the total amount of monomers, and the resultant mixture was heated at 75° C. for about 5 hours. Then, the obtained reaction mixture was poured into a large amount of a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. The obtained resin was poured into a mixture of methanol and ion exchanged water and filtrated to provide the resin having a weight average molecular weight of about 7900 in 80% yield. This resin, which had the structural units of the following formulae, was referred to Resin A1-9.

Synthesis Example 12: Synthesis of Resin A1-10

Monomer (a1-1-3), monomer (a1-2-11), monomer (a3-2-1), monomer (I′-2) and monomer (II′-6) were mixed together with the mole ratio of monomer (a1-1-3):monomer (a1-2-11):monomer (a3-2-1):monomer (I′-2):monomer (II′-6) is 18.5:18.5:19:40:3, and propyleneglycolmonomethylether acetate was added thereto in the amount equal to 1.5 times by mass of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the solution in the amounts of 1% by mole and 3% by mole respectively with respect to the total amount of monomers, and the resultant mixture was heated at 75° C. for about 5 hours. Then, the obtained reaction mixture was poured into a large amount of a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. The obtained resin was poured into a mixture of methanol and ion exchanged water and filtrated to provide the resin having a weight average molecular weight of about 8100 in 75% yield. This resin, which had the structural units of the following formulae, was referred to Resin A1-10.

Synthesis Example 13: Synthesis of Resin A1-11

Monomer (a1-1-3), monomer (a1-2-11), monomer (a3-2-1), monomer (I′-2) and monomer (11′-8) were mixed together with the mole ratio of monomer (a1-1-3):monomer (a1-2-11):monomer (a3-2-1):monomer (I′-2):monomer (II′-8) is 18.5:18.5:19:40:3, and propyleneglycolmonomethylether acetate was added thereto in the amount equal to 1.5 times by mass of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the solution in the amounts of 1% by mole and 3% by mole respectively with respect to the total amount of monomers, and the resultant mixture was heated at 75° C. for about 5 hours. Then, the obtained reaction mixture was poured into a large amount of a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. The obtained resin was poured into a mixture of methanol and ion exchanged water and filtrated to provide the resin having a weight average molecular weight of about 8300 in 72% yield. This resin, which had the structural units of the following formulae, was referred to Resin A1-11.

Synthesis Example 14: Synthesis of Resin A2-1

Monomer (a5-1-1) and monomer (a4-0-12)=50:50, and methylisobutylketone was added thereto in the amount equal to 0.6 times by mass of the total amount of monomers to obtain a solution. Azobisisobutyronitrile was added as initiators to the solution in the amounts of 3% by mole respectively with respect to the total amount of monomers, and the resultant mixture was heated at 70° C. for about 5 hours. The obtained reaction mixture was poured into a large amount of a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated to provide the copolymer having a weight average molecular weight of about 15000 in 88% yield. This resin, which had the structural units of the following formulae, was referred to Resin A2-1.

Synthesis Example 15: Synthesis of Resin X1

Monomer (a1-1-1), monomer (a3-1-X) and monomer (II′-1) were mixed together with a mole ratio of monomer (a1-1-1), monomer (a3-1-X) and monomer (II′-1)=45:45:10, and propyleneglycolmonomethylether acetate was added thereto in the amount equal to 1.5 times by mass of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the solution in the amounts of 1% by mole and 3% by mole respectively with respect to the total amount of monomers, and the resultant mixture was heated at 75° C. for about 5 hours. Then, the obtained reaction mixture was poured into a large amount of a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. The obtained resin was dissolved in propyleneglycolmonomethylether acetate to obtain a solution, and the solution was poured into a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. These operations were conducted twice to provide the resin having a weight average molecular weight of about 8400 in 85% yield. This resin, which had the structural units of the following formulae, was referred to Resin X1.

Synthesis Example 16: Synthesis of Resin X2

Monomer (a1-1-1), monomer (a2-1-1), monomer (a3-1-1) and monomer (a5-1-X) were mixed together with a mole ratio of monomer (a1-1-1):monomer (a2-1-1):monomer (a3-1-1):monomer (a5-1-X)=45:15:40:5, and propyleneglycolmonomethylether acetate was added thereto in the amount equal to 1.5 times by mass of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the solution in the amounts of 1% by mole and 3% by mole respectively with respect to the total amount of monomers, and the resultant mixture was heated at 70° C. for about 5 hours. Then, the obtained reaction mixture was poured into a large amount of a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. The obtained resin was dissolved in propyleneglycolmonomethylether acetate to obtain a solution, and the solution was poured into a mixture of methanol and ion exchanged water to precipitate a resin. The obtained resin was filtrated. These operations were conducted twice to provide the resin having a weight average molecular weight of about 9200 in 81% yield. This resin, which had the structural units of the following formulae, was referred to Resin X2.

(Preparing Resist Compositions)

Resist compositions were prepared by mixing and dissolving each of the components shown in Table 1, and then filtrating through a fluororesin filter having 0.2 μm pore diameter.

TABLE 1
		Acid
	Resin	Generator (B)	Compound (D)
Resist Comp.	(parts)	(parts)	(parts)	PB/PEB
Composition 1	A2-1/A1-1 =	B1-21/B1-22 =	D1 = 0.05	90° C./85° C.
	0.3/10	0.9/0.4
Composition 2	A2-1/A1-2 =	B1-21/B1-22 =	D1 = 0.05	90° C./85° C.
	0.3/10	0.9/0.4
Composition 3	A2-1/A1-3 =	B1-21/B1-22 =	D1 = 0.05	90° C./85° C.
	0.3/10	0.9/0.4
Composition 4	A2-1/A1-4 =	B1-21/B1-22 =	D1 = 0.05	90° C./85° C.
	0.3/10	0.9/0.4
Composition 5	A2-1/A1-5 =	B1-21/B1-22 =	D1 = 0.05	100° C./115° C.
	0.3/10	0.9/0.4
Composition 6	A2-1/A1-6 =	B1-21/B1-22 =	D1 = 0.05	90° C./85° C.
	0.3/10	0.9/0.4
Composition 7	A2-1/A1-7 =	B1-21/B1-22 =	D1 = 0.05	90° C./85° C.
	0.3/10	0.9/0.4
Composition 8	A2-1/A1-8 =	B1-21/B1-22 =	D1 = 0.05	90° C./85° C.
	0.3/10	0.9/0.4
Composition 9	A2-1/A1-9 =	B1-21/B1-22 =	D1 = 0.05	90° C./85° C.
	0.3/10	0.9/0.4
Composition 10	A2-1/A1-10 =	B1-21/B1-22 =	D1 = 0.05	90° C./85° C.
	0.3/10	0.9/0.4
Composition 11	A2-1/A1-11 =	B1-21/B1-22 =	D1 = 0.05	90° C./85° C.
	0.3/10	0.9/0.4
Comparative	A2-1/X1 =	B1-21/B1-22 =	D1 = 0.05	100° C./115° C.
Composition 1	0.3/10	0.9/0.4
Comparative	A2-1/X2 =	B1-21/B1-22 =	D1 = 0.05	100° C./115° C.
Composition 2	0.3/10	0.9/0.4

The symbols listed in Table 1 represent the following ones.

<Resin>

Resins: Resins A1-1 to A1-11, A2-1, X1 to X2, each prepared by the method as described above.

<Acid Generator (B)>

B1-21: Salt represented by the formula (B1-21)

B1-22: Salt represented by the formula (B1-22)

<Compound (D)>

D1: Compound as follow, a product of Tokyo Chemical Industry Co., LTD

<Solvent for Resist Compositions>

	Propyleneglycolmonomethyl ether acetate	265	parts
	Propyleneglycolmonomethyl ether	20	parts
	2-Heptanone	20	parts
	γ-butyrolactone	3.5	parts

<Evaluation of Residue>

A composition for an organic antireflective film (“ARC-29”, by Nissan Chemical Co. Ltd.) was applied onto 12-inch silicon wafer and baked for 60 seconds at 205° C. to form a 78 nm thick organic antireflective film.

One of the resist compositions was then applied thereon by spin coating in such a manner that the thickness of the film after drying (pre-baking) became 85 nm.

The obtained wafer was then pre-baked for 60 seconds on a direct hot plate at the temperature given in the “PB” column in Table 1.

On the wafers on which the resist film had thus been formed, the film was then exposed through a mask for forming trench patterns (pitch 120 nm/trench width 40 nm) while changing exposure quantity stepwise, with an ArF excimer laser stepper for liquid-immersion lithography (“XT:1900Gi” by ASML Ltd.: NA=1.35, Dipole 0.900/0.700 Y-pol. lighting). Ultrapure water was used as medium for liquid-immersion.

After the exposure, post-exposure baking was carried out for 60 seconds at the temperature given in the “PEB” column in Table 1.

Then, development was carried out with butyl acetate (a product of Tokyo Chemical Industry Co., LTD) at 23° C. for 20 seconds in the manner of dynamic dispensing method to obtain negative resist patterns.

Effective sensitivity was represented as the exposure quantity at which the resist pattern with 40 nm trench width was obtained.

The trench patterns were obtained by way of the process where the exposure was carried out at the exposure quantity of the effective sensitivity, and then each pattern was observed using a scanning electron microscope. When residues were not observed on the unexposed surface of the substrate, it was evaluated as “o” (good). When residues were observed on the unexposed surface of the substrate, it was evaluated as “X” (bad). Table 2 illustrates the results thereof.

<Evaluation Critical Dimension Uniformity (CDU)>

A composition for an organic antireflective film (“ARC-29”, by Nissan Chemical Co. Ltd.) was applied onto 12-inch silicon wafer and baked for 60 seconds at 205° C. to form a 78 nm thick organic antireflective film.

One of the resist compositions was then applied thereon by spin coating in such a manner that the thickness of the film after drying (pre-baking) became 85 nm.

The obtained wafer was then pre-baked for 60 seconds on a direct hot plate at the temperature given in the “PB” column in Table 1.

On the wafers on which the resist film had thus been formed, the film was then exposed through a mask for forming contact hole patterns (hole pitch 90 nm/hole diameter 55 nm) while changing exposure quantity stepwise, with an ArF excimer laser stepper for liquid-immersion lithography (“XT:1900Gi” by ASML Ltd.: NA=1.35, 3/4 Annular, XY-pol. lighting). Ultrapure water was used as medium for liquid-immersion.

After the exposure, post-exposure baking was carried out for 60 seconds at the temperature given in the “PEB” column in Table 1.

Then, development was carried out with butyl acetate (a product of Tokyo Chemical Industry Co., LTD) at 23° C. for 20 seconds in the manner of dynamic dispensing method to obtain negative resist patterns.

Effective sensitivity was represented as the exposure quantity at which the resist pattern with 50 nm hole diameter was obtained.

The resist patterns were formed by the same method described above using the mask of 55 nm of hole diameter with the effective sensitivity. The hole diameter was measured 24 times per one hole, and an average of those was an average hole diameter. As to the average hole diameter of the patterns formed by using a mask which had 70 nm of hole diameter, the standard deviation was obtained based on the population which was 400 values of the above average hole diameter within the same wafer.

When the standard deviation was less than 1.80 nm, it was evaluated as “o” (good). When the standard deviation was 1.80 nm or more, it was evaluated as “X” (bad).

Table 2 illustrates the results thereof. The parenthetical number means the standard deviation (nm).

TABLE 2
	Resist Composition	Residue	CDU
	Ex. 1	Composition 1	∘	∘(1.61)
	Ex. 2	Composition 2	∘	∘(1.64)
	Ex. 3	Composition 3	∘	∘(1.69)
	Ex. 4	Composition 4	∘	∘(1.61)
	Ex. 5	Composition 5	∘	∘(1.78)
	Ex. 6	Composition 6	∘	∘(1.59)
	Ex. 7	Composition 7	∘	∘(1.60)
	Ex. 8	Composition 8	∘	∘(1.61)
	Ex. 9	Composition 9	∘	∘(1.58)
	Ex. 10	Composition 10	∘	∘(1.57)
	Ex. 11	Composition 11	∘	∘(1.59)
	Comparative	Comparative	x	x(1.93)
	Ex. 1	Composition 1
	Comparative	Comparative	x	x(1.83)
	Ex. 2	Composition 2

The resist composition of the disclosure can provide the resist patterns with excellent CDU and few residues. Therefore, the resist composition can be used for semiconductor microfabrication.

Claims

1. A resist composition comprising a resin (A1) which has a structural unit represented by formula (I), a structural unit represented by formula (II), and a structural unit having an acid-labile group,a resin (A2) which has a structural unit having a fluorine atom and no structural unit having an acid-labile group,an acid generator, anda weak acid inner salt represented by formula (D),wherein the proportion of the resin (A2) is 1 parts by mass to 30 parts by mass with respect to 100 parts by mass of the resin (A1),wherein formula (I) is as follows:

2. The resist composition according to claim 1, wherein L1 is a single bond.

3. A method for producing a resist pattern comprising steps (1) to (4); (1) applying the resist composition according to claim 1 onto a substrate;(2) drying the applied composition to form a composition layer;(3) exposing the composition layer; and(4) developing the exposed composition layer.

4. The resist composition according to claim 1, wherein the total proportion of the resin (A1) and the resin (A2) is 80% by mass to 99% by mass, with respect to the total amount of solid components of the resist composition.

5. The resist composition according to claim 1, wherein the resin (A1) has a structural unit represented by formula (a1-1) and a structural unit represented by formula (a1-2) as the structural unit having an acid-labile group:

6. The resist composition according to claim 1, wherein a mole ratio of the structural unit (II) is 0.5 to 15% by mole with respect to the total structural units of the resin (A1).