Patent Application
20250164878
This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2023-195606 filed in Japan on Nov. 17, 2023, the entire contents of which are hereby incorporated by reference.
This invention relates to a resist composition and a pattern forming process.
To meet the demand for higher integration density and operating speed of LSIs, the effort to reduce the pattern rule is in rapid progress. As the use of 5G high-speed communications and artificial intelligence (AI) is widely spreading, high-performance devices are needed for their processing. As the advanced miniaturization technology, manufacturing of microelectronic devices at the 5-nm node by the lithography using EUV of wavelength 13.5 nm has been implemented in a mass scale. Studies are made on the application of EUV lithography to 3-nm node devices of the next generation and 2-nm node devices of the next-but-one generation. IMEC in Belgium announced its successful development of 2 Å node devices.
As the feature size reduces, image blurs due to acid diffusion become a problem. To insure resolution for fine patterns with a size of 45 nm et seq., not only an improvement in dissolution contrast is important as previously reported, but the control of acid diffusion is also important as reported in Non-Patent Document 1. Since chemically amplified resist compositions are designed such that sensitivity and contrast are enhanced by acid diffusion, an attempt to minimize acid diffusion by reducing the temperature and/or time of post-exposure bake (PEB) fails, resulting in drastic reductions of sensitivity and contrast.
A triangular tradeoff relationship among sensitivity, resolution, and edge roughness (LWR) has been pointed out. Specifically, a resolution improvement requires to suppress acid diffusion whereas a short acid diffusion distance leads to a decline of sensitivity.
The addition of an acid generator capable of generating a bulky acid is an effective means for suppressing acid diffusion. It was then proposed to incorporate repeat units derived from an onium salt having a polymerizable unsaturated bond in a polymer. Since this polymer functions as an acid generator, it is referred to as polymer-bound acid generator. Patent Document 1 discloses a sulfonium or iodonium salt having a polymerizable unsaturated bond, capable of generating a specific sulfonic acid. Patent Document 2 discloses a sulfonium salt having a sulfonic acid directly attached to the backbone.
Resist compositions adapted for the ArF lithography are typically based on (meth)acrylate polymers having acid labile groups. These acid labile groups undergo deprotection reaction when a photoacid generator capable of generating a sulfonic acid which is substituted at α-position with fluorine (referred to as “α-fluorinated sulfonic acid, hereinafter) is used, but not when a photoacid generator capable of generating a sulfonic acid which is not substituted at α-position with fluorine (referred to as “α-non-fluorinated sulfonic acid, hereinafter) or carboxylic acid is used. When a sulfonium or iodonium salt capable of generating α-fluorinated sulfonic acid is mixed with a sulfonium or iodonium salt capable of generating α-non-fluorinated sulfonic acid, the sulfonium or iodonium salt capable of generating α-non-fluorinated sulfonic acid undergoes ion exchange with the α-fluorinated sulfonic acid. Through the ion exchange, the α-fluorinated sulfonic acid once generated upon light exposure is converted back to the sulfonium or iodonium salt. Then the sulfonium or iodonium salt of α-non-fluorinated sulfonic acid or carboxylic acid functions as a quencher. Patent Document 3 discloses a resist composition comprising a sulfonium or iodonium salt capable of generating carboxylic acid as the quencher.
Patent Documents 4 and 5 disclose resist materials comprising a sulfonium salt of a phenol compound having a fluorinated benzene ring as the quencher. After the sulfonium salt of phenol compound is decomposed, a phenol compound is created. Since the phenol compound is little swollen in an alkaline developer, it is effective for preventing pattern collapse caused by swell. However, fluorine is less effective for suppressing acid diffusion, allowing acid diffusion to spread. LWR or critical dimension uniformity (CDU) is then degraded. Further, the sulfonium salt of a fluorinated phenol compound is liable to pyrolysis because the fluorinated phenol compound has a low acidity. A resist material having the sulfonium salt of a fluorinated phenol compound added thereto undesirably undergoes a sensitivity increase during storage.
It is desired to have a quencher capable of reducing the roughness (LWR) of line patterns, improving the critical dimension uniformity (CDU) of hole patterns, and increasing the sensitivity of a resist composition. To this end, image blurs due to acid diffusion must be significantly reduced.
An object of the invention is to provide a resist composition which exhibits a high sensitivity, reduced LWR, and improved CDU independent of whether it is of positive or negative tone, and a pattern forming process using the same.
The inventors have found that a sulfonium salt of an iodized phenol compound is an effective quencher for suppressing acid diffusion. Because of the effect of suppressing acid diffusion, the effect of minimizing swell to prevent pattern collapse, and the effect of improving contrast by strong absorption of iodine, a resist composition using the sulfonium salt as the quencher exhibits reduced LWR, improved CDU, high resolution, and wide process margin. Since the iodized phenol compound has a high acidity, the sulfonium salt thereof is resistant to pyrolysis. A resist composition having the sulfonium salt added thereto has improved storage stability.
In one aspect, the invention provides a resist composition comprising a sulfonium salt of an iodized phenol compound.
In a preferred embodiment, the sulfonium salt has the formula (1).
Herein m is 1, 2, 3, 4 or 5, n is 0, 1, 2, 3 or 4, m+n is from 1 to 5,
Typically, the resist composition further comprises a base polymer.
In a preferred embodiment, the base polymer comprises repeat units of at least one type selected from repeat units having the formula (a1) and repeat units having the formula (a2).
Herein RA is each independently hydrogen or methyl,
Preferably, the resist composition is a chemically amplified positive resist composition.
In another preferred embodiment, the base polymer is free of an acid labile group. The resist composition is typically a chemically amplified negative resist composition.
In a preferred embodiment, the base polymer comprises repeat units of at least one type selected from repeat units having the formula (f1), repeat units having the formula (f2), repeat units having the formula (f3), repeat units having the formula (f4), and repeat units having the formula (f5).
Herein RA is each independently hydrogen or methyl,
The resist composition may further comprise an acid generator capable of generating a strong acid. Preferably, the acid generator generates a sulfonic acid, imide acid or methide acid.
The resist composition may further comprise an organic solvent and/or a surfactant.
In another aspect, the invention provides a pattern forming process comprising the steps of applying the resist composition defined herein onto a substrate to form a resist film thereon, exposing the resist film to high-energy radiation, and developing the exposed resist film in a developer. Most often, the high-energy radiation is KrF excimer laser, ArF excimer laser, EB or EUV of wavelength 3 to 15 nm.
The sulfonium salt of an iodized phenol compound serves as a quencher capable of suppressing acid diffusion. The salt is successful in achieving low acid diffusion performance. A resist composition having reduced LWR or improved CDU can be designed.
As used herein, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. “Optional” or “optionally” means that the subsequently described event or circumstances may or may not occur, and that description includes instances where the event or circumstance occurs and instances where it does not. The notation (Cn-Cm) means a group containing from n to m carbon atoms per group. In chemical formulae, the broken line (---) designates a point of attachment or valence bond. As used herein, the term “fluorinated” refers to a fluorine-substituted or fluorine-containing compound or group and “iodized” refers to a iodine-substituted or iodine-containing compound or group. The terms “group” and “moiety” are interchangeable.
The abbreviations and acronyms have the following meaning.
One embodiment of the invention is a resist composition comprising a sulfonium salt of an iodized phenol compound as a quencher.
The sulfonium salt of an iodized phenol compound preferably has the formula (1).
In formula (1), m is 1, 2, 3, 4 or 5, n is 0, 1, 2, 3 or 4, and m+n is from 1 to 5.
In formula (1), R1 is each independently halogen exclusive of iodine, hydroxy, nitro, cyano, a C1-C20 hydrocarbyl group, C1-C20 hydrocarbyloxy group, C2-C20 hydrocarbylcarbonyloxy group, or C1-C20 hydrocarbylsulfonyloxy group.
The hydrocarbyl group and hydrocarbyl moiety in the hydrocarbyloxy, hydrocarbylcarbonyloxy, and hydrocarbylsulfonyloxy groups, represented by R1, may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as will be exemplified later for the C1-C20 hydrocarbyl groups R2 to R4. The hydrocarbyl, hydrocarbyloxy, hydrocarbylcarbonyloxy, and hydrocarbylsulfonyloxy groups may contain at least one element selected from halogen, oxygen, sulfur and nitrogen. That is, in the hydrocarbyl group, some or all of the hydrogen atoms may be substituted by a moiety containing at least one element selected from halogen, oxygen, sulfur and nitrogen, and some —CH2— may be replaced by a moiety containing at least one element selected from oxygen, sulfur and nitrogen, so that the group may contain hydroxy, fluorine, chlorine, bromine, iodine, cyano, nitro, carbonyl, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (—C(═O)—O—C(═O)—), or haloalkyl moiety.
Examples of the anion in the sulfonium salt having formula (1) are shown below, but not limited thereto.
In formula (1), R2 to R4 are each independently halogen or a C1-C20 hydrocarbyl group which may contain a heteroatom. Suitable halogen atoms include fluorine, chlorine, bromine, and iodine. The C1-C20 hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof include C1-C20 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, heptadecyl, octadecyl, nonadecyl, and icosyl; C3-C20 cyclic saturated hydrocarbyl groups such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; C2-C20 alkenyl groups such as vinyl, propenyl, butenyl, and hexenyl; C2-C20 alkynyl groups such as ethynyl, propynyl, and butynyl; C3-C20 cyclic unsaturated aliphatic hydrocarbyl groups such as cyclohexenyl and norbornenyl; C6-C20 aryl groups such as phenyl, methylphenyl, ethylphenyl, n-propylphenyl, isopropylphenyl, n-butylphenyl, isobutylphenyl, sec-butylphenyl, tert-butylphenyl, naphthyl, methylnaphthyl, ethylnaphthyl, n-propylnaphthyl, isopropylnaphthyl, n-butylnaphthyl, isobutylnaphthyl, sec-butylnaphthyl, and tert-butylnaphthyl; C7-C20 aralkyl groups such as benzyl and phenethyl; and combinations thereof.
In the hydrocarbyl group, some or all of the hydrogen atoms may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, and some constituent —CH2— may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxy, fluorine, chlorine, bromine, iodine, cyano, nitro, mercapto, pentafluorosulfanyl, carbonyl, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (—C(═O)—O—C(═O)—), or haloalkyl moiety.
Also, R2 and R3 may bond together to form a ring with the sulfur atom to which they are attached. Rings of the structure shown below are preferred.
Herein, the broken line denotes a point of attachment to R4.
Examples of the cation in the sulfonium salt having formula (1) are shown below, but not limited thereto.
The sulfonium salt having formula (1) may be synthesized, for example, by ion exchange between a hydrochloride or carbonate salt having a sulfonium cation and an ammonium salt of an iodized phenol compound.
In the resist composition, the sulfonium salt having formula (1) is preferably used in an amount of 0.001 to 50 parts by weight, more preferably 0.01 to 40 parts by weight per 100 parts by weight of a base polymer to be described just below. The sulfonium salt having formula (1) may be used alone or in admixture of two or more.
In one embodiment, the resist composition contains a base polymer. In the case of positive resist compositions, the base polymer comprises repeat units containing an acid labile group. The preferred repeat units containing an acid labile group are repeat units having the formula (a1) or repeat units having the formula (a2), which are also referred to as repeat units (a1) or (a2).
In formulae (a1) and (a2), RA is each independently hydrogen or methyl. X1 is a single bond, phenylene group, naphthylene group, or a C1-C12 linking group containing at least one moiety selected from ester bond, ether bond and lactone ring. The phenylene, naphthylene or linking group may contain at least one moiety selected from halogen, hydroxy, C1-C8 saturated hydrocarbyloxy and C2-C8 saturated hydrocarbylcarbonyloxy. X2 is a single bond, ester bond or amide bond. X3 is a single bond, ether bond or ester bond. R11 and R12 are each independently an acid labile group. R13 is hydroxy, halogen, trifluoromethyl, cyano or a C1-C6 saturated hydrocarbyl group. R14 is a single bond or a C1-C6alkanediyl group in which some —CH2— may be replaced by an ether bond or ester bond. The subscript “a” is 1 or 2, “b” is an integer of 0 to 4, and the sum of a+b is from 1 to 5.
Examples of the monomer from which repeat units (a1) are derived are shown below, but not limited thereto. Herein RA and R11 are as defined above.
Examples of the monomer from which repeat units (a2) are derived are shown below, but not limited thereto. Herein RA and R12 are as defined above.
The acid labile groups represented by R11 and R12 may be selected from a variety of such groups, for example, groups having the following formulae (AL-1) to (AL-3).
In formula (AL-1), c is an integer of 0 to 6. RL1 is a C4-C20, preferably C4-C15 tertiary hydrocarbyl group, a trihydrocarbylsilyl group in which each hydrocarbyl moiety is a C1-C6 saturated one, a C4-C20 saturated hydrocarbyl group containing a carbonyl moiety, ether bond or ester bond, or a group of formula (AL-3). Notably, the tertiary hydrocarbyl group is a group obtained from a tertiary hydrocarbon by eliminating hydrogen on the tertiary carbon.
The tertiary hydrocarbyl group RL1 may be saturated or unsaturated and branched or cyclic. Examples thereof include tert-butyl, tert-pentyl, 1,1-diethylpropyl, 1-ethylcyclopentyl, 1-butylcyclopentyl, 1-ethylcyclohexyl, 1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl, and 2-methyl-2-adamantyl. Examples of the trihydrocarbylsilyl group include trialkylsilyl groups such as trimethylsilyl, triethylsilyl, and dimethyl-tert-butylsilyl. The saturated hydrocarbyl group containing a carbonyl moiety, ether bond or ester bond may be straight, branched or cyclic, preferably cyclic and examples thereof include 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl, 5-methyl-2-oxooxolan-5-yl, 2-tetrahydropyranyl, and 2-tetrahydrofuranyl.
Examples of the acid labile group having formula (AL-1) include tert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-pentyloxycarbonyl, tert-pentyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl, 1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl, 1-ethylcyclopentyloxycarbonylmethyl, 1-ethyl-2-cyclopentenyloxycarbonyl, 1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl, 2-tetrahydropyranyloxycarbonylmethyl, and 2-tetrahydrofuranyloxycarbonylmethyl.
Other examples of the acid labile group having formula (AL-1) include groups having the formulae (AL-1)-1 to (AL-1)-10.
In formulae (AL-1)-1 to (AL-1)-10, c is as defined above. RL8 is each independently a C1-C10 saturated hydrocarbyl group or C6-C20 aryl group. RL9 is hydrogen or a C1-C10 saturated hydrocarbyl group. RL10 is a C2-C10 saturated hydrocarbyl group or C6-C20 aryl group. The saturated hydrocarbyl group may be straight, branched or cyclic.
In formula (AL-2), RL2 and RL3 are each independently hydrogen or a C1-C18, preferably C1-C10 saturated hydrocarbyl group. The saturated hydrocarbyl group may be straight, branched or cyclic and examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl and n-octyl.
RL4 is a C1-C18, preferably C1-C10 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Typical are C1-C18 saturated hydrocarbyl groups, in which some hydrogen may be substituted by hydroxy, alkoxy, oxo, amino or alkylamino. Examples of the substituted saturated hydrocarbyl group are shown below.
A pair of RL2 and RL3, RL2 and RL4, or RL3 and RL4 may bond together to form a ring with the carbon atom or carbon and oxygen atoms to which they are attached. RL2 and RL3, RL2 and RL4, or RL3 and RL4 that form a ring are each independently a C1-C18, preferably C1-C10 alkanediyl group. The ring thus formed is preferably of 3 to 10, more preferably 4 to 10 carbon atoms.
Of the acid labile groups having formula (AL-2), suitable straight or branched groups include those having formulae (AL-2)-1 to (AL-2)-69, but are not limited thereto.
Of the acid labile groups having formula (AL-2), suitable cyclic groups include tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl, tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl.
Also included are acid labile groups having the following formulae (AL-2a) and (AL-2b). The base polymer may be crosslinked within the molecule or between molecules with these acid labile groups.
In formulae (AL-2a) and (AL-2b), RL11 and RL12 are each independently hydrogen or a C1-C8 saturated hydrocarbyl group which may be straight, branched or cyclic. Also, RL11 and RL12 may bond together to form a ring with the carbon atom to which they are attached, and in this case, RL11 and RL12 are each independently a C1-C8 alkanediyl group. RL13 is each independently a C1-C10 saturated hydrocarbylene group which may be straight, branched or cyclic. The subscripts d and e are each independently an integer of 0 to 10, preferably 0 to 5, and f is an integer of 1 to 7, preferably 1 to 3.
In formulae (AL-2a) and (AL-2b), LA is a (f+1)-valent C1-C50 aliphatic saturated hydrocarbon group, (f+1)-valent C3-C50 alicyclic saturated hydrocarbon group, (f+1)-valent C6-C50 aromatic hydrocarbon group or (f+1)-valent C3-C50 heterocyclic group. In these groups, some constituent —CH2— may be replaced by a heteroatom-containing moiety, or some hydrogen may be substituted by a hydroxy, carboxy, acyl moiety or fluorine. LA is preferably a C1-C20 saturated hydrocarbylene, saturated hydrocarbon group (e.g., tri- or tetravalent saturated hydrocarbon group), or C6-C30 arylene group. The saturated hydrocarbon group may be straight, branched or cyclic. LB is —C(═O)—O—, —NH—C(═O)—O— or —NH—C(═O)—NH—.
Examples of the crosslinking acetal groups having formulae (AL-2a) and (AL-2b) include groups having the formulae (AL-2)-70 to (AL-2)-77.
In formula (AL-3), RL5 is hydrogen or a C1-C20 hydrocarbyl group which may contain a heteroatom such as oxygen, sulfur, nitrogen or fluorine. RL6 and RL7 are each independently a C1-C20 hydrocarbyl group which may contain a heteroatom such as oxygen, sulfur, nitrogen or fluorine. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof include C1-C20 alkyl groups, C3-C20 cyclic saturated hydrocarbyl groups, C2-C20 alkenyl groups, C3-C20 cyclic unsaturated hydrocarbyl groups, and C6-C10 aryl groups. A pair of RL5 and RL6, RL5 and RL7, or RL6 and RL7 may bond together to form a C3-C20 aliphatic ring with the carbon atom to which they are attached.
Examples of the group having formula (AL-3) include tert-butyl, 1,1-diethylpropyl, 1-ethylnorbornyl, 1-methylcyclopentyl, 1-ethylcyclopentyl, 1-isopropylcyclopentyl, 1-methylcyclohexyl, 2-(2-methyl)adamantyl, 2-(2-ethyl)adamantyl, and tert-pentyl.
Examples of the group having formula (AL-3) also include groups having the formulae (AL-3)-1 to (AL-3)-22.
In formulae (AL-3)-1 to (AL-3)-22, RL14 is each independently hydrogen, a C1-C5 aliphatic hydrocarbyl group or C6-C20 aryl group. RL15 and RL17 are each independently hydrogen or a C1-C20 saturated hydrocarbyl group. RL16 is a C6-C20 aryl group. The saturated hydrocarbyl group may be straight, branched or cyclic. Typical of the aryl group is phenyl. RL18 is fluorine, iodine, nitro or trifluoromethyl. RL19 is each independently hydrogen, fluorine, iodine, nitro, a C1-C8 saturated hydrocarbyl group or C1-C8 hydrocarbyloxy group, and g is an integer of 1 to 5.
Other examples of the acid labile group having formula (AL-3) include groups having the formulae (AL-3)-23 and (AL-3)-24. The base polymer may be crosslinked within the molecule or between molecules with these acid labile groups.
In formulae (AL-3)-23 and (AL-3)-24, RL14 is as defined above. RL20 is a C1-C20 (h+1)-valent saturated or unsaturated hydrocarbylene group or C6-C20 (h+1)-valent arylene group, which may contain a heteroatom such as oxygen, sulfur or nitrogen. The saturated or unsaturated hydrocarbylene group may be straight, branched or cyclic. The subscript h is an integer of 1 to 3.
Besides the foregoing acid labile groups, the aromatic-bearing acid labile groups described in JP 5407941, JP 5434983, JP 5565293, JP 5655755, and JP 5655756 are also useful.
The base polymer may further comprise repeat units (b) having a phenolic hydroxy group as an adhesive group. Examples of suitable monomers from which repeat units (b) are derived are given below, but not limited thereto. Herein RA is as defined above.
The base polymer may further comprise repeat units (c) having another adhesive group selected from hydroxy group (other than the foregoing phenolic hydroxy), lactone ring, sultone ring, ether bond, ester bond, sulfonate ester bond, carbonyl group, sulfonyl group, cyano group, and carboxy group. Examples of suitable monomers from which repeat units (c) are derived are given below, but not limited thereto. Herein RA is as defined above.
In another preferred embodiment, the base polymer may further comprise repeat units (d) derived from indene, benzofuran, benzothiophene, acenaphthylene, chromone, coumarin, and norbornadiene, or derivatives thereof. Suitable monomers are exemplified below.
Furthermore, the base polymer may comprise repeat units (e) derived from styrene, vinylnaphthalene, vinylanthracene, vinylpyrene, methyleneindene, vinylpyridine, vinylcarbazole, or derivatives thereof.
In a further embodiment, the base polymer may comprise repeat units (f) derived from an onium salt having a polymerizable unsaturated bond. Specifically, the base polymer may comprise repeat units of at least one type selected from repeat units having formula (f1), repeat units having formula (f2), repeat units having formula (f3), repeat units having formula (f4), and repeat units having formula (f5). These units are simply referred to as repeat units (f1), (f2), (f3), (f4) and (f5), which may be used alone or in combination of two or more types.
In formulae (f1) to (f5), RA is each independently hydrogen or methyl.
In formulae (f1) to (f3), Z1 is a single bond, C1-C6 aliphatic hydrocarbylene group, phenylene, naphthylene, or a C7-C18 group obtained by combining the foregoing, or —O—Z11—, —C(═O)—O—Z11— or —C(═O)—NH—Z11—. Z11 is a C1-C6 aliphatic hydrocarbylene group, phenylene, naphthylene, or a C7-C18 group obtained by combining the foregoing, which may contain a carbonyl moiety, ester bond, ether bond or hydroxy moiety. Z2 is a single bond or ester bond. Z3 is a single bond, —Z31—C(═O)—O—, —Z31—O—, or —Z31—O—C(═O)—. Z31 is a C1-C12 aliphatic hydrocarbylene group, phenylene group, or a C7-C18 group obtained by combining the foregoing, which may contain a carbonyl moiety, ester bond, ether bond, bromine or iodine. Z4 is methylene, 2,2,2-trifluoro-1,1-ethanediyl or carbonyl. Z5 is a single bond, methylene, ethylene, phenylene, fluorinated phenylene, trifluoromethyl-substituted phenylene, —O—Z51—, —C(═O)—O—Z51—, or —C(═O)—NH—Z51—. Z51 is a C1-C6 aliphatic hydrocarbylene group, phenylene, fluorinated phenylene, or trifluoromethyl-substituted phenylene group, which may contain a carbonyl moiety, ester bond, ether bond, halogen or hydroxy moiety. The aliphatic hydrocarbylene group represented by Z1, Z11, Z31 and Z51 may be saturated or unsaturated and straight, branched or cyclic.
In formulae (f4) and (f5), Z6 is a single bond, phenylene group, naphthylene ring, ester bond or amide bond.
In formula (f4), Z7A is a single bond or a C1-C24 divalent organic group which may contain at least one element selected from halogen, oxygen, nitrogen and sulfur.
The divalent organic group Z7A may be saturated or unsaturated and straight, branched or cyclic. Also included are C1-C24 hydrocarbylene groups in which some or all of the hydrogen atoms are substituted by iodine or bromine. Examples of the C1-C24 hydrocarbylene group include alkanediyl groups such as methanediyl, ethane-1,1-diyl, ethane-1,2-diyl, propane-1,3-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, octadecane-1,18-diyl, nonadecane-1,19-diyl, and eicosane-1,20-diyl; cyclic saturated hydrocarbylene groups such as cyclopentanediyl, methylcyclopentanediyl, dimethylcyclopentanediyl, trimethylcyclopentanediyl, tetramethylcyclopentanediyl, cyclohexanediyl, methylcyclohexanediyl, dimethylcyclohexanediyl, trimethylcyclohexanediyl, tetramethylcyclohexanediyl, norbornanediyl and adamantanediyl; arylene groups such as phenylene, methylphenylene, ethylphenylene, n-propylphenylene, isopropylphenylene, n-butylphenylene, isobutylphenylene, sec-butylphenylene, tert-butylphenylene, naphthylene, methylnaphthylene, ethylnaphthylene, n-propylnaphthylene, isopropylnaphthylene, n-butylnaphthylene, isobutylnaphthylene, sec-butylnaphthylene, tert-butylnaphthylene, biphenyldiyl, methylbiphenyldiyl and dimethylbiphenyldiyl; and combinations thereof. In the hydrocarbylene group Z7A, some or all of the hydrogen atoms may be substituted by a moiety containing at least one element selected from oxygen, nitrogen and sulfur, or some —CH2— may be replaced by a moiety containing at least one element selected from oxygen, nitrogen and sulfur, so that the group may contain a hydroxy moiety, ester bond, ether bond, amide bond, carbamate bond or urea bond.
In formula (f5), Z7B is a C1-C0 monovalent organic group which may contain at least one element selected from halogen, oxygen, nitrogen and sulfur.
The monovalent organic group Z7B may be saturated or unsaturated and straight, branched or cyclic. Also included are C1-C10 hydrocarbyl groups in which some or all of the hydrogen atoms are substituted by iodine or bromine. Examples of the C1-C10 hydrocarbyl group include C1-C10 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, 3-pentyl, tert-pentyl, neopentyl, n-hexyl, n-octyl, n-nonyl, and n-decyl; C3-C10 cyclic saturated hydrocarbyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, adamantyl, norbornyl, cyclopropylmethyl, cyclopropylethyl, cyclobutylmethyl, cyclobutylethyl, cyclopentylmethyl, cyclopentylethyl, cyclohexylmethyl, cyclohexylethyl, methylcyclopropyl, methylcyclobutyl, methylcyclopentyl, methylcyclohexyl, ethylcyclopropyl, ethylcyclobutyl, ethylcyclopentyl, and ethylcyclohexyl; C2-C10 alkenyl groups such as vinyl, 1-propenyl, 2-propenyl, butenyl, pentenyl, hexenyl, heptenyl, nonenyl, and decenyl; C2-C10 alkynyl groups such as ethynyl, propynyl, butynyl, pentynyl, hexynyl, heptynyl, octynyl, nonynyl, and decynyl; C3-C10 cyclic unsaturated aliphatic hydrocarbyl groups such as cyclopentenyl, cyclohexenyl, methylcyclopentenyl, methylcyclohexenyl, ethylcyclopentenyl, ethylcyclohexenyl, and norbornenyl; C6-C10 aryl groups such as phenyl, methylphenyl, ethylphenyl, n-propylphenyl, isopropylphenyl, n-butylphenyl, isobutylphenyl, sec-butylphenyl, tert-butylphenyl, and naphthyl; C7-C10 aralkyl groups such as benzyl, phenethyl, phenylpropyl and phenylbutyl; and combinations thereof. In the hydrocarbyl group Z7B, some or all of the hydrogen atoms may be substituted by a moiety containing at least one element selected from oxygen, nitrogen and sulfur, and some —CH2— may be replaced by a moiety containing at least one element selected from oxygen, nitrogen and sulfur, so that the group may contain a hydroxy, ester bond, ether bond, amide bond, carbamate bond, or urea bond.
In formulae (f4) and (f5), Z8 is a single bond, ether bond, ester bond, thioether bond, or a C1-C6 alkanediyl group.
In formula (f5), Z9 is a C1-C12 trivalent organic group which may contain at least one element selected from oxygen, nitrogen and sulfur. The trivalent organic group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof include groups obtained from C1-C12 hydrocarbylene groups by further eliminating one hydrogen. Examples of the C1-C12 hydrocarbylene groups include those exemplified above for the C1-C24 hydrocarbylene group, but of 1 to 12 carbon atoms. In the group Z9, some or all of the hydrogen atoms may be substituted by a moiety containing at least one element selected from oxygen, nitrogen and sulfur, and some —CH2— may be replaced by a moiety containing at least one element selected from oxygen, nitrogen and sulfur, so that the group may contain a hydroxy, ester bond, ether bond, amide bond, carbamate bond, or urea bond.
In formulae (f1) to (f5), R21 to R25 are each independently halogen or a C1-C20 hydrocarbyl group which may contain a heteroatom. Suitable halogen atoms include fluorine, chlorine, bromine and iodine. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as exemplified above for R2 to R4 in formula (1). In the foregoing hydrocarbyl groups, some or all of the hydrogen atoms may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, and some constituent —CH2— may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxy, fluorine, chlorine, bromine, iodine, cyano, nitro, carbonyl, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (—C(═O)—O—C(═O)—) or haloalkyl moiety. R23 and R24 may bond together to form a ring with the sulfur atom to which they are attached. Examples of the ring are as exemplified above for the ring that R2 and R3 in formula (a), taken together, form with the sulfur atom to which they are attached.
In formulae (f4) and (f5), R26 is each independently a C1-C10 saturated hydrocarbyl group, C6-C10 aryl group, fluorine, iodine, trifluoromethoxy, difluoromethoxy, cyano or nitro group.
In formulae (f4) and (f5), the circle R is a C6-C10 (j+2)-valent aromatic hydrocarbon group. Examples of the (j+2)-valent aromatic hydrocarbon group include groups obtained from aromatic hydrocarbons such as benzene and naphthalene by eliminating (j+2) number of hydrogen atoms.
In formulae (f4) and (f5), j is each independently an integer of 0 to 5.
In formula (f1), M− is a non-nucleophilic counter ion. Examples of the non-nucleophilic counter ion include halide ions such as chloride and bromide ions; fluoroalkylsulfonate ions such as triflate, 1,1,1-trifluoroethanesulfonate, and nonafluorobutanesulfonate; arylsulfonate ions such as tosylate, benzenesulfonate, 4-fluorobenzenesulfonate, and 1,2,3,4,5-pentafluorobenzenesulfonate; alkylsulfonate ions such as mesylate and butanesulfonate; imide ions such as bis(trifluoromethylsulfonyl)imide, bis(perfluoroethylsulfonyl)imide and bis(perfluorobutylsulfonyl)imide; methide ions such as tris(trifluoromethylsulfonyl)methide and tris(perfluoroethylsulfonyl)methide.
Also included are sulfonate ions having fluorine substituted at α-position as represented by the formula (f1-1) and sulfonate ions having fluorine substituted at α-position and trifluoromethyl at β-position as represented by the formula (f1-2).
In formula (f1-1), R31 is hydrogen or a C1-C20 hydrocarbyl group which may contain an ether bond, ester bond, carbonyl moiety, lactone ring, or fluorine atom. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as will be exemplified later for the hydrocarbyl group Rfa1 in formula (2A′).
In formula (f1-2), R32 is hydrogen, or a C1-C30 hydrocarbyl group or C2-C30 hydrocarbylcarbonyl group, which may contain an ether bond, ester bond, carbonyl moiety or lactone ring. The hydrocarbyl group and the hydrocarbyl moiety in the hydrocarbylcarbonyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as will be exemplified later for the hydrocarbyl group Rfa1 in formula (2A′).
Examples of the cation in the monomer from which repeat unit (f1) is derived are shown below, but not limited thereto. RA is as defined above.
Examples of the cation in repeat units (f2) to (f5) are as exemplified above for the cation in the sulfonium salt having formula (1).
Examples of the anion in the monomer from which repeat unit (f2) is derived are shown below, but not limited thereto. RA is as defined above.
Examples of the anion in the monomer from which repeat unit (f) is derived are shown below, but not limited thereto. RA is as defined above.
Examples of the anion in the monomer from which repeat unit (f4) or (f5) is derived are shown below, but not limited thereto. RA and XBI are as defined above.
Repeat units (f1) to (f5) have the function of acid generator. The binding of an acid generator to the polymer backbone is effective in restraining acid diffusion, thereby preventing a reduction of resolution due to blur by acid diffusion. Also, LWR and CDU are improved since the acid generator is uniformly distributed. When a base polymer comprising repeat units (f1) to (f5) is used, that is, in the case of polymer-bound acid generator, an acid generator of addition type (to be described later) may be omitted.
The base polymer for formulating the positive resist composition comprises repeat units (a1) or (a2) having an acid labile group as essential component and additional repeat units (b), (c), (d), (e), and (f) as optional components. A fraction of units (a1), (a2), (b), (c), (d), (e), and (f) is:
For the base polymer for formulating the negative resist composition, an acid labile group is not necessarily essential. The base polymer comprises repeat units (b), and optionally repeat units (c), (d), (e), and/or (f). A fraction of these units is: preferably 0<b≤1.0, 0≤c≤0.9, 0≤d≤0.8, 0≤e≤0.8, and 0≤f≤0.5; more preferably 0.2≤b≤1.0, 0≤c≤0.8, 0≤d≤0.7, 0≤e≤0.7, and 0≤f≤0.4; and even more preferably 0.3≤b≤1.0, 0≤c≤0.75, 0≤d≤0.6, 0≤e≤0.6, and 0≤f≤0.3. Notably, f=f1+f2+f3+f4+f5, meaning that unit (f) is at least one of units (f1) to (f5), and b+c+d+e+f=1.0.
The base polymer may be synthesized by any desired methods, for example, by dissolving monomers corresponding to the foregoing repeat units in an organic solvent, adding a radical polymerization initiator thereto, and heating for polymerization. Examples of the organic solvent which can be used for polymerization include toluene, benzene, tetrahydrofuran (THF), diethyl ether, dioxane, propylene glycol monomethyl ether, and γ-butyrolactone. Examples of the polymerization initiator used herein include 2,2′-azobisisobutyronitrile (AIBN), 2,2′-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2-azobis(2-methylpropionate), benzoyl peroxide, and lauroyl peroxide. Preferably the reaction temperature is 50 to 80° C., and the reaction time is 2 to 100 hours, more preferably 5 to 20 hours.
In the case of a monomer having a hydroxy group, the hydroxy group may be replaced by an acetal group susceptible to deprotection with acid, typically ethoxyethoxy, prior to polymerization, and the polymerization be followed by deprotection with weak acid and water. Alternatively, the hydroxy group may be replaced by an acetyl, formyl, pivaloyl or similar group prior to polymerization, and the polymerization be followed by alkaline hydrolysis.
When hydroxystyrene or hydroxyvinylnaphthalene is copolymerized, an alternative method is possible. Specifically, acetoxystyrene or acetoxyvinylnaphthalene is used instead of hydroxystyrene or hydroxyvinylnaphthalene, and after polymerization, the acetoxy group is deprotected by alkaline hydrolysis, for thereby converting the polymer product to hydroxystyrene or hydroxyvinylnaphthalene. For alkaline hydrolysis, a base such as aqueous ammonia or triethylamine may be used. Preferably the reaction temperature is −20° C. to 100° C., more preferably 0° C. to 60° C., and the reaction time is 0.2 to 100 hours, more preferably 0.5 to 20 hours.
The base polymer should preferably have a weight average molecular weight (Mw) in the range of 1,000 to 500,000, and more preferably 2,000 to 30,000, as measured by GPC versus polystyrene standards using tetrahydrofuran (THF) solvent. A Mw in the range ensures that a resist film has heat resistance and a high solubility in alkaline developer.
If a base polymer has a wide molecular weight distribution or dispersity (Mw/Mn), which indicates the presence of lower and higher molecular weight polymer fractions, there is a possibility that foreign matter is left on the pattern or the pattern profile is degraded. The influences of Mw and Mw/Mn become stronger as the pattern rule becomes finer. Therefore, the base polymer should preferably have a narrow dispersity (Mw/Mn) of 1.0 to 2.0, especially 1.0 to 1.5, in order to provide a resist composition suitable for micropatterning to a small feature size.
For forming a narrow dispersity polymer, not only ordinary radical polymerization, but living radical polymerization may also be employed. Suitable living radical polymerization processes include radical polymerization using nitroxide radicals, i.e., nitroxide-mediated radical polymerization (NMP), atom transfer radical polymerization (ATRP), and reversible addition-fragmentation chain transfer (RAFT) polymerization.
The base polymer may be a blend of two or more polymers which differ in compositional ratio, Mw or Mw/Mn.
The resist composition may comprise an acid generator capable of generating a strong acid (referred to as acid generator of addition type, hereinafter). As used herein, the term “strong acid” refers to a compound having a sufficient acidity to induce deprotection reaction of an acid labile group on the base polymer in the case of a chemically amplified positive resist composition, or a compound having a sufficient acidity to induce acid-catalyzed polarity switch reaction or crosslinking reaction in the case of a chemically amplified negative resist composition. The inclusion of such an acid generator ensures that the sulfonium salt having formula (1) functions as a quencher and the inventive resist composition functions as a chemically amplified positive or negative resist composition.
The acid generator is typically a compound (PAG) capable of generating an acid upon exposure to actinic ray or radiation. Although the PAG used herein may be any compound capable of generating an acid upon exposure to high-energy radiation, those compounds capable of generating sulfonic acid, imidic acid (imide acid) or methide acid are preferred. Suitable PAGs include sulfonium salts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxyimide, and oxime-O-sulfonate acid generators. Suitable PAGs are as exemplified in U.S. Pat. No. 7,537,880 (JP-A 2008-111103, paragraphs [0122]-[0142]).
As the PAG used herein, sulfonium salts having the formula (2-1) and iodonium salts having the formula (2-2) are also preferred.
In formulae (2-1) and (2-2), R101 to R105 are each independently halogen or a C1-C20 hydrocarbyl group which may contain a heteroatom. Suitable halogen atoms include fluorine, chlorine, bromine and iodine. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as exemplified above for the hydrocarbyl groups R2 to R4 in formula (1). In the hydrocarbyl group, some or all hydrogen atoms may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, and some —CH2— may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxy, fluorine, chlorine, bromine, iodine, cyano, nitro, carbonyl, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride, or haloalkyl moiety. R101 and R102 may bond together to form a ring with the sulfur atom to which they are attached. Examples of the ring are as exemplified above for the ring that R2 and R3 in formula (1), taken together, form with the sulfur atom to which they are attached.
Examples of the cation in the sulfonium salt having formula (2-1) are as exemplified above for the cation in the sulfonium salt having formula (1).
Examples of the cation in the iodonium salt having formula (2-2) are shown below, but not limited thereto.
In formulae (2-1) and (2-2), Xa− is an anion selected from the following formulae (2A) to (2D).
In formula (2A), Rfa is fluorine or a C1-C40 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as will be exemplified later for the hydrocarbyl group Rfa1 in formula (2A′).
Of the anions having formula (2A), an anion having the formula (2A′) is preferred.
In formula (2A′), RHF is hydrogen or trifluoromethyl, preferably trifluoromethyl.
Rfa1 is a C1-C38 hydrocarbyl group which may contain a heteroatom. As the heteroatom, oxygen, nitrogen, sulfur and halogen atoms are preferred, with oxygen being most preferred. Of the hydrocarbyl groups represented by Rfa1, those groups of 6 to 30 carbon atoms are preferred from the aspect of achieving a high resolution in forming patterns of fine feature size. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof include C1-C38 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, 2-ethylhexyl, nonyl, undecyl, tridecyl, pentadecyl, heptadecyl, and icosyl; C3-C38 cyclic saturated hydrocarbyl groups such as cyclopentyl, cyclohexyl, 1-adamantyl, 2-adamantyl, 1-adamantylmethyl, norbornyl, norbornylmethyl, tricyclodecanyl, tetracyclododecanyl, tetracyclododecanylmethyl, and dicyclohexylmethyl; C2-C38 unsaturated aliphatic hydrocarbyl groups such as allyl and 3-cyclohexenyl; C6-C38 aryl groups such as phenyl, 1-naphthyl and 2-naphthyl; C7-C38 aralkyl groups such as benzyl and diphenylmethyl; and combinations thereof.
In the foregoing hydrocarbyl groups, some or all hydrogen atoms may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, and some constituent —CH2— may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxy, fluorine, chlorine, bromine, iodine, cyano, nitro, carbonyl, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (—C(═O)—O—C(═O)—), or haloalkyl moiety. Examples of the heteroatom-containing hydrocarbyl group include tetrahydrofuryl, methoxymethyl, ethoxymethyl, methylthiomethyl, acetamidemethyl, trifluoroethyl, (2-methoxyethoxy)methyl, acetoxymethyl, 2-carboxy-1-cyclohexyl, 2-oxopropyl, 4-oxo-1-adamantyl, and 3-oxocyclohexyl.
With respect to the synthesis of the sulfonium salt having an anion of formula (2A′), reference may be made to JP-A 2007-145797, JP-A 2008-106045, JP-A 2009-007327, and JP-A 2009-258695. Also useful are the sulfonium salts described in JP-A 2010-215608, JP-A 2012-041320, JP-A 2012-106986, and JP-A 2012-153644.
Examples of the anion having formula (2A) include those exemplified as the anion having formula (1A) in JP-A 2018-197853.
In formula (2B), Rfb1 and Rfb2 are each independently fluorine or a C1-C40 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic, and examples thereof are as exemplified above for Rfa1 in formula (2A′). Preferably Rfb1 and Rfb2 are fluorine or C1-C4 straight fluorinated alkyl groups. Also, Rfb1 and Rfb2 may bond together to form a ring with the linkage: —CF2—SO2—N—SO2—CF2— to which they are attached. It is preferred that a combination of R11 and R12 be a fluorinated ethylene or fluorinated propylene group.
In formula (2C), Rfc1, Rfc2 and Rfc3 are each independently fluorine or a C1-C40 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic, and examples thereof are as exemplified above for Rfa1 in formula (2A′). Preferably Rfc1, Rfc2 and Rfc3 are fluorine or C1-C4 straight fluorinated alkyl groups. Also, Rfc1 and Rfc2 may bond together to form a ring with the linkage: —CF2—SO2—C—SO2—CF2— to which they are attached. It is preferred that a combination of Rfc1 and Rfc2 be a fluorinated ethylene or fluorinated propylene group.
In formula (2D), Rd is a C1-C40 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic, and examples thereof are as exemplified above for Rfa1 in formula (2A′).
With respect to the synthesis of the sulfonium salt having an anion of formula (2D), reference may be made to JP-A 2010-215608 and JP-A 2014-133723.
Examples of the anion having formula (1D) include those exemplified as the anion having formula (1D) in U.S. Pat. No. 11,022,883 (JP-A 2018-197853).
Notably, the compound having the anion of formula (2D) does not have fluorine at the α-position relative to the sulfo group, but two trifluoromethyl groups at the β-position. For this reason, it has a sufficient acidity to sever the acid labile groups in the base polymer. The compound is thus an effective PAG.
Compounds having the formula (3) are also useful as the PAG.
In formula (3), R201 and R202 are each independently halogen or a C1-C30 hydrocarbyl group which may contain a heteroatom. R203 is a C1-C30 hydrocarbylene group which may contain a heteroatom. Any two of R201, R202 and R203 may bond together to form a ring with the sulfur atom to which they are attached. Exemplary rings are as described above for the ring that R2 and R3 in formula (1), taken together, form with the sulfur atom to which they are attached.
The hydrocarbyl groups R201 and R202 may be saturated or unsaturated and straight, branched or cyclic. Examples thereof include C1-C30 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; C3-C30 cyclic saturated hydrocarbyl groups such as cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, oxanorbornyl, tricyclo[5.2.1.02,6]decyl, and adamantyl; C6-C30 aryl groups such as phenyl, methylphenyl, ethylphenyl, n-propylphenyl, isopropylphenyl, n-butylphenyl, isobutylphenyl, sec-butylphenyl, tert-butylphenyl, naphthyl, methylnaphthyl, ethylnaphthyl, n-propylnaphthyl, isopropylnaphthyl, n-butylnaphthyl, isobutylnaphthyl, sec-butylnaphthyl, tert-butylnaphthyl, and anthracenyl; and combinations thereof. In the hydrocarbyl group, some or all of the hydrogen atoms may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, or some constituent —CH2— may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxy, fluorine, chlorine, bromine, iodine, cyano, nitro, carbonyl, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (—C(═O)—O—C(═O)—) or haloalkyl moiety.
The hydrocarbylene group R203 may be saturated or unsaturated and straight, branched or cyclic. Examples thereof include C1-C30 alkanediyl groups such as methanediyl, ethane-1,1-diyl, ethane-1,2-diyl, propane-1,3-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, and heptadecane-1,17-diyl; C3-C30 cyclic saturated hydrocarbylene groups such as cyclopentanediyl, cyclohexanediyl, norbornanediyl and adamantanediyl; C6-C30 arylene groups such as phenylene, methylphenylene, ethylphenylene, n-propylphenylene, isopropylphenylene, n-butylphenylene, isobutylphenylene, sec-butylphenylene, tert-butylphenylene, naphthylene, methylnaphthylene, ethylnaphthylene, n-propylnaphthylene, isopropylnaphthylene, n-butylnaphthylene, isobutylnaphthylene, sec-butylnaphthylene and tert-butylnaphthylene; and combinations thereof. In the hydrocarbylene group, some or all of the hydrogen atoms may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, or some constituent —CH2— may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxy, fluorine, chlorine, bromine, iodine, cyano, nitro, carbonyl, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (—C(═O)—O—C(═O)—) or haloalkyl moiety. Of the heteroatoms, oxygen is preferred.
In formula (3), LA is a single bond, ether bond or a C1-C20 hydrocarbylene group which may contain a heteroatom. The hydrocarbylene group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as exemplified above for R203.
In formula (3), XA, XB, XC and XD are each independently hydrogen, fluorine or trifluoromethyl. At least one of XA, XB, XC and XD is fluorine or trifluoromethyl.
In formula (3), k is an integer of 0 to 3.
Of the PAGs having formula (3), those having the formula (3′) are preferred.
In formula (3′), LA is as defined above. XE is hydrogen or trifluoromethyl, preferably trifluoromethyl. R301, R302 and R303 are each independently hydrogen or a C1-C20 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as exemplified above for Rfa1 in formula (2A′). The subscripts x and y are each independently an integer of 0 to 5, and z is an integer of 0 to 4.
Examples of the PAG having formula (3) are as exemplified for the PAG having formula (2) in JP-A 2017-026980.
Of the foregoing PAGs, those having an anion of formula (2A′) or (2D) are especially preferred because of reduced acid diffusion and high solubility in the solvent. Also those having formula (3′) are especially preferred because of extremely reduced acid diffusion.
A sulfonium or iodonium salt having an anion containing an iodized or brominated aromatic ring may also be used as the PAG. Suitable are sulfonium and iodonium salts having the formulae (4-1) and (4-2).
In formulae (4-1) and (4-2), p is an integer of 1 to 3, q is an integer of 1 to 5, and r is an integer of 0 to 3, and 1≤q+r≤5. Preferably, q is 1, 2 or 3, more preferably 2 or 3, and r is 0, 1 or 2.
In formulae (4-1) and (4-2), XBI is iodine or bromine. A plurality of XBI may be the same or different when p and/or q is 2 or more.
L1 is a single bond, ether bond, ester bond, or a C1-C6 saturated hydrocarbylene group which may contain an ether bond or ester bond. The saturated hydrocarbylene group may be straight, branched or cyclic.
L2 is a single bond or a C1-C20 divalent linking group when p is 1, and a C1-C20 (p+1)-valent linking group which may contain oxygen, sulfur or nitrogen when p is 2 or 3.
R401 is a hydroxy group, carboxy group, fluorine, chlorine, bromine, amino group, or a C1-C20 hydrocarbyl, C1-C20 hydrocarbyloxy, C2-C20 hydrocarbylcarbonyl, C2-C20 hydrocarbyloxycarbonyl, C2-C20 hydrocarbylcarbonyloxy or C1-C20 hydrocarbylsulfonyloxy group, which may contain fluorine, chlorine, bromine, hydroxy, amino or ether bond, or —N(R401A)(R401B), —N(R401C)—C(═O)—R401D or —N(R401C)—C(═O)—O—R401D. R401A and R401B are each independently hydrogen or a C1-C6 saturated hydrocarbyl group. R401C is hydrogen or a C1-C6 saturated hydrocarbyl group which may contain halogen, hydroxy, C1-C6 saturated hydrocarbyloxy, C2-C6 saturated hydrocarbylcarbonyl or C2-C6 saturated hydrocarbylcarbonyloxy moiety. R401D is a C1-C16 aliphatic hydrocarbyl group, C6-C14 aryl group or C7-C15 aralkyl group, which may contain halogen, hydroxy, C1-C6 saturated hydrocarbyloxy, C2-C6 saturated hydrocarbylcarbonyl or C2-C6 saturated hydrocarbylcarbonyloxy moiety. The aliphatic hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. The hydrocarbyl, hydrocarbyloxy, hydrocarbylcarbonyl, hydrocarbyloxycarbonyl, hydrocarbylcarbonyloxy and hydrocarbylsulfonyloxy groups may be straight, branched or cyclic. A plurality of R401 may be the same or different when p and/or r is 2 or more. Of these, R401 is preferably hydroxy, —N(R401C)—C(═O)—R401D, —N(R401C)—C(═O)—O—R401D, fluorine, chlorine, bromine, methyl or methoxy.
In formulae (4-1) and (4-2), Rf1 to Rf4 are each independently hydrogen, fluorine or trifluoromethyl, at least one of Rf1 to Rf4 is fluorine or trifluoromethyl. Rf1 and Rf2, taken together, may form a carbonyl group. Preferably, both Rf3 and Rf4 are fluorine.
R402 to R406 are each independently halogen or a C1-C20 hydrocarbyl group which may contain a heteroatom. Suitable halogen atoms include fluorine, chlorine, bromine and iodine. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as exemplified above for the hydrocarbyl groups R2 to R4 in formula (1). In the hydrocarbyl group, some or all of the hydrogen atoms may be substituted by hydroxy, carboxy, halogen, cyano, nitro, mercapto, sultone ring, sulfo, or sulfonium salt-containing moiety, and some constituent —CH2— may be replaced by an ether bond, ester bond, carbonyl moiety, amide bond, carbonate bond or sulfonate ester bond. R402 and R403 may bond together to form a ring with the sulfur atom to which they are attached. Exemplary rings are as described above for the ring that R2 and R3 in formula (1), taken together, form with the sulfur atom to which they are attached.
Examples of the cation in the sulfonium salt having formula (4-1) include those exemplified above as the cation in the sulfonium salt having formula (1). Examples of the cation in the iodonium salt having formula (4-2) include those exemplified above as the cation in the iodonium salt having formula (2-2).
Examples of the anion in the onium salts having formulae (4-1) and (4-2) are shown below, but not limited thereto. Herein XBI is as defined above.
Sulfonium and iodonium salts of fluorobenzenesulfonic acid bonded with iodized benzoic acid as represented by the formulae (4-3) and (4-4) are also useful as the PAG.
In formulae (4-3) and (4-4), s is an integer of 1 to 5, t is an integer of 0 to 3, and u is an integer of 1 to 4.
In formulae (4-3) and (4-4), R411 is hydroxy, carboxy, alkoxycarbonyl, fluorine, chlorine, bromine, amino or a C1-C20 saturated hydrocarbyl group, C1-C20 saturated hydrocarbyloxy group, or C2-C20 saturated hydrocarbylcarbonyloxy group, which may contain fluorine, chlorine, bromine, hydroxy, amino or alkoxy, or —N(R411A)—C(═O)—R411B or —N(R411A)—C(═O)—O—R411B. R411A is hydrogen or a C1-C6 saturated hydrocarbyl group. R411B is a C1-C16 aliphatic hydrocarbyl group, C6-C14 aryl group, or C7-C15 aralkyl group, which may contain halogen, hydroxy, a C1-C6 saturated hydrocarbyloxy moiety, C2-C6 saturated hydrocarbylcarbonyl moiety, or C2-C6 saturated hydrocarbylcarbonyloxy moiety.
In formulae (4-3) and (4-4), L3 is a single bond or a C1-C20 divalent linking group which may contain oxygen, sulfur or nitrogen.
In formulae (4-3) and (4-4), Rf11 is fluorine or trifluoromethyl.
In formulae (4-3) and (4-4), R412 to R416 are each independently halogen or a C1-C20 hydrocarbyl group which may contain a heteroatom. Suitable halogen atoms include fluorine, chlorine, bromine and iodine. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as exemplified above for R2 to R4 in formula (1). In the hydrocarbyl group, some or all of the hydrogen atoms may be substituted by hydroxy, carboxy, halogen, cyano, nitro, mercapto, sultone ring, sulfo or sulfonium salt-containing moiety, and some —CH2— may be replaced by an ether bond, ester bond, carbonyl, amide bond, carbonate bond or sulfonate ester bond. R402 and R403 may bond together to form a ring with the sulfur atom to which they are attached. Examples of the ring are as exemplified above for the ring that R2 and R3 in formula (1), taken together, form with the sulfur atom to which they are attached.
Examples of the cation in the sulfonium salt having formula (4-3) are as exemplified above for the cation in the sulfonium salt having formula (1). Examples of the cation in the iodonium salt having formula (4-4) are as exemplified above for the cation in the iodonium salt having formula (2-2).
Examples of the anion in the onium salt having formula (4-3) or (4-4) are shown below, but not limited thereto.
When used, the acid generator of addition type is preferably added in an amount of 0.1 to 50 parts, and more preferably 1 to 40 parts by weight per 100 parts by weight of the base polymer. The acid generator may be used alone or in admixture. The resist composition functions as a chemically amplified positive resist composition when the base polymer includes any of repeat units (f1) to (f5) and/or the resist composition contains the acid generator of addition type.
[Organic solvent]
An organic solvent may be added to the resist composition. The organic solvent used herein is not particularly limited as long as the foregoing and other components are soluble therein. Examples of the organic solvent are described in JP-A 2008-111103, paragraphs [0144]-[0145] (U.S. Pat. No. 7,537,880). Exemplary solvents include ketones such as cyclohexanone, cyclopentanone, methyl-2-n-pentyl ketone and 2-heptanone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and diacetone alcohol (DAA); ethers such as propylene glycol monomethyl ether (PGME), ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; esters such as propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono-tert-butyl ether acetate; and lactones such as γ-butyrolactone, which may be used alone or in admixture.
The organic solvent is preferably added in an amount of 100 to 10,000 parts, and more preferably 200 to 8,000 parts by weight per 100 parts by weight of the base polymer.
In addition to the foregoing components, the resist composition may contain other components such as a surfactant, dissolution inhibitor, crosslinker, quencher other than the sulfonium salt having formula (1), water repellency improver and acetylene alcohol. Each of the other components may be used alone or in admixture.
Exemplary surfactants are described in JP-A 2008-111103, paragraphs [0165]-[0166]. Inclusion of a surfactant may improve or control the coating characteristics of the resist composition. The surfactant is preferably added in an amount of 0.0001 to 10 parts by weight per 100 parts by weight of the base polymer.
In the embodiment wherein the resist composition is of positive tone, the inclusion of a dissolution inhibitor may lead to an increased difference in dissolution rate between exposed and unexposed areas and a further improvement in resolution. The dissolution inhibitor is typically a compound having at least two phenolic hydroxy groups on the molecule, in which an average of from 0 to 100 mol % of all the hydrogen atoms on the phenolic hydroxy groups are replaced by acid labile groups or a compound having at least one carboxy group on the molecule, in which an average of 50 to 100 mol % of all the hydrogen atoms on the carboxy groups are replaced by acid labile groups, both the compounds having a molecular weight of 100 to 1,000, and preferably 150 to 800. Typical are bisphenol A, trisphenol, phenolphthalein, cresol novolac, naphthalenecarboxylic acid, adamantanecarboxylic acid, and cholic acid derivatives in which the hydrogen atom on the hydroxy or carboxy group is replaced by an acid labile group, as described in U.S. Pat. No. 7,771,914 (JP-A 2008-122932, paragraphs [0155]-[0178]).
When the resist composition is of positive tone and contains a dissolution inhibitor, the dissolution inhibitor is preferably added in an amount of 0 to 50 parts, more preferably 5 to 40 parts by weight per 100 parts by weight of the base polymer.
In the case of negative resist compositions, a negative pattern may be formed by adding a crosslinker to reduce the dissolution rate of exposed area. Suitable crosslinkers which can be used herein include epoxy compounds, melamine compounds, guanamine compounds, glycoluril compounds and urea compounds having substituted thereon at least one group selected from among methylol, alkoxymethyl and acyloxymethyl groups, isocyanate compounds, azide compounds, and compounds having a double bond such as an alkenyloxy group. These compounds may be used as an additive or introduced into a polymer side chain as a pendant. Hydroxy-containing compounds may also be used as the crosslinker.
Suitable epoxy compounds include tris(2,3-epoxypropyl) isocyanurate, trimethylolmethane triglycidyl ether, trimethylolpropane triglycidyl ether, and triethylolethane triglycidyl ether. Examples of the melamine compound include hexamethylol melamine, hexamethoxymethyl melamine, hexamethylol melamine compounds having 1 to 6 methylol groups methoxymethylated and mixtures thereof, hexamethoxyethyl melamine, hexaacyloxymethyl melamine, hexamethylol melamine compounds having 1 to 6 methylol groups acyloxymethylated and mixtures thereof. Examples of the guanamine compound include tetramethylol guanamine, tetramethoxymethyl guanamine, tetramethylol guanamine compounds having 1 to 4 methylol groups methoxymethylated and mixtures thereof, tetramethoxyethyl guanamine, tetraacyloxyguanamine, tetramethylol guanamine compounds having 1 to 4 methylol groups acyloxymethylated and mixtures thereof. Examples of the glycoluril compound include tetramethylol glycoluril, tetramethoxyglycoluril, tetramethoxymethyl glycoluril, tetramethylol glycoluril compounds having 1 to 4 methylol groups methoxymethylated and mixtures thereof, tetramethylol glycoluril compounds having 1 to 4 methylol groups acyloxymethylated and mixtures thereof. Examples of the urea compound include tetramethylol urea, tetramethoxymethyl urea, tetramethylol urea compounds having 1 to 4 methylol groups methoxymethylated and mixtures thereof, and tetramethoxyethyl urea.
Suitable isocyanate compounds include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate and cyclohexane diisocyanate. Suitable azide compounds include 1,1′-biphenyl-4,4′-bisazide, 4,4′-methylidenebisazide, and 4,4′-oxybisazide. Examples of the alkenyloxy group-containing compound include ethylene glycol divinyl ether, triethylene glycol divinyl ether, 1,2-propanediol divinyl ether, 1,4-butanediol divinyl ether, tetramethylene glycol divinyl ether, neopentyl glycol divinyl ether, trimethylol propane trivinyl ether, hexanediol divinyl ether, 1,4-cyclohexanediol divinyl ether, pentaerythritol trivinyl ether, pentaerythritol tetravinyl ether, sorbitol tetravinyl ether, sorbitol pentavinyl ether, and trimethylol propane trivinyl ether.
When the resist composition is of negative tone and contains a crosslinker, the crosslinker is preferably added in an amount of 0.1 to 50 parts, more preferably 1 to 40 parts by weight per 100 parts by weight of the base polymer.
The other quencher is typically selected from conventional basic compounds. Conventional basic compounds include primary, secondary, and tertiary aliphatic amines, mixed amines, aromatic amines, heterocyclic amines, nitrogen-containing compounds with carboxy group, nitrogen-containing compounds with sulfonyl group, nitrogen-containing compounds with hydroxy group, nitrogen-containing compounds with hydroxyphenyl group, alcoholic nitrogen-containing compounds, amide derivatives, imide derivatives, and carbamate derivatives. Also included are primary, secondary, and tertiary amine compounds, specifically amine compounds having a hydroxy group, ether bond, ester bond, lactone ring, cyano group, or sulfonate ester bond as described in JP-A 2008-111103, paragraphs [0146]-[0164], and compounds having a carbamate group as described in JP 3790649. Addition of a basic compound may be effective for further suppressing the diffusion rate of acid in the resist film or correcting the pattern profile.
Onium salts such as sulfonium, iodonium and ammonium salts of sulfonic acids which are not fluorinated at α-position as described in U.S. Pat. No. 8,795,942 (JP-A 2008-158339) and similar onium salts of carboxylic acid may also be used as the other quencher. While an α-fluorinated sulfonic acid, imide acid, and methide acid are necessary to deprotect the acid labile group of carboxylic acid ester, an α-non-fluorinated sulfonic acid and a carboxylic acid are released by salt exchange with an α-non-fluorinated onium salt. An α-non-fluorinated sulfonic acid and a carboxylic acid function as a quencher because they do not induce deprotection reaction.
Also useful are quenchers of polymer type as described in U.S. Pat. No. 7,598,016 (JP-A 2008-239918). The polymeric quencher segregates at the resist surface and thus enhances the rectangularity of resist pattern. When a protective film is applied as is often the case in the immersion lithography, the polymeric quencher is also effective for preventing a film thickness loss of resist pattern or rounding of pattern top.
When used, the other quencher is preferably added in an amount of 0 to 5 parts, more preferably 0 to 4 parts by weight per 100 parts by weight of the base polymer.
To the resist composition, a water repellency improver may also be added for improving the water repellency on surface of a resist film. The water repellency improver may be used in the topcoatless immersion lithography. Suitable water repellency improvers include polymers having a fluoroalkyl group and polymers having a specific structure with a 1,1,1,3,3,3-hexafluoro-2-propanol residue and are described in JP-A 2007-297590 and JP-A 2008-111103, for example. The water repellency improver to be added to the resist composition should be soluble in alkaline developers and organic solvent developers. The water repellency improver of specific structure with a 1,1,1,3,3,3-hexafluoro-2-propanol residue is well soluble in the developer. A polymer having an amino group or amine salt copolymerized as repeat units may serve as the water repellent additive and is effective for preventing evaporation of acid during PEB, thus preventing any hole pattern opening failure after development. An appropriate amount of the water repellency improver is 0 to 20 parts, preferably 0.5 to 10 parts by weight per 100 parts by weight of the base polymer.
Also, an acetylene alcohol may be blended in the resist composition. Suitable acetylene alcohols are described in JP-A 2008-122932, paragraphs [0179]-[0182]. An appropriate amount of the acetylene alcohol blended is 0 to 5 parts by weight per 100 parts by weight of the base polymer.
The resist composition is used in the fabrication of various integrated circuits. Pattern formation using the resist composition may be performed by well-known lithography processes. The process generally involves the steps of applying the resist composition onto a substrate to form a resist film thereon, exposing the resist film to high-energy radiation, and developing the exposed resist film in a developer. If necessary, any additional steps may be added.
Specifically, the resist composition is first applied onto a substrate on which an integrated circuit is to be formed (e.g., Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, or organic antireflective coating) or a substrate on which a mask circuit is to be formed (e.g., Cr, CrO, CrON, MoSi2, or SiO2) by a suitable coating technique such as spin coating, roll coating, flow coating, dipping, spraying or doctor coating. The coating is prebaked on a hotplate preferably at a temperature of 60 to 150° C. for 10 seconds to 30 minutes, more preferably at 80 to 120° C. for 30 seconds to 20 minutes. The resulting resist film is generally 0.01 to 2 μm thick.
The resist film is then exposed to a desired pattern of high-energy radiation such as UV, deep-UV, EB, EUV of wavelength 3 to 15 nm, x-ray, soft x-ray, excimer laser light, γ-ray or synchrotron radiation. When UV, deep-UV, EUV, x-ray, soft x-ray, excimer laser light, γ-ray or synchrotron radiation is used as the high-energy radiation, the resist film is exposed thereto directly or through a mask having a desired pattern in a dose of preferably about 1 to 200 mJ/cm2, more preferably about 10 to 100 mJ/cm2. When EB is used as the high-energy radiation, the resist film is exposed thereto directly or through a mask having a desired pattern in a dose of preferably about 0.1 to 300 μC/cm2, more preferably about 0.5 to 200 μC/cm2. It is appreciated that the inventive resist composition is suited in micropatterning using KrF excimer laser, ArF excimer laser, EB, EUV, x-ray, soft x-ray, γ-ray or synchrotron radiation, especially in micropatterning using EB or EUV.
After the exposure, the resist film may be baked (PEB) on a hotplate or in an oven preferably at 30 to 150° C. for 10 seconds to 30 minutes, more preferably at 50 to 120° C. for 30 seconds to 20 minutes.
After the exposure or PEB, the resist film is developed in a developer in the form of an aqueous base solution for 3 seconds to 3 minutes, preferably 5 seconds to 2 minutes by conventional techniques such as dip, puddle and spray techniques. A typical developer is a 0.1 to 10 wt %, preferably 2 to 5 wt % aqueous solution of tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), or tetrabutylammonium hydroxide (TBAH). In the case of positive tone, the resist film in the exposed area is dissolved in the developer whereas the resist film in the unexposed area is not dissolved. In this way, the desired positive pattern is formed on the substrate. In the case of negative tone, inversely the resist film in the exposed area is insolubilized whereas the resist film in the unexposed area is dissolved away.
In an alternative embodiment, a negative pattern can be obtained from the positive resist composition comprising a base polymer containing acid labile groups by effecting organic solvent development. The developer used herein is preferably selected from among 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methylacetophenone, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, butenyl acetate, isopentyl acetate, propyl formate, butyl formate, isobutyl formate, pentyl formate, isopentyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, methyl propionate, ethyl propionate, ethyl 3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, pentyl lactate, isopentyl lactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, phenyl acetate, benzyl acetate, methyl phenylacetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, ethyl phenylacetate, and 2-phenylethyl acetate, and mixtures thereof.
At the end of development, the resist film is rinsed. As the rinsing liquid, a solvent which is miscible with the developer and does not dissolve the resist film is preferred. Suitable solvents include alcohols of 3 to 10 carbon atoms, ether compounds of 8 to 12 carbon atoms, alkanes, alkenes, and alkynes of 6 to 12 carbon atoms, and aromatic solvents. Specifically, suitable alcohols of 3 to 10 carbon atoms include n-propyl alcohol, isopropyl alcohol, 1-butyl alcohol, 2-butyl alcohol, isobutyl alcohol, t-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, t-pentyl alcohol, neopentyl alcohol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-3-pentanol, cyclopentanol, 1-hexanol, 2-hexanol, 3-hexanol, 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 2-ethyl-1-butanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, 4-methyl-3-pentanol, cyclohexanol, and 1-octanol. Suitable ether compounds of 8 to 12 carbon atoms include di-n-butyl ether, diisobutyl ether, di-s-butyl ether, di-n-pentyl ether, diisopentyl ether, di-s-pentyl ether, di-t-pentyl ether, and di-n-hexyl ether. Suitable alkanes of 6 to 12 carbon atoms include hexane, heptane, octane, nonane, decane, undecane, dodecane, methylcyclopentane, dimethylcyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, cycloheptane, cyclooctane, and cyclononane. Suitable alkenes of 6 to 12 carbon atoms include hexene, heptene, octene, cyclohexene, methylcyclohexene, dimethylcyclohexene, cycloheptene, and cyclooctene. Suitable alkynes of 6 to 12 carbon atoms include hexyne, heptyne, and octyne. Suitable aromatic solvents include toluene, xylene, ethylbenzene, isopropylbenzene, t-butylbenzene and mesitylene.
Rinsing is effective for minimizing the risks of resist pattern collapse and defect formation. However, rinsing is not essential. If rinsing is omitted, the amount of solvent used may be reduced.
A hole or trench pattern after development may be shrunk by the thermal flow, RELACS® or DSA process. A hole pattern is shrunk by coating a shrink agent thereto, and baking such that the shrink agent may undergo crosslinking at the resist surface as a result of the acid catalyst diffusing from the resist layer during bake, and the shrink agent may attach to the sidewall of the hole pattern. The bake is preferably at a temperature of 70 to 180° C., more preferably 80 to 170° C., for a time of 10 to 300 seconds. The extra shrink agent is stripped and the hole pattern is shrunk.
Examples of the invention are given below by way of illustration and not by way of limitation. All parts are by weight (pbw).
Quenchers Q-1 to Q-16 having the structure shown below were used in resist compositions.
Base polymers (Polymers P-1 to P-4) of the composition shown below were obtained by dissolving selected monomers in THF solvent, effecting copolymerization reaction, pouring the reaction solution in methanol, washing the solid precipitate with hexane, isolation, and drying. The polymers were analyzed for composition by 1H-NMR spectroscopy and for Mw and Mw/Mn by GPC versus polystyrene standards using THF solvent.
Resist compositions were prepared by dissolving the selected components in a solvent in accordance with the recipe shown in Table 1, and filtering through a filter having a pore size of 0.2 μm. The resist compositions of Examples 1 to 18 and Comparative Example 1 were of positive tone whereas the resist compositions of Example 19 and Comparative Example 2 were of negative tone.
The components in Table 1 are as identified below.
Comparative Quencher: cQ-1
Each of the resist compositions in Table 1 was spin coated on a silicon substrate having a 20-nm coating of silicon-containing spin-on hard mask SHB-A940 (Shin-Etsu Chemical Co., Ltd., Si content 43 wt %) and prebaked on a hotplate at 100° C. for 60 seconds to form a resist film of 60 nm thick. Using an EUV scanner NXE3400 (ASML, NA 0.33, σ 0.9/0.6, quadrupole illumination), the resist film was exposed to EUV through a mask bearing a hole pattern having a pitch (on-wafer size) of 44 nm+20% bias. The resist film was baked (PEB) on a hotplate at the temperature shown in Table 1 for 60 seconds and developed in a 2.38 wt % TMAH aqueous solution for 30 seconds to form a hole pattern having a size of 22 nm in Examples 1 to 18 and Comparative Example 1, or a dot pattern having a size of 22 nm in Example 19 and Comparative Example 2.
The resist pattern was observed under CD-SEM (CG6300, Hitachi High-Technologies Corp.). The exposure dose that provides a hole or dot pattern of 22 nm size was measured and reported as sensitivity. The size of 50 holes or dots at that dose was measured, from which a 3-fold value (36) of the standard deviation (6) was computed and reported as CDU.
The resist composition is shown in Table 1 together with the sensitivity and CDU of EUV lithography.
It is demonstrated in Table 1 that resist compositions comprising a sulfonium salt of an iodized phenol compound have a high sensitivity and form patterns with improved CDU.
Japanese Patent Application No. 2023-195606 is incorporated herein by reference. Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-195606 | Nov 2023 | JP | national |
