Onium salt, chemically amplified resist composition, and patterning method

Abstract

To provide an onium salt for use in a chemically amplified resist composition that exhibits superior solvent solubility, high sensitivity, high contrast, and superior lithographic performance such as EL, LWR in photolithography based on high energy rays, a chemically amplified resist composition comprising the onium salt as a photoacid generator, and a patterning method using the chemically amplified resist composition.SOLUTION: The present invention provides an onium salt represented by the formula (1).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an onium salt, a chemically amplified resist composition, and a patterning method. [Background technology]

[0002] In recent years, with the increasing integration and speed of LSIs, there has been a growing demand for miniaturization of pattern rules. As a result, far ultraviolet lithography and extreme ultraviolet (EUV) lithography are considered promising next-generation microfabrication technologies. Among these, photolithography using ArF excimer laser light is an indispensable technology for ultra-fine processing of 0.13 μm or less.

[0003] ArF lithography began to be used partially for the fabrication of 130nm node devices and became the main lithography technology for 90nm node devices. Initially, 157nm lithography using an F2 laser was considered promising as the next 45nm node lithography technology, but development delays due to various problems were pointed out. As a result, ArF immersion lithography, which can achieve high resolution by inserting a liquid with a refractive index higher than air, such as water, ethylene glycol, or glycerin, between the projection lens and the wafer, and designing the numerical aperture (NA) of the projection lens to be 1.0 or higher, has rapidly emerged (Non-Patent Literature 1) and is now in the practical application stage. This immersion lithography requires a resist composition that is not easily eluted by water.

[0004] In ArF lithography, highly sensitive resist compositions that can achieve sufficient resolution with low exposure are required to prevent degradation of precise and expensive optical materials. The most common way to achieve this is to select components that are highly transparent at a wavelength of 193 nm. For example, polyacrylic acid and its derivatives, norbornene-maleic anhydride alternating polymers, polynorbornene, ring-opening metathesis polymers, and ring-opening metathesis polymer hydrogenated polymers have been proposed as base polymers, and some success has been achieved in improving the transparency of the resin itself.

[0005] In recent years, negative-tone resists developed using organic solvents have gained attention alongside positive-tone resists developed using alkaline aqueous solutions. To resolve extremely fine hole patterns that cannot be achieved with positive tones, negative patterns are formed by using a high-resolution positive-type resist composition and developing it with an organic solvent. Furthermore, research is underway to obtain twice the resolution by combining two development processes: alkaline aqueous solution development and organic solvent development. Conventional positive-type ArF resist compositions can be used as ArF resist compositions for negative-tone development with organic solvents, and pattern formation methods using such compositions are described in Patent Documents 1 to 3.

[0006] To adapt to the rapid miniaturization of recent years, the development of resist compositions is progressing daily, along with process technologies. Various photoacid generators have been investigated, and sulfonium salts consisting of triphenylsulfonium cations and perfluoroalkanesulfonic acid anions are commonly used. However, the generated acid, perfluoroalkanesulfonic acid, particularly perfluorooctanesulfonic acid (PFOS), is difficult to decompose, bioaccumulates, and poses toxicity concerns, making its application to resist compositions difficult. Currently, photoacid generators that produce perfluorobutanesulfonic acid are used. However, when this is used in resist compositions, the diffusion of the generated acid is large, making it difficult to achieve high resolution. To address this problem, various partially fluorine-substituted alkanesulfonic acids and their salts have been developed. For example, Patent Document 1 describes, as prior art, a photoacid generator that generates α,α-difluoroalkanesulfonic acid upon exposure, specifically di(4-tert-butylphenyl)iodonium 1,1-difluoro-2-(1-naphthyl)ethanesulfonate and a photoacid generator that generates α,α,β,β-tetrafluoroalkanesulfonic acid. However, although the fluorine substitution rate is reduced in all of these, they do not have decomposable substituents such as ester structures, making them insufficient from the standpoint of environmental safety due to their easy decomposition. Furthermore, there are limitations in molecular design for changing the size of the alkanesulfonic acid, and the starting materials containing fluorine atoms are expensive.

[0007] Furthermore, with the reduction in circuit line width, the effect of contrast degradation due to acid diffusion in resist compositions has become even more serious. This is because the pattern dimensions approach the acid diffusion length, leading to a decrease in mask fidelity and deterioration of pattern rectangularity due to a larger dimensional deviation on the wafer (mask error factor (MEF)) relative to the dimensional deviation of the mask. Therefore, in order to fully obtain the benefits of shorter wavelength and higher NA of the light source, it is necessary to increase the dissolution contrast or suppress acid diffusion more than with conventional materials. As one solution, it is possible to reduce acid diffusion by lowering the bake temperature, and as a result improve the MEF, but this inevitably leads to lower sensitivity.

[0008] Introducing bulky substituents or polar groups into photoacid generators is effective in suppressing acid diffusion. Patent document 4 describes a photoacid generator having 2-acyloxy-1,1,3,3,3-pentafluoropropane-1-sulfonic acid, which has excellent solubility and stability in solvents and allows for a wide range of molecular designs. In particular, photoacid generators having 2-(1-adamantyloxy)-1,1,3,3,3-pentafluoropropane-1-sulfonic acid with bulky substituents exhibit low acid diffusion. Patent documents 5 to 7 also describe photoacid generators with condensed ring lactones, sultones, or thiolactones introduced as polar groups. Although some performance improvement has been confirmed due to the acid diffusion suppression effect of introducing polar groups, it is still insufficient for advanced control of acid diffusion, and the lithography performance is not satisfactory when considering MEF, pattern shape, sensitivity, etc.

[0009] Introducing polar groups into the anion of a photoacid generator is effective in suppressing acid diffusion, but it is disadvantageous from the viewpoint of solvent solubility. Patent documents 8 and 9 describe attempts to improve solvent solubility by introducing alicyclic groups into the cation portion of the photoacid generator, specifically introducing cyclohexane rings and adamantane rings. Although solubility is improved by introducing such alicyclic groups, a certain number of carbon atoms is required to ensure solubility, and as a result the molecular structure of the photoacid generator becomes bulky, which degrades lithography performance such as line width roughness (LWR) and dimensional uniformity (CDU) when forming fine patterns.

[0010] Furthermore, because iodine atoms have very high absorption for EUV at a wavelength of 13.5 nm, the effect of generating secondary electrons from iodine atoms during exposure has been confirmed, and they are attracting attention in EUV lithography. Patent document 10 proposes a photoacid generator in which iodine atoms are introduced into an anion. Although some improvement in lithography performance has been confirmed with this, iodine atoms do not have high solubility in organic solvents, and precipitation in solvents is a concern.

[0011] To improve dissolution contrast, acid-unstable groups have been introduced into the anions or cations of photoacid generators (Patent Documents 11 and 12). Many of these have a structure in which a carboxyl group is protected by an acid-unstable group. Although the elimination reaction of the acid-unstable group by acid proceeds before and after exposure, the resulting polar group is a carboxyl group, which causes swelling in the developer during alkaline development and pattern collapse during fine pattern formation. To meet the demand for further miniaturization, the development of novel photoacid generators is important, and there is a need for photoacid generators that have well controlled acid diffusion, excellent solvent solubility, and are effective in suppressing pattern collapse. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2008-281974 [Patent Document 2] Japanese Patent Publication No. 2008-281975 [Patent Document 3] Patent No. 4554665 [Patent Document 4] Japanese Patent Publication No. 2007-145797 [Patent Document 5] Patent No. 5061484 [Patent Document 6] Japanese Patent Publication No. 2016-147879 [Patent Document 7] Japanese Patent Publication No. 2015-63472 [Patent Document 8] Patent No. 5573098 [Patent Document 9] Patent No. 6461919 [Patent Document 10] Patent No. 6720926 [Patent Document 11] Patent No. 5544078 [Patent Document 12] Patent No. 5609569 [Non-patent literature]

[0013] [Non-Patent Document 1] Journal of Photopolymer Science and Technology, Vol. 17, No. 4, p. 587-601 (2004) [Overview of the Initiative] [Problems that the invention aims to solve]

[0014] In response to the recent demand for high-resolution resist patterns, conventional resist compositions using sulfonium salt-type photoacid generators cannot adequately suppress acid diffusion, resulting in a degradation of lithography performance such as contrast, MEF, and LWR. Furthermore, during fine pattern formation, there is the problem of pattern collapse due to swelling.

[0015] The present invention has been made in view of the above circumstances, and aims to provide an onium salt used in a chemically amplified resist composition that is excellent in solvent solubility, high sensitivity, high contrast, and excellent lithography performance such as exposure margin (EL) and LWR, particularly in photolithography using high-energy beams such as KrF excimer laser light, ArF excimer laser light, electron beam (EB), and EUV; a chemically amplified resist composition containing the onium salt as a photoacid generator; and a pattern formation method using the chemically amplified resist composition. [Means for solving the problem]

[0016] As a result of diligent research to achieve the above objective, the inventors discovered that an onium salt with a specific structure exhibits excellent solvent solubility, and that a chemically amplified resist composition using this as a photoacid generator exhibits high sensitivity and high contrast, excellent lithography performance such as EL and LWR, and is extremely effective in suppressing pattern collapse during fine pattern formation. This led to the present invention.

[0017] That is, the present invention provides the following onium salt, chemically amplified resist composition, and patterning method. 1. An onium salt represented by the following formula (1).

Chemical formula

Chemical formula

Effects of the Invention

[0018] When pattern formation is performed using a chemically amplified resist composition containing the onium salt of the present invention as a photoacid generator, a resist pattern with high contrast, good sensitivity, excellent lithography performance such as MEF and LWR, and suppressed pattern collapse can be formed.

Modes for Carrying Out the Invention

[0019] [Onium Salt] The onium salt of the present invention is represented by the following formula (1).

Chemical Formula

[0020] In formula (1), n1 is 0 or 1. When n1 is 0, it represents a benzene ring, and when n1 is 1, it represents a naphthalene ring. From the perspective of solvent solubility, it is preferably a benzene ring where n1 is 0. n2 is an integer from 1 to 3. From the perspective of raw material procurement, n2 is preferably 1 or 2, and more preferably 1. n3 is an integer from 1 to 4. From the perspective of raw material procurement, n3 is preferably 1 or 2, and more preferably 1. n4 is an integer from 0 to 4. However, when n1 = 0, n2 + n3 + n4 ≤ 5, and when n1 = 1, n2 + n3 + n4 ≤ 7. n5 is an integer from 0 to 4, preferably an integer from 0 to 3, and more preferably 1.

[0021] In formula (1), R AL is an acid-labile group formed together with an adjacent oxygen atom. As the acid-labile group, those represented by the following formula (AL-1) or (AL-2) are preferred.

Chemical formula

[0022] In formula (AL-1), R 2 , R 3 and R 4 are each independently a hydrocarbyl group having 1 to 12 carbon atoms. A part of -CH2- of the hydrocarbyl group may be substituted with -O- or -S-. When the hydrocarbyl group contains an aromatic ring, a part or all of the hydrogen atoms of the aromatic ring may be substituted with a halogen atom, a cyano group, a nitro group, an alkyl group having 1 to 4 carbon atoms that may contain a halogen atom, or an alkoxy group having 1 to 4 carbon atoms that may contain a halogen atom. m1 is 0 or 1. * represents a bond to an adjacent -O-.

[0023] R 2 、R 3 and R 4The C1-C12 hydrocarbyl group represented by can be saturated or unsaturated, and can be linear, branched, or cyclic. Specific examples include C1-C12 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, n-decyl, n-undecyl, and n-dodecyl; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, norbornylmethyl, adamantyl, adamantylmethyl, and tricyclo[5.2.1.0 2,6 ] Decyl group, tetracyclo[6.2.1.1 3,6 .0 2,7 Examples include: cyclic saturated hydrocarbyl groups with 3 to 12 carbon atoms, such as the dodecyl group; alkenyl groups with 2 to 12 carbon atoms, such as the vinyl group, allyl group, propenyl group, butenyl group, pentenyl group, and hexenyl group; alkynyl groups with 2 to 12 carbon atoms, such as the ethynyl group, propynyl group, butynyl group, pentynyl group, and hexynyl group; cyclic unsaturated aliphatic hydrocarbyl groups with 3 to 12 carbon atoms, such as the cyclopentenyl group and cyclohexenyl group; aryl groups with 6 to 12 carbon atoms, such as the phenyl group, naphthyl group, and indanyl group; and aralkyl groups with 7 to 12 carbon atoms, such as the benzyl group, 1-phenylethyl group, and 2-phenylethyl group: and groups obtained by combining these.

[0024] Also, R 2 and R 3 However, they may bond to each other and form a ring with the carbon atoms to which they are bonded, and some of the -CH2- in the ring may be substituted with -O- or -S-. The ring formed in this case may be a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, a cyclooctane ring, a norbornane ring, an adamantane ring, or a tricyclo[5.2.1.0 2,6 ] Decane ring, tetracyclo[6.2.1.1 3,6 .0 2,7Examples include dodecane rings. In addition, some of the -CH2- in the ring may be substituted with -O- or -S-.

[0025] In formula (AL-2), R 5 and R 6 Each of these is independently a hydrogen atom or a hydrocarbyl group having 1 to 10 carbon atoms. 5 and R 6 The hydrocarbyl group, represented by , having 1 to 10 carbon atoms, can be saturated or unsaturated, and can be linear, branched, or cyclic. A specific example is R 2 , R 3 and R 4 Examples of hydrocarbyl groups with 1 to 12 carbon atoms, as represented by [formula], include those with 1 to 10 carbon atoms.

[0026] In formula (AL-2), R 7 This is a hydrocarbyl group having 1 to 20 carbon atoms, and some of the -CH2- atoms in the hydrocarbyl group may be substituted with -O- or -S- atoms. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include C1-C20 alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, n-hexyl group, n-octyl group, n-nonyl group, n-decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, heptadecyl group, octadecyl group, nonadecyl group, and eicosyl group; cyclopropyl group, cyclopentyl group, cyclohexyl group, cyclopropylmethyl group, 4-methylcyclohexyl group, cyclohexylmethyl group, norbornyl group, norbornylmethyl group, adamantyl group, adamantylmethyl group, and tricyclo[5.2.1.0 2,6 ] Decyl group, tetracyclo[6.2.1.1 3,6 .0 2,7] Cyclic saturated hydrocarbyl groups with 3 to 20 carbon atoms, such as dodecyl group; alkenyl groups with 2 to 20 carbon atoms, such as vinyl group, propenyl group, butenyl group, pentenyl group, hexenyl group; alkynyl groups with 2 to 20 carbon atoms, such as ethynyl group, propynyl group, butynyl group, pentynyl group, hexynyl group; cyclic unsaturated aliphatic hydrocarbyl groups with 3 to 20 carbon atoms, such as cyclopentenyl group, cyclohexenyl group, norbornenyl group; phenyl group, methylphenyl group, ethylphenyl group, n-propylphenyl group, isopropyl Examples include aryl groups having 6 to 20 carbon atoms, such as propylphenyl, n-butylphenyl, isobutylphenyl, sec-butylphenyl, tert-butylphenyl, naphthyl, methylnaphthyl, ethylnaphthyl, n-propylnaphthyl, isopropylnaphthyl, n-butylnaphthyl, isobutylnaphthyl, sec-butylnaphthyl, and tert-butylnaphthyl; aralkyl groups having 7 to 20 carbon atoms, such as benzyl and phenethyl; and groups obtained by combining these. Also, R 6 and R 7 and bond to each other, and the carbon atoms and L that they bond to are bonded together. C Together, they may form a heterocyclic group having 3 to 20 carbon atoms, and some of the -CH2- in the heterocyclic group may be substituted with -O- or -S-.

[0027] In formula (AL-2), L C It is either -O- or -S-.

[0028] In equation (AL-2), m2 is either 0 or 1. * represents a bond with an adjacent -O-.

[0029] Examples of acid-unstable groups represented by formula (AL-1) include, but are not limited to, those listed below. In the following formulas, * represents a bond with an adjacent -O-. [ka]

[0030] [ka]

[0031] [ka]

[0032] [ka]

[0033] [ka]

[0034] [ka]

[0035] [ka]

[0036] [ka]

[0037] [ka]

[0038] [ka]

[0039] [ka]

[0040] Examples of acid-unstable groups represented by formula (AL-2) include, but are not limited to, those listed below. In the following formulas, * represents a bond with an adjacent -O-. [ka]

[0041] [ka]

[0042] In equation (1), I and -OR AL These atoms are bonded to adjacent carbon atoms. By being adjacent to each other, -R AL The acidity of the aromatic alcohol after its elimination improves, and the solubility contrast is enhanced.

[0043] In formula (1), R 1This is a C1-C20 hydrocarbyl group which may contain heteroatoms. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples 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 eicosyl; cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, and 4-methyl Examples include cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; alkenyl groups having 2 to 20 carbon atoms, such as vinyl, allyl, propenyl, butenyl, and hexenyl; cyclic unsaturated hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclohexenyl; aryl groups having 2 to 20 carbon atoms, such as phenyl and naphthyl; aralkyl groups having 7 to 20 carbon atoms, such as benzyl, 1-phenylethyl, and 2-phenylethyl; and groups obtained by combining these. Of these, aryl groups are preferred. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing heteroatoms such as oxygen, sulfur, nitrogen, or halogen atoms, and some of the -CH2- groups of the hydrocarbyl group may be substituted with a group containing heteroatoms such as oxygen, sulfur, or nitrogen atoms, and as a result, the material may contain hydroxyl groups, cyano groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, carbonyl groups, ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic acid anhydrides (-C(=O)-OC(=O)-), haloalkyl groups, etc.

[0044] In formula (1), L A and L BThese are, independently, a single bond, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, or a carbamate bond. Of these, a single bond, an ether bond, or an ester bond is preferred.

[0045] In formula (1), X L This is a 1-40 carbon atom hydrocarbylene group which may contain single bonds or heteroatoms. The hydrocarbylene group may be linear, branched, or cyclic, and specific examples include an alkanediyl group and a cyclic saturated hydrocarbylene group. The heteroatom may be an oxygen atom, a nitrogen atom, a sulfur atom, etc.

[0046] X L The following are preferred as C1-C40 hydrocarbylene groups that may contain heteroatoms represented by the formula below. In the formula below, * represents L A and L B This represents a combination of two things. [ka]

[0047] [ka]

[0048] [ka]

[0049] Of these, X L -0~X L -3, X L -29~X L -34, X L -47~X L -49 is preferred, X L -0~X L -2, X L -29, X L -47 is more preferable.

[0050] In formula (1), Q1 and Q 2 Each of these is independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. A trifluoromethyl group is preferred as the fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms.

[0051] In formula (1), Q 3 and Q 4 Each of these is independently either a fluorine atom or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. A trifluoromethyl group is preferred as the fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms.

[0052] In formula (1), -[C(Q 1 )(Q 2 )] n5 -C(Q 3 )(Q 4 )-SO3 - The following are preferred examples of substructures represented by , but are not limited to these. In the following formula, * represents L B This represents a combination of two things. [ka]

[0053] Of these, Acid-1 to Acid-7 are preferred, and Acid-1 to Acid-3, Acid-6, and Acid-7 are more preferred.

[0054] The onium salt represented by formula (1) is preferably the one represented by formula (1A) below. [ka] (In the formula, R AL , R 1 , L A , L B , X L Q 1 Q 2 , n1~n5 and Z + (This is the same as above.)

[0055] The onium salt represented by formula (1A) is preferably the one represented by formula (1B) below. [ka] (In the formula, R AL , R 1 , L A , X L Q 1 Q 2 , n1~n5 and Z + (This is the same as above.)

[0056] The anions of the onium salt represented by formula (1) include, but are not limited to, those listed below. Furthermore, the substitution positions of substituents on the aromatic ring can be I and -OR. AL This does not apply if and are placed adjacent to each other. Note that in the following formula, Q 1 This is the same as described above. [ka]

[0057] [ka]

[0058] [ka]

[0059] [ka]

[0060] [ka]

[0061] [ka]

[0062] [Chemistry]

[0063] [Chemistry]

[0064] [Chemistry]

[0065] [Chemistry]

[0066] [Chemistry]

[0067] [Chemistry]

[0068] [Chemistry] [

[0069] [Chemistry]

[0070] In formula (1), Z + is represented by either of the following formulas (cation-1) or (cation-2). [Chemistry]

[0071] In formulas (cation-1) and (cation-2), R ct1 ~R ct5Each of these is independently a C1-C30 hydrocarbyl group which may contain heteroatoms. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl; cyclic saturated hydrocarbyl groups such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; alkenyl groups such as vinyl, allyl, propenyl, butenyl, and hexenyl; cyclic unsaturated hydrocarbyl groups such as cyclohexenyl; aryl groups such as phenyl, naphthyl, and thienyl; aralkyl groups such as benzyl, 1-phenylethyl, and 2-phenylethyl; and groups obtained by combining these, but aryl groups are preferred. Furthermore, some of the hydrogen atoms of the hydrocarbyl group may be substituted with heteroatom-containing groups such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and heteroatom-containing groups such as oxygen atoms, sulfur atoms, and nitrogen atoms may be interposed between the carbon atoms of these groups. As a result, the group may contain hydroxyl groups, cyano groups, carbonyl groups, ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic acid anhydrides (-C(=O)-OC(=O)-), haloalkyl groups, etc.

[0072] Also, R ct1 and R ct2 However, they may bond with each other to form a ring with the sulfur atom to which they are bonded. In this case, examples of sulfonium cations represented by formula (cation-1) include those represented by the following formula. [ka] (In the formula, the dashed line represents R ct3 (This is a combination of the two.)

[0073] Examples of the sulfonium cation represented by the formula (cation-1) include, but are not limited to, those shown below. [Chemical formula]

[0074] [Chemical formula]

[0075] [Chemical formula]

[0076] [Chemical formula]

[0077] [Chemical formula]

[0078] [Chemical formula]

[0079] [Chemical formula]

[0080] [Chemical formula]

[0081] [Chemical formula]

[0082] [Chemical formula]

[0083]

change

[0084]

change

[0085]

change

[0086]

change

[0087]

change

[0088]

change

[0089]

change

[0090]

change

[0091]

change

[0092]

change

[0093]

change

[0094] [ka]

[0095] [ka]

[0096] [ka]

[0097] [ka]

[0098] [ka]

[0099] Examples of iodonium cations represented by formula (cation-2) include, but are not limited to, those listed below. [ka]

[0100] [ka]

[0101] Specific examples of the onium salt of the present invention include any combination of the anion and cation described above.

[0102] The onium salt (1) of the present invention can be synthesized by known methods. As an example, a method for producing the onium salt represented by the following formula (PAG-1-ex) will be described. [ka] (In the formula, R AL , R 1 Q 1 ~Q 4 , n1~n5 and Z + This is the same as above. M + X is a countercation. - (This is an anti-anion.)

[0103] The first step involves hydrolyzing the nitrile groups in the raw material SM-1, which can be synthesized commercially or by known synthesis methods, with a base to obtain the intermediate In-1. The reaction can be carried out using known organic synthesis methods. Specifically, the raw material SM-1 is suspended in water or an ether-based solvent such as tetrahydrofuran (THF), and hydrolysis is carried out by adding a base. Alkali metal hydroxides such as sodium hydroxide and potassium hydroxide are preferred as the base. The reaction temperature is generally from room temperature to around the boiling point of the solvent used, but heating is preferable for smoother reaction. The reaction time is typically around 4 to 12 hours, although tracking the reaction using silica gel thin-layer chromatography (TLC) to complete the reaction is desirable for yield. Afterward, the reaction is stopped using dilute hydrochloric acid, the pH is made acidic, and the target product is extracted from the reaction mixture. Intermediate In-1 can then be obtained by conventional aqueous work-up. The obtained intermediate In-1 can be purified by conventional methods such as chromatography and recrystallization if necessary.

[0104] The second step is to obtain intermediate In-2 by the reaction of intermediate In-1 with starting material SM-2. Various condensing agents can be used when directly forming an ester bond between the carboxyl group of intermediate In-1 and the hydroxyl group of starting material SM-2. Examples of condensing agents that can be used include N,N'-dicyclohexylcarbodiimide, N,N'-diisopropylcarbodiimide, 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride. However, from the viewpoint of ease of removal of urea compounds produced as by-products after the reaction, it is preferable to use 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride. The reaction is carried out by dissolving intermediate In-1 and starting material SM-2 in a halogenated solvent such as methylene chloride and adding a condensing agent. Adding 4-dimethylaminopyridine (DMAP) as a catalyst can improve the reaction rate. The reaction time is typically around 12-24 hours, although it is desirable to monitor the reaction using TLC to complete it for optimal yield. After stopping the reaction, the intermediate In-2 can be obtained by removing any by-product urea compounds by filtration or washing with water, and then performing a standard aqueous work-up of the reaction mixture. The obtained intermediate In-2 can be purified by conventional methods such as chromatography or recrystallization, if necessary.

[0105] The third step is to use the obtained intermediate In-2 in Z + X - This is a process to obtain an onium salt (PAG-1-ex) by exchanging the onium salt (raw material SM-3) represented by X. - Chloride ions, bromide ions, iodide ions, or methyl sulfate anions are preferred as they facilitate quantitative exchange reactions. Confirmation of the reaction progress by TLC is desirable for yield. The onium salt (PAG-1-ex) can be obtained from the reaction mixture by conventional aqueous work-up. If necessary, it can be purified by conventional methods such as chromatography or recrystallization.

[0106] In the above scheme, the ion exchange in the third step can be easily carried out by known methods, for example, by referring to Japanese Patent Application Publication No. 2007-145797.

[0107] The above manufacturing method is merely an example, and the method for producing onium salt according to the present invention is not limited thereto.

[0108] A structural feature of the onium salt of the present invention is that it has an acid-unstable group bonded to the hydroxyl group on the aromatic ring of the anion and an iodine atom, both of which are bonded to adjacent carbon atoms. By introducing a tertiary alkyl or acetal structure as the acid-unstable group, lipophilicity is improved, and sufficient organic solvent solubility can be obtained despite the presence of an iodine atom. Therefore, there is no concern about precipitation in solvents with the onium salt of the present invention. The acid-unstable group in the exposed area undergoes a deprotection reaction with the generated acid, generating an aromatic hydroxyl group. This improves the contrast between the exposed and unexposed areas. In addition, the adjacent iodine atom has a large molecular weight, so when it is included in the anion, acid diffusion is reduced. Furthermore, because the absorption by the iodine atom at a wavelength of 13.5 nm EUV is very large, secondary electrons are generated from the iodine atom during exposure, resulting in high sensitivity. In addition, the iodine atom also has an electron-withdrawing effect, so I and -OR AL When two things are adjacent to each other, -OR AL The acidity of the phenols generated by the elimination of acid-unstable groups is improved, and their solubility in alkaline developers is enhanced. When the resist film is developed with an alkaline developer after exposure, the affinity between the generated aromatic hydroxyl groups and the alkaline developer is improved, allowing the exposed areas to be effectively removed by the developer. Furthermore, since phenols have a lower affinity for alkaline developers than carboxyl groups, swelling by the alkaline developer can be suppressed. This suppresses pattern collapse during fine pattern formation. Due to these synergistic effects, when using the onium salt of the present invention, high dissolution contrast, excellent LWR for line patterns and CDU for hole patterns, and pattern formation that is resistant to pattern collapse are possible, making it suitable as a positive-type resist composition.

[0109] The onium salt can be suitably used as a photoacid generator.

[0110] [Chemically Amplified Resist Composition] [(A) Photoacid Generator] The chemically amplified resist composition of the present invention contains (A) a photoacid generator comprising an onium salt represented by formula (1) as an essential component.

[0111] In the chemically amplified resist composition of the present invention, the content of the photoacid generator, which consists of an onium salt represented by formula (1) of component (A), is preferably 0.1 to 40 parts by mass, and more preferably 0.5 to 30 parts by mass, relative to 80 parts by mass of the base polymer described later. When the content of component (A) is within the above range, the sensitivity and resolution are good, and there is no risk of foreign matter problems occurring after development or peeling of the resist film, so it is preferable. The photoacid generator of component (A) may be used alone, or two or more types may be used in combination.

[0112] [(B) Base polymer] The chemically amplified resist composition of the present invention may include a base polymer as component (B). The (B) base polymer contains repeating units represented by the following formula (a1) (hereinafter also referred to as repeating unit a1). [ka]

[0113] In formula (a1), R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0114] In formula (a1), X 1 This refers to a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OX 11 -The phenylene group or naphthylene group may be substituted with a carbon-1 to carbon-10 alkoxy group or halogen atom which may contain a fluorine atom. 11This is a saturated hydrocarbylene group, phenylene group, or naphthylene group having 1 to 10 carbon atoms, and the saturated hydrocarbylene group may contain a hydroxyl group, an ether bond, an ester bond, or a lactone ring. * represents a bond with a carbon atom of the main chain.

[0115] In formula (a1), AL 1 This is an acid-unstable group. Examples of such acid-unstable groups include those described in Japanese Patent Publication No. 2013-80033 and Japanese Patent Publication No. 2013-83821.

[0116] Typically, the acid-unstable groups mentioned above are those represented by the following formulas (AL-3) to (AL-5). [ka] (In the equation, dashed lines represent connections.)

[0117] In equations (AL-3) and (AL-4), R L1 and R L2 Each of these is independently a saturated hydrocarbyl group having 1 to 40 carbon atoms, and may contain heteroatoms such as oxygen, sulfur, nitrogen, and fluorine atoms. The saturated hydrocarbyl group may be linear, branched, or cyclic. The saturated hydrocarbyl group is preferably one having 1 to 20 carbon atoms.

[0118] In formula (AL-3), k is an integer between 0 and 10, preferably between 1 and 5.

[0119] In formula (AL-4), R L3 and R L4 Each of these is independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 20 carbon atoms, and may contain heteroatoms such as oxygen, sulfur, nitrogen, or fluorine atoms. The hydrocarbyl group may be linear, branched, or cyclic. Also, R L2 , R L3 and R L4Any two of these may bond with each other to form a ring having 3 to 20 carbon atoms, together with the carbon atom to which they are bonded, or a carbon atom and an oxygen atom. The ring is preferably a ring having 4 to 16 carbon atoms, and an alicyclic ring is particularly preferred.

[0120] In formula (AL-5), R L5 , R L6 and R L7 Each of these is independently a saturated hydrocarbyl group having 1 to 20 carbon atoms, and may contain heteroatoms such as oxygen, sulfur, nitrogen, and fluorine atoms. The hydrocarbyl group may be linear, branched, or cyclic. Also, R L5 , R L6 and R L7 Any two of these may bond with each other to form a ring with 3 to 20 carbon atoms. The ring is preferably a ring with 4 to 16 carbon atoms, and an alicyclic ring is particularly preferred.

[0121] The repeating unit a1 can be, but is not limited to, the following. Note that in the following formula, R A and AL 1 This is the same as described above. [ka]

[0122] [ka]

[0123] [ka]

[0124] The base polymer may further contain repeating units represented by the following formula (a2) (hereinafter also referred to as repeating unit a2). [ka]

[0125] In formula (a2), R A X is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 2 The bond is either a single bond or *-C(=O)-O-. * represents a bond with a carbon atom in the main chain. 21 This is a C1-C20 hydrocarbyl group which may contain a halogen atom, a cyano group, a heteroatom, a C1-C20 hydrocarbyloxy group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyl group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyloxy group which may contain a heteroatom, or a C2-C20 hydrocarbyloxycarbonyl group which may contain a heteroatom. a is an integer from 0 to 4, preferably 0 or 1. AL 2 This is an acid-unstable group. The acid-unstable group is AL. 1 Examples of acid-unstable groups represented by the formula shown are similar to those exemplified above.

[0126] The repeating unit a2 can be, but is not limited to, the following. Note that in the following formula, R A and AL 2 This is the same as described above. [ka]

[0127] Preferably, the base polymer further contains a repeating unit represented by the following formula (b1) (hereinafter also referred to as repeating unit b1) or a repeating unit represented by the following formula (b2) (hereinafter also referred to as repeating unit b2). [ka]

[0128] In equations (b1) and (b2), R A These are, independently, a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1The bond is either a single bond or *-C(=O)-O-. * represents a bond with a carbon atom in the main chain. 21 R is a group having 1 to 20 carbon atoms that includes at least one structure selected from a hydrogen atom, or a hydroxyl group other than a phenolic hydroxyl group, a cyano group, a carbonyl group, a carboxyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, and a carboxylic acid anhydride (-C(=O)-OC(=O)-). 22 b is a C1-C20 hydrocarbyl group which may contain a halogen atom, a hydroxyl group, a nitro group, a heteroatom, a C1-C20 hydrocarbyloxy group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyl group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyloxy group which may contain a heteroatom, or a C2-C20 hydrocarbyloxycarbonyl group which may contain a heteroatom. b is an integer from 1 to 4. c is an integer from 0 to 4, where 1 ≤ b + c ≤ 5.

[0129] The repeating unit b1 can be, but is not limited to, the following. Note that in the following formula, R A This is the same as described above. [ka]

[0130] [ka]

[0131] [ka]

[0132] [ka]

[0133] [ka]

[0134]

change

[0135]

change

[0136]

change

[0137]

change

[0138]

change

[0139]

change

[0140]

change

[0141]

change

[0142]

change

[0143]

change

[0144] [ka]

[0145] The repeating unit b2 can be, but is not limited to, the following. Note that in the following formula, R A This is the same as described above. [ka]

[0146] [ka]

[0147] [ka]

[0148] [ka]

[0149] [ka]

[0150] As for the repeating unit b1 or b2, in ArF lithography, it is particularly preferable to have a lactone ring as a polar group, and in KrF lithography, EB lithography, and EUV lithography, it is preferable to have a phenol moiety.

[0151] The base polymer may further contain repeating units represented by any of the following formulas (c1) to (c4) (hereinafter also referred to as repeating units c1 to c4). [ka]

[0152] In formulas (c1) to (c4), RA These are, independently, a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1 This is a single bond or a phenylene group. 2 is *-C(=O)-OZ 21 -, *-C(=O)-NH-Z 21 -or *-OZ 21 - is Z 21 This is a divalent group obtained by combining an aliphatic hydrocarbylene group, a phenylene group, or a combination thereof, having 1 to 6 carbon atoms, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. 3 This refers to a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OZ 31 - is Z 31 This is an aliphatic hydrocarbylene group, a phenylene group, or a naphthylene group having 1 to 10 carbon atoms, and the aliphatic hydrocarbylene group may contain a hydroxyl group, an ether bond, an ester bond, or a lactone ring. 4 This is a single bond or *-Z 41 -C(=O)-O- Z 41 This is a hydrocarbylene group having 1 to 20 carbon atoms, which may contain heteroatoms. 5 This includes single bonds, methylene groups, ethylene groups, phenylene groups, fluorinated phenylene groups, trifluoromethyl groups, and *-C(=O)-OZ. 51 -, *-C(=O)-N(H)-Z 51 -or *-OZ 51 - is Z 51 This is a phenylene group substituted with an aliphatic hydrocarbylene group, phenylene group, fluorinated phenylene group, or trifluoromethyl group having 1 to 6 carbon atoms, and may also contain a carbonyl group, ester bond, ether bond, or hydroxyl group. * represents a bond with a carbon atom of the main chain.

[0153] Z 21 , Z 31 and Z 51The aliphatic hydrocarbylene group represented by can be linear, branched, or cyclic, and specific examples include methanediyl group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,1-diyl group, propane-1,2-diyl group, propane-1,3-diyl group, propane-2,2-diyl group, butane-1,1-diyl group, butane-1,2-diyl group, butane-1,3-diyl group, butane- Examples include alkanediyl groups such as 2,3-diyl group, butane-1,4-diyl group, 1,1-dimethylethane-1,2-diyl group, pentane-1,5-diyl group, 2-methylbutane-1,2-diyl group, and hexane-1,6-diyl group; cycloalkanediyl groups such as cyclopropanediyl group, cyclobutanediyl group, cyclopentanediyl group, and cyclohexanediyl group; and groups obtained by combining these.

[0154] Z 41 The hydrocarbylene group represented by can be saturated or unsaturated, and can be linear, branched, or cyclic. Specific examples are listed below, but are not limited to these. [ka] (In the equation, dashed lines represent connections.)

[0155] In formula (c1), R 31 and R 32Each of these is independently a hydrocarbyl group having 1 to 20 carbon atoms, which may contain heteroatoms. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include C1-C20 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl groups; C3-C20 cyclic saturated hydrocarbyl groups such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl groups; C2-C20 alkenyl groups such as vinyl, allyl, propenyl, butenyl, and hexenyl groups; C3-C20 cyclic unsaturated hydrocarbyl groups such as cyclohexenyl groups; C6-C20 aryl groups such as phenyl, naphthyl, and thienyl groups; C7-C20 aralkyl groups such as benzyl, 1-phenylethyl, and 2-phenylethyl groups; and groups obtained by combining these, but aryl groups are preferred. Furthermore, some of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing heteroatoms such as oxygen, sulfur, nitrogen, or halogen atoms, and some of the -CH2- of the hydrocarbyl group may be substituted with a group containing heteroatoms such as oxygen, sulfur, or nitrogen atoms, and as a result, it may contain a hydroxyl group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc.

[0156] Also, R 31 and R 32 These may bond with each other to form a ring with the sulfur atom to which they are bonded. In this case, the ring is defined as R in the explanation of formula (cation-1). ct1 and R ct2 Examples of rings that can be formed when these atoms bond together with the sulfur atom to which they bond are similar to those exemplified.

[0157] Examples of cations for the repeating unit c1 include, but are not limited to, those listed below. Note that in the following formula, R A This is the same as described above. [ka]

[0158] [ka]

[0159] [ka]

[0160] [ka]

[0161] [ka]

[0162] [ka]

[0163] [ka]

[0164] In formula (c1), M - is a non-nucleophilic counterion. The non-nucleophilic counterion is, Halogen ions such as chloride ions and bromide ions, Sulfonate anions, imidoate anions, and methidoate anions are preferred. Specific examples of the sulfonate anions (sulfonate ions) include: ,toExamples include fluoroalkyl sulfonate ions such as reflate ions, 1,1,1-trifluoroethanesulfonate ions, and nonafluorobutanesulfonate ions; aryl sulfonate ions such as tosylate ions, benzenesulfonate ions, 4-fluorobenzenesulfonate ions, and 1,2,3,4,5-pentafluorobenzenesulfonate ions; and alkyl sulfonate ions such as mesylate ions and butanesulfonate ions. Specific examples of the aforementioned imido acid anions (imido ions) include bis(trifluoromethylsulfonyl)imide ions, bis(perfluoroethylsulfonyl)imide ions, and bis(perfluorobutylsulfonyl)imide ions. Specific examples of the aforementioned methido acid anions (methido ions) include ,to Examples include ris(trifluoromethylsulfonyl)methide ion and tris(perfluoroethylsulfonyl)methide ion.

[0165] Other examples of the aforementioned non-nucleophilic counterions include anions represented by any of the following formulas (c1-1) to (c1-4). [ka]

[0166] In formula (c1-1), R fa R is a C1-C40 hydrocarbyl group which may contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. A specific example is R in formula (c1-1-1) described later. fa1 Examples of hydrocarbyl groups represented by the symbol shown are similar to those exemplified.

[0167] The anion represented by formula (c1-1) is preferably the one represented by the following formula (c1-1-1). [ka]

[0168] In formula (c1-1-1), Q 11 and Q 12 Each of these is independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms, but to improve solvent solubility, it is preferable that at least one of them be a trifluoromethyl group. e is an integer from 0 to 4, but it is particularly preferable that it be 1. R fa1 This is a hydrocarbyl group having 1 to 35 carbon atoms, which may contain heteroatoms. The heteroatoms are preferably oxygen atoms, nitrogen atoms, sulfur atoms, halogen atoms, etc., with oxygen atoms being more preferred. From the viewpoint of obtaining high resolution in fine pattern formation, the hydrocarbyl group having 6 to 30 carbon atoms is particularly preferred.

[0169] In formula (c1-1-1), R fa1 Hydrocarbyl groups having 1 to 35 carbon atoms, represented by , may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include alkyl groups having 1 to 35 carbon atoms 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 eicosyl; cyclopentyl, cyclohexyl, 1-adamantyl, 2-adamantyl, 1-adamantylmethyl, norbornyl, nor Examples include cyclic saturated hydrocarbyl groups with 3 to 35 carbon atoms, such as bornylmethyl group, tricyclodecyl group, tetracyclododecyl group, tetracyclododecylmethyl group, and dicyclohexylmethyl group; unsaturated aliphatic hydrocarbyl groups with 2 to 35 carbon atoms, such as allyl group and 3-cyclohexenyl group; aryl groups with 6 to 35 carbon atoms, such as phenyl group, 1-naphthyl group, 2-naphthyl group, and 9-fluorenyl group; aralkyl groups with 7 to 35 carbon atoms, such as benzyl group and diphenylmethyl group; and groups obtained by combining these.

[0170] Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom, nitrogen atom, or halogen atom, and some of the -CH2- of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom, or nitrogen atom, and as a result, it may contain a hydroxyl group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, a carbonyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc. Examples of hydrocarbyl groups containing heteroatoms include tetrahydrofuryl group, methoxymethyl group, ethoxymethyl group, methylthiomethyl group, acetamidomethyl group, trifluoroethyl group, (2-methoxyethoxy)methyl group, acetoxymethyl group, 2-carboxy-1-cyclohexyl group, 2-oxopropyl group, 4-oxo-1-adamantyl group, and 3-oxocyclohexyl group.

[0171] In formula (c1-1-1), L a1 The bond can be a single bond, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, or a carbamate bond, but from a synthetic viewpoint, an ether bond or an ester bond is preferred, and an ester bond is even more preferred.

[0172] The anions represented by formula (c1-1) include, but are not limited to, those listed below. Note that in the formula below, Q 11 This is the same as above, and Ac is an acetyl group. [ka]

[0173] [ka]

[0174] [ka]

[0175] [ka]

[0176] [ka]

[0177] [ka]

[0178] [ka]

[0179] [ka]

[0180] [ka]

[0181] [ka]

[0182] In formula (c1-2), R fb1 and R fb2 Each of these is a hydrocarbyl group having 1 to 40 carbon atoms, which may independently contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. A specific example is R in formula (c1-1-1). fa1 Examples of hydrocarbyl groups represented by R include those similar to those exemplified. fb1 and R fb2 Preferably, R is a fluorine atom or a linear fluorinated alkyl group having 1 to 4 carbon atoms. fb1 and R fb2These are bonded to each other, and the groups to which they bond are (-CF2-SO2-N - It may form a ring with -SO2-CF2-), in which case R fb1 and R fb2 The group obtained by the bonding of these two elements is preferably a fluorinated ethylene group or a fluorinated propylene group.

[0183] In formula (c1-3), R fc1 , R fc2 and R fc3 Each of these is a hydrocarbyl group having 1 to 40 carbon atoms, which may independently contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. A specific example is R in formula (c1-1-1). fa1 Examples of hydrocarbyl groups represented by R include those similar to those exemplified. fc1 , R fc2 and R fc3 Preferably, R is a fluorine atom or a linear fluorinated alkyl group having 1 to 4 carbon atoms. fc1 and R fc2 These are bonded to each other, and the groups to which they bond are (-CF2-SO2-C - It may form a ring with -SO2-CF2-), in which case R fc1 and R fc2 The group obtained by the bonding of these two elements is preferably a fluorinated ethylene group or a fluorinated propylene group.

[0184] In formula (c1-4), R fd R is a hydrocarbyl group having 1 to 40 carbon atoms, which may contain heteroatoms. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. A specific example is R in formula (c1-1-1). fa1 Examples of hydrocarbyl groups represented by the same formula as those exemplified above include those shown.

[0185] The anions represented by formula (c1-4) include, but are not limited to, those listed below. [ka]

[0186] [ka]

[0187] Examples of the aforementioned non-nucleophilic counterions include anions having an aromatic ring substituted with an iodine or bromine atom. Such anions are represented by the following formulas (c1-5). [ka]

[0188] In equation (c1-5), x is an integer satisfying 1 ≤ x ≤ 3. y and z are integers satisfying 1 ≤ y ≤ 5, 0 ≤ z ≤ 3, and 1 ≤ y + z ≤ 5. y is preferably an integer satisfying 1 ≤ y ≤ 3, and more preferably 2 or 3. z is preferably an integer satisfying 0 ≤ z ≤ 2.

[0189] In formula (c1-5), X BI x is an iodine atom or a bromine atom, and when x and / or y are 2 or more, they may be the same or different from each other.

[0190] In formula (c1-5), L 11 This is a saturated hydrocarbylene group having 1 to 6 carbon atoms, which may contain a single bond, an ether bond, or an ester bond, or an ether bond or an ester bond. The saturated hydrocarbylene group may be linear, branched, or cyclic.

[0191] In formula (c1-5), L 12 When x is 1, it is a single bond or a divalent linking group having 1 to 20 carbon atoms, and when x is 2 or 3, it is a (x+1) valent linking group having 1 to 20 carbon atoms, and the linking group may contain an oxygen atom, a sulfur atom, or a nitrogen atom.

[0192] In formula (c1-5), R feThis may include a hydroxyl group, a carboxyl group, a fluorine atom, a chlorine atom, a bromine atom, or an amino group, or a fluorine atom, a chlorine atom, a bromine atom, a hydroxyl group, an amino group, or an ether bond, and may contain a C1-C20 hydrocarbyl group, a C1-C20 hydrocarbyloxy group, a C2-C20 hydrocarbylcarbonyl group, a C2-C20 hydrocarbyloxycarbonyl group, a C2-C20 hydrocarbylcarbonyloxy group, or a C1-C20 hydrocarbylsulfonyloxy group, or -N(R feA )(R feB ), -N(R feC )-C(=O)-R feD Or -N(R feC )-C(=O)-OR feD That is. R feA and R feB Each of these is independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms. feC R is a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms, and may also contain a halogen atom, a hydroxyl group, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyl group having 2 to 6 carbon atoms, or a saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms. feD This is an aliphatic hydrocarbyl group having 1 to 16 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 15 carbon atoms, and may contain a halogen atom, a hydroxyl group, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyl group having 2 to 6 carbon atoms, or a saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms. The aliphatic hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. The hydrocarbyl group, hydrocarbyloxy group, hydrocarbylcarbonyl group, hydrocarbyloxycarbonyl group, hydrocarbylcarbonyloxy group, and hydrocarbylsulfonyloxy group may be linear, branched, or cyclic. When x and / or z is 2 or more, each R fe They may be the same or different from one another.

[0193] Of these, R feExamples include hydroxyl groups, -N(R feC )-C(=O)-R feD , -N(R feC )-C(=O)-OR feD Fluorine atoms, chlorine atoms, bromine atoms, methyl groups, methoxy groups, etc. are preferred.

[0194] In formula (c1-5), Rf 11 ~Rf 14 Each of these is independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, but at least one of these is either a fluorine atom or a trifluoromethyl group. Also, Rf 11 and Rf 12 These may combine to form a carbonyl group. In particular, Rf 13 and Rf 14 It is preferable that both are fluorine atoms.

[0195] The anions represented by formula (c1-5) include, but are not limited to, those listed below. Note that in the following formula, X BI This is the same as described above. [ka]

[0196] [ka]

[0197] [ka]

[0198] [ka]

[0199] [ka]

[0200]

change

[0201]

change

[0202]

change

[0203]

change

[0204]

change

[0205]

change

[0206]

change

[0207]

change

[0208]

change

[0209]

change

[0210]

change

[0211] [ka]

[0212] [ka]

[0213] [ka]

[0214] [ka]

[0215] [ka]

[0216] [ka]

[0217] [ka]

[0218] As the non-nucleophilic counterion, you can also use a fluorobenzenesulfonic acid anion bonded to an aromatic group containing an iodine atom as described in Japanese Patent No. 6648726, an anion having a mechanism for decomposition by acid as described in International Publication No. 2021 / 200056 and Japanese Patent Application Publication No. 2021-70692, an anion having a cyclic ether group as described in Japanese Patent Application Publication No. 2018-180525 and Japanese Patent Application Publication No. 2021-35935, or an anion as described in Japanese Patent Application Publication No. 2018-92159.

[0219] As the non-nucleophilic counterions, anions of bulky benzenesulfonic acid derivatives that do not contain fluorine atoms, as described in Japanese Patent Publication No. 2006-276759, Japanese Patent Publication No. 2015-117200, Japanese Patent Publication No. 2016-65016, and Japanese Patent Publication No. 2019-202974, as well as benzenesulfonic acid anions or alkylsulfonic acid anions that do not contain fluorine atoms bonded to an aromatic group containing an iodine atom, as described in Japanese Patent Publication No. 6645464.

[0220] As the non-nucleophilic counterion, other options include the bissulfonic acid anion described in Japanese Patent Publication No. 2015-206932, the sulfonamide or sulfonimide anion described in International Publication No. 2020 / 158366, which has a sulfonic acid on one end and a different sulfonamide or sulfonimide on the other, and the sulfonate anion described in Japanese Patent Publication No. 2015-24989.

[0221] In equations (c2) and (c3), L 1 These are single bonds, ether bonds, ester bonds, carbonyl groups, sulfonic acid ester bonds, carbonate bonds, or carbamate bonds. Of these, ether bonds, ester bonds, and carbonyl groups are preferred from a synthetic viewpoint, and ester bonds and carbonyl groups are more preferred.

[0222] In formula (c2), Rf 1 and Rf 2 Each of these is independently a fluorine atom or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Of these, Rf 1 and Rf 2 To increase the acid strength of the generated acid, it is preferable that all atoms be fluorine atoms. Rf 3 and Rf 4 These are, independently, a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Of these, Rf is used to improve solvent solubility. 3 and Rf 4 At least one of them is preferably a trifluoromethyl group.

[0223] In formula (c3), Rf 5 and Rf 6 Each of these is independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. However, all Rf 5 and Rf 6 These cannot simultaneously become hydrogen atoms. Of these, Rf 5 and Rf 6 At least one of them is preferably a trifluoromethyl group.

[0224] In equations (c2) and (c3), d is an integer between 0 and 3, but 1 is preferred.

[0225] The following are some examples of anions that can be used as repeating units c2, but they are not limited to these. Note that in the following formula, R A This is the same as described above. [ka]

[0226] [ka]

[0227] [ka]

[0228] [ka]

[0229] [ka]

[0230] [ka]

[0231] Examples of anions with repeating unit c3 include, but are not limited to, those listed below. Note that in the following formula, R A This is the same as described above. [ka]

[0232] [ka]

[0233] [ka]

[0234] The repeating unit anions represented by formula (c4) include, but are not limited to, the following. Note that in the following formula, R A This is the same as described above. [ka]

[0235] In formulas (c2) to (c4), A+ is an onium cation. Examples of the onium cation include ammonium cations, sulfonium cations, and iodonium cations, but sulfonium cations and iodonium cations are preferred. Specific examples of these include those exemplified as the cations represented by formula (cation-1) and formula (cation-2), and those exemplified as the cation represented by formula (cation-3) described later. but, This is not limited to these.

[0236] Specific structural examples of repeating units c1-c4 include any combination of the anions and cations mentioned above.

[0237] Of the repeating units c1 to c4, repeating units c2, c3, and c4 are preferred from the viewpoint of controlling acid diffusion, repeating units c2 and c4 are more preferred from the viewpoint of the acid strength of the generated acid, and repeating unit c2 is even more preferred from the viewpoint of solvent solubility.

[0238] The base polymer may further contain repeating units (hereinafter also referred to as repeating unit d) having a structure in which a hydroxyl group is protected by an acid-unstable group. The repeating unit d is not particularly limited as long as it has one or more structures in which a hydroxyl group is protected and the protecting group decomposes upon the action of an acid to generate a hydroxyl group, but it is preferably represented by the following formula (d1). [ka]

[0239] In formula (d1), R A This is the same as above. R 41 R is a (f+1) valent hydrocarbon group having 1 to 30 carbon atoms, which may contain heteroatoms. 42 f is an acid-unstable group. f is an integer between 1 and 4.

[0240] In formula (d1), R 42 The acid-unstable group represented by can be any group that is deprotected by the action of an acid and generates a hydroxyl group. 42 The structure is not particularly limited, but acetal structures, ketal structures, alkoxycarbonyl groups, and alkoxymethyl groups represented by the following formula (d2) are preferred, and alkoxymethyl groups represented by the following formula (d2) are particularly preferred. [ka] (In the equation, the dashed line represents a coupling. R 43 (This refers to a hydrocarbyl group with 1 to 15 carbon atoms.)

[0241] R 42Examples of the acid-labile group represented by [Chemical Formula 1], the alkoxymethyl group represented by Formula (d2), and the repeating unit d are the same as those exemplified in the description of the repeating unit d described in JP-A-2020-111564.

[0242] The base polymer may further contain a repeating unit e derived from indene, benzofuran, benzothiophene, acenaphthylene, chromone, coumarin, norbornadiene, or derivatives thereof. Examples of the monomer that gives the repeating unit e include, but are not limited to, those shown below. [Chemical Formula]

[0243] The base polymer may further contain a repeating unit f derived from indane, vinylpyridine, or vinylcarbazole.

[0244] In the polymer of the present invention, the content ratios of the repeating units a1, a2, b1, b2, c1 to c4, d, e, and f are preferably 0 < a1 ≤ 0.8, 0 ≤ a2 ≤ 0.8, 0 ≤ b1 ≤ 0.6, 0 ≤ b2 ≤ 0.6, 0 ≤ c1 ≤ 0.4, 0 ≤ c2 ≤ 0.4, 0 ≤ c3 ≤ 0.4, 0 ≤ c4 ≤ 0.4, 0 ≤ d ≤ 0.5, 0 ≤ e ≤ 0.3, and 0 ≤ f ≤ 0.3, and more preferably 0 < a1 ≤ 0.7, 0 ≤ a2 ≤ 0.7, 0 ≤ b1 ≤ 0.5, 0 ≤ b2 ≤ 0.5, 0 ≤ c1 ≤ 0.3, 0 ≤ c2 ≤ 0.3, 0 ≤ c3 ≤ 0.3, 0 ≤ c4 ≤ 0.3, 0 ≤ d ≤ 0.3, 0 ≤ e ≤ 0.3, and 0 ≤ f ≤ 0.3.

[0245] The weight average molecular weight (Mw) of the polymer is preferably from 1,000 to 500,000, more preferably from 3,000 to 100,000. If Mw is within this range, sufficient etching resistance can be obtained, and there is no risk of deterioration of resolution due to the inability to ensure the difference in dissolution rate before and after exposure. In the present invention, Mw is a polystyrene equivalent measurement value by gel permeation chromatography (GPC) using THF or N,N-dimethylformamide (DMF) as a solvent.

[0246] Furthermore, the molecular weight distribution (Mw / Mn) of the polymer tends to have a greater influence as the pattern rule becomes finer. Therefore, in order to obtain a resist composition suitable for fine pattern dimensions, it is preferable that the Mw / Mn is narrowly dispersed between 1.0 and 2.0. Within this range, there are few low molecular weight or high molecular weight polymers, and there is no risk of foreign matter being observed on the pattern or deterioration of the pattern shape after exposure.

[0247] To synthesize the aforementioned polymer, for example, the monomer that provides the repeating units described above may be heated in an organic solvent with a radical polymerization initiator added, and polymerization may be carried out.

[0248] Examples of organic solvents used during polymerization include toluene, benzene, THF, diethyl ether, dioxane, cyclohexane, cyclopentane, methyl ethyl ketone (MEK), propylene glycol monomethyl ether acetate (PGMEA), and γ-butyrolactone (GBL). Examples of polymerization initiators include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl-2,2-azobis(2-methylpropionate), 1,1'-azobis(1-acetoxy-1-phenylethane), benzoyl peroxide, and lauroyl peroxide. The amount of these initiators added is preferably 0.01 to 25 mol% of the total amount of monomers to be polymerized. The reaction temperature is preferably 50 to 150°C, and more preferably 60 to 100°C. The reaction time is preferably 2 to 24 hours, and more preferably 2 to 12 hours from the viewpoint of production efficiency.

[0249] The polymerization initiator may be added to the monomer solution and supplied to the reaction vessel, or an initiator solution may be prepared separately from the monomer solution and each supplied to the reaction vessel independently. Since the polymerization reaction may proceed and a superpolymer may be formed by radicals generated from the initiator during the waiting time, it is preferable from a quality control viewpoint to prepare the monomer solution and the initiator solution independently and add them dropwise. The acid-unstable group may be used as is, introduced into the monomer, or it may be protected or partially protected after polymerization. In addition, known chain transfer agents such as dodecyl mercaptan or 2-mercaptoethanol may be used in combination to adjust the molecular weight. In this case, the amount of these chain transfer agents added is preferably 0.01 to 20 mol% of the total amount of monomers to be polymerized.

[0250] In the case of monomers containing hydroxyl groups, the hydroxyl groups may be substituted with acetal groups that are easily deprotected by acids such as ethoxyethoxy groups during polymerization, and then deprotected with a weak acid and water after polymerization. Alternatively, they may be substituted with acetyl groups, formyl groups, pivaloyl groups, etc., and then alkaline hydrolysis may be performed after polymerization.

[0251] When copolymerizing hydroxystyrene or hydroxyvinylnaphthalene, hydroxystyrene or hydroxyvinylnaphthalene may be polymerized by heating in an organic solvent with a radical polymerization initiator. Alternatively, acetoxystyrene or acetoxyvinylnaphthalene may be used, and after polymerization, the acetoxy group may be deprotected by alkaline hydrolysis to obtain polyhydroxystyrene or hydroxypolyvinylnaphthalene.

[0252] Ammonia water, triethylamine, etc., can be used as the base during alkaline hydrolysis. The reaction temperature is preferably -20 to 100°C, more preferably 0 to 60°C. The reaction time is preferably 0.2 to 100 hours, more preferably 0.5 to 20 hours.

[0253] The amount of each monomer in the monomer solution can be appropriately set, for example, to achieve a preferred content ratio of the repeating units described above.

[0254] The polymer obtained by the above manufacturing method may be treated as a final product if it is a reaction solution obtained by a polymerization reaction, or as a final product if it is a powder obtained by a purification process such as a reprecipitation method in which the polymerization solution is added to a poor solvent and a powder is obtained. However, from the viewpoint of work efficiency and quality stabilization, it is preferable to treat the polymer solution obtained by dissolving the powder obtained by the purification process in a solvent as the final product.

[0255] Specific examples of solvents used in this process include ketones such as cyclohexanone and methyl-2-n-pentyl ketone, as described in paragraphs

[0144] to

[0145] of Japanese Patent Publication No. 2008-111103; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and 1-ethoxy-2-propanol; 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. Examples include ethers such as ethers; esters such as 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 monotert-butyl ether acetate; lactones such as GBL; alcohols such as diacetone alcohol (DAA); high-boiling point alcoholic solvents such as diethylene glycol, propylene glycol, glycerin, 1,4-butanediol, and 1,3-butanediol; and mixed solvents thereof.

[0256] In the polymer solution, the concentration of the polymer is preferably 0.01 to 30% by mass, and more preferably 0.1 to 20% by mass.

[0257] It is preferable to filter the reaction solution or polymer solution. Filtering removes foreign matter and gel that may cause defects, which is effective in stabilizing quality.

[0258] Examples of filter materials used in the aforementioned filter filtration include fluorocarbon, cellulose, nylon, polyester, and hydrocarbon materials. However, in the filtration process of the resist composition, filters made of fluorocarbon materials such as Teflon (registered trademark), hydrocarbon materials such as polyethylene and polypropylene, or nylon are preferred. The pore size of the filter can be appropriately selected according to the desired level of cleanliness, but is preferably 100 nm or less, and more preferably 20 nm or less. These filters may be used individually or in combination. The filtration method may involve passing the solution through only once, but it is more preferable to circulate the solution and filter it multiple times. The filtration process can be carried out in any order and number of times in the polymer manufacturing process, but it is preferable to filter the reaction solution after the polymerization reaction, the polymer solution, or both.

[0259] (B) The base polymer may be used alone, or two or more types with different composition ratios, Mw and / or Mw / Mn may be used in combination. In addition, (B) the base polymer may also contain hydrogenated ring-opening metathesis polymers, for which those described in Japanese Patent Publication No. 2003-66612 may be used.

[0260] [(C) Organic Solvents] The chemically amplified resist composition of the present invention may contain an organic solvent as component (C). The organic solvent (C) is not particularly limited as long as it is capable of dissolving the components described above and the components described later. Examples of such organic solvents include ketones such as cyclopentanone, cyclohexanone, and methyl-2-n-pentyl ketone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and 1-ethoxy-2-propanol; keto alcohols such as DAA; ethers such as 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 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 monotert-butyl ether acetate; lactones such as GBL; and mixed solvents thereof.

[0261] Among these organic solvents, 1-ethoxy-2-propanol, PGMEA, cyclohexanone, GBL, DAA, and mixtures thereof are preferred, as they exhibit particularly excellent solubility of the base polymer of component (B).

[0262] In the chemically amplified resist composition of the present invention, the content of (C) organic solvent is preferably 200 to 5000 parts by mass, and more preferably 400 to 3500 parts by mass, per 80 parts by mass of (B) base polymer. (C) organic solvent may be used alone or as a mixture of two or more types.

[0263] [(D) Quencher] The chemically amplified resist composition of the present invention may contain a quencher as component (D). In the present invention, a quencher is a material that traps the acid generated from the photoacid generator in the chemically amplified resist composition, thereby preventing its diffusion to unexposed areas and forming a desired pattern.

[0264] (D) Examples of quenchers include onium salts represented by the following formulas (2) or (3). [ka]

[0265] In formula (2), R q1 This is a C1-C40 hydrocarbyl group which may contain a hydrogen atom or a heteroatom, but excludes those in which the hydrogen atom bonded to the α-carbon of the sulfo group is substituted with a fluorine atom or a fluoroalkyl group. In formula (3), R q2 This is a hydrocarbyl group having 1 to 40 carbon atoms, which may contain a hydrogen atom or a heteroatom.

[0266] R q1 Specifically, the C1-C40 hydrocarbyl groups represented by include C1-C40 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; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, and tricyclo[5.2.1.0 2,6Examples include cyclic saturated hydrocarbyl groups having 3 to 40 carbon atoms, such as decyl groups and adamantyl groups; and aryl groups having 6 to 40 carbon atoms, such as phenyl groups, naphthyl groups, and anthracenyl groups. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and some of the -CH2- groups of the hydrocarbyl group may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms. As a result, the group may contain hydroxyl groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, cyano groups, carbonyl groups, ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic acid anhydrides (-C(=O)-OC(=O)-), haloalkyl groups, etc.

[0267] R q2 Specifically, the hydrocarbyl group represented by R q1 In addition to the substituents exemplified as specific examples, other examples include fluorinated saturated hydrocarbyl groups such as trifluoromethyl and trifluoroethyl groups, and fluorinated aryl groups such as pentafluorophenyl and 4-trifluoromethylphenyl groups.

[0268] The anions of the onium salt represented by formula (2) include, but are not limited to, those listed below. [ka]

[0269] [ka]

[0270] [ka]

[0271] The anions of the onium salt represented by formula (3) include, but are not limited to, those listed below. [ka]

[0272] [ka]

[0273] [ka]

[0274] In equations (2) and (3), MQ + This is an onium cation. The onium cation is preferably a sulfonium cation represented by the formula (cation-1) described above, an iodonium cation represented by the formula (cation-2) described above, or an ammonium cation represented by the following formula (cation-3). [ka]

[0275] In formula (cation-3), R ct6 ~R ct9 Each of these is independently a hydrocarbyl group having 1 to 40 carbon atoms, which may contain heteroatoms. Also, R ct6 and R ct7 These may bond with each other to form a ring with the nitrogen atom to which they are bonded. The hydrocarbyl group is R in the description of formulas (cation-1) and (cation-2). ct1 ~R ct5 Examples of hydrocarbyl groups represented by the same formula as those exemplified above include those shown.

[0276] Examples of ammonium cations represented by formula (cation-3) include, but are not limited to, those listed below. [ka]

[0277] Specific examples of onium salts represented by formula (2) or (3) include any combination of the anions and cations mentioned above. These onium salts can be easily prepared by ion exchange reactions using known organic chemical methods. For ion exchange reactions, refer to, for example, Japanese Patent Publication No. 2007-145797.

[0278] The onium salt represented by formula (2) or (3) acts as a quencher in the chemically amplified resist composition of the present invention. This is because each counteranion of the onium salt is a conjugate base of a weak acid. Here, a weak acid means one that exhibits an acidity that cannot deprotect the acid-unstable groups of the acid-unstable group-containing units used in the base polymer. The onium salt represented by formula (2) or (3) functions as a quencher when used in combination with an onium salt type photoacid generator having a conjugate base of a strong acid, such as a sulfonic acid with fluorinated α-position, as a counteranion. That is, when an onium salt that generates a strong acid, such as a sulfonic acid with fluorinated α-position, is mixed with an onium salt that generates a weak acid, such as an unfluorinated sulfonic acid or carboxylic acid, when the strong acid generated from the photoacid generator by high-energy ray irradiation collides with the onium salt having an unreacted weak acid anion, the weak acid is released by salt exchange, and an onium salt having a strong acid anion is produced. In this process, strong acids are replaced by weaker acids with lower catalytic activity, so the acids appear to be deactivated, allowing for control of acid diffusion.

[0279] Furthermore, as the (D) quencher, an onium salt having a sulfonium cation and a phenoxide anion moiety in the same molecule as described in Japanese Patent Publication No. 6848776, an onium salt having a sulfonium cation and a carboxylate anion moiety in the same molecule as described in Japanese Patent Publication No. 6583136 and Japanese Patent Application Publication No. 2020-200311, and an onium salt having an iodonium cation and a carboxylate anion moiety in the same molecule as described in Japanese Patent Publication No. 6274755 can also be used.

[0280] Here, if the photoacid generator that produces a strong acid is an onium salt, as mentioned above, the strong acid produced by high-energy ray irradiation can be exchanged for a weak acid. On the other hand, it is thought that the weak acid produced by high-energy ray irradiation is unlikely to collide with the unreacted onium salt that produces the strong acid and undergo salt exchange. This is due to the phenomenon that onium cations are more likely to form ion pairs with the anions of stronger acids.

[0281] When the chemically amplified resist composition of the present invention contains an onium salt represented by formula (2) or (3) as a quencher (D), its content is preferably 0.1 to 20 parts by mass, and more preferably 0.1 to 10 parts by mass, per 80 parts by mass of the base polymer (B). A quencher of the onium salt type of component (D) within this range is preferable because it provides good resolution and does not significantly reduce sensitivity. The onium salt represented by formula (2) or (3) can be used alone or in combination of two or more.

[0282] The chemically amplified resist composition of the present invention may contain a nitrogen-containing compound as the (D) quencher. Examples of the nitrogen-containing compound of component (D) include primary, secondary, or tertiary amine compounds described in paragraphs

[0146] to

[0164] of Japanese Patent Application Publication No. 2008-111103, particularly amine compounds having a hydroxyl group, ether bond, ester bond, lactone ring, cyano group, or sulfonic acid ester bond. Also, examples include compounds in which a primary or secondary amine is protected with a carbamate group, such as the compound described in Japanese Patent Application Publication No. 3790649.

[0283] Furthermore, a sulfonium sulfonate salt having a nitrogen-containing substituent may be used as the nitrogen-containing compound. Such a compound functions as a quencher in the unexposed area and loses its quenching ability in the exposed area through neutralization with its own generated acid, functioning as a so-called photodecayable base. By using a photodecayable base, the contrast between the exposed and unexposed areas can be further enhanced. For example, Japanese Patent Publication No. 2009-109595 and Japanese Patent Publication No. 2012-46501 can be referenced as examples of photodecayable bases.

[0284] When the chemically amplified resist composition of the present invention contains a nitrogen-containing compound as (D) quencher, the content is preferably 0.001 to 12 parts by mass, and more preferably 0.01 to 8 parts by mass, per 80 parts by mass of the (B) base polymer. The nitrogen-containing compound may be used alone or in combination of two or more.

[0285] [(E) Other photoacid generators] The chemically amplified resist composition of the present invention may contain a photoacid generator other than component (A) as component (E) (hereinafter also referred to as "other photoacid generator"). The other photoacid generator is not particularly limited as long as it is a compound that generates acid upon irradiation with high-energy rays. Suitable other photoacid generators include those represented by the following formulas (4) or (5). [ka]

[0286] In formula (4), R 101 ~R 105 Each of these is independently a hydrocarbyl group having 1 to 20 carbon atoms, which may contain heteroatoms. Also, R 101 , R 102 and R 103 Any two of these may bond with each other to form a ring with the sulfur atom to which they are bonded. The hydrocarbyl group is R as described in the explanation of formulas (cation-1) and (cation-2). ct1 ~R ct5 Examples of hydrocarbyl groups represented by the same formula as those exemplified above include those shown.

[0287] Specific examples of cations of sulfonium salts represented by formula (4) include those similar to those exemplified as sulfonium cations represented by formula (cation-1). Specific examples of cations of iodonium salts represented by formula (5) include those similar to those exemplified as iodonium cations represented by formula (cation-2).

[0288] In equations (4) and (5), Xa - This is an anion of a strong acid. Examples of the aforementioned anions of strong acids include those represented by any of the formulas (c1-1) to (c1-5).

[0289] Furthermore, as an additional photoacid generator for component (E), one represented by the following formula (6) is also preferred. [ka]

[0290] In formula (6), R 201 and R 202 Each of these is independently a hydrocarbyl group having 1 to 30 carbon atoms, which may contain heteroatoms. 203 This is a hydrocarbylene group having 1 to 30 carbon atoms, which may contain heteroatoms. Also, R 201 , R 202 and R 203 Any two of these may bond with each other to form a ring with the sulfur atom to which they are bonded.

[0291] R 201 and R 202 The C1-C30 hydrocarbyl group represented by can be saturated or unsaturated, and can be linear, branched, or cyclic. Specific examples include C1-C30 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, tert-pentyl, n-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, oxanorbornyl, and tricyclo[5.2.1.0 2,6Examples include cyclic saturated hydrocarbyl groups having 3 to 30 carbon atoms, such as decyl groups and adamantyl groups; aryl groups having 6 to 30 carbon atoms, such as phenyl groups, methylphenyl groups, ethylphenyl groups, n-propylphenyl groups, isopropylphenyl groups, n-butylphenyl groups, isobutylphenyl groups, sec-butylphenyl groups, tert-butylphenyl groups, naphthyl groups, methylnaphthyl groups, ethylnaphthyl groups, n-propylnaphthyl groups, isopropylnaphthyl groups, n-butylnaphthyl groups, isobutylnaphthyl groups, sec-butylnaphthyl groups, tert-butylnaphthyl groups, anthracenyl groups, and groups obtained by combining these. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing heteroatoms such as oxygen, sulfur, nitrogen, or halogen atoms, and some of the -CH2- groups of the hydrocarbyl group may be substituted with a group containing heteroatoms such as oxygen, sulfur, or nitrogen atoms, and as a result, the material may contain hydroxyl groups, cyano groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, carbonyl groups, ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic acid anhydrides (-C(=O)-OC(=O)-), haloalkyl groups, etc.

[0292] R 203The hydrocarbylene group, represented by , having 1 to 30 carbon atoms, may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include alkane diyl groups with 1 to 30 carbon atoms, such as methanediyl group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,3-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group, undecane-1,11-diyl group, dodecane-1,12-diyl group, tridecane-1,13-diyl group, tetradecane-1,14-diyl group, pentadecane-1,15-diyl group, hexadecane-1,16-diyl group, heptadecane-1,17-diyl group, etc.; cyclop Examples include cyclic saturated hydrocarbylene groups having 3 to 30 carbon atoms, such as tananediyl group, cyclohexanediyl group, norbornanediyl group, and adamantanediyl group; and arylene groups such as phenylene group, methylphenylene group, ethylphenylene group, n-propylphenylene group, isopropylphenylene group, n-butylphenylene group, isobutylphenylene group, sec-butylphenylene group, tert-butylphenylene group, naphthylene group, methylnaphthylene group, ethylnaphthylene group, n-propylnaphthylene group, isopropylnaphthylene group, n-butylnaphthylene group, isobutylnaphthylene group, sec-butylnaphthylene group, and tert-butylnaphthylene group. Furthermore, some or all of the hydrogen atoms of the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom, nitrogen atom, or halogen atom, and some of the -CH2- of the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom, or nitrogen atom, and as a result, it may contain a hydroxyl group, a cyano group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a carbonyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc. The heteroatom is preferably an oxygen atom.

[0293] In formula (6), L AThis is a 1-20 carbon atom hydrocarbylene group which may contain single bonds, ether bonds, or heteroatoms. The hydrocarbylene group may be saturated or unsaturated, and may be linear, branched, or cyclic. A specific example is R 203 Examples of hydrocarbylene groups represented by the same formula as those exemplified above include the same groups as those shown.

[0294] In formula (6), X a , X b , X c and X d Each of these is independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group. However, X a , X b , X c and X d At least one of these is a fluorine atom or a trifluoromethyl group.

[0295] The photoacid generator represented by formula (6) is preferably the one represented by the following formula (6'). [ka]

[0296] In formula (6'), L A The same as above. X e R is a hydrogen atom or a trifluoromethyl group, preferably a trifluoromethyl group. 301 , R 302 and R 303 Each of these is a hydrocarbyl group having 1 to 20 carbon atoms, which may each contain a hydrogen atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. A specific example is R in formula (c1-1-1). fa1 Examples of hydrocarbyl groups represented by the same designation as those exemplified are shown. 1 and m 2 Each of these is an integer between 0 and 5, and m 3 This is an integer between 0 and 4.

[0297] Examples of photoacid generators represented by formula (6) include those similar to those exemplified as photoacid generators represented by formula (2) in Japanese Patent Publication No. 2017-26980.

[0298] Among the other photoacid generators mentioned above, those containing anions represented by formula (c1-1-1) or (c1-4) are particularly preferred because they exhibit low acid diffusion and excellent solubility in solvents. Furthermore, those represented by formula (6') are particularly preferred because they exhibit extremely low acid diffusion.

[0299] If the chemically amplified resist composition of the present invention contains (E) other photoacid generators, the content thereof is preferably 0.1 to 40 parts by mass, and more preferably 0.5 to 20 parts by mass, per 80 parts by mass of the (B) base polymer. When the amount of photoacid generator added to component (E) is within the above range, the resolution is good and there is no risk of foreign matter problems occurring after development or peeling of the resist film, so it is preferable. (E) Other photoacid generators may be used alone or in combination of two or more types.

[0300] [(F) Surfactants] The chemically amplified resist composition of the present invention may further contain a surfactant as component (F). Preferably, the surfactant (F) is a surfactant that is insoluble or sparingly soluble in water and soluble in an alkaline developer, or a surfactant that is insoluble or sparingly soluble in both water and an alkaline developer. Examples of such surfactants can be found in Japanese Patent Publication No. 2010-215608 and Japanese Patent Publication No. 2011-16746.

[0301] As surfactants that are insoluble or poorly soluble in water and alkaline developer, among the surfactants described in the above publication, FC-4430 (manufactured by 3M), Surflon® S-381 (manufactured by AGC Seimi Chemical Co., Ltd.), Orfin® E1004 (manufactured by Nisshin Chemical Industry Co., Ltd.), KH-20, KH-30 (manufactured by AGC Seimi Chemical Co., Ltd.), and oxetane ring-opening polymers represented by the following formula (surf-1) are preferred. [ka]

[0302] Here, R, Rf, A, B, C, m, and n apply only to formula (surf-1), notwithstanding the preceding description. R is a divalent to tetravalent aliphatic group having 2 to 5 carbon atoms. Examples of such aliphatic groups include the divalent ethylene group, 1,4-butylene group, 1,2-propylene group, 2,2-dimethyl-1,3-propylene group, and 1,5-pentylene group, while examples of trivalent or tetravalent aliphatic groups are listed below. [ka] (In the formula, the dashed lines represent bonds, which are substructures derived from glycerol, trimethylolethane, trimethylolpropane, and pentaerythritol, respectively.)

[0303] Among these, the 1,4-butylene group and the 2,2-dimethyl-1,3-propylene group are preferred.

[0304] Rf is a trifluoromethyl group or a pentafluoroethyl group, preferably a trifluoromethyl group. m is an integer from 0 to 3, n is an integer from 1 to 4, and the sum of n and m is the valence of R, an integer from 2 to 4. A is 1. B is an integer from 2 to 25, preferably an integer from 4 to 20. C is an integer from 0 to 10, preferably 0 or 1. Furthermore, the order of each constituent unit in formula (surf-1) is not specified, and they may be bonded in a block-like manner or randomly. For details on the production of partially fluorinated oxetane ring-opening polymer surfactants, please refer to U.S. Patent No. 5,650,483, etc.

[0305] Surfactants that are insoluble or sparingly soluble in water and soluble in alkaline developers have the function of reducing water penetration and leaching by orienting themselves on the surface of the resist film when a resist protective film is not used in ArF immersion lithography. Therefore, they are useful in suppressing the elution of water-soluble components from the resist film and reducing damage to the exposure equipment. Furthermore, they are useful because they become solubilized during alkaline aqueous solution development after exposure or post-exposure bake (PEB) and are less likely to become foreign substances that cause defects. Such surfactants are insoluble or sparingly soluble in water and soluble in alkaline developers, and are polymer-type surfactants, also called hydrophobic resins, with those that have particularly high water repellency and improve water lubricity being preferred.

[0306] Examples of such polymer-type surfactants include those containing at least one repeating unit selected from any of the following formulas (7A) to (7E). [ka]

[0307] In formulas (7A) to (7E), R B is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1 R is -CH2-, -CH2CH2-, -O-, or two separated -H atoms. s1 Each of these is independently a hydrogen atom or a hydrocarbyl group having 1 to 10 carbon atoms. s2 R is a single bond or a linear or branched hydrocarbylene group having 1 to 5 carbon atoms. s3 Each of these is independently a hydrogen atom, a C1-C15 hydrocarbyl group or a fluorinated hydrocarbyl group, or an acid-unstable group. s3 If the group is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be interposed between the carbon-carbon bonds. s4 R is a (u+1) valent hydrocarbon group or fluorinated hydrocarbon group having 1 to 20 carbon atoms. u is an integer from 1 to 3. s5 These are, independently, hydrogen atoms, or -C(=O)-ORsa It is a group represented by R. sa This is a fluorinated hydrocarbyl group having 1 to 20 carbon atoms. s6 This is a hydrocarbyl group having 1 to 15 carbon atoms or a fluorinated hydrocarbyl group, and an ether bond or a carbonyl group may be interposed between the carbon-carbon bonds.

[0308] R s1 The C1-C10 hydrocarbyl group represented by is preferably a saturated hydrocarbyl group and may be linear, branched, or cyclic. Specific examples include C1-C10 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl groups; and C3-C10 cyclic saturated hydrocarbyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, adamantyl, and norbornyl groups. Of these, those with C1-C6 are preferred.

[0309] R s2 The hydrocarbylene group represented by is preferably a saturated hydrocarbylene group and may be linear, branched, or cyclic. Specific examples include methylene, ethylene, propylene, butylene, and pentylene groups.

[0310] R s3 or R s6 The hydrocarbyl group represented by may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include saturated hydrocarbyl groups, alkenyl groups, alkynyl groups, and other aliphatic unsaturated hydrocarbyl groups, but saturated hydrocarbyl groups are preferred. The saturated hydrocarbyl group is R s1 In addition to the examples given as hydrocarbyl groups represented by , other examples include undecyl groups, dodecyl groups, tridecyl groups, tetradecyl groups, pentadecyl groups, etc. s3 or R s6Examples of fluorinated hydrocarbyl groups represented by the above-mentioned hydrocarbyl group include groups in which some or all of the hydrogen atoms bonded to the carbon atoms are replaced with fluorine atoms. As mentioned above, ether bonds or carbonyl groups may be interposed between these carbon-carbon bonds.

[0311] R s3 Examples of acid-unstable groups represented by the formulas (AL-3) to (AL-5) mentioned above include trialkylsilyl groups in which each alkyl group has 1 to 6 carbon atoms, and alkyl groups containing an oxo group with 4 to 20 carbon atoms.

[0312] R s4 The (u+1) valent hydrocarbon group or fluorinated hydrocarbon group represented by may be linear, branched, or cyclic, and specific examples include groups obtained by further removing u hydrogen atoms from the aforementioned hydrocarbyl group or fluorinated hydrocarbyl group.

[0313] R sa The fluorinated hydrocarbyl group represented by is preferably saturated and may be linear, branched, or cyclic. Specific examples include those in which some or all of the hydrogen atoms of the hydrocarbyl group are substituted with fluorine atoms, and specific examples of such include trifluoromethyl group, 2,2,2-trifluoroethyl group, 3,3,3-trifluoro-1-propyl group, 3,3,3-trifluoro-2-propyl group, 2,2,3,3-tetrafluoropropyl group, 1,1,1,3,3,3-hexafluoroisopropyl group, 2,2,3,3,4,4,4-heptafluorobutyl group, 2,2,3,3,4,4,5,5-octafluoropentyl group, 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl group, 2-(perfluorobutyl)ethyl group, 2-(perfluorohexyl)ethyl group, 2-(perfluorooctyl)ethyl group, 2-(perfluorodecyl)ethyl group, etc.

[0314] The repeating units represented by any of the formulas (7A) to (7E) include, but are not limited to, the following. Note that in the following formulas, R B This is the same as described above. [ka]

[0315] [ka]

[0316] [ka]

[0317] [ka]

[0318] [ka]

[0319] The polymer-type surfactant may further contain other repeating units other than those represented by formulas (7A) to (7E). Examples of other repeating units include those obtained from methacrylic acid and α-trifluoromethylacrylic acid derivatives. The content of the repeating units represented by formulas (7A) to (7E) in the polymer-type surfactant is preferably 20 mol% or more, more preferably 60 mol% or more, and even more preferably 100 mol% of the total repeating units.

[0320] The Mw of the polymer-type surfactant is preferably 1,000 to 500,000, and more preferably 3,000 to 100,000. The Mw / Mn ratio is preferably 1.0 to 2.0, and more preferably 1.0 to 1.6.

[0321] A method for synthesizing the polymer-type surfactant involves polymerizing a monomer containing unsaturated bonds that provide repeating units represented by formulas (7A) to (7E), and optionally other repeating units, by heating it in an organic solvent with a radical initiator. Examples of organic solvents used during polymerization include toluene, benzene, THF, diethyl ether, and dioxane. Examples of polymerization initiators include AIBN, 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl-2,2-azobis(2-methylpropionate), benzoyl peroxide, and lauroyl peroxide. The reaction temperature is preferably 50 to 100°C. The reaction time is preferably 4 to 24 hours. The acid-unstable group may be used as is after being introduced into the monomer, or it may be protected or partially protected after polymerization.

[0322] When synthesizing the polymer-type surfactant, known chain transfer agents such as dodecyl mercaptan or 2-mercaptoethanol may be used to adjust the molecular weight. In that case, the amount of these chain transfer agents added is preferably 0.01 to 10 mol% relative to the total number of moles of monomers to be polymerized.

[0323] When the chemically amplified resist composition of the present invention contains a surfactant (F), its content is preferably 0.1 to 50 parts by mass, and more preferably 0.5 to 10 parts by mass, per 80 parts by mass of the base polymer (B). If the content of the surfactant (F) is 0.1 parts by mass or more, the receding contact angle between the resist film surface and water is sufficiently improved, and if it is 50 parts by mass or less, the dissolution rate of the resist film surface in the developer is small, and the height of the formed fine pattern is sufficiently maintained. The surfactant (F) may be used alone or in combination of two or more types.

[0324] [(G) Other ingredients] The chemically amplified resist composition of the present invention may also contain (G) other components such as a compound that decomposes with acid to generate acid (acid-proliferating compound), an organic acid derivative, a fluorine-substituted alcohol, and a compound with an Mw of 3,000 or less whose solubility in the developer changes due to the action of acid (dissolution inhibitor). As the acid-proliferating compound, one can refer to the compounds described in Japanese Patent Publication No. 2009-269953 or Japanese Patent Publication No. 2010-215608. When the acid-proliferating compound is included, its content is preferably 0 to 5 parts by mass, and more preferably 0 to 3 parts by mass, per 80 parts by mass of the (B) base polymer. If the content is too high, it becomes difficult to control acid diffusion, which may lead to deterioration of resolution and pattern shape. As the organic acid derivative, fluorine-substituted alcohol and dissolution inhibitor, one can refer to the compounds described in Japanese Patent Publication No. 2009-269953 or Japanese Patent Publication No. 2010-215608.

[0325] [Pattern formation method] The pattern formation method of the present invention includes the steps of forming a resist film on a substrate using the chemically amplified resist composition described above, exposing the resist film with high-energy rays, and developing the exposed resist film using a developer.

[0326] As the substrate, for example, substrates for integrated circuit manufacturing (Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic anti-reflective coatings, etc.) or substrates for mask circuit manufacturing (Cr, CrO, CrON, MoSi2, SiO2, etc.) can be used.

[0327] The resist film can be formed by, for example, applying the chemically amplified resist composition onto a substrate using a method such as spin coating to a film thickness of preferably 0.05 to 2 μm, and then pre-baking it on a hot plate at preferably 60 to 150°C for 1 to 10 minutes, more preferably 80 to 140°C for 1 to 5 minutes.

[0328] High-energy beams used for exposure of resist films include KrF excimer laser light, ArF excimer laser light, EB, and EUV. When using KrF excimer laser light, ArF excimer laser light, or EUV, exposure is performed using a mask to form the desired pattern, with an exposure dose of preferably 1 to 200 mJ / cm². 2 More preferably 10-100 mJ / cm² 2 This can be done by irradiating in such a manner. When using EB, the exposure amount is preferably 1 to 300 μC / cm², either using a mask to form the desired pattern or directly. 2 More preferably 10-200 μC / cm 2 Irradiate in such a way that it results in the following.

[0329] In addition to conventional exposure methods, immersion methods can also be used, in which a liquid with a refractive index of 1.0 or higher is interposed between the resist film and the projection lens. In this case, a protective film insoluble in water can also be used.

[0330] The aforementioned water-insoluble protective film is used to prevent leaching from the resist film and to improve the water-repellent properties of the film surface, and there are two main types. One is an organic solvent-removable type that requires removal before alkaline aqueous solution development using an organic solvent that does not dissolve the resist film, and the other is an alkaline aqueous solution-soluble type that is soluble in alkaline developer and removes the protective film along with the soluble parts of the resist film. The latter is particularly preferably based on a polymer having a 1,1,1,3,3,3-hexafluoro-2-propanol residue that is insoluble in water and soluble in alkaline developer, and dissolved in an alcohol-based solvent having 4 or more carbon atoms, an ether-based solvent having 8 to 12 carbon atoms, or a mixture thereof. Alternatively, the aforementioned water-insoluble and alkaline developer-soluble surfactant can be dissolved in an alcohol-based solvent having 4 or more carbon atoms, an ether-based solvent having 8 to 12 carbon atoms, or a mixture thereof.

[0331] PEB may be performed after exposure. PEB can be performed, for example, by heating on a hot plate, preferably at 60-150°C for 1-5 minutes, more preferably at 80-140°C for 1-3 minutes.

[0332] Development is carried out using a developer solution, preferably an alkaline aqueous solution such as tetramethylammonium hydroxide (TMAH) in an amount of 0.1 to 5% by mass, more preferably 2 to 3% by mass, and by conventional methods such as the dip method, puddle method, or spray method for preferably 0.1 to 3 minutes, more preferably 0.5 to 2 minutes, which dissolves the exposed areas and forms the desired pattern on the substrate.

[0333] Furthermore, after the resist film is formed, a rinse with pure water may be performed to extract acid generators or other substances from the film surface, or to wash away particles. Alternatively, a rinse may be performed after exposure to remove any water remaining on the film.

[0334] Furthermore, patterns may be formed using a double patterning method. Examples of double patterning methods include the trench method, in which a 1:3 trench pattern base is processed with the first exposure and etching, and then a 1:3 trench pattern is formed by a second exposure with a shifted position to form a 1:1 pattern; and the line method, in which a first base for a 1:3 isolated pattern is processed with the first exposure and etching, and then a second exposure with a shifted position to process a second base formed beneath the first base for a 1:3 isolated pattern to form a 1:1 pattern with half the pitch.

[0335] In the pattern formation method of the present invention, instead of the alkaline aqueous solution used as the developer, a negative tone development method may be used in which an organic solvent is used to dissolve the unexposed areas.

[0336] This organic solvent development uses the following as a developer: 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 crotate, ethyl crotate, propyl acetate, methyl propyl formate, butyl formate, isobutyl formate, pentyl formate, methyl valerate, methyl pentenoate, methyl crotate, ethyl crotate, propyl propyl acetate, methyl propyl formate, methyl pentenoate, methyl crotate, ethyl crotate, propyl propyl acetate, methyl propyl formate, methyl pentenoate, methyl crotate, methyl crotate, methyl propyl acetate, methyl propyl formatepropyl acetate, methyl propyl formate, methyl propyl acetate, methyl pentenoate, methyl crotate, methyl propyl acetate, methyl propyl acetate, methyl pentenoate, methyl crotate, methyl propyl acetate, methyl propyl acetate, methyl pentenoate, methyl methyl crotate, methyl propyl acetate, methyl propyl acetate, methyl pentenoate, methyl propyl acetate, methyl propyl acetate, methyl pentenoate, methyl methyl crotate, methyl Methyl ropionate, 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, ethyl phenyl acetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, 2-phenylethyl acetate, etc. can be used. These organic solvents may be used individually or in mixtures of two or more. [Examples]

[0337] The present invention will be specifically described below with reference to synthesis examples, examples, and comparative examples, but the present invention is not limited to the following examples. The apparatus used is as follows. • MALDI TOF-MS: S3000 manufactured by JEOL Ltd.

[0338] [1] Synthesis of onium salts [Example 1-1] Synthesis of onium salt PAG-1 [ka]

[0339] (1) Synthesis of intermediate In-1 Under a nitrogen atmosphere, sodium hydride (55% by mass purity, 4.8 g) was suspended in THF (60 mL), and a solution consisting of 1-isopropylcyclopentanol (14.1 g) and THF (15 mL) was added dropwise. After the dropwise addition, the mixture was heated under reflux for 4 hours to prepare the metal alkoxide. Subsequently, starting material SM-1 (24.7 g) was added dropwise, and the mixture was heated under reflux and aged for 18 hours. The reaction mixture was cooled in an ice bath, and the reaction was stopped with water (100 mL). The target product was extracted with a mixed solvent of toluene (100 mL) and hexane (100 mL), and after a normal aqueous work-up, the solvent was removed by distillation, and the mixture was purified by silica gel chromatography to obtain 28.8 g of intermediate In-1 as a colorless oil (yield 81%).

[0340] (2) Synthesis of intermediate In-2 Under a nitrogen atmosphere, intermediate In-1 (28.8 g) was placed in a reaction vessel in a solution consisting of 25% by mass sodium hydroxide aqueous solution (38.9 g) and water (100 mL), and the mixture was aged at 100°C in the reaction vessel for 24 hours. After aging, the reaction mixture was cooled, and the reaction was stopped by adding 20% ​​by mass hydrochloric acid (55 g) dropwise. The mixture was extracted with ethyl acetate (150 mL), subjected to a normal aqueous work-up, and after removing the solvent by distillation, hexane was added and recrystallization was performed to obtain 21.8 g of intermediate In-2 as white crystals (yield 72%).

[0341] (3) Synthesis of intermediate In-3 Under a nitrogen atmosphere, intermediate In-2 (18.0 g), starting material SM-2 (19.0 g), DMAP (0.6 g), and methylene chloride (60 g) were added to the reaction vessel and cooled in an ice bath. While maintaining the temperature inside the reaction vessel below 20°C, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (11.3 g) was added in powder form. After addition, the temperature was raised to room temperature and aged for 12 hours. After aging, water was added to stop the reaction, and a normal aqueous work-up was performed. After removing the solvent by distillation, diisopropyl ether was added and recrystallization was performed to obtain 33.2 g of intermediate In-3 as white crystals (yield 94%).

[0342] (4) Synthesis of onium salt PAG-1 Under a nitrogen atmosphere, intermediate In-3 (14.7g), starting material SM-3 (8.2g), methylene chloride (40g), and water (30g) were added to a reaction vessel and stirred for 30 minutes. The organic layer was then separated, washed with water, and concentrated under reduced pressure. Diisopropyl ether was added to the concentrate and recrystallized to obtain 15.6g of the target product PAG-1 as white crystals (yield 92%).

[0343] The TOF-MS results for PAG-1 are shown below. MALDI TOF-MS: POSITIVE M + 261(C 18 H 13 S + equivalent) NEGATIVE M - 585(C 18 H 19 F5IO6S - equivalent)

[0344] [Examples 1-2 to 1-10] Synthesis of onium salts PAG-2 to PAG-10 Using corresponding raw materials and known organic synthesis reactions, onium salts PAG-2 to PAG-10, represented by the following formulas, were synthesized. [ka]

[0345] [ka]

[0346] [2] Synthesis of base polymers [Synthesis Example] Synthesis of base polymers (P-1 to P-6) Each monomer was combined and copolymerized in MEK, a solvent. The reaction solution was then added to hexane, and the precipitated solid was washed with hexane, isolated, and dried to obtain base polymers (P-1 to P-6) with the following compositions. The compositions of the obtained base polymers are: 1Mw and Mw / Mn were confirmed by H-NMR using GPC (solvent: THF, standard: polystyrene). [ka]

[0347] [3] Preparation of chemically amplified resist compositions [Examples 2-1 to 2-36, Comparative Examples 1-1 to 1-34] Chemically amplified resist compositions (R-1 to R-36 and CR-1 to CR-34) were prepared by dissolving the onium salts (PAG-1 to PAG-10), comparative photoacid generators (PAG-A to PAG-E), other photoacid generators (PAG-X, PAG-Y), base polymers (P-1 to P-6), and quenchers (Q-1 to Q-4) of the present invention in a solvent containing 0.01% by mass of surfactant A (Omnova) in the compositions shown in Tables 1 to 4 below, and filtering the solution through a 0.2 μm Teflon® type filter.

[0348] [Table 1]

[0349] [Table 2]

[0350] [Table 3]

[0351] [Table 4]

[0352] In Tables 1-4, the solvent, other photoacid generators PAG-X, PAG-Y, comparative photoacid generators PAG-A to PAG-E, quenchers Q-1 to Q-4, and surfactant A are as follows. • Solvent: PGMEA (Propylene glycol monomethyl ether acetate) DAA (Diacetone Alcohol)

[0353] Other photoacid generators: PAG-X, PAG-Y [ka]

[0354] • Comparative photoacid generators: PAG-A ~ PAG-E [ka]

[0355] • Quencher: Q-1~Q-4 [ka]

[0356] • Surfactant A: 3-methyl-3-(2,2,2-trifluoroethoxymethyl)oxetane-tetrahydrofuran-2,2-dimethyl-1,3-propanediol copolymer (manufactured by Omnova) [ka] a:(b+b'):(c+c')=1:4~7:0.01~1 (molar ratio) Mw=1500

[0357] [4] EUV lithography evaluation (1) [Examples 3-1 to 3-36, Comparative Examples 2-1 to 2-34] Each chemically amplified resist composition (R-1 to R-36, CR-1 to CR-34) shown in Tables 1 to 4 was spin-coated onto a Si substrate on which a silicon-containing spin-on hard mask SHB-A940 (silicon content 43% by mass) manufactured by Shin-Etsu Chemical Co., Ltd. had been formed to a thickness of 20 nm. A resist film with a thickness of 50 nm was then fabricated by pre-baking at 100°C for 60 seconds using a hot plate. The resist film was then exposed to an LS pattern with a wafer dimension of 18 nm and a pitch of 36 nm using an ASML EUV scanner NXE3300 (NA 0.33, σ 0.9 / 0.6, dipole illumination), with exposure dose and focus varied (exposure dose pitch: 1 mJ / cm²). 2 The process was carried out while adjusting the focus pitch (0.020 μm), and after exposure, PEB was performed for 60 seconds at the temperatures shown in Tables 5 and 6. Then, paddle development was performed for 30 seconds with a 2.38 mass% TMAH aqueous solution, rinsed with a surfactant-containing rinse material, and spin-dried to obtain a positive type pattern. The obtained LS patterns were observed using a Hitachi High-Technologies Corporation length-measuring SEM (CG6300), and sensitivity, EL, LWR, depth of field (DOF), and tilt limit were evaluated according to the method described below. The results are shown in Tables 5 and 6.

[0358] [Sensitivity evaluation] The optimal exposure dose Eop(mJ / cm²) for obtaining an LS pattern with a line width of 18nm and a pitch of 36nm is obtained. 2 The value of ) was calculated and defined as the sensitivity. The smaller this value, the higher the sensitivity.

[0359] [EL rating] The exposure amount formed within ±10% (16.2 to 19.8 nm) of the 18 nm space width in the aforementioned LS pattern was used to calculate the EL (unit: %) using the following formula. A larger value indicates better performance. EL(%) = (|E1-E2| / Eop) × 100 E1: Optimal exposure amount to give an LS pattern with a line width of 16.2 nm and a pitch of 36 nm. E2: Optimal exposure amount to give an LS pattern with a line width of 19.8 nm and a pitch of 36 nm. Eop: Optimal exposure amount to give an LS pattern with a line width of 18nm and a pitch of 36nm.

[0360] [LWR rating] The LS pattern obtained by irradiating with Eop was measured at 10 points along the longitudinal direction of the line, and the LWR was calculated as three times the standard deviation (σ) (3σ) from these results. The smaller this value, the less roughness and the more uniform the line width pattern obtained.

[0361] [DOF rating] To evaluate the depth of focus, the focus range formed within ±10% of the 18nm dimension (16.2 to 19.8nm) in the aforementioned LS pattern was determined. A larger value indicates a wider depth of focus.

[0362] [Evaluation of the limit of line pattern collapse] The line dimensions for each exposure amount at the optimal focus of the aforementioned LS pattern were measured at 10 points along the longitudinal direction. The thinnest line dimension obtained without collapse was defined as the collapse limit dimension. The smaller this value, the better the collapse limit.

[0363] [Table 5]

[0364] [Table 6]

[0365] The results shown in Tables 5 and 6 indicate that the chemically amplified resist composition containing the onium salt photoacid generator of the present invention exhibits good sensitivity and excellent EL, LWR, and DOF. Furthermore, it was confirmed that the tilt limit value is small and that the pattern is resistant to tilting even in the formation of fine patterns. Therefore, the chemically amplified resist composition of the present invention is suitable as a material for EUV lithography.

[0366] [5] EUV Lithography Evaluation (2) [Examples 4-1 to 4-36, Comparative Examples 3-1 to 3-34] Each chemically amplified resist composition (R-1 to R-36, CR-1 to CR-34) shown in Tables 1 to 4 was spin-coated onto a Si substrate on which a silicon-containing spin-on hard mask SHB-A940 (silicon content 43% by mass) manufactured by Shin-Etsu Chemical Co., Ltd. had been formed to a thickness of 20 nm. The resist film was then pre-baked at 105°C for 60 seconds using a hot plate to produce a resist film with a thickness of 50 nm. The resist film was exposed using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9 / 0.6, quadruple pole illumination, wafer-mounted dimensions of 46 nm pitch, +20% bias hole pattern mask). PEB was performed using a hot plate at the temperatures listed in Tables 7 and 8 for 60 seconds, and development was performed with a 2.38% by mass TMAH aqueous solution for 30 seconds to form a hole pattern with dimensions of 23 nm. Using a Hitachi High-Technologies Corporation length-measuring SEM (CG6300), the exposure amount when a hole dimension of 23 nm was formed was measured and defined as the sensitivity. The dimensions of 50 holes at that time were also measured, and the dimensional variation (CDU) was defined as three times the standard deviation (σ) calculated from the results (3σ). The results are shown in Tables 7 and 8.

[0367] [Table 7]

[0368] [Table 8]

[0369] The results shown in Tables 7 and 8 confirm that the chemically amplified resist composition containing the photoacid generator made of onium salt according to the present invention exhibits good sensitivity and excellent CDU.

Claims

1. The onium salt represented by the following formula (1B). 【Chemistry 1】 [In the formula, n1 is 0 or 1. n2 is an integer from 1 to 3. n3 is an integer from 1 to 4. n4 is 0. However, when n1 = 0, n2 + n3 + n4 ≤ 5, and when n1 = 1, n2 + n3 + n4 ≤ 7. n5 is an integer from 0 to 4. R AL This is an acid-unstable group represented by the following formula (AL-1) or (AL-2). 【Chemistry 2】 (In the formula, R 2 , R 3 and R 4 Each of these is independently a C1-C12 hydrocarbyl group, and if the hydrocarbyl group includes an aromatic ring, some or all of the hydrogen atoms of the aromatic ring may be substituted with a halogen atom, a cyano group, a nitro group, a C1-C4 alkyl group which may contain a halogen atom, or a C1-C4 alkoxy group which may contain a halogen atom. 2 and R 3 However, they may bond with each other to form a ring with the carbon atoms to which they are bonded. R 5 and R 6 are each independently a hydrogen atom or a hydrocarbyl group having 1 to 10 carbon atoms. R 7 is a cyclic saturated hydrocarbyl group having 3 to 20 carbon atoms. L C It is either -O- or -S-. m1 is either 0 or 1. m2 is either 0 or 1. * represents a bond with an adjacent -O-. I and -O-R AL These atoms are bonded to adjacent carbon atoms. R 1 This is a hydrocarbyl group having 1 to 20 carbon atoms, which may contain heteroatoms. L A These are single bonds, ether bonds, or ester bonds. X L is, L A When it is a single bond, it is a single bond, L A When it is an ether bond or an ester bond, the group is represented by one of the following formulas. 【Transformation 3】 (In the formula, * represents L) A and L B (This represents a combination of two elements.) Q 1 and Q 2 Each of these is independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Z + This is an onium cation.

2. Z + The onium salt according to claim 1, wherein the onium cation is represented by the following formula (caten-1) or (caten-2). 【Chemistry 4】 (In the formula, R ct1 ~R ct5 Each of these is independently a hydrocarbyl group having 1 to 30 carbon atoms, which may contain heteroatoms. Also, R ct1 and R ct2 However, they may bond with each other to form a ring with the sulfur atom to which they are bonded.

3. A photoacid generator comprising the onium salt according to claim 1 or 2.

4. A chemically amplified resist composition comprising the photoacid generator described in claim 3.

5. A chemically amplified resist composition according to claim 4, comprising a base polymer containing repeating units represented by the following formula (a1). 【Transformation 5】 (In the formula, R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X 1 This refers to a single bond, a phenylene group, a naphthylene group, or *-C(=O)-O-X 11 - and the phenylene group or naphthylene group may be substituted with a carbon-1 to carbon-10 alkoxy group or halogen atom which may contain a fluorine atom. 11 This is a saturated hydrocarbylene group, phenylene group, or naphthylene group having 1 to 10 carbon atoms, and the saturated hydrocarbylene group may contain a hydroxyl group, an ether bond, an ester bond, or a lactone ring. * represents a bond with a carbon atom of the main chain. AL 1 It is an acid-unstable group.

6. The chemically amplified resist composition according to claim 5, wherein the base polymer further comprises repeating units represented by the following formula (a2). 【Transformation 6】 (In the formula, R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X 2 The bond is either a single bond or *-C(=O)-O-. The asterisk (*) represents a bond with a carbon atom in the main chain. R 11 This is a C1-C20 hydrocarbyl group which may contain a halogen atom, a cyano group, a heteroatom, a C1-C20 hydrocarbyloxy group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyl group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyloxy group which may contain a heteroatom, or a C2-C20 hydrocarbyloxycarbonyl group which may contain a heteroatom. AL 2 It is an acid-unstable group. (a is an integer between 0 and 4.)

7. The chemically amplified resist composition according to claim 5, wherein the base polymer comprises repeating units represented by the following formula (b1) or (b2). 【Transformation 7】 (In the formula, R A These are, independently, a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y 1 The bond is either a single bond or *-C(=O)-O-. The asterisk (*) represents a bond with a carbon atom in the main chain. R 21 This is a group having 1 to 20 carbon atoms that includes a hydrogen atom or at least one structure selected from a hydroxyl group other than a phenolic hydroxyl group, a cyano group, a carbonyl group, a carboxyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, and a carboxylic acid anhydride (-C(=O)-O-C(=O)-). R 22 This refers to a C1-C20 hydrocarbyl group which may contain a halogen atom, a hydroxyl group, a nitro group, a heteroatom, a C1-C20 hydrocarbyloxy group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyl group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyloxy group which may contain a heteroatom, or a C2-C20 hydrocarbyloxycarbonyl group which may contain a heteroatom. b is an integer between 1 and 4. c is an integer between 0 and 4. However, 1 ≤ b + c ≤ 5.

8. Furthermore, the chemically amplified resist composition according to claim 5, wherein the base polymer comprises at least one selected from repeating units represented by the following formulas (c1) to (c4). 【Transformation 8】 (In the formula, R A These are, independently, a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Z 1 This is either a single bond or a phenylene group. Z 2 *-C(=O)-O-Z 21 -, *-C(=O)-NH-Z 21 - or * - O - Z 21 - is Z 21 This is a divalent group obtained by combining an aliphatic hydrocarbylene group, a phenylene group, or a combination thereof, having 1 to 6 carbon atoms, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. Z 3 This refers to a single bond, a phenylene group, a naphthylene group, or *-C(=O)-O-Z 31 - is Z 31 This is an aliphatic hydrocarbylene group, a phenylene group, or a naphthylene group having 1 to 10 carbon atoms, and the aliphatic hydrocarbylene group may contain a hydroxyl group, an ether bond, an ester bond, or a lactone ring. Z 4 This is a single bond or *-Z 41 -C(=O)-O-. Z 41 This is a hydrocarbylene group having 1 to 20 carbon atoms, which may contain heteroatoms. Z 5 This includes single bonds, methylene groups, ethylene groups, phenylene groups, fluorinated phenylene groups, trifluoromethyl groups, and *-C(=O)-O-Z. 51 -, *-C(=O)-N(H)-Z 51 - or * - O - Z 51 - is Z 51 This is a phenylene group substituted with an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, or a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. * represents a bond with a carbon atom in the main chain. R 31 and R 32 Each of these is independently a hydrocarbyl group having 1 to 20 carbon atoms, which may contain heteroatoms. Also, R 31 and R 32 These may bond with each other to form a ring with the sulfur atom to which they are bonded. L 1 These are single bonds, ether bonds, ester bonds, carbonyl groups, sulfonic acid ester bonds, carbonate bonds, or carbamate bonds. Rf 1 and Rf 2 Each of these is independently either a fluorine atom or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Rf 3 and Rf 4 Each of these is independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Rf 5 and Rf 6 Each of these is independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. However, all Rf 5 and Rf 6 They cannot simultaneously become hydrogen atoms. M - It is a non-nucleophilic counterion. A + This is an onium cation. d is an integer between 0 and 3.

9. Furthermore, the chemically amplified resist composition according to claim 4, further comprising an organic solvent.

10. Furthermore, the chemically amplified resist composition according to claim 4, further comprising a quencher.

11. Furthermore, the chemically amplified resist composition according to claim 4, comprising a photoacid generator other than the photoacid generator described in claim 6.

12. Furthermore, the chemically amplified resist composition according to claim 4, further comprising a surfactant.

13. A pattern forming method comprising the steps of: forming a resist film on a substrate using the chemically amplified resist composition according to claim 4; exposing the resist film with high-energy rays; and developing the exposed resist film using a developer.

14. The pattern forming method according to claim 13, wherein the high-energy beam is a KrF excimer laser beam, an ArF excimer laser beam, an electron beam, or extreme ultraviolet light with a wavelength of 3 to 15 nm.

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