Onium salt, chemically amplified resist composition, and patterning process

Abstract

To provide an onium salt used in a chemically amplified resist composition that has excellent solvent solubility, high sensitivity, and high contrast in photolithography using high-energy rays, and exhibits superior lithographic properties such as exposure latitude (EL) and LWR, a chemically amplified resist composition comprising the onium salt as a photoacid generator, and a patterning process using the chemically amplified resist composition.SOLUTION: An onium salt represented by formula (1). One of R13 and R14 is a group having a partial structure represented by formula (1a).SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In recent years, as the integration and speed of LSIs have become higher, there has been a demand for finer pattern rules, and deep ultraviolet lithography and extreme ultraviolet (EUV) lithography are seen as promising next-generation microfabrication technologies. In particular, photolithography using ArF excimer laser light is an essential technology for ultra-fine processing of 0.13 μm or less.

[0003] ArF lithography began to be used partially in the fabrication of 130nm node devices, but became the main lithography technology for 90nm node devices. Initially, 157nm lithography using F2 lasers was seen as a promising lithography technology for the next 45nm node, but various issues caused delays in development. ArF immersion lithography, which can achieve high resolution by inserting a liquid with a higher refractive index than air, such as water, ethylene glycol, or glycerin, between the projection lens and the wafer, has suddenly emerged (Non-Patent Document 1), and is now in the practical stage. Immersion lithography requires a resist composition that is resistant to dissolution in water.

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

[0005] In recent years, along with positive-tone resists developed with alkaline aqueous solutions, negative-tone resists developed with organic solvents have also been attracting attention. To resolve extremely fine hole patterns that cannot be achieved with positive-tone exposure, a high-resolution positive resist composition is used and developed with an organic solvent to form a negative pattern. Furthermore, studies are also underway to achieve double the resolution by combining two development steps, alkaline aqueous solution development and organic solvent development. Conventional positive-tone 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] In order to adapt to the rapid miniaturization of semiconductor devices in recent years, the development of resist compositions is progressing along with the development of process technologies. Various photoacid generators have been investigated, and sulfonium salts consisting of a triphenylsulfonium cation and a perfluoroalkanesulfonate anion are commonly used. However, the acid generated, perfluoroalkanesulfonic acid, particularly perfluorooctanesulfonic acid (PFOS), is difficult to decompose, has bioaccumulative potential, and is toxic, making its use in resist compositions difficult. Therefore, photoacid generators that generate perfluorobutanesulfonic acid are currently used. However, when used in resist compositions, the generated acid diffuses significantly, making it difficult to achieve high resolution. In response to this problem, various partially fluorinated alkanesulfonic acids and salts thereof have been developed. For example, Patent Document 1 describes, as prior art, photoacid generators that generate α,α-difluoroalkanesulfonic acids upon exposure, specifically di(4-tert-butylphenyl)iodonium 1,1-difluoro-2-(1-naphthyl)ethanesulfonate and photoacid generators that generate α,α,β,β-tetrafluoroalkanesulfonic acids. However, although the fluorine substitution rate of these compounds is reduced, they do not have decomposable substituents such as ester structures, and therefore are insufficient from the standpoint of environmental safety due to their facile decomposition. Furthermore, there are limitations on molecular design for changing the size of the alkanesulfonic acid, and the starting materials containing fluorine atoms are expensive.

[0007] Furthermore, as circuit linewidths shrink, the impact of acid diffusion on resist composition contrast degradation has become increasingly severe. This is because the pattern dimensions approach the acid diffusion length, leading to a larger mask error factor (MEF), which increases the difference between the mask and wafer dimensions. This leads to a decrease in mask fidelity and pattern rectangularity. Therefore, to fully realize the benefits of shorter wavelengths and higher NAs, it is necessary to increase dissolution contrast or suppress acid diffusion more than with conventional materials. One solution is to reduce acid diffusion by lowering the bake temperature, which can improve the MEF, but this inevitably results in lower sensitivity.

[0008] Introducing bulky substituents or polar groups into photoacid generators is effective in suppressing acid diffusion. Patent Document 4 describes photoacid generators containing 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 design possibilities. In particular, photoacid generators containing 2-(1-adamantyloxy)-1,1,3,3,3-pentafluoropropane-1-sulfonic acid, which has a bulky substituent, exhibit low acid diffusion. Patent Documents 5 to 7 describe photoacid generators containing fused-ring lactones, sultones, or thiolactones as polar groups. While some performance improvements have been confirmed due to the acid diffusion suppression effect of introducing polar groups, this is still insufficient to achieve high-level control of acid diffusion, and lithography performance is unsatisfactory when considering factors such as MEF, pattern shape, and sensitivity.

[0009] Introducing a polar group into the anion of a photoacid generator is effective in suppressing acid diffusion, but is disadvantageous in terms of solvent solubility. Patent Documents 8 and 9 attempt to ensure solvent solubility by introducing an alicyclic group into the cation portion of the photoacid generator, specifically by introducing a cyclohexane ring or an adamantane ring. While the introduction of such an alicyclic group improves solubility, a certain number of carbon atoms is required to ensure solubility, which results in a bulky molecular structure of the photoacid generator, resulting in degradation of lithography performance such as line width roughness (LWR) and dimensional uniformity (CDU) during the formation of fine patterns.

[0010] Furthermore, Patent Document 10 describes a photoacid generator that generates a fluoroalkanesulfonic acid having an anion with an aromatic fused ring derived from anthracene. While this has been confirmed to improve lithography performance to a certain extent, the alkane sulfonic acid structure lacks rigidity and has recently been subject to regulation as an organofluorine compound subject to PFAS, raising concerns about its impact on the environment and human body. To meet the demand for further miniaturization, the development of a new photoacid generator is important, and there is a need for a photoacid generator that has adequately controlled acid diffusion, excellent solvent solubility, and improves lithography performance. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-281974 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-281975 [Patent Document 3] Patent No. 4554665 [Patent Document 4] Japanese Patent Application Laid-Open No. 2007-145797 [Patent Document 5] Patent No. 5061484 [Patent Document 6] Japanese Patent Application Laid-Open No. 2016-147879 [Patent Document 7] Japanese Patent Application Laid-Open No. 2015-63472 [Patent Document 8] Patent No. 5573098 [Patent Document 9] Patent No. 6461919 [Patent Document 10] Patent No. 7109178 [Non-patent literature]

[0012] [Non-Patent Document 1] Journal of Photopolymer Science and Technology, Vol. 17, No. 4, p. 587-601 (2004) Summary of the Invention [Problem to be solved by the invention]

[0013] In response to recent demands for high resolution resist patterns, resist compositions that use conventional onium salt-type photoacid generators are unable to sufficiently suppress acid diffusion, which can result in degradation of lithography performance such as contrast, MEF, and LWR.

[0014] The present invention has been made in view of the above circumstances, and has an object to provide an onium salt used in a chemically amplified resist composition that exhibits excellent solvent solubility, high sensitivity, high contrast, and excellent lithography performance such as exposure latitude (EL) and LWR, particularly in photolithography using high-energy rays such as KrF excimer laser light, ArF excimer laser light, electron beam (EB), and EUV; a chemically amplified resist composition that contains the onium salt as a photoacid generator; and a pattern formation method that uses the chemically amplified resist composition. [Means for solving the problem]

[0015] As a result of extensive research into achieving the above-mentioned object, the present inventors have found that onium salts containing a sulfonate anion having a substituted fused ring structure and an aromatic sulfonic acid structure have excellent solvent solubility, and that chemically amplified resist compositions using such onium salts as photoacid generators have high sensitivity and high contrast, are extremely effective in suppressing acid diffusion, and are excellent in lithography performance such as EL and LWR, and are extremely effective in forming fine patterns, which has led to the completion of the present invention.

[0016] That is, the present invention provides the following onium salt, chemically amplified resist composition, and pattern forming method. 1. An onium salt represented by the following formula (1): [ka] [In the formula, R 1 ~R 12 are each independently a hydrogen atom, a halogen atom, or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. R 13 and R 14 One of the groups is a group having a partial structure represented by the following formula (1a), and the other is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a hydrogen atom, a halogen atom, or a heteroatom. Also, R 1 ~R 14 At least two of may be bonded to each other to form a ring together with the carbon atoms to which they are bonded, or together with the carbon atoms to which they are bonded and the carbon atoms therebetween. Z + is an onium cation. [ka] (In the formula, m1 is 0 or 1. When m1 is 0, m2 is an integer of 0 to 4, and when m1 is 1, m2 is an integer of 0 to 6. When m1 is 0, m3 is an integer of 0 to 3, and when m1 is 1, m3 is an integer of 0 to 5. However, when m1 is 0, m2+m3 is an integer of 0 to 4, and when m1 is 1, m2+m3 is an integer of 0 to 6. R F is a fluorine atom, a fluorinated alkyl group having 1 to 6 carbon atoms, a fluorinated alkoxy group having 1 to 6 carbon atoms, or a fluorinated alkylthio group having 1 to 6 carbon atoms. R 15 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, and when m3 is 2 or more, a plurality of R 15 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. L A and L B are each independently a single bond, an ether bond, an ester bond, an amide bond, a sulfonate ester bond, a sulfonamide bond, a carbonate bond or a carbamate bond. X Lis a single bond or a hydrocarbylene group having 1 to 40 carbon atoms which may contain a heteroatom.)] 2. An onium salt of formula 1, which is represented by the following formula (1A): [ka] (In the formula, R 1 ~R 13 , R 15 , L A , X L , R F , m1 to m3 and Z + is the same as above.) 3. An onium salt of 2 represented by the following formula (1B): [ka] (In the formula, R 5 , R 10 ~R 13 , R 15 , L A , X L , R F , m1 to m3 and Z + is the same as above. m4 and m5 each independently represent an integer of 0 to 4. R 16 and R 17 are each independently a hydrogen atom, a halogen atom, or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 16 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded, or together with the carbon atoms to which they are bonded and the carbon atoms therebetween, and when m5 is 2 or more, a plurality of R 17 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded, or together with the carbon atoms to which they are bonded and the carbon atoms therebetween. 4. An onium salt of 3, which is represented by the following formula (1C): [ka] (In the formula, R 5 , R 10 ~R 13 , R16 , R 17 , L A , X L , m4, m5 and Z + is the same as above.) 5.Z + is a sulfonium cation represented by the following formula (cation-1) or an iodonium cation represented by the following formula (cation-2). [ka] (In the formula, R ct1 ~R ct5 are each independently a halogen atom or a hydrocarbyl group having 1 to 30 carbon atoms which may contain a heteroatom. ct1 and R ct2 may be bonded to each other to form a ring together with the sulfur atom to which they are attached. 6. A photoacid generator comprising an onium salt according to any one of 1 to 5. 7. A chemically amplified resist composition containing a photoacid generator according to claim 6. 8. The chemically amplified resist composition of 7, comprising a base polymer containing a repeating unit represented by the following formula (a1): [ka] (In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X 1 is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OX 11 -, and the phenylene group or naphthylene group may be substituted with a halogen atom or an alkoxy group having 1 to 10 carbon atoms which may contain a fluorine atom. 11 is a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring. * represents a bond to a carbon atom in the main chain. AL 1 is an acid labile group. 9. The chemically amplified resist composition of 8, wherein the base polymer contains a repeating unit represented by the following formula (a2): [ka] (In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X 2 is a single bond or *-C(=O)-O-. * represents a bond to a carbon atom in the main chain. R 21 represents a halogen atom, a cyano group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbyloxycarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom. AL 2 is an acid labile group. a is an integer from 0 to 4. 10. The chemically amplified resist composition of 8 or 9, wherein the base polymer contains a repeating unit represented by the following formula (b1) or (b2): [ka] (In the formula, R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y 1 is a single bond or *-C(=O)-O-. * represents a bond to a carbon atom in the main chain. R 31 is a group having 1 to 20 carbon atoms and containing at least one structure selected from a hydrogen atom, a hydroxy group other than a phenolic hydroxy group, a cyano group, a carbonyl group, a carboxy group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, and a carboxylic anhydride (-C(=O)-OC(=O)-). R 32represents a halogen atom, a hydroxy group, a nitro group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbyloxycarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom. b is an integer from 1 to 4, and c is an integer from 0 to 4, provided that 1≦b+c≦5. 11. The chemically amplified resist composition of any one of 8 to 10, wherein the base polymer comprises at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (c1), a repeating unit represented by the following formula (c2), a repeating unit represented by the following formula (c3), and a repeating unit represented by the following formula (c4): [ka] (In the formula, R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Z 1 is a single bond or a phenylene group. Z 2 is *-C(=O)-OZ 21 -, *-C(=O)-NH-Z 21 -or*-OZ 21 -It is. Z 21 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, or a divalent group obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Z 3 are each independently a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OZ 31 -It is. Z 31 is an aliphatic hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the aliphatic hydrocarbylene group may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring. Z 4are each independently a single bond, **-Z 41 -C(=O)-O-, **-C(=O)-NH-Z 41 -or **-OZ 41 -It is. It is. Z 41 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a hetero atom. Z 5 are each independently a single bond, *-Z 51 -C(=O)-O-, *-C(=O)-NH-Z 51 -or*-OZ 51 -It is. Z 51 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Z 6 represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, *-C(=O)-OZ 61 -, *-C(=O)-N(H)-Z 61 -or*-OZ 61 -It is. Z 61 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, or a phenylene group substituted with a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. * represents a bond to a carbon atom in the main chain. ** represents Z 3 Represents a bond with . R 41 and R 42 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 41 and R 42 may be bonded to each other to form a ring together with the sulfur atom to which they are attached. L 1 is a single bond, an ether bond, an ester bond, a carbonyl group, a sulfonate ester bond, a carbonate bond or a carbamate bond. Rf 1 and Rf 2 are each independently a fluorine atom or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Rf 3 and Rf 4 are each independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Rf 5 and Rf 6 are each independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms, provided that all Rf 5 and Rf 6 cannot simultaneously become a hydrogen atom. M - is a non-nucleophilic counterion. A + is an onium cation. d is an integer from 0 to 3. 12. The chemically amplified resist composition according to any one of 7 to 11, further comprising an organic solvent. 13. The chemically amplified resist composition according to any one of 7 to 12, further comprising a quencher. 14. The chemically amplified resist composition according to any one of 7 to 13, further comprising a photoacid generator other than the photoacid generator according to 6. 15. The chemically amplified resist composition according to any one of 7 to 14, further comprising a surfactant. 16. A pattern forming method comprising the steps of forming a resist film on a substrate using any one of the chemically amplified resist compositions of 7 to 15, exposing the resist film to high-energy rays, and developing the exposed resist film using a developer. 17. The pattern formation method of 16, wherein the high-energy radiation is KrF excimer laser light, ArF excimer laser light, EB, or EUV having a wavelength of 3 to 15 nm. [Effects of the Invention]

[0017] When a pattern is formed using a chemically amplified resist composition containing the onium salt of the present invention as a photoacid generator, the resist composition exhibits high sensitivity, excellent acid diffusion suppression ability, improved lithography performance such as MEF and LWR, and can suppress collapse of the resist pattern during fine pattern formation. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a nuclear magnetic resonance spectrum (H-NMR / DMSO-d) of the onium salt PAG-1 synthesized in Example 1-1. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be described in detail below. In the following description, some structures represented by chemical formulas may have asymmetric carbon atoms, and enantiomers or diastereomers may exist. In such cases, a single formula will be used to represent all isomers. These isomers may be used singly or as a mixture of two or more.

[0020] [Onium salts] The onium salt of the present invention is represented by the following formula (1): [ka]

[0021] In formula (1), R 1 ~R 12 R are each independently a hydrogen atom, a halogen atom, or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 13 and R 14 One of the groups is a group having a partial structure represented by formula (1a) described below, and the other is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a hydrogen atom, a halogen atom, or a heteroatom.

[0022] Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 20 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, and an icosyl group; a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cyclopropylmethyl group, and a 4-methyl Examples of such groups include saturated cyclic 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; unsaturated cyclic hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclohexenyl; aryl groups having 6 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 groups. 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 a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy 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 sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, or the like.

[0023] Also, R 1 ~R 14At least two of the above may be bonded to each other to form a ring together with the carbon atoms to which they are bonded, or together with the carbon atoms to which they are bonded and the carbon atoms between them. Specific examples of the ring formed in this case include alicyclic rings such as a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a norbornane ring, and an adamantane ring, and aromatic rings such as a benzene ring, a naphthalene ring, and an anthracene ring. Furthermore, some or all of the hydrogen atoms in the ring may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and some of the -CH2- groups in the ring may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms, resulting in the ring containing a hydroxy 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 sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, or the like. Specific examples thereof include R 1 Examples of the ring include the same as those exemplified as the hydrocarbyl group represented by the following formula: The ring is preferably an aromatic ring, more preferably a benzene ring.

[0024] In formula (1), R 13 or R 14 is a group having a partial structure represented by the following formula (1a). 14 is preferably a group having a partial structure represented by the following formula (1a). [ka]

[0025] In formula (1a), m1 is 0 or 1. When m1 is 0, it is a benzene ring, and when m1 is 1, it is a naphthalene ring, but from the viewpoint of solvent solubility, m1 is preferably a benzene ring of 0. When m1 is 0, m2 is an integer of 0 to 4, and when m1 is 1, it is an integer of 0 to 6. When m1 is 0, m2 is preferably 4, and when m1 is 1, it is preferably 4, 5, or 6. When m1 is 0, m3 is an integer of 0 to 3, and when m1 is 1, it is an integer of 0 to 5. However, m2+m3 is 0 to 4 when m1 is 0, and 0 to 6 when m1 is 1.

[0026] In formula (1a), R F R is a fluorine atom, a fluorinated alkyl group having 1 to 6 carbon atoms, a fluorinated alkoxy group having 1 to 6 carbon atoms, or a fluorinated alkylthio group having 1 to 6 carbon atoms. F is preferably a fluorine atom, a trifluoromethyl group, a difluoromethyl group, a trifluoromethoxy group, a difluoromethoxy group, a trifluoromethylthio group, or a difluoromethylthio group, and more preferably a fluorine atom, a trifluoromethyl group, or a trifluoromethoxy group. By containing a fluorine atom or one of these substituents having a fluorine atom, the acid strength of the generated acid is improved due to an electron-withdrawing effect, so that the deprotection reaction of acid labile groups such as tertiary esters and tertiary ethers, which will be described later, proceeds smoothly. When m2 is 2, 3, or 4, each R F may be the same as or different from each other.

[0027] In formula (1a), R 15 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R 1 When m3 is 2 or more, each R 15 may be the same or different. When m3 is 2 or more, multiple R 15may be bonded to each other to form a ring together with the carbon atoms to which they are bonded. The ring is preferably a 5- to 8-membered ring.

[0028] In formula (1a), L A and L B are each independently a single bond, an ether bond, an ester bond, an amide bond, a sulfonate ester bond, a sulfonamide bond, a carbonate bond, or a carbamate bond. Of these, a single bond, an ether bond, or an ester bond is preferred.

[0029] In formula (1a), X L is a single bond or a hydrocarbylene group having 1 to 40 carbon atoms which may contain a heteroatom. The hydrocarbylene group may be linear, branched, or cyclic, and specific examples thereof include an alkanediyl group, a cyclic saturated hydrocarbylene group, and an arylene group. Specific examples of the heteroatom include an oxygen atom, a nitrogen atom, and a sulfur atom.

[0030] X L Specific examples of the hydrocarbylene group having 1 to 40 carbon atoms and optionally containing a hetero atom, represented by the formula (I), include, but are not limited to, those shown below. In the formula (I), * represents L A and L B Represents a bond with . [ka]

[0031] [ka]

[0032] [ka]

[0033] [ka]

[0034] Of these, X L -0~X L -22 and X L -47~X L -58 is preferred.

[0035] The onium salt represented by formula (1) is preferably one represented by the following formula (1A). [ka] (In the formula, R 1 ~R 13 , R 15 , L A , X L , R F , m1 to m3 and Z + is the same as above.)

[0036] The onium salt represented by formula (1A) is preferably one represented by the following formula (1B). [ka] (In the formula, R 5 , R 10 ~R 13 , R 15 , L A , X L , R F , m1 to m3 and Z + is the same as above.

[0037] In formula (1B), m4 and m5 each independently represent an integer of 0 to 4. Of these, it is preferable that both are 0 to 2 from the viewpoint of procuring raw materials.

[0038] In formula (1B), R 16 and R 17 are each independently a hydrogen atom, a halogen atom, or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. Specific examples of the halogen atom and hydrocarbyl group include R 1 ~R 14 Examples of the halogen atom and hydrocarbyl group represented by the formula (I) include the same as those exemplified above.

[0039] When m4 is 2 or more, multiple R 16 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded and the carbon atoms therebetween, and when m5 is 2 or more, a plurality of R 17 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded and the carbon atoms between them. Specific examples of the ring formed in this case include R 1 ~R 14 Examples of the ring that can be formed by bonding at least two of the above groups together include the same rings as those exemplified above.

[0040] The onium salt represented by formula (1B) is preferably one represented by the following formula (1C). [ka] (In the formula, R 5 , R 10 ~R 13 , R 16 , R 17 , L A , X L , m4, m5 and Z + is the same as above.)

[0041] Specific examples of the anion of the onium salt represented by formula (1) include, but are not limited to, those shown below: In the following formula, Me is a methyl group. [ka]

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[0218] [ka]

[0219] [ka]

[0220] [ka]

[0221] [ka]

[0222] In formula (1), Z + is an onium cation. The onium cation is preferably a sulfonium cation represented by the following formula (cation-1) or an iodonium cation represented by the following formula (cation-2). [ka]

[0223] In formulas (cation-1) and (cation-2), R ct1 ~R ct5are each independently a halogen atom or a hydrocarbyl group having 1 to 30 carbon atoms which may contain a heteroatom.

[0224] R ct1 ~R ct5 Examples of the halogen atom represented by the formula (I) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0225] R ct1 ~R ct5 The hydrocarbyl group represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 30 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl; saturated cyclic hydrocarbyl groups having 3 to 30 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; alkenyl groups having 2 to 30 carbon atoms, such as vinyl, allyl, propenyl, butenyl, and hexenyl; unsaturated cyclic hydrocarbyl groups having 3 to 30 carbon atoms, such as cyclohexenyl; aryl groups having 6 to 30 carbon atoms, such as phenyl, naphthyl, and thienyl; aralkyl groups having 7 to 30 carbon atoms, such as benzyl, 1-phenylethyl, and 2-phenylethyl; and groups obtained by combining these, with aryl groups being preferred. 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, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy 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 sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc.

[0226] Also, R ct1 and R ct2However, they may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. In this case, examples of the ring structure include those represented by the following formulas. [ka] (In the formula, the dashed line indicates R ct3 )

[0227] Specific examples of the sulfonium cation represented by formula (cation-1) include, but are not limited to, those shown below. [ka]

[0228] [ka]

[0229] [ka]

[0230] [ka]

[0231] [ka]

[0232] [ka]

[0233] [ka]

[0234] [ka]

[0235]

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[0246] [ka]

[0247] [ka]

[0248] [ka]

[0249] [ka]

[0250] [ka]

[0251] [ka]

[0252] [ka]

[0253] [ka]

[0254] Specific examples of the iodonium cation represented by formula (cation-2) include, but are not limited to, those shown below. [ka]

[0255] [ka]

[0256] Specific examples of the onium salt of the present invention include any combination of the above-mentioned anions and cations.

[0257] The onium salt of the present invention can be synthesized by a known method. As an example, a method for producing an onium salt represented by the following formula (PAG-1-ex) will be described, but the synthesis method is not limited thereto. [ka] (In the formula, R 1 ~R 13 , R F , R 15 , L A , X L , m1 to m3 and Z + is the same as above. + is the counter cation. X - is the counter anion.)

[0258] The first step involves the reaction of raw materials SM-1, available commercially or obtained by a known synthetic method, with raw materials SM-2 to obtain intermediate In-1. Various condensation agents can be used to directly form an ester bond between the carboxyl group of raw material SM-1 and the hydroxyl group of raw material SM-2. Examples of condensation agents include N,N'-dicyclohexylcarbodiimide, N,N'-diisopropylcarbodiimide, 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride. However, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride is preferred due to the ease of removal of the urea compound produced as a by-product after the reaction. The reaction is carried out by dissolving raw materials SM-1 and SM-2 in a halogenated solvent such as methylene chloride and adding the condensation agent. The addition of 4-dimethylaminopyridine (DMAP) as a catalyst can improve the reaction rate. The reaction time is usually about 12 to 24 hours, although it is desirable to monitor the reaction by silica gel thin layer chromatography (TLC) to complete the reaction from the viewpoint of yield. After the reaction is stopped, the by-product urea compound is removed by filtration or washing with water, if necessary, and the reaction solution is then subjected to a conventional aqueous work-up to obtain intermediate In-1. The obtained intermediate In-1 may be purified, if necessary, by conventional methods such as chromatography or recrystallization.

[0259] In the second step, the obtained intermediate In-1 is converted to Z + X - This is a process for obtaining an onium salt (PAG-1-ex) by salt exchange with an onium salt (raw material SM-3) represented by the formula: - The preferred exchange anions are chloride ions, bromide ions, iodide ions, or methyl sulfate anions, as these tend to facilitate quantitative exchange reactions. It is desirable to monitor the progress of the reaction by TLC in terms of yield. The onium salt (PAG-1-ex) can be obtained from the reaction mixture by a standard aqueous work-up. If necessary, it can be purified by standard methods such as chromatography or recrystallization.

[0260] In the above scheme, the ion exchange in the second step can be easily carried out by a known method, for example, see JP-A-2007-145797.

[0261] The above-mentioned production method is merely an example, and the method for producing the onium salt of the present invention is not limited to this.

[0262] A structural feature of the onium salt of the present invention is that a substituted fused ring structure and an aromatic sulfonic acid structure are introduced into the anion. The substituted fused ring structure has a large excluded volume and acts as a bulky substituent, highly suppressing the diffusion of the generated acid. Furthermore, its resistance to alkaline developers reduces film loss in unexposed areas of the pattern. On the other hand, the aromatic sulfonic acid structure provides a rigid structure for the generated acid, thereby suppressing acid diffusion. The aromatic ring forming the aromatic sulfonic acid structure preferably contains a fluorine atom or an electron-withdrawing sulfonic acid ester bond as a linking group, thereby increasing the acidity of the generated acid and efficiently deprotecting the acid-labile groups of the base polymer. Furthermore, fluorine atoms, although not as effective as iodine atoms, have a high EUV light absorption effect. Therefore, increasing the number of fluorine atoms increases the amount of secondary electrons generated, promoting cation decomposition and contributing to high sensitivity. Japanese Patent No. 7109178 proposes an alkanesulfonic acid-type photoacid generator having 2 to 4 fluorine atoms, but because it is an alkanesulfonic acid, acid diffusion is relatively large and solvent solubility is poor, raising concerns about development defects. Due to these synergistic effects, the resist composition containing the onium salt of the present invention has high sensitivity and low acid diffusibility, thereby enabling the formation of patterns that are excellent in LWR of line patterns and CDU of hole patterns and are resistant to pattern collapse, making it suitable for forming fine patterns.

[0263] The onium salt can be suitably used as a photoacid generator.

[0264] [Chemically amplified resist composition] [(A) Photoacid generator] The chemically amplified resist composition of the present invention contains, as an essential component, (A) a photoacid generator comprising an onium salt represented by formula (1).

[0265] In the chemically amplified resist composition of the present invention, the content of the photoacid generator (A), which is an onium salt represented by formula (1), 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 below. A content of component (A) within this range is preferred because it provides good sensitivity and resolution and prevents problems with foreign matter after development of the resist film or during stripping. The photoacid generator (A) may be used alone, or two or more types may be used in combination.

[0266] [(B) Base polymer] The chemically amplified resist composition of the present invention may contain a base polymer as component (B). The base polymer (B) contains a repeating unit represented by the following formula (a1) (hereinafter also referred to as repeating unit a1): [ka]

[0267] In formula (a1), R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0268] In formula (a1), X 1 is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OX 11 -, and the phenylene group or naphthylene group may be substituted with a halogen atom or an alkoxy group having 1 to 10 carbon atoms which may contain a fluorine atom. 11 is a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring. * represents a bond to a carbon atom in the main chain.

[0269] In formula (a1), AL 1is an acid labile group. Examples of the acid labile group include those described in JP-A Nos. 2013-80033 and 2013-83821.

[0270] Typical examples of the acid labile group include those represented by the following formulae (AL-1) to (AL-3). [ka] (In the formula, the dashed lines represent bonds.)

[0271] In formulas (AL-1) and (AL-2), R L1 and R L2 are each independently a hydrocarbyl group having 1 to 40 carbon atoms, which may contain a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a fluorine atom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. The hydrocarbyl group preferably has 1 to 20 carbon atoms.

[0272] In formula (AL-1), k is an integer of 0 to 10, and an integer of 1 to 5 is preferred.

[0273] In formula (AL-2), R L3 and R L4 are each independently a hydrogen atom or a 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 saturated or unsaturated, and may be linear, branched, or cyclic. The hydrocarbyl group preferably has 1 to 20 carbon atoms. In addition, R L2 , R L3 and R L4 Any two of these may be bonded to each other to form a ring having 3 to 20 carbon atoms together with the carbon atom or the carbon atom and oxygen atom to which they are bonded. As the ring, a ring having 4 to 16 carbon atoms is preferred, and an alicyclic ring is particularly preferred.

[0274] In formula (AL-3), R L5 , R L6 and R L7are each independently a hydrocarbyl group having 1 to 20 carbon atoms, which may contain a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a fluorine atom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. The hydrocarbyl group preferably has 1 to 20 carbon atoms. In addition, R L5 , R L6 and R L7 Any two of these may be bonded to each other to form, together with the carbon atoms to which they are bonded, a ring having 3 to 20 carbon atoms. As the ring, a ring having 4 to 16 carbon atoms is preferred, and an alicyclic ring is particularly preferred.

[0275] Specific examples of the repeating unit a1 include, but are not limited to, the following: A and AL 1 is the same as above. [ka]

[0276] [ka]

[0277] [ka]

[0278] The base polymer may further contain a repeating unit represented by the following formula (a2) (hereinafter also referred to as repeating unit a2). [ka]

[0279] In formula (a2), R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 2 is a single bond or *-C(=O)-O-. * represents a bond to a carbon atom in the main chain. R 21is a halogen atom, a cyano group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbyloxycarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom. AL 2 is an acid labile group. The acid labile group may be AL 1 Examples of the acid labile group include the same as those exemplified above. a is an integer of 0 to 4, and preferably 0 or 1.

[0280] Specific examples of the repeating unit a2 include, but are not limited to, the following: A and AL 2 is the same as above. [ka]

[0281] [ka]

[0282] The base polymer preferably 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]

[0283] In formulas (b1) and (b2), R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1 is a single bond or *-C(=O)-O-. * represents a bond to a carbon atom in the main chain. R 31R is a group having 1 to 20 carbon atoms and containing at least one structure selected from a hydrogen atom, a hydroxy group other than a phenolic hydroxy group, a cyano group, a carbonyl group, a carboxy group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, and a carboxylic anhydride (-C(=O)-OC(=O)-). 32 is a halogen atom, a hydroxy group, a nitro group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbyloxycarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom. b is an integer of 1 to 4. c is an integer of 0 to 4, provided that 1≦b+c≦5.

[0284] Specific examples of the repeating unit b1 include, but are not limited to, the following: A is the same as above. [ka]

[0285] [ka]

[0286] [ka]

[0287] [ka]

[0288] [ka]

[0289]

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[0300] Specific examples of the repeating unit b2 include, but are not limited to, those shown below. A is the same as above. [ka]

[0301] [ka]

[0302] [ka]

[0303] [ka]

[0304] [ka]

[0305] As the repeating unit b1 or b2, those having a lactone ring as a polar group are particularly preferred for ArF lithography, and those having a phenol moiety are preferred for KrF lithography, EB lithography and EUV lithography.

[0306] The base polymer may further contain at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (c1) (hereinafter also referred to as repeating unit c1), a repeating unit represented by the following formula (c2) (hereinafter also referred to as repeating unit c2), a repeating unit represented by the following formula (c3) (hereinafter also referred to as repeating unit c3), and a repeating unit represented by the following formula (c4) (hereinafter also referred to as repeating unit c4). [ka]

[0307] In formulas (c1) to (c4), R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1 is a single bond or a phenylene group. 2 is *-C(=O)-OZ 21 -, *-C(=O)-NH-Z 21 -or*-OZ 21 -It is. Z 21 Z is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, or a divalent group obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. 3 are each independently a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OZ 31 -It is. Z 31 is an aliphatic hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the aliphatic hydrocarbylene group may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring. 4 are each independently a single bond, **-Z 41 -C(=O)-O-, **-C(=O)-NH-Z 41 -or **-OZ 41 -It is. It is. Z 41 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. 5 are each independently a single bond, *-Z 51 -C(=O)-O-, *-C(=O)-NH-Z 51 -or*-OZ 51 -It is. Z 51 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. 6 represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, *-C(=O)-OZ 61 -, *-C(=O)-N(H)-Z 61 -or*-OZ 61 -It is. Z61 is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, or a phenylene group substituted with a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. * represents a bond to a carbon atom in the main chain. ** represents a bond to a carbon atom in the main chain. Z 3 Represents a bond with .

[0308] Z 21 , Z 31 and Z 61 The aliphatic hydrocarbylene group represented by the formula (I) may be linear, branched or cyclic, and specific examples thereof include a methanediyl group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a propane-2,2-diyl group, a butane-1,1-diyl group, a butane-1,2-diyl group, a butane-1,3-diyl group, a butane- Examples of the alkyl group include alkanediyl groups such as a 2,3-diyl group, a butane-1,4-diyl group, a 1,1-dimethylethane-1,2-diyl group, a pentane-1,5-diyl group, a 2-methylbutane-1,2-diyl group, and a hexane-1,6-diyl group; cycloalkanediyl groups such as a cyclopropanediyl group, a cyclobutanediyl group, a cyclopentanediyl group, and a cyclohexanediyl group; and groups obtained by combining these groups.

[0309] Z 41 and Z 51 The hydrocarbylene group represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include, but are not limited to, those shown below. [ka] (In the formula, the dashed lines represent bonds.)

[0310] In formula (c1), R 41 and R 42are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl; saturated cyclic hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; alkenyl groups having 2 to 20 carbon atoms, such as vinyl, allyl, propenyl, butenyl, and hexenyl; unsaturated cyclic hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclohexenyl; aryl groups having 6 to 20 carbon atoms, such as phenyl, naphthyl, and thienyl; aralkyl groups having 7 to 20 carbon atoms, such as benzyl, 1-phenylethyl, and 2-phenylethyl; and groups obtained by combining these, with aryl groups being preferred. 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, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy 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 sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc.

[0311] Also, R 41 and R 42 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. In this case, the ring is the same as that of R ct1 and R ct2 Examples of the ring that can be formed by bonding these together with the sulfur atom to which they are bonded are the same as those exemplified above.

[0312] Specific examples of the cation of the repeating unit c1 include, but are not limited to, the following: A is the same as above. [ka]

[0313] [ka]

[0314] [ka]

[0315] [ka]

[0316] [ka]

[0317] [ka]

[0318] [ka]

[0319] In formula (c1), M -is a non-nucleophilic counter ion. Examples of the non-nucleophilic counter ion include halide ions, sulfonate anions, imidate anions, and methide anions. Specific examples of the halide ions include chloride ions and bromide ions. Specific examples of the sulfonate anions (sulfonate ions) include fluoroalkylsulfonate ions such as triflate ions, 1,1,1-trifluoroethanesulfonate ions, and nonafluorobutanesulfonate ions; arylsulfonate ions such as tosylate ions, benzenesulfonate ions, 4-fluorobenzenesulfonate ions, and 1,2,3,4,5-pentafluorobenzenesulfonate ions; and alkylsulfonate ions such as mesylate ions and butanesulfonate ions. Specific examples of the imidate anions (imide ions) include bis(trifluoromethylsulfonyl)imide ions, bis(perfluoroethylsulfonyl)imide ions, and bis(perfluorobutylsulfonyl)imide ions. Specific examples of the methide acid anion (methide ion) include imide ions such as bis(trifluoromethylsulfonyl)imide ion, bis(perfluoroethylsulfonyl)imide ion, and bis(perfluorobutylsulfonyl)imide ion; tris(trifluoromethylsulfonyl)methide ion, and tris(perfluoroethylsulfonyl)methide ion.

[0320] Other examples of the non-nucleophilic counter ion include anions represented by any of the following formulae (c1-1) to (c1-4). [ka]

[0321] In formula (c1-1), R fa is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (c1-1-1) described below. fa1Examples of the hydrocarbyl group represented by the formula (I) include the same as those exemplified above.

[0322] The anion represented by formula (c1-1) is preferably one represented by the following formula (c1-1-1): [ka]

[0323] In formula (c1-1-1), Q 11 and Q 12 are each independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms, but in order to improve solvent solubility, it is preferable that at least one of them is a trifluoromethyl group. m is an integer of 0 to 4, and is particularly preferably 1. R fa1 is a hydrocarbyl group having 1 to 35 carbon atoms which may contain a heteroatom. The heteroatom is preferably an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom, or the like, and more preferably an oxygen atom. From the viewpoint of obtaining high resolution in the formation of a fine pattern, the hydrocarbyl group is particularly preferably one having 6 to 30 carbon atoms.

[0324] In formula (c1-1-1), R fa1The hydrocarbyl group having 1 to 35 carbon atoms and represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 35 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a neopentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, a nonyl group, an undecyl group, a tridecyl group, a pentadecyl group, a heptadecyl group, and an icosyl group; a cyclopentyl group, a cyclohexyl group, a 1-adamantyl group, a 2-adamantyl group, a 1-adamantylmethyl group, a norbornyl group, a norbornyl group, and an alkyl group having 1 to 35 carbon atoms. Examples include cyclic saturated hydrocarbyl groups having 3 to 35 carbon atoms, such as bornylmethyl, tricyclodecyl, tetracyclododecyl, tetracyclododecylmethyl, and dicyclohexylmethyl; unsaturated aliphatic hydrocarbyl groups having 2 to 35 carbon atoms, such as allyl and 3-cyclohexenyl; aryl groups having 6 to 35 carbon atoms, such as phenyl, 1-naphthyl, 2-naphthyl, and 9-fluorenyl; aralkyl groups having 7 to 35 carbon atoms, such as benzyl and diphenylmethyl; and groups obtained by combining these.

[0325] 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, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy 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 sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc. Examples of hydrocarbyl groups containing hetero atoms include tetrahydrofuryl, methoxymethyl, ethoxymethyl, methylthiomethyl, acetamidomethyl, trifluoroethyl, (2-methoxyethoxy)methyl, acetoxymethyl, 2-carboxy-1-cyclohexyl, 2-oxopropyl, 4-oxo-1-adamantyl, and 3-oxocyclohexyl groups.

[0326] In formula (c1-1-1), L a1 is a single bond, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond or a carbamate bond, but from the viewpoint of synthesis, an ether bond or an ester bond is preferred, and an ester bond is more preferred.

[0327] Specific examples of the anion represented by formula (c1-1) include, but are not limited to, the following: 11 is the same as above, and Ac is an acetyl group. [ka]

[0328] [ka]

[0329] [ka]

[0330] [ka]

[0331] [ka]

[0332] [ka]

[0333] [ka]

[0334] [ka]

[0335] [ka]

[0336] [ka]

[0337] In formula (c1-2), R fb1 and R fb2 are each independently a hydrocarbyl group having 1 to 40 carbon atoms which may contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (c1-1-1): fa1 Examples of the hydrocarbyl group represented by R include the same as those exemplified above. fb1 and R fb2 is preferably a fluorine atom or a linear fluorinated alkyl group having 1 to 4 carbon atoms. fb1 and R fb2 are bonded to each other and form the bonded group (-CF2-SO2-N - -SO2-CF2-) together to form a ring, in which case R fb1 and R fb2 The group obtained by bonding together is preferably a fluorinated ethylene group or a fluorinated propylene group.

[0338] In formula (c1-3), R fc1 , R fc2 and R fc3 are each independently a hydrocarbyl group having 1 to 40 carbon atoms which may contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (c1-1-1): fa1 Examples of the hydrocarbyl group represented by R include the same as those exemplified above. fc1 , R fc2 and R fc3is preferably a fluorine atom or a linear fluorinated alkyl group having 1 to 4 carbon atoms. fc1 and R fc2 are bonded to each other and form the bonded group (-CF2-SO2-C - -SO2-CF2-) together to form a ring, in which case R fc1 and R fc2 The group obtained by bonding together is preferably a fluorinated ethylene group or a fluorinated propylene group.

[0339] In formula (c1-4), R fd is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (c1-1-1): fa1 Examples of the hydrocarbyl group represented by the formula (I) include the same as those exemplified above.

[0340] Specific examples of the anion represented by formula (c1-4) include, but are not limited to, the following: [ka]

[0341] [ka]

[0342] Further examples of the non-nucleophilic counter ion include anions having an aromatic ring substituted with an iodine atom or a bromine atom. Specific examples of such anions include those represented by the following formula (c1-5): [ka]

[0343] In formula (c1-5), x is an integer that satisfies 1≦x≦3. y and z are integers that satisfy 1≦y≦5, 0≦z≦3, and 1≦y+z≦5. y is preferably an integer that satisfies 1≦y≦3, more preferably 2 or 3. z is preferably an integer that satisfies 0≦z≦2.

[0344] In formula (c1-5), X BI 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.

[0345] In formula (c1-5), L 11 is a single bond, an ether bond, an ester bond, or a saturated hydrocarbylene group having 1 to 6 carbon atoms which may contain an ether bond or an ester bond. The saturated hydrocarbylene group may be linear, branched, or cyclic.

[0346] In formula (c1-5), L 12 represents a single bond or a divalent linking group having 1 to 20 carbon atoms when x is 1, and represents an (x+1)-valent linking group having 1 to 20 carbon atoms when x is 2 or 3, and the linking group may contain an oxygen atom, a sulfur atom, or a nitrogen atom.

[0347] In formula (c1-5), R fe is a hydroxy group, a carboxy group, a fluorine atom, a chlorine atom, a bromine atom or an amino group, or a hydrocarbyl group having 1 to 20 carbon atoms, a hydrocarbyloxy group having 1 to 20 carbon atoms, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms, a hydrocarbyloxycarbonyl group having 2 to 20 carbon atoms, a hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms or a hydrocarbylsulfonyloxy group having 1 to 20 carbon atoms which may contain a fluorine atom, a chlorine atom, a bromine atom, a hydroxy group, an amino group or an ether bond, or feA )(R feB ), -N(R feC )-C(=O)-R feD or -N(R feC )-C(=O)-OR feD R feA and R feBare each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms. feC is a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms, and may contain a halogen atom, a hydroxy 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 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 hydroxy 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 may be the same or different from each other.

[0348] Of these, R fe Examples of the hydroxyl group include -N(R feC )-C(=O)-R feD , -N(R feC )-C(=O)-OR feD fluorine atom, chlorine atom, bromine atom, methyl group, methoxy group, etc. are preferred.

[0349] In formula (c1-5), Rf 11 ~Rf 14 are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, and at least one of them is a fluorine atom or a trifluoromethyl group. 11 and Rf 12 may combine to form a carbonyl group. 13 and Rf 14 are preferably both fluorine atoms.

[0350] Specific examples of the anion represented by formula (c1-5) include, but are not limited to, the following: BI is the same as above. [ka]

[0351] [ka]

[0352] [ka]

[0353] [ka]

[0354] [ka]

[0355] [ka]

[0356] [ka]

[0357] [ka]

[0358] [ka]

[0359] [ka]

[0360]

change

[0361]

change

[0362]

change

[0363]

change

[0364]

change

[0365]

change

[0366]

change

[0367]

change

[0368]

change

[0369]

change

[0370] [ka]

[0371] [ka]

[0372] [ka]

[0373] Examples of the non-nucleophilic counter ion include a fluorobenzenesulfonate anion bonded to an aromatic group containing an iodine atom as described in Japanese Patent No. 6648726, an anion having a mechanism for decomposing with an 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, and an anion as described in Japanese Patent Application Publication No. 2018-92159.

[0374] Further examples of the non-nucleophilic counter ion include anions of bulky benzenesulfonic acid derivatives that do not contain fluorine atoms, as described in JP 2006-276759 A, JP 2015-117200 A, JP 2016-65016 A, and JP 2019-202974 A, and benzenesulfonic acid anions and alkylsulfonic acid anions that do not contain fluorine atoms bonded to aromatic groups containing iodine atoms, as described in Japanese Patent No. 6645464 A.

[0375] Further examples of the non-nucleophilic counter ion include anions of bissulfonic acid described in JP 2015-206932 A, anions of sulfonamides or sulfonimides having a sulfonic acid on one side and a different sulfonic acid on the other side described in WO 2020 / 158366 A, and anions of sulfonic acid on one side and carboxylic acid on the other described in JP 2015-24989 A.

[0376] In formulas (c2) and (c3), L 1 is a single bond, an ether bond, an ester bond, a carbonyl group, a sulfonate ester bond, a carbonate bond, or a carbamate bond. Among these, from the viewpoint of synthesis, an ether bond, an ester bond, or a carbonyl group is preferred, and an ester bond or a carbonyl group is more preferred.

[0377] In formula (c2), Rf 1 and Rf 2 are each independently a fluorine atom or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. 1 and Rf 2 In order to increase the acid strength of the generated acid, it is preferable that Rf be a fluorine atom. 3 and Rf 4 are each independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Of these, Rf 3 and Rf 4 At least one of these is preferably a trifluoromethyl group.

[0378] In formula (c3), Rf 5 and Rf 6 are each independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms, provided that all Rf 5 and Rf 6 cannot be simultaneously hydrogen atoms. Among these, Rf 5 and Rf 6 At least one of these is preferably a trifluoromethyl group.

[0379] In the formulae (c2) and (c3), d is an integer of 0 to 3, with 1 being preferred.

[0380] Specific examples of the anion of the repeating unit c2 include, but are not limited to, the following: A is the same as above, and Me is a methyl group. [ka]

[0381] [ka]

[0382] [ka]

[0383] [ka]

[0384] [ka]

[0385] [ka]

[0386] [ka]

[0387] [ka]

[0388] [ka]

[0389] Specific examples of the anion of the repeating unit c3 include, but are not limited to, the following: A is the same as above. [ka]

[0390] [ka]

[0391] [ka]

[0392] [ka]

[0393] [ka]

[0394] [ka]

[0395] [ka]

[0396] [ka]

[0397] Specific examples of the anion of the repeating unit c4 include, but are not limited to, the following: A is the same as above. [ka]

[0398] In formulas (c2) to (c4), A +is an onium cation. Examples of the onium cation include ammonium cation, sulfonium cation, and iodonium cation, with sulfonium cation and iodonium cation being preferred. Specific examples thereof include, but are not limited to, those exemplified as the sulfonium cation represented by formula (cation-1) and the iodonium cation represented by formula (cation-2), as well as those exemplified as the ammonium cation represented by formula (cation-3) described below.

[0399] Specific structures of the repeating units c1 to c4 include any combination of the above-mentioned anions and cations.

[0400] Of the repeating units c1 to c4, the repeating units c2, c3 and c4 are preferred from the viewpoint of controlling acid diffusion, the repeating units c2 and c4 are more preferred from the viewpoint of the acid strength of the generated acid, and the repeating unit c2 is more preferred from the viewpoint of solvent solubility.

[0401] The base polymer may further contain a repeating unit having a structure in which a hydroxy group is protected by an acid labile group (hereinafter also referred to as repeating unit d). The repeating unit d is not particularly limited as long as it has one or more structures in which a hydroxy group is protected and the protecting group is decomposed by the action of an acid to generate a hydroxy group, but is preferably one represented by the following formula (d1): [ka]

[0402] In formula (d1), R A is the same as above. R 41 R is a hydrocarbon group having 1 to 30 carbon atoms and a valence of (e+1), which may contain a heteroatom. 42 is an acid labile group. e is an integer of 1 to 4.

[0403] In formula (d1), R 42The acid labile group represented by R may be any group that can be deprotected by the action of an acid to generate a hydroxy group. 42 Although the structure is not particularly limited, an acetal structure, a ketal structure, an alkoxycarbonyl group, an alkoxymethyl group represented by the following formula (d2), and the like are preferred, and an alkoxymethyl group represented by the following formula (d2) is particularly preferred. [ka] (In the formula, * represents a bond. R 43 is a hydrocarbyl group having 1 to 15 carbon atoms.

[0404] R 42 Specific examples of the acid labile group represented by the formula (d2), the alkoxymethyl group represented by the formula (d3), 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.

[0405] The base polymer may further include a repeating unit e derived from indene, benzofuran, benzothiophene, acenaphthylene, chromone, coumarin, norbornadiene, or a derivative thereof. Specific examples of monomers that provide the repeating unit e include, but are not limited to, the following: [ka]

[0406] The base polymer may further include a repeating unit f derived from indane, vinylpyridine, or vinylcarbazole.

[0407] 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.

[0408] 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.

[0409] Furthermore, since the influence of Mw / Mn tends to increase as the pattern rules are miniaturized, in order to obtain a resist composition suitably used for fine pattern dimensions, Mw / Mn is preferably narrowly dispersed at 1.0 to 2.0. If within the above range, there are few low molecular weight and high molecular weight polymers, and there is no risk of foreign matter being seen on the pattern or the pattern shape deteriorating after exposure.

[0410] To synthesize the polymer, for example, monomers providing the above-described repeating units may be heated in an organic solvent with a radical polymerization initiator added thereto to perform polymerization.

[0411] 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 the polymerization initiator 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% based on the total amount of monomers to be polymerized. The reaction temperature is preferably 50 to 150°C, 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.

[0412] The polymerization initiator may be added to the monomer solution and then fed to the reaction vessel. Alternatively, an initiator solution may be prepared separately from the monomer solution and then fed to the reaction vessel independently. From the perspective of quality control, it is preferable to prepare the monomer solution and the initiator solution independently and then add them dropwise, since radicals generated from the initiator during the waiting time may cause the polymerization reaction to proceed, resulting in the formation of ultra-high molecular weight polymers. The acid labile group may be used as is after being introduced into the monomer, or may be protected or partially protected after polymerization. Furthermore, known chain transfer agents such as dodecyl mercaptan and 2-mercaptoethanol may be used in combination to adjust the molecular weight. In this case, the amount of the chain transfer agent added is preferably 0.01 to 20 mol % of the total amount of monomers to be polymerized.

[0413] In the case of a monomer containing a hydroxy group, the hydroxy group may be substituted with an acetal group, such as an ethoxyethoxy group, which is easily deprotected by an acid, during polymerization, and then deprotected with a weak acid and water after polymerization. Alternatively, the hydroxy group may be substituted with an acetyl group, a formyl group, a pivaloyl group, or the like, and then subjected to alkaline hydrolysis after polymerization.

[0414] When copolymerizing hydroxystyrene or hydroxyvinylnaphthalene, hydroxystyrene or hydroxyvinylnaphthalene and other monomers may be polymerized by heating in an organic solvent with the addition of a radical polymerization initiator. Alternatively, acetoxystyrene or acetoxyvinylnaphthalene may be used, and after polymerization, the acetoxy group may be deprotected by alkaline hydrolysis to form polyhydroxystyrene or hydroxypolyvinylnaphthalene.

[0415] The base that can be used in alkaline hydrolysis includes aqueous ammonia, triethylamine, etc. 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.

[0416] The amount of each monomer in the monomer solution may be appropriately set so as to achieve the preferred content ratio of the repeating units described above.

[0417] The polymer obtained by the above-described production method may be a reaction solution obtained by a polymerization reaction as a final product, or a powder obtained through a purification step such as a reprecipitation method in which a polymerization solution is added to a poor solvent to obtain a powder, and the resulting powder may be handled as a final product. However, from the viewpoint of work efficiency and quality stability, it is preferable to handle a polymer solution obtained by dissolving the powder obtained through the purification step in a solvent as a final product.

[0418] Specific examples of the solvent used in this case include ketones such as cyclohexanone and methyl-2-n-pentyl ketone, as described in paragraphs

[0144] to

[0145] of JP-A 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. 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 mono tert-butyl ether acetate; lactones such as GBL; alcohols such as diacetone alcohol (DAA); high-boiling alcohol solvents such as diethylene glycol, propylene glycol, glycerin, 1,4-butanediol, and 1,3-butanediol; and mixed solvents thereof.

[0419] The concentration of the polymer in the polymer solution is preferably 0.01 to 30% by mass, more preferably 0.1 to 20% by mass.

[0420] The reaction solution and polymer solution are preferably filtered through a filter, which is effective in stabilizing quality by removing foreign matter and gels that may cause defects.

[0421] Examples of filter materials used in the filter filtration include fluorocarbon, cellulose, nylon, polyester, and hydrocarbon-based materials. However, in the filtration process of resist compositions, filters made of fluorocarbons, such as Teflon (registered trademark), hydrocarbons such as polyethylene and polypropylene, or nylon are preferred. The pore size of the filter can be selected appropriately depending on the target cleanliness, but is preferably 100 nm or less, more preferably 20 nm or less. These filters may be used alone or in combination. The filtration method may involve passing the solution through the filter only once, but it is more preferable to circulate the solution and filter it multiple times. The filtration process can be performed in any order and any number of times in the polymer production process. However, it is preferable to filter the reaction solution after the polymerization reaction, the polymer solution, or both.

[0422] The (B) base polymer may be used singly or in combination of two or more different polymers with different composition ratios, Mw, and / or Mw / Mn. The (B) base polymer may also contain, in addition to the above-mentioned polymer, a hydrogenated ring-opening metathesis polymer, and the polymers described in JP-A-2003-66612 can be used.

[0423] [(C) Organic solvent] The chemically amplified resist composition of the present invention may contain an organic solvent as component (C). There are no particular limitations on the organic solvent (C) as long as it is capable of dissolving the components described above and below. 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; ketoalcohols 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 mono-tert-butyl ether acetate; lactones such as GBL; and mixed solvents thereof.

[0424] Among these organic solvents, 1-ethoxy-2-propanol, PGMEA, cyclohexanone, GBL, DAA, and mixed solvents thereof are preferred, as they have particularly excellent solubility for the base polymer of component (B).

[0425] In the chemically amplified resist composition of the present invention, the content of (C) organic solvent is preferably 200 to 5000 parts by mass, more preferably 400 to 3500 parts by mass, relative to 80 parts by mass of (B) base polymer. (C) The organic solvent may be used alone or in combination of two or more types.

[0426] [(D) Quencher] The chemically amplified resist composition of the present invention may contain a quencher as component (D). In this invention, the quencher is a material that traps the acid generated by the photoacid generator in the chemically amplified resist composition, thereby preventing it from diffusing to unexposed areas and forming a desired pattern.

[0427] (D) The quencher includes an onium salt represented by the following formula (2) or (3). [ka]

[0428] In formula (2), R q1 represents a hydrogen atom or a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom, but excludes those in which the hydrogen atom bonded to the carbon atom at the α-position of the sulfo group is substituted with a fluorine atom or a fluoroalkyl group. q2 is a hydrogen atom or a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom.

[0429] R q1 Specific examples of the hydrocarbyl group having 1 to 40 carbon atoms represented by the formula (I) include alkyl groups having 1 to 40 carbon atoms 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]. 2,6cyclic saturated hydrocarbyl groups having 3 to 40 carbon atoms, such as a decyl group or an adamantyl group; and aryl groups having 6 to 40 carbon atoms, such as a phenyl group, a naphthyl group or an anthracenyl group. Some or all of the hydrogen atoms in the hydrocarbyl groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms or halogen atoms, and some of the -CH2- groups in the hydrocarbyl groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms or nitrogen atoms, so that the hydrocarbyl groups may contain hydroxy groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, cyano groups, carbonyl groups, ether bonds, ester bonds, sulfonate ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic anhydrides (-C(=O)-OC(=O)-), haloalkyl groups, etc.

[0430] R q2 Specific examples of the hydrocarbyl group represented by R q1 In addition to the substituents exemplified as specific examples, examples include fluorinated saturated hydrocarbyl groups such as trifluoromethyl group and trifluoroethyl group, and fluorinated aryl groups such as pentafluorophenyl group and 4-trifluoromethylphenyl group.

[0431] Specific examples of the anion of the onium salt represented by formula (2) include, but are not limited to, those shown below. [ka]

[0432] [ka]

[0433] [ka]

[0434] [ka]

[0435] Specific examples of the anion of the onium salt represented by formula (3) include, but are not limited to, those shown below. [ka]

[0436] [ka]

[0437] [ka]

[0438] In equations (2) and (3), Mq + is an onium cation. The onium cation is preferably a sulfonium cation represented by the above formula (cation-1), an iodonium cation represented by the above formula (cation-2), or an ammonium cation represented by the following formula (cation-3). [ka]

[0439] In formula (cation-3), R ct6 ~R ct9 are each independently a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom. ct6 and R ct7 and may be bonded to each other to form a ring together with the nitrogen atom to which they are bonded. The hydrocarbyl group includes, in the explanation of formulas (cation-1) and (cation-2), R ct1 ~R ct5 Examples of the hydrocarbyl group represented by the formula (I) include the same as those exemplified above.

[0440] Specific examples of the ammonium cation represented by formula (cation-3) include, but are not limited to, those shown below. [ka]

[0441] Specific examples of the onium salts represented by formula (2) or (3) include any combination of the anions and cations described above. These onium salts can be easily prepared by ion exchange reactions using known organic chemistry methods. For information on ion exchange reactions, see, for example, JP 2007-145797 A.

[0442] The onium salt represented by formula (2) or (3) functions as a quencher in the chemically amplified resist composition of the present invention. This is because the counter anion of each onium salt is the conjugate base of a weak acid. The term "weak acid" as used herein refers to an acidity that is insufficient to deprotect the acid labile group in the acid labile group-containing unit 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 counter anion that is the conjugate base of a strong acid, such as a sulfonic acid fluorinated at the α-position. Specifically, when an onium salt that generates a strong acid, such as a sulfonic acid fluorinated at the α-position, is mixed with an onium salt that generates a weak acid, such as a non-fluorinated sulfonic acid or carboxylic acid, the strong acid generated from the photoacid generator upon irradiation with high-energy radiation collides with an onium salt having an unreacted weak acid anion, releasing the weak acid through salt exchange and generating an onium salt having a strong acid anion. In this process, the strong acid is exchanged for a weak acid with a lower catalytic activity, and the acid appears to be deactivated, allowing for control of acid diffusion.

[0443] Furthermore, as the (D) quencher, onium salts having a sulfonium cation and a phenoxide anion moiety in the same molecule as described in Japanese Patent No. 6848776, onium salts having a sulfonium cation and a carboxylate anion moiety in the same molecule as described in Japanese Patent No. 6583136 and JP-A-2020-200311, and onium salts having an iodonium cation and a carboxylate anion moiety in the same molecule as described in Japanese Patent No. 6274755 can also be used.

[0444] Here, when the photoacid generator that generates a strong acid is an onium salt, the strong acid generated by irradiation with high-energy rays can be exchanged for a weak acid as described above, but on the other hand, it is thought that the weak acid generated by irradiation with high-energy rays collides with the unreacted onium salt that generates the strong acid, making it difficult to carry out salt exchange. This is due to the phenomenon that the onium cation is more likely to form an ion pair with the anion of the strong acid.

[0445] When the chemically amplified resist composition of the present invention contains an onium salt represented by formula (2) or (3) as the quencher (D), the content thereof is preferably 0.1 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, relative to 80 parts by mass of the base polymer (B). It is preferable that the onium salt quencher of component (D) is within the above range, since 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.

[0446] The chemically amplified resist composition of the present invention may contain a nitrogen-containing compound as a quencher (D). Examples of the nitrogen-containing compound (D) include primary, secondary, or tertiary amine compounds described in paragraphs

[0146] to

[0164] of JP 2008-111103 A, particularly amine compounds having a hydroxy group, an ether bond, an ester bond, a lactone ring, a cyano group, or a sulfonate ester bond. Other examples include compounds in which a primary or secondary amine is protected with a carbamate group, such as the compounds described in JP 3790649 A.

[0447] Alternatively, a sulfonate sulfonium 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 by neutralizing with the acid generated by the compound itself, functioning as a so-called photodegradable base. The use of a photodegradable base can further enhance the contrast between the exposed and unexposed areas. For example, JP-A Nos. 2009-109595 and 2012-46501 can be used as references for the photodegradable base.

[0448] When the chemically amplified resist composition of the present invention contains a nitrogen-containing compound as a quencher (D), the content thereof is preferably 0.001 to 12 parts by mass, more preferably 0.01 to 8 parts by mass, relative to 80 parts by mass of the base polymer (B). The nitrogen-containing compound may be used alone or in combination of two or more types.

[0449] [(E) Other Photoacid Generators] The chemically amplified resist composition of the present invention may contain, as component (E), a photoacid generator other than component (A) (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 an acid upon exposure to high-energy rays. Suitable other photoacid generators include those represented by the following formula (4) or (5): [ka]

[0450] In formula (4), R 101 ~R 105 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 101 , R 102 and R 103 Any two of these may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. The hydrocarbyl group includes R ct1 ~R ct5Examples of the hydrocarbyl group represented by the formula (I) include the same as those exemplified above.

[0451] Specific examples of the cation of the sulfonium salt represented by formula (4) include the same as those exemplified as the sulfonium cation represented by formula (cation-1).Specific examples of the cation of the iodonium salt represented by formula (5) include the same as those exemplified as the iodonium cation represented by formula (cation-2).

[0452] In formulas (4) and (5), Xa - is an anion of a strong acid. Examples of the anion of a strong acid include those represented by any one of formulas (c1-1) to (c1-5).

[0453] Furthermore, as the other photoacid generator of the component (E), a compound represented by the following formula (6) is also preferred. [ka]

[0454] In formula (6), R 201 and R 202 R are each independently a hydrocarbyl group having 1 to 30 carbon atoms which may contain a heteroatom. 203 is a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom. 201 , R 202 and R 203 Any two of may be bonded to each other to form a ring together with the sulfur atom to which they are attached.

[0455] R 201 and R 202The hydrocarbyl group having 1 to 30 carbon atoms represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 30 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a tert-pentyl group, an n-pentyl group, an n-hexyl group, an n-octyl group, a 2-ethylhexyl group, an n-nonyl group, and an n-decyl group; a cyclopentyl group, a cyclohexyl group, a cyclopentylmethyl group, a cyclopentylethyl group, a cyclopentylbutyl group, a cyclohexylmethyl group, a cyclohexylethyl group, a cyclohexylbutyl group, a norbornyl group, an oxanorbornyl group, and a tricyclo[5.2.1.0] 2,6 cyclic saturated hydrocarbyl groups having 3 to 30 carbon atoms, such as a decyl group and an adamantyl group; aryl groups having 6 to 30 carbon atoms, such as a phenyl group, a methylphenyl group, an ethylphenyl group, an n-propylphenyl group, an isopropylphenyl group, an n-butylphenyl group, an isobutylphenyl group, a sec-butylphenyl group, a tert-butylphenyl group, a naphthyl group, a methylnaphthyl group, an ethylnaphthyl group, an n-propylnaphthyl group, an isopropylnaphthyl group, an n-butylnaphthyl group, an isobutylnaphthyl group, a sec-butylnaphthyl group, a tert-butylnaphthyl group and an anthracenyl group; and groups obtained by combining these groups. 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, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy 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 sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, or the like.

[0456] R 203The hydrocarbylene group having 1 to 30 carbon atoms represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkanediyl groups having 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, and heptadecane-1,17-diyl group; Examples of the alkylene groups include cyclic saturated hydrocarbylene groups having 3 to 30 carbon atoms, such as a cyclohexanediyl group, a norbornanediyl group, a cyclohexanediyl group, a norbornanediyl group, and an adamantanediyl group; and arylene groups, such as a phenylene group, a methylphenylene group, an ethylphenylene group, an n-propylphenylene group, an isopropylphenylene group, an n-butylphenylene group, an isobutylphenylene group, a sec-butylphenylene group, a tert-butylphenylene group, a naphthylene group, a methylnaphthylene group, an ethylnaphthylene group, an n-propylnaphthylene group, an isopropylnaphthylene group, an n-butylnaphthylene group, an isobutylnaphthylene group, a sec-butylnaphthylene group, and a tert-butylnaphthylene group. In addition, 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, a sulfur atom, a nitrogen atom, or a halogen atom, and some of the -CH- groups of the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom, resulting in the hydrocarbylene group containing a hydroxy 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 sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc. As the heteroatom, an oxygen atom is preferred.

[0457] In formula (6), L Ais a single bond, an ether bond, or a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. The hydrocarbylene group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R 203 Examples of the hydrocarbylene group represented by the formula (I) include the same as those exemplified above.

[0458] In formula (6), X a , X b , X c and X d are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, provided that X a , X b , X c and X d At least one of the groups is a fluorine atom or a trifluoromethyl group.

[0459] The photoacid generator represented by formula (6) is preferably one represented by the following formula (6'). [ka]

[0460] In formula (6'), L A is the same as above. X e is a hydrogen atom or a trifluoromethyl group, preferably a trifluoromethyl group. 301 , R 302 and R 303 are each independently a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (c1-1-1): fa1 Examples of the hydrocarbyl group include the same as those exemplified above. p and q each independently represent an integer of 0 to 5, and r represents an integer of 0 to 4.

[0461] Examples of the photoacid generator represented by formula (6) include the same compounds as those exemplified as the photoacid generator represented by formula (2) in JP-A-2017-26980.

[0462] Among the other photoacid generators, those containing anions represented by formula (c1-1-1) or (c1-4) are particularly preferred because of their small acid diffusion and excellent solubility in solvents. Also, those represented by formula (6') are particularly preferred because of their extremely small acid diffusion.

[0463] When the chemically amplified resist composition of the present invention contains (E) other photoacid generator, the content thereof is preferably 0.1 to 40 parts by mass, more preferably 0.5 to 20 parts by mass, per 80 parts by mass of (B) base polymer. When the amount of the photoacid generator (E) added is within the above range, the resolution is good and there is no risk of problems with foreign matter occurring after development of the resist film or during stripping, which is preferable. The (E) other photoacid generators may be used alone or in combination of two or more.

[0464] [(F) Surfactant] The chemically amplified resist composition of the present invention may further comprise a surfactant as component (F). The surfactant (F) is preferably a surfactant that is insoluble or slightly soluble in water but soluble in an alkaline developer, or a surfactant that is insoluble or slightly soluble in both water and an alkaline developer. Examples of such surfactants include those described in JP-A-2010-215608 and JP-A-2011-16746.

[0465] Among the surfactants described in the above publications, preferred surfactants that are insoluble or slightly soluble in water and alkaline developers include FC-4430 (manufactured by 3M), Surflon (registered trademark) S-381 (manufactured by AGC Seimi Chemical Co., Ltd.), Olfine (registered trademark) E1004 (manufactured by Nissin 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): [ka]

[0466] Here, R, Rf, A, B, C, m, and n apply only to formula (surf-1), regardless of the above descriptions. R is a divalent to tetravalent aliphatic group having 2 to 5 carbon atoms. Examples of the divalent aliphatic group include an ethylene group, a 1,4-butylene group, a 1,2-propylene group, a 2,2-dimethyl-1,3-propylene group, and a 1,5-pentylene group, and examples of the trivalent or tetravalent aliphatic group include the following: [ka] (In the formula, the dashed lines represent bonds and are partial structures derived from glycerol, trimethylolethane, trimethylolpropane, and pentaerythritol, respectively.)

[0467] Among these, a 1,4-butylene group, a 2,2-dimethyl-1,3-propylene group, and the like are preferred.

[0468] Rf is a trifluoromethyl group or a pentafluoroethyl group, preferably a trifluoromethyl group. m is an integer of 0 to 3, n is an integer of 1 to 4, and the sum of n and m is the valence of R, which is an integer of 2 to 4. A is 1. B is an integer of 2 to 25, preferably an integer of 4 to 20. C is an integer of 0 to 10, preferably 0 or 1. The order of the structural units in formula (surf-1) is not specified, and they may be bonded in blocks or randomly. The production of surfactants based on partially fluorinated oxetane ring-opening polymers is described in detail in the specification of U.S. Pat. No. 5,650,483, etc.

[0469] Surfactants that are insoluble or slightly soluble in water but 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 for suppressing the elution of water-soluble components from the resist film and reducing damage to the exposure equipment. They are also useful because they become soluble during alkaline aqueous development after exposure or post-exposure bake (PEB), making them less likely to become contaminants that cause defects. Such surfactants are insoluble or slightly soluble in water but soluble in alkaline developers. They are polymeric surfactants, also known as hydrophobic resins, and are particularly preferred because they have high water repellency and improve water slippage.

[0470] Specific examples of such polymer surfactants include those containing at least one repeating unit selected from those represented by any of the following formulae (7A) to (7E). [ka]

[0471] In formulas (7A) to (7E), R B is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1 is -CH2-, -CH2CH2-, -O- or two -H groups separated from each other. s1 are each 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 R are each independently a hydrogen atom, a hydrocarbyl group or a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, or an acid labile group. s3 When R is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be present between the carbon-carbon bonds. s4 is a hydrocarbon group or a fluorinated hydrocarbon group having 1 to 20 carbon atoms and a valence of (u+1). u is an integer of 1 to 3. R s5 are each independently a hydrogen atom or -C(=O)-ORsa R is a group represented by sa is a fluorinated hydrocarbyl group having 1 to 20 carbon atoms. s6 is a hydrocarbyl group or a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, and an ether bond or a carbonyl group may be present between the carbon-carbon bonds.

[0472] R s1 The hydrocarbyl group having 1 to 10 carbon atoms represented by the formula (I) is preferably a saturated hydrocarbyl group, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 10 carbon atoms, 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; and cyclic saturated hydrocarbyl groups having 3 to 10 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, adamantyl, and norbornyl. Of these, those having 1 to 6 carbon atoms are preferred.

[0473] R s2 The hydrocarbylene group represented by the formula (I) is preferably a saturated hydrocarbylene group, which may be linear, branched, or cyclic. Specific examples thereof include a methylene group, an ethylene group, a propylene group, a butylene group, and a pentylene group.

[0474] R s3 or R s6 The hydrocarbyl group represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include saturated hydrocarbyl groups, and aliphatic unsaturated hydrocarbyl groups such as alkenyl groups and alkynyl groups, with saturated hydrocarbyl groups being preferred. As the saturated hydrocarbyl group, R s1 In addition to the examples of the hydrocarbyl group represented by the formula (R), examples include an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, and a pentadecyl group. s3 or R s6Examples of the fluorinated hydrocarbyl group represented by the formula (I) include groups in which some or all of the hydrogen atoms bonded to the carbon atoms of the aforementioned hydrocarbyl group have been substituted with fluorine atoms. As mentioned above, an ether bond or a carbonyl group may be present between these carbon-carbon bonds.

[0475] R s3 Specific examples of the acid labile group represented by the formula (AL-3) to (AL-5) include the groups represented by the formulas (AL-3) to (AL-5) above, trialkylsilyl groups in which each alkyl group has 1 to 6 carbon atoms, and oxo group-containing alkyl groups having 4 to 20 carbon atoms.

[0476] R s4 The (u+1)-valent hydrocarbon group or fluorinated hydrocarbon group represented by the formula (I) may be linear, branched, or cyclic, and specific examples thereof include groups obtained by further eliminating u hydrogen atoms from the aforementioned hydrocarbyl group or fluorinated hydrocarbyl group.

[0477] R sa The fluorinated hydrocarbyl group represented by the formula (I) is preferably saturated and may be linear, branched or cyclic. Specific examples thereof include those in which some or all of the hydrogen atoms of the hydrocarbyl groups have been substituted with fluorine atoms, and specific examples thereof include a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a 3,3,3-trifluoro-1-propyl group, a 3,3,3-trifluoro-2-propyl group, a 2,2,3,3-tetrafluoropropyl group, a 1,1,1,3,3,3-hexafluoroisopropyl group, a 2,2,3,3,4,4,4-heptafluorobutyl group, a 2,2,3,3,4,4,5,5-octafluoropentyl group, a 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl group, a 2-(perfluorobutyl)ethyl group, a 2-(perfluorohexyl)ethyl group, a 2-(perfluorooctyl)ethyl group, and a 2-(perfluorodecyl)ethyl group.

[0478] Specific examples of the repeating unit represented by any one of formulas (7A) to (7E) include, but are not limited to, the following: B is the same as above. [ka]

[0479] [ka]

[0480] [ka]

[0481] [ka]

[0482] [ka]

[0483] [ka]

[0484] The polymer surfactant may further contain other repeating units in addition to the repeating units represented by formulae (7A) to (7E). Examples of such other repeating units include repeating units obtained from methacrylic acid and α-trifluoromethylacrylic acid derivatives. In the polymer surfactant, the content of the repeating units represented by formulae (7A) to (7E) is preferably 20 mol % or more, more preferably 60 mol % or more, and even more preferably 100 mol %, of all repeating units.

[0485] The Mw of the polymer surfactant is preferably from 1,000 to 500,000, and more preferably from 3,000 to 100,000. The Mw / Mn is preferably from 1.0 to 2.0, and more preferably from 1.0 to 1.6.

[0486] The polymer surfactant can be synthesized by heating a monomer containing an unsaturated bond that provides the repeating units represented by formulas (7A) to (7E) and, if necessary, other repeating units, in an organic solvent with the addition of a radical initiator to polymerize the monomer. Examples of organic solvents used in 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 labile group introduced into the monomer may be used as is, or may be protected or partially protected after polymerization.

[0487] When synthesizing the polymer surfactant, a known chain transfer agent such as dodecyl mercaptan or 2-mercaptoethanol may be used to adjust the molecular weight. In this case, the amount of the chain transfer agent added is preferably 0.01 to 10 mol % based on the total number of moles of the monomers to be polymerized.

[0488] When the chemically amplified resist composition of the present invention contains a surfactant (F), the content thereof is preferably 0.1 to 50 parts by mass, more preferably 0.5 to 10 parts by mass, per 80 parts by mass of the base polymer (B). When the surfactant (F) content is 0.1 part by mass or more, the receding contact angle between the resist film surface and water is sufficiently improved, while when the surfactant content is 50 parts by mass or less, the dissolution rate of the resist film surface in the developer is low, 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.

[0489] [(G) Other ingredients] The chemically amplified resist composition of the present invention may contain, as other components (G), a compound that decomposes in the presence of acid to generate acid (acid amplifying compound), an organic acid derivative, a fluorine-substituted alcohol, or a compound with a Mw of 3000 or less whose solubility in a developer changes upon the action of acid (dissolution inhibitor). Examples of the acid amplifying compound include the compounds described in JP-A-2009-269953 and JP-A-2010-215608. When the acid amplifying compound is contained, its content is preferably 0 to 5 parts by mass, more preferably 0 to 3 parts by mass, relative to 80 parts by mass of the (B) base polymer. If the content is too high, it may be difficult to control acid diffusion, resulting in degradation of resolution and pattern shape. Examples of the organic acid derivative, fluorine-substituted alcohol, and dissolution inhibitor include the compounds described in JP-A-2009-269953 and JP-A-2010-215608.

[0490] [Pattern formation method] The pattern forming method of the present invention includes the steps of forming a resist film on a substrate using the aforementioned chemically amplified resist composition, exposing the resist film to high-energy rays, and developing the exposed resist film using a developer.

[0491] The substrate may be, for example, a substrate for integrated circuit manufacturing (Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic anti-reflective coating, etc.) or a substrate for mask circuit manufacturing (Cr, CrO, CrON, MoSi2, SiO2, etc.).

[0492] The resist film can be formed, for example, by applying the chemically amplified resist composition onto a substrate by a method such as spin coating so that the film thickness is preferably 0.05 to 2 μm, and then pre-baking the composition on a hot plate preferably at 60 to 150°C for 1 to 10 minutes, more preferably at 80 to 140°C for 1 to 5 minutes.

[0493] Examples of high-energy rays used to expose the resist film include KrF excimer laser light, ArF excimer laser light, EB, and EUV with a wavelength of 3 to 15 nm. When KrF excimer laser light, ArF excimer laser light, or EUV is used for exposure, a mask for forming a desired pattern is used, and the exposure dose is preferably 1 to 200 mJ / cm. 2 , more preferably 10 to 100 mJ / cm 2 When EB is used, the exposure dose is preferably 1 to 300 μC / cm 2 , either directly or through a mask for forming a desired pattern. 2 , more preferably 10 to 200 μC / cm 2 Irradiate so that

[0494] In addition to the usual exposure method, the immersion method can also be used, in which a liquid with a refractive index of 1.0 or higher is placed between the resist film and the projection lens. In this case, a water-insoluble protective film can also be used.

[0495] The water-insoluble protective film is used to prevent elution from the resist film and increase the water sliding property of the film surface. It can be broadly divided into two types. One is an organic solvent-removable type that requires stripping before alkaline aqueous development using an organic solvent that does not dissolve the resist film. The other is an alkaline aqueous solution-soluble type that is soluble in alkaline developer and removes the protective film along with removing the soluble portion of the resist film. The latter is particularly based on a polymer containing 1,1,1,3,3,3-hexafluoro-2-propanol residues that is insoluble in water but soluble in alkaline developer, and is preferably dissolved in an alcohol solvent with 4 or more carbon atoms, an ether solvent with 8 to 12 carbon atoms, or a mixed solvent thereof. Materials can also be prepared by dissolving the water-insoluble, alkaline developer-soluble surfactant described above in an alcohol solvent with 4 or more carbon atoms, an ether solvent with 8 to 12 carbon atoms, or a mixed solvent thereof.

[0496] After the exposure, PEB may be performed by heating on a hot plate, for example, preferably at 60 to 150° C. for 1 to 5 minutes, more preferably at 80 to 140° C. for 1 to 3 minutes.

[0497] The development is carried out using a developer, for example, an alkaline aqueous solution of tetramethylammonium hydroxide (TMAH) or the like, preferably at 0.1 to 5 mass %, more preferably 2 to 3 mass %, for preferably 0.1 to 3 minutes, more preferably 0.5 to 2 minutes, by a conventional method such as dipping, puddling, or spraying, whereby the exposed areas are dissolved and the desired pattern is formed on the substrate.

[0498] After forming the resist film, the resist film may be rinsed with pure water to extract the acid generator and the like from the film surface or to wash away particles, or the resist film may be rinsed after exposure to remove water remaining on the film.

[0499] Furthermore, the pattern may be formed by a double patterning method, such as a trench method in which a first exposure and etching process is performed to process an underlayer with a 1:3 trench pattern, and then a second exposure process is performed with a shifted position to form a 1:3 trench pattern, thereby forming a 1:1 pattern, or a line method in which a first underlayer with a 1:3 isolated leave pattern is processed by a first exposure and etching process, and then a second exposure process is performed with a shifted position to process a second underlayer with a 1:3 isolated leave pattern formed below the first underlayer, thereby forming a 1:1 pattern with half the pitch.

[0500] In the pattern forming method of the present invention, a negative tone development method may be used in which an organic solvent is used as a developer instead of the alkaline aqueous solution to dissolve the unexposed areas.

[0501] The organic solvent development may be carried out using, 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 crotonate, ethyl crotonate, propyl cyclohexanone ... Examples of organic solvents that can be used include methyl propionate, ethyl propionate, ethyl 3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, pentyl lactate, isopentyl lactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, phenyl acetate, benzyl acetate, methyl phenylacetate, ethyl phenylacetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, and 2-phenylethyl acetate. These organic solvents may be used alone or in combination of two or more. [Example]

[0502] The present invention will be specifically explained below by showing synthesis examples, examples, and comparative examples, but the present invention is not limited to the following examples. The apparatuses used are as follows. IR: Thermo Fisher Scientific NICOLET 6700 · 1 H-NMR: ECA-500 manufactured by JEOL Ltd. MALDI TOF-MS: JEOL S3000

[0503] [1] Synthesis of onium salts [Example 1-1] Synthesis of onium salt PAG-1 [ka]

[0504] (1) Synthesis of intermediate In-1 Under a nitrogen atmosphere, raw materials SM-1 (6.3 g), SM-2 (10.4 g), DMAP (0.3 g), and methylene chloride (50 g) were added to a reaction vessel and cooled in an ice bath. While maintaining the temperature inside the reaction vessel at 20°C or below, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (5.8 g) was added as a powder. After the addition, the mixture was warmed to room temperature and aged for 12 hours. After aging, water was added to quench the reaction, and the mixture was subjected to a standard aqueous work-up. The solvent was then distilled off, and the residue was washed with diisopropyl ether to obtain 14.4 g of intermediate In-1 as an oil (yield 92%).

[0505] (2) Synthesis of PAG-1 Under a nitrogen atmosphere, intermediate In-1 (14.4 g), raw material SM-3 (7.8 g), methylene chloride (50 g), and water (30 g) were added, stirred for 15 minutes, and the organic layer was separated, washed with water, and then concentrated under reduced pressure. Methyl isobutyl ketone (50 g) was added to the concentrated solution, followed by azeotropic dehydration. Diisopropyl ether was added to the concentrate, and crystallization was carried out to obtain 16.0 g of the target product, PAG-1, as white crystals (yield 92%).

[0506] The IR spectrum data and TOF-MS results of PAG-1 are shown below. 1 The results of H-NMR / DMSO-d6) are shown in Figure 1. IR(D-ATR): ν= 3484, 3065, 3024, 2972, 1779, 1641, 1593, 1583, 1479, 1467, 1443, 1379, 1324, 1272, 1229, 1170, 1123, 1091, 1047, 999, 986, 917, 886, 847, 816, 763, 706, 681, 631, 596, 535, 487 cm -1 . MALDI TOF-MS: POSITIVE M + 277(C 18 H 13 OS + equivalent) NEGATIVE M - 477(C23 H 13 F4O5S - equivalent)

[0507] [Examples 1-2 to 1-9] Synthesis of onium salts PAG-2 to PAG-9 Onium salts PAG-2 to PAG-9 represented by the following formulae were synthesized using the corresponding raw materials and known organic synthesis reactions. [ka]

[0508] [ka]

[0509] [2] Synthesis of base polymer [Synthesis example] Synthesis of base polymers (P-1 to P-5) Each monomer was combined and copolymerized in MEK, the solvent, and the reaction solution was poured into hexane. The precipitated solid was washed with hexane, isolated, and dried to obtain base polymers (P-1 to P-5) with the following compositions. The resulting base polymers were 1 Mw and Mw / Mn were confirmed by H-NMR and GPC (solvent: THF, standard: polystyrene). [ka]

[0510] [ka]

[0511] [3] Preparation of chemically amplified resist composition [Examples 2-1 to 2-30, Comparative Examples 1-1 to 1-20] Photoacid generators (PAG-1 to PAG-9) composed of onium salts of the present invention, comparative photoacid generators (PAG-A to PAG-E), other photoacid generators (PAG-X, PAG-Y), base polymers (P-1 to P-5), and quenchers (Q-1 to Q-4) were dissolved in a solvent containing 0.01 mass% of surfactant A (Omnova) in the compositions shown in Tables 1 and 2 below to prepare solutions. The solutions were then filtered through a 0.2 μm Teflon (registered trademark) filter to prepare chemically amplified resist compositions (R-1 to R-30 and CR-1 to CR-20).

[0512] [Table 1]

[0513] [Table 2]

[0514] In Tables 1 and 2, the solvents, other photoacid generators PAG-X and 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)

[0515] Other photoacid generators: PAG-X, PAG-Y [ka]

[0516] Photoacid generators for comparison: PAG-A to PAG-E [ka]

[0517] Quencher: Q-1~Q-4 [ka]

[0518] Surfactant A: 3-methyl-3-(2,2,2-trifluoroethoxymethyl)oxetane-tetrahydrofuran-2,2-dimethyl-1,3-propanediol copolymer (Omnova) [ka] a:(b+b'):(c+c')=1:4-7:0.01-1 (molar ratio) Mw=1500

[0519] [4] EUV Lithography Evaluation (1) [Examples 3-1 to 3-30, Comparative Examples 2-1 to 2-20] Each chemically amplified resist composition (R-1 to R-30, CR-1 to CR-20) shown in Tables 1 to 3 was spin-coated onto a Si substrate on which a 20-nm-thick silicon-containing spin-on hard mask SHB-A940 (43% silicon by mass) manufactured by Shin-Etsu Chemical Co., Ltd. had been formed, and the substrate was pre-baked at 100°C for 60 seconds using a hot plate to produce a 50-nm-thick resist film. The resist film was exposed to an LS pattern with an on-wafer dimension of 18 nm and a pitch of 36 nm using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9 / 0.6, dipole illumination) while varying the exposure dose and focus (exposure dose pitch: 1 mJ / cm). 2 After exposure, PEB was performed for 60 seconds at the temperatures shown in Tables 4 and 5. Thereafter, puddle development was performed with a 2.38 mass % TMAH aqueous solution for 30 seconds, followed by rinsing with a surfactant-containing rinse material and spin drying to obtain a positive pattern. The obtained LS pattern was observed with a critical dimension SEM (CG6300) manufactured by Hitachi High-Technologies Corporation, and the sensitivity, EL, LWR, depth of focus (DOF), and tilt limit were evaluated according to the following methods. The results are shown in Tables 3 and 4.

[0520] [Sensitivity evaluation] The optimum exposure dose Eop (mJ / cm) to obtain an LS pattern with a line width of 18 nm and a pitch of 36 nm 2The smaller this value, the higher the sensitivity.

[0521] [EL Evaluation] EL (unit: %) was calculated from the exposure amount formed within a range of ±10% (16.2 to 19.8 nm) of the 18 nm space width in the LS pattern using the following formula: The larger this value, the better the performance. EL(%)=(|E1-E2| / Eop)×100 E1: Optimal exposure dose for LS pattern with line width of 16.2 nm and pitch of 36 nm E2: Optimal exposure dose for LS pattern with line width of 19.8 nm and pitch of 36 nm Eop: Optimal exposure dose for LS pattern with line width of 18nm and pitch of 36nm

[0522] [LWR rating] The LS pattern obtained by irradiation with Eop was measured at 10 points along the line length, and the LWR was calculated as three times the standard deviation (σ) (3σ). The smaller this value, the less roughness and the more uniform the line width pattern obtained.

[0523] [DOF evaluation] For the evaluation of the depth of focus, the focus range formed within a range of ±10% (16.2 to 19.8 nm) of the 18 nm dimension of the LS pattern was determined. The larger this value, the wider the depth of focus.

[0524] [Line pattern collapse limit evaluation] The line dimension of the LS pattern at each exposure dose at the optimum focus was measured at 10 points in 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.

[0525] [Table 3]

[0526] [Table 4]

[0527] The results shown in Tables 3 and 4 demonstrate that the chemically amplified resist composition of the present invention, which contains a photoacid generator consisting of an onium salt, exhibits good sensitivity and excellent EL, LWR, and DOF. Furthermore, the collapse limit value was small, demonstrating resistance to pattern collapse 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.

[0528] [5] EUV Lithography Evaluation (2) [Examples 4-1 to 4-30, Comparative Examples 3-1 to 3-20] Each chemically amplified resist composition (R-1 to R-30, CR-1 to CR-20) listed in Tables 1 to 3 was spin-coated onto a 20 nm thick silicon spin-on hard mask (SHB-A940, manufactured by Shin-Etsu Chemical Co., Ltd.) containing 43% silicon by weight. The resist was then pre-baked at 105°C for 60 seconds using a hot plate to produce a 50 nm thick resist film. The resist film was exposed to light using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9 / 0.6, quadruple-pole illumination, 46 nm pitch on the wafer, and a hole pattern mask with a +20% bias). The resist film was then subjected to PEB for 60 seconds using a hot plate at the temperatures listed in Tables 7 and 8, followed by development for 30 seconds in a 2.38% by weight aqueous TMAH solution to produce a 23 nm hole pattern. Using a critical dimension SEM (CG6300) manufactured by Hitachi High-Technologies Corporation, the exposure dose when a hole dimension of 23 nm was formed was measured and used as the sensitivity. The dimensions of 50 holes were also measured, and the CDU was calculated by multiplying the standard deviation (σ) by three (3σ). The results are shown in Tables 5 and 6.

[0529] [Table 5]

[0530] [Table 6]

[0531] The results shown in Tables 5 and 6 confirm that the chemically amplified resist composition containing a photoacid generator made of an onium salt of the present invention has good sensitivity and excellent CDU.

Claims

1. An onium salt represented by the following formula (1): 【Chemical 1】 [In the formula, R 1 ~R 12 are each independently a hydrogen atom, a halogen atom, or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. R 13 and R 14 One of the groups is a group having a partial structure represented by the following formula (1a), and the other is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a hydrogen atom, a halogen atom, or a heteroatom. Also, R 1 ~R 14 At least two of may be bonded to each other to form a ring together with the carbon atoms to which they are bonded, or together with the carbon atoms to which they are bonded and the carbon atoms therebetween. Z + is an onium cation. 【Chemistry 2】 (In the formula, m1 is 0 or 1. When m1 is 0, m2 is an integer of 0 to 4, and when m1 is 1, m2 is an integer of 0 to 6. When m1 is 0, m3 is an integer of 0 to 3, and when m1 is 1, m3 is an integer of 0 to 5. However, when m1 is 0, m2+m3 is 0 to 4, and when m1 is 1, m2+m3 is 0 to 6. R F is a fluorine atom, a fluorinated alkyl group having 1 to 6 carbon atoms, a fluorinated alkoxy group having 1 to 6 carbon atoms, or a fluorinated alkylthio group having 1 to 6 carbon atoms. R 15 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, and when m3 is 2 or more, a plurality of R 15 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. L A and L B are each independently a single bond, an ether bond, an ester bond, an amide bond, a sulfonate ester bond, a sulfonamide bond, a carbonate bond or a carbamate bond. X L represents a single bond or a hydrocarbylene group having 1 to 40 carbon atoms which may contain a heteroatom.

2. The onium salt according to claim 1, which is represented by the following formula (1A): 【Chemistry 3】 (In the formula, R 1 ~R 13 , R 15 , L A , X L , R F , m1 to m3 and Z + is the same as above.)

3. The onium salt according to claim 2, which is represented by the following formula (1B): 【Chemistry 4】 (In the formula, R 5 , R 10 ~R 13 , R 15 , L A , X L , R F , m1 to m3 and Z + is the same as above. m4 and m5 each independently represent an integer of 0 to 4. R 16 and R 17 are each independently a hydrogen atom, a halogen atom, or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 16 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded, or together with the carbon atoms to which they are bonded and the carbon atoms therebetween, and when m5 is 2 or more, a plurality of R 17 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded, or together with the carbon atoms to which they are bonded and the carbon atoms therebetween.)

4. The onium salt according to claim 3, which is represented by the following formula (1C): 【Chemistry 5】 (In the formula, R 5 , R 10 ~R 13 , R 16 , R 17 , L A , X L , m4, m5 and Z + is the same as above.)

5. Z + is a sulfonium cation represented by the following formula (cation-1) or an iodonium cation represented by the following formula (cation-2): 【Chemistry 6】 (In the formula, R ct1 ~R ct5 are each independently a halogen atom or a hydrocarbyl group having 1 to 30 carbon atoms which may contain a heteroatom. ct1 and R ct2 may be bonded to each other to form a ring together with the sulfur atom to which they are attached.)

6. A photoacid generator comprising the onium salt according to any one of claims 1 to 5.

7. A chemically amplified resist composition comprising the photoacid generator according to claim 6.

8. 8. The chemically amplified resist composition according to claim 7, which comprises a base polymer containing a repeating unit represented by the following formula (a1): 【Chemistry 7】 (In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X 1 represents 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 halogen atom or an alkoxy group having 1 to 10 carbon atoms which may contain a fluorine atom. 11 is a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring. * represents a bond to a carbon atom in the main chain. AL 1 is an acid labile group.

9. 9. The chemically amplified resist composition according to claim 8, wherein the base polymer contains a repeating unit represented by the following formula (a2): 【Chemistry 8】 (In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X 2 is a single bond or *-C(=O)-O-. * represents a bond to a carbon atom in the main chain. R 21 represents a halogen atom, a cyano group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbyloxycarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom. AL 2 is an acid labile group. a is an integer from 0 to 4.

10. 9. The chemically amplified resist composition according to claim 8, wherein the base polymer contains a repeating unit represented by the following formula (b1) or (b2): 【Chemistry 9】 (In the formula, R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y 1 is a single bond or *-C(=O)-O-. * represents a bond to a carbon atom in the main chain. R 31 is a group having 1 to 20 carbon atoms and containing at least one structure selected from a hydrogen atom, a hydroxy group other than a phenolic hydroxy group, a cyano group, a carbonyl group, a carboxy group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, and a carboxylic acid anhydride (-C(=O)-O-C(=O)-). R 32 represents a halogen atom, a hydroxy group, a nitro group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbyloxycarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom. b is an integer from 1 to 4, and c is an integer from 0 to 4, provided that 1≦b+c≦5.

11. 9. The chemically amplified resist composition according to claim 8, wherein the base polymer comprises at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (c1), a repeating unit represented by the following formula (c2), a repeating unit represented by the following formula (c3), and a repeating unit represented by the following formula (c4): 【Chemistry 10】 (In the formula, R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Z 1 is a single bond or a phenylene group. Z 2 is *-C(=O)-O-Z 21 -, *-C(=O)-NH-Z 21 - or *-O-Z 21 - is. Z 21 is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, or a divalent group obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Z 3 are each independently a single bond, a phenylene group, a naphthylene group, or *-C(=O)-O-Z 31 - is. Z 31 is an aliphatic hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the aliphatic hydrocarbylene group may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring. Z 4 each independently represents a single bond, **-Z 41 -C(=O)-O-, **-C(=O)-NH-Z 41 - or **-O-Z 41 - is. is. Z 41 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Z 5 are each independently a single bond, *-Z 51 -C(=O)-O-, *-C(=O)-NH-Z 51 - or *-O-Z 51 - is. Z 51 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Z 6 represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, *-C(=O)-O-Z 61 -, *-C(=O)-N(H)-Z 61 - or *-O-Z 61 - is. Z 61 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, or a phenylene group substituted with a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. * represents a bond to a carbon atom in the main chain. ** represents Z 3 Represents a bond with . R 41 and R 42 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 41 and R 42 may be bonded to each other to form a ring together with the sulfur atom to which they are attached. L 1 is a single bond, an ether bond, an ester bond, a carbonyl group, a sulfonate ester bond, a carbonate bond or a carbamate bond. Rf 1 and Rf 2 are each independently a fluorine atom or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Rf 3 and Rf 4 are each independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Rf 5 and Rf 6 are each independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. 5 and Rf 6 cannot simultaneously become a hydrogen atom. M - is a non-nucleophilic counterion. A + is an onium cation. d is an integer from 0 to 3.

12. 8. The chemically amplified resist composition according to claim 7, further comprising an organic solvent.

13. 8. The chemically amplified resist composition according to claim 7, further comprising a quencher.

14. 8. The chemically amplified resist composition according to claim 7, further comprising a photoacid generator other than the photoacid generator according to claim 6.

15. 8. The chemically amplified resist composition according to claim 7, further comprising a surfactant.

16. A pattern forming method comprising the steps of: forming a resist film on a substrate using the chemically amplified resist composition according to claim 7; exposing the resist film to high-energy rays; and developing the exposed resist film using a developer.

17. 17. The pattern forming method according to claim 16, wherein the high-energy beam is a KrF excimer laser beam, an ArF excimer laser beam, an electron beam, or extreme ultraviolet light having a wavelength of 3 to 15 nm.

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