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JP-2026076056-A - Sulfonium salt, chemically amplified resist composition, and patterning method

JP2026076056AJP 2026076056 AJP2026076056 AJP 2026076056AJP-2026076056-A

Abstract

[Problem] To provide an onium salt used in a chemically amplified resist composition that exhibits excellent solvent solubility, high sensitivity, high contrast, and superior lithography performance such as LWR, CDU, MEF, EL, DOF, etc., in photolithography using high-energy rays; a chemically amplified resist composition containing the onium salt as a photoacid generator; and a pattern formation method using the chemically amplified resist composition. [Solution] A sulfonium salt comprising an aromatic sulfonate anion and a sulfonium cation represented by the following formula (1B). [Selection Diagram] None

Inventors

  • 福島 将大

Assignees

  • 信越化学工業株式会社

Dates

Publication Date
20260511
Application Date
20241023

Claims (16)

  1. A sulfonium salt comprising an aromatic sulfonate anion represented by the following formula (1A) and a sulfonium cation represented by the following formula (1B). (In the formula, m1 is 0 or 1. m2 is 0, 1, 2, 3 or 4. m3 is 0, 1, 2, 3 or 4, where 0 ≤ m2 + m3 ≤ 4 when m1 is 0, and 0 ≤ m2 + m3 ≤ 6 when m1 is 1. m4 is 0 or 1.) W is a 6-40 carbon atom hydrocarbyl group containing at least one aromatic ring, and the hydrocarbyl group may contain a heteroatom. R F1 is a fluorine atom, a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms, a fluorinated saturated hydrocarbyloxy group having 1 to 6 carbon atoms, or a fluorinated saturated hydrocarbylthio group having 1 to 6 carbon atoms. When m2 is 2, 3, or 4, each R F1 may be the same as or different from one another. R1 is a halogen atom other than fluorine, a nitro group, a C1-C20 hydrocarbyl group which may contain a heteroatom, a C1-C20 hydrocarbyloxy group which may contain a heteroatom, or a C1-C20 hydrocarbylthio group which may contain a heteroatom. When m3 is 2, 3, or 4, each R1 may be the same or different from each other, and multiple R1s may bond to each other to form a ring with the carbon atoms to which they are bonded. LA and LB are, independently, a single bond, an ether bond, an ester bond, a sulfonic acid ester bond, an amide bond, a sulfonamide bond, a carbonate bond, or a carbamate bond. X L is a hydroxylene group having 1 to 40 carbon atoms, which may contain single bonds or heteroatoms. (In the formula, n1 is 0 or 1. n2 is 0, 1 or 2. n3 is 0, 1 or 2. n4 is 0, 1 or 2. However, when n1 is 0, 0 ≤ n2 + n3 + n4 ≤ 5, and when n1 is 1, 0 ≤ n2 + n3 + n4 ≤ 7. n5 is 0 or 1. n6 is 0, 1 or 2. n7 is 0, 1 or 2. n8 is 0, 1 or 2. However, when n5 is 0, 0 ≤ n6 + n7 + n8 ≤ 5, and when n5 is 1, then 0 ≤ n6 + n7 + n8 ≤ 7. n9 is 0 or 1. n10 is 0, 1 or 2. n11 is 0, 1 or 2. n12 is 0, 1 or 2. However, when n9 is 0, then 0 ≤ n10 + n11 + n12 ≤ 5, and when n9 is 1, then 0 ≤ n10 + n11 + n12 ≤ 7. Also, 1 ≤ n2 + n6 + n10 ≤ 6, and 1 ≤ n3 + n7 + n11 ≤ 6. R11 , R12 , and R13 are each independently a hydrocarbyl group having 1 to 20 carbon atoms, which may contain heteroatoms. When n3 is 2, each R11 may be the same as or different from the others. When n7 is 2, each R12 may be the same as or different from the others. When n11 is 2, each R13 may be the same as or different from the others. R14 , R15 , and R16 are each independently a halogen atom, a nitro group, a hydroxyl group, a carboxyl group, a C1-C20 hydrocarbyl group which may contain a heteroatom, a C1-C20 hydrocarbyloxy group which may contain a heteroatom, or a C1-C20 hydrocarbylthio group which may contain a heteroatom. When n4 is 2, each R14 may be the same or different from each other, and two R14s may bond to each other to form a ring with the carbon atoms to which they are bonded. When n8 is 2, each R15 may be the same or different from each other, and two R15s may bond to each other to form a ring with the carbon atoms to which they are bonded. When n12 is 2, each R16 may be the same or different from each other, and two R16s may bond to each other to form a ring with the carbon atoms to which they are bonded. Furthermore, two of the three aromatic rings bonded to S + may bond to each other, forming a ring with the sulfur atom to which they are bonded.
  2. The sulfonium salt according to claim 1, wherein W is represented by the following formula (W-1) or (W-2). (In the formula, m5 is 0 or 1. m6 is 0, 1, 2, 3 or 4. m7 is 1, 2, 3 or 4. m8 is 0 or 1. m9 is 0 or 1. m10 is 0, 1, 2, 3 or 4. m11 is 0, 1, 2, 3 or 4.) R2 is a hydrocarbyl group having 1 to 20 carbon atoms, which may each independently contain a hydrogen atom, a halogen atom other than an iodine atom, or a heteroatom. R3 and R4 are each independently a C1-C20 hydrocarbyl group which may contain a hydrogen atom, a halogen atom, or a heteroatom. R5 to R9 are each independently a hydrocarbyl group having 1 to 40 carbon atoms, which may contain a hydrogen atom, a halogen atom, or a heteroatom. The dashed line represents a connection with LA .
  3. The sulfonium salt according to claim 1, wherein the anion is represented by the following formula (1A-1). (In the formula, m1 to m4, W, R F1 , R 1 , and L A are the same as described above.)
  4. The sulfonium salt according to claim 1, wherein the cation is represented by the following formula (1B-1). (In the formula, n2 to n4, n6 to n8, n10 to n12 and R 11 to R 16 are the same as described above.)
  5. A photoacid generator comprising a sulfonium salt according to any one of claims 1 to 4.
  6. A chemically amplified resist composition comprising the photoacid generator described in claim 5.
  7. Furthermore, the chemically amplified resist composition according to claim 6, comprising a base polymer containing a polymer having repeating units represented by the following formula (a1) or (a2). (In the formula, R A is independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.) X1 is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-O- X11- , and the phenylene group or naphthylene group may be substituted with a hydroxyl group, a nitro group, a cyano group, a saturated hydrocarbyl group having 1 to 10 carbon atoms which may contain a fluorine atom, a saturated hydrocarbyloxy group having 1 to 10 carbon atoms which may contain a fluorine atom, or a halogen atom. X11 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 hydroxyl group, an ether bond, an ester bond, or a lactone ring. X² is either a single bond or *-C(=O)-O-. * represents a bond with a carbon atom in the main chain. R 21 is a halogen atom, a cyano group, a hydroxyl group, a nitro group, a C1-C20 hydrocarbyl group which may contain a heteroatom, a C1-C20 hydrocarbyloxy group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyl group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyloxy group which may contain a heteroatom, or a C2-C20 hydrocarbyloxycarbonyl group which may contain a heteroatom. When a1 is 2, 3, or 4, each R 21 may be the same as or different from one another. AL1 and AL2 are, independently, acid-unstable groups. a1 is 0, 1, 2, 3, or 4.
  8. The chemically amplified resist composition according to claim 7, wherein the polymer comprises repeating units represented by the following formula (a3). (In the formula, b1 is 0 or 1. When b1 is 0, b2 is 0, 1, 2 or 3, and when b1 is 1, b2 is 0, 1, 2, 3, 4 or 5.) RA is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X3 is a single bond, *-C(=O)-O- or *-C(=O)-NH-. * represents a bond with a carbon atom in the main chain. X4 is a single bond, an aliphatic hydrocarbylene group having 1 to 4 carbon atoms, a carbonyl group, a sulfonyl group, or a group obtained by combining these. X5 and X6 are, independently, either an oxygen atom or a sulfur atom, except that X4 and X6 are bonded to adjacent carbon atoms in the aromatic ring. R22 and R23 are each independently a hydrocarbyl group having 1 to 20 carbon atoms, which may contain a hydrogen atom or a heteroatom. Furthermore, R22 and R23 may bond to each other to form a ring with the carbon atoms to which they are bonded. R 24 is a halogen atom, a hydroxyl group, a cyano group, a nitro group, a C1-C20 hydrocarbyl group which may contain a heteroatom, a C1-C20 hydrocarbyloxy group which may contain a heteroatom, a C2-C20 hydrocarbyloxycarbonyl group which may contain a heteroatom, a C1-C20 hydrocarbylthio group which may contain a heteroatom, or -N(R 24A )(R 24B ). R 24A and R 24B are each independently a hydrogen atom or a C1-C6 hydrocarbyl group. When b2 is 2 or more, each R 24 may be the same or different from each other, and multiple R 24s may bond to each other to form a ring with the carbon atoms of the aromatic ring to which they are bonded.
  9. The chemically amplified resist composition according to claim 7, wherein the polymer comprises repeating units represented by the following formula (b1) or (b2). (In the formula, R A is independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.) Y1 is either a single bond or an *-C(=O)-O- bond. * represents a bond with a carbon atom in the main chain. R 31 is a group having 1 to 20 carbon atoms that includes a hydrogen atom or at least one structure selected from a hydroxyl group other than a phenolic hydroxyl group, a cyano group, a carbonyl group, a carboxyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, and a carboxylic acid anhydride (-C(=O)-O-C(=O)-). R 32 is a halogen atom, a carboxyl group, a nitro group, a cyano group, a C1-C20 hydrocarbyl group which may contain a heteroatom, a C1-C20 hydrocarbyloxy group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyl group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyloxy group which may contain a heteroatom, or a C2-C20 hydrocarbyloxycarbonyl group which may contain a heteroatom. When c2 is 2, 3, or 4, each R 32 may be the same as or different from one another. c1 is 1, 2, 3, or 4. c2 is 0, 1, 2, 3, or 4, where 1 ≤ c1 + c2 ≤ 5.
  10. The chemically amplified resist composition according to claim 7, wherein the polymer comprises at least one selected from repeating units represented by the following formula (c1), repeating units represented by the following formula (c2), repeating units represented by the following formula (c3), repeating units represented by the following formula (c4), and repeating units represented by the following formula (c5). (In the formula, d1 and d2 are independently 0, 1, 2, or 3.) e1 is either 0 or 1. e2 is either 0, 1, 2, 3, or 4. e3 is either 0, 1, 2, 3, or 4. However, when e1 is 0, 0 ≤ e2 + e3 ≤ 4, and when e1 is 1, 0 ≤ e2 + e3 ≤ 6. R and A are, independently, a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Z1 is a phenylene group which may have a single bond or a substituent. Z2 is a single bond, **-C(=O)-O- Z21- , **-C(=O)-NH- Z21- , or **-O- Z21- . Z21 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 halogen atom, a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. Z3 is a single bond, ether bond, ester bond, sulfonic acid ester bond, amide bond, sulfonamide bond, carbonate bond, or carbamate bond. Z4 is a single bond, or a divalent group obtained by combining an aliphatic hydrocarbylene group, a phenylene group, or a combination thereof, and may contain a halogen atom, a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. Z 5 is independently a single bond, a phenylene group which may have substituents, a naphthylene group which may have substituents, or *-C(=O)-O-Z 51- . Z 51 is an aliphatic hydrocarbylene group, a phenylene group which may have 1 to 10 carbon atoms, and the aliphatic hydrocarbylene group may contain a halogen atom, a hydroxyl group which may have ether bonds which may have ester bonds which may have lactone rings. Z6 is a single bond, ether bond, ester bond, sulfonic acid ester bond, amide bond, sulfonamide bond, carbonate bond, or carbamate bond. Each Z7 is independently a single bond, ***- Z71 -C(=O)-O-, ***-C(=O)-NH- Z71- , or ***-O- Z71- . Z71 is a hydroxylene group having 1 to 20 carbon atoms, which may contain heteroatoms. Each Z8 is independently a single bond, ****- Z81 -C(=O)-O-, ****-C(=O)-NH- Z81- , or ****-O- Z81- . Z81 is a hydroxylene group having 1 to 20 carbon atoms, which may contain heteroatoms. Z9 is 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- Z91- , *-C(=O)-N(H) -Z91- , or *-O- Z91- . Z91 is a phenylene group substituted with an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, or a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. * represents a bond with a carbon atom in the main chain. ** represents a bond with Z1 . *** represents a bond with Z6 . **** represents a bond with Z7 . L1 is a single bond, ether bond, ester bond, carbonyl group, sulfonic acid ester bond, sulfonamide bond, carbonate bond, or carbamate bond. Rf 1 and Rf 2 are, independently, a fluorine atom or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Rf3 and Rf4 are, 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, independently, a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. However, not all of Rf 5 and Rf 6 are hydrogen atoms at the same time. Rf 7 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 41 and R 42 are each independently a hydrocarbyl group having 1 to 20 carbon atoms, which may contain heteroatoms. Furthermore, R 41 and R 42 may bond to each other to form a ring with the sulfur atom to which they are bonded. R 43 is a C1-C20 hydrocarbyl group which may contain halogen atoms other than fluorine atoms, or heteroatoms. When e3 is 2, 3, or 4, each R 43 may be the same or different from each other, and multiple R 43s may bond to each other to form a ring with the carbon atoms to which they are bonded. M- is a non-nucleophilic counterion. A + is an onium cation.
  11. Furthermore, the chemically amplified resist composition according to claim 6, further comprising an organic solvent.
  12. Furthermore, the chemically amplified resist composition according to claim 6, comprising a quencher.
  13. Furthermore, the chemically amplified resist composition according to claim 6, comprising a photoacid generator other than the photoacid generator described in claim 5.
  14. Furthermore, the chemically amplified resist composition according to claim 6, comprising a surfactant.
  15. A pattern forming method comprising the steps of: forming a resist film on a substrate using the chemically amplified resist composition described in claim 6; exposing the resist film with high-energy rays; and developing the exposed resist film using a developer.
  16. The pattern formation method according to claim 15, wherein the high-energy beam is a KrF excimer laser beam, an ArF excimer laser beam, an electron beam, or extreme ultraviolet light with a wavelength of 3 to 15 nm.

Description

This invention relates to sulfonium salts, chemically amplified resist compositions, and patterning methods. In recent years, with the increasing integration and speed of LSIs, there has been a growing demand for miniaturization of pattern rules. As a result, far-ultraviolet lithography and extreme ultraviolet (EUV) lithography are considered promising next-generation microfabrication technologies. ArF lithography, which uses ArF excimer laser light, began to be used partially for the fabrication of 130 nm node devices and became the main lithography technology for 90 nm node devices. Initially, lithography using a 157 nm wavelength F2 laser was considered promising as the next 45 nm node lithography technology, but development delays due to various problems were pointed out. Therefore, ArF immersion lithography, which achieves high resolution by inserting a liquid with a refractive index higher than air, such as water, ethylene glycol, or glycerin, between the projection lens and the wafer, allows the numerical aperture (NA) of the projection lens to be designed to be 1.0 or higher. This immersion lithography requires a resist composition that is not easily eluted by water. In ArF lithography, to prevent the degradation of precise and expensive optical materials, there is a need for highly sensitive resist compositions that can achieve sufficient resolution with low exposure. The most common method to achieve this is to select components that are highly transparent at a wavelength of 193 nm. For example, for the base polymer, polyacrylic acid and its derivatives, norbornene-maleic anhydride alternating polymers, polynorbornene, ring-opening metathesis polymers, and ring-opening metathesis polymer hydrogenated polymers have been proposed, and some success has been achieved in improving the transparency of the resin itself. In recent years, negative-tone resists developed using organic solvents have gained attention alongside positive-tone resists developed using alkaline aqueous solutions. To resolve extremely fine hole patterns that cannot be achieved with positive-tone exposure, negative patterns are formed by using a high-resolution positive-type resist composition and developing it with an organic solvent. Furthermore, research is underway to achieve double the resolution by combining two development steps: alkaline aqueous solution development and organic solvent development. Conventional positive-type ArF resist compositions can be used as ArF resist compositions for negative-tone development with organic solvents, and pattern formation methods using these compositions are described in Patent Documents 1 to 3. To adapt to the rapid miniaturization of recent years, the development of resist compositions is progressing daily, along with process technologies. Various photoacid generators have been investigated, and sulfonium salts consisting of triphenylsulfonium cations and perfluoroalkanesulfonic acid anions are commonly used. However, the generated acid, perfluoroalkanesulfonic acid, particularly perfluorooctanesulfonic acid (PFOS), is difficult to decompose, bioaccumulates, and poses toxicity concerns, making its application to resist compositions difficult. Currently, photoacid generators that produce perfluorobutanesulfonic acid are used. However, when this is used in resist compositions, the diffusion of the generated acid is significant, making it difficult to achieve high resolution. To address this problem, various partially fluorine-substituted alkanesulfonic acids and their salts have been developed. For example, Patent Document 1 describes, as prior art, a photoacid generator that generates α,α-difluoroalkanesulfonic acid upon exposure, specifically a photoacid generator that generates di(4-tert-butylphenyl)iodonium 1,1-difluoro-2-(1-naphthyl)ethanesulfonate and α,α,β,β-tetrafluoroalkanesulfonic acid. However, although the fluorine substitution rate is reduced in all of these, they lack degradable substituents such as ester structures, making them insufficient from the standpoint of environmental safety due to their easy decomposition. Furthermore, there are limitations in molecular design for changing the size of the alkanesulfonic acid, and the starting materials containing fluorine atoms are expensive. Furthermore, with the reduction in circuit line width, the impact of contrast degradation due to acid diffusion in resist compositions has become even more serious. This is because the pattern dimensions approach the acid diffusion length, leading to a decrease in mask fidelity and deterioration of pattern rectangularity due to a larger dimensional deviation on the wafer (mask error factor (MEF)) relative to the mask dimensional deviation value. Therefore, in order to fully obtain the benefits of shorter wavelength and higher NA of the light source, it is necessary to increase the dissolution contrast or suppress acid diffusion more than with conventional materials. As one improvement measu