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US-12625429-B2 - Resist composition and pattern forming process

US12625429B2US 12625429 B2US12625429 B2US 12625429B2US-12625429-B2

Abstract

A resist composition comprising a base polymer comprising repeat units having a salt structure consisting of a sulfonic acid anion bonded to a polymer backbone and a sulfonium cation having an acid labile group of aromatic group-containing cyclic secondary or tertiary ester type as the acid generator exhibits a high sensitivity and reduced LWR or improved CDU.

Inventors

  • Jun Hatakeyama
  • Masahiro Fukushima

Assignees

  • SHIN-ETSU CHEMICAL CO., LTD.

Dates

Publication Date
20260512
Application Date
20230131
Priority Date
20220204

Claims (11)

  1. 1 . A resist composition comprising a base polymer comprising repeat units (a) having a salt structure consisting of a sulfonic acid anion bonded to a polymer backbone and a sulfonium cation having the formula (1): wherein p is 0 or 1, q is an integer of 0 to 4, r is 1 or 2, s is an integer of 1 to 3, R 1 is a single bond, ether bond, thioether bond or ester bond, R 2 is a single bond or a C 1 -C 20 alkanediyl group which may contain fluorine or hydroxy, R 3 is hydroxy, carboxy, nitro, cyano, fluorine, chlorine, bromine, iodine, amino, or a C 1 -C 20 saturated hydrocarbyl group, C 1 -C 20 saturated hydrocarbyloxy group, C 2 -C 20 saturated hydrocarbylcarbonyloxy group, C 2 -C 20 saturated hydrocarbyloxycarbonyl group, or C 1 -C 4 saturated hydrocarbylsulfonyloxy group, which may contain at least one moiety selected from fluorine, chlorine, bromine, iodine, hydroxy, amino and ether bond, R 4 is a C 1 -C 20 hydrocarbyl group which may contain a heteroatom, in case of s=1, two groups R 4 may be the same or different and may bond together to form a ring with the sulfur atom to which they are attached, R AL is an acid labile group having any one of the formulae (AL-1) to (AL-4): wherein m1 is an integer of 0 to 4, n1 is an integer of 0 to 3, m1+n1 is from 0 to 4, m2 is an integer of 0 to 6, n2 is an integer of 0 to 3, m2+n2 is from 0 to 6, n3 is an integer of 0 to 4, n4 is an integer of 0 to 4, R 5 is hydrogen, or a C 1 -C 12 saturated hydrocarbyl group, C 2 -C 8 alkenyl group, C 2 -C 8 alkynyl group, or C 6 -C 10 aryl group, which may contain oxygen or sulfur, R 6 is fluorine, iodine, an optionally fluorinated C 1 -C 4 alkyl group, optionally fluorinated C 1 -C 4 alkoxy group, or optionally fluorinated C 1 -C 4 alkylthio group, R 7 is hydroxy, nitro, cyano, chlorine, bromine, amino, phenyl, a C 2 -C 4 alkoxycarbonyl group, or C 1 -C 4 alkylsulfonyl group, in case of n2=2 or 3, two groups R 7 may bond together to form a ring with the carbon atoms to which they are attached, R 8 is a C 2 -C 6 alkenyl group, the arc R a1 is a C 2 -C 10 tetravalent saturated hydrocarbon group which may contain oxygen, sulfur, nitrogen or a C 6 -C 10 aromatic moiety in a carbon-carbon bond, the arc R a2 is a C 2 -C 10 tetravalent saturated hydrocarbon group which may contain oxygen, sulfur or nitrogen in a carbon-carbon bond, the circle R a3 is a C 3 -C 10 (n3+2)-valent alicyclic hydrocarbon group having a double bond in the ring and/or an alkylidene moiety bonded to a carbon atom in the ring, the circle R a4 is a C 3 -C 10 (n4+2)-valent cyclic saturated hydrocarbon group, and the broken line designates a valence bond.
  2. 2 . The resist composition of claim 1 wherein the repeat units (a) have the formula (a1) or (a2): wherein R A is each independently hydrogen or methyl, X 1 is a single bond or ester bond, X 2 is a single bond, —X 21 —C(═O)—O— or —X 21 —O—, wherein X 21 is a C 1 -C 12 hydrocarbylene group, phenylene group or a C 7 -C 18 group obtained by combining the foregoing, which may contain carbonyl, ester bond, ether bond, iodine or bromine, X 3 is a single bond, methylene or ethylene, X 4 is a single bond, methylene, ethylene, phenylene, methylphenylene, dimethylphenylene, fluorinated phenylene, trifluoromethyl-substituted phenylene, —O—X 41 —, —C(═O)—O—X 41 — or —C(═O)—NH—X 41 wherein X 41 is a C 1 -C 6 aliphatic hydrocarbylene group, phenylene group, methylphenylene group, dimethylphenylene group, fluorinated phenylene group or trifluoromethyl-substituted phenylene group, which may contain carbonyl, ester bond, ether bond, hydroxy or halogen, Rf 1 to Rf 4 are each independently hydrogen, fluorine or trifluoromethyl, at least one of Rf 1 to Rf 4 is fluorine or trifluoromethyl, Rf 1 and Rf 2 may together form a carbonyl group, M + is the sulfonium cation having formula (1).
  3. 3 . The resist composition of claim 1 wherein m1 is an integer of 1 to 4 and m2 is an integer of 1 to 6.
  4. 4 . The resist composition of claim 1 , further comprising an organic solvent.
  5. 5 . The resist composition of claim 1 wherein the base polymer further comprises repeat units having the formula (b1) or repeat units having the formula (b2): wherein R A is each independently hydrogen or methyl, Y 1 is a single bond, phenylene, naphthylene, or a C 1 -C 12 linking group containing at least one moiety selected from an ester bond, ether bond and lactone ring, Y 2 is a single bond or ester bond, Y 3 is a single bond, ether bond or ester bond, R 11 and R 12 are each independently an acid labile group, R 13 is fluorine, trifluoromethyl, cyano, a C 1 -C 6 saturated hydrocarbyl group, C 1 -C 6 saturated hydrocarbyloxy group, C 2 -C 7 saturated hydrocarbylcarbonyl group, C 2 -C 7 saturated hydrocarbylcarbonyloxy group, or C 2 -C 7 saturated hydrocarbyloxycarbonyl group, R 14 is a single bond or a C 1 -C 6 alkanediyl group in which some constituent —CH 2 — may be replaced by an ether bond or ester bond, a is 1 or 2, b is an integer of 0 to 4, and a+b is from 1 to 5.
  6. 6 . The resist composition of claim 5 which is a chemically amplified positive resist composition.
  7. 7 . The resist composition of claim 1 , further comprising a surfactant.
  8. 8 . The resist composition of claim 1 wherein n3 is an integer of 1 to 4.
  9. 9 . The resist composition of claim 1 wherein n4 is an integer of 1 to 4.
  10. 10 . A pattern forming process comprising the steps of applying the resist composition of claim 1 onto a substrate to form a resist film thereon, exposing the resist film to high-energy radiation, and developing the exposed resist film in a developer.
  11. 11 . The pattern forming process of claim 10 wherein the high-energy radiation is KrF excimer laser, ArF excimer laser, EB, or EUV of wavelength 3 to 15 nm.

Description

CROSS-REFERENCE TO RELATED APPLICATION This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application Nos. 2022-016244 and 2022-166350 filed in Japan on Feb. 4, 2022 and Oct. 17, 2022, respectively, the entire contents of which are hereby incorporated by reference. TECHNICAL FIELD This invention relates to a resist composition and a patterning process using the composition. BACKGROUND ART To meet the demand for higher integration density and operating speed of LSIs, the effort to reduce the pattern rule is in rapid progress. As the use of 5G high-speed communications and artificial intelligence (AI) is widely spreading, high-performance devices are needed for their processing. As the advanced miniaturization technology, manufacturing of microelectronic devices at the 5-nm node by the lithography using EUV of wavelength 13.5 nm has been implemented in a mass scale. Studies are made on the application of EUV lithography to 3-nm node devices of the next generation and 2-nm node devices of the next-but-one generation. IMEC in Belgium announced its successful development of 1-nm and 0.7-nm node devices. As the feature size reduces, image blurs due to acid diffusion become a problem. To insure resolution for fine patterns of sub-45-nm size, not only an improvement in dissolution contrast is important as previously reported, but the control of acid diffusion is also important as reported in Non-Patent Document 1. Since chemically amplified resist compositions are designed such that sensitivity and contrast are enhanced by acid diffusion, an attempt to minimize acid diffusion by reducing the temperature and/or time of post-exposure bake (PEB) fails, resulting in drastic reductions of sensitivity and contrast. A triangular tradeoff relationship among sensitivity, resolution, and edge roughness (LWR) has been pointed out. Specifically, a resolution improvement requires to suppress acid diffusion whereas a short acid diffusion distance leads to a decline of sensitivity. The addition of an acid generator capable of generating a bulky acid is an effective means for suppressing acid diffusion. It was then proposed to incorporate repeat units derived from an onium salt having a polymerizable unsaturated bond in a polymer. Since this polymer functions as an acid generator, it is referred to as polymer-bound acid generator. Patent Document 1 discloses a sulfonium or iodonium salt having a polymerizable unsaturated bond, capable of generating a specific sulfonic acid. Patent Document 2 discloses a sulfonium salt having a sulfonic acid directly attached to the backbone. For forming patterns of smaller size, it is necessary not only to suppress acid diffusion, but also to enhance dissolution contrast. For enhancing dissolution contrast, a base polymer of polarity switch type capable of generating a phenol or carboxy group through acid-catalyzed deprotection reaction is used. On use of a resist material containing this base polymer, it is possible to form both a positive pattern by alkaline development and a negative pattern by organic solvent development. The positive pattern is formed at a higher resolution because the alkaline development provides a higher dissolution contrast. The base polymer adapted to generate a carboxy group exhibits higher alkaline solubility and hence, a higher dissolution contrast than the base polymer adapted to generate a phenol group. For such reasons, the base polymer of carboxy generation type is often used. There is known a non-chemically amplified resist material of backbone decomposition type comprising as the base polymer a copolymer of α-chloroacrylate with α-methylstyrene wherein the copolymer backbone is decomposed upon light exposure so that the copolymer reduces its molecular weight and turns more soluble in organic solvent developer. Although this resist material is devoid of the influence of acid diffusion, its dissolution contrast is low. The above-mentioned chemically amplified resist material having polarity switch function exhibits a higher resolution. For further enhancing dissolution contrast, it is proposed to add an acid generator having a polarity switch function as well as the base polymer having a polarity switch function to the resist material. Patent Documents 3 and 4 disclose a resist material comprising a sulfonium salt having an acid labile group of tertiary ester type in the cation moiety. Patent Document 5 discloses a resist material comprising a polymer having a sulfonic acid anion bonded to a polymer backbone and a sulfonium cation having an acid labile group. However, the acid labile groups of alicyclic structure and dimethylphenylcarbinol type described in these patent documents are still insufficient in dissolution contrast enhancement and swell suppression. CITATION LIST Patent Document 1: JP-A 2006-045311 (U.S. Pat. No. 7,482,108)Patent Document 2: JP-A 2006-178317Patent Document 3: JP-A 2011-006400Patent Document 4: JP-A 2021-