Resist composition and patterning process

1. A resist composition consisting of a sulfonium salt of a carboxylic acid having an iodine or bromine-substituted hydrocarbyl group wherein the hydrocarbyl group is not an aromatic ring,

a base polymer, and

an acid generator capable of generating a sulfonic acid, imide acid or methide acid, and

optionally at least one selected from the group consisting of

an organic solvent,

surfactant,

dissolution inhibitor,

crosslinker,

a quencher other than the sulfonium salt of the carboxylic acid having the iodine or bromine-substituted hydrocarbyl group having formula (A) which is a conventional basic compound or an onium salt of sulfonic acids which are not fluorinated at α-position,

a water repellency improver, and

an acetylene alcohol,

wherein the sulfonium salt of the carboxylic acid having the iodine or bromine-substituted hydrocarbyl group has the formula (A):

wherein m and n are each independently an integer of 1 to 3,

X BI is iodine or bromine,

X 1 is a single bond, ether bond, ester bond, amide bond, carbonyl group or carbonate group,

X 2 is a single bond or a C 1 -C 20 (m+1)-valent hydrocarbon group which may contain a heteroatom exclusive of iodine and bromine,

R 1 is a C 1 -C 20 (n+1)-valent aliphatic hydrocarbon group which may contain at least one moiety selected from the group consisting of fluorine, chlorine, hydroxyl, carboxyl, C 6 -C 12 aryl, ether bond, ester bond, carbonyl, amide bond, carbonate, urethane bond and urea bond,

R 2 , R 3 and R 4 are each independently fluorine, chlorine, bromine, iodine, or a C 1 -C 20 hydrocarbyl group which may contain a heteroatom, R 2 and R 3 may bond together to form a ring with the sulfur atom to which they are attached, and

m is an integer of 1 to 3, and

wherein the acid generator has the formula (1), (2), (3-1) or (3-2):

wherein R 101 , R 102 , and R 103 are each independently fluorine, chlorine, bromine, iodine, or a C 1 -C 20 hydrocarbyl group which may contain a heteroatom, any two of R 101 , R 102 , and R 103 may bond together to form a ring with the sulfur atom to which they are attached, and

X″ is an anion of the following formula (1A), (1B), (1C) or (1D):

wherein R fa is fluorine or a C 1 -C 40 hydrocarbyl group which may contain a heteroatom,

R fb1 and R fb2 are each independently fluorine or a C 1 -C 40 hydrocarbyl group which may contain a heteroatom, R fb1 and R fb2 may bond together to form a ring with the linkage: —CF 2 —SO 2 —N − —SO 2 —CF 2 — to which they are attached,

R fc1 , R fc2 , and R fc3 are each independently fluorine or a C 1 -C 40 hydrocarbyl group which may contain a heteroatom, R fc1 and R fc2 may bond together to form a ring with the linkage: —CF 2 —SO 2 —N − —SO 2 —CF 2 — to which they are attached, and

R fd is a C 1 -C 40 hydrocarbyl group which may contain a heteroatom,

wherein, R 201 and R 202 are each independently a C 1 -C 30 hydrocarbyl group which may contain a heteroatom, R 203 is a C 1 -C 30 hydrocarbylene group which may contain a heteroatom, any two of R 201 , R 202 , and R 203 may bond together to form a ring with the sulfur atom to which they are attached,

L A is a single bond, ether bond or a C 1 -C 20 hydrocarbylene group which may contain a heteroatom,

X A , X B , X C and X D are each independently hydrogen, fluorine or trifluoromethyl, with the proviso that at least one of X A , X B , X C and X D is fluorine or trifluoromethyl, and

k is an integer of 0 to 3,

wherein r is an integer of 1 to 3, s is an integer of 1 to 5, t is an integer of 0 to 3, and 1≤s+t≤5,

X BI is iodine or bromine, and may be identical or different when s and/or r are at least 2,

L 1 is a single bond, ether bond, ester bond, or a C 1 -C 6 saturated hydrocarbylene group which may contain an ether bond or ester bond,

L 2 is a single bond or a C 1 -C 20 divalent linking group when r=1, or a C 1 -C 20 (r+1)-valent linking group when r=2 or 3,

R 401 is hydroxyl, carboxyl, fluorine, chlorine, bromine, amino group, or a C 1 -C 20 saturated hydrocarbyl, C 1 -C 20 saturated hydrocarbyloxy, C 2 -C 20 saturated hydrocarbyloxycarbonyl, C 2 -C 20 saturated hydrocarbylcarbonyloxy, or C 1 -C 20 saturated hydrocarbylsulfonyloxy group, which may contain fluorine, chlorine, bromine, hydroxyl, amino or ether bond, or —NR 401A —C(═O)—R 401B or —NR 401A —C(═O)—O—R 401B , R 401A is hydrogen, or a C 1 -C 6 saturated hydrocarbyl group which may contain halogen, hydroxy, C 1 -C 6 saturated hydrocarbyloxy, C 2 -C 6 saturated hydrocarbylcarbonyl or C 2 -C 6 saturated hydrocarbylcarbonyloxy moiety, R 401B is a C 1 -C 16 aliphatic hydrocarbyl group or C 6 -C 12 aryl group, which may contain halogen, hydroxyl, C 1 -C 6 saturated hydrocarbyloxy, C 2 -C 6 saturated hydrocarbylcarbonyl or C 2 -C 6 saturated hydrocarbylcarbonyloxy moiety, groups R 401 may be identical or different when t and/or r are 2 or 3,

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, or Rf 1 and Rf 2 , taken together, may form a carbonyl group,

R 402 , R 403 , R 404 , R 405 and R 406 are each independently a C 1 -C 20 hydrocarbyl group which may contain a heteroatom, any two of R 402 , R 403 and R 404 may bond together to form a ring with the sulfur atom to which they are attached.

2. The resist composition of claim 1 wherein the base polymer comprises recurring units having the formula (a1) or recurring units having the formula (a2):

wherein R A is each independently hydrogen or methyl, R 11 and R 12 each are an acid labile group, Y 1 is a single bond, phenylene group, naphthylene group, or C 1 -C 12 linking group containing ester bond or lactone ring, Y 2 is a single bond or ester bond.

3. The resist composition of claim 2 which is a chemically amplified positive resist composition.

4. The resist composition of claim 1 wherein the base polymer is free of an acid labile group.

5. The resist composition of claim 4 which is a chemically amplified negative resist composition.

6. The resist composition of claim 1 , further comprising an organic solvent.

7. The resist composition of claim 1 , further comprising a surfactant.

8. A process for forming a pattern comprising the steps of applying the resist composition of claim 1 onto a substrate to form a resist film, exposing the resist film to high-energy radiation, and developing the exposed resist film in a developer.

9. The process of claim 8 wherein the high-energy radiation is i-line of wavelength 365 nm, ArF excimer laser radiation of wavelength 193 nm or KrF excimer laser radiation of wavelength 248 nm.

10. The process of claim 8 wherein the high-energy radiation is EB or EUV of wavelength 3 to 15 nm.

11. The resist composition of claim 1 wherein X BI is iodine.

12. A resist composition consisting of a sulfonium salt of a carboxylic acid having an iodine or bromine-substituted hydrocarbyl group wherein the hydrocarbyl group is not an aromatic ring, and

a base polymer, and

optionally at least one selected from the group consisting of

an acid generator capable of generating a sulfonic acid, imide acid or methide acid,

an organic solvent,

surfactant,

dissolution inhibitor,

crosslinker,

a quencher other than the sulfonium salt of the carboxylic acid having the iodine or bromine-substituted hydrocarbyl group having formula (A) which is a conventional basic compound or an onium salt of sulfonic acids which are not fluorinated at α-position,

a water repellency improver, and

an acetylene alcohol,

wherein the sulfonium salt of the carboxylic acid having the iodine or bromine-substituted hydrocarbyl group has the formula (A):

wherein m and n are each independently an integer of 1 to 3,

X BI is iodine or bromine,

X 1 is a single bond, ether bond, ester bond, amide bond, carbonyl group or carbonate group,

X 2 is a single bond or a C 1 -C 20 (m+1)-valent hydrocarbon group which may contain a heteroatom exclusive of iodine and bromine,

R 1 is a C 1 -C 20 (n+1)-valent aliphatic hydrocarbon group which may contain at least one moiety selected from the group consisting of fluorine, chlorine, hydroxyl, carboxyl, C 6 -C 12 aryl, ether bond, ester bond, carbonyl, amide bond, carbonate, urethane bond and urea bond,

R 2 , R 3 and R 4 are each independently fluorine, chlorine, bromine, iodine, or a C 1 -C 20 hydrocarbyl group which may contain a heteroatom, R 2 and R 3 may bond together to form a ring with the sulfur atom to which they are attached, and

m is an integer of 1 to 3, and

wherein the base polymer comprises recurring units of at least one type selected from recurring units having the formulae (f 1 ) to (f 3 ):

wherein R A is each independently hydrogen or methyl,

Z 1 is a single bond, phenylene group, —O—Z 11 —, —C(═O)—O—Z 11 —, or —C(═O)—NH—Z 11 —is a C 1 -C 6 aliphatic hydrocarbylene group or phenylene group, which may contain a carbonyl, ester bond, ether bond or hydroxyl moiety,

Z 2 is a single bond, —Z 21 —C(═O)—O—, —Z 21 —O— or —Z 21 —O—C(═O)—is a C 1 -C 12 saturated hydrocarbylene group which may contain a carbonyl moiety, ester bond or ether bond,

Z 3 is a single bond, methylene, ethylene, phenylene, fluorinated phenylene, —C(═O)—O—R 31 —, or —C(═O)—NH—Z 31 — is a C 1 -C 6 aliphatic hydrocarbylene group, phenylene group, fluorinated phenylene group, or trifluoromethyl-substituted phenylene group, which may contain a carbonyl moiety, ester bond, ether bond or hydroxyl moiety,

R 21 to R 28 are each independently a C 1 -C 20 hydrocarbyl group which may contain a heteroatom, any two of R 23 , R 24 and R 25 or any two of R 26 , R 27 and R 28 may bond together to form a ring with the sulfur atom to which they are attached,

A 1 is hydrogen or trifluoromethyl, and

M − is a non-nucleophilic counter ion.

13. The resist composition of claim 12 wherein X BI is iodine.