Resist composition and patterning process

1. A resist composition comprising a base polymer and a quencher,

said quencher comprising a salt compound having the formula (A):

wherein the ring R is a C 2 -C 12 alicyclic group containing the nitrogen atom, the ring may contain an ether bond, thioether bond, carbonyl group, —N(R′)— or sulfonyl group, R′ is hydrogen, a C 1 -C 6 saturated hydrocarbyl group or -L 3 -R 3 ,

L 1 , L 2 and L 3 are each independently a single bond, ester bond, sulfonyl group, or C 1 -C 6 alkanediyl group, some hydrogen in the alkanediyl group may be substituted by a hydroxy moiety, optionally fluorinated C 1 -C 12 hydrocarbyloxy moiety, or optionally fluorinated C 2 -C 12 hydrocarbylcarbonyloxy moiety, and any methylene constituent in the alkanediyl group may be replaced by an ether bond, ester bond, amide bond, sulfonyl moiety, sulfonate bond, or sulfonamide bond, with the proviso that L 1 , L 2 and L 3 do not contain a tertiary ester structure,

R 1 , R 2 and R 3 are each independently hydrogen, a C 1 -C 16 saturated hydrocarbyl group, C 6 -C 10 aryl group, C 1 -C 16 saturated hydrocarbyl group substituted with at least three fluorine atoms, C 6 -C 10 aryl group substituted with at least three fluorine atoms, or a combination thereof, one or both of R 1 and R 2 have at least three fluorine atoms, and

X − is a carboxylate, sulfonamide, halogenated phenoxide or halide anion.

2. The resist composition of claim 1 wherein X − is a fluorinated or brominated carboxylate, fluorinated or brominated sulfonamide, or fluorinated or brominated phenoxide anion.

3. The resist composition of claim 1 , further comprising an acid generator capable of generating a sulfonic acid, imide acid or methide acid.

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

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

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 an ester bond and % or 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 or C 1 -C 6 saturated hydrocarbyl group,

R 14 is a single bond or a C 1 -C 6 alkanediyl group in which some carbon may be replaced by an ether bond or ester bond,

a is 1 or 2, b is an integer of 0 to 4, and 1≤a+b≤5.

6. The resist composition of claim 5 which is a chemically amplified positive resist composition.

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

8. The resist composition of claim 7 which is a chemically amplified negative resist composition.

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

10. The resist composition of claim 1 wherein the base polymer comprises repeat units of at least one type selected from repeat units having the formulae (f1) to (f3):

wherein R A is each independently hydrogen or methyl,

Z 1 is a single bond, a C 1 -C 6 aliphatic hydrocarbylene group, phenylene group, naphthylene group, or C 7 -C 18 group obtained by combining the foregoing, or —O—Z 11 —, —C(═O)—O—Z 11 — or —C(═O)—NH—Z 11 —, Z 11 is a C 1 -C 6 aliphatic hydrocarbylene group, phenylene group, naphthylene group, or C 7 -C 18 group obtained by combining the foregoing, which may contain a carbonyl moiety, ester bond, ether bond or hydroxy moiety,

Z 2 is a single bond or ester bond,

Z 3 is a single bond, —Z 31 —C(═O)—O—, —Z 31 —O— or —Z 31 —O—C(═O)—, Z 31 is a C 1 -C 12 hydrocarbylene group, phenylene group, or C 7 -C 18 group obtained by combining the foregoing, which may contain a carbonyl moiety, ester bond, ether bond, iodine or bromine,

Z 4 is a methylene, 2,2,2-trifluoro-1,1-ethanediyl or carbonyl group,

Z 5 is a single bond, methylene, ethylene, phenylene, fluorinated phenylene, trifluoromethyl-substituted phenylene group, —O—Z 51 —, —C(═O)—O—Z 51 —, or —C(═O)—NH—Z 51 —, Z 51 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 hydroxy moiety,

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

M − is a non-nucleophilic counter ion.

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

12. The process of claim 11 wherein the high-energy radiation is i-line of wavelength 365 nm, ArF excimer laser of wavelength 193 nm or KrF excimer laser of wavelength 248 nm.

13. The process of claim 11 wherein the high-energy radiation is EB or EUV of wavelength 3 to 15 nm.

14. A salt compound having the formula (A′):

wherein the ring R is a C 2 -C 12 alicyclic group containing the nitrogen atom, the ring may contain an ether bond, thioether bond, carbonyl group, —N(R′)— or sulfonyl group, R′ is hydrogen, a C 1 -C 6 saturated hydrocarbyl group or -L 3 -R 3 ,

L 1 , L 2 and L 3 are each independently a single bond, ester bond, sulfonyl group, or C 1 -C 6 alkanediyl group, some hydrogen in the alkanediyl group may be substituted by a hydroxy moiety, optionally fluorinated C 1 -C 12 hydrocarbyloxy moiety, or optionally fluorinated C 2 -C 12 hydrocarbylcarbonyloxy moiety, and any methylene constituent in the alkanediyl group may be replaced by an ether bond, ester bond, amide bond, sulfonyl moiety, sulfonate bond, or sulfonamide bond, with the proviso that L 1 , L 2 and L 3 do not contain a tertiary ester structure,

R 1 , R 2 and R 3 are each independently hydrogen, a C 1 -C 16 saturated hydrocarbyl group, C 6 -C 10 aryl group, C 1 -C 16 saturated hydrocarbyl group substituted with at least three fluorine atoms, C 6 -C 10 aryl group substituted with at least three fluorine atoms, or a combination thereof, one or both of R 1 and R 2 have at least three fluorine atoms,

R 4 is a single bond or carbonyl group,

R 5 is hydrogen, hydroxy group, optionally halogenated C 1 -C 6 saturated hydrocarbyl group, optionally halogenated C 1 -C 6 saturated hydrocarbyloxy group, optionally halogenated C 2 -C 7 saturated hydrocarbylcarbonyloxy group, optionally halogenated C 1 -C 4 saturated hydrocarbylsulfonyloxy group, fluorine, chlorine, bromine, amino group, nitro group, cyano group, —N(R 51 )—C(═O)—R 52 —, or —N(R 51 )—C(═O)—O—R 52 , R 51 is hydrogen or a C 1 -C 6 saturated hydrocarbyl group, R 52 is a C 1 -C 6 saturated hydrocarbyl group or C 2 -C 8 unsaturated aliphatic hydrocarbyl group,

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