Resist composition and patterning process

A resist composition comprising a base polymer and a quencher containing an iodonium salt having the formula (A):

• wherein R1 is a hydroxyl group, C1-C6 straight, branched or cyclic alkyl or alkoxy group, C2-C6 straight, branched or cyclic acyloxy group, fluorine, chlorine, bromine, amino, —NR5—C(═O)—R6, or —NR5—C(═O)—O—R6, R5 is hydrogen or a C1-C6 straight, branched or cyclic alkyl group, R6 is a C1-C6 straight, branched or cyclic alkyl group or C2-C8 straight, branched or cyclic alkenyl group, X1 is a single bond or a (q+1)-valent C1-C20 linking group which may contain at least one moiety selected from ether, carbonyl, ester, amide, sultone, lactam, carbonate, halogen, hydroxyl and carboxyl;
• X2 is an ether, ester or amide group;
• R2 and R3 are each independently trifluoromethyl or a C6-C10 aryl, C2-C6 alkenyl or C2-C6 alkynyl group in which at least one hydrogen atom may be substituted by halogen, trifluoromethyl, C1-C10 straight, branched or cyclic alkyl, C1-C10 straight, branched or cyclic alkoxy, hydroxyl, carboxyl, C2-C10 straight, branched or cyclic alkoxycarbonyl, nitro and/or cyano;
• m is an integer of 1 to 5, n is an integer of 0 to 3, p is an integer of 1 to 4, and q is an integer of 1 to 3,
• wherein the base polymer further comprises recurring units of at least one type selected from the formulae (f1) to (f3):
• wherein RA is each independently hydrogen or methyl,
• Z1 is a single bond, phenylene group, —O—Z12— or —C(═O)—Z11-Z12—, Z11 is —O— or —NH—, Z12 is a C1-C6 straight, branched or cyclic alkylene group, C2-C6 straight, branched or cyclic alkenylene group or phenylene group, which may contain a carbonyl, ester, ether or hydroxy moiety,
• R21 to R28 are each independently a C1-C12 straight, branched or cyclic alkyl group which may contain a carbonyl, ester or ether moiety, or a C6-C12 aryl group or C7-C20 aralkyl group, in which at least one hydrogen may be substituted by a C1-C10 straight, branched or cyclic alkyl moiety, halogen, trifluoromethyl, cyano, nitro, hydroxyl, mercapto, C1-C10 straight, branched or cyclic alkoxy moiety, C2-C10 straight, branched or cyclic alkoxycarbonyl moiety, or C2-C10 straight, branched or cyclic acyloxy moiety, any two of R23, R24 and R25, or any two of R26, R27 and R28 may bond together to form a ring with the sulfur atom to which they are attached,
• Z2 is a single bond, —Z21—C(═O)—O—, —Z21—O— or —Z21—O—C(═O)—, Z21 is a C1-C12 straight, branched or cyclic alkylene group which may contain a carbonyl, ester or ether moiety,
• A is hydrogen or trifluoromethyl,
• Z3 is a single bond, methylene group, ethylene group, phenylene group, fluorinated phenylene group, —O—Z32—, or —C(═O)—Z31-Z32—, Z31 is —O— or —NH—, Z32 is a C1-C6 straight, branched or cyclic alkylene group, phenylene, fluorinated phenylene or trifluoromethyl-substituted phenylene group, or C2-C6 straight, branched or cyclic alkenylene group, which may contain a carbonyl, ester, ether or hydroxyl moiety, and
• M− is a non-nucleophilic counter ion.