Resist composition and patterning process

A resist composition comprising a base polymer and a sulfonium or iodonium salt having an anion and a cation,

• wherein the cation is a sulfonium cation having the formula (B) or iodonium cation having the formula (C):
• wherein R4, R5 and R6 are each independently a straight, branched or cyclic C1-C12 alkyl or oxoalkyl group, a straight, branched or cyclic C2 -C12 alkenyl or oxoalkenyl group, C6-C20 aryl group, or C7-C12 aralkyl or aryloxoalkyl group, in which at least one hydrogen may be substituted by a substituent containing an ether, ester, carbonyl, carbonate, hydroxyl, carboxyl, halogen, cyano, amide, nitro, sultone, sulfonic acid ester, sulfone, thiol moiety or sulfonium salt,
• R7 and R8 are each independently a C6-C20 aryl group in which at least one hydrogen may be substituted by a straight, branched or cyclic C1-C10 alkyl or alkoxy moiety, and
• the anion in the sulfonium or iodonium salt is selected from the group consisting of the following formulae:

A resist composition comprising a base polymer and a sulfonium or iodonium salt having the formula (A):

• wherein the circle RA is a C3-C12 cyclic hydrocarbon group which may contain an ether, ester, thiol, sulfone moiety or double bond and may be a bridged ring, or a C6-C10 aryl group,
• R1 is hydrogen or a straight, branched or cyclic C1-C6 alkyl group,
• m is an integer of 0 to 5,
• R2 is selected from the group consisting of straight, branched or cyclic C1-C6 alkyl, acetyl, methoxycarbonyl, ethoxycarbonyl, n-propyloxycarbonyl, isopropyloxycarbonyl, t-butoxycarbonyl, t-pentyloxycarbonyl, methylcyclopentyloxycarbonyl, ethylcyclopentyloxycarbonyl, methylcyclohexyloxycarbonyl, ethylcyclohexyloxycarbonyl, 9-fluorenylmethyloxycarbonyl, allyloxycarbonyl, phenyl, benzyl, naphthyl, naphthylmethyl, methoxymethyl, ethoxymethyl, propoxymethyl, and butoxymethyl,
• R3 is a straight, branched or cyclic C1-C24 alkylene group which may contain a hydroxyl, alkoxy, ether, ester, sulfonic acid ester, cyano moiety, halogen atom, double bond, triple bond or aromatic moiety, with the proviso that the α-carbon attached to SO3− in formula (A) is not substituted with fluorine,
• A+ is a sulfonium cation having the formula (B) or iodonium cation having the formula (C):
• wherein R4, R5 and R6 are each independently a straight, branched or cyclic C1-C12 alkyl or oxoalkyl group, a straight, branched or cyclic C2-C12 alkenyl or oxoalkenyl group, C6-C20 aryl group, or C7-C12 aralkyl or aryloxoalkyl group, in which at least one hydrogen may be substituted by a substituent containing an ether, ester, carbonyl, carbonate, hydroxyl, carboxyl, halogen, cyano, amide, nitro, sultone, sulfonic acid ester, sulfone, thiol moiety or sulfonium salt,
• R7 and R8 are each independently a C6-C20 aryl group in which at least one hydrogen may be substituted by a straight, branched or cyclic C1-C10 alkyl or alkoxy moiety.