US 10,620,533 B2  153  154  -continued  -continued  (f2)  R56  I  +s-Rs7  I  Rss  (fJ)  (A)  (B)  (C) (fl)  16.  A resist composition comprising a base polymer and  a sulfonium or iodonium salt having the formula (A):  wherein  R  $^{1 }$is a straight, branched or cyclic  C$_{1 }$-C$_{24 }$ alkylene  group which may contain, an alkoxy, ether, ester, sulfonic  acid ester moiety, double bond, triple bond or aromatic  moiety,  A+  is a sulfonium cation having the formula  (B)  or  iodonium cation having the formula (C):  wherein R 2 , R 3  and R 4  are each independently a straight,  branched or cyclic  C$_{1 }$-C$_{12 }$ alkyl or oxoalkyl group, a  straight, branched or cyclic  C$_{2}$-C$_{12 }$ alkenyl or oxoalkenyl  group,  C$_{6}$-C$_{20 }$ aryl group, or  C$_{7}$ -C$_{12 }$ aralkyl or aryloxoalk~l  group, in which at least one hydrogen of at least one of R ,  R $^{3 }$and  R 4  is 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, or R 2  and R 3  may bond  together to form a ring with the sulfur atom to which they are  attached,  R 5  and R 6  are each independently a  CcC$_{20 }$ aryl group in 50  which at least one hydrogen may be substituted by a  straight, branched or cyclic C$_{1 }$-C$_{10 }$ alkyl or alkoxy  moiety,  wherein the base polymer comprises recurring units of at  least one type selected from the formulae (fl) to (f3):  wherein R 51 , R $^{55 }$and R $^{59 }$each are hydrogen or methyl,  R 52  is a single bond, phenylene, ---0- R 63 -, or  ----C(=0)-Y 1 -R 63 -, Y $^{1 }$is ---0- or-NH-, R 63  is a straight, branched or cyclic  C$_{1 }$-C$_{6 }$ alkylene or  alkenylene group which may contain a carbonyl, ester,  ether or hydroxyl moiety, or phenylene group,  Rs3  Rs4 Rs6 Rs7 Rss R6o R61  and R62 are each  i~depe~dently a ~traight, br~ch~d or cyclic  C$_{1 }$-C$_{12 }$ alkyl group which may contain a carbonyl, ester or  ether moiety, or a  CcC$_{12 }$ aryl group,  C$_{7}$ -C$_{20 }$ aralkyl  group or mercaptophenyl group,  A 1  is a single bond, -A$^{0}$----C(=0)-0-, -A$^{0}$-0- or -A$^{0}$-0----C(=0)-, A 0  is a straight, branched or  cyclic  C$_{1 }$-C$_{12 }$ alkylene group which may contain a  carbonyl, ester or ether moiety,  A 2  is hydrogen or trifluoromethyl,  Z 1  is a single bond, methylene, ethylene, phenylene,  fluorinated phenylene, ---O-R 64 -, or ----C(=0)› Z2 -R  6 4-,  Z 2  is -0- or -NH-, R $^{64 }$is a straight,  branched or cyclic C$_{1 }$-C$_{6 }$ alkylene or alkenylene group  which may contain a carbonyl, ester, ether or hydroxyl  moiety, or phenylene, fluorinated phenylene or trifluo› romethyl-substituted phenylene group,  M- is a non-nucleophilic counter ion, and fl, f2 and f3 are  numbers in the range: 0sfls0.5, 0sf2s0.5, 0sf3s0.5,  and 0<fl+f2+f3s0.5, and  the sulfonium or iodonium cation is selected from the  group consisting of the following formulae: 