US 10,802,400 B2  87  88  As the PAG used herein, sulfonium salts having the  formula  (1-1)  and iodonium salts having the formula (1-2)  are also preferred.  In formulae  (1-1)  and (1-2), R 101 , R 102 , R 103 , R $^{104 }$and  R $^{105 }$are each independently a C $_{1 }$-C$_{20 }$ straight, branched or  cyclic monovalent hydrocarbon 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.  Suitable examples of the cation moiety in the sulfonium  salt having formula  (1-1)  are as exemplified above as the  cation moiety in the recurring unit (al). Suitable examples  of the cation moiety in the iodonium salt having formula  (1-2) are as exemplified above as the cation moiety in the  recurring unit (a2).  In formulae  (1-1)  and (1-2), x- is an anion of the  following formula (IA), (18), (IC) or (ID).  In formula (IA),  wa  is fluorine or a cl -C40 straight,  branched or cyclic monovalent hydrocarbon group which  may contain a heteroatom.  Of the anions of formula (IA), an anion having the  formula (IA’) is preferred.  In formula (IA’), R 106  is hydrogen or trifluoromethyl,  preferably trifluoromethyl. R  107  is  a C$_{1 }$-C$_{38 }$ straight,  branched or cyclic monovalent hydrocarbon group which  may contain a heteroatom. As the heteroatom, oxygen,  nitrogen, sulfur and halogen atoms are preferred, with  oxygen being most preferred. Of the monovalent hydrocar› bon groups represented by R 107 , those groups of 6 to 30  carbon atoms are preferred from the aspect of achieving a  high resolution in forming patterns of fine feature size.  Suitable monovalent hydrocarbon groups include, but are  not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobu› tyl, s-butyl, t-butyl, pentyl, neopentyl, cyclopentyl, hexyl,  cyclohexyl, 3-cyclohexenyl, heptyl, 2-ethylhexyl, nonyl,  undecyl, tridecyl, pentadecyl, heptadecyl, 1-adamantyl,  2-adamantyl, 1-adamantylmethyl, norbornyl, norbornylm› ethyl, tricyclodecanyl, tetracyclododecanyl, tetracyclodode› canylmethyl, dicyclohexylmethyl, eicosanyl, ally!, benzyl,  diphenylmethyl, tetrahydrofuryl, methoxymethyl, ethoxym› ethyl, methylthiomethyl, acetamidomethyl, trifluoroethyl,  (2-methoxyethoxy)methyl, acetoxymethyl, 2-carboxy-1-cy› clohexyl, 2-oxopropyl, 4-oxo-1-adamantyl, and 3-oxocyclo› hexyl. In these groups, one or more hydrogen atoms may be  substituted by a moiety containing a heteroatom such as  oxygen, sulfur, nitrogen or halogen, or one or more carbon  atoms may be substituted by a moiety containing a heteroa› tom such as oxygen, sulfur or nitrogen, so that the group  may contain a hydroxyl, cyano, carbonyl, ether, ester, sul- fonic acid ester, carbonate, lactone ring, sultone ring, car› boxylic anhydride or haloalkyl moiety.  With respect to the synthesis of the sulfonium salt having  an anion of formula (IA’), reference may be made to JP-A  2007-145797, JP-A 2008-106045, JP-A 2009-007327, and  JP-A 2009-258695. Also useful are the sulfonium salts  described in JP-A 2010-215608, JP-A 2012-041320, JP-A  2012-106986, and JP-A 2012-153644.  Examples of the anion of formula (IA) are shown below,  but not limited thereto.  (1-1)  (1-2)  R104  I  1+  x- i  RIOS  (lB)  (lC)  (lD) 