content_image/902052.jpg content_image/902051.jpg content_image/902049.jpg content_image/902050.jpg content_image/902047.jpg content_image/902048.jpg
<img src='content_image/902052.jpg'>

[0116] In formulae (1-1) and (1-2), x-is an anion of the following formula (IA), (18), (IC) or (ID). 

<img src='content_image/902051.jpg'>

<img src='content_image/902049.jpg'>

<img src='content_image/902050.jpg'>

[0117] In formula (IA), Wais fluorine or a C$_{1}$-C$_{40 }$mon› ovalent hydrocarbon group which may contain a heteroa› tom. The monovalent hydrocarbon group may be straight, branched or cyclic, and examples thereof include those exemplified later for R 107 . 

[0118] Of the anions of formula (IA), an anion having the formula (IA’) is preferred. 

[0119] In formula (IA’), R$^{106 }$is hydrogen or trifluorom› ethyl, preferably trifluoromethyl. 

[0120] R 107 is a C$_{1 }$-C$_{38 }$ monovalent hydrocarbon group which may contain a heteroatom. As the heteroatom, oxy› gen, 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. The monovalent hydrocarbon groups may be straight, branched or cyclic. Examples thereof include, but are not limited to, straight or branched alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pen› tyl, neopentyl, hexyl, heptyl, 2-ethylhexyl, nonyl, undecyl, tridecyl, pentadecyl, heptadecyl, and eicosanyl; monovalent saturated alicyclic hydrocarbon groups such as cyclopentyl, cyclohexyl, 1-adamantyl, 2-adamantyl, 1-adamantylmethyl, norbornyl, norbomylmethyl, tricyclodecanyl, tetracyclodo› decanyl, tetracyclododecanylmethyl, and dicyclohexylm› ethyl; monovalent unsaturated aliphatic hydrocarbon groups such as ally! and 3-cyclohexenyl; aryl groups such as phenyl, 1-naphthyl and 2-naphthyl; and aralkyl groups such as benzyl and diphenylmethyl. Examples of the monovalent hydrocarbon group having a heteroatom include tetrahydro› furyl, methoxymethyl, ethoxymethyl, methylthiomethyl, acetamidomethyl, trifluoroethyl, (2-methoxyethoxy)methyl, acetoxymethyl, 2-carboxy-1-cyclohexyl, 2-oxopropyl, 4-oxo-1-adamantyl, and 3-oxocyclohexyl. In these groups, some hydrogen may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, or some carbon may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxyl, cyano, carbonyl, ether bond, ester bond, sulfonic acid ester bond, carbonate moiety, lactone ring, sultone ring, carboxylic anhydride or haloalkyl moiety. 

[0121] 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 

<img src='content_image/902047.jpg'>

<img src='content_image/902048.jpg'>

-continued 

