Apr. 18,  2019  48  US 2019/0113844 Al  the base polymer because it is free of fluorine at a-position  of sulfa group, but has two trifluoromethyl groups at ~-po› sition. Thus the compound is a useful PAG.  [0113]  Further, compounds having the formula (2) are  useful as the PAG.  lactone ring, sultone ring, carboxylic acid anhydride or  haloalkyl moiety. Suitable heteroatoms include oxygen,  nitrogen, sulfur and halogen, with oxygen being preferred.  [0117]  Of the PAGs having formula (2), those having  formula (2’) are preferred.  [0114]  In formula (2), R 201  and R 202  are each indepen› dently a C$_{1 }$-C$_{30 }$monovalent hydrocarbon group which may  contain a heteroatom. R$^{203 }$is a C$_{1}$-C$_{30 }$divalent hydrocarbon  group which may contain a heteroatom. Any two of R 201 ,  R$^{202 }$and R$^{203 }$may bond together to form a ring with the  sulfur atom to which they are attached.  LA is a single bond  or ether bond, or a C$_{1 }$-C$_{20 }$divalent hydrocarbon group which  may contain a heteroatom.  XA, XB, Xe  and  xn  are each  independently hydrogen, fluorine or trifluoromethyl, with  the proviso that at least one  ofXA, XB, Xe  and  xn  is fluorine  or trifluoromethyl, and k is an integer of Oto 3.  [0115]  The monovalent hydrocarbon groups may be  straight, branched or cyclic and include straight or branched  alkyl groups such as methyl, ethyl, propyl, isopropyl, n-bu› tyl, s-butyl, t-butyl, n-pentyl, t-pentyl, n-hexyl, n-octyl,  n-nonyl, n-decyl, and 2-ethylhexyl; monovalent saturated  cyclic hydrocarbon groups such as cyclopentyl, cyclohexyl,  cyclopentylmethyl,  cyclopentylethyl,  cyclopentylbutyl,  cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, nor› bomyl, oxanorbomyl, tricyclo[5.2.l.0 2 • $^{6}$]decanyl, and ada› mantyl; and aryl groups such as phenyl, naphthyl and  anthracenyl. Also included are the foregoing groups in  which at least one hydrogen is substituted by a heteroatom  such as oxygen, sulfur, nitrogen or halogen, or in which at  least one carbon is substituted 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, lactone ring,  sultone ring, carboxylic acid anhydride or haloalkyl moiety.  [0116]  The divalent hydrocarbon groups may be straight,  branched or cyclic, and examples thereof include linear or  branched alkane diyl groups such as methylene, ethylene,  propane-1,3-diy 1, butane-1,4-diy 1, pentane-1, 5-diy 1, hexane- 1,6-diy l, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl,  decane-1, 10-diy 1, undecane-1, 11-diy 1, dodecane-1, 12-diy 1,  tridecane-1, 13-diyl, tetradecane-1, 14-diyl, pentadecane-1,  15-diy 1, hexadecane-1, 16-diy 1, heptadecane-1, 17 -diyl; satu› rated cyclic divalent hydrocarbon groups such as cyclopen› tanediyl,  cyclohexanediyl,  norbomanediyl,  and  adamantanediyl; and unsaturated cyclic divalent hydrocar› bon groups such as phenylene and naphthylene. Also  included are the foregoing groups in which at least one  hydrogen atom is substituted by an alkyl group such as  methyl, ethyl, propyl, n-butyl or t-butyl, or in which at least  one hydrogen atom is substituted by a moiety containing a  heteroatom such as oxygen, sulfur, nitrogen or halogen, or in  which at least one carbon atom is substituted 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,  [0119]  Examples of the PAG having formula (2) are shown  below, but not limited thereto. Herein R is as defined above.  [0118]  In formula (2’), LA is as defined above. R is hydro› gen or trifluoromethyl, preferably trifluoromethyl. R 301 ,  R$^{302 }$and R$^{303 }$are each independently hydrogen or a C$_{1 }$-C$_{20 }$ monovalent hydrocarbon group which may contain a het› eroatom. The monovalent hydrocarbon groups may be  straight, branched or cyclic, and examples thereof are as  exemplified above for R  105 . The subscripts x and y each are  an integer of 0 to 5, and z is an integer of 0 to 4.  (2)  (2’) 