US 2020/0050104 Al  65  Feb. 13, 2020  cfo~s~  lYO~SO;  0 ;(Y 0 ~s~  1(1  " 0 ~SO;  ~  CF3  0  CF3  O ~S03- CF3  -continued  [0085]  The compound having the anion of formula (3D)  has a sufficient acid strength to cleave acid labile groups in  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.  [0086]  Also compounds having the formula (  4)  are useful  as the PAG.  (4)  [0087]  In formula (  4),  R 201  and R$^{202 }$are each indepen› dently a C$_{1 }$-C$_{30 }$ straight, branched or cyclic monovalent  hydrocarbon group which may contain a heteroatom. R $^{203 }$is  a C$_{1 }$-C$_{30 }$ straight, branched or cyclic divalent hydrocarbon  group which may contain a heteroatom.  [0088]  Any two ofR 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, ether bond or a straight,  branched or cyclic 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 of  XA, XB, Xe  and  xn  is  fluorine or trifluoromethyl, and k is an integer of Oto 3.  [0089]  Suitable monovalent hydrocarbon groups include  methyl, ethyl, propyl, isopropyl, n-butyl, s-butyl, t-butyl,  n-pentyl, t-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, cyclo› pentyl, cyclohexyl, 2-ethylhexyl, cyclopentylmethyl, cyclo› pentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclo› hexylethyl,  cyclohexylbutyl,  norbomyl,  oxanorbornyl,  tricyclo[5.2.  l  .0 2 • $^{6}$]decanyl, adamantyl, phenyl, naphthyl and  anthracenyl. Also included are the foregoing groups in  which some hydrogen is replaced by a radical containing a  heteroatom such as oxygen, sulfur, nitrogen or halogen, or in  which some carbon is replaced by a radical containing a  heteroatom such as oxygen, sulfur or nitrogen, so that the  group may contain a hydroxyl, cyano, carbonyl, ether, ester,  sulfonic acid ester, carbonate, lactone ring, sultone ring,  carboxylic acid anhydride or haloalkyl radical.  [0090]  Suitable divalent hydrocarbon groups include lin› ear alkane diyl groups such as methylene, ethylene, propane- 1,3-diyl; butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl,  heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane- 1,  10-diyl, undecane-1, 11-diyl, dodecane-1, 12-diyl, tride› cane-1, 13-diy  1,  tetradecane-1, 14-diy  1,  pentadecane-1, 15- diy  l,  hexadecane-1,16-diyl,  heptadecane-1,17-diyl; 