48  Nov. 22, 2018  US 2018/0335696 Al  bond, carbonate bond, 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;  saturated cyclic divalent hydrocarbon groups such as cyclo› pentanediyl, cyclohexanediyl, norbornanediyl, and adaman› tanediyl, and unsaturated cyclic divalent hydrocarbon  groups such as phenylene and naphthylene. Also included  are the foregoing groups in which at least one hydrogen  atom is replaced by an alkyl group such as methyl, ethyl,  propyl, n-butyl or t-butyl, or in which at least one hydrogen  atom is replaced by a radical containing a heteroatom such  as oxygen, sulfur, nitrogen or halogen, or in which at least  one carbon atom 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. Suitable  heteroatoms include oxygen, nitrogen, sulfur and halogen,  with oxygen being preferred.  [0091]  Of the PAGs having formula (2), those having  formula (2’) are preferred.  [0086]  The compound having the anion of formula (ID)  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.  [0087]  A compound having the formula (2) is also a useful  PAG.  [0088]  In formula (2), 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. 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,  ether group or a C$_{1 }$-C$_{20 }$straight, branched or cyclic 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  of0 to 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,  norbornyl,  oxanorbornyl,  tricyclo[5.2.l .0 2 • $^{6}$]decanyl, adamantyl, phenyl, naphthyl and  anthracenyl. Also included are the foregoing groups in  which at least one hydrogen is replaced by a heteroatom  such as oxygen, sulfur, nitrogen or halogen, or in which at  least one carbon is replaced by 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  [0093]  Examples of the PAG having formula (2) are  shown below, but not limited thereto. Herein R is as defined  above.  [0092]  In formula (2’), LA is as defined above. R is  hydrogen or trifluoromethyl, preferably trifluoromethyl.  R 301 , R $^{302 }$and R$^{303 }$are each independently hydrogen or a  C$_{1 }$-C$_{20 }$straight, branched or cyclic monovalent hydrocarbon  group which may contain a heteroatom. Suitable monova› lent hydrocarbon groups are as exemplified above for R  107 .  The subscripts x and y each are an integer of 0 to 5, and z  is an integer of 0 to 4.  0  0  0  (2)  (2’)  -continued 