Feb.4,2021  74  US 2021/0033970 Al  acid ester bond, carbonate moiety, lactone ring, sultone ring,  carboxylic anhydride or haloalkyl moiety.  [0119]  The hydrocarbylene group R$^{203 }$may be saturated  or unsaturated and straight, branched or cyclic. Examples  thereof include alkanediyl groups such as methylene, eth› ylene, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl,  hexane-1,6-diyl, heptane-I, 7-diyl, octane-1,8-diyl, nonane- 1,9-diyl, decane-1,10-diyl, undecane-1,11-diyl, dodecane-1,  12-diyl, tridecane-1, 13-diyl, tetradecane-1, 14-diyl, pentade› cane-1, 15-diyl, hexadecane-1, 16-diyl, and heptadecane-1,  17-diyl; cyclic saturated hydrocarbylene groups such as  cyclopentanediyl, cyclohexanediyl, norbomanediyl and ada› mantanediyl; and arylene groups such as phenylene, meth› ylphenylene, ethylphenylene, n-propylphenylene, isopropy› lphenylene,  n-butylphenylene,  isobutylphenylene,  sec› butylphenylene,  tert-butylphenylene,  naphthylene,  methylnaphthylene,  ethylnaphthylene,  n-propylnaphthyl› ene,  isopropylnaphthylene,  n-butylnaphthylene,  isobutylnaphthylene,  sec-butylnaphthylene,  and  tert› butylnaphthylene. 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, lactone ring, sultone ring, car› boxylic anhydride or haloalkyl moiety. Of the heteroatoms,  oxygen is preferred.  [0120]  In formula (2),  LA is a single bond, ether bond or a  C$_{1 }$-C$_{20 }$hydrocarbylene group which may contain a heteroa› tom. The hydrocarbylene group may be saturated or unsatu› rated and straight, branched or cyclic. Examples thereof are  as exemplified above for R 203 .  [0121]  In formula (2),  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.  [0122]  Of the PAGs having formula (2), those having  formula (2’) are preferred.  [0123]  In formula (2’), LA is as defined above.  RHF  is  hydrogen or trifluoromethyl, preferably trifluoromethyl.  R 301 , R $^{302 }$and R$^{303 }$are each independently hydrogen or a  C$_{1 }$-C$_{20 }$hydrocarbyl group which may contain a heteroatom.  The hydrocarbyl group may be saturated or unsaturated and  straight, branched or cyclic. Examples thereof are as exem› plified above for R $^{107 }$in formula (IA’). The subscripts x and  y are each independently an integer of 0 to 5, and z is an  integer of 0 to 4.  [0124]  Examples of the PAG having formula (2) are as  exemplified for the PAG having formula (2) in JP-A 2017- 026980.  [0118]  The hydrocarbyl groups R 201  and R 202  may be  saturated or unsaturated and straight, branched or cyclic.  Examples thereof include alkyl groups such as methyl, ethyl,  propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl,  tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and  n-decyl; cyclic saturated hydrocarbyl groups such as cyclo› pentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl,  cyclopentylbutyl,  cyclohexylmethyl,  cyclohexylethyl,  cyclohexylbutyl, norbornyl, oxanorbomyl, tricyclo[5.2.l.0 2 •  6]decanyl, and adamantyl; and aryl groups such as phenyl,  naphthyl and anthracenyl. 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  [0117]  In formula (2), R 201  and R 202  are each indepen› dently a C$_{1 }$-C$_{30 }$ hydrocarbyl group which may contain a  heteroatom. R 203  is a C$_{1}$-C$_{30 }$ hydrocarbylene group which  may contain a heteroatom. Any two of R 201 , R $^{202 }$and R203  may bond together to form a ring with the sulfur atom to  which they are attached. Exemplary rings are the same as  described above for the ring that R $^{101 }$and R $^{102 }$in formula  (1-1), taken together, form with the sulfur atom to which  they are attached.  [0116]  Another preferred PAG is a compound having the  formula (2).  [0115]  Notably, the compound having the anion of for› mula (ID) does not have fluorine at the a-position relative  to the sulfa group, but two trifluoromethyl groups at the  ~-position. For this reason, it has a sufficient acidity to sever  the acid labile groups in the base polymer. Thus the com› pound is an effective PAG.  -continued  0  (2’)  (2) 