US 10,620,533 B2  143  144  9.  The resist composition of claim  7  which is a chemically  amplified negative resist composition.  10.  The resist composition of claim  1  wherein the base  polymer comprises recurring units of at least one type  selected from the formulae (fl) to (f3):  2.  The resist composition of claim  1,  wherein the pho- toacid generator is capable of generating sulfonic acid, imide  acid or methide acid.  3.  The resist composition of claim  1,  further comprising  an organic solvent.  4.  The resist composition of claim  1  wherein the base  polymer comprises recurring units having the formula (al)  or recurring units having the formula (a2):  wherein R  11  and R  13  are each independently hydrogen or 55  methyl, R 12  and R $^{14 }$are each independently an acid labile  group, X is a single bond, ester group, phenylene group,  naphthylene group or a C$_{1 }$-C$_{12 }$ linking group containing  lactone ring, and Y is a single bond or ester group.  5.  The resist composition of claim  4,  further comprising 60  a dissolution inhibitor.  6.  The resist composition of claim  4  which is a chemically  amplified positive resist composition.  7.  The resist composition of claim  1  wherein the base  polymer is free of an acid labile group.  8.  The resist composition of claim  7,  further comprising  a crosslinker.  wherein R 51 , R 55  and R 59  each are hydrogen or methyl,  R 52  is a single bond, phenylene, -O-R 63 -, or  ----C(=0)-Y 1 -R 63 -, Y $^{1 }$is ---0- or-NH-, R 63  is a straight, branched or cyclic  C$_{1 }$-C$_{6 }$ alkylene or  alkenylene group which may contain a carbonyl, ester,  ether or hydroxyl moiety, or phenylene group,  Rs3, Rs4, Rs6, Rs7, Rss, R6o, R61, and R62 are each  independently a straight, branched or cyclic  C$_{1 }$-C$_{12 }$ alkyl group which may contain a carbonyl, ester or  ether moiety, or a  CcC$_{12 }$ aryl group,  C$_{1 }$-C$_{20 }$ aralkyl  group or mercaptophenyl group,  A 1  is a single bond, -A $^{0}$----C(=0)-0-, -A$^{0}$-0- or -A $^{0}$-0----C(=0)-, A0  is a straight, branched or  cyclic  C$_{1 }$-C$_{12 }$ alkylene group which may contain a  carbonyl, ester or ether moiety,  A $^{2 }$is hydrogen or trifluoromethyl,  Z 1  is a single bond, methylene, ethylene, phenylene,  fluorinated phenylene,  ---O-R 64 -, or ----C(=0)› Z2-R64-,  Z 2  is ---0- or -NH-, R$^{64 }$is a straight,  branched or cyclic C$_{1 }$-C$_{6 }$ alkylene or alkenylene group  which may contain a carbonyl, ester, ether or hydroxyl  moiety, or phenylene, fluorinated phenylene or trifluo- romethyl-substituted phenylene group,  M- is a non-nucleophilic counter ion, and fl, f2 and f3 are  numbers in the range: 0sfls0.5, 0sf2s0.5, 0sf3s0.5,  and 0<fl+f2+f3s0.5.  11.  The resist composition of claim  1,  further comprising  a surfactant.  12.  A process for forming a pattern comprising the steps  of applying the resist composition of claim  1  onto a sub- strate, baking to form a resist film, exposing the resist film  to high-energy radiation, and developing the exposed film in  a developer.  -continued  >-0-1+-o-<  >=>-,-q  =t-0---,-0-f  >-0-1+-0- >=>-,-0- (a2)  ~  y  ORl4  (fl)  (fJ)  (f2)  R56  I  +s-R57  I  Rss 