US 10 698 314 B2  3  4  -continued  experiences no film thickness loss after development  and  has a high sensitivity  minimized LWR and improved CDU.  In one aspect  the invention provides a chemically ampli› fied resist composition comprising a quencher containing a  quaternary ammonium salt selected from the group consist- ing of a quaternary ammonium iodide  quaternary ammo› nium dibromoiodide  quaternary ammonium bromodiiodide   and quaternary ammonium triiodide  and an acid generator.  In one preferred embodiment  the quaternary ammonium  salt has the formula (1) or (2).  Herein R 1  to R 4  and R 5  to R$^{10 }$are each independently a  C 1  -C 24  straight  branched or cyclic alkyl group   C 2 -C 24  straight  branched or cyclic alkenyl group  C 2 -C 24  straight   branched or cyclic alkynyl group  or  CcC$_{24 }$ aryl group   which may contain a halogen  hydroxyl  carboxyl  ether   ester  thiol  thioester  thionoester  dithioester  amino  nitro   sulfone or ferrocenyl moiety  a pair ofR 1  and R 2   R 1  and R 4    R 2  and R 3   and/or R 3  and R 4  may bond together to form a  ring  or a pair ofR 1  and R 2   R 1  and R 4   R 2  and R 4   or R 3  and  R 4   taken together  may form a double bond  R 11  is a C 2 -C$_{12 }$ straight  branched or cyclic alkylene group which may  contain an ether and/or ester moiety   x- is an anion selected  from the group consisting of  1-   Br  2 1-   Brl 2  - and  1 3  - .  In one preferred embodiment  the acid generator is  capable of generating sulfonic acid  imidic acid or methide  acid.  The resist composition may further comprise a base  polymer.  In owe preferred embodiment  the base polymer com› prises recurring units of at least one type selected from  recurring units having the formulae (fl) to (f3).  Herein  RA  is each independently hydrogen or methyl. Z 1  is  a single bond  phenylene   ---O-Z 11 -   or ----C(=0)› Z12-Z11-   Z 11  is a C 1 -C 6  straight  branched or cyclic  alkylene group or C 2 -C 6  straight  branched or cyclic alk- enylene group which may contain a carbonyl  ester  ether or  hydroxyl moiety  or phenylene group  Z 12  is ---0- or  -NH- Rs1 Rs2 Rs3 Rs4  Rss  Rs6 Rs7 and Rss are each  independent!; a  cl  -c:2  st;aight  br~nch;d or cyclic alkyl  group which may contain a carbonyl  ester or ether moiety   or a  CcC$_{12 }$ aryl   C 7 -C$_{20 }$ aralkyl  or mercaptophenyl group.  Z 2  is a single bond  -Z 21 -C(O)O-  -Z 21 -0-  or  -Z 21 -0----C(=0)-  Z 21  is a C 1 -C$_{12 }$straight  branched or  cyclic alkylene group which may contain a carbonyl  ester or  ether moiety. Z 3  is a single bond  methylene  ethylene   phenylene   fluorinated  phenylene   ---O-Z 31 -   or  ----C(=0)-Z$^{32}$-Z 31 -  Z $^{31 }$is a C 1 -C 6  straight  branched  or cyclic alkylene group or C 2 -C 6  straight  branched or  cyclic alkenylene group which may contain a carbonyl   ester  ether or hydroxyl moiety  or a phenylene  fluorinated  phenylene or trifluoromethyl-substituted phenylene group   Z 32  is ---0- or -NH-. A  1  is hydrogen or trifluoromethyl   and  M- is a non-nucleophilic counter ion.  In one preferred embodiment  the acid generator also  functions as a base polymer. In this case  the acid generator  is a polymer comprising recurring units of at least one type  selected from recurring units having the formulae (fl) to (f3)  defined above.  In one preferred embodiment  the base polymer comprises  recurring units having the formula (al) or recurring units  having the formula (a2).  (fl)  (f2)  (al)  (a2)  ~  OR22  Herein  RA  is each independently hydrogen or methyl  R 11  and R 12  are each independently an acid labile group  X 1  is a  single bond  phenylene  naphthylene  or a $^{C}$1 -C$_{12 }$ linking  group containing ester moiety or lactone ring  and X 2  is a  single bond or ester group.  (fJ) 