Feb.4,2021  2  US 2021/0033970 Al  Herein m is an integer of  1  to 5, n is an integer of  O  to  4,  lsm+ns5, p$^{1 }$is  1,  2 or 3, p 2  is  1  or 2, q$^{1 }$is  1,  2 or 3, and q 2  is  1,  2 or 3. X$^{1 }$is a C$_{1}$-C$_{20 }$(p$^{2}$+1)-valent hydrocarbon group  which may contain at least moiety selected from ester bond  and ether bond. R $^{1 }$is hydroxyl, C$_{1 }$-C$_{6 }$ saturated hydrocarbyl  group, C$_{1 }$-C$_{6 }$ saturated hydrocarbyloxy group, C$_{2}$ -C$_{6 }$ satu› rated hydrocarbylcarbonyloxy group, fluorine, chlorine, bro› mine, amino group, -NR$^{1}$A----C(=O)-R 1 B, or-NR $^{1}$A_  C(=O)-O-R 1 B, wherein R $^{1}$A is hydrogen or a C$_{1}$-C$_{6 }$ saturated hydrocarbyl group,  RIB  is a C$_{1 }$-C$_{6 }$ saturated hydro› carbyl, C$_{2}$-C$_{8 }$unsaturated aliphatic hydrocarbyl, C$_{6}$-C$_{12 }$aryl  or C$_{7}$ -C$_{13 }$ aralkyl group. R 2  is hydrogen, nitro, or a C$_{1}$-C$_{20 }$ hydrocarbyl group which may contain at least one moiety  selected from hydroxyl, carboxyl, thiol, ether bond, ester  bond, nitro, cyano, halogen and amino moiety, in case of  p$^{1}$=1 or 2, two R$^{2 }$may bond together to form a ring with the  nitrogen atom to which they are attached, the ring optionally  containing a double bond, oxygen, sulfur or nitrogen, or R 2  and X $^{1 }$may bond together to form a ring with the nitrogen  atom to which they are attached, the ring optionally con› taining a double bond, oxygen, sulfur or nitrogen.  XBI  is  iodine or bromine. X 2  is a single bond, ether bond, ester  bond, amide bond, carbonyl group or carbonate group. X $^{3 }$is  a single bond or a C$_{1 }$-C$_{20 }$( q$^{1 }$+  1  )-valent hydrocarbon group  which may contain a heteroatom exclusive of iodine and  bromine. R$^{3 }$is a C$_{1 }$-C$_{20 }$ ( q $^{2 }$+  1  )-valent aliphatic hydrocarbon  group which may contain at least one moiety selected from  fluorine, chlorine, hydroxyl, carboxyl, CcC$_{12 }$ aryl, ether  bond, ester bond, carbonyl, amide bond, carbonate, urethane  bond, and urea bond.  [0020]  The resist composition may further comprise an  acid generator capable of generating a sulfonic acid, imide  acid or methide acid and/or an organic solvent.  [0021]  In a preferred embodiment, the base polymer com› prises recurring units having the formula (al) or recurring  units having the formula (a2).  Herein  RA  is each independently hydrogen or methyl. Z 1  is  a single bond, phenylene group,  ---O-Z 11 -,  ----C(=O)› O-Z11- or ----C(=O)-NH-Z 11 -, wherein Z 11  is a  C$_{1 }$-C$_{6 }$ aliphatic hydrocarbylene group or phenylene group,  which may contain a carbonyl, ester bond, ether bond or  hydroxyl moiety. Z 2  is a single bond, -Z$^{21}$----C(=O)› O-, -Z$^{21}$---0-or-Z$^{21}$---0----C(=O)-, whereinZ$^{21 }$is  a C$_{1 }$-C$_{12 }$saturated hydrocarbylene group which may contain  Herein  RA  is each independently hydrogen or methyl, R 11  and R $^{12 }$each are an acid labile group, Y 1  is a single bond,  phenylene group, naphthylene group, or C$_{1 }$-C$_{12 }$ linking  group containing at least one moiety selected from ester  bond and lactone ring, and Y $^{2 }$is a single bond or ester bond.  [0022]  In one embodiment, the resist composition is a  chemically amplified positive resist composition.  [0023]  In another embodiment, the base polymer is free of  an acid labile group. The resist composition is typically a  chemically amplified negative resist composition.  [0024]  The base polymer may comprise recurring units of  at least one type selected from recurring units having the  formulae  (fl) to (f3).  (a2)  ~  y2  OR12  (A)  (fl)  (f2)  R23  I  +s-R24  I  R2s  (fJ)  R26  I  +s-R 27  I  R2s  (al)  -continued 