Jul. 30, 2020  2  US 2020/0241417 Al  (A-1)  [0022]  In another embodiment, the base polymer is free of  an acid labile group. Typically, the resist composition is a  chemically amplified negative resist composition.  [0023]  The resist composition may further comprise a  surfactant.  [0024]  In a preferred embodiment, the base polymer fur› ther comprises recurring units of at least one type selected  from recurring units having the formulae (fl) to (f3).  [0019]  The resist composition may further comprise an  acid generator capable of generating a sulfonic acid, imide  acid or methide acid, and an organic solvent.  [0020]  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 -, Z 11  is a Cl-C6  alkanediyl group, C$_{2}$-C 6  alkenediyl 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$^{21}$-O- or -Z$^{21}$---0----C(=O)-, Z 21  is a  (al)  Herein Xis a single bond or a C$_{1 }$-C$_{20 }$divalent linking group  which may contain an ether bond, carbonyl moiety, ester  bond, amide bond, sultone ring, lactam ring, carbonate bond,  halogen, hydroxyl moiety or carboxyl moiety. R 1  is hydro› gen, hydroxyl, an optionally halo-substituted C$_{1 }$-C 6  alkyl  group, optionally halo-substituted C$_{1 }$-C 6  alkoxy group,  optionally halo-substituted C$_{2}$-C 6  acyloxy group, optionally  halo-substituted C$_{1 }$-C$_{4 }$ alkylsulfonyloxy group, fluorine,  chlorine, bromine, amino, nitro, cyano, -NR$^{1}$A-C(=O)› R, or -NR$^{1}$A-C(=O)-O-R 1 B, R $^{1}$A is hydrogen or a  C$_{1 }$-C 6  alkyl group,  RIB  is a C$_{1 }$-C 6  alkyl group or C$_{2}$-C$_{5 }$ alkenyl group. R 2  and R 3  are each independently a C$_{1}$-C 6  alkyl group, R$^{2 }$andR$^{3 }$may bond together to form a ring with  the carbon atom to which they are attached. R 4  and R 6  are  each independently hydrogen, a C$_{1 }$-C$_{4 }$ straight or branched  alkyl group, C$_{2}$ -C$_{12 }$ straight or branched alkoxycarbonyl  group. CcC$_{15 }$aryloxycarbonyl group, or CcC$_{14 }$aralkyloxy› carbonyl group. R 5  is a C$_{1 }$-C 6  alkyl group, C$_{2}$-C 6  alkenyl  group, C$_{2}$ -C 6  alkynyl group, or C 6 -C$_{12 }$ aryl group. R is a  C$_{2}$ -C$_{10 }$alicyclic group to form a ring with the nitrogen atom,  m is an integer of 1 to 5, n is an integer of 0 to 4, and  lsm+ns5, and pis 1 or 2.  (A-2)  (fJ)  (f2)  R23  I  +s-R24  I  R2s  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.  [0021]  Typically, the resist composition is a chemically  amplified positive resist composition.  -continued  (a2)  ~  y2  Q  OR12  (fl) 