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[0220] It is demonstrated in Table 1 that positive resist compositions comprising a base polymer comprising recur› ring units containing iodine and amino offer a high sensi› tivity and improved CDU. 

[0221] Japanese Patent Application No. 2018-244436 is incorporated herein by reference. 

[0222] Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims. 

1. A positive resist composition comprising a base poly› mer comprising recurring units containing an optionally substituted amino group and iodine. 

2. The resist composition of claim 1 wherein the recurring units containing an optionally substituted amino group and iodine have the formula (a): 

wherein RA is hydrogen or methyl, X 1 is a single bond, phenylene, naphthylene, or a C$_{1 }$-C$_{12 }$linking group contain› ing an ester bond, ether bond or lactone ring, X 2 is a single bond or a C$_{1 }$-C$_{12 }$ divalent hydrocarbon group which may contain hydroxyl, ether bond or ester bond, R is hydroxyl, carboxyl, C$_{1 }$-C$_{4 }$ straight or branched alkyl group, C$_{1 }$-C$_{4 }$ straight or branched alkoxy group, C$_{2}$-C$_{5 }$ straight or branched alkoxycarbonyl group, C$_{2}$ -C$_{5 }$ straight or branched acyl group, C$_{2}$ -C$_{5 }$ straight or branched acyloxy group, or halogen exclusive of iodine, R 1 and R 2 are each indepen› dently hydrogen, C$_{1 }$-C$_{6 }$ alkyl group, C$_{2}$ -C$_{5 }$ alkenyl group, C$_{2}$ -C$_{6 }$ alkynyl group, C$_{2}$-C$_{7 }$ acyl group, C$_{2}$-C$_{7 }$ alkoxycar› bonyl group, C$_{2}$-C$_{7 }$ alkenyloxycarbonyl group, C$_{2}$ -C$_{7 }$ alky› nyloxycarbonyl group, C$_{7}$-C$_{12 }$ aryloxycarbonyl group, or C$_{1}$-C$_{12 }$ aralkyloxycarbonyl group, R 1 and R 2 may bond 

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together to form a ring with the nitrogen atom to which they are attached, the ring may contain an ether bond, m is an integer of 1 to 4, n is 1 or 2, p is an integer of O to 3, and 2sm+n+ps5. 

3. The resist composition of claim 1 wherein the base polymer further comprises recurring units having a carboxyl group substituted with an acid labile group and/or recurring units having a phenolic hydroxyl group substituted with an acid labile group. 

4. The resist composition of claim 3 wherein the recurring units having a carboxyl group substituted with an acid labile group and the recurring units having a phenolic hydroxyl group substituted with an acid labile group are recurring units having the formula (b 1) and recurring units having the formula (b2), respectively, 

wherein RA is each independently hydrogen or methyl, Y$^{1 }$is a single bond, phenylene, naphthylene, or a C$_{1 }$-C$_{12 }$linking group containing an ester bond, ether bond or lactone ring, Y 2 is a single bond, ester bond or amide bond, R $^{11 }$and R 12 are each independently an acid labile group, R$^{13 }$is fluorine, trifluoromethyl, cyano, or a C$_{1 }$-C$_{6 }$ alkyl group, R 14 is a single bond or C$_{1 }$-C$_{6 }$ straight or branched alkanediyl group in which some carbon may be replaced by an ether or ester bond, a is 1 or 2, and b is an integer of O to 4. 

5. The resist composition of claim 1 wherein the base polymer further comprises recurring units ( c) containing an adhesive group selected from the group consisting of hydroxyl, carboxyl, lactone ring, carbonate, thiocarbonate, 

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