Polymers and chemically amplified positive resist compositions

Abstract

A polymer comprising recurring units of formula (1) is provided wherein some hydrogen atoms of phenolic hydroxyl groups and/or carboxyl groups are replaced by acid labile groups. The polymer is crosslinked with a crosslinking group having a C--O--C linkage resulting from reaction of some of the remaining phenolic hydroxyl groups and/or carboxyl groups with an alkenyl ether compound or halogenated alkyl ether compound. The amount of the acid labile group and the crosslinking group combined is on the average from more than 0 mol % to 80 mol % of the entirety of the phenolic hydroxyl group and carboxyl group. The polymer has Mw of 1,000-500,000. R.sup.1 is H or methyl, R.sup.2 is C.sub.1 -C.sub.8 alkyl, R.sup.3 is H, R.sup.4 is --COOR.sup.5, C.sub.1 -C.sub.5 alkyl or phenyl, or R.sup.3 and R.sup.4, taken together, may form --COOCO--, R.sup.5 is H or C.sub.1 -C.sub.8 alkyl, x and y are integers satisfying x+y.ltoreq.5, p and q are positive numbers satisfying p+q=1 and 0<q/(p+q).ltoreq.0.9. A chemically amplified positive resist composition comprising the polymer as a base resin has high sensitivity and resolution and forms resist patterns having plasma etching resistance, heat resistance, overhang prevention, and dimensional controllability.