Partially hydrogenated polymers and chemically amplified positive resist

Abstract

A polymer comprising recurring units of formula (1) is provided wherein some of the hydrogen atoms of phenolic hydroxyl groups and/or alcoholic hydroxyl groups are replaced by acid labile groups. The polymer is crosslinked within a molecule and/or between molecules with a crosslinking group having a C--O--C linkage resulting from reaction of some of the remaining phenolic hydroxyl groups and/or alcoholic hydroxyl 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 alcoholic hydroxyl group. The polymer has Mw of 1,000-500,000. ##STR1## R.sup.1 is H or methyl, R.sup.2 is C.sub.1 -C.sub.8 alkyl, letter x is 0 or a positive integer, y is a positive integer, x+y.ltoreq.5, letters p and q are positive numbers satisfying p+q=1 and 0<q/(p+1).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.