Graft copolymers, process for the preparation thereof and ionizing radiation sensitive resist using such copolymers

摘要

Solvent-soluble copolymers having a number average molecular weight of about 1,000 to about 1,000,000 and comprising recurring units of the following formulae (I) and (II) (case A) or recurring unit of the following formulae (I), (II) and (III) (case B) or solvent-soluble graft copolymers having a number average molecular weight of about 1,500 to about 2,000,000 and comprising recurring units of the following formulae (I), (II) and/or (II'), and (IV) (case C) or recurring units of the following formulae (I), (II) and/or (II'), (III) and (IV) (case D), said recurring units being combined to form the main alkylene chain, wherein in the cases A and B the amount of the formula (I) unit is about 3 to 60 mol % of the total amount of the whole units, and in the cases C and D the amount of the formula (I) unit is about 5 to 60 mol % of the total amount of the units of formulae (I), (II) and/or (II'), and (IV), and in the cases B and D the amount of the formula (III) unit is about 1 to 40 mol % of the total amount of the whole units, and in the cases C and D the amount of the side chains enclosed in brackets of the formula (IV) unit is at least about 10% by weight of the amount of the main chain, exclusive of the bracketed grafted side chains, of the graft copolymer: <IMAGE> <IMAGE> +TR <IMAGE> wherein each of R1, R2 and R3 represents independently hydrogen, a straight or branched chain alkyl group having 1 to 4 carbon atoms or a halogen; R4 represents hydrogen or a straight or branched chain alkyl group having 1 to 10 carbon atoms; R5 represents an alkyl group having 1 to 6 carbon atoms, a phenyl group or a benzyl group; R6 represents hydrogen or a methyl group; R7 represents a straight or branched chain alkyl group having 1 to 10 carbon atoms, an aryl group, an aralkyl group or an aminoalkyl group; and n is an integer of 1 to 50. A resist having an excellent sensitivity to ionizing radiations and a high resolution, and also having a high dry etching resistance is provided by using these copolymers and graft copolymers.