Application of chlorinated polymethylstyrene, CPMS, to electron beam lithography

Abstract

Swelling behavior and resist performance of a series of chlorinated polymethylstyrenes, CPMS, were investigated. Measurements of swelling ratio and resolution of the CPMS resist coating in a wide variety of organic solvents disclosed that resolution depends on the swelling ratio. In addition, it was found that Cellosolve acetate or methyl isobutyl ketone was the most suitable developer, and that the critical swelling ratio might be 3.2 (=1.473) for screening of a developer. Functional testings on CPMS showed the resist had considerably high sensitivity as well as high contrast and dry etch resistance. The selectivity ratio of the resist to aluminum, when the resist was used in a dry etching process, was 1.5 times as high as that of the conventional Novolak-type positive-working photoresist.