Design and synthesis of an optimum performance crosslinking resist based on poly (2,4-dimethylstyrene)

We have successfully synthesized and optimized a range of copolymers of 2,4-dimethylstyrene and 3/4-chloromethylstyrene (vinyl benzyl chloride, VBC) as high-performance single-stage-crosslinking electron-beam resists. The formulations were synthesized by a reproducible free-radical-initiated solution polymerization technique which has the merit of simplicity. While the product polymers are not monodisperse, and hence cannot achieve optimal lithographic contrast, they benefit from a structural feature which prevents chain scission during irradiation and hence increases the intrinsic sensitivity of the resist. Resists with sensitivities very close to target values of 5 and 12 μC cm^sup -2^ have been demonstrated, with negligible chain scission and lithographic contrast of 2.3. ©1999 Kluwer Academic Publishers[PUBLICATION ABSTRACT]