Photoresists based on bisphenol A derivatives with tert-butyl ester groups for electron beam lithography

Abstract

Four branched bisphenol A derivatives decorated with tert-butyl ester group (BPA-BU-n, n = 1–4) were synthesized. The number of BU groups was controlled precisely by selective hydrogenation. The good thermal resistance and film-forming performance suggested that BPA-BU-1 and BPA-BU-2 are candidates for photoresist materials. They were used as positive-tone photoresists by mixing with a proportionate photo-acid generator and base. Both BPA-BU-1 and BPA-BU-2 resists can obtain 40 nm L/S patterns. BPA-BU-1 resist exhibits higher sensitivity and contrast than that of BPA-BU-2 resist for their different substituted positions of acid labile groups in the molecule. All the results demonstrated that protected ratio and position had a significant effect on the patterning ability of BPA-BUs resists. This study will help to understand the relationship between molecular structures and lithographic performance, and provide useful guidelines for designing molecular resists.