Electron-Beam Exposure Characteristics of Copolymers Containing 2, 3-Epithiopropyl Methacrylate

Abstract

Copolymers of 2, 3-epithiopropyl methacrylate (ETMA)-styrene derivatives were prepared by a solution polymerization in benzene using azobisisobutyronitrile as an initiator and the electron-beam exposure characteristics of these copolymers were investigated. p-Chlorostyrene (pCS), m-chlorostyrene (mCS), and (chloromethyl) styrene (CMS) were used as styrene derivatives. The copolymers with lower molecular weight distribution were obtained by fractionation of bulk copolymers using dissolution-precipitation method. The following resuits on electron-beam exposure characteristics were obtained: electron-beam sensitivity of these copolymers increased with increasing molecular weight and ETMA content. The copolymers with lower molecular weight and lower molecular weight distribution showed higher contrast. The sensitivity of ETMA-pCS copolymers was slightly lower than that of ETMAmCS copolymers, and the order of contrast was reverse to that of sensitivity. However ETMA-CMS copolymers had higher sensitivity than ETMA-pCS and ETMA-mCS, the ETMA-CMS was unstable as electron beam resist. ETMA-pCS 'copolymers had higher dry etching resistance than ETMA homopolymer. ETMA-pCS and ETMA-mCS copolymer showed resolution capacity of O.6 pm and 0.45 pm, respectively.