Polymers with acid-amplifying side chains as positive-type photoresists

Abstract

Novel polymers substituted with acid-amplifying units in their side chain are described, aiming at developing photoresist materials exhibiting both of the suppression of the mobility of generated acids and the enhancement of photosensitivity. The thermal decomposition of pinanediol monosulfonate groups tethered covalently to polymer backbones derived from 2-hydroxypinanyl-3 p-styrenesulfonate proceeds non-linearly and involves the autocatalytic process to generate sulfonic acid groups in the side chains. Photoresists comprised of the homopolymer or a copolymer of a high loading (62%) of the acid-amplifying unit and a photoacid generator exhibited no alikaline developability probably because of a dissolution inhibitory effect of rearranged product(s) from the acid-amplifying unit. On the other hand, copolymers of the acid-amplifying monomer of 10% and 42% loadings with tert-butyl methacrylate gave positive-tone photoresists developable with an aqueous alkali to display high photosensitivity.