Investigation on polymer design to enhance dissolution inhibition effects of photochemical acid generators for hexafluoroisopropylalcohol‐containing polystyrene in non‐chemically amplified resists

Abstract

This paper presents the origin and mechanism of a dissolution inhibition effect of a photochemical acid generator (PAG) for a non-chemically amplified resist based on hexafluoroisopropylalcohol (HFA)-containing styrene (HFASt) in an alkaline developer. For the photoresist systems consisting of copolymers of HFASt/another p-substituted St and a sulfonium salt-type PAG, solubility tests for coating films in the alkaline developer and proton nuclear magnetic resonance analysis and theoretical calculations for mixtures of the monomers and PAG were performed. It was found that p-substituted St monomers with a highly polar functional group and an electron-dense aromatic ring were effective in the dissolution inhibition. Since the interaction between p-substituted St monomers and the cationic part of PAG was well predictable and quantifiable with theoretical calculations, which was consist well with the experimental data, the study method adopted in this study enables rational structural design of the polymers/PAG system that exhibits a high dissolution inhibition effect, which can lead to the development of non-chemically amplified positive tone-type resist materials usable for the formation of high-resolution patterns.