Acid Generation Mechanism of Poly(4-hydroxystyrene)-Based Chemically Amplified Resists for Post-Optical Lithography: Acid Yield and Deprotonation Behavior of Poly(4-hydroxystyrene) and Poly(4-methoxystyrene)

Abstract

With the shrinkage of patterns, the elucidation of reaction mechanisms at the molecular level has become essential in resist design. In particular, proton dynamics is one of the most important issues on the sensitivity and resolution of chemically amplified resists. In chemically amplified resists for post-optical lithographies, such as extreme ultraviolet and electron beam lithographies, it has been reported that protons mainly come from not acid generators but polymers. Determining proton sources is a key to understanding reaction mechanisms at the molecular level. In this article, we investigated the deprotonation mechanism of poly(4-hydroxystyrene) and poly(4-methoxystyrene) upon exposure to ionizing radiation. We found that the difference between the proton labilities of polymer radical cations (proton source for acid generation) leads to a difference in acid yield.