Thermal and acid-catalyzed deprotection kinetics in candidate deep ultraviolet resist materials

Abstract

Deep ultraviolet (UV) chemically amplified (CA) resists are leading candidates for semiconductor lithography manufacturing in the sub-half-micron regime. In this article, we describe in situ, high data rate, accurate measurements of the chemical kinetics that occur in CA resists during the post-exposure bake. The thermal and acid-catalyzed deprotection of two candidate deep-UV resist materials, poly(p-t-butoxycarbonyloxystyrene) (PTBOCST) and poly(t-butylmethacrylate) (PTBMA), was characterized. The thermal deprotection of PTBOCST and PTBMA showed auto-accelerated behavior as the reaction proceeds, while the acid-catalyzed deprotection displayed inhibition as extent of conversion increased. We propose models for the thermal and acid-catalyzed deprotection and extracted rate coefficients using a stochastic kinetics simulator. Excellent agreement between the model and experimental data was obtained.