Abstract
Understanding acid reaction-diffusion kinetics is crucial for controlling the lithographic performance of chemically amplified photoresists. In this work, we study how the molecular architectures of positive-tone chemically amplified molecular glass resists can affect acid reaction-diffusion kinetics during post exposure bake. We compare the acid reaction-diffusion kinetics of a common photoacid generator in molecular glass resists with chemical structural similarity to poly(4-hydroxystyrene), designed with branched and ring architectures. An in situ FTIR method was used to measure reaction rate, acid trapping behavior, and acid diffusivity as a function of post exposure bake temperature. We have found that the acid kinetics performance in molecular glass resists is correlated to the film molar densities which are affected by the architectures of the resist molecules. These results allow a modeling analysis of latent image formation in molecular glass resists, which is critical for resolution and line edge roughness of pattern features. A comparison between experimentally measured and theoretically predicted diffusion lengths in one molecular glass resist system was made. Since there is little understood about acid diffusion in molecular glass resists, this paper is the first that tackles this process across a variety of materials and provides some insight into the molecular design of photoresists for high resolution lithography.
