Fundamental studies of the properties of photoresists based on resins containing polymer-bound photoacid generators

摘要

Conventional chemically amplified photoresist formulations are complex mixtures that include a protected polymer resin and a small molecule photoacid generator (PAG). The limited compatibility of the PAG with the photoresist resin and the relatively high mobilities of some small molecule PAG additives and their acid photoproducts can lead to a variety of problems including PAG phase separation in the photoresist during film formation, non-uniform initial PAG and photoacid distribution, and acid diffusion during the post-exposure baking (PEB) processes. The incorporation of PAG units into the main chain of the polymer resin is one possible method to alleviate these problems. Recently, we have investigated methacrylate based resists which incorporate novel PAG functional groups into the polymer main chain. These materials have demonstrated good resolution performance for both 193 nm and EUV exposure for sub-100 nm patterning. However, limited information is available on the effect of binding the PAG to the polymer on PAG photoreactivity and photoacid diffusivity. In this work, the photoacid generation rate constant (commonly referred to as the Dill C parameter for the PAG) of both triflate polymer-bound PAG and blended PAG photoresists based on poly(γ-butyrolactone methacrylate-co-2-ethyl-2-adamantyl methacrylate) resists were determined by a new technique utilizing both quantitative FTIR spectroscopy and kinetic model fitting. The initial results indicate that the polymer-bound PAG resist has a substantially lower photoacid generation rate constant (C=0.0122) than the analogous blended PAG material (C = 0.2647). This large difference in Dill C parameters would indicate that the sensitivity of the polymer-bound PAG resist is substantially lower than that of the analogous blended sample which is consistent with imaging experiments and contrast curve data for these two resists.