Mesoscale simulation of molecular glass photoresists: effect of PAG loading and acid diffusion coefficient

Abstract

A mesoscale model of molecular resists has been created and implemented that allows for the investigation of the effect of material composition and physiochemical properties, such as PAG loading and photoacid diffusion coefficient, on the lithographic performance (i.e. resolution, line edge roughness, and sensitivity or as commonly referred to "RLS") of molecular glass photoresists. This model is shown to produce results that are in good agreement with many of the conventional LER scaling arguments. In cases where critical dimension is not held constant, it was found that higher photoacid diffusion improves LER at low acid concentrations, but induces higher LER at high acid concentration as compared to smaller diffusion coefficients. Increased PAG loadings were found to provide comparatively lower LER at the same resolution and sensitivity as lower PAG loadings, or alternatively to provide better sensitivity at the same resolution and LER as lower PAG loadings. Even at ultra-high PAG loadings, CARs were found to exhibit RLS limitations. By normalizing all PAG loadings by the total amount of acid produced, it is shown that LER is controlled primarily by photoacid concentration in the resist at the imaging dose for the case where constant critical dimension is maintained with no use of base quencher in the resist. Thus, the most direct and functional scaling argument for LER under such cases is, which is similar to the more common scaling arguments that state, but as this work shows it is more universal to state that which automatically normalizes for different PAG loadings and photoreaction rate constants across different resist formulations.