Analysis of Quencher Diffusion in Chemically Amplified Resists and Its Effect on Imaging Characteristics

Diffusion of quencher contained in most chemically amplified resists today can cause proximity effects such as dependence of pattern feature size on pattern density or iso-dense bias. Diffusion coefficients were measured for several quencher compounds, and significantly large diffusion coefficients (e.g. 0.003μm2/sec at 100°C) were observed compared with those observed for acid. To evaluate the influence of quencher diffusion on macroscopic imaging behavior of resists, a new resist model for mutual diffusion of acid and quencher was introduced and was implemented to our in-house lithography simulator. Simulation results based on the model explained various proximity effects observed on real wafers, assuming quencher diffusion length as large as 0.2μm. This is significantly long compared with acid diffusion lengths reported and agrees with the results of direct measurement. Our results suggest that very small amount of quencher can have a strong influence on imaging characteristics of chemically amplified resists.