Modeling soft bake effects in chemically amplified resists

For lithography simulation physically correct resist models are required to achieve the best prediction of resist images across multiple process conditions. In the past, very limited work has been done to integrate the soft bake process into the full resist model. In this paper we describe how the soft-bake process generates a non-isotropic physical state in the resist. Then simple models for the effect of the solvent concentration, quencher concentration and free volume on the Exposure, PEB and develop kinetics are proposed and implemented. These models are coupled with the soft bake evaporation diffusion model to produce a physically based chemically amplified resist model that covers every processing step. The resulting model is used to simulate the kinetics for a chemically amplified resist as a function of soft bake condition.