Two-Dimensional Simulation of Photolithography on Reflective Stepped Substrate

A new method for two-dimensional (2D) photolithography simulation is proposed. Lightwaves in photoresist are assumed to be polarized, and the layer beneath the photoresist is assumed to be a perfect conductor. In order to analyze lightwave behavior in a 2D region, Maxwell equations for electromagnetic fields are simplified into a Helmholtz equation which is solved in the photoresist region, taking lightwave damping in the infinite vacuum region surrounding the photoresist into account. The finite-element method and boundary-element method are used in the calculations. The bleaching model proposed by Drill et al. is applied to describe photoresist behavior on irradiation by exposure light. When this simulation is applied to a photoresist system on a reflective stepped surface, the simulated photoresist image is found to be in reasonably good agreement with an actually developed profile.