Application of Substructure Method to Three-Dimensional Optical Lithography Simulation

초록

Optical lithography simulators have been widely used for predicting and optimizing the lithographic processes. As the complexity of IC devices increases, the importance of three-dimensional simulators has been greatly increased in order to understand the scattering of light and the reflective notching inside the photoresist. Though several methods and techniques have been proposed for simulating the three dimensional case recently, the requirement of the huge memory and the long computation time makes it difficult to apply most of them in practice. In order to resolve these problem, we have newly proposed and developed the three-dimensional lithography simulator based on the finite element method (FEM). Contrary to the conventional FEM, we could resolve the problem of huge memory requirement by applying the substructure method to FEM. In our scheme, the overall domain, which consists of photoresist, interlayers, and the substrate, is divided into several subdomains. After each subdomain is treated locally, the calculation results are integrated altogether. Since the consuming memory is tremendously reduced by the substructure method, the three-dimensional case can be successfully simulated at the engineering workstation. We have compared our scheme with the conventional FEM and evaluated the reduction of computational memory by the substructure method. Finally some simulation results on the reflective notching are obtained.