Modeling and Simulation of Silicon Dry Etching

As a widespread form of dry etching, deep reactive ion etching (DRIE) is a highly anisotropic etch process. It alternates switching the chemistry for etching and passivation cycles, typically leads to characteristic scalloping patterns on the sidewalls with high aspect ratios. Measurements of the etch depth per cycle l _d and undercut length per cycle l _u show a strong dependence of the undercut ratio l _u /l _d on the trench aspect ratio for a wide range of opening sizes. Although various simulation models have been proposed, the determination of the corresponding parameters from experimental data remains unsolved. We present the use of (i) the continuous cellular automaton (CCA), to simulate the process reliably in three dimensions; (ii) the particle swarm optimization (PSO) method, to determine suitable values for the atomistic CCA parameters directly from experimental data; and (iii) a GPU, parallel implementation of the CCA, to increase the computational efficiency of the simulations. The resultant, parameter-optimized CCA simulations show good agreement with the experiments. The approach has a large potential for the simulation of other MEMS processes.