Orientation-dependent surface morphology of crystalline silicon during anisotropic etching using a continuous cellular automaton

Abstract

The formation of morphological protrusions on the surface during anisotropic wet etching is addressed computationally by modifying a step-flow-based continuous cellular automaton (CCA) in order to incorporate the stochastic adsorption and desorption of impurity particles on the surface. The CCA method is characterized by the possibility of calibrating the site-specific atomistic removal rates of the step-flow model in order to describe the macroscopic orientation dependence of the etch rate obtained in an experiment. Interestingly, the combination of the deposition model with previously calibrated site-specific atomistic removal rates leads to a realistic description of the experimental surface morphologies for a wide range of crystalline orientations. This is shown by considering the wet etching of crystalline silicon in two very different etchants, namely pure KOH and KOH with isopropanol (IPA). The modified CCA makes possible the realization of accurate and realistic simulations of anisotropic etching in realistic engineering applications.