A novel interatomic potential energy function is proposed for condensed systems composed of silicon and oxygen atoms, from SiO2 to Si crystal. The potential function is an extension of the Stillinger-Weber potential, which was originally designed for pure Si systems. All parameters in the potential function were determined based on ab initio molecular orbital calculations of small clusters. Without any adjustment to empirical data, the order of stability of five silica polymorphs is correctly reproduced. This potential realizes a large-scale modeling of SiO2/Si interface structures on average workstation computers.

Ab initio theoretical computations have been performed to reveal the mechanism of the etching reaction of silicon oxide (SiO2) by HF molecules. The probable reaction paths, in which the etching reaction proceeds through four sequential steps to remove a single fragment of SiO2, are presented with their potential energy curves. In every step, the insertion of an HF molecule into an Si-O bond leads to the dissociation of the Si-O connection. The potential energy barriers evaluated along the reaction paths suggest that the HF molecule has an ability to etch the SiO2 surface. The strong interaction among HF molecules, however, likely causes HF polymer formation, which is expected to reduce the reaction rate of SiO2 etching.

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