Molecular dynamics simulations of Si etching by energetic CF3+

Abstract

The development of a Tersoff-type empirical interatomic potential energy function (PEF) for the Si–C–F system is reported. As a first application of this potential, etching of a:Si by CF3+ using molecular dynamics (MD) simulations is demonstrated. Aspects of CF3+ ion bombardment through a fluence of 4×1016 cm−2 are discussed, including overlayer composition and thickness, Si etch yields, and etch product distributions. The formation of a 1-nm-thick steady-state SixCyFz overlayer occurs in the simulation, and this layer is an active participant in the etching of the underlying Si. At an ion energy of 100 eV, a steady state the etch yield of Si is predicted to be 0.06±0.01 Si/ion. A comparison of the simulation findings and experimental results from the literature leads to the conclusion that the new PEF performs well in qualitatively modeling the atomic-scale processes involved in CF3+ ion beam etching of Si. Simulations of this kind yield insight into fluorocarbon etch mechanisms, and ultimately will result in phenomenological models of etching by fluorocarbon plasmas.