Molecular dynamics simulations of Si-F surface chemistry with improved interatomic potentials

Molecular dynamics results using an improved Tersoff-Brenner style interatomic potential for Si-F (denoted by TB-HG) are presented. In simulations of F/Ar⁺, F⁺, and SiF₃⁺ etching of silicon, the TB-HG potential predicts different behaviour from that of Stillinger and Weber (SW). With the SW potential, F atoms do not mix into Si surfaces, creating instead a roughened surface with F on the outside. With the TB-HG potential, F atoms are able to mix into Si, leading to higher F uptake and Si etch rate in all cases. The TB-HG potential is compared to the modified SW potential of Weakliem et al (SW-WWC) in simulations of F⁺ etching of Si. The quantitative values of steady-state F uptake and Si etch rate for the (SW-WWC and TB-HG) potentials are nearly identical, but surface structure and etch product distributions are qualitatively different. Evidence of spurious energetic barriers in the SW potential form is given.