Initial Stages of Etching of the Si{100}(2×l) Surface by 3.0-eV Normal Incident Fluorine Atoms: A Molecular Dynamics Study

Etching of the dimer reconstructed silicon surface with an initial coverage of a monolayer of fluorine by 3.0-eV fluorine atoms at normal incidence has been examined with molecular dynamics. In the simulation, fluorine adsorption and product etching occur at the top of two atomic layers of silicon, which are exposed to the vacuum. We have identified mechanisms responsible for the gas-phase products SiF₄ and Si₂ F_x, where x = 5 and 6. In addition, we have simulated a near-steady-state etched surface where the majority of the adspecies are monofluorinated species with a significant amount of difluorinated and trifluorinated species. Observed fluorosilyl towerlike structures are found to be important to the etching of the Si₂ F_x species, and they also provide insight as to the possible structure of the adlayer formed on silicon samples after long time exposure to XeF₂.