Molecular dynamics simulations of Si etching by energetic CF⁺₃

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 CF⁺₃ using molecular dynamics (MD) simulations is demonstrated. Aspects of CF⁺₃ 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 Si_xC_yF_z. 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 CF⁺₃ 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.