Surface chemistry associated with plasma etching processes

We present our progress towards an accurate simulation model of plasma etching of silicon. A study of the interactions of energetic argon ions with silicon surfaces using molecular dynamics (MD) simulations is reported. A dynamic balance between ion-induced damage and recrystallization of the surface is detected. By manipulating ion energy, argon ions are able to both create disordered regions near the surface, and recrystallize these disordered regions. Silicon atoms in this amorphous region are readily mixed by argon ions. Limited mixing in the crystalline layer is observed. Fluorine adsorbed on the silicon surface does not mix into the layer with argon ion impact. When an energetic F+ impacts a silicon surface, the uptake and apparent sub-surface mixing of F is much greater than Ar+-induced mixing. However, a closer examination shows that the F impacts have primarily increased the Si surface area by creating crevices and cracks, and that the F remains mainly on the surface of this layer. A similar situation results when SiF3+ impacts the surface.