Near-surface damage and mixing in Si-Cl2-Ar atomic layer etching processes: Insights from molecular dynamics simulations

Abstract

Silicon-chlorine-argon (Si-Cl2-Ar) atomic layer etching (ALE) is simulated using classical molecular dynamics (MD). The simulations provide a detailed view into the near-surface region during ALE processing. Bombardment of Ar+ ions creates a mixed amorphous region that significantly differs from the picture of ideal ALE. There is also a significant change in the Si etch yield and the etch product distribution as a function of Ar+ ion fluence. The Si etch yield is the highest at the beginning of the bombardment step but eventually decays to the physical sputtering yield. Atomic Cl and silicon chlorides are major etch products at the start of an ion bombardment step, but quickly decay. Atomic Si yields remain relatively constant as a function of Ar+ ion fluence. A new schematic of Si-Cl2-Ar ALE is presented in order to emphasize the complex behavior observed in MD simulations.