Molecular Dynamics Simulation of Si Etching by Off-Normal Cl+ Bombardment at High Neutral-to-Ion Flux Ratios

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Molecular dynamics simulations of Si etching using chlorine-based plasmas including both high-energy ($=100$ eV) Cl+ ions and low-energy neutral Cl radicals with a high neutral-to-ion flux ratio ($=\eta$) have been performed. The ion angular dependences of the etch yield, stoichiometry, and translational kinetic energies of etch products as well as the atomic distribution in the reaction layers were analyzed. For the plasma etching condition ($\eta=100$ in this paper), total Si yield monotonically decreased as Cl+ incident angle ($=\theta_{\text{i}}$) increased, which agreed with experimental results obtained using Cl2 plasmas by Vitale et al. On the other hand, for beam etching without radicals, the yield curve was a typical physical sputtering curve with a maximum near $\theta_{\text{i}}=60$°. This indicated that a relatively large number of Si atoms were sputtered physically from the unsaturated surface. Our numerical technique could replicate etching characteristics including the effect of neutral radicals.
2008-11-25