Molecular dynamics simulation of atomic layer etching of silicon

A molecular dynamics study of 50 eV Ar⁺ ion bombardment of a Si(100) crystal with a monolayer of adsorbed chlorine was conducted to simulate atomic layer etching (ALET) of Si. The total reaction yield (Si atoms removed per ion) was 0.172; 84% of silicon was removed as SiCl, 8% as elemental Si and 8% as SiCl₂. Based on the total yield, an ion dose of 1.16×10¹⁶ ions/cm² is necessary to remove one monolayer of silicon. Reaction occurs during the ps time scale of the ion–solid interaction. Long time‐scale chemistry (100s of ms) which is possible in ion‐assisted etching with simultaneous exposure to neutral and ion beams does not happen in ALET. It was further found that 93% of Si originated from the top silicon layer and 7% from the layer underneath. In addition, some structural ‘‘damage’’ was induced to the top three silicon layers. It appears that perfect ALET of silicon is not possible for an ion energy of 50 eV.