Surface effects in quasiatomic layer etching of silicon

The current investigation explores the surface effects of quasiatomic layer etching (Q-ALE) of silicon (Si), focusing on the interplay of process parameters, such as Ar+ ion energy, and their impact on etch rate, surface roughness, and material damage. Using a chlorine-based reactive ion etching tool at varying radio frequency bias voltages, the ion energy distribution and etching characteristics were systematically analyzed. Experimental results demonstrate the existence of an ALE process window at 50–70 eV Ar+ peak ion energy, achieving an etch-per-cycle of ∼0.12 nm with minimum surface roughness and damage. Outside this window, higher ion energies led to increased surface roughness of the etched Si. Ellipsometry and atomic force microscopy revealed that the amorphous Si layer resulting from Ar+ ion bombardment was limited to ∼0.6 nm under optimal conditions. These findings provide insights into optimizing Q-ALE processes for precise and controlled Si etching, enabling advancements in nanoscale device fabrication.