Defect-Mediated Atomic Layer Etching Processes on Cl-Si(100): An Atomistic Insight

Defects play a significant role in atomic layer etching (ALE) processes; however, a fundamental understanding at the atomic level is still lacking. To bridge this knowledge gap, this study investigated the role of point defects in the laser-induced ALE of Cl-Si(100) using density functional theory (DFT) and real-time time-dependent DFT calculations. In the calculations, both the pristine surface and the defective surface were considered for comparative analysis. The key finding is the enhanced desorption of SiCl molecules, facilitated by point defects under laser pulse irradiation. The presence of point defects was found to effectively reduce both the desorption energy barrier and the laser intensity threshold required for desorption. Additionally, extra defective levels within the band gap were observed through the density-of-state diagram. Based on these findings, a defect-mediated etching regime was proposed to elucidate the layer-by-layer etching process. This study provides atomistic insight into understanding the role of defects in laser-induced ALE processes. The presence of point defects can enhance the etching selectivity between the topmost layer and the underlying layers, thereby contributing to highly efficient and damage-free etching processes through the defect-mediated etching mechanism.