Atomistic insights into ion irradiation effects in plasma-enhanced atomic layer deposition of silicon nitride

Molecular dynamics simulations were performed to investigate the effects of low-energy N2+ ion irradiation on nitridation and chlorine (Cl) removal from silicon (Si) and chlorinated Si surfaces, motivated by the question of the extent to which ion irradiation contributes to Cl removal during the second half-cycle of plasma-enhanced atomic layer deposition (PEALD) of silicon nitride films. The simulation results show good agreement with previous ion beam experiments conducted under comparable conditions [T. Ito, et al., Jpn. J. Appl. Phys. 61, SI1011 (2022)]. While energetic N2+ ion impacts can promote surface nitridation and remove chemisorbed Cl atoms, collision cascades also drive Cl atoms into subsurface regions, leading to significant Cl implantation. These findings highlight the dual role of ion irradiation in PEALD and demonstrate the value of atomistic simulations for elucidating subsurface processes not readily accessible by experiment.