Low-energy ion irradiation effects on chlorine desorption in plasma-enhanced atomic layer deposition (PEALD) for silicon nitride

Precise control of silicon nitride (SiN) film quality is required for SiN plasma-enhanced atomic layer deposition (PEALD) processes. In this study, we examined the interactions of SiCl4 adsorbed Si surfaces with incident ions in the desorption/nitridation half-cycle of typical SiN PEALD with nitrogen plasma irradiation. Reactions of low-energy ion beams with Cl-terminated Si surfaces were investigated with in situ X-ray photoelectron spectroscopy. It was found that N-2 (+) ion injection in the incident energy range of 30-100 eV formed a SiN x (x approximate to 1.33) layer on a Cl-terminated Si surface at room temperature. It was also confirmed that, although low-energy ion injection tends to remove Cl atoms from the surface, some Cl atoms are pushed into a deeper layer by knock-on collisions caused by incident ions. This observation indicates that the complete removal of Cl atoms from the surface by N-2 (+) ion irradiation only is not feasible.