Theoretical investigation of NH3 nitridation on Cl-terminated Si(100)-2 × 1 surfaces

Enhancing SiN deposition, particularly using NH₃ in atomic layer and chemical vapor deposition, is crucial for improving the performance of Si-based devices. However, while NH₃ nitridation on clean Si surfaces is well understood, its behavior on Cl-terminated Si surfaces remains largely unexplored. In this study, the mechanism of NH₃ nitridation on Cl-terminated Si(100)-2 × 1 surfaces is investigated using first-principles calculations and thermodynamic analysis. NH₃ reacts with Si–Cl on the surface with low reaction barriers, generating Si–NH₂ and gaseous HCl. Subsequently, Si–NH₂ forms a Si–NH–Si structure via NH₂ insertion into the Si–Si dimer bond and H migration onto the Si-dangling bond. Si–NH–Si formation is more favorable on the Si–Si dimer bond than on the Si–Si back bond. Thermodynamic analyses indicate that NH₃ nitridation leads to the Si–NH–Si structure, as Si–NH–Si formation is more thermodynamically stable than Si–NH₂ formation. Moreover, it is confirmed that the Si–NH–Si formation reaction is more favorable at higher temperatures and NH₃ partial pressures. These findings could potentially be used to improve SiN deposition processes and enhance the performance of Si-based devices.