Computational thermodynamic study on CVD of silicon oxynitride films from Si–O–N–H and Si–O–N–H–Cl systems

High-throughput thermodynamic analysis of chemical vapor deposition of silicon oxynitride films from the Si–O–N–H and Si–O–N–H–Cl systems are performed based on the CALPHAD (CALculation of PHAse Diagram) approach. The considered deposition conditions are 800 °C, 200 Pa, NH3/SiH4 ratios of 0.05–50 and NH3/N2O ratios of 0.05–10. The influence of precursor composition on the phase and composition of the coatings as well as the optimal window for obtaining high-purity Si2N2O are discussed. The formation of SiO2 favors low NH3/N2O ratios and its fraction decreases with increasing NH3/N2O ratio. The content of Si2N2O increases monotonously with increasing NH3/N2O ratio until reaching 100 at.%. Free Si is suppressed to almost 0 at.% when the NH3/SiH4 ratio is greater than 1. The introduction of Cl in the precursor can not only reduce the formation of free Si but also expand the deposition window for preparing pure Si2N2O. Our calculated results agree well with available experimental data.