Optical emission spectroscopy studies in ECR plasma used for the deposition of silicon oxide film

The Optical Emission Spectroscopy (OES) is used as a diagnostic tool for analyzing the plasma spectrum of Electron Cyclotron Resonance Chemical Vapor Deposition (ECR-CVD) in solar silicon oxide thin film process. In this study, the correlation between spectrum variation trend and a-SiOx film properties will be discussed. The results reveal when the total flow rate and working pressure are fixed, the silicon oxide deposition rate can be interpreted by SiH* spectroscopy. On the premise that the bond energy of reaction species is lower than the bond energy of Si-O bond, the O* spectroscopy intensity tends to to be a positive correlation with oxygen content of thin film. Based on the above results, we can develop and use the database from plasma spectra corresponding to film properties, and the processing time required for optimization of silicon oxide process can be reduced significantly. In addition to the film properties, it is noted that a different and opposite finding compared with PECVD is that the photo-conductivity of a-SiO_x film increases and dark-conductivity decreases when microwave power augments. Finally, in 800W power, 200°C process temperaure and 5mTorr working pessure, it is found that the hydrogenated amorphous silicon oxide will transform to the crystalline phase when CO₂/SiH₄ ratio is less than 0.2 and H₂/SiH₄ ratio is greater than 10.