Abstract
The purpose of this study is to investigate the influence of the plasma property on the thin film property in plasma enhanced chemical vapor deposition (PECVD) processes which are employed for deposition of silicon based thin film. This study includes both experimental and simulation analysis. Experimentally, optical emission spectroscopy was employed for analysis in PECVD plasma discharge for a-SiGe:H films. Correlations between the variation of the intensities of the characteristic emissions of the gaseous species important for the film deposition and properties. On the other hand, numerical simulation using fluid model was also conducted for analysis of capacitively-coupled SiH4/H2 plasma discharges operated at very high frequencies (VHF) for deposition of a-Si:H film which was used in the HIT solar cells. In simulation study, the effect of silane depletion and higher silane species under different process parameter (power, pressure and silane flow rate). Experiment shows OES-ratio Si/Ge shows the same trend with film bandgap and photosensitivity. It means OES-ratio Si/Ge exists strong correlations to the silicon/germanium content in the film. Besides, OES-ratio Si/SiH and OES-ratio Hβ/Hα can be used to analysis electron temperature in the plasma. But these two OES ratio show the abnormal variation as power/silane flow rate are varied. However, when pressure and germane flow rate increases, then OES-ratio Si/SiH and OES-ratio Hβ/Hα will descend. Finally, H2 emission intensity can be used to analysis electron density of plasma. H2 emission intensity doesn’t have trend to follow as pressure is varied. But in the others process condition, H2 emission intensity increases with power, it means higher electron density in the plasma. On the other hand, electron density descend when the total gas flow rate increases. So OES analysis method can be used to know the variation of film bandgap and plasma property under different process parameter. In simulation studies, silane depletion and higher silane species flux ratio increase with power due to SiH2 number density increase acutely. In addition, silane depletion and higher silane species flux ratio have a opposite trend as pressure/silane flow rate are varied.