Optical emission spectroscopy diagnostic and thermodynamic analysis of thermal plasma enhanced nanocrystalline silicon CVD process
Nanocrystalline silicon is a promising alternative for the conventional crystalline silicon materials in the photovoltaic industry because of its better photostability and easy fabrication. However, the low deposition rates of conventional nanocrystalline silicon fabrication processes have hampered its application in industry. Thermal plasma has been used to successfully realize the high rate deposition of nanocrystalline silicon in this work. Optical emission spectroscopy (OES) diagnostic and thermodynamic equilibrium calculation are carried out to better understand the mechanism of deposition reactions and the effect of SiCl4 input rate on the nanocrystalline silicon deposition rate and product properties. Emission lines of atomic silicon, atomic hydrogen and atomic argon are observed. The results show that the amount of silicon related species in the gas phase is the main factor affecting the deposition process, which has a linear relationship with nanocrystalline silicon deposition rate, grain size and crystalline fraction at the high H2 dilution ratio of the deposition system.