Gas temperature and surface heating in plasma enhanced chemical-vapour-deposition

The gas temperature in plasma enhanced chemical-vapour-deposition is a key parameter to determine the properties of deposited films because it influences gas-phase reactions of radicals and surface reactions of precursors. In this paper, we report the measurement results of the gas temperature determined from optical emission spectroscopy of molecular spectra and discuss heating of the growing surface of the film. It is found that the gas temperature linearly increases with the plasma density and the surrounding wall temperature. The surface heating is dominated by collisions with high-temperature gas molecules in a plasma generated at a high gas pressure condition. The measurements are performed in a hydrogen diluted silane plasma generated by very-high-frequency discharge under a high-rate growth condition of hydrogenated micro-crystalline silicon for photovoltaic applications.