On-line gas-phase optical diagnostics in plasma CVD deposition of carbon films

Space resolved, on-line spontaneous and stimulated emission, and CARS diagnostics have been employed on CH4/H2 mixtures excited by rf-discharge in order to investigate the chemical processes and the gas phase kinetics in the plasma. CH4 and H2 concentration and temperature have been monitored during the process as a function of main reaction parameters (rf-power, total pressure, CH4/H2 ratio). Formation of CH,H2, and H in excited states has been observed. On the basis of present spectroscopic data, a model for the gas-phase reactions accompanying the carbon film deposition is proposed.