Amorphous silicon deposition rates in diode and triode discharges

Abstract

The relative rates of radical deposition on discharge electrodes and substrate surfaces are calculated for two-and three-electrode discharges. The reaction rate, diffusion coefficient, screen-electrode transparency, and surface sticking coefficient are parameters in the general solution. The parameters are then chosen to describe typical silane discharges used for a-Si:H photovoltaic production, and the effect of screen transparency and other parameters on substrate deposition rates is evaluated. We then show that a measurement of deposition rate versus screen–substrate spacing in a three-electrode discharge has been misinterpreted as due to gas reactions, whereas it is primarily due to screen deposition. Finally, we note some possibilities for measuring deposition parameters and for varying the mix of depositing species.