4460673 Method of producing amorphous silicon layer and its manufacturing apparatus

Abstract

Disclosed are method and apparatus for producing amorphous silicon layers for solar cells or electrophotography by plasma-enhanced chemical vapor deposition (CVD) through glow-discharge decomposition of a reaction gas containing monosilane or a higher order silicon hydride in a reaction chamber. Deposition rate and efficiency of reaction gas usage are improved by the selective removal of hydrogen gas reaction product from the reaction chamber. In one embodiment, a filter which is more permeable to hydrogen gas than to the reaction gas is placed in the vacuum pumping port of the reaction chamber. The filter comprises either a palladium film or a bundle of small diameter tubes made from a polyimide system polymer. In another embodiment of the invention, a porous sintered material containing La-Ni alloy is used to selectively adsorb hydrogen gas in the reaction chamber. In still another embodiment of the invention, a trap which collects reaction gas but passes hydrogen gas is used in the vacuum pump line connected to the chamber. The trap comprises a cell cooled to liquid nitrogen temperature for condensing the reaction gas but not the hydrogen. The collected reaction gas is recycled through the reaction chamber. The removal rate of hydrogen gas is controlled to maintain a desired hydrogen density in the reaction chamber, the hydrogen density being monitored by observing the intensity of hydrogen spectral lines in the glow discharge in the reaction chamber.