Chemical Vapor Deposition of a-Si:H Films Utilizing a Microwave Excited Ar Plasma Stream

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Abstract
A Microwave-excited Ar-plasma stream produced at low gas pressures (10-4 to 10-2 Torr) was applied to a preparation of hydrogenated amorphous silicon films made from SiH4. The electric and optical properties of the films were investigated as functions of the deposition conditions. The film properties greatly depended upon the substrate temperature and the deposition pressure and slightly upon the microwave power. The conductivity of the films prepared at 200°C and at pressures ranging between 0.6 and 0.8 mTorr were about 5×10-10 S·cm-1 in the dark and 4×10-4 S·cm-1 under AM 1.5 illumination. The films prepared at the lower pressures were porous and contain a large amount of gases; the films prepared at higher pressures were deteriorated in the same way as those prepared by an RF glow discharge from Ar-diluted SiH4.