Effects of Ions on Properties of a-Si:H Films Prepared by ECR Plasma CVD Method

Abstract

A study has been made on the effect of ions on the structural and electrical properties of a-Si:H films prepared by ECR plasma CVD method using H2, He and Ar as a plasma generation gas and SiH4. Deposition rates of over 10 µm/h can be achieved with H2 and He plasma, while Ar plasma generation attains half the deposition rates of H2 and He plasma. The increase of (SiH2)n chains in films is related to the reduced microwave power, increased pressure and positive DC bias voltage being applied to the substrates. The concentration of (SiH2)n chains dominates the photoconductivities. Films having the low concentration of (SiH2)n have ηµτ of 6×10-7 cm2/V after the depositions without substrate heating and 6×10-6 cm2/V after annealing at 280degC for 30 min. The energy transfer of incident ions to the film surface plays the most important role in obtaining highly photoconductive films.