Plasma parameter measurements and deposition of a-Si:H thin films in pulsed ECR plasma.

Pulse modulation of the incident microwave power was investigated for the control of plasma parameters and improvement of the films deposited in ECR plasma. Measurements of the temporal variation of plasma parameters in the pulse-modulated ECR plasma indicate that the electron density varies little in time while the electron temperature decreases rapidly within 10 μs after the discharge. The results suggest that pulse modulation where the power-off period is approximately 10 μs enables reduction of the mean electron temperature while keeping a high electron density. Furthermore, we have prepared hydrogenated amorphous silicon films by the ECR plasma CVD method. It was found that the ratio of photoconductivity to dark conductivity of the film was improved from 103 to 2.5×105 without heating the substrate and the deposition rate was 14 Å/s by pulse-modulated ECR plasma.