Effect of hydrogen plasma treatments at very high frequency on p-type amorphous and microcrystalline silicon films

Very high frequency (100 MHz) hydrogen plasma treatments on a-Si:H deposited by plasma enhanced chemical vapour deposition were studied. Ex-situ optical measurements have shown that etching and chemical transport occur as competing phenomena. The one that prevails is determined by the plasma conditions. In particular, very efficient chemical etching is observed for high H(2) flow rates, while, for low H(2) flow rates, the equilibrium is shifted toward deposition, and a structural modification of the sample is observed. The experimental conditions were stressed in the direction of utilizing chemical transport from the cathode to deposit very thin (7 nm) microcrystalline films with a pure H(2) plasma.