Deposition pressure effect on the surface roughness scaling of microcrystalline silicon films

The scaling behaviour of surface roughness evolution of microcrystalline silicon （/zc-Si：H） films prepared by very- high frequency plasma-enhanced chemical vapour deposition （VHF-PECVD） has been investigated by using a spectroscopic eHipsometry （SE） technique. The growth exponent β was analysed for the films deposited under different pressures Pg. The results suggest that films deposited at Pg = 70 Pa have a growth exponent β about 0.22, which corresponds to the definite diffusion growth. However, abnormal scaling behaviour occurs in the films deposited at Pg = 300 Pa. The exponent β is about 0.81 that is much larger than 0.5 of zero diffusion limit in the scaling theory. The growth mode ofμc-Si：H deposited at Pg = 300 Pa is clearly different from that of μc-Si：H at Pg = 70 Pa. Monte Carlo simulations indicate that the sticking process and the surface diffusion of the radicals are two key factors to affect the growth mode under different pressures. Under Pg = 300 Pa, β〉 0.5 is correlated with the strong shadowing effect resulting from the larger sticking coefficient.