Effect of deposition rate on the scaling behavior of microcrystalline silicon films prepared by very high frequency-plasma enhanced chemical vapor deposition

Abstract

Three sets of hydrogenated microcrystalline silicon （μc-Si:H） films for different deposition time were prepared by very high frequency-plasma enhanced chemical vapor deposition with different deposition rates. The surface roughness evolution of μc-Si:H has been investigated using spectroscopic ellipsometry. For films with the deposition rate of 0.08 nm/s and 0.24 nm/s, the surface roughness of films changes a little, and the growth exponent β is about 0.20. Similar β values ascribed to the adatoms have enough time to move to the site with lower energy under lower deposition rate. However, when the deposition rate increases to 0.66 nm/s, the surface roughness of films increases obviously, and the exponent β is about 0.81, which is much higher than 0.5 for zero diffusion limit in the scaling theory. The growth mode of high-rate deposited μc-Si:H is clearly different from that of lower-rate deposited μc-Si:H. This is due to the fact that the adatoms have no enough time to diffuse before being covered by the radicals of the next layer under high deposition rate, which decreases the surface diffusion of the adatom, and therefore increases the film surface roughening which results in a larger β. The case of β>0.5 is related to the shadowing effect.