SURFACE-ROUGHNESS EVOLUTION IN THE GROWTH OF A-SI-H THIN-FILMS STUDIED BY ELLIPSOMETRY

In situ real time ellipsometry at 3.4 eV photon energy has been used to analyze the deposition of hydrogenated amorphous silicon (a-Si:H) thin films obtained by RF glow discharge decomposition of silane gas. The study is focused on the evolution of the microstructure during the films growth. The results are explained considering a theoretical model which assumes a homogeneous growth of the a-Si:H below a surface roughness layer which increases 0.5-0.7 nm in thickness during the first 400 nm of film growth. The bulk layer microstructure appears to be homogeneous within 1% of density variations.