Mechanical stress in thin a-Si:H films

PL Study Of mechanical stress is carried out for a-Si:H films deposited at different substrate temperatures and using plasma-enhanced chemical vapour deposition from hydrogen-diluted silane. The film thickness has been varied in the range of 150-600 nm. A dependence of compressive intrinsic stress on film thickness has been observed for films deposited at substrate temperatures ranging from 180 to 270 degreesC. In films deposited at 150 degreesC stress distribution is uniform. Linear stress profiles are established in films deposited at higher temperatures, provided that during the growth of surface layers no structural or compositional changes proceed in the bulk of the film. The compressive stress increases in the direction from the interface to the film surface. The observed nonuniformity across the film thickness is discussed.