Stress in chemically vapour-deposited silicon films

Abstract

Stress in silicon films was investigated by X-ray diffraction. Films 0.5–0.6 microm thick were deposited onto single-crystal silicon substrates covered with thermally grown amorphous SiO 2. The investigations were carried out for films deposited over the temperature ranges 500–800°C in a nitrogen atmosphere and 650–1070°C in hydrogen. The influence of the volume ratio of silane to carrier gas on the stress in the silicon films was also examined. All the silicon films were compressively stressed but the stress was not a linear function of the substrate temperature. The experimental data indicate that the structure of the film and the type of preferred orientation have a marked influence on the film stress. The most stressed films were those with an amorphous structure and those with 〈110〉 preferred orientation, irrespective of the atmosphere in which the films were deposited. The least stressed films were randomly oriented polycrystalline and the stress in these decreased as the substrate temperature was increased.