Structure of thin polycrystalline silicon films on ceramic substrates

Abstract

The structure of polycrystalline silicon films with thickness of 10 μm, which were deposited by thermal chemical vapor deposition on ceramic substrates, was investigated. In this article we report results of silicon films deposited on SiAlON, mullite, and alumina substrates. The type of substrate strongly influences the stress and the texture of the films. In the silicon films deposited on SiAlON substrate tensile stress is observed, while in the films deposited on mullite and alumina substrates compressive stress is present. In all deposited films the observed stress is higher than the thermal stress, which has been determined from the differences in the thermal expansion coefficients of the film and substrate materials. We observe in the films grown on SiAlON substrate that the total stress decreases with increasing deposition temperature, which implies a reduction of the intrinsic stress in the films. We ascribe the reduction of the intrinsic stress to a lower defect formation at higher deposition temperature. The silicon films exhibit a preferential texture, which becomes more random at higher deposition temperatures. We also observe that at higher deposition temperatures the grain size is larger and the crystal growth is columnar. We propose that the observed structural coherence between the alumina substrate and the silicon film results in an epitaxial growth that is responsible for a good adhesion of the film to the substrate.