Epitaxial silicon thin films by low temperature aluminum induced crystallization of amorphous silicon

Epitaxial silicon thin films by low temperature aluminum induced crystallization of amorphous silicon were achieved in this effort. Two configurations were studied, cSi/a-Si/Al and c-Si/Al/a-Si. Evidences are given indicating the polycrystalline nature of the crystallized films using the first configuration. X-ray diffraction and transmission electron microscopy studies were used to study the crystal structure of the resulting films. The introduced results indicated that there is no preferred orientation of growth and the inability to produce epitaxial films using the first configuration.; In the second configuration, epitaxial silicon thin films were achieved on crystalline silicon substrates. The phenomenon of layer inversion was utilized in the process of epitaxy. (100) silicon wafers were used as the substrate and as the starting crystalline structure for the epitaxial thin film growth. A film of sputtered aluminum followed by a film of amorphous silicon by plasma enhanced chemical vapor deposition were deposited on the Si wafer. After annealing at 475°C (or higher) for 40 minutes or more, a continuous crystallized film of silicon was formed on the silicon substrate. Evidences are given to show that the crystallized silicon film is epitaxial in nature and well oriented with respect to the silicon substrate. Cross sectional transmission electron microscopy and selected area diffraction studies of the crystallized structure showed epitaxial nature of the thin film. Plane view scanning electron microscopy after etching aluminum showed a continuous film. Scanning electron microscopy in the cross sectional mode showed an indistinguishable interface between the substrate and the crystallized film. X-ray diffraction spectrum also indicated that the film has the same orientation as that of the substrate.; Auger depth profiling of layer inversion process indicated the formation of a Si/Al mixed phase within the first few minutes of annealing. Vertical and lateral modes of diffusion were found to take place during layer inversion. A proposed model of the process of layer inversion is presented in this dissertation. The model is based on the two modes of diffusion and on the lowest energy at which silicon adatoms adhere to the substrate and the already formed epitaxial portions of the film.