Crystallization of amorphous silicon films during low pressure chemical vapor deposition

The crystallization of low pressure chemical vapor deposition amorphous silicon films was studied by transmission electron microscope observations. The results demonstrate the interdependence of the silicon deposition rate, the incubation time for nucleation, and the crystalline growth rate. At temperatures below 600 °C the deposited films are amorphous, but partial crystallization can occur the deposition time is longer than the incubation time. Crystallization occurs through an epitaxial-like growth from nucleates near or at the substrate interface; the crystalline phase will reach the depositing interface for thick films if the growth rate exceeds the deposition rate. The crystallized fraction of the deposited layer can be controlled by regulating the deposition temperature and rate and by in situ addition of dopant impurities. At temperature higher than 600 °C the deposited films are polycrystalline and columnar in structure. The surface texture is much smoother for films whose surfaces are amorphous.