Microstructural and optical properties of as-deposited LPCVD silicon films

Silicon thin films were deposited by low-pressure chemical vapor deposition (LPCVD) on oxidized silicon substrates, from silane decomposition. The dep osition temperatures used in our experiment have been 500, 530, 550, 590 an d 615 degreesC and the pressure values were 20, 53 and 100 Pa. The microstr ucture and the surface roughness of as-deposited films were investigated by X-ray diffraction (XRD), spectroelipsometry (using the Bruggemann-Effectiv e Medium Approximation with a multilayer model) and AFM techniques. Three d ifferent models, Tauc, Cody and Wemple-Di Domenico were used to estimate th e values of the optical gap. The results show the influence of the microstr ucture on the physical and optical properties of as-deposited LPCVD silicon films. It is pointed out that polycrystalline silicon thin films can be ob tained by the LPCVD technique below 550 degreesC. (C) 2001 Elsevier Science B.V. All rights reserved.