Effects of SiH2Cl2 Addition on the Growth Mechanism of Si Films Prepared by Photochemical Vapor Deposition

Abstract

ABSTRACTEffects of SiH2Cl2 and H2 addition to SiH4 on photochemical vapor deposition (photo-CVD) of amorphous Si (a-Si) and epitaxial Si films were investigated, and roles of Cl and H in the growth mechanism were discussed. The surface morphology and the defect density of the obtained a-Si films were evaluated by atomic force microscope (AFM), and constant photocurrent method (CPM), respectively. It was found that the H2 dilution of SiH4 is effective to prepare the a-Si films with smooth surfaces and low defect density. Furthermore, nearly flat surface with the root mean square (RMS) of the roughness of 0.35nm was obtained by the SiH2Cl2 addition to H2-diluted SiH4. In the Si epitaxy, the SiH2Cl2 addition is also efficient to improve the film quality. It is suggested that the growing surface is terminated by both Cl and H, and the surface is more stable than that terminated by only H. Therefore, the diffusion on the growing surface of the film precursors such as SiH3 is enhanced, resulting in the improvement of the surface morphology and the film quality.