Spectroscopic-Ellipsometry Analysis of Si Films Prepared by RF Sputtering

Optical properties of Si films sputter-deposited on HF-treated (100)Si substrates have been investigated using spectroscopic ellipsometry in the 2.5-5.5-eV photon-energy range. Homoepitaxial Si films are grown at a high substrate temperature (∼410°C), while films deposited at lower temperatures show that they have polycrystalline (∼380°C) or amorphous structures (∼310°C). A linear regression analysis and a Bruggeman effective-medium approximation reveal that the homoepitaxial film has a few void networks in the film and a rough-surface overlayer of a few tens of Å. Polycrystalline and amorphous films are also found to contain a large number of void networks deep in the film mediums.