X-Ray Photoelectron Spectroscopy of SiO2–Si Interfacial Regions: Ultrathin Oxide Films
by S. I. Raider, R. Flitsch
The composition and width of the interfacial region formed between thin thermally-grown oxide films and single-crystal Si substrates were nondestructively characterized by means of x-ray photoelectron spectroscopy. Data obtained from variations in core-level binding energies, from variations in photoelectron line intensities, and from variations in photoelectron linewidths indicate the presence of a nonstoichiometric oxide-Si transition region. The composition and width of this region are dependent upon substrate orientation, but are invariant with change in other oxidation processing parameters. Transition regions formed on <100> oriented substrates are narrower and more completely oxidized than those formed on <111> oriented substrates. Although both Si–Si bonds and SiO–Si groups are present in this nonstoichiometric region, they do not appear to be a mixture of Si and SiO2. Instead, a continuous distribution of Si tetrahedra, Si–(O)x(Si)4−x, are formed, in which x changes from 0 to 4 as one proceeds from the substrate to the stoichiometric SiO2 film.