Thermal oxidation of outdiffusing SiO with permeating 0, in a SiO, film studied by angle-resolved X-ray photoelectron spectroscopy

During annealing in vacuum and dry O, the amount of suboxide, @?, in the 1000 A SiO, films on Si( 111) was measured as a function of the annealing time by angle-resolved X-ray photoelectron spectroscopy (ARXPS). From ARXPS spectra of Si 2p taken at two polar angles of 0” (bulk sensitive) and 75” (surface sensitive), it was clarified that during annealing in vacuum, 0, increases with time underneath the surface more largely than on the surface, but annealing in 0, atmosphere at 0.5 Torr reduces 0, on the surface more significantly than underneath the surface. These indicate that SiO molecules outdiffusing from the SiO,/Si interface are oxidized by permeating 0, in the SiO, films.