THERMAL-OXIDATION OF OUTDIFFUSING SIO WITH PERMEATING O-2 IN A SIO2 FILM STUDIED BY ANGLE-RESOLVED X-RAY PHOTOELECTRON-SPECTROSCOPY

During annealing in vacuum and dry O-2, the amount of suboxide, Theta( s) in the 1000 Angstrom SiO2 films on Si(111) was measured as a functi on of the annealing time by angle-resolved X-ray photoelectron spectro scopy (ARXPS). From ARXPS spectra of Si 2p taken at two polar angles o f 0 degrees (bulk sensitive) and 75 degrees (surface sensitive), it wa s clarified that during annealing in vacuum, Theta(s) increases with t ime underneath the surface more largely than on the surface, but annea ling in O-2 atmosphere at 0.5 Torr reduces Theta(s) on the surface mor e significantly than uncerneath the surface. These indicate that SiO m olecules outdiffusing from the SiO2/Si interface are oxidized by perme ating O-2 in the SiO2 films.