SYNCHROTRON-RADIATION-INDUCED MODIFICATION OF SILICON DIOXIDE FILM AT ROOM-TEMPERATURE

Thermally grown SiO2 films were irradiated by synchrotron radiation at room temperature and changes in film properties were analyzed to clarify the irradiation effects and explain the mechanism of the photo-stimulated desorption (PSD) of SiO2. The irradiated SiO2 was chemically weakened throughout the film of 89-nm thickness by Si-O bond breaking following core electron excitation. The broken bonds were recombined by postannealing at 850-degrees-C. The irradiated surface was deoxidized by oxygen desorption and the remaining Si-rich layer was evaporated by postannealing over 700-degrees-C. Results indicate that irradiation effects are bond breaking and the desorption of oxygen and that thermal effects are the recombination of broken bonds and the evaporation of the deoxidized layer. It is supposed that the PSD of SiO2 at elevated temperature consists of photo-desorption of oxygen and thermal evaporation of SiO.