The thermal oxidation kinetics of Si with dry oxygen was investigated by X-ray and ultraviolet photoelectron spectroscopy. The SiO desorption was found to be maintained for a while even after the oxide growth during initial oxidation. By the annealing of thick oxides in O2, the oxidation of SiO molecules in SiO2 was verified more straightforwardly. Further, it was observed that the decomposition kinetics are closely concerned with the SiO2/Si strained interface at 730°C, suggesting that the point defect produced by the strain is responsible for the SiO formation. Based on the observations, a unified thermal oxidation model is proposed, in which oxidation and decomposition always take place simultaneously by vacancies and Si self-interstitials due to point defect generation at the interface, respectively, in addition to the oxidation of SiO by O2 permeating into SiO2. It is pointed out that SiO molecules are so unstable that they diffuse through the repeated exchange reaction of SiO with SiO2. Although SiO can be oxidized under O2 in SiO2, SiO would desorb from the SiO2 surface when the O2 pressure is too low and in vacuum, leading to the removal of oxide. By the use of the present unified model, one can interpret successfully the 18O profile measured by SIMS for the oxidi reoxidized with 18O2 isotope [J.A. Costello and R.E. Tressler, J. Electrochem. Soc. 131 (1984) 1944] and the initial rapid oxidation below 300 Å.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry