Evidence of swelling of SiO2 upon thermal annealing

Ultrathin SiO2 film was thermally grown on Si(001) substrate by dry oxidation and wet oxidation processes. The films were then subjected to thermal annealing (TA) at 1000 degreesC for 30 min. The structural characterization of the as-grown and the TA samples was carried out using the grazing incidence x-ray reflectivity technique. The analysis of the x-ray reflectivity data was carried out by using a model independent formalism based on the distorted wave Born approximation for obtaining the electron density profile (EDP) of the film as a function of depth. The EDP of both films show a decrease in the electron density as well as an increase in their thickness when the films are subjected to TA. It has also been observed that the total number of electrons is conserved in the oxide film after TA. Our analysis of the x-ray reflectivity data indicates that the SiO2 film swells and its interface with the substrate modifies upon TA. (C) 2002 American Institute of Physics.