Irregular Au profile on the SiO2 surface and at the SiO2∕Si interface and the oxidation kinetics of thermally oxidized Au-contaminated n-Si (001) surfacesa)

The authors have studied the Au profile near the SiO2∕Si interface as a function of oxidation temperature and clarified the oxidation mechanism. Clusterlike Au granules were observed on the surface of the SiO2 film (the Au surface concentration was 1.7×1015at.∕cm2) of thermally oxidized Au-contaminated Si wafers, oxidized between 823 and 1123K. As the oxidation temperature was increased, the Au granular clusters grew competitively. The clusters were observed to be both on the surface of the SiO2 film and at the SiO2∕Si interface. The Au clusters were found not to bond with other elements such as O, H, and Si. The existence of a depleted or weakly inverted layer at the Si surface indicated the formation of a Au∕n-Si Schottky barrier. Regarding the oxidation kinetics between 823 and 1173K, Au rapidly enhances the growth rate of SiO2 (for SiO2 thicknesses of less than ∼10nm). This result shows that Au acts as a catalyst to promote the initial growth of SiO2 on Si (001) surfaces.