Oxidation of Ge implanted into SiO2 layers: Modeling and XPS

During annealing at 950°C in an oxidizing ambient, the redistribution of Ge in Ge+-implanted SiO2 layer is influenced by the germanium oxidation. Crystalline clusters precipitate immediately after sample heating. During the annealing an oxidation front proceeds into the layer, consuming crystalline clusters and leaving behind glassy precipitates barely visible by XTEM. Sputtering depth profiling in conjunction with the X-ray photoelectron spectroscopy (XPS) analysis was applied in order to identify the chemical state of both the precipitated Ge and that dissolved in the silicon dioxide matrix. For a reliable interpretation of the measured data, modeling of the physical processes involved in the depth profiling XPS technique was performed. It is shown that the depth profiling by ion beam sputtering causes collisional mixing of the subsurface region, which modifies the XPS signal. The results indicate possible improvement of the depth profiling XPS method to be used in future experiments.