Vacuum-Ultra-Violet and Ozone Induced Oxidation of Silicon and Silicon-Germanium

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Abstract
UV radiation has been used to induce low temperature oxidation of crystalline silicon (c-Si) surfaces and silicon-germanium (Si-Ge) strained layers on Si. For c-Si at 550°C, growth rate enhancements of up to 50 times the dry thermal oxidation rate are achieved, equivalent to what is normally only obtainable thermally at 900°C. When irradiated under identical conditions by the UV light, SiGe layers were found to oxidise two times faster than c-Si. Prolonged oxidation of SiGe produced a dielectric structure consisting of a pure SiO2 film on top of a SiO2 layer containing several percent of trapped Ge, with the remaining SiGe layer snow-ploughed at the Si interface but retaining its epitaxial structure. Simple modelling qualitatively explains the observed features of the silicon oxidation and has led to further studies of ozone oxidation of c-Si.