Rapid thermal oxidation of epitaxial SiGe thin films

The oxidation of epitaxial thin Si1−xGex layers (0.06<x<0.30) at 1000 °C in dry O2, for times between 20 and 240 s, has been investigated. The analysis of the thin oxides (≈4–20 nm) has been performed using X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry. Although most of the Ge is found to pile-up at the oxide/Si1−xGex interface, our data indicate the formation of both SiO2 and GeO2 for all investigated samples and oxidation times. Moreover, the oxidation rate, enhanced with increasing the Ge concentration in the alloy, is reported. To our knowledge, this is the first experimental evidence of GeO2 formation and rate enhancement in the regime of high temperature oxidation in dry O2 and Si1−xGex alloys with x<0.5. The differences could be peculiar to the initial stage of oxidation, as well as to the rapid thermal process used in our case, but a clear answer is currently unavailable.