Dry oxidation of MBE-SiGe films: rate enhancement, Ge redistribution and defect injection

In this paper we compare dry oxidation, at different temperatures and oxidation times, on epitaxial SiGe films and Si reference samples. Rapid and conventional furnaces and several analysis techniques, such as Rutherford backscattering spectrometry, transmission electron microscopy and secondary ion mass spectroscopy, have been used to process and characterize our samples. We focused the attention on the thin oxide regime (3-30 nm), pointing out substantial differences between Si and SiGe in the oxidation kinetics and point defect injection. In fact, SiGe films show an oxidation rate enhancement with respect to Si, previously reported by other groups only for wet ambient. The enhancement, however, decreases with temperature and oxide thickness. From our data we estimated the activation energies for Si and SiGe oxidation in our range of thickness. We also show that Ge segregates behind the oxide forming a Ge-rich layer, free of extended defects. Finally, the study of the broadening of thin boron spikes, introduced in some of our samples, has allowed us to measure the interstitial injection during the oxidation and to demonstrate that it is strongly reduced in the case of SiGe samples.