Plasma assisted oxidation of SiGe layers at 500°C: interface characterization

In this paper, we investigate the germanium behaviour during the low temperature plasma assisted oxidation of strained epitaxial Si1−xGex (x = 0.05, 0.1 and 0.2) layers. For an oxidation temperature of 500°C and an oxide thickness between 80 and 350 Å, using Auger depth profiling, we find that the oxidation process leads to the formation of a pure SiO2 top layer and the rejection of Ge at the oxide/alloy interface. Taking into account in a suitable way the broadening effects affecting the Auger profiles, we show that a pure Ge layer is formed at the interface. For longer oxidation times, this interfacial layer reaches a ‘critical’ thickness which is found to be independent of the germanium concentration of the SiGe substrate. Then, some germanium atoms begin to be embedded in the SiO2 layer before starting to be oxidized.