An in situ and ex situ ellipsometry comparison of the interfaces of Si and GaAs resulting from thermal and plasma oxidation

A combination of in situ spectroscopic ellipsometry (SE) and real time ellipsometry (RTE) along with ex situ spectroscopic immersion ellipsometry (SIE) measurements were performed in order to compare the Si and GaAs-oxide interfaces produced by thermal and electron cyclotron resonance (ECR) plasma oxidation processes. Our studies indicate that the two oxidation methods yield different kinetics for Si and GaAs. RTE reveals that ECR plasma oxidation shows an initial stage of fast growth independent of substrate bias, up to a few nanometers; then the oxidation slows down and becomes bias-dependent. Substrate bias has a similar effect on Si and GaAs, even though more pronounced for GaAs. For GaAs, we also observed a strong effect of the doping on the kinetics of ECR plasma oxidation. For thermal oxidation of GaAs, a substrate orientation effect was found, in contrast to ECR plasma oxidation of semi-insulating substrates which shows no strong substrate orientation effect. Similarly, the strong orientation dependence of the initial Si oxidation kinetics for thermal oxidation disappears for ECR plasma oxidation of Si. Our SE results show that the GaAs oxides obtained from the two oxidation processes are different, and these findings were correlated with X-ray photoelectron spectroscopy (XPS). SIE studies were performed to compare the interfacial region of oxides obtained with different processes.