SURFACE CHARACTERIZATION OF GAAS AFTER THE REACTIVE ION ETCHING OF GEMOW OHMIC CONTACT IN RADIO-FREQUENCY SF6-O2 PLASMA

A characterization of monocrystalline GaAs surfaces after reactive ion etching of a GeMoW contact in SF6-O2 is presented. Scanning electron microscopy (SEM), monochromatized x-ray photoelectron spectroscopy (XPS), and Auger spectroscopy are used as means of investigation. Irregular 0.1 mum structures are observed by SEM on the surface while the XPS analysis reveals the existence of a gallium oxyfluoride superficial layer which composition is typically GaOF. Contributions in the As 2p and As 3d spectra at 1.8 eV with respect to As (GaAs) are identified as arsenic sulfides. Moreover, they have been localized on top of the GaAs substrate, and in the lowest part of the gallium oxyfluoride layer. An annealing at 800-degrees-C for 10 s partly removes the SEM observed structures which can be assigned to the As(x)S(y) and As2O3 species. The XPS analysis reveals the decomposition of the interface As-species when the temperature increases and the concomitant Ga-S bonds formation. Concurrently, the GaOF layer could be degraded by fluorine evaporation to yield a Ga2O3 oxide phase.