Formation of epitaxial Si1−xGex films produced by wet oxidation of amorphous SiGe layers deposited on Si(100)

Abstract

Epitaxial SiGe/Si structures have been formed by wet oxidation of amorphous SiGe films. Amorphous, 1000-Å-thick Si0.86Ge0.14 films were electron beam evaporated onto RCA cleaned Si(100) substrates at a background pressure of 1×10−7 Torr. They were then wet oxidized in an open tube furnace, at 900 °C for various times. They have been examined by reflective high-energy electron diffraction and Rutherford backscattering. Results indicate the formation of an epitaxial SiGe layer following the oxidation, whereas a polycrystalline layer forms following a vacuum or nitrogen ambient anneal. It is suggested that the oxide contamination at the amorphous SiGe/Si interface is too high to allow solid phase epitaxial growth to occur in an oxygen-free ambient, but during the oxidation process, some native oxide is dissolved due to a gradient of silicon from the substrate to the growing SiO2 on the surface. This allows grains of the SiGe alloy to orient with respect to the substrate, and secondary grain growth occurs during the oxidation process.