Oxidation of Si1−xGex Alloys at Elevated Pressure

Abstract

ABSTRACTThermal passivation of Si1−xGex (x=10 at.%) using dry high pressure (>700 atm) and hydrothermal (>500 atm) oxidation (HPO) was studied. Alloys of Si1−xGex approximately 200 nm thick were oxidized using three processes: (i) dry oxygen at 700 atm and at a temperature of 550°C, (ii) hydrothermal at 510 atm and 550°C, and (iii) conventional 1 atm at 800°C. Auger sputter depth profiling (AES), X-ray photoelectron spectroscopy (XPS), and Raman Spectroscopy were used to characterize the oxides. AES and Raman studies reveal that both dry high pressure and hydrothermal oxidizing conditions produce compositionally congruent oxides from Si90Ge10, multicomponent alloys. XPS studies were used to establish that the Ge in these oxides is chemically incorporated. Thermodynamic and kinetic considerations of the Si-Ge-O system are discussed for both HPO and conventional oxidation. The metastable nature of the HPO oxides is confirmed by examining the microstructure of annealed oxides.