The Formation and Devitrification of Oxides on Silicon

The thermal oxidation of silicon in various gaseous atmospheres has been studied and the growth rate data and activation energies determined. The oxide layers contained defects, the density of which increased with increasing temperature and time; microcracks were also observed. The devitrification of these oxides was studied at 1300 degrees C and above in argon-oxygen atmospheres; water vapour was found effectively to catalyse the process. Sections of the devitrified oxide were prepared and examined with an electron microscope and electron diffraction patterns recorded. The latter exhibit a probable cubic structure, cell size 8.16 angstrom, which does not correspond to any published structure of crystalline silica. The formation of a "rosette" structure was also observed and was probably a stress-relief phenomenon. The origin of the rosette structure was traced to the Si-SiO2 interface and revealed by controlled removal of the oxide layer.