CHALLENGES IN THE OXIDATION OF STRAINED SiGe LAYERS

摘要

The use of ultraviolet (UV) and vacuum ultraviolet (VUV) photons generated from low pressure Hg lamps and excimer lamps, respectively, to enhance the growth of ultrathin dielectrics films on SiGe strained layers and on Si at temperatures below 550 °C is described in this paper. The thickness, structure (composition) and electrical properties of the grown oxide layers were investigated by ellipsometry, Raman and electron spectroscopy, scanning and transmission electron microscopy, Rutherford backscattering, Fourier-transform IR spectroscopy, capacitance-voltage and current-voltage measurements in order to characterise the oxidation process. The use of the UV and VUV radiation during the oxidation resulted in significant enhancements of the growth rate when compared with thermal oxidation, especially for the novel excimer lamp sources, which are more powerful light sources than Hg lamps. Using this technique, high quality, stoichiometric SiO_2 layers were grown on Si or Si capped SiGe strained layers, without any measurable relaxation of the strained substrate. New effects such as the formation during the UV-assisted oxidation of SiGe samples of nanocrystalline Ge particles inside the grown oxide layer which exhibit visible photoluminescence and stress effects induced by the oxidation process are also presented.