Formation of Germanium Dioxide During Wet Oxidation of Si 0.5 Ge 0.5 Alloy
- PDF / 393,678 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 53 Downloads / 156 Views
FORMATION OF GERMANIUM DIOXIDE DURING WET OXIDATION OF Si0.sGe0 .5 ALLOY J.P. ZHANG, P.L.F. HEMMENT*, R.A. KUBIAK** and E.H.C. PARKER** * Department of Electronic and Electrical Engineering, University of Surrey, Guildford, Surrey GU2 5XH, UK "**Department of Physics, University of Warwick, Coventry CV4 7AL., UK ABSTRACT The oxidation of Si 0.5Ge 0.5 alloy has been investigated over the temperature range 800 to 1000'C. The composition of the oxide layers has been determined by 1.5 MeV Rutherford backscattering spectroscopy (RBS), infrared transmission spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS). During the initial stage of oxidation, as the temperature ramps up in an oxidising ambient both Si and Ge are oxidized to form a mixed oxide in the region near the surface. Upon further oxidation, at temperatures higher than 900'C and times longer than 5 minutes, the Ge atoms are ejected by the growing oxide layer, which has the composition of SiO 2 , and accumulate in the underlying alloy, which becomes rich in Ge.The surface oxide layer remains unchanged. The proportion of GeO 2 in the near surface region, determined from IR spectra, decreases when the temperatures increases firom 800'C to 1000 0 C. It is concluded that at 800'C Ge atoms are insufficiently mobile to be ejected from the growing oxide and both matrix species ( Si and Ge ) have equal probabilities of oxidation leading to the formation an oxide of composition Si0.5Geo.50 2 . Supporting experiments confirm that GeO 2 in the surface layer is formed during warm up of the samples oxidized at 900 and 1000'C. INTRODUCTION High quality dielectric layers will be required to realise many of the advanced devices which maybe fabricated in SiGe hetrostructures and with this requirement .in mind the authors have undertaken a study of the oxidation of SiGe alloy grown on Si(100) substrates. Most previous investigators have studied the oxidation of dilute alloys containing much less than 50% germanium ( Si1 1. Gex, x
Data Loading...
