Effect of impurities on initial stages of phase formation for the system of Ti deposited on (001) Si-Ge layers

Effect of impurities (oxygen, carbon) on initial stages of phase formation for the system of Ti overlayer deposited in a 2 x 10(-7) Torr vacuum on Si0 .83Ge0.18 layers epitaxially grown on (001) Si has been studied by Auger el ectron spectroscopy, X-ray powder diffractometry, conventional and high res olution transmission electron microscopy and energy dispersive spectroscopy . The change in impurity contents at the Ti/SiGe interface was realized by changing the thickness of the Ti overlayer. Two sets of Ti/SiGe/Si samples with 10 and 60 nm thick Ti were investigated. It was shown that for the sam ples with 60 nm thick Ti the content of the oxygen and carbon at the Ti/SiG e interface was one order of magnitude lower than that in the samples with 10 nm thick Ti overlayer. The first crystalline phase formed as a result of annealing at a vacuum better than 2 x 10(-7) Torr was Ti-5(Si,Ge)(3) for s amples with a high level of the impurities and C49-Ti(Si,Ge)(2) for samples with a low level of the impurities. An amorphous phase was revealed for bo th sets of specimens during the initial stages of phase formation. The resu lts obtained were interpreted within the framework of a recently developed model of phase formation. (C) 1999 Elsevier Science S.A. All rights reserve d.