XPS and TOFSIMS studies of shallow Si/Si1-xGex/Si layers

We present here a combined study of XPS and TOFSIMS on the oxidation of Si/ Si1-xGex/Si layers with x = 0.2 and top Si thickness from 0.5 to 3 nm. The oxidation conditions correspond to the formation of a 2, 4 or 6 nm thick Si O2 layer. XPS shows that, the oxidation of Ce does not occur and that the a ctual oxide thickness measured from the Si2p peak is in very good agreement with the expected thickness except for the thinnest top layer. The samples with the thinnest top layer show a fully oxidized cap layer and the oxidat ion continued through the SiGe layer to produce an oxidized layer. These re sults were largely confirmed by TOFSIMS depth profile measurements with a d ual beam system (IONTOF IV) which show no differences comparing the four th ickest cap layers. The samples with the initially very thin Si top layers s how a much thicker oxide layer estimated to similar to 20 nm, and Ge segreg ation is also observed. (C) 1999 Elsevier Science S.A. All lights reserved.