ION-BEAM SYNTHESIS OF COSI2 IN SI1-XGEX ALLOY LAYERS WITH DIFFERENT GE CONCENTRATIONS

Ion beam synthesis is a very successful technique to create buried CoS i2 layers in Si. Recently we have reported on the synthesis of CoSi2 i n SiGe and on the redistribution of Ge that accompanies this formation of a buried CoSi, layer [A. Lauwers et al., Mater. Res. Soc. Symp. Pr oc. 235 (1992) 299]. The aim of the present work is to study the impac t of increasing the SiGe lattice parameter on the growth of the buried layer. Epitaxial Si1-xGex alloy layers with different Ge concentratio ns are implanted with high doses of Co. The Co doses are varied betwee n 0.6 x 10(17) and 2 x 10(17) at. /cm2. The influence of the Ge concen tration on the strain situation in the as-implanted samples is studied . Increasing. the SiGe lattice parameter is found to change not only t he strain but also the type and the size distribution of the CoSi2 pre cipitates. The formation of a buried CoSi2 layer during subsequent ann eal is observed to be hindered by increasing the Ge concentration.