Preferential PtSi Formation in Thermal Reaction between Pt and Si0.8Ge0.2 MBE Layers

Thermal reactions between Pt and Si0.8Ge0.2 MBE layers were studied by sputtering AES and X-ray diffraction measurements. Pt(1000 A)/Si0.8Ge0.2(1000 A) annealed at 300°C for 3 hours or at 400°C for 1 hour formed Pt2(Si0.8Ge0.2)1 or Pt1(Si0.8Ge0.2)1, respectively. The sample annealed at 400°C for 16 hours showed a slight accumulation of Ge at the Pt(SiGe)/Si interface, and the annealing at 500°C for 1 hour repelled the Ge from the surface Pt(SiGe) layer to form a Ge-rich SiGe epitaxial layer at the PtSi/Si interface. These results suggest a stronger bonding of Pt-Si than Pt-Ge and a possible preferential formation of PtSi at the interface even for lower annealing temperatures.