Electrical and structural properties of zirconium germanosilicide formed by a bilayer solid state reaction of Zr with strained Si1-xGex alloys

The effects of alloy composition on the electrical and structural properties of zirconium germanosilicide (Zr-Si-Ge) films formed during the Zr/Si1-xGex solid state reaction were investigated. Thin films of Zr(Si1-yGey) and C49 Zr(Si1-yGey)(2) were formed from the solid phase reaction of Zr and Si1-xGex bilayer structures. The thicknesses of the Zr and Si1-xGex layers were 100 and 500 Angstrom, respectively, It was observed that Zr reacts uniformly with the Si1-xGex alloy and that C49 Zr(Si1-yGey)(2) with y=x is the final phase of the Zr/Si1-xGex solid phase reaction for all compositions examined. The sheet resistance of the Zr(Si1-yGey)(2) thin films was higher than the sheet resistance of similarly prepared ZrSi2 films. The stability of Zr(Si1-yGey)(2) in contact with Si1-xGex was investigated and compared to the stability of Ti(Si1-yGey)(2) in contact with Si1-xGex. The Ti(Si1-yGey)(2)/Si1-xGex structure is unstable when annealed for 10 min at 700 degrees C, with Ge segregating from Ti(Si1-yGey)(2) and forming Ge-rich Si1-zGez precipitates at grain boundaries. In contrast, no Ge segregation was detected in the Zr(Si1-yGey)(2)/Si1-xGex structures. We attribute the stability of the Zr-based structure to a smaller thermodynamic driving force for germanium segregation and stronger atomic bonding in C49 Zr(Si1-yGey)(2). Classical thermodynamics were used to calculate Zr(Si1-yGey)(2)-Si1-xGex tie lines in the Zr-Si-Ge ternary phase diagram. The calculations were compared with previously calculated Ti(Si1-yGey)(2)-Si1-xGex tie lines. (C) 1997 American Institute of Physics.