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

Abstract

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 Å, 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 °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.