Formation of stable titanium germanosilicide thin films on Si _1-xGe _x

The sequential deposition of strained Si1-x Gex with concentrations x=0.20 and 0.30, amorphous silicon, and titanium on Si (100) after annealing at 700 °C leads to the formation of a C54 Ti (Si1-y Gey) 2 Si1-x Gex bilayer, the phase formation and interface stability of which are studied. The use of an amorphous layer of Si is employed to eliminate or decrease the formation of germanium-rich Si1-z Gez alloy precipitates found in the solid-phase reaction of Ti and Si1-x Gex. It has been proposed that the precipitation phenomenon was driven by differences in the enthalpy of formation as a function of concentration in the Ti (Si1-y Gey) 2 layer, resulting from the enthalpy difference between Ti Si2 and Ti Ge2 compounds, both of which are assumed to be completely miscible with one another. Layers of amorphous silicon of varying thicknesses were incorporated between a 300-Å Ti layer and the strained Si1-x Gex substrate layer to achieve Ti (Si1-y Gey) 2 films that are in equilibrium with the Si1-x Gex substrate. The use of amorphous silicon layers of varying thicknesses indicated that Ti (Si1-y Gey) 2 Si1-x Gex films could be formed with the absence of germanium-rich precipitates at the grain boundaries, depending on the amorphous silicon layer thickness.