Titanium Germanosilicide: Phase Formation, Segregation, and Morphology

ABSTRACTThe high temperature solid phase reaction of Ti with SixGe1−x produces a low resistivity titanium germanosilicide which is isomorphic with the C54 phase of TiSi2 and TiGe2. The composition of the final C54 Ti(SiyGe1−y)2 film is dependent on the composition of the initial Si-Ge alloy and on the annealing conditions. The intermediate phases of the Ti-Si and Ti-Ge reactions are C49 TiSi2 and Ti6Ge5 respectively. The reaction path of Ti - SixGe1−x shifts from that of Ti-Si to that of Ti-Ge as the SixGe1−x alloy composition changes (×=1→0). Phase separations were observed at low temperatures for Ti reactions with Si-Ge alloys and the C54 formation temperature was observed to decrease as the Si-Ge alloy composition approached Si.5Ge.5. Surface and interface morphologies were examined using SEM and TEM. The formation of smooth, large grain, low resistivity films has been observed for the reaction of Ti with low Ge content alloys (x≥0.7). As germanium content is increased the formation of faceted islands is observed. Reactions with high Ge content alloys (x≤0.3) produce films with morphologies similar to those of the Ti-Ge reaction.