Film thickness effects in the Ti–Si1−xGex solid phase reaction

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Abstract
The effects of film thickness on the Ti–Si1−xGex solid phase reaction were investigated. Thin C49 TiM2 (M=Si1−yGey) films were formed from the solid phase reaction of 400 Å Ti or 100 Å Ti with Si1−xGex alloys. It was determined that for films formed from 400 Å Ti, the nucleation barrier of the C49‐to‐C54 transformation decreases with increasing germanium content, for alloy compositions with up to ≊40 at. % germanium (i.e., x≤0.40). It was also observed that germanium segregates out of the TiM2 lattice, for both the C49 and C54 phases, and is replaced on the TiM2 lattice with Si from the substrate. The germanium segregation changes the Ge index y of the Ti(Si1−yGey)2. For films formed from a 100 Å Ti layer it was observed that the C54 TiSi2 nucleation temperature was increased by ≥125 °C. The addition of germanium to the silicon increased the agglomeration of the C49 phase and caused the C54 TiM2 nucleation barrier to increase further. The results also indicate that the increased temperature required for the transition to the C54 phase, for the 100 Å films, leads to an increased rate of germanium segregation.

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