Film thickness effects in the Ti–Si1-xGex solid phase reaction
ABSTRACT The effects of film thickness on the Ti–Si 1-x Ge x solid phase reaction were investigated. Thin C49 TiM 2 (M=Si 1-y Ge y ) films were formed from the solid phase reaction of 400 Å Ti or 100 Å Ti with Si 1-x Ge x 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 TiM 2 lattice, for both the C49 and C54 phases, and is replaced on the TiM 2 lattice with Si from the substrate. The germanium segregation changes the Ge index y of the Ti(Si 1-y Ge y ) 2 . For films formed from a 100 Å Ti layer it was observed that the C54 TiSi 2 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 TiM 2 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. © 1995 American Institute of Physics.