FILM THICKNESS EFFECTS IN THE TI-SI1-XGEX SOLID-PHASE REACTION

The effects of film thickness on the Ti-Si1-xGex solid phase reaction were investigated, Thin C49 TiM(2) (M=Si1-yGey) films were formed from the solid phase reaction of 400 Angstrom Ti or 100 Angstrom Ti with Si1-xGex alloys. It was determined that for films formed from 400 Angstrom Ti, the nucleation barrier of the C49-to-C54 transformation decreases with increasing germanium content, for alloy compositions with up to approximate to 40 at. % germanium (i.e., x less than or equal to 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(Si1-yGey)(2). For films formed from a 100 Angstrom Ti layer it was observed that the C54 TiSi2 nucleation temperature was increased by greater than or equal to 125 degrees 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 Angstrom films, leads to an increased rate of germanium segregation. (C) 1995 American Institute of Physics.