Reduction of the phase transition temperature of TiSi2 on Si(111) using a Ta interlayer

The effect of a thin Ta interlayer on the C49 to C54 phase transition of TiSi2 on Si(111) was examined. The Ta interlayered samples were prepared by depositing Ta and Ti films sequentially on Si(111) substrates in a UHV system. As control samples, 100 Angstrom Ti films were deposited directly on clean Si(111) substrates. The deposited substrates were annealed for 10 min, in-situ, at temperatures between 500 degrees C and 750 degrees C using 50 degrees C increments. The TiSi2 which formed in this UHV process, was analyzed with XRD, AES, SEM, TEM, and four-point probe measurements. The control samples exhibited the C49 to C54 transition at a temperature of 750 degrees C. However, the TiSi2 samples with 5 Angstrom and 10 Angstrom Ta interlayers displayed a significant reduction of the phase transition temperature. The XRD analysis indicated that the C49 to C54 transition temperature of TiSi2 was lowered by similar to 200 degrees C. The sheet resistance measurement showed a low resistivity characteristic of C54. The SEM and TEM micrographs showed that the Ta interlayer also suppressed the surface agglomeration of the C54 TiSi2 film. The AES analysis data indicated that the composition of the titanium silicide showed the expected Ti:Si stoichiometry of 1:2.