NB/NI AND NI/NB BILAYERS ON SI - RAPID THERMAL-PROCESSING, PHASE-SEPARATION, AND TERNARY PHASE FORMATION

Ni/Nb and Nb/Ni bilayers on Si(100), Ni/NbSi2/Si(100) and Nb/Ni/Si/SiO2/Si(100) were produced by rf sputtering and annealed by rapid thermal processing. Thereafter, phase sequence and morphology were deduced by Auger electron spectroscopy and x-ray diffraction. The first three cases lead to phase separation of the binary compounds NbSi2 and NiSi2. Conversely when SiO2 is used as a buffer to limit the consumption of Si, the ternary phase Nb4Ni4Si7 or Nb4Ni4Si7 + NbSi2 can be produced depending on the amount of Ni available. These observations are consistent with the Nb-Ni-Si phase diagram, in which phase separation occurs in a Si-rich environment whereas the ternary phase is stable in a Si-poor environment.