Effect of palladium addition on nickel silicide formation on Si (111)

Abstract

In this work, the influence of palladium addition on phase transition, surface morphology, structural, vibrational, and electrical properties of nickel silicide is investigated at various temperatures. For Ni(Pd)Si films micro-Raman measurements have yielded Raman phonon peaks belonging to NiSi phase, although redshifted, on par with new peaks at 322 and 434 cm-1, not determined before, which we assign to the compositional disorder, introduced by Pd. The results have shown that Ni(Pd)Si films are thermally stable up to 900 °C, which is 100-150 °C more than that for pure NiSi films. Applying Miedema's model we have calculated the heat of formation for Ni(Pd)Si and found it to be more negative than that for pure NiSi, revealing a key role of Pd in the retardation of NiSi2 phase formation. AFM results have shown that the presence of Pd favorably influences the surface morphology of NiSi, resulting in a smoother surface. Furthermore, we have discussed the impact of annealing conditions on peculiarities of Pd diffusion, element distribution and electrical properties of Ni(Pd)Si and NiSi films.