Kinetics of Pd2Si layer growth measured by an x-ray diffraction technique

Abstract

An x-ray diffraction approach has been developed for determination of the kinetics of growth of Pd2Si layers. Epitaxial Pd2Si films were grown on Si(111) substrates over a temperature range of 160–222 °C by a solid-state reaction between the substrates and the Pd overlayers. The parabolic rate equation was verified and rate constants showed Arrhenius behavior with an activation energy Ea=1.06 eV and prefactor k0=7×10−4 cm2/s. The low value of Ea suggests a short-circuit diffusion mechanism. It is reasonable to expect that impurities and microstructure may play important roles in the growth process. Impurity levels in the specimens were evaluated by analytic techniques suited to thin-film study: Rutherford backscattering spectrometry, secondary ion mass spectrometry, and Auger electron spectrometry. No impurities were present at concentrations approaching 1 at. %. Some O, C, and F were detected at the Pd2Si/Si interfaces. The annealing ambient was the major source of further contamination. Upon emergence of the growth interface through the sample surface (some Pd2Si on surface), impurity pickup was detected. Interfacial roughness was indicated by all the techniques to be on the order of 20 nm.