Atomic diffusion at the Cu-Au-Si multilayers interface

Si(1 0 0) and (1 1 1) oriented silicon wafers were used as a substrate for metallic bilayers deposition of copper and gold. Cu/Au/Si structures were obtained by thermal evaporation and then heated below 400 °C in vacuum. These solid-state reactions occurred in the samples have been studied using X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), scanning electronic microscopy (SEM) and X-ray dispersive energy analyzer (XDE). The study shows that heat treatment at 200 °C of the multilayered Cu/Au/Si structure leads to the formation and the co-existence of both Cu3Si and Cu4Si copper rich-silicides with the expansion of their respective cells, independently of the orientation of the substrate. The increasing of the annealing temperature until 400 °C leads to the growth of well-oriented crystallites corresponding to Cu3Si and Cu4Si silicides on Si(1 1 1) but only Cu4Si crystallites with square and rectangular shapes on Si(1 0 0). The thermal stability of formed copper silicides after heat treatment at 400 °C during 30 min for both Cu/Au/Si(1 0 0) and Cu/Au/Si(1 1 1) systems is analyzed.