Atomic diffusion at the Cu-Au-Si multilayers interface

Si(100) and (111) 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^oC 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^oC of the multilayered Cu/Au/Si structure leads to the formation and the co-existence of both Cu"3Si and Cu"4Si 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^oC leads to the growth of well-oriented crystallites corresponding to Cu"3Si and Cu"4Si silicides on Si(111) but only Cu"4Si crystallites with square and rectangular shapes on Si(100). The thermal stability of formed copper silicides after heat treatment at 400^oC during 30min for both Cu/Au/Si(100) and Cu/Au/Si(111) systems is analyzed.