Determination of the dominant diffusing species during nickel and palladium germanide formation

Abstract

We have used real-time Rutherford backscattering spectrometry to determine the dominant diffusing species during the formation of nickel germanide and palladium germanide; two of the most promising candidates for use as ohmic contacts were germanium to replace silicon in devices. In the Ni/Ge system Ni5Ge3 is the first phase to form, followed by NiGe. The results show that during Ni5Ge3 formation Ni is essentially the sole diffusing species and is responsible for almost all the growth. During the 2nd-phase formation both Ni and Ge diffuse, with the Ge diffusion prominent during the very early stages, while the later stage of growth is dominated by Ni diffusion. During the formation of Pd2Ge and PdGe phases the metal (i.e. palladium) is once again the dominant diffusing species. The relative contribution of germanium diffusion to the growth is, however, more prominent in the Pd/Ge system, with significant amounts of Ge diffusion being observed during formation of both phases.