Thick selective electroless plated cobalt-nickel alloy contacts to CoSi sub 2:1. Material properties.

Thick (>= 1micron) selective electroless plating of Co, Ni and their alloys is used to "plug" contacts to shallow junctions below CoSi sub 2. After a discussion of the electroless plating procedure, plating uniformity and the substrate doping dependence of the plated material characteristics, data is presented on the Al/Co-Ni/CoSi sub 2/Si material interaction for various hydrogen anneal cycles up to 450C. It is shown that electroless plated Co-Ni alloy plugs can be annealed at slightly above 400C without any Co/CoSi sub2/Si interaction. The Al/Co interaction is confined to a layer ~1000angstroms thick. At 450C, the Co/CoSi sub 2/Si interaction converts the CoSi sub 2 and ~600angstroms of Si below CoSi sub 2 to CoSi. Alloying of Ni to Co is indicated by the observation that the rapidly diffusing Ni component is constrained to diffuse with the slower bulk Co.