Stability of polycrystalline silicon-on-cobalt disilicide-silicon structures.

Stability of the polycrystalline silicon-CoSi sub 2-single crystalline silicon sandwich structures, at temperatures in the range of 600-950C, is investigated. It is found that at temperatures above 800C, the structure is unstable whenever the polycrystalline silicon is undoped or boron (insitu) doped. At temperatures >800C, silicon migration to the crystalline substrate and CoSi sub 2 migration to surface occurred, finally resulting in a structure where no polycrystalline silicon was left on the top of CoSi sub 2 in a manner analogous to solid phase epitaxial process reported earlier in literature. However this exchange of place between polycrystalline silicon and CoSi sub 2 did not occur when the phosphorus (in situ) doped film was used. The structure "phosphorus (in situ) doped polycrystalline silicon-CoSi sub 2-single crystalline silicon" was stable at 900C in Argon, nitrogen-15% hydrogen, or PBr sub 3 doping ambients.