The B ions were implanted into thin layers of WSi2 or CoSi2, on polycrystalline or monocrystalline Si, and were out-diffused into the substrate during furnace heating or rapid thermal annealing. Shallow (less than 100nm) junctions were obtained by using rapid thermal annealing. The interface concentrations were close to the solid solubilities of the respective dopant; that is, more than 8 x 1019/cm3. During furnace annealing at temperatures above 800C, the migration of B from CoSi2 led to a decrease, in the interface concentration, to less than 2 x 1019/cm3. This was attributed to the effect of marked B segregation, and probably to reactive losses at the SiO2/CoSi2 interface. It was found that the dopant redistribution was determined by the lattice and grain-boundary diffusivities, the solubility limits, layer inhomogeneities, dopant segregation at interfaces and grain boundaries. In addition, there was probably a phase transformation of the dopants which were segregated at the SiO2/silicide interface.

V.Probst, H.Schaber, A.Mitwalsky, H.Kabza, L.Van den Hove, K.Maex. Journal of Applied Physics, 1991, 70[2], 708-19