Morphological and phase stability of nickel-germanosilicide on Si1-xGex under thermal stress

Continuous and uniform Ni(Si,Ge) layers are formed on polycrystalline Si and Si0.42Ge0.58 substrate films at 500 degreesC by rapid thermal processing. The germanosilicide is identified as NiSi0.42Ge0.58, i.e., with the same Si-to-Ge ratio as in the substrate. The NiSi0.42Ge0.58 layer has agglomerated at 600 degreesC. This is accompanied by a diffusion of Ge out from the germanosilicide grains and the growth of a Ge-rich SiGe region in their close vicinity. These changes cause a slight variation in the atomic composition of Ni(Si,Ge) detectable for individual grains by means of energy dispersive spectroscopy. Above 600 degreesC, substantial outdiffusion of Ge from the Ni(Si,Ge) grains occurs concurrently with the migration of the grains into the substrate film away from the surface area leaving a Ge-rich SiGe region behind. These observations can be understood with reference to calculated Ni-Si-Ge ternary phase diagrams with and without the inclusion of NiSi2. When Ge is present, the Ni-based self-aligned silicide process presents a robust technique with respect to device applications. (C) 2002 American Institute of Physics.