Enhanced thermal stability of nickel germanide on thin epitaxial germanium by adding an ultrathin titanium layer

The thermal stability of NiGe films formed on epitaxial Ge on Si substrates was improved from 450to550°C by simply adding an ultrathin (∼1nm) Ti layer during Ni deposition, either as an intermediate layer between Ni and Ge or as a capping layer on Ni. The improvement was attributed to the formation of ternary Ni1−xTixGe phase near the NiGe surface, which acts as a capping layer to suppress agglomeration of the underlying NiGe film at an elevated temperature, as well as modification of the NiGe grain boundaries. The resistivity of NiGe is also slightly reduced by the Ti incorporation, making this method very promising for the germanium technology.

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