Shallow silicide-to-silicon contacts: The case of amorphous-Pd ₈₀Si₂₀-to-silicon

It is known that fabrication of shallow silicide-to-silicon contacts is possible by diluting the silicide-forming metal with some other metal which does not participate in silicide formation at the chosen annealing temperature. We report preliminary experiments undertaken to develop contacts which are even shallower, by a modification of this method. The diluting metal is replaced by Si which supplies a portion of the Si needed in silicide formation. An amorphous alloy of ∼400-Å Pd80Si20, coevaporated onto a Si single crystal substrate, has been successfully used to form a continuous and uniform layer of Pd2Si which only consumes ∼80Å of substrate silicon. The formation and microstructural properties of the formed silicide has been studied by in situ transmission electron microscopy experiments. These results were correlated with parallel measurements of the current-voltage characteristics of Schottky diodes made from the same material. It is shown that annealing for ∼ 1/4 h at 200°C is sufficient to form the desired Pd2Si.