Metal In-Diffusion during Fe and Co-Germanidation of Germanium

In this paper, the deep levels occurring in Fe- or Co-germanide Schottky barriers on ntype Ge have been studied by Deep Level Transient Spectroscopy (DLTS). As is shown, no traps have been found for germanidation temperatures up to 500 oC, suggesting that in both cases no marked metal in-diffusion takes place during the Rapid Thermal Annealing (RTA) step. Deep acceptor states in the upper half of the Ge band gap and belonging to substitutional Co and Fe can be detected by DLTS only at higher RTA temperatures (TRTA). For the highest TRTA, deep levels belonging to other metal contaminants (Cu) have been observed as well. Simultaneously, the reverse current of the Schottky barriers increases with TRTA, while the barrier height is also strongly affected.