A deep-level transient spectroscopy study of Co- and Ni-germanided n-type germanium

In this paper, the impact of the rapid thermal annealing (RTA) temperature on the formation of deep levels during Ni- or Co-germanidation of n-type Ge substrates has been studied by Deep-Level Transient Spectroscopy. As is shown, metal in-diffusion is found in the case of nickel, starting from an RTA temperature (Tann) of 400 °C, while no clear evidence of metal-related deep electron traps is found for Co up to 500 °C. This is also reflected in the reverse current of the resulting Schottky barriers: generally, an increase has been found for increasing Tann, which can be ascribed to the impact of the generation centers introduced in the Ge substrate during the germanidation. It is concluded from this that source/drain metallization for future CMOS on Ge, employing low thermal budgets will not introduce deep levels that compromise the leakage current of the junctions.