Processing Factors Impacting the Leakage Current and Flicker Noise of Germanium p[sup +]-n Junctions on Silicon Substrates

Abstract

The impact of several processing factors, such as the n-well doping, the use of nickel-germanidation, and the postmetallization anneal (PMA) temperature, on the reverse current and flicker noise of p+ -n junctions fabricated in epitaxial germanium-on-silicon substrates is investigated. It is shown that a higher well doping leads to a lower leakage current, in the range studied here, both for the perimeter and bulk component. It is furthermore shown that there exists an optimal PMA temperature around 450°C, depending on the leakage current component and the process details. The use of NiGe contacts improves the series resistance (forward current) but may deteriorate the perimeter leakage associated with surface-state generation at the Ge-Si O2 interface. This is confirmed by the low-frequency noise results, showing a dominance of the perimeter component. It is demonstrated that these effects are related to the occurrence of Ni-germanidation-induced voids along the edge of the p+ -n junctions. © 2007 The Electrochemical Society.