Achieving sub-0.1 ev hole schottky barrier height for NiSiGe on SiGe by aluminum segregation

Nickel germano-silicide (NiSiGe) contact was formed on silicon-germanium (Si1-x Gex or SiGe) epilayer with 26% Ge, grown on p-Si (100) substrate. We report the tuning of the effective Schottky barrier height (SBH) of holes at the NiSiGeSiGe junction to sub- 0.1 eV by the introduction of aluminum (Al) using ion implantation and its segregation at the NiSiGeSiGe interface after germano-silicidation. The effective SBH decreases with increasing concentration of Al at the NiSiGeSiGe interface. We demonstrate the achievement of one of the lowest reported hole SBHs for NiSiGe on SiGe of 0.068 eV, which is extremely promising for application in p -type metal oxide semiconductor field-effect transistors. The presence of Al does not affect the sheet resistance or the low-resistivity nickel mono-germano-silicide phase of the NiSiGe film. Our results indicate the possibility of an electric dipole at the NiSiGeSiGe interface, introduced by Al atoms, which is responsible for the SBH modulation. Increase in thickness of nickel used for germano-silicidation increases the effective SBH. The increase in the Al implant dose reduces the effective SBH but degrades the SiGe epilayer by amorphizing it to a greater depth. Thus, a trade-off exists in choosing the Al implant dose and the nickel thickness needed to consume the amorphized SiGe for maximum device performance.