Electrical and Microstructural Characterization of Cu-Germanide Contacts Formed on p-Type Ge Substrate

We have investigated the electrical and microstructural properties of Cu-germanide formed on p-type Ge substrate as a function of rapid thermal annealing (RTA) temperature. As increasing RTA temperatures, Cu films reacted with Ge and formed Cu-germanides. The Cu₃Ge phase appears to be the dominant phase along with Cu₅Ge₂ phase at annealing temperatures of 500 and 600 °C. The sheet resistance and specific contact resistivity were investigated as a function of germanide formation temperature. A minimum specific contact resistivity value of 6.19´10^-6 Ωcm² is obtained after annealing at 400 °C associated with the formation of stoichiometric Cu₃Ge.  The sheet resistance and specific contact resistivity increased after rapid thermal at temperatures >500 °C indicated the degradation of the contact properties and could be associated with the formation of copper rich Cu₅Ge₂phase and the loss of structural integrity with increasing annealing temperature.