Microstructural and electrical properties of Cu-germanide formed on p-type Ge wafer

We have investigated the microstructural and electrical properties of Cu-germanides formed by the deposition of Cu on Ge wafer, followed by rapid thermal annealing (RTA) process at the temperatures in the range of 300-700 °C. Regardless of RTA temperature, the Cu₃Ge was the only phase formed as a result of solid-state reaction between Cu and Ge driven by RTA process. The RTA temperature dependency of specific contact resistivity of Cu₃Ge was explained in terms of its structural evolution caused by RTA process. The RTA process at 400 °C led to the formation of Cu₃Ge film having highly uniform surface and interface morphologies, allowing the minimum value of the specific contact resistivity. The samples annealed above 500 °C underwent the severe structural degradation of Cu₃Ge, resulting in a rapid increase in the specific contact resistivity. After RTA at 700 °C, pyramidal Cu₃Ge islands standing on a corner, distributed along Ge <110> direction were formed with epitaxial relationship on underlying Ge.