Kinetics of thin-film reactions of Cu/a-Ge bilayers

The kinetics of the Cu3Ge phase formation during reactions between 600 nm polycrystalline Cu (poly-Cu) and 600 nm amorphous Ge (a-Ge) layers on Si (100) substrates have been studied as a function of annealing conditions. Monoclinic Cu3Ge nucleated rapidly, resulting in smooth Cu3Ge layers. The room-temperature resistivity of the Cu3Ge was ∼8 μΩ cm (∼4.5 times that of pure Cu). The real-time resistance versus temperature [R(T)] characteristics were nearly identical for heating rates of 0.1–5 °C/min. Modeling of the R(T) data indicates that the reaction was predominantly diffusion controlled with a rate of (4×10−3 cm2/s) exp [−0.85±0.01 eV/kT] where k=8.617×10−5 eV/K. Secondary ion mass spectrometry profiles and R(T) data for the films annealed to various temperatures indicate that the Cu3Ge/Ge interface is stable for T<300 °C.