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 μcm (∼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.