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 mV 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 (4310 cm/s) exp @20.8560.01 eV/kT# where k58.617 310 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. © 1997 American Institute of Physics. @S0021-8979~97!02619-4#