INVESTIGATION OF Ta / Ni – Al INTEGRATED FILM USED AS a DIFFUSION BARRIER LAYER BETWEEN Cu AND Si

Ta (3.3 nm)/Ni–Al (3.3 nm) integrated films deposited on Si substrates by magnetron sputtering, annealed at various temperatures in a ultra-high vacuum, have been studied as diffusion barrier layers between Cu and Si for application in Cu interconnection. The images of transmission electron microscopy (TEM) prove that the cross-sectional interfaces of Cu/Ta/Ni–Al/Si sample annealed at 600°C are clear and sharp. No Cu–silicide peaks can be found from the X-ray diffraction (XRD) patterns of the 850°C annealed sample, but the sheet resistance of the sample increases abruptly. Moreover, large grooves are found from the image of atomic force microscopy (AFM) for the 850°C annealed sample, implying the failure of the diffusion barrier. The integrated Ta/Ni–Al barrier layer retains thermally stable nature up to at least 800°C, indicating that the Ta/Ni–Al integrated film is an excellent diffusion barrier between Cu and Si.