Interdiffusion and reactions in the Cu/TiN/Si thin film system

The barrier capability of reactive sputtering deposited TiN thin films has been investigated in the Cu/TiN/Si structure by Auger electron spectroscopy (AES) and X-ray diffraction (XRD). Samples have been treated in vacuum in the temperature range 400 to 500 degrees C. During annealing, Cu migrates into the TiN layer and no appreciable decomposition of TiN is observed. Si diffuses slightly into the TiN layer and forms Ti5Si3 due to the Ti5Si3-TiO-SiO2 three-phase region at equilibrium in the Ti-Si-O system. Since Si and Cu diffuse in the TiOx defective layer in grain boundaries, the diffusion of Si and Cu through the TiN layer will be slowed down once TiOx is oxidized to TiO2. Therefore, TiN layer can be made as an effective barrier by incorporation of oxygen into the film.