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TiN diffusion barrier layers were deposited on SiO2/Si substrate by ALD method that employed TiCl4 and NH3 as the source and reactant gases, respectively, at a temperature range between 350°C and 500°C. Properties of films, including deposition rate, resistivity, surface roughness and chemical composition, were investigated, and performance of TiN diffusion barrier layer was also verified. Deposition rate of TiN films is almost a constant (~0.15Å/cycle), independent from the process condition, measured by ellipsometer and verified by AES. This demonstrates TiN films were grown by ALD growth mechanism. Resistivity of the films is below 125μΩ·cm when deposition temperature is above 400°C,which is very low compared to TiN film grown by other CVD methods, and it decreases with the increase of reaction temperature and TiN films thickness. AFM analysis result reveals that RMS roughness is low (~0.636nm). Chemical composition was analyzed by AES and XPS, content of chorine in TiN films is about 0.5 at. %, and the ratio of N and Ti by atomic concentration is nearly 1:1. In order to research the performance of TiN as diffusion barrier layer, copper is sputtered on TiN films and then post-annealed in a vacuum ambient of 10-5 Pa at 400°C for 1h. AES analysis results indicate that no copper diffusion into the SiO2 for Si with Cu/TiN/SiO2 films after annealing.