Copper (Cu) thin films have been deposited onto titanium nitride (TiN) layer which was previously prepared by flow modulation chemical vapor deposition (FMCVD) technology. The diffusion barrier properties of the TiN layer to Cu have been studied depending upon the post-annealing and the sample preparation conditions of the TiN layer. The Cu deposition has performed by RF magnetron sputtering with 5N target in the high vacuum ambient. The FMCVD process has carried out in a single CVD chamber by switching TiCl4 flow to the argon flow cyclically, which creates sequential deposition of TiN layer and chlorine reduction process. The higher flow modulation cycle and Ar purge time during the TiN layer growth have been observed to provide the better diffusion barrier property in Auger depth profile and X-ray diffraction analysis.