ZrN/Zr/ZrN diffusion barrier was grown on Si (100) substrates under different substrate bias in a RF magnetron sputtering system. The effect of insertion of a thin Zr interlayer between Zr-N films on Zr-N diffusion barrier performance in Cu metallization was investigated. The results reveal that an increase in negative substrate bias results in a decrease in the resistivity together with a higher ZrN (111) preferred orientation. The barrier breakdown temperature of ZrN/Zr/ZrN film is about 100 °C higher than that of ZrN. It can effectively prevent the diffusion of Cu after annealing at 750 °C. The improvement of diffusion barrier performance is due to that the production of ZrO2 blocks the diffusion paths of Cu when annealing at high temperature.