Zr-Si-N diffusion barrier films were deposited by reactive magnetron sputtering with different negative bias. The results reveal that the Si content and resistivity of the Zr-Si-N films decrease as negative bias increases. The crystalline phase increases with the increase of negative bias. The thermal stability of Zr-Si-N diffusion barrier was so good that Zr-Si-N diffusion barrier can effectively prevent from the diffusion of Cu.