Characteristics of W-B-C-N Thin Diffusion Barrier for Cu Interconnects

A tungsten boron carbon nitride (W-B-C-N) quaternary compound thin film was deposited as a diffusion barrier for preventing interdiffusion between Cu metal and a Si semiconductor. The thickness of the W-B-C-N thin film was 100 nm (1,000 Å), and the working pressure was 3 mTorr during the deposition process. To examine the diffusion characteristics of interface, we deposited a Cu film on the W-B-C-N thin film. We got excellent results in that the Cu thin film provided a stuffing effect that prevented interdiffusion at Cu/Si interface after annealing at 850 C for 30 min because W-B-C-N thin films are good passive diffusion barriers, which may be due to the boron, carbon, and nitrogen inside the W-B-C-N film not being bonded states but impurities.