Performance of WCN diffusion barrier for Cu multilevel interconnects

The electrical and thermal properties of a WCN diffusion barrier have been studied for Cu multilevel interconnects. The WCN has been prepared using an atomic layer deposition system with WF₆-CH₄-NH₃-H₂ gases and has a very low resistivity of 100μΩcm and 96.9% step coverage on the high-aspect-ratio vias. The thermally stable WCN maintains an amorphous state at 800 °C and Cu/WCN contact resistance remains within a 10% deviation from the initial value after 700 °C. The mean time to failure suggests that the Cu/WCN interconnects have a longer lifetime than Cu/TaN and Cu/WN interconnects because WCN prevents Cu migration owing to the stress evolution from tensile to compressive.