Diffusion Barrier Behaviors of V-Ta, V-Ta-N and V-Ta/V-Ta-N Alloy Films in Cu Interconnects

The V-Ta, V-Ta-N and V-Ta/V-Ta-N alloy barrier layers with thickness of 50 nm were deposited on Si (100) substrates by magnetron sputtering and then the 300 nm thick Cu films were prepared on the barrier layers to obtain Cu/V-Ta/Si, Cu/V-Ta-N/Si and Cu/V-Ta/V-Ta-N/Si multilayer films. The multilayer film samples were subsequently annealed at 300°C–750°C temperatures for 1 h in vacuum atmosphere. The crystal structure, surface morphology and sheet resistance were characterized by grazing incidence x-ray diffraction (GXRD), electron probe microanalysis (EPMA), scanning electron microscopy (SEM) and four-point probe (FPP) analysis to investigate the diffusion barrier behavior of the V-Ta, V-Ta-N and V-Ta/V-Ta-N alloy barrier layers. The results show that the V-Ta, V-Ta-N and V-Ta/V-Ta-N barrier layers effectively blocked the diffusion of Cu into the Si substrate. When annealed at 700°C, the Cu/V-Ta/Si and Cu/V-Ta/V-Ta-N/Si thin film samples maintained good thermal stability and demonstrated low sheet resistance (∼ 0.3 Ω cm). Therefore, both the V-Ta and V-Ta/V-Ta-N thin films are promising candidates for use as diffusion barrier layers.