Diffusion barriers for copper interconnects

Thermally stable, thin W₂N, TaN, and TaC diffusion barrier layers between Cu and Si were developed by a radio-frequency sputtering method. The W₂N(8 nm), TaN(8 nm) and TaC(5 nm) barrier layers were found to prevent Cu diffusion to Si after annealing at 600, 700, and 600°C for 30 min, respectively. From the microstructural and diffusional analyses, the Cu diffusion mechanism through the barrier layers was explained by grain boundary and lattice diffusion