Diffusion barrier property of TaN between Si and Cu

Thermally stable, thin TaN diffusion barriers to prevent intermixing of Cu wiring with the Si substrate were developed by reactively sputtering Ta in a nitrogen atmosphere using a radio-frequency sputtering method. The TaN had a polycrystalline structure with disordered grain boundaries, and the 8 nm thick TaN layer was found to be enough to prevent the intermixing after annealing at 700°C for 30 min. The Cu diffusion in the TaN was concluded to be controlled by both the grain boundaries and lattice based on the diffusional analysis. The present study indicated that the chemical inertness with Cu and Si and structural stability at high temperatures are key parameters to evaluate the barrier properties.