Reactively sputtered Mo-V nitride thin films as ternary diffusion barriers for copper metallization

The effectiveness and performance of Mo-based ternary nitride films as copper diffusion barriers were investigated. Thermally stable Mo-V nitride thin diffusion barrier layers were deposited using radio frequency reactive magnetron sputtering and their barrier capability was evaluated and studied. Cu/Mo-V nitride/Si structures were fabricated and annealed at different temperatures. The agglomeration of Cu and the formation of Cu(3)Si due to high-temperature annealing were probed using scanning electron microscopy/energy-dispersive X-ray spectroscopy. The drastic increase in sheet resistance after annealing at 800 degrees C was found to take place due to the formation of highly resistive Cu(3)Si, also evident from X-ray diffraction patterns. The formation of inverted pyramidal structure of Cu(3)Si at the interface penetrated into the Si substrate corroborated the breakdown of the barrier layer at 800 degrees C. Our results suggest that an 8 nm thick Mo-V nitride barrier can effectively prevent the formation of Cu(3)Si up to high annealing temperatures.