The electrical property of plasma-treated Ta/TaNx diffusion barrier

In copper damascene processes, a barrier film is necessary to prevent copper diffusion into a dielectric layer as well as to improve the adhesion between the copper and dielectric layers. The tantalum/tantalum nitride (Ta/TaNx) composite film deposited by ionized metal plasma is widely used as the copper diffusion barrier layer due to its effective barrier property and chemical inertness. To reduce the contact resistance of devices, re-sputtering technology using biased Ar plasma was applied to remove the barrier layer from bottoms in advanced metallization processes. This study found that the film resistivity of Ta films depended on the re-sputtering amount of under TaNx films. As the re-sputtering amount of under TaNx films increased, the resistivity of the Ta/TaNx bi-layer decreased and saturated to a limited value. The behavior resulted from the phase transformation of Ta films on different TaNx substrates.