Study of nitrogen diffusion profile of low resistivity diffusion barrier by resputtering technology.

One of the major challenges in the integrated circuit beyond 90 nm is to fabricate low resistivity Cu diffusion barrier layer in the metal multilevel interconnect. Ta/TaN bilayer is one of the best candidates for Cu metal diffusion layer. It provides the advantage good diffusion performance between Cu and low-k dielectric layer. However, the resistivity is large deviation from tantalum phase variation. This is because of Tantalum of bilayer easily found in beta-phase, which is high resistance. This paper proposed a low resistivity alpha-Ta thin films were grown by treatment-TaN using Argon plasma treatment on TaN substrate. The argon treatment redistribute nitrogen profile between Ta and TaN and create a Ta(N) interface. X-ray diffraction analyses show that the interface film is composed of b.c.c.-Ta(N) grains. This Ta/treatment TaN provide new method to fabricated b.c.c.-Ta(N) difference from the previously report deposition by sputtering process. The resistivity will decrease nitrogen concentration to provide a favorable environment to promote low resistivity Tantalum alpha-phase formation.