Dielectric/metal sidewall diffusion barrier for Cu/porous ultralow-<i>k</i> interconnect technology

Abstract

With the acknowledged insufficiency of traditional Ta or TaN barriers, deposited by physical vapor deposition (PVD), in the Cu/porous ultralow-k intermetal dielectric integration, an amorphous hydrogenated SiC (a-SiC:H)/Ta bilayer sidewall diffusion barrier has been fabricated using 0.13 μm Cu/porous ultralow-k [Porous-SiLK (Proprietary product from Dow Chemical Corporation, USA), k∼2.2] single damascene process. The electrical tests show that the line-to-line leakage current and the electrical breakdown field (EBD) of samples with this a-SiC:H/Ta dielectric/metal bilayer structure are significantly improved compared to the conventional PVD multi-stacked Ta(N) sidewall barrier. This improvement is mostly due to surface roughness modification after the deposition of a-SiC:H film, which, in addition to being a good barrier to Cu diffusion, can effectively “seal” the weak points on the surface of porous low-k material that are responsible for the sidewall barrier failure.