Ultralow-k Amorphous Boron Nitride Film for Copper Interconnect Capping Layer

Abstract

We report the feasibility of ultralow-k amorphous boron nitride (alpha-BN) film as a new capping layer for copper (Cu) interconnects. alpha-BN thin films were successfully deposited using a plasma-enhanced chemical vapor deposition (PECVD) process. The CVD-grown alpha-BN showed a k-value as low as 2.0 at 3 nm thickness, low leakage current density (similar to 7 x 10(-8) A/cm(2)), and high breakdown field (similar to 8.8 MV/cm) comparable to a conventional SiN blocking layer. The alpha-BN has excellent thermal stability up to 1000 degrees C, implying that the film can be used not only for the back-end-of-line (BEOL) but also for the front-end-of line (FEOL) processes. A 7-nm-thick alpha-BN film successfully blocked Cu diffusion at temperatures up to 500 degrees C. The alpha-BN film also showed excellent adhesion to Cu, with an adhesion energy of 2.90 +/- 0.51 J/m(2) between alpha-BN and Cu. The COMSOL multiphysics simulation predicted that, compared to a conventional SiN capping layer, an alpha-BN capping layer would reduce interconnect RC delay by up to 17%. The alpha-BN was proven to be a promising new candidate for a capping layer to reduce RC delay in Cu interconnect systems.