Ultralow- \textit Amorphous Boron Nitride Film for Copper Interconnect Capping Layer

We report the feasibility of ultralow- \textit{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 \textit{k} -value as low as 2.0 at 3 nm thickness, low leakage current density ( \sim 7 \times 10 ^{-\text{8}} A/cm ^{\text{2}} ), and high breakdown field ( \sim 8.8 MV/cm) comparable to a conventional SiN blocking layer. The \alpha -BN has excellent thermal stability up to 1000 ^{\circ} 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 ^{\circ} C. The \alpha -BN film also showed excellent adhesion to Cu, with an adhesion energy of 2.90 \pm 0.51 J/m ^{\text{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