Amorphous boron nitride as an ultrathin copper diffusion barrier for advanced interconnects

Abstract

This study focuses on amorphous boron nitride ( alpha-BN) as a novel diffusion barrier for advanced semiconductor technology, particularly addressing the critical challenge of copper diffusion in back-end-of-line (BEOL) interconnects. Owing to its ultralow dielectric constant and robust barrier properties, alpha-BN is examined as an alternative to conventional low-k dielectrics. The investigation primarily employs theoretical modelling, using a Gaussian approximation potential, to simulate and understand the atomic-level interactions. This machine-learning-based potential enables realistic simulations of amorphous alpha-BN structures and allows us to examine how different film morphologies affect barrier performance. Furthermore, we studied the electronic and optical properties of the films using a simple Tight-Binding model. In addition to the theoretical work, we performed copper diffusion experiments through PECVD-grown alpha-BN on Si substrates. Theoretical and experimental results indicate that alpha-BN films can suppress Cu diffusion at nanometre thicknesses. Together, molecular dynamics simulations based on a machine-learned interatomic potential and PECVD experiments support the use of alpha-BN as a Cu diffusion barrier for BEOL interconnects.