Crystallization and failure behavior of Ta-Ni nanostructured/amorphous diffusion barriers for copper metallization

Abstract

This work examines the thin-film properties and diffusion barrier behavior of sputtered Ta-Ni films, aiming at depositing highly crystallization-resistant and conductive diffusion barriers for Cu metallization. Structural analysis indicates that the as-deposited Ta-Ni films indeed have a glassy structure and are free from highly resistive intermetallic compounds. Examining Si/Ta-Ni/Cu stacked samples reveals that thermally induced failure of amorphous Ta-Ni barriers is triggered by the barrier’s reaction with the silicon substrate at temperatures around 700°C. The effectiveness of the amorphous Ta-Ni thin film thus can be substantially enhanced by effectively blocking diffusion of copper toward the underlying silicon.