CRYSTALLIZATION AND FAILURE BEHAVIORS OF Ta-Co NANOSTRUCTURED/AMORPHOUS DIFFUSION BARRIERS FOR COPPER METALLIZATION

Abstract

This work examines the thin-film properties and diffusion barrier behaviors of thin Ta-Co films, aiming at depositing highly crystallization-resistant and highly conductive diffusion barriers for Cu metallization. Structure analyzing indicates that the deposited Ta-Co films indeed have a glassy structure and are free from highly resistive intermetallic compounds, thus giving a low resisitivity under 20 mu Omega-cm. Examining Si/Ta-Co/Cu stacked samples by using 4-point probes and XRD reveals that thermally induced failure of amorphous Ta-Co barriers are triggered by the barrier\'s crystallization at temperatures just under around 600 degrees C. The effectiveness of the nanostructure/amorphous Ta-Co thin film thus can be substantially enhanced by effectively blocking diffusion of copper towards the underlying silicon.