Stability of Glassy Ta-Rh Diffusion Barriers for Cu Metallization

Abstract

Amorphous Ta-Rh thin films were studied as diffusion barriers for Cu metallization. Thermodynamic calculations were performed to predict the glass forming ability of the Ta-Rh system. Various compositions were deposited by co-sputtering from two targets and the theoretically predicted amorphization range was confirmed by structural characterization using XRD and TEM observations. These calculations provide a useful guide for selecting a glass forming composition suitable for diffusion barrier applications for Cu metallization. The selected composition was studied as a diffusion barrier in contact with Cu and Si. A 13 nm-thick Ta 0.45 Rh 0.55 film is effective at temperatures up to 550°C, whereupon it dissociates into its constituents followed by formation of RhSi.