Transmission Electron Microscopy Study of the Failure Mechanism of the Diffusion Barriers (TiN and TaN) Between Al and Cu

Abstract

Failure mechanisms of transition metal nitride thin film diffusion barriers, such as TiN and TaN (10 nm in thickness), between Al and Cu were investigated by transmission electron microscopy (IEM), scanning transmission electron microscopy, and energy dispersive spectroscopy. After annealing at 450 degrees C during 30 min, the TiN diffusion bather initially failed due to an interfacial reaction between TN and Al forming TiAl3. When the annealing temperature was increased to 500 degrees C,degrees Cu-Al intermetallic compounds were formed by the inter diffusion of Al and Cu through the diffusion barrier. In the case of the Al/TaN/Cu structure, no interfacial reaction products were observed after annealing up to 550 degrees C. On the other hand, it failed after annealing at 550 degrees C due to the inter-diffusion of Cu and Al through the diffusion barrier. TEM also identified Cu to be the rapid diffusing species in both systems. The results are discussed based on the thermodynamic stability of the interface predicted by the ternary phase diagram and the diffusion kinetics of Al and Cu through the diffusion bather. The results show that both the thermodynamic stability of the diffusion barrier between Al and Cu and the diffusion kinetics of Al and Cu through the diffusion barrier, which are dependent on the microstructure of the diffusion barrier, should be considered carefully when selecting diffusion barrier materials between Al and Cu.