$\bf ZrAl_{3}$ Intermetallic Compound Thin Film as a Diffusion Barrier between Al and Au Layers

A layer of intermetallic compound ZrAl3 of 100 nm thickness functioning as a diffusion barrier between Al and Au thin films was investigated. The performance of the barrier was characterized by in situ monitoring of electrical resistance during heating under vacuum. The value of sheet resistance remained constant up to about 340 degrees C; then it increased gradually to a maximum at about 550 degrees C. The increase of resistance reflected the occurrence of interactions between thin films. With the aid of Auger electron spectroscopy depth profile and X-ray diffraction analyses, it was found that the degradation of the ZrAl3 barrier layer was mainly attributed to the diffusion of Al through ZrAl3 grain boundaries, reacting with Au to form Au5Al2 initially on the surface at 300 degrees C. As temperature was increased further, AuAl2 was found at the Au/ZrAl3 interface.