EFFECTS OF TEMPERATURE, THICKNESS AND ATMOSPHERE ON MIXING IN AU-TI BILAYER THIN-FILMS

The interdiffusion and intermetallic compound formation of Au-Ti bilayer thin films annealed at 1 25 to 350-degrees-C have been investigated. The bilayer thin films were prepared through electron beam deposition at comparatively low temperature. The interdiffusion of annealed specimens was examined by measuring electrical resistance and the depth-composition profile, and by observation using a transmission electron microscope. Interdiffusion between the thin films was detected at temperature above 175-degrees-C in a vacuum of 10(-4) Pa. The starting temperature at which interdiffusion occurred decreases with lowering annealing vacuum. The intermetallic compounds AuTi, Au4Ti, AU2Ti and Ti3Au form during annealing at over 250-degrees-C. The activation energies of Au in Ti and Ti in Au obtained by the penetration depth are approximately 0.45 and 0.41 eV, respectively. These measurements indicate that the diffusion is controlled by a short-circuit mechanism. The diffusion of Ti species in Au depends on the annealing vacuum and Au thickness.