Studies of accelerated electromigration were conducted on passivated Al single-crystal interconnects fabricated on oxidized Si, and capped withAl3Tioverlayers. The capping layers were formed by the reaction of the single-crystal Al films with Ti overlayers. The activation energy for electromigration-induced failure was determined to be0.94±0.05 eV.Previous work on Al single-crystal interconnects withoutAl3Tioverlayers gave an activation energy of0.98±0.2 eVand lifetimes of similar magnitude [Y.-C. Joo and C. V. Thompson, J. Appl. Phys.81, 6062 (1997)]. The similarity of these results suggests that either the rate-limiting mechanism for electromigration-induced failure of single-crystal Al interconnects is not diffusion along the interface of the Al with the surrounding oxide and overlayer, or that, surprisingly, the diffusivity of Al along theAl/Al3Tiinterface is approximately the same as, or lower than, the diffusivity of Al along theAl/AlOxinterface. ©1998 American Institute of Physics.