Comparison of Electromigration in Submicron Al(Cu) and Cu Thin Film Lines

Electromigration lifetime is compared for SiO(sub2)-passivated 0.35 um wide Al(Cu), and 0.90 um Cu lines connected by four vias to underlying W lines using both drift velocity and resistance techniques. Void growth at the cathode was the primary cause of electromigration line failure. Activation energies for electromigration in Cu and Al(0.5%Cu) were found to be 1.22 eV and 1.06 eV, respectively. Lifetime for Cu were at least two orders of magnitude longer than that of Al(Cu) in test temperature range of 300 to 400 degrees C, at current density of 2x10(sup6)A/cm(sup2). Values of the log-normal deviation, sigma, of the time to failure for both Cu and Al(Cu) lines for these multi-stud test structures ranged from 0.4 to 1.