Effect of Wire Thickness on Electromigration and Stress Migration Lifetime of Cu

Electromigration and stress migration lifetimes are characterized as a function of metal thickness for Cu interconnects fabricated using 0.13 mum process technology. The stress migration lifetime decreases as metal thickness decreases, consistent with previous studies. The electromigration lifetime shows a more complicated dependence on metal thickness. For vias landing on narrow lines, the electromigration lifetime can actually be longer for thin wires (50 nm) than for thick wires (400 nm), because the via is more likely to touch the liner of the underlying metal as wire thickness decreases. In contrast, for vias landing on wide lines (and for vias landing on narrow lines at short stress times), the electromigration lifetime is independent of wire thickness