Electromigration in Dual-Damascene CuMn Alloy IC Interconnects

Electromigration reliability of Cu interconnects is an important issue for continued performance improvement of IC technologies. In this paper, we investigate the impact of Mn impurities on the electromigration drift velocity of Cu conductors. Under accelerated test conditions, the drift velocity in CuMn alloys is reduced by an order of magnitude compared with pure Cu with polycrystalline microstructure. Dilute CuMn alloys exhibit a large activation energy for drift of 1.05 eV, which is significantly increased above that for pure Cu as a result of a 0.2 eV impurity(Mn)-vacancy binding energy. There is no measurable impact of the presence of the Mn dopant on diffusion along the Cu/dielectric cap interface in the samples studied here.