A metallurgical prescription for electromigration (EM) reliability improvment in scaled-down, Cu dual damascene interconnects

Electromigration (EM)-derived, void-nucleation and its growth have been investigated in 65-nm node, dual damascene interconnects (DDIs), and the effects of impurity-doping as well as adhesion-strength to SiCN-capping layer (CAP) are discussed regarding the EM-reliability improvement. It is found that reductive surface-treatment of Cu line improves the adhesion to the SiCN-CAP, elongating the incubation time of voiding at the via-bottom. The Al-doping is effective in suppressions both of the void nucleation and the growth, or the drift velocity. Consequently, the Al-doped, dilute Cu-alloy with the strong interface of the Cu/CAP improves the EM lifetime by 50 times refer to that of the conventional pure-Cu. Blocking all migration paths in Cu DDIs is essential for the EM-reliability improvement in 65nm-node LSIs and beyond