Electromigration in dual damascene Cu interconnects was investigated using package level electromigration tests and failure analysis techniques. Interface diffusion along Cu/Si3N4 interface was found to be the dominant electromigration path. The effect of a reservoir at the Cu via region upon the electromigration performance was studied by using via-fed 2-layer test structures with various extension lengths above the via. An improvement in electromigration failure times was observed with increasing reservoir length; consistent with the mechanism of vacancy movement along the Cu/Si3N4 interface.

Electromigration in Copper Damascene Interconnects - Reservoir Effects and Failure Analysis. W.Shao, A.V.Vairagar, C.H.Tung, Z.L.Xie, A.Krishnamoorthy, S.G.Mhaisalkar: Surface and Coatings Technology, 2005, 198[1-3], 257-61