In situ secondary electron microscope characterizations were carried out to study electromigration failure mechanism in dual-damascene Cu interconnect tree structures, which were important for reliability assessment as well as design optimizations of on-chip interconnects. Direct evidence of electromigration-induced degradation in interconnect tree structure consisting of void nucleation and void movement in opposite direction to electron flow along the Cu/SiNx interface was unravelled. The peculiar electromigration behavior of Cu interconnect tree structures could be clearly understood based on this mechanism. Dependence of electromigration mechanism of a segment in a Cu interconnect tree on current configuration in neighboring interconnect segment was discussed in detail.

Direct Evidence of Electromigration Failure Mechanism in Dual-Damascene Cu Interconnect Tree Structures. A.V.Vairagar, S.G.Mhaisalkar, M.A.Meyer, E.Zschech, A.Krishnamoorthy, K.N.Tu, A.M.Gusak: Applied Physics Letters, 2005, 87[8], 081909 (3pp)