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In-situ SEM electromigration studies were performed at fully embedded via/line interconnect structures to visualize the time-dependent void evolution in inlaid copper interconnects. Void formation, growth and movement, and consequently interconnect degradation, depend on both interface bonding and copper microstructure. Two phases are distinguished for the electromigration-induced interconnect degradation process: In the first phase, agglomerations of vacancies and voids are formed at interfaces and grain boundaries, and voids move along weak interfaces. In the second phase of the degradation process, they merge into a larger void which subsequently grows into the via and eventually causes the interconnect failure. Void movement along the copper line and void growth in the via are discontinuous processes, whereas their step-like behavior is caused by the copper microstructure. Directed mass transport along inner surfaces depends strongly on the crystallographic orientation of the copper grains. Electromigration lifetime can be drastically increased by changing the copper/capping layer interface. Both an additional CoWP coating and a local copper alloying with aluminum increase the bonding strength of the top interface of the copper interconnect line, and consequently, electromigration-induced mass transport and degradation processes are reduced significantly.

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The electrical degradation of ultra low-k SiCOH dielectric before breakdown is investigated. A new technique to obtain information before breakdown has been developed to define stress conditions and observe degradation patterns before total destruction occurs. Electrical measurements and physical inspection in specifically designed test structures have been made to focus on intrinsic properties. A typical leakage current characteristic, voiding and tantalum transport have been observed. These observations have been interpreted by quantitatively adapting physical effects. This investigation provides a model that describes the observed phenomena in a qualitatively manner.

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