Reliability Testing of Advanced Interconnect Materials

Abstract

We describe the development of electrical test methods to evaluate damage that determines reliability in advanced, small‐scale conductors, including damascene copper and aligned carbon nanotube networks. Rapid thermal cycling induced during high‐current AC stressing provides a means for measuring lifetimes associated with cyclic plasticity and/or diffusive damage in damascene copper. The specific type of damage that develops depends on the line geometry and the nature of the stress state induced within the lines during cycling. Voids form in both fully passivated and partially passivated lines under high levels of hydrostatic tension. Dislocation activity takes place in partially passivated lines in the presence of high shears. High‐current DC stressing provides a means for evaluating the fabrication quality of aligned carbon nanotube (CNT) networks, in what we believe to be the first lifetime degradation tests of such materials. While classic electromigration is unlikely in nanocarbon, we observed through resistance changes two forms of degradation that we believe are tied to the nanotube packing and resulting conduction path density through the network: a gradual build‐up of damage, and a more abrupt, unpredictable form of damage accumulation, which may be linked to sudden changes in network morphology due to stressing.