Joule heating-assisted electromigration failure mechanisms for dual damascene Cu/SiO2 interconnects

Failure mechanisms observed in electromigration (EM)-stressed dual damascene Cu/SiO₂ interconnect trees were studied by stressing at fixed conditions for a short time followed by stressing with increasing current to induce Joule heating. Similar failure sites as those observed in samples stressed at normal EM conditions were found. This suggests that Joule heating can be used to accelerate some EM failure mechanisms that occur in normal EM experiments. Finite element method (FEM) simulation showed that the failure mechanisms could be due to Joule heating of Ta diffusion barrier after fully-spanning void was formed. The probabilistic existence of the post-stress ´volcano craters´ and melt patches is highly dependent on the void growth mechanism during EM stressing.