A New Stress Migration Failure Mode in Highly Scaled Cu/Low-$k$ Interconnects

We identify a new stress migration (SM) failure mode in Cu/low-
k
interconnects whereby voids are formed in very narrow trenches close to large Cu plates. Finite-element analysis shows that the new failure mode is generated by large stress gradients associated with geometry changes in highly scaled Cu interconnects. This work indicates that management of mechanical stresses will be an important issue for future development of reliable Cu/low-
k
interconnects.