Analysis of electric field distribution and its influence on dielectric failures in asymmetric copper interconnect structures

The distribution and impact of the electric field which results in dielectric breakdown in asymmetric copper interconnect structures has been studied based on finite element method (FEM) simulations. It has been demonstrated that the electric field concentration points in asymmetric via-involved structures are quite different from those in traditional line-to-line symmetric structures. That is to say, the weak points, or the paths of leakage current, are very different during backend dielectric breakdown. Reliability problems might also result from this vulnerability. Backend time-dependent dielectric breakdown (TDDB) test and failure-mode analysis were also performed to support these simulation results. TDDB performance was worse in asymmetric structures than that in traditional structures. It could possibly be a potential concern for TDDB reliability of porous low-k films in future continuous scaling technology.