Void formation in a copper-via-structure depending on the stress free temperature and metallization geometry

The understanding of degradation phenomena in dual-damascene (DD) copper metallization structures, due to high current densities and temperatures, in reliability stress tests has been an important challenge during the past decades. The determination of the mass transport pathway is a major point of concern. Electromigration for instance can occur through a number of different pathways like the surface, the interface, and the grain boundaries. The reliability prediction, due to the different migration mechanisms like electro- thermo- and stress migration as well as the different migration paths, becomes more and more important and has to be considered. In this study, the void formation, as well as the mass flux divergence distribution out of the static simulations, in a copper metallization was investigated by finite element simulation (using ANSYS®). A calculation routine is used for the determination of the mass flux divergences and void formation in the model.