Bonded Cu interconnects were stressed with increasing current while the contact resistance was measured. Interconnects with high initial contact resistance exhibited a contact resistance reduction phenomenon at a critical current density. The higher the initial contact resistance is, the lower the current required to trigger this phenomenon. Interconnects with low initial contact resistances exhibit this phenomenon only when stressed at a higher temperature. Electromigration is shown to be the most likely mechanism responsible for this phenomenon. This behavior can be used for low-temperature improvement of the quality of bonded interconnects for three-dimensional integrated circuits.