Through-Silicon-Via (TSV) Filling by Electrodeposition of Cu with Pulse Current at Ultra-Short Duty Cycle

Through-Si-via (TSV) filling with electrodeposited Cu was performed with a pulse current consisting of very a short duty cycle to achieve 3D interconnection in high density integrated circuit (IC) devices. Low frequency was unacceptable in this condition, because a highly acidic electrolyte attacked the seed layer and Cu deposit obtained with low current efficiency during comparably longer off time period. An increased frequency critically enhanced the filling rate of Cu, which was mainly related to the improvement of the current efficiency and lower dissolution rate. In pulse conditions, high density nanoscale twin structure and strain fields were observed, which were caused by induced stress during the on-time because of high peak current density. Application of pulse deposition reduced thermal extrusion of Cu that was related to the imperfect microstructure of the deposited Cu.