Via resistance reduction in advanced copper interconnects

Via resistance reduction in Cu interconnects was achieved through a pre-liner dielectric nitridation process prior to pure Ta liner deposition. Replacing TaN with Ta in the conventional liner stack reduces Cu via resistance, while the nitridation treatment maintains the interconnect integrity and reliability. Comprehensive evaluations including adhesion tests, parametric measurements, and electromigration evaluations of the pre-liner dielectric nitridation process were carried out to confirm the feasibility of reducing via resistance in advanced-node Cu/ultralow-k back-end-of-the-line interconnects.