Low Resistance and High Electromigration Lifetime of Cu-To-Cu Joints Using (111)-Oriented Nanotwinned Copper

Cu-to-Cu joints of 30 mm in diameter were fabricated using (111)-oriented nanotwinned copper at 300 °C for 20 min in N₂ ambient. The joints possess excellent electrical properties. The average resistance and specific contact resistivity are 4.1 mΩ and 3.98 × 10 _-8 Ω·cm ₂ , respectively for an as-fabricated Cu joint. With a second step annealing at 400 °C, the resistance can be reduced to 3.27 mΩ due to grain growth across the joint interface. There is 50% resistance reduction compared to SnAg solder joints with the same diameter. The electromigration lifetime for Cu-to-Cu joints is at least 750 times longer than solder joints.