Effect of copper addition on electromigration behavior of silver metallization

This study investigates the effect of Cu alloying on electromigration behavior of Ag metallization. Electromigration tests are performed on pure Ag and Ag (1.5% Cu) samples deposited by e-beam evaporation. The experiments show that Ag (Cu) alloy interconnect has superior elctromigration resistance compared to pure Ag interconnect. X-ray diffraction, four point probe measurements and electron microscopy were used to investigate the test structures and corresponding thin film samples. The Cu improves the lifetime of interconnect test structures by hindering Ag diffusion and increasing {111} texture of Ag. Also, Cu addition seemingly reduces the agglomeration in Ag.