Reliability of Cu Interconnects with Ta Implant

In this study, a novel method is explored for improving the electromigration lifetime of Cu wires, using a blanket Ta implantation into both the oxide and Cu on the surface of a wafer. For the highest implant dose, the electromigration lifetime is improved by over 5X using this method, with a minimal increase in wire resistance. An increase in lifetime is achieved, even for an average surface concentration of Ta on the order of 0.1 atm%. The line-to-line leakage at high voltages (> 5 V) increases with the Ta implant, with higher leakage at higher Ta concentrations. The lifetime for time dependent dielectric breakdown (TDDB) is significantly degraded for high Ta doses, but not for lower Ta doses, suggesting that there may be a window for improving electromigration lifetime while maintaining high dielectric reliability.