Effect of NH3/He Plasma Treatment on Electromigration Behavior and Electrical Reliability of Copper Interconnects

Abstract

Electromigration reliability tests of Cu interconnect structures with or without an NH3/He plasma treatment have been performed in this study at 400oC under a high current density of 8 MA/cm2 to clarify the effect of plasma treatment on the interface structure, early-stage electromigration behavior and electrical reliability of interconnects. From cumulative failure probabilities, small shape factors and large median time to failure were obtained for the interconnects with the plasma treatment, indicating an improved electromigration resistance. The oxide layer on Cu surface was removed, and an alternative CuSiN interlayer with a lattice spacing of 0.195 nm formed at the Cu/SiCN interface, enhancing interface adhesion and reducing the diffusion paths of Cu atoms. Therefore, voids nucleated inside the Cu wires, rather than at the interface. The change in the Cu/SiCN interface structure varied the early-stage electromigration-induced voiding behavior and effectively improved the electrical reliability of the Cu interconnect structures.