Effective Cu surface pre-treatment for high-reliable 22 nm-node Cu dual damascene interconnects with high plasma resistant ultra low-k dielectric (k = 2.2)

Effects of Cu surface treatment (NH3 plasma irradiation) before the cap dielectric deposition on low-k surface damage and Cu surface cleaning were systematically investigated. From the blanket film surface damage evaluations of porous low-k film with high carbon content and the oxygen removal on blanket Cu film after chemical mechanical polishing (CMP), the optimized NH3 plasma condition such as high RF power and high pressure exhibited the high efficiency for oxygen removal from the Cu surface without increasing the k-value of low-k film. The low-k/Cu interconnect (line/space = 40/40 nm) for 22 nm-node with the high plasma resistant low-k film and the optimized Cu surface treatment showed longer electro-migration lifetime without large degradation of RC performance.