Restraint of Copper Oxidation Using Barrier Restoration Technique with Cu–Mn Alloy

Abstract

This paper clarifies for the first time that employing Cu–Mn alloy can reduce the resistance of ultralarge scale integration (ULSI) interconnects. It is well known that Cu alloys have higher resistance than pure Cu. However, recent discussion indicates that Cu or barrier metal oxidation by moisture from interlayer dielectrics causes electrical resistance to increase even further. Therefore, Cu oxidation must be prevented. Previously, we have reported a barrier restoration technique using Cu–Mn alloy, and the application of this technique is expected to result in strong tolerance to Cu oxidation. In this work, we investigated the property that copper is protected from oxidation when using the barrier restoration technique with Cu–Mn alloy. This property results in the reduction of interconnect resistance and the improvement of the resistance distribution in ULSI interconnects. We conclude that using the barrier restoration technique with Cu–Mn alloy will be being compatible with further scaling to 22 nm node and beyond.