Trade-off between reliability and post-CMP defects during recrystallization anneal for copper damascene interconnects

Thermal treatments of electroplated copper films before CMP can increase grain size and therefore reduce resistance and improve electromigration reliability. However, high temperature excursions can also increase the stress levels in thick metal layers due to differential thermal expansion, which in turn can increase the occurrence of post-CMP defects such as pullouts and line voids. In this paper, we discuss this trade-off between electromigration and defects and the influence of plating chemistry and barrier layer on reducing this tradeoff.