Using the NH3 flush step to prevent Cu extrusion for improving stand-by current performance for 28nm-node Cu interconnect and beyond

Abstract

The stand-by current (Isb) performance is impacted by the failure of Cu interconnects due to Cu extrusion forming Cu-loss. This paper provides the solution to overcome the formation of Cu-loss without modifying via etching reactant to keep the capability of via etching tuning. Cu-loss strongly depends on the existence of Cu-F produced by via etching process. By inserting the NH3 flush step, Cu-F is completely removed. Moreover, 5 times the queue time extension is achieved. The Isb failure by Cu-loss is obviously exterminated.