Recovery of open via after electromigration in Cu dual Damascene interconnect

The recovery of open failure in a Cu dual Damascene via chain after electromigration stress test is reported. An infrared microscope system is introduced to monitor hot spots in the via chain. It is observed that hot spots could develop and fade during electromigration stressing. Furthermore, via that has opened up during stress test could recover after subsequent storage. Stress current density and storage temperature affect the time to recovery. It is proposed that backflow under compressive stress is the responsible mechanism.