Thermomechanical Fatigue in Two Level Cu Interconnects Under Pulsing Peak Current

This study reports on the thermomechanical fatigue behavior of two-level Cu interconnects under surge current conditions. Standard two-level Cu interconnects of varying dimensions were subjected to high-density, shortduration current pulses, with resistance evolution monitored as a failure indicator. Experimental and computational analyses reveal that interconnect width and thickness significantly influence failure susceptibility, highlighting the roles of localized Joule heating, thermal expansion mismatch, and plastic deformation in damage progression. Additionally, the results indicate the existence of a critical current density (or power density) below which fatigue failure does not develop, suggesting an endurancelike behavior in Cu interconnects. The study also emphasizes the importance of considering temperature effects, as recovery and recrystallization may counteract the accumulation of plastic energy, thereby suppressing fatigue failure. These findings provide critical insights into the fundamental fatigue mechanisms of Cu interconnects and inform design strategies for improving their resistance to transient high-current events in semiconductor applications.