CU interconnect immortality criterion based on electromigration void growth saturation

The ever increasing scaling down of IC leads to ever more current density in interconnects. As a consequence, electromigration (EM) becomes a concern in interconnect reliability. In order to face this problem and allow more current density in design, one can take advantage of the Blech effect. Many investigations have proposed extraction methods, behaviors or values for the threshold jL_c product but some controversies subsist in particular on failures under jL_c. We studied the resistance saturation with time to characterize Blech effect of Cu/low-k dual damascene interconnects from the 65 nm node. We propose an immortality criterion proportional to the jL² product based on the limitation of EM induced void volume at steady state. In our case, this criterion leads to more relaxed current rules for short lines compared to jL_c criterion.