Effect of W-plug via on electromigration lifetime of metal interconnect

The effect of W-plug via on electromigration (EM) lifetime of the metal interconnects with bamboo structure and single/multiple vias has been systematically investigated by using high resolution resistance measurement (HRRM). It is found that the vias added in the structure significantly change its resistance degradation profile. W-plug vias not only cause discontinuity at the interface between metal and W-plug, but also make the metal stripe near W-plug via to be more vulnerable to electromigration, further reducing EM lifetime of metal stripe. This finding raises doubt about the assumption that adding multiple vias will proportionately prolong interconnect lifetime in a circuit design.