Electromigration in width transition copper interconnect

Electromigration (EM) experiments are conducted for submicron dual damascene copper interconnects with width transition. The direction of electron flow (from narrow-to-wide segment and wide-to-narrow segment) and the ratio of lengths (e.g. ratio of narrow-to-wide segment lengths) are found to be significant factors in determining the life-time of such interconnects. About 69% shorter EM life-time is obtained for the case of electron flow from narrow-to-wide segment, and thus to avoid over estimation of EM life-time of such interconnect system, the direction of the electron flow should be chosen appropriately in the reliability assessment. On the other hand, it is found that the width transition location is not the failure site, and finite element model is presented to explain the experimental findings.