Line-width dependency on electromigration performance for long and short copper interconnects

Experiments were performed to study the effect of metal line width on electromigration characteristics for Cu interconnects, and the results revealed completely different electromigration behavior for long and short metal lines. The extracted critical current density jc due to back stress effect can explain the electromigration width effect for long and short metal lines. For long metal lines, the electromigration times to failure were found to be increased with increasing the line width, and the critical current density jc is lower and slightly increased for the wider metal line. On the other hand, the electromigration failure time was observed to be inversely proportional to the line width in the case of short metal lines. Moreover, the back stress effect was decreased with increasing the line width, leading to the decreasing critical current density jc. These observed effects are specific to Cu technology and can have major technological implications for electromigration assessment.