Scaling effect on electromigration in copper interconnects

Electromigration in Cu dual damascene interconnections has been investigated in terms of metal line width and thickness. The failure lifetime was found to decrease with decreasing line thickness and width. Furthermore, electromigration lifetime was greatly decreased as the line width was decreased to 0.07 m width. In addition to interface diffusion, the microstructure of Cu can be the dominant path for electromigraton mass transport. As a result, as the generation is scaled down to below 45 nm technology, electromigration behaviour will limit allowable current in the integrated circuit. In this study, the process improvement actions including the new copper surface passivation and bamboo-like Cu microstructure are presented and demonstrated an improvement electromigration performance.