Strategy to Characterize Electromigration Short Length Effects in Cu/low-k Interconnects

With the increasing amount of on-chip interconnects and continuous down-scaling, electromigration will play a more critical role especially for automotive reliability, which requires high statistical confidence. In confined metal lines, tensile stress builds up at the cathode side before void nucleation; compressive stress builds up at the anode side. A critical stress is required for EM-induced void formation to occur. Proper understanding of the critical stress is crucial for boosting interconnect RC performance, yet guaranteeing robust electromigration reliability. This study aims to characterize the short length effect and physical degradation behavior with a modified Wheatstone Bridge structure to significantly increase the statistical confidence.