Diagnostic electromigration reliability evaluation with a local sensing structure

EM reliability evaluations generally rely on monitoring an EM test structure resistance increase caused by void formation during current stress. With technology scaling, the height and width of interconnects are shrinking. Therefore, the base resistance of EM test structures increases substantially, and the detection of the absolute resistance change caused by the same size of void at the latest technology nodes becomes very challenging. In this paper, an improved EM test structure based on a local resistance sensing concept is developed and evaluated. With this new test structure and associated method, the location of local void formation can be electrically determined, the details of void evolution can be more fully characterized, and a great improvement of void detection sensitivity can be achieved.