Back-end-of-Line (BeoL) Reliability has been a major concern at least since electromigration (EM) was first identified in the late 1960s as a critical failure mechanism within integrated circuits. Typically, reliability concerns arose because simple technology scaling placed larger current density demands on the metallization system. To slow down the erosion of reliability margin with scaling, Cumetallization using Dual-Damascene (DD) integration was introduced around the 180/130nm node. In addition, low-kdielectrics (2.5 <~ k <~ 3.0) were later incorporated into DD integration schemes to keep in check the negative impact of of interconnect RC delay.
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