Electromigration-limited lifetime of aluminum bond pads

The semiconductor industry has replaced aluminum by copper metallization because copper has a stronger electromigration resistance combined with lower resistivity. Since all the design current has to go through the aluminum bond pads, the electromigration robustness of the bond pads plays a decisive role. For reliable product operation, knowledge of the maximum current which can be carried by the bond pads is absolutely necessary. Furthermore, the product area can be minimized by an optimization of the number of pads. In this work, tests have been performed to characterize the bond pads regarding the influence of pad design, current path, probing and aluminum thickness on the electromigration properties.