Bimodal electromigration mechanisms in dual-damascene Cu line/via on W

Electromigration in 0.23 μm wide Cu dual-damascene lines connected to W underlayers has been investigated. Void growth at the vicinity of the cathode end of the line/via was determined to be the cause of the line failure. The distribution of failure lifetimes was found to be closely represented by a two-log-normal function. Focused ion beam analysis showed that the two failure populations had distinct difference in the location of the void growth.