Analysis of electromigration-induced failures in multilayered interconnects

The authors studied electromigration-induced failures in multilayered interconnects with overlayer TiN in conjunction with the overlayer-TiN/Al heterointerface evaluation. The electrical contact resistance between Al and TiN changes with fabrication processes. The contact between Al and underlayer TiN shows almost the same resistance as Al/Al direct contact. On the other hand, the contact between overlayer TiN and Al shows higher resistance compared with that of Al/Al direct contact; its value varies with the deposition processes. That is, overlayer-TiN/Al structure successively deposited without breaking vacuum shows one order of magnitude higher contact resistance, while overlayer-TiN/Al structure deposited after Al was exposed to air shows two orders of magnitude higher contact resistance compared with Al/Al direct contact. The high contact resistance between overlayer TiN and Al suppresses the current bypass flow even when it is one order of magnitude higher compared with that of Al/Al direct contact. The simple multilayered structure of overlayered TiN/Ti/Al exhibits high reliability for submicrometer-level interconnects