Microstructural Analysis of Electromigration-Induced Voids and Hillocks

Abstract

ABSTRACTInterconnect reliability is of continuing concern in modem VLSI circuits. This work presents analyses of the microstructural detail in electromigration-induced damage in Al and Al-Cu unpassivated interconnects. Such failure analysis is crucial for the characterization of the fundamental processes responsible for failure. Results, via TEM, SEM and focussed-ion beam techniques, suggest possible second phase precipitate-void growth interactions, show slit-like open circuit failures in narrow interconnects, and illustrate the microstructures of hillocks and whiskers formed during accelerated electromigration testing. These results are discussed in terms of existing models for electromigration failure processes and lifetimes. The results are further intended to suggest mechanisms for future modelling and to direct the design of more reliable interconnect material systems.