Microstructure Effect on Electromigration-Induced Degradation of Inlaid Copper Interconnects

Abstract

Electromigration‐induced degradation processes in via/line dual inlaid copper interconnect test structures are discussed based on experimental studies. Void formation, growth and movement, and consequently interconnect degradation, depend on both interface bonding and copper microstructure. Void movement along the copper line and void growth in the via are discontinous processes, wherein their step‐like behavior is caused by copper microstructure. Microstructure studies and microstructure monitoring are becoming more important for strengthened top interfaces of copper lines, e. g. by local alloying of the copper or by applying an additional coating on top of the polished copper lines. As a result of this interface engineering, the contribution of grain boundary diffusion becomes increasingly important for the directed mass transport and for electromigration‐induced degradation.