Initial void formation in bamboo Al-Cu(1%) two-level structure

Abstract

As the interconnect line width reduces to the sub-micron range, the grain distribution of Al-Cu(1%) alloy lines reaches a bamboo structure. Understanding of the electromigration resistance of bamboo structure is essential to the sub-micron interconnect reliability issue. In this study, initial void formation in 1 μm wide Al-Cu(1%) two-level lines with bamboo structure was investigated using scanning electron microscopy (SEM) and focused ion beam (FIB) microscopy. The results show that voids always initiate from line edges in slit-like shape or wedged shape, which indicate that interfacial diffusion coupled with grain boundary diffusion controls the void initiation.