Cu interconnects have decreased in width and are at around 100 nm. A decrease in interconnect width have led to a predominately bamboo structured Cu lines. In Cu interconnects, void formation during high temperature is a reliability issue, and this study looks at the void formation behavior in damascene Cu interconnects with a predominately bamboo microstructure. First, the crystal texture and grain morphology of the Cu interconnects was observed. Then to determine the void formation behavior, in-situ Transmission Electron Microscopy (TEM) was performed. Voids that formed as a result of in-situ heating were analyzed in terms of preferential void formation sites and crystal orientation where voids formed. In bamboo structured lines, voids formed at the triple junction of grain boundary and Cu/diffusion barrier interface. The crystal orientation where voids nucleated was studied to identify diffusion paths during void nucleation and growth.
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An, J.H., Ferreira, P.J. In-situ TEM Study of Thermally Induced Voids in 180 nm Cu Interconnects. MRS Online Proceedings Library 907, 303 (2005). https://doi.org/10.1557/PROC-0907-MM03-03