Small grain and twin characterization in sub-100 nm Cu interconnects using the conical dark-field technique in the transmission electron microscope

The introduction of future technology nodes is accompanied by further downscaling of the interconnect dimensions resulting in the growth of Cu grains with a grain size that is significantly smaller than 100 nm. Consequently, well established techniques for orientation imaging microscopy reach their resolution limit for sufficient Cu microstructure characterization. The only suitable alternative is given by transmission electron microscopy, and particularly, by applying the conical dark-field (CDF) technique which provides complete grain orientation maps. With a proven spatial resolution of better than 5 nm, various interconnect structures with Cu twins and agglomerates of small Cu grains are analyzed by the CDF technique.