Electrodeposition of Nano-Twinned Cu and their Applications in Electronics

Twin boundaries are planar defects between two domains exhibiting mirror symmetry. Nano-twinned metallic materials contain numerous twin boundaries in parent grains exhibiting submicrometer twin spacing. Owing to their unique mechanical and electrical properties, nano-twinned metals have been studied extensively. Although the mechanical strength of the metal can be drastically increased by shrinking grains, nanocrystalline metals lose their ductility (i.e., the strength–ductility tradeoff), and their electrical conductivity is considerably lowered owing to electron scattering at dense grain boundaries. However, nano-twinned metallic materials can overcome these limitations and exhibit excellent strength, ductility, and electrical conductivity. In this paper, the structure and properties of nano-twinned Cu films are reviewed, and direct current and pulse electrodeposition for forming twin boundaries in Cu films and controlling the twin structure and thickness are summarized. Furthermore, the applications of nano-twinned Cu materials for fabricating electronics are presented.