Electrodeposition and Growth Mechanism of Nanotwinned Copper in High Aspect-Ratio via Structures

Despite nanotwinned copper (nt-Cu) having many fascinating physical/chemical properties, controlling twin density and orientation in the electrodeposited nt-Cu remains challenging, especially for high aspect-ratio Cu vias. Here, an array of nt-Cu nanowires (aspect ratio > 150) with dense coherent twin boundaries (CTBs) perpendicular to the length direction were deposited in porous anodic aluminium oxide vias by pulse electrodeposition. By changing pulse on/off duration, we control the degree of (111) growth texture and twinning structure of the nt-Cu nanowires. It was found that a small anodic current in the pulse-off period enhances (111) crystal texture and CTB formation probability during the bottom-up filling process. We propose that nanoscale twinning is activated by facet-dependent crystal growth and stress accumulation/relaxation behavior during pulse deposition. This study shall enable the implementation of high aspect-ratio nt-Cu interconnects in nanoelectronic devices and nanoelectromechanical systems.