Synethesis of Single-crystal Cu Via for BEOL Interconnect

This study reports the vertical growth of single-crystal Cu with a sub-100 nm scale to address the size-effect challenges in nanometer-scaling Cu interconnects. Single-crystalline Cu nanowires (NWs) were synthesized using a reverse-pulse potentiodynamic electrochemical deposition method, and the effects of the reduction potential and the frequency on NW morphology and diameter were analyzed, respectively. Higher reduction potentials enhanced the nucleation, leading to smaller grain sizes, while the frequency controlled the NW diameter. TEM and SAED analyses exhibited the single-crystalline 〈111〉 growth in the longitudinal direction. Additionally, single-crystalline Cu NWs were successfully filled into the PMMA-defined Via nanostructures, suggesting a possibility for improvement in electrical performance in a nanoscale Via interconnect. This approach is expected to offer a new route for Cu interconnect technology in BEOL.