Electrical resistivity and microstructural evolution of electrodeposited Co and Co-W nanowires

Abstract

As the design rule of the integrated circuits is decreasing to a 10 nm scale, the total electrical resistance of conventional Cu metallization increases rapidly. New conducting materials such as Co with shorter electron mean free paths, have gained significant attention and may replace Cu. Further, CoW alloys are being considered as alternatives to replace the TaN/Ta barrier layers. However, limited studies have been carried out to elucidate electrical resistivity changes in nanoscale Co and its alloys depending on the size and composition. In this study, we report the variations in electrical resistivity and the microstructural evolution of a series of single Co nanowires (NWs) prepared using template-assisted electrochemical deposition, with diameters ranging from 16 to 130 nm. Besides, we investigate CoW alloy NWs with W content ranging from 0 to 25.1 at.%. The Co NWs, in all diameter ranges, show substantially lower resistivity values compared to that in previous reports, where the value of an NW with a diameter of 16 nm is approximately 40 μΩ∙cm. The grain size also decreases as NW diameter decreases. Alloying W with Co NWs increases electrical resistivity. The 30 nm diameter CoW alloy NW with 25.1 at.% W shows the highest electrical resistivity value at 170 μΩ∙cm. This value decreases as post-deposition annealing temperature increases.