Control of Crystallographic Growth Orientation and Twinning Structure in Copper Nanowires by Template-Assisted Electrodeposition

Abstract

Synthesis and characterization of noble metal nanowires have been a popular topic in the field of microelectronic devices and catalysts. Nanotwinned copper nanowires (nt-CuNWs) possess high mechanical strength, excellent electromigration resistance and low electrical resistivity, which have been considered as a promising interconnect material in ultra-large scale integrated circuits (ICs). Here, we deposited nt-CuNWs in two different anodic aluminum oxide (AAO) templates with respective pore sizes of 70 nm and 35 nm pore by pulse electrodeposition. The influence of thermal treatment on the Cu seed layer deposited on AAO membranes prior to electrodeposition is investigated. Both coarse and thin nt-CuNWs mainly grew in <111> crystallographic direction with (111) texture coefficients (TC(111)) > 2.5, and an aspect ratio (AR) > 100 according to x-ray diffraction analysis. An addition of gelatin (14 ppm) in the copper sulfate electrolyte is found to suppress the growth of (220)-oriented Cu grains in the AAO by forming copper nanowires with large TC(111) > 2.65 and high-density nanotwin structure. This study provides a simple route to tailoring microstructure and physical properties of nanoscale copper wires, which is beneficial for the interconnect technology development in semiconductor IC devices.