Fabrication of high-density copper microstructures using vacuum ultraviolet light lithography and hydrofluoric acid etching treatment

This paper describes a method to fabricate high-density copper microstructures on an indium tin oxide (ITO) surface. Lithography using 172-nm vacuum ultraviolet (VUV) light was found to not decompose the siloxane network at the bottom of a methyl-terminated organosilane self-assembled monolayer (SAM) deposited on an ITO substrate. When copper was electrodeposited onto this ITO surface covered a SAM/siloxane network pattern, it deposited selectively onto the siloxane regions. However, the density of the electrodeposited copper was low. By applying a wet hydrofluoric (HF) acid treatment for an appropriate time after the lithography, we could effectively remove the siloxane network without damaging the organosilane SAM. In this manner, we were able to successfully fabricate high-density copper microstructures with 35×35 μm² patterns.