25 nm Single-Crystal Silicon Nanowires Fabricated by Anisotropic Wet Etching

We report a top-down method for fabricating ultra-high aspect ratio single-crystal silicon nanowires. The fabrication method is based on the standard photolithography technique and anisotropic wet etching of the single-crystal silicon in KOH solution. SiO₂ mask nanolines used for patterning single-crystal silicon nanowires are formed by the undercut etching of thin SiO₂ layer in buffered hydrofluoric solution. The minimum width of the SiO₂ mask nanolines are 50 nm. The length of SiO₂ mask nanolines is 2 cm. The single-crystal silicon nanowires have been successfully transferred from the SiO₂ mask nanolines by KOH anisotropic wet-chemical etching. The minimum width of the silicon nanowire has obtained to be 25 nm. The fabricated single-crystal silicon nanowires have trapezoidal and triangular cross sections, which are useful for applications in nanoelectronic and nanophotonic elements.