High resolution nanofabrication using self-assembly of metal salt-polymer nanocomposite film

Abstract

For fabrication of nanostructures that do not need long range ordering and precise placement, such as antireflective structure for photovoltaic and display applications and super-hydrophobic surface for lab-on-chip applications, bottom-up fabrication techniques are more preferable than top-down techniques due to their low cost. Here, the authors report a simple process to obtain nanostructures using low-cost spin-coating method and pattern transfer. They first dissolved metal salt and polymer in a solvent. After spin-coating to form a thin film, the authors annealed the film to attain a phase separation. Next, the nanocomposite film was etched with oxygen plasma to remove the polymer matrix, leaving behind nanoscale metal salt islands that can be used as a hard mask for dry etching the substrate or sublayer. With optimal metal salt (nickel nitrate hexahydrate) and polymer (polymethylmethacrylate) weight ratio, the authors achieved wafer-scale high resolution (down to 20 nm) pillar structures etched in silicon with 100 nm height and ∼100 nm spacing.