Antireflective silicon subwavelength structure formed by self-aggregated gold nano particle as a catalyst

A subwavelength structure (SWS) was formed by simple chemical wet etching using two types of gold (Au) catalysts to compare the etching speed due to difference of fill factor. One sample is an Au thin film that has an almost 100% fill factor; the other is comprised of Au nano particles that have an approximately 50% fill factor. Single nano-sized Au particles were fabricated by metal self-aggregation effect. The deposition and the thermal annealing of the metallic thin film were carried out. The thermal annealing of a metallic thin film enables the creation of metal nano particles by isolating them from each other by means of the self-aggregation of the metal. Then, samples were soaked in an aqueous etching solution of hydrofluoric acid and hydrogen peroxide. When Si etched for 20min using the Au thin film, the reflectance decreased to about 8%. But, when Si etched just 3min using the Au nano particle, the reflectance decreased below 3%; with an added 10min etching, the reflectance decreased almost to 0% in the whole range from 300 to 900nm owing to the deep and steep double tapered structure.