Optimized process of metal assisted silicon wet etching for antireflection layer

Abstract

► A simple fabrication technique for silicon subwavelength structure is proposed. ► Au nanoparticles are an excellent catalyst to wet etching. ► Au nanoparticles were fabricated using the metal self-aggregation effect. ► Particle size was adapted with initial Au film thickness before annealing. ► Reflectance of etched Si was almost 0% for the wavelength from 300 to 1300 nm. In this study, a simple fabrication technique for silicon (Si) subwavelength structure (SWS) by means of chemical wet etching using Au nano particles directly formed on silicon substrates was proposed and optimized. Single nano-sized Au particles were fabricated using the metal self-aggregation effect. The deposition and thermal annealing of the metallic thin film were undertaken. The thermal annealing of the metallic thin film enables the creation of metal nano particles by isolating them from each other through the self-aggregation of the metal. It was found that the initial Au film thickness can affect the particle size and change the etching conditions such as the fill factor, inter-particle distance, and so on. Then, samples were soaked in an aqueous etching solution of hydrofluoric acid and hydrogen peroxide. When using the optimized process parameters, although Si etching was only 2 min in duration, the reflectance decreased to approximately 1% in the whole wavelength range from 300 to 1300 nm due to the deep and steep double tapered structure.