Antireflective Hydrophobic Si Subwavelength Structures Using Thermally Dewetted Ni/SiO₂ Nanomask Patterns

We report the disordered silicon (Si) subwavelength structures (SWSs), which are fabricated with the use of inductively coupled plasma (ICP) etching in SiCl₄ gas using nickel/silicon dioxide (Ni/SiO₂) nanopattens as the etch mask, on Si substrates by varying the etching parameters for broadband antireflective and self-cleaning surfaces. For the fabricated Si SWSs, the antireflection characteristics are experimentally investigated and a theoretical analysis is made based on the rigorous coupled-wave analysis method. The desirable dot-like Ni nanoparticles on SiO₂/Si substrates are formed by the thermal dewetting process of Ni films at 900 °C. The truncated cone shaped Si SWS with a high average height of 790 ± 23 nm, which is fabricated by ICP etching with 5 sccm SiCl₄ at 50 W RF power with additional 200 W ICP power under 10 mTorr process pressure, exhibits a low average reflectance of ∼5% over a wide wavelength range of 450–1050 nm. The water contact angle of 110° is obtained, indicating a hydrophobic surface. The calculated reflectance results are also reasonably consistent with the experimental data.