Simple lithographic approach for subwavelength structure antireflection

A simple lithographic method is developed to generate large-area antireflective subwavelength structures (SWSs), in which the metal island films are used as masks. Using magnetron sputter deposition, stochastically arranged Ag islands were fabricated on Si substrates with dimensions controlled in the range of 50 similar to 400 nm. After reactive ion etching with CF4, Si SWSs were formed, with the same arrangement and density as those of Ag islands. The measured reflectivity was decreased from similar to 40% for polished Si to similar to 5% for Si SWS surfaces. The residual reflection was thought to be mainly from the bottoms of U-shape grooves. (c) 2007 American Institute of Physics.