A two-dimensional microstructure with low reflectance was fabricated on the surface of an SiO2 plate by the precise regulation of its shape and surface morphology. A periodically dotted mask pattern of a positive resist was formed on SiO2 by a two-beam interference method using a He-Cd laser with a wavelength of 325 nm. The substrate was rotated by 90° between the first and second irradiation steps. The microstructure of SiO2 was etched using an electron cyclotron resonance plasma. The reflection loss was effectively minimized by overcoating an SiO2 thin film on the microstructure followed by chemical etching in an HF solution. Steady fabrication of subwavelength structures (SWSs) having a reflectance less than 0.1% was possible by using these surface treatment methods.
2003 The Ceramic Society of Japan