Ultrahigh-aspect-ratio SiO₂ deeply etched periodic structures with smooth surfaces for photonics applications

One-dimensional Si O2 deeply etched periodic structures were fabricated. The fabrication process was based on an anisotropic Si etching, followed by a direct oxidation of the etched Si structure. The obtained submicron-scale Si O2 periodic structure had an ultrahigh aspect ratio of 16 for the etched space and an etching depth of as large as 12.5 μm. The etched depth was limited only by the etching mask. Therefore, increasing the mask thickness, or replacing it with a much harder mask material, should result in a much larger aspect ratio and etching depth. This structure also had an excellent vertical profile of less than 0.5° and extremely smooth surfaces of only 0.6 nm rms suitable for use in various applications, particularly in photonics fields that require a broad band performance, ranging from ultraviolet to near infrared.