The hydrogenated Silicon nitride film is well developed to form a passivation layer for non-volatile memory devices. It has many superior chemical, electrical, and mechanical properties. In addition, it also has excellent optical properties. It is transparent in UV and DUV range, with a high refractive index of about 1.7~2. Owing to its superior mechanical and optical properties, we used a hydrogenated silicon nitride (SiNXHY) membrane as an optical phase element. By using e-beam lithography, we demonstrate on feasibility for the fabrication of subwavelength optical elements, such as waveplate, polarizer, and polarized beam splitter on a silicon-based low stress SiNXHY membrane for the UV region applications. An SiNXHY film was deposited by plasma enhanced chemical vapor deposition (PECVD) and the free- standing membrane is formed by KOH silicon backside etching, from which substrate materials are removed. The membrane's morphology and geometries of subwavelength optical elements were verified by means of an scanning electron microscope (SEM), and the optical performance characteristics of these subwavelength optical elements are shown. The experimental datas agree well with theoretical predictions.
Silicon nitride (SiNX) film is a commonly used material in silicon technology. In addition, it has excellent optical properties. It is transparent in both the UV and visible range, with a high refractive index of about 1.7~2. Owing to its superior mechanical and optical properties, we used a silicon nitride membrane as an optical phase element. We will fabricate nano-structured diffractive optical elements, such as wave-plate, polarizer, and polarized beam splitter on SiNXHY membrane by e-beam lithography for the UV-visible regime applications. The SiNXHY membranes were made from SiNXHY films deposited by an plasma enhanced chemical vapor deposition (PECVD) as an alternative method for low stress membrane fabrication used in UV-visible transmittance. The stress of silicon nitride film showed a change from compressive to tensile with increasing working pressure during film deposition. The UV-visible transmittance of the free standing membrane was measured, which showed that UV light is transparent at wavelength as short as 240nm. We will show the feasibility to fabricate nano-structured diffractive optical elements on the SiNXHY membrane combined with microoptoelectromechanical systems (MOEMS) technology for the application in the UV-visible regimes.