MEMS blazed gratings fabricated using anisotropic etching and oxidation sharpening

Micro-electro-mechanical system (MEMS) blazed gratings are the critical optical elements in high resolution micro-spectrometer systems. The MEMS blazed gratings fabricated by conventional methods are not ideal saw-tooth profiles. After the photolithographic and anisotropic etching process, a tiny platform of silicon will be left on the top of the grating groove because of the silica mask, which will lead to amounts of stray light and reduce the diffraction efficiency of gratings. This paper presents a novel design and fabrication method for fabricating MEMS blazed grating, which utilizes off-cut silicon (111) wafers. The blazed angle of gratings is revised from 7.54° to 8.0° according to the tiny platform width on the top of grating grooves. In the procedure of grating fabrication, the oxidation sharpening method is used to cut down the width of the tiny platform. The experimental result shows that the platform width of the grating groove has sharpened from 1000 nm to 540 nm, and the fabricated blazed grating has high diffraction efficiency. The result indicates that the process to fabricate blazed gratings through the anisotropic etching and oxidation sharpening technology is quite effective.