Released submicrometer Si microstructures formed by one-step dry etching

Microstructures with submicrometer gaps in Si were fabricated by etching with Cl2 and F-based gases in inductively coupled plasma systems. Released cantilevered beams with a 0.1 μm gaps and 4 μm thick were fabricated using Cl2 etching. Etching in Cl2 provides vertical profile and smooth morphology for submicrometer trenches. It has been applied to form a clamped–clamped beam resonator with 0.2 μm gaps between the resonating beam and electrodes. For trenches with 0.1 μm openings, the F-based etching resulted in tapered etch profile and the top of the trenches was eventually closed due to polymer deposition. Based on faster lateral etch rate for n++ Si in Cl2 etching, a one step dry etching process was used to pattern and release microstructures from the substrate. Residues on the surface after F-based etching can be removed by overetching and the charging effect can be avoided by etching in Cl2.