In situ trench etching and releasing technique of high aspect ratio beams using magnetically enhanced reactive ion etching

This article describes an in situ trench etching and releasing technique to fabricate high aspect-ratio beams for high performance microelectromechanical systems (MEMS) accelerometers using magnetically enhanced reactive ion etching (MERIE) technique. In the conventional process, lateral encroachment due to the release etching is severe underneath the SiO 2 etching mask. In this process, the sidewall of the beams was passivated by inhibiting layers formed during the HBr / SiF 4 / O 2 trench etching, and the beams were not attacked by the subsequent SF 6 release etching. Auger electron spectroscopy showed the etch inhibiting layer to consist mostly of Si and O. This was also confirmed by x-ray photoelectron spectroscopy as SiO x (1