A novel fabrication method for suspended high-aspect-ratio MEMS structures

The high-aspect-ratio structures (HARS) are widely used for MEMS devices such as micro-gyroscope, micro-accelerometer, optical fiber switches, and so on. Various fabrication methods, such as SOI (Indermuehle et al., 1994), SCREAM (Shaw et al., 1994) and SBM (Lee et al., 1999) processes, were proposed to fabricate HARS. However, these methods are focus on the fabricating suspended microstructures with small trench openings (e.g., less than 10 μm), which often limits the maximum in-plane displacement of the structures. In this paper, we propose a low-cost single-mask, single ICP-RIE process for fabricating suspended MEMS structures which have the characteristics of arbitrary sizes of trench openings, very high trench aspect ratio (about 20) and very large structure thickness (about 100 μm). Also, the proposed process potentially can be used to fabricate the devices for large in-plane-displacement applications.