A gyroscope fabrication method for high sensitivity and robustness to fabrication tolerances

Abstract

MEMS gyroscopes have favorable characteristics, including small size, high throughput, and low cost. The performance of MEMS gyroscopes depends on the displacement sensitivity of the capacitors. In this paper, we describe the fabrication of 300-µm-thick gyroscopes that can provide high displacement sensitivity and are robust to fabrication tolerances, i.e. deep reactive ion etch (DRIE) rate uniformity. When thick structures are perforated using DRIE to achieve high-aspect-ratio features, footing is commonly observed. However, we describe a fabrication method that circumvents problems associated with footing and side-wall etching, so that the gyroscopes can have uniform dimensions and small variations across the wafer. Using a post-fabrication translation approach, the position of capacitors is modified following DRIE, and the gap in the gyroscopes can be reduced to 3 μm, which leads to an aspect ratio of 100. Using this method, we fabricated MEMS gyroscopes that can overcome the DRIE aspect ratio limit and have capacitors with higher sensitivities than those of other gyroscopes, which typically employ substrates that are less than 100 µm thick. The gyroscope had a resonant frequency of 9.91 kHz, a quality factor of 2500 and a sensitivity of 23 mV/[deg/s].

Design, Analysis and Experimental Results of Micromachined Single-structure Triaxis Vibratory Gyroscope with Advanced Coupling Mechanism

“…5 and 6, respectively. (13,14) The gyroscope and circuit were tested with a rate table (1270VS-230, Ideal Aerosmith, USA) and the output data were obtained with a LabVIEW data acquisition system (PCIe-6363, NI, USA).…”

System Modeling of a MEMS Vibratory Gyroscope and Integration to Circuit Simulation

“…This MEMS gyroscope has a high aspect ratio structure, resulting in large capacitance and, thus, high-sensitivity, despite a simple and intuitive structure [23]. The basic concept of this gyroscope is shown at Figure 1a.…”

CMOS MEMS Fabrication Technologies and Devices

“…Recently, to address the etching deterioration caused by the thermal effect first reported in [ 75 ], some new approaches, including multiple step etching [ 77 , 78 ], and backside coating of a metal layer to provide thermal dissipation path [ 79 , 80 ]. A CMOS MEMS accelerometer, gyroscope and micromirror with large mirror plate have been fabricated using the further improved methods, respectively.…”

“…In demonstration of the integrated gyroscope in [ 78 ], the authors employed TMAH backside anisotropic silicon etching to mitigate the undercut on SCS in the comb drives resulting from the footing effect in front side DRIE. A SiO 2 layer by wet oxidation was coated in the trenches formed by front DRIE etching.…”