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A high-performance silicon-on-insulator MEMS gyroscope operating at atmospheric pressure

This paper presents a new, high-performance silicon-on-insulator (SOI) MEMS gyroscope with decoupled oscillation modes. The gyroscope structure allows it to achieve matched-resonance-frequencies, large drive-mode oscillation amplitude, high sense-mode quality factor, and low mechanical cross-talk. The gyroscope is fabricated through the commercially available SOIMUMPS process of MEMSCAP Inc. The fabricated gyroscope has minimum capacitive sense gaps of 2.6 mu m and a structural silicon thickness of 25 mu m, and it fits into a chip area smaller than 3 mm x 3 mm. The fabricated gyroscope is hybrid connected to a CMOS capacitive interface ASIC chip, which is fabricated in a standard 0.6 mu m CMOS process. The characterization of the hybrid-connected gyroscope demonstrates a low measured noise-equivalent rate of 90 degrees/h/Hz(1/2) at atmospheric pressure, eliminating the need for a vacuum package for a number of applications. R-2-non-linearity of the gyroscope is measured to be better than 0.02%. The gyroscope has a low quadrature signal of 70 degrees/s and a short-term bias stability of 1.5 degrees/s. The angular rate sensitivity of the gyroscope is 100 mu V/(degrees/s) at atmospheric pressure, which improves 24 times to 2.4 mV/(degrees/s) at vacuum. The noise-equivalent rate of the gyroscope at 20 mTorr vacuum is measured to be 35 degrees/h/Hz(1/2), which can be improved further by reducing the electromechanical noise.