A High-Resolution Silicon-on-Glass $Z$ Axis Gyroscope Operating at Atmospheric Pressure

Abstract

This paper describes a high-resolution silicon-on-glass <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</i> axis gyroscope operating at atmospheric pressure. The mechanical structure is designed in such a way that it exhibits low cross coupling between drive and sense mode of less than 0.5% simulated using finite-element method and 1.35% verified by experimental measurements. Due to a symmetrically designed structure, the specified bandwidth can be maintained despite of fabrication imperfections. The fabrication process flow is based on a combination of silicon on glass bonding and deep reactive ion etching which results in a large proof mass and capacitances. A closed loop self-oscillation drive interface is used to resonate the gyroscope in the drive mode, which reaches steady-state after 150 ms. Using area-varying capacitors, large quality factors of 217 and 97 for drive and sense mode, respectively, were achieved operating at atmospheric pressure. A low drive voltage, with a 1 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">peak-peak</sub> AC drive amplitude and 10 V DC bias was used to excite the drive mode. The measured scale factor was 10.7 mV/°/s in a range of ±300°/s with a <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> -nonlinearity of 0.12%. The noise equivalent angular rate is 0.0015°/s/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> (=5.4°/h/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> ) in a 50 Hz bandwidth. The measured SNR was 34 dB at an angular rate input signal with an amplitude of 12.5°/s and a frequency of 10 Hz. Without any active temperature control, zero bias stability of 1°/s was achieved for long-term measurements over six hours and 0.3°/s for short-term measurements over 120 seconds (1-¿).