A 0.5MHz mode-matched pitch or roll annulus gyroscope with nano-gap slanted electrodes for quadrature cancellation

Abstract

This paper presents, for the first time, the effective quadrature cancellation in a high-frequency pitch or roll bulk acoustic wave (BAW) gyroscope to enable perfect mode-matching for sensitivity improvement and noise reduction. The presented gyroscope has a high operation frequency of 0.5MHz and high translational stiffness for shock and vibration robustness. Quadrature cancellation, which is the biggest challenge in high-performance pitch or roll gyroscopes, is achieved by incorporating nano-gap slanted electrodes through the new HARPSS+ fabrication process, which combines anisotropic wet-etching of silicon with conventional DRIE-based HARPSS process. The HARPSS+ process enables precision capacitive transduction and tuning in all desired orientations, providing tuning coverage over typical process corners and significantly improving the yield of pitch or roll gyroscopes. Quadrature cancellation is verified on fabricated devices, allowing a perfectly mode-matched operation with a scale factor of 95.2pA/(°/s) and an open-loop bandwidth of 15Hz. The HARPS S+ process also enables simultaneous fabrication of single-chip tri-axial BAW gyroscopes: high-frequency (0.5–5MHz) gyroscopic modes with high quality factors (10,000s–100,000s) are measured on both yaw and pitch/roll BAW gyroscopes on the same wafer.