100K Q-factor toroidal ring gyroscope implemented in wafer-level epitaxial silicon encapsulation process

Abstract

This paper reports a new type of degenerate mode gyroscope with measured Q-factor of > 100,000 on both modes at a compact size of 1760 μm diameter. The toroidal ring gyroscope consists of an outer anchor ring, concentric rings nested inside the anchor ring and an electrode assembly at the inner core. Current implementation uses n = 3 wineglass mode, which is inherently robust to fabrication asymmetries. Devices were fabricated using high-temperature, ultra-clean epitaxial silicon encapsulation (EpiSeal) process. Over the 4 devices tested, lowest as fabricated frequency split was found to be 8.5 Hz (122 ppm) with a mean of 21 Hz (Δf/f = 300 ppm). Further electrostatic tuning brought the frequency split below 100 mHz (<; 2 ppm). Whole angle mechanization and pattern angle was demonstrated using a high speed DSP control system. Characterization of the gyro performance using force-rebalance mechanization revealed ARW of 0.047°/√hr and an in-run bias stability of 0.65 deg/hr. Due to the high Q-factor and robust support structure, the device can potentially be instrumented in whole angle mechanization for applications which require high rate sensitivity and robustness to g-forces.