# Design, Modeling, and Fabrication of a High-Q AlN Annular Gyroscope with Sub-10°/h Bias Instability

## TL;DR

This paper introduces a high-performance, lead-free MEMS gyroscope with a record quality factor and low bias instability, suitable for precision motion sensing.

## Contribution

The paper presents a high-Q aluminum nitride MEMS gyroscope with sub-10°/h bias instability and a novel analytical model for transduction optimization.

## Key findings

- The gyroscope achieves a quality factor of 75,000, the highest for silicon-based piezoelectric gyroscopes.
- It demonstrates a bias instability of 8.19°/h and an angle random walk of 0.34°/√h.
- The device uses lead-free aluminum nitride, meeting RoHS environmental standards.

## Abstract

This work presents a high-performance piezoelectric MEMS yaw gyroscope fabricated on a single-crystal silicon platform, which achieves a quality factor of 75 k—the highest reported to date among silicon-based piezoelectric gyroscopes. The device employs a wide annular resonator that operates at 132 kHz in the in-plane wineglass mode. To maximize transduction efficiency, we develop an analytical model that relates output charge to the area-integrated in-plane stress under modal deformation, and we use this model to guide parametric optimization of the annular width. The resulting geometry simultaneously enhances the mechanical quality factor and the piezoelectric coupling. A back-etching fabrication process is used to eliminate front-side release holes, thereby preserving structural continuity and suppressing thermoelastic damping. In open-loop rate mode operation with a native frequency split of 28 Hz, the gyroscope demonstrates an angle random walk of 0.34°/√h and a bias instability of 8.19°/h. These performance metrics are comparable to those of state-of-the-art lead zirconate titanate (PZT)-based annular gyroscopes, while the use of lead-free aluminum nitride as the transduction material ensures compliance with RoHS environmental regulations.