A 3D-HARPSS Polysilicon Microhemispherical Shell Resonating Gyroscope: Design, Fabrication, and Characterization

Abstract

This paper presents, for the first time, the analysis, design, fabrication, and characterization of a microhemispherical resonating gyroscope ( $\mu $ HRG). A 3D high aspect-ratio poly- and single-crystalline silicon (HARPSS) process is developed to fabricate a stem-supported hemispherical shell with self-aligned tall capacitive electrodes intended for driving, sensing, and tuning of the gyroscope. The monolithic process consists of seven lithographic steps combining the HARPSS process with fabrication of a 3D curved microstructure to create electrodes with scalable capacitive gaps. The fabrication is successfully demonstrated with polysilicon $\mu $ HRG prototypes with a diameter of 1.2 mm and a shell thickness of 1 $\mu \text{m}$ . The frequency response is measured and gyro operation is examined using the integrated electrodes. Mode matching and mode alignment are successfully performed by applying tuning and quadrature nulling voltages. A closed-loop rate sensitivity scale factor of 8.57 mV/°/s was measured. Furthermore, design and process optimization of the support structure resulted in an improved quality factor ( $Q \sim 40\,000$ ).