A HARPSS polysilicon vibrating ring gyroscope

This paper presents the design, fabrication, and testing of an 80-mum-thick , 1.1 mm in diameter high aspect-ratio (20:1) polysilicon ring gyroscope (P RG). The vibrating ring gyroscope was fabricated through the high aspect-ra tio combined poly and single-crystal silicon MEMS technology (HARPSS), This all-silicon single-wafer technology is capable of producing electrically i solated vertical electrodes as tall as the main body structure 50 to 100's (mum tall) with various size air-gaps ranging from submicron to tens of mic rons. A detailed analysis has been performed to determine the overall sensi tivity of the vibrating ring gyroscope and identify its scaling limits. An open-loop sensitivity of 200 muV/deg/s in a dynamic range of +/- 250 deg/s was measured under low vacuum level for a prototype device tested in hybrid format. The resolution for a PRG with a quality factor (Q) of 1200, drive amplitude of 0.15 mum, and sense node parasitic capacitances of 2 pF was me asured to be less than 1 deg/s in 1 Hz bandwidth, limited by the noise from the circuitry. Elimination of the parasitic capacitances and improvement i n the quality factor of the ring structure are expected to reduce the resol ution to 0.01 deg/s/(Hz)(0.5).