A Novel Comb Architecture for Enhancing the Sensitivity of Bulk Mode Gyroscopes

Abstract

This work introduces a novel architecture for increasing the sensitivity of bulk mode gyroscopes. It is based on adding parallel plate comb drives to the points of maximum vibration amplitude, and tuning the stiffness of the combs. This increases the drive strength and results in a significant sensitivity improvement. The architecture is targeted for technologies with ∼100 nm transducer gaps in order to achieve very high performance devices. In this work, this sensitivity enhancement concept was implemented in SOIMUMPs, a commercial relatively large gap technology. Prototypes were measured to operate at frequencies of ∼1.5 MHz, with quality factors of ∼33,000, at a 10 mTorr vacuum level. Measurements using discrete electronics show a rate sensitivity of 0.31 μV/°/s, corresponding to a capacitance sensitivity of 0.43 aF/°/s/electrode, two orders of magnitude higher than a similar design without combs, fabricated in the same technology.

Bulk Mode Disk Resonator With Transverse Piezoelectric Actuation and Electrostatic Tuning

“…The achieved motional resistance is a key advantage for the device presented in this work, as it results in significant simplification of the associated electronics for realizing complete systems (e.g., oscillator and phase locked loop in [1]) resulting in lower power consumption and phase noise. The performance demonstrated here is achieved without the need for submicron gaps, as in [3], [4], and [9]- [13], or high DC polarization voltages, as in [14]- [18]. In fact, the device requires no DC voltage for its operation.…”

“…As for electrostatic resonators, they rely mostly on vibratory resonance, either in a flexural or bulk mode. Bulk-mode devices typically exhibit high stiffness, and are consequently less prone to thermoelastic damping, compared to flexural devices, allowing them to achieve large quality factors (>10,000), even at atmospheric pressure [9]- [18]. However, electrostatic actuation causes these resonators to exhibit lower electromechanical transduction efficiency and significant signal transmission loss, leading to higher motional resistance than typical piezoelectric devices.…”

“…However, electrostatic actuation causes these resonators to exhibit lower electromechanical transduction efficiency and significant signal transmission loss, leading to higher motional resistance than typical piezoelectric devices. This can however be mitigated by increasing the applied DC polarization voltage and utilizing sophisticated technologies to realize very thin lateral transduction gaps (<100 nm) (e.g., [9]- [18]). Electrostatic resonators can also benefit from the electrostatic spring softening phenomenon to allow for tuning the resonance frequency by varying the polarization voltage.…”

“…In [14] and [15], the devices had to operate at high voltages (>50 V) in order to overcome the dimension limitations on the transducer gap imposed by the technology. In [17] and [18], combs were added to the bulk-resonating structure in order to improve overall sensitivity and allow for operation at lower voltage, at the expense of increased area.…”

A Sub-mW 18-MHz MEMS Oscillator Based on a 98-dBΩ Adjustable Bandwidth Transimpedance Amplifier and a Lamé-Mode Resonator

“…Resonators can be classified based on their vibration modes as either flexural or bulk-mode devices. Bulk-mode devices typically exhibit high stiffness, and are consequently less prone to thermoelastic damping, compared to flexural devices, allowing them to achieve large quality factors (>10,000), even at atmospheric pressure [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]. In [2,3,4,5,6,7], bulk-mode resonators including Lamé-mode and wine glass mode devices with quality factors in the 106 range were presented based on capacitive actuation.…”