Investigation on anchor and base design for aluminum nitride flexural mode resonators

Abstract

This paper investigates the impact of base and anchor on the quality factor (Q) of piezoelectric MEMS tuning fork resonators vibrating in in-plane flexural mode, and proposes a new strategy to improve Q significantly. Finite element method simulation and measured results reveal that base and anchor geometries have a significant impact on the thermoelastic damping (TED) which dominates the overall resonator quality factor. For the first time, we accurately extract Q value related to TED of piezoelectric tuning fork resonators by cryogenic temperature experiment, which is consistent with FEM simulation results. According to the analysis, a wider anchor or a longer base should promote overall Q by restraining the thermal conduction induced by TED. On the other hand, increase of width or length of anchor will force the out-of-plane flexural modes closer to the target mode, reducing the overall Q by multimode effect. With a wide anchor and a pillar structure under the base to suppress multimode effect, the resonator Q could be improved by 65% to more than 11000 and impedance at series resonant frequency (fs) could be reduced by 78% to 6.5 kΩ. To our knowledge, the proposed resonator exhibits the highest f×Q and lowest motional impedance among the reported in-plane mode piezoelectric MEMS tuning fork resonators.

Flexural-Mode Piezoelectric Resonators: Structure, Performance, and Emerging Applications in Physical Sensing Technology, Micropower Systems, and Biomedicine

“…Utilizing a very highfrequency detection technology based on a phase-locked amplifier, they discovered that piezoelectrically excited ZnO NW can operate at a resonant frequency of 417. 35 MHz and a quality factor of 3010 under room-temperature conditions. To enhance the test's accuracy, the sensor's sensitive area was positioned at the midpoint of the resonant beam Piezoelectrically excited ZnO resonant gas sensor platforms offer several advantages, such as compact size, low power consumption, sensitive response, and convenient array implementation.…”

“…Resonant structure vibration’s coupling with the surrounding environment typically results in diverse types of energy dissipation governed by numerous internal and external mechanisms [ 35 , 69 ]. Common external energy dissipation examples include contact loss, clamping loss, surface modification loss, thermoelastic loss, air friction, and miscellaneous dissipation caused by various excitation methods [ 70 , 71 ].…”

“…Flexural-mode piezoelectric resonators (FMPRs) are a novel resonator type that have garnered significant attention due to their unique characteristics and wide-ranging application potential [ 7 , 34 , 35 ]. The resonant frequency of FMPRs, like that of other FMRs, can be tuned using distinct active tuning methods such as external excitation [ 36 ] or local bias force [ 37 ].…”