A Resonant Pressure Sensor Based upon Electrostatically Comb Driven and Piezoresistively Sensed Lateral Resonators

Abstract

This study proposes a microfabricated resonant pressure sensor in which a pair of double-ended tuning forks were utilized as resonators where comb electrodes and single-crystal silicon-based piezoresistors were used for electrostatic excitation and piezoresistive detection, respectively. In operations, pressures under measurements deform the pressure-sensitive diaphragm to cause stress variations of two resonators distributed on the central and side positions of the pressure-sensitive diaphragm, where the corresponding changes of the intrinsic resonant frequencies are then captured piezoresistively. The developed resonant pressure sensors were fabricated based on MEMS with open-loop and closed-loop characterizations conducted. Key sensing parameters including quality factors, differential pressure/temperature sensitivities and fitting errors were quantified as higher than 17,000, 48.24 Hz/kPa, 0.15 Hz/°C and better than 0.01% F.S. (140 kpa), respectively. In comparison to previously reported resonant pressure sensors driven by parallel-plate electrodes, the developed sensor in this study is featured with a lower temperature sensitivity and a higher stability.

Resonant Pressure Micro Sensors Based on Dual Double Ended Tuning Fork Resonators

“…In comparison to previous resonant pressure micro sensors based on electrostatic excitation and capacitive detection (e.g., Xie [7], Sun [8]), the sensors developed in this study were featured with lower crosstalk and thus higher SNRs. In comparison to the counterparts based on electrostatic excitation and piezoresistive detection (e.g., Shi [13], Shi [17]), the sensor developed in this study demonstrated higher SNRs, higher differential sensitivities, wider working temperature ranges and lower device dimensions due to structure optimization. In addition, the DETF resonators can operate in the anti-phase mode, which ensures that the proposed sensors demonstrate higher pressure cycling performances (e.g., shift, hysteresis and repeatability error) than what was reported in [8].…”

“…In order to compare the SNRs of the proposed sensor with previously reported counterparts, the outputs of three types of resonant pressure sensors in responses to excitation signals from 50 to 150 kHz with bias voltages of 20 V were measured under atmospheric pressure (~ 100 kPa) and room temperature (~ 22 °C). As shown in Figure 5c, the developed sensor demonstrates a high SNR of 67.64 dB compared with 54.00 dB (Shi’s sensor [17]) and 38.33 dB (Xie’s sensor [7]). Note that, the sensors based on electrostatic excitation/piezoresistive detection shows lower noise levels due to the negligible crosstalk between the detection electrode and driving electrode compared with the sensor based on electrostatic excitation/capacitance detection.…”

“…However, two silicon-silicon bondings and one anodic bonding were required in the fabrication, which was extremely complicated and suffered from limited yield. In order to simplify the device fabrication process, in our group, silicon on insulator (SOI)-based fabrications and wafer-level vacuum packaging were adopted to form resonant pressure micro sensors based on electrostatic excitation/piezoresistive detection [13,17]. However, the key parameters of the sensor structures were not optimal, which led to lower SNRs and compromised performances.…”

Si-based MEMS Resonant Sensor: A Review from Microfabrication Perspective

“…(c) proto-type view of resonator with a dimension of 7 Ö 7 mm2. (d) resonant sensor mounted on top of a covar-header [142]. Kuo et al [143]integrated a multiple sensor on a single innovative System-on-chip design resonator structure.…”

Novel resonant pressure sensor based on piezoresistive detection and symmetrical in-plane mode vibration

“…DRUCK 16 proposed a novel structure that eliminates adjacent output signals, such as the first mode output; however, numerous beams are used, and thus the resulting structure is complex. Shi et al 17 proposed another beam combination structure by setting the piezoresistive detection beam at the end of the resonant beam, and the beam combination structures have good shielding ability for adjacent modes, but the resonator quality factor was only~10,000 with vacuum packaging. Welham et al 15 proposed the use of two straight beams as coupling and detection beams for shielding the adjacent mode, and the increase in the stiffness owing to the coupling beam decreases the sensitivity.…”