This letter presents a MEMS resonant differential pressure sensor with an integrated temperature sensor and a static pressure sensor to address the issue of side effects of temperature and static pressure on measurement accuracies of resonant differential pressure microsensors. In this microsensor, two resonators were employed on the pressure sensitive diaphragm to sense differential pressure while a Pt-film-resistor was included as the temperature sensor and an additional resonator was positioned on the framework as the static pressure sensor. Microfabrication was conducted to manufacture the resonant microsensor and key performances were quantified as 79.76 Hz/kPa (~1036 ppm/kPa) of differential pressure sensitivity, 6.22 Ω/°C of temperature sensor sensitivity and –0.47 Hz/kPa of static pressure sensor sensitivity. Based on compensations of temperature and static pressure, a measurement accuracy of 0.02%FS was achieved for the developed microsensor under the differential pressure range from 0 to 100 kPa, the temperature range from –20°C to 60°C and the static pressure range from 110 kPa to 200 kPa.

This paper presents a resonant pressure microsensor with a wide range of pressure measurements. The developed microsensor is mainly composed of a silicon-on-insulator (SOI) wafer to form pressure-sensing elements, and a silicon-on-glass (SOG) cap to form vacuum encapsulation. To realize a wide range of pressure measurements, silicon islands were deployed on the device layer of the SOI wafer to enhance equivalent stiffness and structural stability of the pressure-sensitive diaphragm. Moreover, a cylindrical vacuum cavity was deployed on the SOG cap with the purpose to decrease the stresses generated during the silicon-to-glass contact during pressure measurements. The fabrication processes mainly contained photolithography, deep reactive ion etching (DRIE), chemical mechanical planarization (CMP) and anodic bonding. According to the characterization experiments, the quality factors of the resonators were higher than 15,000 with pressure sensitivities of 0.51 Hz/kPa (resonator I), −1.75 Hz/kPa (resonator II) and temperature coefficients of frequency of 1.92 Hz/°C (resonator I), 1.98 Hz/°C (resonator II). Following temperature compensation, the fitting error of the microsensor was within the range of 0.006% FS and the measurement accuracy was as high as 0.017% FS in the pressure range of 200 ~ 7000 kPa and the temperature range of −40 °C to 80 °C.

This paper presented a temperature-insensitive resonant pressure microsensor where silicon based resonators anchored on a pressure-sensitive diaphragm were vacuum packaged by a silicon cap based on eutectic bonding. Incoming pressures deformed the pressure-sensitive diaphragm and built stresses around resonators for frequency modulation while under temperature challenges, deformations of silicon based resonators and the vacuum cap were consistent and thus no stresses were generated on resonators. The temperature-insensitive resonant pressure microsensor was analyzed in both theoretical analysis and numerical simulations with confirmed high pressure sensitivities and low temperature disturbances. The resonant pressure microsensor was then fabricated by key steps of photolithography, deep reactive ion etching, and eutectic bonding and characterized in both open-loop and close-loop testing systems. Characterization results showed that the quality factors of resonators were $\sim 10000$ with pressure sensitivity of 82.98 Hz/kPa and temperature disturbance of −0.63 Hz/° (the lowest result among previously reported resonant pressure microsensors). In summary, the temperature-insensitive resonant pressure microsensor developed in this study exhibited a fitting accuracy better than 0.02% FS within the pressure range of 10 to 120 kPa and the temperature range of −45 to $85^{\circ }\text{C}$ .

This article presented a high-sensitivity resonant differential pressure microsensor based on wafer-level eutectic bonding, where dual resonators were embedded in the pressure-sensitive diaphragm to sense differential pressures, and a silicon cap was used to form a vacuum cavity. Differential pressures applied to the developed microsensor caused deflections of the pressure-sensitive diaphragm, resulting in shifts in resonant frequencies. This microsensor was designed based on finite element simulations with optimized structural parameters, which indicated high differential pressure sensitivities. Micro fabrications with key processes of deep reactive-ion etching (DRIE), lithography, and wafer-level eutectic bonding were adopted for device fabrication. The following experimental characterizations were conducted, producing the differential-pressure sensitivity of 181.53 Hz/kPa, the maxing fitting error of less than 80 Pa, under the differential pressure range of 0–100 kPa, the static pressure range of 110–200 kPa, and the temperature range of −10 °C to 60 °C. These results show that developed resonant differential pressure microsensors have excellent performances for differential-pressure measurements.

Resonant differential pressure (DP) sensors are prone to environmental disturbances [e.g., temperatures ( ${T}$ ) and static pressure (SP)] due to poor packaging. In order to address this issue, this article presents a resonant DP microsensor where the core pressure-sensitive element was assembled with the packaging house using stress isolation and Au–Au bonding. The stress isolation was used to reduce the effect of packaging house on the core-sensitive element when the environmental disturbances of temperature and SP varied, and the Au–Au bonding was used to improve the structural stability to reduce the frequency drift over time. Numerical simulation was conducted to confirm the positive effect of including the stress isolation structure and fabrication processes were developed to realize Au–Au bonding in packaging. Experimental characterization was conducted, reporting reductions of three times in temperature disturbance, 25 times in SP disturbance, and 35 times in frequency drift in comparison with the counterpart without stress isolation and Au–Au bonding. Based on these improvements, the accuracy of the developed resonant DP microsensor was quantified as 0.03%FS within the DP of 0–100 kPa, the temperature of −10 °C to 60 °C, and the SP of 110–200 kPa.