In this paper, a piezoresistive pressure sensor based on silicon on insulator (SOI) was presented, which was composed of an SOI layer with sensing elements and a glass cap for a hermetic package. Different from its conventional counterparts, the position and thickness of the four piezoresistors was optimized based on numerical simulation, which suggests that two piezoresistors at the center while the other two at the edge of the pressure-sensitive diaphragm and a thickness of 2 μm can produce the maximum sensitivity and the minimum nonlinearity. Due to the use of silicon rather than metal for electrical connections, the piezoresistive pressure sensor was fabricated in a highly simplified process. From the experimental results, the fabricated piezoresistive pressure sensor demonstrated a high sensitivity of 37.79 mV·V⁻¹·MPa⁻¹, a high full-scale (FS) output of 472.33 mV, a low hysteresis of 0.09% FS, a good repeatability of 0.03% FS and a good accuracy of 0.06% FS at 20 °C. A temperature coefficient of sensitivity of 0.44 mV·MPa⁻¹·°C⁻¹ and a low zero drift were also shown at different temperatures. The piezoresistive pressure sensor developed in this study may function as an enabling tool in pressure measurements.

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 article presents a new micromachined resonant differential pressure sensor, which is mainly composed of an SOI wafer as the sensing element and a glass-on-silicon (GOS) cap for vacuum packaging. More specifically, two resonators were deployed on the central and side areas of the pressure-sensitive diaphragm in the SOI handle layer and coupled to the pressure-sensitive diaphragm in the GOS glass layer, enabling differential outputs. The proposed differential pressure sensor was fabricated based on conventional microfabrication processes (e.g., photolithography, deep reactive ion etching, and anodic boning) and characterized in both open- and closed-loop manners, producing quality factors of the resonators higher than 18 000. Furthermore, averaged differential pressure sensitivities were quantified as -4.4664 Hz/kPa (~64 ppm/kPa) with a linear correlation coefficient of 0.9992 (a static pressure of 110 kPa and a temperature from -30 °C to 80 °C) and -4.4516 Hz/kPa (~64 ppm/kPa) with a linear correlation coefficient of 0.9992 (static pressure from 110 to 310 kPa and temperature of 25 °C). In addition, averaged temperature sensitivities and averaged static pressure sensitivities were quantified as -1.2932 Hz/°C (~18 ppm/°C) and 0.0989 Hz/kPa (~1 ppm/kPa), which further validated the proposed differential pressure sensor.

This paper presents a resonant pressure microsensor with the measurement range of 1 MPa suitable for the soaring demands of industrial gas pressure calibration equipment. The proposed microsensor consists of an SOI layer as a sensing element and a glass cap for vacuum packaging. The sensing elements include a pressure-sensitive diaphragm and two resonators embedded in the diaphragm by anchor structures. The resonators are excited by a convenient Lorentz force and detected by electromagnetic induction, which can maintain high signal outputs. In operation, the pressure under measurement bends the pressure-sensitive diaphragm of the microsensor, producing frequency shifts of the two underlining resonators. The microsensor structures were designed and optimized using finite element analyses and a 4” SOI wafer was employed in fabrications, which requires only one photolithographic step. Experimental results indicate that the Q-factors of the resonators are higher than 25,000 with a differential temperature sensitivity of 0.22 Hz/°C, pressure sensitivities of 6.6 Hz/kPa, and −6.5 Hz/kPa, which match the simulation results of differential temperature sensitivity of 0.2 Hz/°C and pressure sensitivities of ±6.5 Hz/kPa. In addition, characterizations based on a closed-loop manner indicate that the presented sensor demonstrates low fitting errors within 0.01% FS, high accuracy of 0.01% FS in the pressure range of 20 kPa to 1 MPa and temperature range of −55 to 85 °C, and the long-term stability within 0.01% FS in a 156-day period under the room temperature.

This paper presents a high-sensitivity micromachined resonant differential pressure sensor based on bulk silicon. The sensor includes a sensing unit made of a SOI wafer, which is vacuum packaged by a glass-on-silicon (GOS) wafer. More specifically, two resonators located in the SOI device layer were coupled to the GOS glass layer and deployed on the central and side areas of the pressure-sensitive diaphragm respectively, enabling differential outputs. According to the relevant theory of elasticity, the differential pressure sensitivity is high, where the conversion efficiency of the differential pressure to resonators stress is improved by the special cap design, large pressure-sensitive diaphragm and narrow resonators. The developed differential pressure microsensors were manufactured leveraging well-established microfabrication steps including lithography, etching and boning. Characterization of the micromachined sensors was conducted, reporting averaged differential pressure sensitivities of 1) -143.17 Hz/kPa (~2051 ppm/kPa) and a linear correlation coefficient of 0.999992 under a static pressure of 110 kPa and a temperature range from -°C to 40°C; 2) -143.36 Hz/kPa (~2051 ppm/kPa) and a linear correlation coefficient of 0.999997 under a static pressure range from 110 kPa to 250 kPa and a temperature of 25°C. Compared to previous study, the high differential pressure sensitivity of the sensor can pave ways for the subsequent high-precision measurement of differential pressures, which can be used to measure micro differential pressure in the field of nuclear power.

This paper presents a resonant pressure microsensor relying on electrostatic excitation and piezoresistive detection where two double-ended tuning forks were used as resonators, enabling differential outputs. Pressure under measurement caused the deformation of the pressure sensitive membrane, leading to stress buildup of the resonator under electrostatic excitation with a corresponding shift of the resonant frequency detected piezoresistively. The proposed microsensor was fabricated by simplified SOI-MEMS technologies and characterized by both open-loop and closed-loop circuits, producing a quality factor higher than 10,000, a sensitivity of 79.44 Hz/kPa and an accuracy rate of over 0.01% F.S. In comparison to the previously reported resonant piezoresistive sensors, the proposed device used single-crystal silicon as piezoresistors, which was featured with low DC biased voltages, simple sensing structures and fabrication steps. In addition, the two double-ended tuning forks were used as resonators, producing high quality factors and differential outputs, which further improved the sensor performances.