MEMS piezoresistive sound detectors have been fabricated using the dissolved wafer process for the first time. The sensors utilize stress compensated PECVD ultra-thin silicon-nitride/oxide membrane together with monocrystalline ion-implanted p ++ silicon piezoresistors to achieve high sensitivity. Tests reveal that sensors with a diaphragm size of 710 µm have a static sensitivity of 1.1 µV VPa −1 with 2% non-linearity over an operating pressure range of 10 kPa. This sensitivity is substantially larger than that of commercially available microfabricated sensors. Furthermore, the new sensor's dynamic response is found to be flat (within ±2.5 dB) over a frequency range extending up to 10 kHz. This paper contributes to existing literature in the field by demonstrating a new way of fabricating capable MEMS piezoresistive pressure sensors, hence adding to the overall versatility of the technology and associated range of applications.
A new MEMS piezoresistive acoustic/pressure sensor has been developed for use to measure jet screech noise. A few samples of the new sensor with different sizes and 2. from different chips were calibrated in the sound field of an air siren. The results show that the new sensor has a flat response at least fi-om 1 kHz to 6 kHz and a 3. sensitivity that can be as high as four to five times that of the smallest-size silicon-based commercial sensors. However, these first generation devices lack the appropriate shielding and grounding and experience some variation in characteristics of different units with 4. the same nominal design parameters. Those drawbacks possible measurements where the spatial and temporal resolution requirements are highly demanding. The ability to manufacture MEMS sensors or acuators, in large arrays; thus providing the potential for distributed control and diagnostics. The compatibility with some of the manufacturing processes of Integrated Circuits. Therefore, complete (sesnor/actuator/controller) autonomous systems are realizable with MEMS.
A MEMS piezoresistive acoustic sensor has been developed for measurement of jet screech noise. The new sensor was calibrated in the sound field of an air siren. Two sensors with a size of 510 and 710 pm were tested and compared to commercial sensors. The results show that the MEMS sensors are five to eight times more sensitive than the smallest commercially available piezoresistive sensors. Furthermore, the sensors are stable as demonstrated by the agreement between calibrations conducted over two months period. However, the bandwidth of this first generation sensors is somewhat limited by the damping of the diaphragm motion. This effect will be remedied in the next generation sensors through careful minimization of damping effects and increase of the sensors natural fi'eqUi3llCy.
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