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" Development of a Pull-In Free Electrostatic MEMS Microphone "
Ozdogan, Mehmet
Towfighian, Shahrzad
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Latin Dissertation
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| Language of Document
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English
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| Record Number
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1107255
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| Doc. No
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TLpq2437830916
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| Main Entry
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Ozdogan, Mehmet
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Towfighian, Shahrzad
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| Title & Author
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Development of a Pull-In Free Electrostatic MEMS Microphone\ Ozdogan, MehmetTowfighian, Shahrzad
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| College
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State University of New York at Binghamton
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| Date
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2020
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2020
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| Degree
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Ph.D.
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| Page No
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135
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| Abstract
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Today, sensors are everywhere with recent developments in technology, such as artificial intelligence and internet-of-things (IoT). Miniature microphones are one of the most commonly used sensors that have been integrated into billions of devices such as laptops, hearing aids, virtual reality headsets, smart speakers, and headphones. However, the sensitivity of the conventional electrostatic microphones has almost reached its theoretical limits. One approach for better-performing microphones is to increase the bias and reduce the noise, which eventually results in devices with a higher signal-to-noise ratio. However, with the current technology, one cannot increase the bias voltage at will due to the pull-in instability, which has a great potential to cause permanent damage to the released micro-structures. In this study, we propose an electrostatic micro-electro-mechanical-systems (MEMS) microphone with a radical change to the electrode configuration. This particular electrode scheme, which is called levitation based electrode design, enables capacitive MEMS sensors to work for large bias voltages without failing due to pull-in. The study presents the design, fabrication, and characterization of the microphone, which is made of approximately 2 μm thick highly-doped polysilicon diaphragm with a 1 mm2 surface area. The diaphragm is incorporated with finger-like electrodes on three sides of it. Right underneath these moving electrodes, there are 2 μm thick fixed electrodes with a 2 μm thick air gap. After the fabrication process, the mechanical and electrical responses of the microphones are measured in an acoustic chamber. The experimental results indicate that the microphone worked for a wide range of bias voltages (27-200 Volts) without any pull-in failure. They also reveal that the acoustic sensitivity increased up to a specific bias voltage, which suggests that there is an optimum bias to achieve the highest possible acoustic sensitivity. For some of the microphones, it was measured to be 16.1 mV/Pa at 200 V bias voltage, and the bandwidth was from 100 Hz to 4.9 kHz. Overall, the experimental results and simulations prove that integrating the levitation based electrode scheme to a MEMS sensor could yield high sensitivity devices that can handle high DC voltages, which is not feasible for most of the electrostatic microphones.
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Acoustics
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Engineering
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Mechanical engineering
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