30 December 2008 Effective diaphragm area of spring-supported capacitive MEMS microphone designs
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Capacitive (condenser) MEMS microphones have been developed using various design and fabrication techniques to improve performance. Mechanical sensitivity of a condenser MEMS microphone can be increased by reducing the residual stress of the diaphragm using several design approaches including corrugated diaphragms, and in recent years, various spring type diaphragms. The electrical sensitivity of the condenser microphone is proportional to the deflection of the diaphragm, however, the parabolic deflection of the diaphragm, and thus its effective diaphragm area, has reduced the sensitivity of parallel plate type capacitor on a condenser MEMS microphone. This paper presents the numerical analysis on the effective diaphragm area of several condenser MEMS microphone designs of 1.1mm x 1.1mm square. The analysis shows that the effective area of a spring-supported diaphragm is about 20% higher, and its capacitance value thus electrical sensitivity, is about 170% higher than a fully clamped flat diaphragm of an equal size. In addition, a flat deflection and higher effective diaphragm area of a spring-supported diaphragm can be achieved by carefully designed spring mechanisms.
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Norizan Mohamad, Norizan Mohamad, Pio Iovenitti, Pio Iovenitti, Thurai Vinay, Thurai Vinay, } "Effective diaphragm area of spring-supported capacitive MEMS microphone designs", Proc. SPIE 7268, Smart Structures, Devices, and Systems IV, 726805 (30 December 2008); doi: 10.1117/12.810575; https://doi.org/10.1117/12.810575

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