Development of an electret microphone in silicon


Sprenkels, A.J. and Groothengel, R.A. and Verloop, A.J. and Bergveld, P. (1989) Development of an electret microphone in silicon. Sensors and Actuators, 17 (3-4). pp. 509-512. ISSN 0250-6874

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Abstract:We describe a subminiature electret microphone, which has been realized in silicon using wafer processing techniques. The microphone consists of a rigid backplate fabricated in silicon and a 2.5 μm thick metallized Mylar foil (PETP) acting as the diaphragm. Between the diaphragm and the backplate a 20 μm thick air cavity and a 1.1 μm thick charged SiO2 layer are present. The SiO2 layer is used as the electret and generates an electric field in the air gap. The electret has been changed to 300 V using a corona-charging set-up. The time constant of the charge decay amounts to more than 100 years at ambient laboratory conditions.

The microphone cartridge, which measures 3 × 3 × 0.3 mm, shows an open-circuit sensitivity of about 2.5 mV/μbar at 1 kHz.
Item Type:Article
Copyright:© 1989 Elsevier Science
Electrical Engineering, Mathematics and Computer Science (EEMCS)
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