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Journal of Micro/Nanolithography, MEMS, and MOEMS • new

Design, modeling, and fabrication of crab-shape capacitive microphone using silicon-on-isolator wafer
Author(s): Bahram Azizollah Ganji; Sedighe Babaei Sedaghat; Alberto Roncaglia; Luca Belsito; Reza Ansari
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Paper Abstract

This paper presents design, modeling, and fabrication of a crab-shape microphone using silicon-on-isolator (SOI) wafer. SOI wafer is used to prevent the additional deposition of sacrificial and diaphragm layers. The holes have been made on diaphragm to prevent back plate etching. Dry etching is used for removing the sacrificial layer, because wet etching causes adhesion between the diaphragm and the back plate. Crab legs around the perforated diaphragm allow for improving the microphone performance and reducing the mechanical stiffness and air damping of the microphone. In this structure, the supply voltage is decreased due to the uniform deflection of the diaphragm due to the designed low-K (spring constant) structure. An analytical model of the structure for description of microphone behavior is presented. The proposed method for estimating the basic parameters of the microphone is based on the calculation of the spring constant using the energy method. The microphone is fabricated using only one mask to pattern the crab-shape diaphragm, resulting in a low-cost and easy fabrication process. The diaphragm size is 0.3  mm×0.3  mm, which is smaller than the conventional microelectromechanical systems capacitive microphone. The results show that the analytical equations have a good agreement with measurement results. The device has the pull-in voltage of 14.3 V, a resonant frequency of 90 kHz, an open-circuit sensitivity of 1.33  mV/Pa under bias voltage of 5 V. Comparing with previous works, this microphone has several advantages: SOI wafer decreases the fabrication process steps, the microphone is smaller than the previous works, and crab-shape diaphragm improves the microphone performances.

Paper Details

Date Published: 12 February 2018
PDF: 9 pages
J. Micro/Nanolith. MEMS MOEMS 17(1) 015002 doi: 10.1117/1.JMM.17.1.015002
Published in: Journal of Micro/Nanolithography, MEMS, and MOEMS Volume 17, Issue 1
Show Author Affiliations
Bahram Azizollah Ganji, Babol Noshirvani Univ. of Technology (Iran)
Sedighe Babaei Sedaghat, Babol Noshirvani Univ. of Technology (Iran)
Alberto Roncaglia, Istituto per la Microelettronica e Microsistemi (Italy)
Luca Belsito, Istituto per la Microelettronica e Microsistemi (Italy)
Reza Ansari, The Univ. of Guilan (Iran)

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