Design and characterization of a high sensitive MEMS capacitive microphone using coupled membrane structure

Gharaei, Hassan; Koohsorkhi, Javad; Saniei, Foad; Abbasi, Ahmad

doi:10.1109/icrom.2013.6510136

Cited by 4 publications

(1 citation statement)

References 14 publications

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“…smart phones and tablets) and speech recognition systems [5]. Among different sensing mechanisms, capacitive sensors are the most common in MEMS microphones because of their high stability, sensitivity and signal to noise ratio [6][7][8][9][10][11]. A capacitive based microphone consists of two parallel electrodes (a diaphragm and a back plate) that produces output voltage from the movement of the electrically loaded diaphragm in response to sound pressure variation on its surface area.…”

Section: Introductionmentioning

confidence: 99%

A MEMS Microphone Using Repulsive Force Sensors

Ozdogan

Towfighian

2016

Volume 4: 21st Design for Manufacturing and the Life Cycle Conference; 10th International Conference on Micro- And Nanosystems

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We present a MEMS microphone that converts the mechanical motion of a diaphragm, generated by acoustic waves, to an electrical output voltage by capacitive fingers. The sensitivity of a microphone is one of the most important properties of its design. The sensitivity is proportional to the applied bias voltage. However, it is limited by the pull-in voltage, which causes the parallel plates to collapse and prevents the device from functioning properly. The presented MEMS microphone is biased by repulsive force instead of attractive force to avoid pull-in instability. A unit module of the repulsive force sensor consists of a grounded moving finger directly above a grounded fixed finger placed between two horizontally seperated voltage fixed fingers. The moving finger experiences an asymmetric electrostatic field that generates repulsive force that pushes it away from the substrate. Because of the repulsive nature of the force, the applied voltage can be increased for better sensitivity without the risk of pull-in failure. To date, the repulsive force has been used to engage a MEMS actuator such as a micro-mirror, but we now apply it for a capacitive sensor. Using the repulsive force can revolutionize capacitive sensors in many applications because they will achieve better sensitivity. Our simulations show that the repulsive force allows us to improve the sensitivity by increasing the bias voltage. The applied voltage and the back volume of a standard microphone have stiffening effects that significantly reduce its sensitivity. We find that proper design of the back volume and capacitive fingers yield promising results without pull-in instability.

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