Fabrication of silicon condenser microphones using single wafer technology

Abstract

A new condenser microphone design, which can be fabricated using the sacrificial layer technique, is proposed and tested. The microphone backplate is a 1 pm PECVD silicon nitride film with a high density of acoustic holes (120-525 holes/mm2), covered with a thin Ti/Au electrode. Microphones with a flat frequency response between 100 Hz and 14 kHz and a sensitivity of typically 1-2 mV/Pa have been fabricated in a reproducible way. These sensitivities can be achieved using a relatively low bias voltage of 6-16 V. The measured sensitivities and bandwidths are comparable to those of other silicon microphones with highly perforated backplates. The major advantage of the new microphone design is that it can be fabricated on a single wafer so that no bonding techniques are required.

Microfabrication of coupled fluid–structure systems with applications in acoustic sensing

“…However, single channel micromachined capacitively sensed microphones have been designed and constructed by a number of researchers [8][9][10][11]. The sensor that we have produced differs from the traditional design by sealing the backing cavity and filling it with a 0924-4247/$ -see front matter © 2007 Elsevier B.V. All rights reserved.…”

A GaAs acoustic sensor with frequency output based on resonant tunneling diodes

“…Although many different transduction principles have been employed [6], all are based on the detection of a pressureinduced structural deflection. In order to make a sensitive acoustic sensor, a deformable membrane is used to amplify the externally applied pressure.…”

Micromachined Arrayed Capacitive Ultrasonic Sensor/Transmitter with Parylene Diaphragms

“…In the case of a simple square diaphragm, the viscous damping coefficient is calculated analytically (Scheeper et al, 1992;Bergqvist & Gobet, 1994;Škvor, 1967) in relation to the number of acoustic holes and to the surface fraction occupied by the acoustic holes. However, there has been no research on air damping for an arbitrary diaphragm shape.…”

“…A capacitive sensor can also transmit ultrasound by applying impulsive high voltage as mentioned above: however, this B&K microphone is not applicable for the use of a transmitter because of the possibility of diaphragm fracture, taking into account its high cost. In contrast, several studies on a capacitive microphone with a silicon diaphragm (Scheeper et al, 1992;Bergqvist & Gobet, 1994;Ikeda et al, 1999;Chen et al, 2002;Martin et al, 2005;Khuri-Yakub et al, 2000;Zhuang et al, 2000) have been conducted using micromachining technology (Kovacs, 1998), and some of them have been commercialized (Knowles Acoustics, 2002). Using this technology, numerous arrayed miniaturized ultrasonic sensors with uniform performance can be fabricated on a silicon wafer with a fine resolution of several microns and a comparatively low cost, which may make it possible to fabricate an arrayed-type sensor (Yamashita et al, 2002a;Yamashita et al, 2002b;Guldiken & Degertekin, 2005;Khuri-Yakub et al, 2000;Zhuang et al, 2006) and to activate it as a transmitter or speaker (Diamond et al, 2002;Khuri-Yakub et al, 2000).…”