High-performance ultra-small single crystalline silicon microphone of an integrated structure

We have succeeded in fabricating an ultra-small condenser microphone that has excellent acoustic characteristics, and excellent reliability and mass-producibility, with an integrated structure made from single-crystalline silicon, a material that has high tensile strength. This is owing to the use of a bonded wafer, which is prepared using powder silicon oxide as a glue (SODIC method), and precise control of the thickness of the diaphragm, a thin film that vibrates under acoustic pressure. The microphone's acoustic characteristics are: wide dynamic range with excellent linearity up to 10 Pa, wide frequency range of 75 Hz-24 kHz, and high sensitivity of - 47 dB (0 dB = 1 V/Pa). Since it is made of single-crystalline silicon, it is robust and thermally resistant. Moreover, it has suitability to mass production, because it is fabricated with a semiconductor process. (C) 2003 Elsevier Science B.V. All rights reserved.