A REVIEW OF SILICON MICROPHONES

Silicon micromachining has successfully been applied to fabricate piez oelectric, piezoresistive and capacitive microphones. The use of silic on has allowed the fabrication of microphones with integrated electron ic circuitry and the development of the new FET microphone. The introd uction of lithographic techniques has resulted in microphones with ver y small (1 mm2) diaphragms and with specially shaped backplates. The a pplication of corrugated diaphragms seems a promising future developme nt for silicon microphones. It is concluded from a noise consideration that the FET microphone shows a high noise level, which is mainly due to the small sensor capacitance. From this noise consideration, it ca n be shown that integration of a capacitive microphone and a preamplif ier will result in a further reduction of the noise.