Abstract
A semiconductor microphone structure is described in terms of the optimization of its micromachining parameters. Microscaling of dimensions is subject to a minimum signal‐to‐electrical noise ratio requirement, with an objective of small silicon diaphragm area. Side constraints include electrostatic stability, acceptable frequency response, and low‐condenser bias voltage. Relations on electrostatic biasing and acoustic sensitivity are presented. A lumped parameter model of the silicon diaphragm was justified for the equivalent circuit. An electrical noise model is described. Scaling to a submicron air film thickness was required to meet the above criteria. A novel (patented) acoustic hole array through the backplate overcomes the resulting (excessive) air squeeze‐film damping (i.e., resistance). The array of 2000 holes, nevertheless, consumes a small fraction of the capacitive area. Analyses for mechanical vibration pickup sensitivity and perforated backplate mechanical stability are briefly discussed.
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