Design and fabrication of silicon condenser microphone using corrugated diaphragm technique

Abstract

A novel silicon condenser microphone with a corrugated diaphragm has been proposed, designed, fabricated and tested. The microphone is fabricated on a single wafer by use of silicon anisotropic etching and sacrificial layer etching techniques, so that no bonding techniques are required. The introduction of corrugations has greatly increased the mechanical sensitivities of the microphone diaphragms due to the reduction of the initial stress in the thin films, For the purpose of further decreasing the thin film stress, composite diaphragms consisting of multilayer (polySi/Si/sub x/N/sub y//polySi) materials have been fabricated, reducing the initial stress to a much lower level of about 70 MPa in tension. Three types of corrugation placements and several corrugation depths in a diaphragm area of 1 mm/sup 2/ have been designed and fabricated. Microphones with flat frequency response between 100 Hz and 8/spl sim/16 kHz and open-circuit sensitivities as high as 8.1/spl sim/14.2 mV/Pa under the bias voltages of 10/spl sim/25 V have been fabricated in a reproducible way. The experimental results proved that the corrugation technique is promising for silicon condenser microphone.