DESIGN AND FABRICATION OF SILICON CONDENSER MICROPHONE USING CORRUGATED DIAPHRAGM TECHNIQUE

A novel silicon condenser microphone with a corrugated diaphragm has b een proposed, designed, fabricated and tested. The microphone is fabri cated on a single wafer by use of silicon anisotropic etching and sacr ificial layer etching techniques, so that no bonding techniques are re quired. The introduction of well-performing corrugations has greatly i ncreased the mechanical sensitivities of the microphone diaphragms due to the reduction of the initial stress in the thin films. For the pur pose of further decreasing the thin film stress, composite diaphragms consisting of multilayer (polySi/SixNy/polySi) materials have been fab ricated, reducing the initial stress to a much lower level of about 70 MPa in tension. Three types of corrugation placements and several cor rugation depths in a diaphragm area of 1 mm(2) have been designed and fabricated. Microphones with flat frequency response between 100 Hz an d 8 similar to 16 kHz and open-circuit sensitivities as high as 8.1 si milar to 14.2 mV/Pa under the bias voltages of 10 similar to 25 V have been fabricated in a reproducible way. The experimental results prove d that the corrugation technique is promising for silicon condenser mi crophone.