INORGANIC ELECTRET MEMBRANE FOR A SILICON MICROPHONE

A new inorganic electret material is presented for application in micr omachined sensors, wherever a static electric field is needed to repla ce an external voltage supply, e.g., for airborne sound transducers. T he double-layer system of thermal silicon dioxide/CVD nitride is an ex cellent candidate for a silicon-based electret material. An inorganic electret membrane of this material is suggested for application in a s ilicon microphone. The processing of the electret membrane chip is des cribed and results of stress-compensated electret layers with good cha rge stability are presented.