Inorganic electret membrane for a silicon microphone

Abstract

A new inorganic electret material is presented for application in micromachined sensors, wherever a static electric field is needed to replace an external voltage supply, e.g., for airborne sound transducers. The double-layer system of thermal silicon dioxide/CVD nitride is an excellent candidate for a silicon-based electret material. An inorganic electret membrane of this material is suggested for application in a silicon microphone. The processing of the electret membrane chip is described and results of stress-compensated electret layers with good charge stability are presented.