Miniaturized inorganic electret layers

Silicon dioxide and nitride based materials are interesting inorganic electrets for applications in the field of micromechanics and sensor technologies since they are compatible to the silicon technology. It was the motivation for this work to find new suitable electret materials with good mechanical properties for the application in a micromachined electret condenser microphone. SiO/sub 2/, Si/sub 3/N/sub 4/ single and double layers and SiON layers are investigated in terms of chargeability and long-term charge-stability. The main emphasis is put on the miniaturization of electret layers. The lateral dimensions of the electrets are reduced down to 2 mm and the characteristics under different environmental conditions are described.