PECVD SiO2/Si3N4 Double-layer Electrets for Application in Micro-devices

Abstract

Abstract In this paper, the influence of different environmental conditions, substrates, micromachining processes, areas and patternings on the performances of PECVD SiO2/Si3N4 double-layer electrets were studied for its application in micro-devices. Various samples were prepared and then charged by the negatively corona charging method. The charge decays at either 250°C or 95%RH were observed to reveal the chargeability and charge stability. Finally, a micro power generator with patterned PECVD SiO2/Si3N4 double-layer electret was presented briefly as demonstration. The results show that all these conditions that conventionally or even unavoidably happen in the fabrication process of electret micro-devices had more or less impact on the electret performance. It is crucial that the electret should be as large area as possible and kept from the micromachining processes and humid condition to the best. Our micro power generator with 2mm rectangular array of PECVD SiO2/Si3N4 double-layer electret had the 5μW output power at 20Hz and 0.7g.