Optimized technology for the fabrication of piezoresistive pressure sensors

In this work a technology for the fabrication of piezoresistive pressure sensors is presented, based on the use of silicon BESOI (bonded and etch-back silicon on insulator) wafers. The main purpose of the proposed technology is the optimization of the thin silicon diaphragm definition process that is one of the most critical steps in the fabrication of silicon pressure sensors. The buried silicon oxide laver of the BESOI wafers is used as an automatic etch stop of the silicon anisotropic etching, making it possible to obtain very precise control of the sensor diaphragm thickness. In addition, the type and thickness of the layers acting as masking materials on the backside of the wafers have been optimized in order to get a high-yield process. The experimental results obtained when using the proposed technology are presented and discussed.