Fabrication of silicon piezoresistive pressure sensor using a reliable wet etching process

Silicon-based piezoresistive pressure sensors are generally fabricated as a piezo-sensitive diaphragm by using MEMS technology and SOI wafer. Lots of innovations and improvements have been made for silicon pressure sensor to increase its performance and reliability. It is found that the quality of Si-Si bonding will directly affect the performing of SOI substrate removing processes. The main problem is that the etching liquid infiltrate into bonding interface from the defect position of bonding wafer edge, resulting in the damage and corrosion of bonding wafer. To solve this problem, the paper presents an etching fixture design for effectively protecting the bonding wafer edge. Experimentally, a SOI-Si bonding wafer with poor quality in bonding edge was used to fabricate the piezoresistive pressure sensors by using the etching fixture. The experimental results show the use of etching fixture did not damage the bonding wafer and made a nice removal of SOI substrate. The fabricated pressure sensors wafers are also presented.