A Novel Packaging Structure and Process for High Temperature Silicon Piezoresistive Pressure Sensor.

The performance of the usual diffused silicon piezoresistive pressure sensors for pressure measurement in high temperature environments is affected by the failure of PN junction isolation, the expansion of silicon oil in packaging structure, and other factors. This study proposed an all-solid-state packaging structure based on silicon/glass/kovar alloy bonding to modify the poor temperature tolerance of silicon oil in the conventional packaging structure of high temperature silicon piezoresistive pressure sensors. Micro-electromechanical system processes, including etching, oxidation, and sputtering, were applied to prepare a high-temperature pressure-sensitive chip based on the smart-cut silicon on insulator wafer. The interconnection of piezoresistors was realized with Ti/Pt/Au multilayer metallization composite electrodes. Silicon/glass, glass/kovar alloy pressure pipes were sealed through the electrostatic bonding process. The electron beam welding process was used to realize the solid-state connection between pressure pipes and sockets, and the sealing condition and performance of the sensor were verified by scanning electron microscope and experiments. Results show that the bonding interfaces between silicon wafer/glass/pressure pipes are good, when a pressure from 0 to 6.0 MPa is applied from 0 °C to 300 °C, the sensitivity is approximately 200 mV/MPa, the nonlinearity is less than 0.59‰FS, the repeatability is less than 0.04‰FS at 300 °C, and the sensitivity temperature drift is less than -0.133 mV/(MPa·°C). This study provides a certain reference for the pressure measurement of silicon piezoresistive pressure sensors in harsh high-temperature environments. [ABSTRACT FROM AUTHOR]