High Temperature Piezoresistive Pressure Microsensor Based on the MEMS Technology

摘要

A high temperature lower range piezoresistive pressure microsensor based on the MEMS (Micro Electro-Mechanical System) and SIMOX (Separation by Implantation of Oxygen) technology has been developed for the harsh environment application. This piezoresistive pressure microsensor's sensitive chip is constituted by silicon substrate, a thin silicon dioxide layer by SIMOX, four Wheatstone bridge p-type resistances in the measuring circuit layer by boron ion implantation and photolithography, stress matching layer with silicon nitride, and beam lead layer (Ti-Pt-Au) for connecting p-type resistance by sputtering, and a cavity like cup structure fabricated by the wet etching. A special silicon dioxide layer is fabricated by the SIMOX technology in the sensitive element, which solves the problem of the leak-current influence, so the pressure microsensor fabricated by high temperature packaging process can be used in the fields with high temperature up to 200°C. In contrast, the traditional solid-state piezoresistive pressure chip is not able to used in high temperature fields, because the leak-current through the p-n junction which is used to isolate the upper measuring circuit layer from the silicon substrate, will increases at the temperature above 120°C, so the sensor's performance will be deteriorated under high temperature. Otherwise, some compensation methods have been studied, the thermal zero drift k_0 and the thermal sensitivity k_S of the pressure microsensor are easy to be less than 2 x 10~(-4) FS/°C. In addition, this type pressure microsensor's range is up to 1MPa. The experimental results show that this pressure microsensor has good performances in the high temperature and is able to meet the requirements of the modern industry, such as aviation, wind tunnel, automobile industry, engine, etc.