Liquid-free, piezoresistive, SOI-based pressure sensor for high temperature measurements up to 400 °C

In this paper a novel liquid-free, piezoresistive pressure sensor on SOI-basis (Silicon On Insulator) for high temperature applications is presented. The sensor is capable of measuring pressures at temperature up to 400 °C (constant load) with an accuracy of 0.25 % FSO (Full Scale Output). Media separation is realized using a steel membrane. A push rod (mounted onto the steel membrane) transfers the applied pressure directly to the centerboss membrane of the SOI-chip, which is placed on a ceramic carrier. The chip membrane is realized by DRIE (Deep Reactive Ion Etching or Bosch Process). Novel propertied chip housing employing a sliding sensor chip that is fixed during packaging by mechanical preloading via the push rod is used. Thereby, avoiding chip movement, optimal push rod load transmission is ensured. The housing consists of different sections optimized for compensation of CTE (Coefficient of Thermal Expansion) mismatches. Utilizing this novel packaging scheme and combining different housing materials, temperature, wear, and long term fatigue stability are assured.