A High Temperature Force Sensor with Low Temperature Drift Operated At 500 °C

This paper demonstrates a shielded capacitive force and pressure sensor that can operate at 500 °C. The measurements show a high accuracy of the sensor with an excellent thermal stability of only −0.0027 %/K full scale (FS) and a nonlinearity error of the inverse capacitance of 0.035 %FS at 500 °C without any additional compensation. A significantly high temperature and mechanical stability was realized by a novel process using Aluminum-Silicon (Al-Si) eutectic bonding. This has the advantage of increasing the operating temperature up to 500 °C without appreciable loss of accuracy and sensitivity compared to standard Gold-Silicon eutectic bond [1]. A Si-Al/Al-Si stack has been investigated and we reveal that the eutectic temperature of 577 °C specified in the Al-Si phase diagram is not sufficient. The best results were obtained at 650 °C and beyond under vacuum condition.