A High-Performance Capacitive Force Sensor for High-Temperature Applications

We present a high-range capacitive force sensor with exceptional thermal stability. Building on innovative manufacturing techniques from previous work, a new sensor design has been developed, fabricated, simulated and tested. The sensor, designed as a standard parallel plate capacitor, is assembled from two micro structured silicon chips using gold-silicon (Au-Si) eutectic bonding, which provides high mechanical and thermal stability and also forms a Faraday cage around the measurement electrodes. The force range has been drastically increased compared to earlier versions by the addition of a center post, while still providing a reasonably large base capacitance. Measurements conducted up to 350°C and 1500 N demonstrate the sensor's excellent thermal stability, with a temperature drift of less than −0.0008% /K without load (zero-point drift) and −0.0025% full scale (FS)/K under load at 350°C. The sensor achieved high linearity, with a value of 99.98% at room temperature and 99.3% at elevated temperatures up to 350°C. The sensitivity of the sensor is 3.66 fF/N.