A capacitive pressure sensor for sensing circuits with GaN diode bridge

This work reports the design, fabrication process and characterization of a silicon diaphragm capacitive pressure sensor high temperature applications using low-temperature co-fired ceramic substrate. The pressure reference cavity placed inside the senor is hermetically sealed in vacuum especially for high temperature applications to avoid a change of the reference pressure. Capacitance sensing circuits associated with an Impedance Bridge is implemented in order to monitor the change the capacitor with respect to that of the potential. GaN diodes are integrated in capacitance sensing circuits to form low-pass filtering and amplifying devices. The capacitor associated in a resonant circuit determines the frequency of oscillation, hence an FM signal proportional to pressure can be obtained. The measured spectral property of the capacitor voltage waveform indicates the expected operation of the capacitive pressure sensors. The advantage of the integration of the GaN diode offers wide band gap; non-intrinsic at much higher temperature or less demand on cooling, high breakdown field, good electron mobility and thermal conductivity as well as high mechanical and thermal stability.