A silicon directly bonded capacitive absolute pressure sensor

A silicon directly bonded capacitive absolute pressure sensor is presented in this paper. The sensor consists of a vacuum-sealed cavity and a parallel plate capacitance microstructure fabricated by silicon direct bonding. The flexible single crystal silicon diaphragm whose thickness can be well controlled was completed by two steps of silicon direct bonding, and the sealed cavity was formed at the same time. Lead-transfer was realized by the thermo-compression bonding. The performance of the sensor was simulated by ANSYS software. The experimental results were compared with the theoretical values. It shows that the sensor provides a dynamic range of 1040-520 mbar, has a sensitivity of 1.58 fF/mbar. The nonlinearity of the full range (FSO) is less than 6.47%, while the nonlinearity in 520-680 mbar, 680-840 mbar and 840-1040 mbar is less than 0.68%, 2.03% and 1.28%, respectively. The maximum hysteresis error occurs in the range of 680-840 mbar, the error over the capacitance change of the full range is about 2.43%, and the sensor has a TCO of 181.5 ppm/°C.