Complementary metal-oxide-semiconductor microelectromechanical pressure sensor integrated with circuits on chip

This study investigates the fabrication of an integrated pressure sensor using the commercial 0.35 mu m complementary metaloxide-semiconductor (CMOS) process and a post-process. The main character of the pressure sensor is to integrate the circuits on a chip. The pressure sensor that is a capacitive type sensor is composed of 128 sensing cells in parallel, and each sensing cell contains a suspended membrane and a fixed electrode to form a parallel-plate sensing capacitor. The circuits are employed to convert the capacitance variation of the pressure sensor into the output voltage. The post-process uses etchants to etch the sacrificial layers to release the suspended membrane of the pressure sensor, and then low pressure chemical vapor deposition (LPCVD) parylene is utilized to seal the etching holes of the pressure sensor. Experimental results show that the pressure sensor has a sensitivity of 1.5 mV/(V.kPa) in the pressure range of 0-200 kPa.