Abstract
The study investigates a capacitive micro pressure sensor integrated with a ring oscillator circuit on a chip. The integrated capacitive pressure sensor is fabricated using the commercial CMOS (complementary metal oxide semiconductor) process and a post-process. The ring oscillator is employed to convert the capacitance of the pressure sensor into the frequency output. The pressure sensor consists of 16 sensing cells in parallel. Each sensing cell contains a top electrode and a lower electrode, and the top electrode is a sandwich membrane. The pressure sensor needs a post-CMOS process to release the membranes after completion of the CMOS process. The post-process uses etchants to etch the sacrificial layers, and to release the membranes. The advantages of the post-process include easy execution and low cost. Experimental results reveal that the pressure sensor has a high sensitivity of 7 Hz/Pa in the pressure range of 0–300 kPa.
Highlights
Microelectromechanical system (MEMS) technology has become popular for the miniaturization of sensors
Sippola and Ann [2] presented a ceramic capacitive pressure sensor fabricated by using thick film screen-printing technique, which the sensor consisted of a bottom electrode deposited on an alumina substrate and a top electrode deposited on a ceramic diaphragm
A pressure chamber, a power supply and a spectrum analyzer were adopted to measure the characteristic of the capacitive pressure sensor with ring oscillator circuit
Summary
Microelectromechanical system (MEMS) technology has become popular for the miniaturization of sensors. Many micro capacitive pressure sensors have recently been manufactured by using MEMS technology. Habibi et al [1] utilized a surface micromachining process to fabricate a capacitive pressure sensor array on a glass substrate. The array consisted of electrically parallel individual sensors with composite SiO2-Cr-SiO2 diaphragms and vacuum-sealed cavities underneath, and the cavities were formed by etching an aluminum sacrificial layer. Sippola and Ann [2] presented a ceramic capacitive pressure sensor fabricated by using thick film screen-printing technique, which the sensor consisted of a bottom electrode deposited on an alumina substrate and a top electrode deposited on a ceramic diaphragm. The cavity and diaphragm were created using a thick film sacrificial layer, and the pressure sensor had a sensitivity of 9.2 fF/psi
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