Design, analysis and optimization of a novel capacitive pressure sensor based on vertical comb-grid configuration

This paper presents a novel structure for absolute capacitive pressure sensor which utilizes vertically arranged comb fingers to reach high sensitivity with wide dynamic range. High sensitivity is one of the important factors in pressure sensors, which usually is achieved by decreasing air-gap within sensing electrodes and thin membrane in capacitive types, but in this paper a comb-grid structure is employed instead to improve the sensitivity. Due to the out-of-plane configuration of comb-fingers, capacitance variation is affected by both changing in lateral overlapped area and also distance within the electrodes simultaneously, which provides two extra degrees of freedom in manipulation and optimization of the sensor behavior in comparison with conventional capacitive pressure sensors. Design optimizations and analysis are derived by energy method which is in fine agreement with Finite Element Analysis (FEA) performed by ANSYS. Variation in sensing electrode area is also carried out to optimize the sensitivity. The results show a sensitivity of 66 fF/kPa at area ratio of 10% and membrane size of 1 × 1 mm². Full scale pressure range of 160 kPa at area ratio of 70% and membrane size of 500 μm × 500 μm is achieved. We found that, higher sensitivities are achieved by horizontally decrement in air gap.