Abstract
This paper presents the simulation, fabrication and characterization of a microFET (field effect transistor) pressure sensor with readout circuits. The pressure sensorincludes 16 sensing cells in parallel. Each sensing cell that is circular shape is composed ofan MOS (metal oxide semiconductor) and a suspended membrane, which the suspendedmembrane is the movable gate of the MOS. The CoventorWare is used to simulate thebehaviors of the pressure sensor, and the HSPICE is employed to evaluate the characteristicsof the circuits. The pressure sensor integrated with circuits is manufactured using thecommercial 0.35 μm CMOS (complementary metal oxide semiconductor) process and apost-process. In order to obtain the suspended membranes, the pressure sensor requires apost-CMOS process. The post-process adopts etchants to etch the sacrificial layers in thepressure sensors to release the suspended membranes, and then the etch holes in the pressuresensor are sealed by LPCVD (low pressure chemical vapor deposition) parylene. Thepressure sensor produces a change in current when applying a pressure to the sensing cells.The circuits are utilized to convert the current variation of the pressure sensor into thevoltage output. Experimental results show that the pressure sensor has a sensitivity of 0.032mV/kPa in the pressure range of 0-500 kPa.
Highlights
Micro pressure sensors that are important components can be applied in biomedical and various industries
[7] presented a capacitive pressure sensor fabricated by the CMOS process, in which the membranes were released using an anisotropic dry etching and a wet etching, and the etch holes were sealed by PECVD nitride
The FET pressure sensor was tested at different Vgs and Vds voltages without pressure in the pressure chamber
Summary
Micro pressure sensors that are important components can be applied in biomedical and various industries. A micro capacitive pressure sensor, presented by Eggers et al [1], was utilized in the biomedical measurement. [7] presented a capacitive pressure sensor fabricated by the CMOS process, in which the membranes were released using an anisotropic dry etching and a wet etching, and the etch holes were sealed by PECVD (plasma enhanced chemical vapor deposition) nitride. An FET pressure sensor, reported by Svensson et al [9], was fabricated by a surface micromachining process. Hynes et al [10] manufactured an FET pressure sensor using a surface micromachining process, in which a sacrificial oxide layer and a polysilicon diaphragm were deposited on the pressure sensing area, and HF was used to etch the sacrificial oxide from beneath the polysilicon diaphragm. The FET pressure sensor had a sensitivity of 1.3 μA/psi
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