Simulation of high sensitivity MEMS capacitive pressure sensor with small size and clamped square diaphragm
In this paper a novel MEMS capacitive pressure sensor with small size and high sensitivity is presented. This sensor has the separated clamped square diaphragm and movable plate. The diaphragm material is polysilicon. The movable and fixed plates are gold and the substrate is pyrex glass. The mechanical coupling is Si3N4. In capacitive sensor the sensitivity is proportional to deflection and capacitance changes with pressure for this reason with this design is improved the sensitivity with small size. The size of this sensor is 350×350 (µm2) and the thickness of diaphragm is 2µm with 1 air gap. This structure is designed by intellisuite software. In this simulation are shown the compare of polysilicon and polyimide diaphragms. Because in many previous works polysilicon and polyimide are used. In this MEMS capacitive pressure sensor the sensor sensitivity, diaphragm mechanical sensitivity for polysilicon(stress=100Mpa) diaphragm are 0.0074 (Pf/mmHg), 0.0042/mmHg), respectively and for polysilicon(stress=20Mpa) diaphragm are 0.0469(Pf/mmHg), 0.011/mmHg, respectively and polyimide diaphragm are 0.0226(pF/mmHg), 0.0091/mmHg), respectively. According to the simulating results for low pressure, the structure with polysilicon diaphragm has more change of the displacement and capacitance, this lead to high sensitivity than other diaphragms.