Design And Optimization Of The Pressure Sensor

Pressure sensors are widely used in industrial control, medical test, environmental monitoring, and aerospace applications, etc. The piezoresistive pressure sensor dominates the mainstream market of MEMS pressure sensors due to its simple manufacturing process, good linearity, output the voltage signal directly, and simplify the sensors' interface issues, and so on. Before the pressure sensors are applied into industrial practice, it must be go through a series of links to research and optimize the performance of the sensors, such as test and calibration.The traditional method to calibrate and test the pressure sensor is to put the pressure sensors in the pressure tank, by setting the different pressure and temperature values in the pressure tank to simulate the real working environment of the pressure sensor.In this paper, electrostatic force was designed to apply to detect the pressure sensors, which has solved the issue of low efficiency and time-consuming drawbacks of the traditional method. Experimental results showed that the piezoresistive pressure sensor had good linearity, good repeatability and low hysteresis characteristics. The sensitivity was 1.77mV/hPa and the non-linearity was 1.19% respectively. At the same time, the electrostatic force could replace the loaded pressure in the range between 110hPa and 500hPa.The main work is as follows:First of all, theoretical model of the composite membrane piezoresistive sensor was established, the analytical model of the electrostatic force driven by an electrostatic voltage was obtained, and the optimization of the structure has been given by analyzing of the model.Secondly, ANSYS finite element simulation software was used to simulate the structure of piezoresistive pressure sensor, including simulating the deflection and stress distribution of the composite elastic membrane under the loaded pressure. At the same time, composite elastic membrane's deflection and stress distribution under the electrostatic force were also simulated which could verify the analytical model.Thirdly, a feasible fabrication process based on flip-chip process was proposed based on the MEMS processing, and the pressure sensor and its detection structure were manufactured in Suzhou Institute of Nano-Tech and Nano-Bionics.Finally, the pressure sensors' performance was tested by use of the traditional method and electrostatic force structure. Experimental results showed that the electrostatic force could replace pressure in the range between 110hPa and 500hPa, reduces test time and increase stability greatly. The sensitivity was 1.77mV/hPa and the non-linearity was 1.19% respectively.