Research For Capacitive Pressure Sensors Based On SON Structure

Capacitive pressure sensor,as the most common type of silicon micro-pressure sensor,has the advantages of high sensitivity,low energy consumption,small temperature drift and fast response speed,therefore,it has been widely used in the field of automobile industry,wearable equipment,environmental monitoring,industrial control,etc.For a capacitive absolute pressure sensor,the vacuum sealing cavity and extraction of the inner electrodes is a relatively complicated process.SON(Silicon on Nothing)technology can make monocrystalline silicon form a single crystal silicon film on the cavity during high temperature annealing.According to the characteristics of SON,the technology are used in the design and manufacture of capacitive pressure sensors in this dissertation.A capacitive absolute pressure sensor and a capacitive differential pressure sensor based on SON structure are designed,which can be applied to barometric measurement and small relative height detection respectively.The main research contents and achievements are as follows:(1)Research on capacitive absolute pressure sensor based on SON.First,a model of small deflection and large deflection of the sensor pressure film was established by plate and shell theory.Then,the load-deformation of the diaphragm was calculated by the theoretical model and ANSYS finite element simulation software.The result show the error between the two is less than 3%.Effects of the thickness of the sensing film,spacing between plates,the film radius and other parameters on output capacitance,sensitivity,linearity and other performance of the sensor were analyzed by the calculation of solved formula.Result shows that the sensitivity of the sensor is most affected by the film radius,followed by the thickness of the sensing film and spacing between plates.Finally,the performance of the sensor is improved by reasonably optimizing the parameters of the sensor and using SON parallel arrays.(2)Research on capacitive differential pressure sensor based on SON.A structural design of capacitive differential pressure sensor with open hole was presented.The theoretical calculation model of dynamic differential pressure of sensor was established based on the theory of plates and shells and aerodynamic knowledge,and the theoretical calculation model of sensitivity and resolution,response time and frequency response of sensor was derived.In view of the different size parameters of the sensor,the influence of the volume V of the sensor cavity and the size of the opening small aperture area S on the performance of the sensor were examined.In view of the numerical model of charge and discharge for fixed volume chambers,the fluid dynamics software FLUENT was used to simulate the flow of gas in the sensor cavity.The change in the transient pressure of the air pressure in the cavity with time was studied compared with the theoretical calculation model.Theoretical calculations show that the larger the sensor cavity and the smaller the opening circular hole,the higher the sensor's sensitivity and resolution,but the longer the corresponding response time.(3)The fabrication of a capacitive pressure sensor.On account of MSTS technology,the SON structure was prepared as the pressure sensing film and vacuum chamber of the absolute pressure sensor,and Au/Ti was sputtered on the glass substrate.The structure of the capacitance absolute pressure sensor was formed by the anode bonding process,and the transfer of Au/Ti electrode on SON structure was realized.(4)The test of capacitive pressure sensor.Finally,the designed capacitive absolute pressure sensor was tested.The experimental results show that 16 sensor arrays with a radius of 100 ?m,within the range of 10 kPa~100 kPa,the sensitivity of them is 9.19fF/kPa,the nonlinearity is 2.43%,the hysteresis error is 0.369%,and the repeatability is 1.23%,the sensor has good linearity and hysteresis characteristics.Simultaneously,the differential pressure sensor was tested and analyzed preliminarily,the experimental results show the pressure response curve of the sensor is compatible with the theoretical model to some extent.