Analysis And Research On Mechanical Properties Of Micro Pressure Sensor Chip

Sensor technology is important in the development of modern science and technology. It is one of three greatest technique of the information industry. Silicon pressure sensor is the mostly widely used among all the kinds of sensors, which includes piezoresistive, capacitive and resonant sensors. At present, piezoresistive pressure sensors are applied most widely, that mostly are made by forming diffused strain gauges on the thin silicon diaphragm. This sensor uses isolation by reverse biased pn-juncitons, whose junction leakage current rises at elevated temperature over 120℃, which deteriorate sensor characteristic so serious that it would disable the sensor.With the emergence of new technology and new materials in MEMS industry, pressure sensor develops along the direction of microminiaturization and low range. In order to improve the device's sensitivity, the stress on the resistance must be increased at the same pressure and chip area, namely make the stress concentrate on the resistance. The usually used method is to reduce the thickness of silicon membrane. But on the one hand, it would be more difficult to control the thickness in process, and increase the uneven of thickness. On the other hand, when the thickness is very small, silicon membrane bending is the nonlinear bending of large deflection, resulting in sharp increase in nonlinearity, consequently reduces the accuracy of device. To obtain higher sensitivity and better linearity simultaneously, the structure of silicon diaphragm must be improved to replace original pn-juncitons, to enhance the working temperature and stability. In this thiesis analysis and research on Mechanical properties of micro pressure sensor chip is to provide theoretical basis for the research and development of micro high temperature pressure sensor.Firstly, stress distributions of three types of strain diaphragm: C-type flat diaphragm, E-type diaphragm and double-island diaphragm are analyzed and compared by material mechanics, elastic mechanics theory and theory of plates and shells to provide theoretical basis for simulation, analysis and the disposition of sensing resister on strain membrane.Secondly, three types of pressure sensor chips are simulated by using ANSYS software on the account of Finite Element Analysis (FEA) theory. The stress distribution of strain diaphragm, rationality of the simplified model, the effect of dimension of strain diaphragm on the difference between stresses and temperature on the distribution of thermal stress and temperature field on the strain membrane is discussed. Then, the paper investigates how to realize the structure optimization of chip by using the ANSYS software. The simplified mechanics model of double-island diaphragm is established, parameter model and mathematics model are optimized, and analysis file and control document are also optimized. The optimal result, the output-input relation of optimum design and the relation between design variables and object function are obtained by using ANSYS. The distribution, dimensions and resistance of sensitive resistor on sensor and the manufacture technology process are designed.At last, dynamic characteristic of sensor chip is studied in modal, harmonic and transient structure dynamics by ANSYS software, and dynamic response characteristic is attained from the analysis result.