Research On Small-range Pressure Sensitive Chip Based On MEMS Technology

MEMS pressure sensor is the earliest development and has a large market share of miniature sensors.Because of its advantages of small size,fast response,simple structure and easy processing of output signals,MEMS pressure sensors have been widely used in various industries such as transportation,process control,and medical.With the maturity of MEMS technology,the development of piezoresistive pressure sensors has been promoted to a small range.For small-range pressure sensors,the method of increasing the diaphragm area and reducing the thickness of the diaphragm,is generally used to make the pressure-sensitive diaphragm generate greater deformation,and improve the sensitivity of the sensor.But this easily leads to nonlinear output of the sensor.In addition,small-range sensors are prone to overload damage during use and storage,which imposes higher requirements on the overload capacity of small-range pressure sensors.For small-range MEMS pressure sensors,there is a problem of increasing sensitivity and reducing nonlinear mutual restraint.Based on the plate-shell theory,the small-scale pressure-sensitive structure is simulated and analyzed,and the design method that takes into account the two mutually-restricted technical indicators is given.Based on the SOI technology,a piezoresistive small-range pressure sensitive structure is designed.By optimizing the size of the structure,the sensor has good linearity in the range.Using the size effect of polysilicon tensile strength,the overload capacity of the sensor is analyzed.The overload capacity of the sensor can be effectively increased by proper contact with the substrate before rupture.The sensor designed in this task has a measuring range of 5KPa.The length and width of the elastic diaphragm is determined based on the relationship between the diaphragm size and sensitivity and the linearity of the sensitive structure.The width of the elastic diaphragm is 300?m and the length is 600?m.After a linear static analysis,the layout of the varistor was determined,combined with the sensitivity and the diaphragm thickness was designed to be 2.5?m.The method of determining the cavity height is given by nonlinear contact analysis.The height of the cavity is designed to be 5?m.The designed pressure sensitive chip has a sensitivity of 8.638mV/KPa when it is powered from a 1mA constant current source,a full-scale voltage output of 43.2mV,and an overload capacity of 1MPa.Based on MEMS technology,a piezoresistive small-range pressure sensor is designed.By optimizing the design of the sensor's structure size and reasonable layout of the strain resistance,the resolution and sensitivity of the small-range pressure-sensitive chip and the anti-overload capability are improved.In addition,the key technologies in the process are analyzed and summarized.Based on the direct bonding technology and SOI technology,the pressure sensitive chip-related process flow and the corresponding layout design are given,providing a design scheme for the manufacture of sensors.