Study On Overload Characteristics Of Linkage Thin Film Pressure Sensitive Chip

Pressure sensor is one of the important research directions of MEMS sensor.Capacitive pressure sensor has the advantages of small size,simple structure,small temperature drift and high sensitivity.It plays an important role in aerospace,industrial engineering,automotive electronics,scientific experiments and other fields.At present,the capacitive pressure sensor has achieved commercial development in the normal range pressure range,and there are few researches on the pressure sensor with micro-range(below 10KPa).Because the range of the micro-range pressure sensor is small,it is easy to be damaged due to overload during transportation and storage,and the harsh use environment in the fields of industrial engineering and aerospace has higher requirements on the overload capacity of the pressure sensor,so it is of practical significance to study the micro-range pressure sensor with good output characteristics and strong overload capacity.Aiming at the application requirements of micro-range pressure sensors,this thesis conducts in-depth research on the new capacitive pressure-sensitive sturcture with linkage film(CPSSLF),focusing on the output characteristics and overload capacity of the pressure sensitive structure.The finite element simulation software is used to model and simulate the sensitive structure,and the square membrane sensitive structure and the circular membrane sensitive structure are compared and analyzed.The simulation shows that the circular membrane structure has a larger linear working range and stronger overload capacity.The size of the lower plate and the dielectric layer of the sensitive structure is optimized by finite element simulation,so that the pressure sensitive structure has better output characteristics.In this thesis,the experimental test results of the fracture strength of single crystal silicon thin film samples are fitted with a function,and the size effect of the fracture strength of single crystal silicon is used to improve the overload capacity of the sensitive structure.Finally,the height of the lower cavity is optimized to ensure the linear response within the range of the sensitive structure,and the overload capacity of the sensitive structure is further improved by the support of the substrate.The simulation results show that the designed linkage film pressure sensitive chip with a range of 4KPa can make the sensitive structure have better output characteristics and overload capacity through reasonable size optimization.The final simulation shows that the linear working range of the sensitive structure is 1.6～4KPa,the sensitivity is 1.02 pF/KPa,the nonlinearity is 0.998%,and the overload is 13.5MPa.The paper also conducts a comparative study between the CPSSLF structure and the traditional contact capacitive pressure sensor(TMCPS).The results show that the linear working range of the CPSSLF structure is about 1.8 times that of the TMCPS structure,so the CPSSLF structure has a broader prospect in micro-range applications.In this thesis,the linkage thin-film pressure-sensitive chip based on SOI technology is deeply studied.By optimizing the size of the sensitive structure,the output characteristics of the pressure-sensitive chip with a micro-range are improved,and the overload capacity of the sensitive chip is improved.In addition,the process flow of the linkage film pressure-sensitive chip is given,and the key technologies in the process are analyzed and summarized.Finally,the layout of the pressure sensor is designed,which provides a feasible scheme for the production and preparation of the micro-range pressure sensor.