Study On High-Sensitivity Pressure Sensor Based On Surface Micro-Machining

Sensor technology is an important indicator for the development level of modern science and technology,which with communications technology and computer technology are the three pillars of the modern information industry.In a variety of semiconductor sensors,silicon pressure sensors are the most widely used,which has a wide range of applications in automotive systems,industrial control,environmental monitoring and measurement as well as bio-medical diagnosis and many other fields.MEMS technology has provided support for the development of pressure sensor technology.Silicon surface micro-machining pressure sensor is one of the important research areas in MEMS technology.We analyze the working principle of pressure sensors firstly,and review the development of MEMS technology.In this paper,pressure sensor chip is designed for the purpose of small size,high sensitivity and integrated with the use of sacrificial layer technology.Using polysilicon as structure layer and silicon dioxide as the sacrificial layer,HF is used to release sacrificial layer,through analyze and compare a variety of sacrificial layer materials.In accordance with the characteristics of sacrificial layer,the polysilicon nanofilm is used as resistors.Then the chip of pressure sensor is simulated and optimized by finite element method and the optimal size of the chip is given. Finally according to the results of simulation and optimization,we design process of the chip,and propose corresponding solutions for the adhesion and residual stress in accordance with its mechanism.The polysilicon nanofilm is used as strain resistors in the design,which improve the performance of the pressure sensor since polysilicon nanofilm piezoresistive characteristics effectively.For pressure sensor of polysilicon nanofilm with silicon cup structure,test results show that:non-linearity(ξ_L) is less than 4‰,hysteretic(ξ_H) is less than 3‰, repetitive(ξ_R) is less than 2‰,zero point stability(r_Z) is less than 2‰,sensitivity stability (r_S) is less than 2‰,thermal zero shift(α) is less than 0.5‰,thermal sensitivity shift(β) is less than 0.2‰.Through the analysis on the test results of pressure sensor of polysilicon nanofilm with cup structure,the design results of the sacrificial layer structure sensor is verified,and the necessary reference data is provided for the development of polysilicon nanofilm pressure sensor with sacrificial layer structure.