Research Of Polysilicon Nanofilms Acceleration Sensor Sturcture

The paper discussed the process of Micro-electro mechanical system (MEMS). The production of the research on silicon piezoresistive acceleration sensors home and abroad is analyzed. The principle and properties of ultra-thin micro-beam piezoresistive acceleration sensor were presented. According to the application of trigger automobile airbag which range is±100g, the structure and fabrication process of sensor chip were designed.Through the introduction of typical structure piezoresistive acceleration sensor and the production of research on silicon piezoresistive acceleration sensor home and abroad is analyzed, as well as the comparison of performance between piezoresistive, capacitive and piezoelectric three kinds of acceleration sensor, summed up the advantages and disadvantages of piezoresistive acceleration sensor. The reason of piezoresistive acceleration sensor's low sensitivity, bad temperature characteristics and narrow frequency range is analyzed. Through the use of polysilicon nanofilms as the strain resistance and an acceleration sensitive structure with Ultra-thin micro-beam, the design of this kind of structure optimized the compromise between sensitivity and temperature characteristics as well as compromise between sensitivity and natural resonant frequency, consequently, the performance of the piezoresistive accelerometer has been largely improved. Polysilicon piezoresistive nano-film has excellent characteristics: high-strain factor, temperature coefficient power group, strain factor temperature coefficient is small, sopolysilicon nanofilms has been adopted as the strain resistance in this paper. An acceleration sensitive structure with Ultra-thin micro-beam of 300nm thickness which is composed of Si3N4-PolySi Nanofilm- Si3N4 three layers has been designed. It improved the sensitivity at the same time effectively improved the temperature characteristics. In this paper, acceleration sensor is simulated by ANSYS analysis software, through structural static simulation and modal analysis, the sensor structure was optimized, and analyzed the performance. The simulation result shows the sensitivity of acceleration sensor with Ultra-thin micro-beam is 0.65mv/g, and the resonant frequency is 68kHz. This result shows that the structure maintain a high sensitivity at the same time substantially increase the resonant frequency, which made the product of this two factors increase more than 30 times.