压阻式压力传感器微结构塑性形变及影响

Plastic Deformation of Micro Structure and Its Influence on Piezoresistive Pressure Sensors

由于体硅微机械工艺制作绝压压阻式压力传感器的过程中,通过Si-Si直接键合形成的带真空腔的微结构在高温和大气压的作用下会产生塑性形变,对器件制作工艺中微结构发生的塑性变形及其对器件性能的影响进行了研究。基于Von Mises屈服准则和有限元仿真,微结构发生塑性变形的临界工艺条件可以通过比较微结构的最大等效应力和材料屈服强度进行预测。在器件的制作过程中,Si-Si键合和扩散电阻条的工艺顺序不同,将会导致塑性变形对器件的影响程度也不同。实验结果表明器件塑性形变量与弹性形变量成线性正比关系;在先进行Si-Si键合后扩散电阻的情况下,器件电阻值远远偏离设计值,反之则会减小塑性变形对器件电阻值的影响。

Based on the micromechanical fabrication process of bulk silicon, the vacuum cavity of the absolute pressure sensor formed by Si-Si direct bonding would be plastic deformed under high temperature at normal atmosphere. The plastic deformation of micro-structure and its influence to pressure sensors＇ properties were studied. By comparing the maximum Von Mises stress of the structure and the yield stress of silicon, the Von Mises yield criterion is used to predict whether the micro structure could produce plastic deformation. In the fabrication process of sensors, the different sequence of Si-Si direct bonding and ion diffusion would lead to the different influence on the sensors caused by plastic deformation. The experimental result shows that the plastic deformation of pressure sensors is proportion to its elastic deformation, and they keep a linear relationship ; the resistance of the device is far deviated from the designed value under the condition of diffusion resistance after the Si-Si bonding firstly; otherwise it will reduce the effect of the plastic deformation on the resistance.