MEMS电容式表压压力传感器研究

Research on MEMS Capacitive Gauge Pressure Sensor

摘要:

微型电容式压力传感器在生物医疗、无人机定位、可穿戴设备等领域有着重要的应用价值。本研究以MEMS电容式表压压力传感器为研究对象，面向植入式生物医疗应用设计并制造了一款高精度的压力传感器。本器件由带固定极板的玻璃衬底和带膜片的SOI晶圆通过阳极键合形成。当存在压强差时，膜片产生形变导致器件电容的变化，进而读出电路通过检测变化电容计算出外界压强。在结构设计上，本文提出了带膜片的凸台设计，实现了对电容式压力传感器非线性问题的改善，在ANSYS有限元仿真下，非线性度由无膜片的约17%改善到7%。凸台结构的制造工艺采用TMAH对硅的各向异性腐蚀而成，并将SOI埋氧层作为停止层得到了较高的器件一致性。最后搭建了电容式压力传感器的封装测试平台，并对输出结果进行标定。最终在0~40kPa相对大气压的压力值的测量范围下，本器件实现了0.30%的测试精度、8%的非线性度以及低至0.09%的重复性误差。

Abstract:

Micro capacitive pressure sensors have important application value in fields such as biomedicine, drone positioning, and wearable devices. This study focuses on MEMS capacitive gauge pressure sensors. A high-precision capacitive pressure sensor is designed and fabricated for implantable biomedical applications. This device is formed by anodic bonding between a glass substrate with fixed electrodes and an SOI wafer with elastic membranes. The elastic membrane will deform when the pressure on both sides changes, resulting in a change in the capacitance of the device. The readout circuit calculates the external pressure by detecting changes in capacitance. This paper improved the nonlinearity of capacitive pressure sensors by designing a structure of a boss on the membrane. The result from ANSYS finite element simulation shows that the nonlinearity was improved from about 17% (flat membrane) to 7% (with boss structure). The structure of the boss was formed by anisotropic etching of silicon with TMAH, and the SOI buried oxide layer serves as the stop layer of etching to achieve high device consistency. Finally, a packaging and testing platform is built for capacitive pressure sensors and calibration. In the measurement range of 0 ~ 40kPa relative to atmospheric pressure, this device achieved a testing accuracy of 0.30%, nonlinearity of 8%, and repeatability error as low as 0.09%.