基于非晶碳膜压阻效应的MEMS压力传感器研究

MEMS Pressure Sensor Based on Piezoresistive Effect of Amorphous Carbon Film

目的研究非晶碳膜的压阻性能和机理,并将其作为压敏电阻应用于MEMS压力传感器敏感电路中。方法使用直流溅射工艺制备非晶碳膜压敏薄膜材料,对典型样品进行内部组分和电学、力学、温度等性能测试和研究,使用有限元方法进行器件设计仿真,借助MEMS加工工艺完成非晶碳膜压力传感器芯片的加工,最后进行器件级别的测试和分析。结果在0~1 MPa范围内,压力传感器芯片的灵敏度为9.4μV/kPa,输出信号的非线性度为5.57%FS;对压敏电阻进行–70~150℃范围内的温度性能研究,其阻值与温度之间表现出较强的线性关系,且在–20~150℃段,线性度更强,表明非晶碳膜压敏材料在高温段应用时更容易补偿。机理研究方面,非晶碳膜在厚度方向上表现出组分差异化,因此该方向也应被纳入机理模型建立中。结论非晶碳膜在加工工艺、力学性能以及电学性能上与传统的MEMS传感器芯片能够很好地结合,加工得到的非晶碳膜压阻式压力传感器灵敏度和线性度较为理想。此外,其压阻机理研究应纳入薄膜厚度方向。

The paper aims to study the piezoresistive performance and mechanism of amorphous carbon(a-C)film and apply it in the sensitive circuit of micro-electromechanical system(MEMS)pressure sensor.In this paper,the a-C film piezoresistive material was deposited by direct-current(DC)sputtering process.The phase content and the electrical,mechanical and thermal performance of the representative sample were characterized.Then the device was designed by finite element simulation.And the a-C carbon film pressure sensor was successfully fabricated by MEMS processes to carry out test and analysis of device level.The sensitivity of the pressure sensor chip was 9.4μV/kPa and the non-linearity of output signal was 5.57%FS(full scale)in the range of 0 to1 MPa.The change of the a-C film resistor’s resistance showed linear relation at–70 to 150℃.Especially at–20 to 150℃,that relation was stronger,which showed that the temperature compensation for the a-C piezoresistive material was easier in high temperature environment.The phase content varied along the thickness-direction of the film,which implied this direction was also needed to be considered in the mechanism research.In conclusion,the a-C carbon film can be well-combined with the traditional MEMS sensor chip in terms of fabrication process,and mechanical and electrical properties.Finally,the a-C piezoresistive pressure sensor also shows satisfactory sensitivity and linearity Furthermore,the thickness-direction of a-C film should be added into the mechanism research.