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改变传感器可动极板的结构是解决MEMS电容式压力传感器信号输出与压力输入呈非线性关系问题的方法之一。设计了一种新型结构电容式压力传感器,其可动极板是LPCVD氮化硅构成的一个方形薄膜,薄膜中心到边缘之间由PECVD氧化硅构筑一个环形岛棱,使可动极板在压力负载下的变形趋于平整,减小了边缘杂散电容带来的非线性,从而改善了该传感器的输出特性。利用有限元方法分析了不同尺寸的动极板在不同外加压力作用下压力与形变的关系,以及相应的应力分布情况,并采用最小二乘拟合直线法计算了压力传感器的线性度。分析结果表明,与常规的双极板微型电容式压力传感器相比,新型结构压力传感器的线性度改善了48 .38 %,达到了1 .6 %。
Changing the structure of the movable electrode plate of the sensor is one of the methods to solve the problem of nonlinear relationship between the signal output and the pressure input of the MEMS capacitive pressure sensor. A new type of capacitive pressure sensor is designed. The movable plate is a square film made of LPCVD silicon nitride. An annular island edge is formed by PECVD silicon oxide between the center of the film and the edge, The deformation under load tends to be flat, reducing the non-linearity brought by the edge stray capacitance, thus improving the output characteristics of the sensor. The relationship between pressure and deformation under different applied pressure and the corresponding stress distribution were analyzed by finite element method. The linearity of the pressure sensor was calculated by the method of least square fitting straight line. The results show that the linearity of the new structural pressure sensor has been improved by 48.38% to 1.6% compared to conventional bipolar plate miniature capacitive pressure sensors.