谐振式MEMS温度传感器设计

为了实现以频率输出为信号的气象温度测量,提出了一种基于双层悬臂梁的谐振式微温度传感器。基于双悬臂梁不同材料热膨胀系数的差异会导致悬臂梁谐振频率偏移的原理,采用压电方式同时实现悬臂梁的驱动及其谐振频率的检测,从而实现温度的测量。根据硅基传感器的正面腐蚀工艺,设计了谐振悬臂梁的双层结构,采用有限元方法分析了悬臂梁的谐振模态、可利用的振型及其温度与各模态谐振频率的关系,并利用多普勒振动系统对悬臂梁的谐振特性进行了研究。实验发现悬臂梁的二阶弯曲振型Q值相对于其它振型是最大的,其Q值约为150;高阶振型特别是二阶弯曲振型适合用于以ZnO为压电材料的温度传感器的频率检测,并且具有相对较高的灵敏度(约为20Hz/℃)和频率温度系数(1.9×10-4/℃)。结果表明,微型温度传感器能够满足气象温度检测的要求,并具有抗干扰能力强、灵敏度高、信号传输接口简单等优点。

Design of resonant MEMS temperature sensor

In order to realize meteorologic temperature measurement based on frequency outputs, a resonant micro-temperature sensor with a bilayer cantilever was proposed. According to the working principle that the resonant frequency of the microcantilever will be shifted due to the thermal expansion coefficient mismatch between the two-materials,the temperature variation could be detected by driving the cantilever and detecting the resonant frequency with piezoelectric excitation and detection. The structure of the temperature sensor was designed according to the front side fabrication process of silicon. Then, the resonant modes, detectable models and the effect of temperature on these models were analyzed by means of finite element method. The resonant characteristics were also researched with a polytech laser Doppler vibrometer. The results indicate that the 2nd resonant model of the cantilever has the largest Q factor about 150 as compared with other resonant models. Furthermore, the higher mode, particularly the 2nd resonant model is more suitable for detecting the resonant frequency of the temperature sensors by utilizing ZnO as piezoelectric materials and it can offer a relative higher sensitivity about 20 Hz/℃ and temperature coefficient of frequency about 1.9×10^-4/℃. These results show that the sensor can satisfy the requirements of meteorologic temperature measurement and has the advantages of high electrical stability, high sensitivity and simple signal transmission interface.