Parylene封装对MEMS声学传感器性能的影响研究

Study on the Effect of Parylene Encapsulation for the Performance of MEMS Acoustic Sensor

该文通过有限元仿真获得微机电系统(MEMS)声学传感器在Parylene-C封装前后的灵敏度变化,并以集总参数等效电路模型推导出器件的接收灵敏度与电压激励下薄膜振幅的转换系数K_(rt),从而探究了Parylene-C封装对器件功能的影响。测试结果显示,器件的接收灵敏度和振幅均值在封装后分別降至原有的42%和48%,两者降幅相近,这表明封装前后K_(rt)不变,因此,通过测量谐振振幅可评估器件灵敏度的变化。采用此方法对同一批器件进行快速筛选,可提高效率;同时仿真得到封装后的灵敏度降至55%,与振幅测试结果相近,二者相互印证。

In this paper,the change of receiving sensitivity for a MEMS acoustic sensor before and after Parylene-C encapsulation was achieved through finite element simulation,and the conversion coefficient K_(rt) between the receiving sensitivity and vibration amplitude of diaphragm from excitation voltage was derived from the Lump-element model,and then the influence of Parylene-C encapsulation on the device performance is explored.Our experimental results showed that the sensitivity and mean vibration amplitude of the device were reduced to 42%and 48%of the original values,respectively,after encapsulation.The similar reduction percentage in sensitivity and mean vibration amplitude indicated K_(rt) was independent from the encapsulation.Therefore,the change of device sensitivity can be evaluated by measuring the mean vibration amplitude instead of time-consuming sensitivity measurement,and this method can be used to quickly screen the same batch of devices and improve the efficiency.Moreover,the simulation results show that the sensitivity is reduced to 55%from original value after encapsulating,which is close to the test results of amplitude,and the two confirm each other.