薄膜体声波谐振器的伽马辐照敏感机理分析

摘要

Thin film bulk acoustic resonators(FBARs) are feasible to detect gamma irradiation by experiments,but the sensing mechanism has not been thoroughly studied.According to two different FBAR structures,two sensing mechanisms are proposed to explain the resonance frequency shift under gamma irradiation.One FBAR structure is four-layer stacked(metal layerpiezoelectric layer-oxide layer-metal layer),after gamma irradiation,it will form a voltage in the radiation sensitive layer(the oxide layer),which is equivalent to impose a DC voltage on the piezoelectric layer,hence the resonant frequency will shift.There is a semiconductor layer between the oxide layer and the piezoelectric layer in the other FBAR structure,and a voltage formed in the oxide layer after irradiation will change the surface potential of the semiconductor and then change the capacitance of the semiconductor space charge layer and finally change the resonant frequency.The results of two different mechanisms are obtained by simulation and compared with the results of the related literature.It is found that the trend of frequency shift and the magnitude of frequency shift are the same,which suggests that the two mechanisms are feasible.%实验证明薄膜体声波谐振器(FBAR)用于检测伽马辐照是可行的,但未对敏感机理进行深入研究.针对这一问题,根据两种不同的FBAR结构,提出了不同机理来解释FBAR在伽马辐照下谐振频率偏移的原因.其中结构一FBAR为四层叠层结构(金属层-压电层-氧化层-金属层),伽马辐照之后,会在辐照敏感层(氧化层)形成一个电压,相当于给压电层施加了一个直流电压,从而使谐振频率发生偏移;结构二与结构一不同的是,结构二FBAR在氧化层和压电层之间有一半导体层,辐照之后在氧化层中形成的电压改变了半导体的表面势,使半导体空间电荷层电容发生改变,从而改变谐振频率.通过仿真得到两种不同机理的结果,并与相关文献的测试结果对比,发现频率偏移的趋势和频率偏移量的数量级是相同的,因此提出来的两种机理是可行的.