面向高温传感的AlN/Sapphire声表面波谐振器研究

Research on AlN/sapphire SAW Resonator for High Temperature Sensing

摘要:

目前，基于硅酸镓镧（LGS）的无线SAW传感器能够在高达600 °C的温度下工作。但随着频率和温度的增加，LGS的传播损耗也会急剧上升，因此基于LGS的SAW传感器工作频率仅在1 GHz左右。而基于氮化铝/蓝宝石（AlN/sapphire）结构的声表面波（SAW）谐振器因其耐高温、高Q值、低传播损耗在高温传感领域有着巨大的应用前景。本文针对基于AlN/sapphire结构SAW谐振器，采用耦合模式（COM）模型结合有限元（FEM）方法，建立了仿真谐振器的有效模型。研究了不同的叉指换能器（IDT）对数、反射栅对数及孔径长度对器件性能的影响，模拟了不同温度下的谐振频率与温度的关系，并与实验结果进行对比。结果表明：谐振器的工作频率高达2.45 GHz，在高达500 °C的温度范围内可靠工作，频率温度特性具有较好的线性度，温度系数高达-67×10^‒6 ℃^‒1。这为设计高性能的声表面波高温传感器提供了重要的参考。

Abstract:

The current wireless SAW (Surface Acoustic Wave) sensor based on langasite (LGS) can work at temperatures as high as 600 °C. Nevertheless, the propagation loss of LGS increases significantly as frequency and temperature increase, which limits the operating frequency of the SAW sensor based on LGS to 1 GHz. However, SAW resonator based on AlN/sapphire structure exhibits gigantic potential for high-temperature sensing applications due to its resistance to high temperatures, high Q-factor, and low propagation loss. In this work, an efficient model for SAW resonator based on AlN/sapphire is developed using the coupled mode (COM) theory combined with the finite element method (FEM). The influence of different numbers of interdigital transducers (IDT), reflective gratings, and different aperture lengths on device performance are investigated. Furthermore, the relationship between resonant frequency and temperature at various temperatures is simulated, which compares well with that of the experimental results. The investigation results show that the resonator works reliably in the temperature range of up to 500 °C and the operating frequency of up to 2.45 GHz. The frequency-temperature characteristics exhibit good linearity, with a temperature coefficient of -67×10^‒6 °C^‒1. This work provides an important reference for designing high-performance SAW high-temperature sensors.