Nishimura Atsushi, Matsuda Satoru, Kabe Yoshiro
IEEE Trans Ultrason Ferroelectr Freq Control. 2021 May;68(5):1965-1971. doi: 10.1109/TUFFC.2020.3048030. Epub 2021 Apr 26.
This work assessed the possible correlation between the refractive index of a SiON passivation film on a surface acoustic wave (SAW) device and the temperature coefficient of frequency (TCF) of the device itself. The data demonstrate that the refractive index does correlate with the TCF as well as the frequency of the one-port resonator. SiON passivation films having an optimal refractive index can potentially suppress the frequency shifts caused by the deposition of such layers, and can change the TCF from that for a SiN film to that for SiO. The results also show that the coupling coefficient of the one-port resonator increases when using a SiON film with a lower refractive index, which changes the TCF such that this value approaches that for a SiO film. Finite-element method spectral domain analyses established that the frequency responses of the one-port resonators were affected by the velocity and temperature coefficient of velocity of the dielectric films deposited on the interdigital transducer electrodes. Thus, adjusting the refractive index of the SiON film can be used to control the properties of an SAW device, including the TCF.
这项工作评估了表面声波（SAW）器件上SiON钝化膜的折射率与器件本身的频率温度系数（TCF）之间的可能相关性。数据表明，折射率确实与TCF以及单端口谐振器的频率相关。具有最佳折射率的SiON钝化膜有可能抑制由此类层的沉积引起的频率偏移，并能将TCF从SiN膜的TCF改变为SiO的TCF。结果还表明，使用较低折射率的SiON膜时，单端口谐振器的耦合系数会增加，这会改变TCF，使其值接近SiO膜的TCF。有限元方法谱域分析表明，单端口谐振器的频率响应受沉积在叉指换能器电极上的介电膜的速度和速度温度系数的影响。因此，调整SiON膜的折射率可用于控制SAW器件的特性，包括TCF。
