AlN/6H-SiC SAW resonator for high temperature wireless SAW sensor

Abstract

For the first time, a surface acoustic wave (SAW) resonator based on the AlN/6H-SiC multilayer structure is designed and fabricated. Firstly, we have succeeded in solving the problem of obtaining AlN (002) on 6H-SiC substrate. The results show that highly c-axis-oriented AlN thin films are obtained, with that the diffraction peak of AlN is 36.121° and the lowest full width at half maximum (FWHM) value is only 0.62°. Besides, a MEMS-compatible fabrication process is employed to fabricate the SAW resonator by using lift-off photolithography techniques. The center frequency of the Mo/AlN/6H-SiC SAW resonator at room temperature is 549.075 MHz. In order to investigate the high-temperature (from 25 °C to 300 °C) performances of the SAW resonator, a high temperature real-time testing system was established. The temperature coefficient of frequency (TCF) values is — 0.04969 MHz/°C, which makes the SAW resonator a potential temperature sensor in high temperature applications.