Pressure Sensitivity Evaluation of Passive SAW Microsensor Integrated with Pressure-Temperature and ID Tag on 41°-YX LiNbO3

This paper presents a mechanical analysis on pressure sensitivity of a passive pressure sensor incorporating surface acoustic wave (SAW) reflective delay line (RDL) on 41deg-YX LiNbO₃. The behavior of shear horizontal (SH) leaky type SAW propagating on pre-stressed LiNbO₃ substrate was investigated using partial-wave-analysis. Referring to the finite element methods (FEM), the pressure sensitivity in the propagation path of SAW was calculated and the effect of the diaphragm thickness on the sensor performance was also studied, which shows proper thickness of LiNbO₃ diaphragm makes it possible to obtain better sensitivity than quartz. Theoretical results were verified by the sensor experiment. We have developed a pressure sensor on 41deg-YX LiNbO₃ integrated with temperature sensor and 8-bits ID tag, which was structured by 440 MHz two-layered-RDL, in which a - 150 mum cavity was designed by Ni electroplating. Fabricated sensor was wirelessly characterized by HP network analyzer. High S/N was observed from the measured S₁₁. Satisfactory pressure sensitivity of -2.9deg/kPa was obtained.