Bimodal Surface Acoustic Wave Sensor Based on Vanadium-Doped Zinc Oxide Film for High-Precise Pressure Measurement Enabled with Temperature Compensation

In this work, a bimodal surface acoustic wave (SAW) sensor employing a vanadium-doped zinc oxide (VZO) thin film is presented for high precise pressure measurement. The sensor is designed with multilayer waveguide structure to operate on both Rayleigh and Lamb modes to achieve temperature compensation. A 3-mask process platform on a SOI wafer based on MEMS technology is used for the development of the sensor. The influence of the oxygen/argon ratio during RF magnetron sputtering of VZO films are studied. Thepiezoelectric coefficient of the VZO film can reach to 120.3 pm/V,indicating high piezoresponse. The Rayleigh mode resonating at 312.5 MHz and the Lamb mode oscillating at 448.3 MHz of the presented sensor are observed. Calibrations of the pressure at different temperatures ranging from 25°C to 170°C have been conducted. The compensated pressure measurement error is demonstrated to be no more than 2.1%, showing a promising application prospects in high precision pressure measurements.