Design and fabrication of SiO2 waveguide-based SAW sensors with filled microcavities

To realize the potential of SAW devices in portable sensing applications, it is important to reduce the power consumption and improve sensitivity of existing surface acoustic wave (SAW) sensors. In this work, we designed several SAW sensors based on ST 90°-X quartz and silicon dioxide (SiO₂) waveguide with or without filled microcavities to achieve both these in a single device. A 3D finite element model (FEM) was employed to compare insertion loss (IL) and mass sensitivity of these SAW sensors to systematically evaluate the advantages of using waveguide and microcavities. Our FEM simulation results illustrated that a sensor device comprised of SiO₂ waveguide layer with Tantalum filled cavities has the lowest insertion loss whereas a device configuration consisting of an SiO₂ waveguide layer with SiO₂ filled cavities displays the highest sensitivity of ~138.48 Hz*cm²/ng, which corroborates well with our experimental observation.