Design and fabrication of a SAW device with Ta filled microcavities inserted into its delay path for improved power transfer

The authors report the design and fabrication of a surface acoustic wave (SAW) device with improved power transfer due to modification of its delay path. Typically, SAW delay-line devices suffer from relatively high insertion loss (IL) (∼10–30 dB). Our approach is to incorporate an array of microcavities, having square cross-sectional area (λ/2 × λ/2) and filled with tantalum, within the delay path to maximize acoustic confinement to the surface and reduce IL. To determine the effectiveness of the cavities without expending too many resources and to explain trends found in actual devices, a finite element model of a SAW device with tantalum filled cavities having various depths was utilized. For each depth simulated, IL was decreased compared to a standard SAW device. Microcavities 2.5 μm deep filled with tantalum showed the best performance (ΔIL = 17.93 dB). To validate simulated results, the authors fabricated a SAW device on ST 90°-X quartz with microcavities etched into its delay path using deep react...