The Analysis and Mems Fabrication of Surface Acoustic Wave Devices with Phononic Reflective Gratings on Piezoelectric Materials

Phononic crystal (PC) consisting of periodic media or periodic geometric structures is a new acoustic metamaterial. PC structures perform anisotropic propagation and acoustic band gaps for various acoustic waves, including bulk acoustic wave, surface acoustic wave (SAW), and Lamb waves. PC applications were also proposed for acoustic-electronic components, such as filters, reflective gratings, waveguides, and resonant cavities. SAW devices are widely used and suitable to combine with PCs. Currently, to make the fabrication feasible, the PCs used in SAW devices usually consist of cylindrical air holes with high aspect ratio in Si matrix. Then piezoelectric film was fabricated on the surface of Si wafer to make inter-digital transducer (IDT) work. However, the electromechanical coupling coefficient of piezoelectric film is small and lowers the performance of SAW devices. In this project, PCs on piezoelectric half-space will be studied. PCs will be constructed within a finite thickness layer on a piezoelectric substrate. This design can make the fabrication more feasible and improve the performance of SAW devices combined with PCs. Firstly, acoustic waves in the layered-structure PC structure should be analyzed to identify the range of band gaps and design PC reflective gratings accordingly. The dispersive of SAW in the region without PC will also be calculated for designing IDT. Combining the PC grating and IDT, a SAW device will be constructed and fabricated by MEMS process. Finally, frequency response of the SAW device will be measured and compared with the numerical analyses. The study is expected to be valuable for applying PCs in SAW devices.

Project ID:PB10207-1794
External Project ID:NSC102-2221-E182-018