A 4.5 GHz Surface Excitation Solidly Mounted Microacoustic Resonator with 20% Coupling

Thanks to improved wafer bonding technologies it is now possible to manufacture wafers with thin single crystal lithium niobate (LN) films with arbitrary orientation. Previous research has focused on interdigitated transducer (IDT) resonators on an LN membrane and cavity. In this work a solidly mounted LN IDT resonator is demonstrated. Hafnium oxide is chosen as a high acoustic impedance reflector material to reduce the parasitic capacitance caused by conductive layers. To ensure the modeling accuracy of hafnium oxide, delay lines have been used to extract a shear stiffness coefficient of 94.4 GPa. To maximize resonator coupling, the LN orientation is chosen to be YX 1 120°• Solidly mounted LN IDT resonators with coupling larger than 20% are demonstrated.