RESUMO
This paper proposes a method to realize ideal lithium niobate (LiNbO3) A1 resonators. By introducing subwavelength through-holes between the interdigital transducer (IDT) electrodes on the LiNbO3 surface, all unfavorable spurious modes of the resonators can be suppressed completely. It is convenient and valid for various IDT electrode parameters and different LiNbO3 thicknesses. Also, this method does not require additional device fabrication steps. At the same time, these through-holes can greatly reduce the suspended area of the LiNbO3 thin film, thus significantly improving the design flexibility, compactness, mechanical stability, temperature stability, and power tolerance of the resonators (and subsequent filters). It is expected to become an important means to promote the practical application of LiNbO3 A1 filters and even all Lamb waves filters.
RESUMO
This paper proposed a solid-mounted (SM) longitudinally excited shear wave resonator (i.e., YBAR). By adopting a 200 nm x-cut LiNbO3 film, top (aluminum) and bottom (platinum) electrodes in 50 nm thickness and 500 nm width, this resonator simultaneously achieves an operating frequency over 5 GHz with an electromechanical coupling coefficient exceeding 50%. Compared with previously proposed YBAR with suspended structure, the proposed SM-YBAR can effectively suppress unwanted spurious modes with only a slight loss of the electromechanical coupling coefficient. The SM-YABR also provides better device stability, possible low-temperature drift coefficient, and a more convenient and mature device processing. It has the potential to meet the multiple requirements for the next generation signal processing devices in terms of high frequency, large bandwidth, stability, and low cost, etc.
