High Quality-Factor and Spectrum-Clean AlN Lamb-Wave Resonators with Optimized Lateral Reflection Boundary Conditions and Transducer Design

This paper presents a high quality-factor (Q) and spectrum-clean AlN Lamb-wave resonator (LWR). The width of its lateral reflection boundary was optimized to weaken the transverse modes’ coupling and wave guiding, and then to improve the LWR’s Q value and spectral purity, which was verified by finite element analysis and experimental characterization. In addition, the series resonance quality factor (Q(s)) value of the interdigitated (IDT)-Ground LWR is similar to that of the IDT-Floating LWR, but its parallel resonance quality factor (Q(p)) is nearly doubled, due to the reduction of the electrical loss induced by its static capacitance (C(0)). The measured results show that the designed LWR with optimized boundary reflection conditions and IDT-Ground structure exhibit Q(s) and Q(p) values as high as 4019.8 and 839.5 at 401.2 MHz and 402.9 MHz, respectively, meanwhile, it has good spectral purity. Moreover, the influence of the metal ratio and material of the LWR’s IDT electrodes on the device’s performance was also studied by theoretical analysis and experimental verification.