Transducer design for AlN Lamb wave resonators

Abstract

AlN Lamb wave resonators enjoy advanced and attractive properties for enabling the next-generation single-chip radio frequency front-end, but their moderate effective electromechanical coupling coefficient (k2eff) poses a limit to their application in filters and multiplexers. Despite the fact that the reported k2eff enhancement techniques of doped AlN thin films which are expensive and trade off the quality factor (Q), the transducer topology itself extensively impacts the k2eff value. Although an AlN cross-sectional Lame mode resonator exhibiting a k2eff of 6.34% has been demonstrated without the need for changing the piezoelectric material, a detailed study of transducer design for AlN Lamb wave resonators has not been conducted. In this work, we investigate the impact of (i) transducer configurations, (ii) electrode materials, (iii) electrode thicknesses, and (iv) interdigital transducer duty factors on the k2eff dispersive characteristics of one-port AlN Lamb wave resonators by using the finite element analysis approach. By properly designing and optimizing the transducers, the k2eff of one-port AlN Lamb wave resonators can be boosted to as high as 7.7%, showing great potential for applications of cellular frequency selection.

Enhanced Performance of ZnO/SiO2/Al2O3 Surface Acoustic Wave Devices with Embedded Electrodes

“…This is likely due to the fact that the energy distribution in electrodes is relatively small in the embedded IDT structure compared to the conventional IDT structure, which can decrease the Bragg reflection and acoustic scattering in the surface of the IDT region, thus yielding a more drastic displacement. , As previous studies pointed out, different configurations of IDT electrodes will result in different distributions of the SAW field and electric field. If the SAW field distribution matches well with the electric field generated by IDTs, the SAW will be more efficiently excited and K 2 can be enhanced. , In this work, when the IDTs are embedded under the piezoelectric layer, energy degradation in non-piezoelectric IDT electrodes is decreased and SAW is efficiently excited in piezoelectric films, so that the enhancement of K 2 can be realized. A similar result has also been observed in a previous work …”

A MEMS Fabrication Process with Thermal-Oxide Releasing Barriers and Polysilicon Sacrificial Layers for AlN Lamb-Wave Resonators to Achieve fs·Qm > 3.42 × 1012

“…The Q s attenuation is mainly caused by the following two factors: the TED loss of the Au IDTs is much higher than that of the Al IDTs; the better acoustic impedance matching between AlN and Au will induce obvious acoustic-energy dissipation. The mass density and acoustic impedance of different materials are listed in Table 3 [ 24 ].…”

Numerical Investigation of an AlN-Based Resonant Detector with a Plasmon Aperture Absorber for Dual-Band IR Sensing

“…The bottom Mo layer with the thickness of 200 nm is patterned to form interdigital transducers (IDTs) to actuate and to sense Lamb-wave modes in the AlN film. The Lame-wave resonant frequency mainly depends on the period P of IDTs [22]. The suspended free edges are not only formed as solid-air interfaces to reflect Lamb waves, but they can also increase the thermal resistance R th .…”