High-performance surface acoustic wave devices using composite substrate structures

Abstract

In this paper, first, the surface acoustic wave (SAW) propagation mode and a method of analyzing the propagation property are introduced briefly. Then, typical composite substrate structures that have been developed to obtain high-performance SAW devices are reviewed. Furthermore, the recent results obtained by the author and research colleagues on the propagation and resonance properties of leaky SAW (LSAW) and longitudinal-type LSAW on dissimilar-material bonded structures comprising a LiTaO3 (LT) or LiNbO3 thin plate with a thickness of less than 1 λ (λː wavelength) and a quartz substrate are described. The control of attenuation and the cause of large coupling factor of LSAWs by utilizing layered structures were also discussed. For the bonded 4 inch wafer of 36°YX-LT/AT90°X-quartz with a thin-plate thickness of 0.3 λ, an admittance ratio of 81 dB, a fractional bandwidth of 4.2%, and resonance and antiresonance factors of approximately 1500 with markedly improved properties compared with a single 36°YX-LT substrate were obtained experimentally at 2.2 GHz.

Development of calculation model for designing temperature characteristics of double-layered thickness-shear resonator

“…[23][24][25][26] In recent years, research has been actively conducted to achieve high coupling, low loss, and high stability by bonding dissimilar materials between thin plates of LT and LN and higher acoustic velocity support substrates such as sapphire, AlN, Si, and quartz. [27][28][29][30][31] For the bulk acoustic wave (BAW) devices, high coupling and stability have been achieved by the solid mounted resonator type thin film resonators in which high and low acoustic impedance films are alternately laminated [32][33][34] and by the film bulk acoustic resonator using compensation layer of fluorine-doped SiO 2 . 35) Although temperature dependence can be reduced by the various structures described above, they cannot be completely eliminated over a wide temperature range.…”

Comparative study of piston mode designs for temperature-compensated surface acoustic wave resonators using SiO2/LiNbO3 structure

“…[10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] The incredible SAW structure using an ultra-thin LT/LN layer can be regarded as a combination of these technologies. [26][27][28][29][30] Among them, SiO 2 covered 128°YX-LN is most commonly used as the TC-SAW structure. 12,13,[21][22][23][24][25] In this configuration, one of the most important design goals is the suppression of transverse mode resonances.…”

c-Axis-tilted ScAlN films grown on silicon substrates for surface acoustic wave devices

“…Surface acoustic wave (SAW) devices with a high frequency (gigahertz range), high electromechanical coupling coefficient K 2 , and high Q factor are required for filters and duplexers in smartphones. [1][2][3] In particular, high K 2 values contribute to the wide bandwidth of SAW devices. The piezoelectric film/high-velocity substrate structure offers great advantages in the fabrication of SAW devices with a high electromechanical coupling coefficient K 2 .…”