Effect of Alumina Film on Surface Acoustic Wave Properties of ZnO Thin Film Surface Acoustic Wave Devices

概要

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ZnO films with $c$-axis (0002) orientation have been successfully grown by RF magnetron sputtering on Al2O3/SiO2/Si substrates. The alumina films were deposited on SiO2/Si substrates by electron beam evaporation. Crystalline structures of the films were investigated by X-ray diffraction, atomic force microscopy, and scanning electron microscopy. The phase velocity of the surface acoustic wave (SAW) device with a 8-μm-thick alumina film was measured to be about 4733 m/s, which is much higher than that (4069 m/s) of the ZnO/SiO2/Si structure and approaches (89.6%) that (5283 m/s) of ZnO/sapphire. The coupling coefficient and temperature coefficient of the frequency of the ZnO/Al2O3/SiO2/Si structure with 8-μm-thick alumina film were close to those of the ZnO/sapphire structure. The experimental result is beneficial to the replacement of the expensive single-crystalline sapphire substrate with alumina film at lower cost for high-frequency SAW devices, and is also useful for integrating the semiconductor and high-frequency SAW devices on the same Si substrate.
2010-09-25