The Preparation of Piezoelectric ZnO Films by RF Magnetron Sputtering for Layered Surface Acoustic Wave Device Applications

概要

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Crystalline structures, intrinsic stress, and surface roughness of piezoelectric ZnO films deposited on sapphire substrates by rf magnetron sputtering and sequential post-annealing treatments were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements. The rf power used and $\text{O$_{2}$}/(\text{Ar}+\text{O$_{2}$})$ gas ratio greatly affected the crystallinity and surface roughness of the ZnO film. A $c$-axis preferred orientation with superior surface roughness was achieved at a specific rf power and $\text{O$_{2}$}/(\text{Ar}+\text{O$_{2}$})$ gas flow ratio. In addition, the original intrinsic stress was also markedly released ($\text{stress}=0.325 \times 10^{10}$ dyn/cm2) and a uniform surface ($R_{\text{a}}=2.42$ nm) was produced by a post-annealing treatment at a temperature of 400 °C under oxygen ambient. An acoustic wave at the center frequency of 240 MHz ($h_{\text{ZnO}}/\lambda=0.1$) was obtained from the ZnO/sapphire-layered surface acoustic wave (SAW) device using this optimized ZnO film.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2006-04-30