氧化鋅成長在藍寶石基板之表面聲波元件特性研究

Abstract

射頻元件因訊號是中高頻段的電磁波，因此訊號可以無線傳播，表面聲波元件就是未來有機會可以取代一般直流訊號傳遞的各項偵檢器，它適合在危險的環境下偵測，並且能夠達到遠距離傳輸訊號。 本研究探討非極化氧化鋅薄膜成長在M面藍寶石基板上及其表面聲波元件特性，氧化鋅薄膜是利用RF磁控濺鍍法沉積薄薄地低溫緩衝層後，再加高溫度繼續濺鍍主要的氧化鋅來達到具有磊晶品質的薄膜，結構分析是利用同步輻射研究中心BL-17B的六環繞射儀做XRD掃描，薄膜壓電特性是利用掃描探針顯微術，並且搭配訊號產生器與鎖相放大器進行量測，接著利用黃光微影製程製作成表面聲波元件，並且使用網路分析儀量測S參數探討其元件特性。 因為氧化鋅在極化軸有較大的壓電響應，很明顯地觀察出聲波在ZnO[0002]方向傳遞的插件損耗-12dB，ZnO[1120]方向則是-30dB，速度分別為6269 m/s和3944 m/s。

In this study, surface acoustic wave (SAW) devices is provided with wireless and remote transport signal. It has potential for development in all kind of sensor, including gas, pressure, bio…etc. That is suitable for using in dangerous environments. Utilizing IDT/ZnO/buffer layer/sapphire structure is fabricated SAW Devices, the high vacuum RF magnetron sputtering system grown of low temperature buffer layer between the main ZnO layer make epitaxial piezoelectric film ZnO onto M-plane sapphire. The structure orientation and crystalline properties of the ZnO layer is evaluated by X-ray diffraction (XRD) on BL-17B in NSRRC. The surface roughness and piezoelectric properties of ZnO/sapphire films are observed by atomic force microscopy (AFM) with lock-in Amplifier and generator to measurement. After the ZnO epi-layer were deposited on sapphire, Au layer will deposition onto the ZnO using the DC sputter system, and the interdigital transducers (IDTs) product by photolithography to manufacture SAW device. The S-parameter of SAW device is measured by network analyzer in NDL. The phase velocity of the acoustic wave along ZnO[0002] and ZnO[1120] are 6269 m/s and 3944 m/s ; the insertion loss are -12 dB and -30 dB respectively.