氧化鋅薄膜於表面聲波元件之應用

The Preparation of Single-Crystal ZnO Film and Its Application on Layered SAW Device

李政憲(Cheng-hsien Li)

指導教授 ： 劉代山

國立虎尾科技大學/電機資訊學院/光電與材料科技研究所/碩士(2005年)

https://doi.org/10.6827/NFU.2005.00010

摘要

本研究利用射頻鍍系統，在室溫下沉積高品質之氧化鋅薄膜，在室溫下沉積所獲得最佳氧化鋅薄膜的濺鍍條件為，射頻功率175 W，濺鍍壓力10 mTorr時，此時氧化鋅薄膜具有最佳的單晶結構與薄膜內應力 (Stress = -1.2×1010 dyn/cm2，此屬於壓應力)，接著加入氧分壓比例為30 ％參與濺鍍過程，可沉積出單晶及表面粗糙度 (Ra = 2.47 nm) 較佳的氧化鋅薄膜，然而由於氧原子參與濺鍍過程，使得薄膜內應力變大，此以快速熱退火處理來降低加入氧分壓參與濺鍍過程後所造成的薄膜內應力，結果顯示當在氧氣環境下，500 ℃熱處理後，薄膜結晶性及內應力獲得明顯改善 (Stress = 0.33×1010 dyn/cm2，此屬於張應力)，因此，利用這種方式所獲得之氧化鋅薄膜具備單晶結構、低薄膜內應力以及平整的表面粗糙度，適合用來製作層狀表面聲波元件的氧化鋅薄膜。
而在表面聲波元件製作上，因以純氬氣沉積之氧化鋅薄膜所造成的表面粗糙度過大，使得表面聲波訊號散射情況嚴重，因此在元件上並未量測到表面聲波訊號，但由於氧分壓 (30 %) 參與濺鍍過程使得氧化鋅薄膜之表面粗糙度獲得良好的改善，所以在中心頻率240 MHz處量測得明顯的聲波訊號，其表面波速為4800 m/s，Insertion Loss為 -18 dB。

關鍵字

non

並列摘要

Abstract
High quality piezoelectric ZnO thin film on room temperature by RF magnetron sputtering technique. The ZnO films on room temperature were deposited at r.f. power of 175 W, working pressure of 10 mTorr which have been excellent single-crystal structure and stress of films (Stress=-1.2×1010 dyn/cm2, this belong to compressive stress). Then O2-Ar mixture gas of 30 % was introduced as discharge and reaction gas to deposit ZnO films. The ZnO films have been excellent single-crystal structure and surface rough- ness (Ra= 2.47 nm). However, a incremental stress with tensile component parallel to c-axis was appeared due to the excess oxygen atoms filled in the interstitial site. The post-annealing treatment under oxygen environment had been found to improve stress of films due to oxygen atmosphere resulted. The experiment result shows associate post-annealing treatment at 500℃ under oxygen atmosphere environment which film crystallinity and stress have been apparent improvement. Therefore, this ZnO film is promising to fabricate a layered SAW device with single -crystal structure, lower stress and smooth surface roughness.
At the same time layered SAW device fabricated, the surface rough- ness of ZnO thin film deposited on pure argon ambient was larger and situ- ation of surface roughness lead to surface acoustic single dispersion. Therefore, the surface acoustic single had not measured yet. Due to surface roughness of ZnO thin film obtain appropriate improvement by deposited on oxygen partial pressure of 30 %, hence center frequency of 240 MHz corresponding to an acoustic velocity of 4800 m/s and insertion loss of -18 dB were measured.

並列關鍵字

non

參考文獻

[1] Hyoun Woo Kim, Nam Ho Kim, “Structural studies of room- temperature RF magnetron sputtered ZnO films under different RF powered conditions”, Materials Science and Engineering, B103 (2003) p.297-302

[2] Wen-Ting Chiou, Wan-Yu Wu, Jyh-Ming Ting, “Growth of single crystal ZnO nanowires using sputter deposition”, Diamond and Related Materials, vol.12 (2003) p.1841-1844

[3] Tsung-Tsong Wu, Wei-Shan Wang, “An experimental study on the ZnO/Sapphire layered surface acoustic wave device”, Journal of Applied Physics, vol.96, No.9 (2004) p.5249-5253

[4] Sheng-Yuan Chu, Walter Water, Jih-Tsang Liaw, “Influence of post- deposition annealing on the properties of ZnO films prepared by RF magnetron sputtering”, Journal of European Ceramic Society, vol.23 (2003) p.1593-1598

[5] N.W. Emanetoglu, C. Gorla, Y. Liu, S. Liang, Y. Lu, “Epitaxial ZnO piezoelectric thin films for SAW filters”, Materials Science in Semiconductor Processing, vol.2 (1999) p.247-252