摻雜鋁之氧化鋅濺鍍薄膜在草酸溶液中之電化學蝕刻研究

Electrochemical etching of Al-doped Zinc Oxide sputtered film in oxalic acid

張毓峰(Yu-Fong Chang)

指導教授 ： 林景崎

國立中央大學/工學院/機械工程學系/碩士(2011年)

摘要

本論文以濺鍍法製備摻鋁氧化鋅透明導電薄膜(AZO)，進而以電化學濕式蝕刻法來探討不同條件參數(如:蝕刻液濃度、蝕刻電位等)對此AZO薄膜之蝕刻速率與薄膜特性的影響。首先利用雙靶射頻磁控濺鍍設備於STN玻璃基板上濺鍍AZO薄膜。濺鍍時，工作背壓在5x10-2torr、基板溫度200℃、純鋁靶功率為100W、氧化鋅靶功率為100W時，濺鍍時間150分鐘可獲得最佳化之AZO薄膜。經場發射電子顯微鏡觀察，所得之AZO膜厚為650nm，由四點探針量測得知其電阻率為3.61x10-3 Ω-cm，XRD與XPS分析得知其結構為(002)結晶方向與化學組態為氧化鋅與三氧化二鋁，紫外光-可見光光譜分析儀量測顯示其可見光穿透率高於90%，原子力顯微鏡分析其表面平均粗糙度約為10.079 nm。
電化學蝕刻利用恆電位儀(RARC 2263)供應電源，工作電極為AZO薄膜(1x1 cm2)，相對電極為白金鈦網，參考電極為飽和甘汞電極，蝕刻液為草酸水溶液。實驗結果顯示：當草酸溶液濃度增加、蝕刻電位加大時，薄膜蝕刻速率會由34.1nm/min加快至39.2 nm/min。蝕刻後的薄膜其電阻率上升為5.19x10-3Ω-cm，可見光穿透率可高於85%，平均粗糙度為11.26nm。AZO薄膜的透明導電性在草酸溶液中經電化學蝕刻前、後沒有重大改變，因此草酸溶液將是AZO透明導電薄膜的優異電化學蝕刻劑。

關鍵字

草酸 ； 電化學蝕刻 ； 鋁摻雜氧化鋅 ； 動態極化

並列摘要

The purpose of this study is to prepare conductive transparent Al-doped ZnO films (AZO) by sputtering and to investigate their possible electrochemical etching process. Radio frequency (RF) magnetron sputter was used to prepare the AZO film on STN glass substrates. Resulting from the sputtering process, we obtained satisfactory AZO films (650 nm in thickness with electrical resistivity at 3.61×10-3Ω-cm and optical transmission higher than 90 %)　under the following optimal conditions: the working pressure at a vacuum of 5×10-2torr, with RF power at 100 W on pure Al target and also at ZnO target, and setting the substrate temperature at 200℃ for 150 min. The morphology of the films was examined by scanning electron microscopy (SEM), their crystal structure was analyzed by x-ray diffraction (XRD) and surface composition using x-ray photoelectron spectroscopy (XPS).
Electrochemical etching process on the AZO films was investigated in solution where the concentration of etching agents and etching potential were varied. The morphology, roughness of surface crystal structure and surface composition of the films before and after etching were examined by SEM, XRD and XPS. The electrochemical etching was conducted in a standard three-way testing cell where a specimen with AZO films is the working electrode, a platinum foil as the auxiliary electrode, and a saturated calomel electrode (SCE) equipped with Haber-Luggin capillary as the reference electrode. Potentiostatic etching was performed in the solution of oxalic acid by using a potentiostat (PARC 2263). The suitable average etching rate for the AZO films was at 34.1 nm/min which would increase to 39.2 nm/min with increasing the acid concentration and anodic potential in the process. After etching, the electric resistivity maintained almost unchanged (i.e., at 5.19x10-3Ω-cm), and only a slight decrease in optical transmission (decrease from 90 % to 85%). Surface roughness of the etched AZO films increased a little bit (i.e., from 10.079 nm to 11.26 nm). The slight decrease in optical transparency for the etched films may be ascribed to the little increase of the roughness.

並列關鍵字

oxalic acid ； Potentiodynamic polarization ； Al-doped zinc oxide ； Electrochemical etching

參考文獻

[9] 徐玄修,林永昇,殷宏林,謝哲偉, “生醫微流體晶片之製程平台”,儀器科技研究中心。

,崑山科技大學電機工程系, 民國98年。

[1] H. Sheng, N.W. Emanetoglu, S. Muthukumar, B.V. Yakshinskiy, S. Feng,

and Y.Lu, J. Electron Mater, Vol.32 (2003) 9

[11] R.W. Fauthauer, T. George, A. Ksendzov, and R.P. Vasquez, “Visible luminescence from silicon waters subjected to stain etches“, Appl. Phys. Lett., 60 (1992)995.