本論文以磁控式射頻共濺鍍系統成長氧化銦鎵鋅薄膜與氧化銦鎵鋅鋁薄膜，除分析薄膜基本特性及隨時間變化外，並以標準黃光製程定義薄膜電晶體，將所研究之氧化銦鎵鋅薄膜與氧化銦鎵鋅鋁薄膜作為薄膜電晶體通道層應用。
薄膜電晶體作為開關元件被廣泛應用在主動式液晶顯示器與有機發光二極體顯示器中，一般以非晶矽與低溫多晶矽為通道層材料，但因其能隙較小易受到可見光影響產生光電流，因此在薄膜電晶體中，透明導電氧化物半導體的發展逐漸受到重視，氧化銦鎵鋅薄膜更是受到矚目。氧化銦鎵鋅為一透明氧化物，可減少可見光的影響，另外作為薄膜電晶體通道時，其場效載子移動率亦高於非晶矽通道層薄膜電晶體，因此在近年來被廣泛的研究與討論。在本研究中，利用磁控式射頻共濺鍍系統成長氧化銦鎵鋅薄膜，使用氧化銦、氧化鎵以及鋅金屬作為濺鍍靶材，個別調變濺鍍功率，研究最適合作為增強型薄膜電晶體通道層的銦、鎵、鋅的原子比例，成功製作具高場效移動率的增強型薄膜電晶體，在通道層之銦、鎵、鋅比例為3.5：1：2.7時，場效移動率可達68.5 cm2/V-s，次臨界擺幅為0.22 V/decade，電流開關比達7.0106以上。將此研究成果應用至可撓式基板(polyethylene terephthalate, PET)製作氧化銦鎵鋅軟性薄膜電晶體，並與一般市售氧化銦鎵鋅靶材比較，所使用之市售氧化銦鎵鋅單靶成份比之銦、鎵、鋅、氧 = 2：2：1：7。在常溫下以最適比例條件之氧化銦、氧化鎵、鋅三靶共濺鍍成長之氧化銦鎵鋅軟性薄膜電晶體，其場效移動率可達57.2 cm2/V-s，次臨界擺幅為0.23 V/decade，優於以市售氧化銦鎵鋅單靶所製作之氧化銦鎵鋅軟性薄膜電晶體，其場效移動率為15.3 cm2/V-s，次臨界擺幅為0.28 V/decade。然而氧化銦鎵鋅薄膜仍有薄膜中的氧不穩定的困擾，因此本研究提出以鋁金屬作為摻雜，以以磁控式射頻共濺鍍系統成長氧化銦鎵鋅鋁薄膜，藉由鋁3s軌域陽離子提供額外的傳導路徑，提昇薄膜特性，並且由於鋁與氧的鍵結較為穩定，增加薄膜氧的穩定度，因此在老化實驗中，氧化銦鎵鋅鋁薄膜電性穩定度高於氧化銦鎵鋅薄膜，其薄膜濃度與移動率變化率分別只有20.1%與2.4%。將所研究之氧化銦鎵鋅鋁薄膜作為通道層製作薄膜電晶體，其場效移動率更提昇至為158.1 cm2/V-s，次臨界擺幅為0.148 V/decade，放至於溫度40oC、濕度75%環境中，十天後場效移動率與次臨界擺幅之變化率為7.9%與14.8%。氧化銦鎵鋅鋁薄膜可藉由鋁-氧間較強的鍵結改善薄膜穩定性。氧化銦鎵鋅鋁薄膜具有高穩定特性表現，未來將可被應用至各種元件上。

In the research, the indium gallium zinc oxide (IGZO) films and the indium gallium zinc aluminum oxide (IGZAO) films were deposited using the magnetron radio frequency (RF) co-sputtering system. The electrical characteristics of the IGZO films and the IGZAO films were analyzed and investigated under various aging times. The thin-film transistors (TFTs) were patterned by using standard photolithography processes. The IGZO films and the IGZAO films were the channel layers and applied to the TFTs.
The TFTs becoming switches were widely used in active matrix liquid crystal display (AMLCD) and organic light emitted diode (OLED) display et.al. In general, amorphous silicon (a-Si) and low temperature polycrystal silicon (LTPS) which were as channel layers were used in the TFTs. However, a-Si and LTPS generated photocurrents by absorption of visible light duo to their narrow optical bandgap. Therefore, the transparent conducting oxide (TCO) semiconductors attracted more attentions in the TFTs, especially the IGZO films. The IGZO as channel of the TFTs was a TCO semiconductor and prevent from the photocurrent generating by the visible light. Moreover, the field-effect mobility of the IGZO TFTs was much higher than that of a-Si TFTs. For the reasons, the IGZO TFTs were widely investigated and discussed in a decade. Nowadays, in this research, the IGZO films was deposited using magnetron RF co-sputtering system with triple targets of In2O3, Ga¬2O3, and Zn. Optimization of the atomic ratio of In, Ga, and Zn to fabricate the channel layers for enhancement mode (E-mode) TFTs by modulating the individual sputtering power. The high field-effect mobility E-mode TFTs were successfully fabricated as the atomic ratio of In:Ga:Zn=3.5:1:2.7. The field-effect mobility, the subthreshold swing, and the on-to-off current ratio of the IGZO TFTs were respectively 68.5 cm2/V-s, 0.22 V/decade, and 7.0106. The above resulting IGZO channel layer was also used in the flexible TFTs fabricated on polyethylene terephthalate (PET) substrate. Compare the performances of the TFTs with the commercial single target (In:Ga:Zn:O=2:2:1:7), the TFTs with optimal atomic ratio IGZO channel obtained superior performances. The field-effect mobility, the subthreshold swing of the IGZO flexible TFTs using triple targets were 57.2 cm2/V-s and 0.23 V/decade better than that of the TFTs using single IGZO target were 15.3 cm2/V-s and 0.28 V/decade. However, the IGZO still suffered instability of oxygen in the IGZO films. Therefore, the IGZAO films deposited using the magnetron RF co-sputtering system with IGZO target and Al target, were proposed in this study. An extra carrier transport pathway could be provided by the 3s orbitals of Al cations to improve the electrical properties of the IGZO films. Moreover, oxygen instability in the IGZAO films could be further stabilized by the strong Al-O bonds. The electrical performances of the IGZAO films were stable than that of the IGZO films under various aging times. The electron concentration change and the electron mobility change of the IGZAO films were respectively 20.1% and 2.4%. The field-effect mobility and the subthreshold swing of the TFTs with the above resulting IGZAO channel layer were respectively 158.1 cm2/V-s and 0.148 mV/decade. The field-effect mobility change and the subthreshold swing change of the IGZAO TFTs were 7.9% and 14.8% under an air environment at 40oC temperature and 75% humidity. The improved stability of the IGZAO channel layer was attributed to the oxygen stabilization owing to the strong Al-O bonds. Consequently, the IGZAO films can be expected to be used in versatile devices for its high performance stability.

Chapter 1
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Chapter 2
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Chapter 3
[1] C. T. Lee, Y. H. Lin, M. M. Chang, and H. Y. Lee, “Investigation of amorphous indium gallium zinc oxide thin film transistors grown by triple-targets magnetron co-sputtering,” IEEE J. Disp. Technol., 10, 293 (2014).
[2] J. S. Park, T. W. Kim, D. Stryakhilev, J. S. Lee, S. G. An, Y. S. Pyo, D. B. Lee, Y. G. Mo, D. U. Jin, and H. K. Chung, “Flexible full color organic light-emitting diode display on polyimide plastic substrate driven by amorphous indium gallium zinc oxide thin-film transistors,” Appl. Phys. Lett., 95, 013503 (2009).

Chapter 4
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