氧化銦鎵鋅薄膜電晶體，因同時具備優異的薄膜均勻度與高載子移動率使其在未來顯示器主動陣列上的應用極具潛力，而氧化銦鎵鋅的高透明度更使得全透明積體電路與顯示器的開發成為可能。然而以n-type半導體材料而言，一般bottom-gate top-contact的元件因源/汲極電極覆蓋在通道之上，當施加閘極電壓時，電子會由半導體下表面開始累積形成通道 ，當閘極電壓極小時，由於通道極靠近介電層一側，此時電極與電子通道間，會有一層未累積電子較低濃度之n-type半導體層，變成電流路徑上多餘的串聯電阻，使得驅動電流下降。為了克服此問題，本論文將以調變結構，使電極能在通道由空乏進入累積之初，立即接觸此電子累積層，減少電流路徑上的串聯電阻，改善此問題。
本研究主要以兩個部分做為探討，其中一種為通道條狀式結構，探討電極覆蓋的通道側邊對元件特性的影響，另外一種為bottom-contact結構，探討源/汲極電極接觸到通道下側對元件特性的影響。本實驗選擇氮化鉭當作金屬閘極的材料，再以氧化矽鉿當作閘極介電層的材料，搭配通道材料為氧化銦鎵鋅，最後以鈦當作源/汲極材料定義元件，完成氧化銦鎵鋅薄膜電晶體之製作。物性分析方面以X光繞射分析(XRD)與化學分析電子儀(XPS)分析氧化銦鎵鋅與氧化矽鉿薄膜。於元件特性比較上，通道條狀式四條之開關電流比為4.2×105，由IDS-VGS萃取出關閉電壓約為-0.94 V，次臨界擺幅為99 mV/decade，而通道中的載子遷移率為11.49 cm2V-1s-1。Bottom-contact之開關電流比為8.04×105，由IDS-VGS萃取出關閉電壓約為-0.66 V，次臨界擺幅為107 mV/decade，而通道中的載子遷移率為12.97 cm2V-1s-1。
由實驗結果顯示，條狀式通道結構與bottom-contact結構，確實可以減少路徑上的串聯電阻使得驅動電流提升，而在元件製程上不會增加成本，對於氧化銦鎵鋅此類累積態通道材料做為高驅動元件應用上極具參考價值。

Indium gallium zinc oxide (IGZO) thin-film-transistors (TFTs) with excellent film uniformity, high carrier mobility and high transparency have shown high potential for applications of active matrix arrays for future display. However, in the operation of n-type TFTs, electron accumulation starts from the interface between channel and gate dielectric and thickness vertically toward the S/D electrodes as gate bias increased, a weak accumulation layer might locate between the S/D electrodes and strong accumulation layer which results in a considerable series resistance in the current path and decreases the driving current, especially for cases with non-optimized channel thickness.
In this thesis, to overcome the problem, multiple channels and bottom-contact structures are used to increase the direct contact region of S/D electrodes and the strong accumulation layer at the lower surface of the channel. Tantalum nitride (TaN), hafnium silicon oxide (HfSiO), and Indium gallium zinc oxide (IGZO) are served as gate electrode, gate dielectric, and channel respectively. The S/D electrodes are defined by the evaporated titanium (Ti). The physical properties and compositions of IGZO and HfSiO films were examined by XRD and XPS analysis. The device with multiple channels has show improved electrical characteristics with Ion/Ioff ratio, off voltage, subthreshold swing, and mobility of 4.2×105, -0.94 V, 99 mV/decade, and 11.49 cm2V-1s-1, respectively, The device of bottom-contact structure has shown improved electrical characteristics with Ion/Ioff ratio, off voltage, subthreshold swing, and mobility of 8.04×105, -0.66 V, 107 mV/decade, and 12.97 cm2V-1s-1, respectively.
In summary, the experimental results revealed that both multiple channels and bottom-contact are able to decrease series resistance and increase driving current. The results can be a valuable reference for structure engineering of TFTs in the future.

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