氧化銦鎵鋅薄膜之結晶性探討

Investigation on structural characteristics of InGaZnO thin films

黎駿樺(Chun-Hua Li)

指導教授 ： 高慧玲

中原大學/電機資訊學院/電子工程研究所/碩士(2015年)

https://doi.org/10.6840/CYCU.2015.00523

摘要

平面顯示器對於大尺寸、高解析度及低耗電的需求越來越高，但以目前所使用的矽薄膜電晶體難以同時滿足所有需求。而近年來發展出以氧化銦鎵鋅(IGZO) 薄膜製成的薄膜電晶體，其具有高載子遷移率、低漏電流、高均勻度以及低成本等特點，可同時實現大尺寸、高解析度以及省電的平面顯示器。IGZO薄膜電晶體亦可在低溫下製成，可應用於可撓式基板，成為可撓式顯示器。由於IGZO薄膜電晶體具備諸多優點，因此具有很大的潛力能取代目前現有的矽薄膜電晶體。本論文致力於探討具c軸從優取向之結晶型IGZO (CAAC-IGZO)，而若以CAAC-IGZO製成薄膜電晶體除了具有以上特點之外，其電流開關比更遠大於非晶型IGZO，因此結晶型IGZO的製程條件是非常值得探討的。
　　本論文以自製IGZO4陶瓷靶材作為濺鍍源，使用RF磁控濺鍍系統成長IGZO薄膜，透過不同溫度、氧氣比例以及基板來分析IGZO薄膜結晶性的影響。由X光繞射分析結果發現於室溫下成長之IGZO薄膜皆為非晶結構，而當400 ℃成長之IGZO薄膜具有較強的c軸結晶，且其c軸結晶程度隨著氧氣比例上升而提升，若成長在具有ZnO緩衝層之IGZO擁有更佳的c軸從優取向的特性。從能量散射光譜(EDS) 可得知In：Ga：Zn元素比例，當氧氣比例為0%時，其原子比約為1：1.1：0.6，而將氧氣比例提升至20%時，比例則變成1：2：1.1原子比。而薄膜電性從霍爾量測分析得知，在氧氣比例0%、室溫成長之IGZO薄膜其載子遷移率為6.1 cm2/Vs、電阻率為3.82 × 10-1 Ω-cm。以氧氣比例0%、400℃成長之IGZO薄膜其載子遷移率為19.9 cm2/Vs，電阻率為4.5 × 10-3 Ω-cm。而當氧氣提升時， IGZO薄膜阻值急速上升。從不同的成長溫度、氧氣比例以及基板的變化，發現成長CAAC-IGZO薄膜需具備一定的成長溫度及氧氣環境，而成長在ZnO緩衝層上之IGZO薄膜，能更進一步提升IGZO薄膜的結晶特性。

關鍵字

氧化銦鎵鋅薄膜 ； c-軸 從優取向 ； 磁控濺鍍 ； 氧化鋅

並列摘要

The requirements for flat panel displays are big size, high resolution, and low power consumption, yet the current technology of silicon-based thin film transistors (TFTs) are hard to satisfy all the requirements. Recently, the Indium-Gallium-Zinc-Oxide (IGZO) has been developed as channel in the thin film transistors. It has several merits such as high mobility, low off-current, high uniform, and low cost, which can in future to realize the commercial requirements. In addition, the process temperature of IGZO is low, and is possible to be applied on the flexible displays. Therefore, IGZO TFTs has potential to replace the traditional Si-based TFTs due to the above mentioned advantages. In this research, it has devoted to the study of C-axis Aligned Crystal (CAAC)　IGZO thin film, which has been reported and expected to have larger carrier mobility and extremely huge on-off ratio, compared with amorphous IGZO TFTs.
　　In this study, self-made IGZO4 ceramic target was used as sputtering source and IGZO thin films were grown using RF magnetron sputtering, to investigate the effects of growth temperature, oxygen contents, substrates on the structural characteristics of IGZO. Amorphous IGZO thin films were obtained at room temperature deposition; when deposited temperature increased to 400℃, the films become textured with c-axis oriented to substrate normal. The degree of the c-axis alignment can be increase by increasing oxygen content in sputtering gas, and also can be enhanced using Zinc Oxide (ZnO) buffer layer. The Indium, Gallium and Zinc atomic composition were investigated by Energy Dispersive Spectroscopy (EDS) with the atomic ratio of 1: 1.1 : 0.6 at 0% oxygen content, and 1 : 2 : 1.1 at 20% oxygen. Moreover, the electron mobility of IGZO thin films prepared in 0% oxygen and 400℃ deposition temperature reached to 19.9 cm2/Vs and the resistivity was decreased to 4.5 × 10-3 Ω-cm, as compared to 6.1 cm2/Vs and 3.82 × 10-1 Ω-cm, respectively, grown at room temperature. However, as the oxygen increases, the film resistivity increases substantially and can hardly be measured by Hall measurement system. The results of temperature effect, oxygen effect, and substrate effect, in this study indicated that the CAAC-IGZO should be formed under certain temperature and oxygen ratio, and in addition, using ZnO to be buffer layer can enhance the CAAC structure.

並列關鍵字

IGZO thin film ； C-axis aligned crystal ； magnetron sputtering ； ZnO

參考文獻

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