氧氣控制、快速熱退火與其他元素摻雜對於銦鎵鋅氧薄膜電晶體的影響

Abstract

近年來，為了在薄膜電晶體有更好的特性進而讓其有更好的應用空間，已有許多專家及廠商投入新穎材料的研究。期望能在現有的非結晶矽、多晶矽和有機半導體找到可以在材料上對於其應用在電晶體上的電性和穩定性可以有更好的突破。氧化物半導體就是在這樣的氛圍下研發出來的，他具有大幅超越現有材料的電性極限，在製程難度上並沒有跟著提升，因此業界就因為氧化物半導體的研發而實現可攜式電子產品的目標。現在日常生活中隨處可見方便攜帶的電子產品像是手機、平板和筆電等，這些都已經離不開人們的日常生活。本論文就針對氧化物半導體中目前最好的材料—銦鎵鋅氧進行研究和討論。 氧化物半導體中，表現出不錯特性的銦鎵鋅氧自從在2004年被研究發展出來後，已經受到科學界和業界的關注，關於她的相關研究報導在這幾年陸陸續續的發表出來。即使如此，我們對於她的理解並不是很清楚，因為她本身是由三種氧化物分別是氧化鋅、氧化鎵和氧化銦所構成的。雖然她的製作方式不是很困難，在製程上在現有的沉積方式即可達到。但是我們對於她其中材料成分變化造成特性影響的機制不是非常清楚。所以本論文就是針對做為薄膜電晶體的新穎材料銦鎵鋅氧進行研究和相關的特性改變與改善。 本論文首先針對銦鎵鋅氧成分進行了解，知道材料比例對於其電性有很大的變化。因為我們的研究發現，通氧氣造成的基本特性和已知的文獻不進相同，而我們也把這個發現應用在薄膜電晶體的沉積上，製作出針對不同區域的主動層做特性上的最佳化。之後我們發現此材料在某種比例對於快速熱退火有很不一樣的現象發生，本來應該是比較偏半導體的運作在攝氏四百度一分鐘快速退火下可以表現出如果金屬一樣導體的特性。所以我們就把這個現象應用在銦鎵鋅氧自體電極的電晶體上，實現高透明度的薄膜電晶體。另外也針對快速熱退火造成的奇異現象進行深入研究，發現製程溫度和製程時間對於銦鎵鋅氧有很高的相依性。特別是氧元素的部分，會隨著不同方式的熱處理進行氧擴散和氧與其他元素化學鍵結的行為。鑒於銦鎵鋅氧本身是多元合金的特點，我們在研究中試著混入其他的金屬元素如鎂和鉬，發現鎂適合參雜在銦鎵鋅氧通道區，而鉬參雜可以應用在自身銦鎵鋅氧電極形成。根據不同的參雜元素，銦鎵鋅氧薄膜會產生迥然不同的電性表現，這非常適合我們在製作高同質性銦鎵鋅氧薄膜電晶體的構想，就是主動區和電極區都是由同一成分材料所構成。最後，我們將提出的快速熱退火和鉬元素參雜方法進行結合運用，發現在鉬的參雜下，只要三百度就可以有電極的行為產生。比起之前高溫有顯著的下降。此研究讓我們有可以在全低溫的情況下做出高特性薄膜電晶體的可能性，也有助了解銦鎵鋅氧內部的一些運作機制。 相較於之前研究課題，本論文最大特點為首次提出利用銦鎵鋅氧參雜其他元素如鎂和鉬。在不同參雜下，造成不同特性，然後利用這個結果針對主動區不同區域進行最佳化，實現銦鎵鋅氧有導體特性的可能。此兩項新穎想法預期可被其他科學家參考與使用，本論文主要的貢獻是對於銦鎵鋅氧薄膜電晶體在眾多不同目的與面向的研究中針對其中一塊領域，也就是材料利用不同方式對於自體改質進行簡單、初期的研究。

In recent years, numerous scientists and firms have worked to develop novel material research for greater performances and more applications in thin-film transistor (TFT) technology. They hope they can make a breakthrough in novel material development for improving transistor electrical performances and stability compared with conventional materials such as amorphous Si, poly Si, and organic materials. Thus, this paper proposes an oxide semiconductor. An oxide semiconductor has superior features, which exceed those of the well-known semiconductor in the TFT field. In addition, the process complexity does not become more difficult once it is introduced to the market. Therefore, the TFT community has the opportunity to achieve the objective of a compact and mobile electronic product because of the introduction of the oxide semiconductor. Novel electronic products such as smart phones and touch pads impact people’s daily life because they exhibit greater convenience compared with living without them. This dissertation examines, InGaZnO (IGZO), which is the ideal material for oxide semiconductors. IGZO, which is the ideal material for an oxide semiconductor, has attracted interest from scientists and industries since its discovery in 2004. Numerous papers and reports on IGZO have been published in the last decade. However, a clear understanding of this novel material is scant because the components have indium oxide, gallium oxide, and zinc oxide, which increase its complexity. Although device fabrication achieved using conventional deposition is not difficult, the relationship between the composition and the performance has yet to be fully elucidated. This dissertation focuses on IGZO and the improvement in electrical performance. This dissertation first reports the realization of the effect of IGZO composition. The electrical parameters are largely influenced by changes in the composition. The effect of the oxygen ratio was determined by adjusting the oxygen flow in this study, which is an approach that differs from those in previous reports. Furthermore, the IGZO thin film was optimized during TFT fabrication by using this result. Afterward, IGZO was found to exert special results through rapid thermal annealing (RTA). An oxide semiconductor exhibits metal behavior through appropriate RTA treatment. Thus, this result was used in homogenous IGZO-TFT fabrication to achieve a highly transparent device. Moreover, this paper systemically investigates this result, and found that the RTA process transformed the oxygen bonding states of IGZO, making it behave as a conductor. In addition, the results indicated that RTA treatment influences only the surface region of the IGZO layer. The oxygen-bonding state in IGZO is essential for determining the electrical performance of IGZO-TFTs. Because IGZO is a multi-component material, this paper investigates the effect of element doping by introducing other elements such as Mg and Mo during thin film deposition. The performances were influenced by doping different elements. Mg doping is benefit for channel performance and reliability improvement and Mo shows the possibility of IGZO electrodes formation. This result revealed the possibility of a homogenous TFT that shares the same materials in the electrode and active layer. Finally, the combination of RTA and Mo doping for IGZO electrode formation was investigated; the finding revealed that IGZO exhibits conductive behavior when Mo is doped and treated using RTA, which largely reduces the process temperature. This indicates the possibility of high-performance IGZO-TFTs fabrication at room temperature, and helps elucidate the mechanism of IGZO regarding its composition. Compared with previous research, this dissertation first introduces the optimization of IGZO through selective modulation induced by the channel region and the possibility of IGZO conductor. These novel concepts can act as a reference, and can be used by other researchers. The contribution of this dissertation is in changing IGZO properties by using different methods, which is the main issue, and it also presents a comparison of all the information regarding oxide semiconductors.