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研究生： 謝秉文
Hsieh, Ping-Wen
論文名稱： 臨場觀測氧化鎵奈米線與鈦金屬之介面工程
In-Situ TEM Observations of Interface Engineering between Ti and Ga2O3
指導教授： 呂明諺
Lu, Ming-Yen
口試委員: 吳文偉
Wu, Wen-Wei
呂明霈
Lu, Ming-Pei
學位類別： 碩士
Master
系所名稱： 工學院 - 材料科學工程學系
Materials Science and Engineering
論文出版年： 2023
畢業學年度： 112
語文別： 中文
論文頁數： 86
中文關鍵詞： TEM臨場觀測 、氧化鎵奈米線 、鈦 、介面工程 、歐姆接觸 、擴散
外文關鍵詞： In-situ TEM, Ga2O3 nanowires, Titanium, Interface engineering, Ohmic contact, Diffusion
相關次數： 點閱：70  下載：0 
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    • 現今人類文明的進步已離不開電子元件的使用，元件所利用的半導體材料也不斷發展。考量到能源轉換效率，未來的功率元件中需要能替代目前材料的新選項，這類具有極寬能隙的半導體材料被稱為第四代半導體。氧化鎵(Ga2O3)為第四代半導體材料之一，因為其良好的材料特性及發展潛力受到矚目。金屬/半導體間的接觸為影響元件電性表現的關鍵因素，接觸金屬須於導通時達成歐姆接觸，確保低接觸電阻以降低功耗。針對Ga2O3，Ti為最常使用的接觸金屬，然而其形成歐姆接觸的介面反應與機制仍有爭議。本研究針對實際的Ga2O3奈米線元件進行電性分析，並利用電子顯微鏡分析Ti與Ga2O3奈米線間的介面工程，並透過穿透式電子顯微鏡臨場加熱並觀察反應的進行。
    第一部分的研究針對Au/Ti/Ga2O3奈米線元件進行電性量測，在退火處理後，可使元件之電流電壓曲線由整流特性轉變為歐姆接觸，TEM分析顯示其介面結構有鎵-鈦合金相生成。退火前，Ti/Ga2O3金半接面的能帶結構具有蕭特基能障，我們推測高溫退火後所形成的鎵-鈦合金相具有更低的功函數，使介面能形成低電阻之歐姆接觸。
    第二部分的研究，我們製備橫截面樣品臨場觀測Ti與Ga2O3奈米線於加熱下的介面反應，發現當加熱至400 °C以上時，Ti/Ga2O3介面將開始發生交互擴散，並於介面觀測到結晶相生成並朝著Ti金屬成長變厚。透過EDS分析、STEM原子影像及繞射點分析，確認該層材料為退火時所形成的鎵-鈦合金相。同時也發現加熱至500 °C以上，介面會因為元素擴散及高真空缺氧環境而累積缺陷，進而出現孔洞，出現孔洞後Ga2O3會隨之昇華分解。

    The progress of human civilization is inseparable from the use of electronic devices, and the semiconductor materials used in these devices continue to evolve. Considering energy conversion efficiency, we need new alternatives that can replace current materials for power electronics application. Materials with ultra-wide bandgap are referred to as the fourth generation of semiconductors. Ga2O3 is one of them and attracting attention due to its promising properties. For Ga2O3, titanium (Ti) is the most commonly used contact metal. However, the interfacial reaction and mechanism contributes to ohmic contact remain controversial. In this study, electrical analysis is conducted on prepared Ga2O3 NW devices. And we use in-situ TEM techniques to study the interface engineering between Ga2O3 and Ti under heating environments.
    In the first part of the research, electrical analysis is performed on fabricated Ga2O3 NW devices. After annealing, the IV characteristics of the device transformed from rectifying behavior to ohmic contact. TEM analysis confirms the formation of different phase at Ti/Ga2O3 interface.
    In the second part of the research, we use in-situ TEM heating and find out diffusion occurred between Ti and Ga2O3 when heated over 400 °C. A crystalline phase gradually formed at the interface. Using EDS analysis, STEM images and diffraction point analysis, it is confirmed that the formed material is a Ga-Ti alloy phase. It is believed that Ga-Ti alloy phase possess lower work function, which enabled the ohmic contact. Additionally, we find out heating above 500 °C led to accumulation of defects at interface due to the diffusion and high-vacuum environment. As a result, voids will appear and causes Ga2O3 to decompose.

    摘要 II Abstract III 致謝 IV 目錄 V 圖目錄 VII 表目錄 XI 第一章 緒論與文獻探討 1 1.1. 奈米材料介紹 1 1.2. 一維奈米材料 2 1.3. 半導體材料之演進 3 第一代半導體 3 第二代半導體 3 第三代半導體 3 第四代半導體 4 1.4. 氧化鎵奈米線 5 1.4.1 氧化鎵特點及應用 5 1.4.2 Ga2O3奈米線之合成方法 8 1.5. 金屬/半導體接觸 10 1.6. 氧化鎵與金屬接觸 13 1.7. 科肯德爾效應 (Kirkendall effect) 19 1.8. 臨場電子顯微鏡技術(In-situ TEM Observation) 21 1.9. 研究動機 24 第二章 實驗方法與儀器 25 2.1. 實驗架構與步驟 25 2.1.1 實驗步驟 25 2.1.2 Ga2O3奈米線合成 26 2.1.3 氮化矽薄膜臨場觀測試片之製備 27 2.1.4 臨場觀測樣品製備 28 2.1.5 TEM臨場觀測 29 2.1.6 元件製備及電性量測 30 2.2. 儀器介紹 32 2.2.1 三區加熱爐管 (Three Zone Furnace) 32 2.2.2 光學顯微鏡(Optical Microscope, OM) 33 2.2.3 X光繞射分析儀 (X-Ray Diffractometer, XRD) 34 2.2.4 電子束蒸鍍系統 (E-beam Evaporation System) 36 2.2.5 掃描式電子顯微鏡 (Scanning Electron Microscope, SEM) 37 2.2.6 聚焦離子束顯微鏡 (Focus ion beam Microscope, FIB) 38 2.2.7 穿透式電子顯微鏡 (Transmission Electron Microscope, TEM) 39 2.2.8 能量色散X-射線光譜 (Energy-Dispersive X-Ray Spectroscopy, EDS) 41 2.2.9 電子顯微鏡臨場加熱系統 42 2.2.10 DLP無光罩式曝光機 (DLP Maskless Exposure System) 43 2.2.11 電性量測系統 44 2.2.12 快速熱退火系統 (Rapid thermal Annealing, RTA) 45 第三章 結果與討論 46 3.1. Ga2O3奈米線特徵分析 46 3.1.1 Ga2O3奈米線之合成 46 3.1.2 橫截面方向觀測Ga2O3奈米線之結構 49 3.2. Ga2O3奈米線元件之電性分析 52 3.2.1 退火前之電性表現 52 3.2.2 退火後之電性 54 3.2.3 退火後元件之介面結構 56 3.3. 臨場觀測Ti/Ga2O3奈米線沿橫截面之介面反應 58 3.3.1 臨場觀測介面反應 58 3.3.2 反應介面分析 60 3.3.3 高溫下介面孔洞之生成 65 第四章 結論 75 第五章 未來展望 76 參考文獻 77

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