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研究生： 邱懷慶
Chiu, Huai-Ching
論文名稱： 氮化鎵藍光二極體之研製及應用表面處理改善其特性之研究
Fabrication and Characteristic Improvement of GaN Blue LED by Surface Treatment
指導教授： 洪茂峰
Houng, Mau-Phon
王永和
Wang, Yeong-Her
學位類別： 碩士
Master
系所名稱： 電機資訊學院 - 微電子工程研究所
Institute of Microelectronics
論文出版年： 2004
畢業學年度： 92
語文別： 英文
論文頁數： 87
中文關鍵詞： 電感耦合電漿蝕刻 、氮化鎵 、發光二極體
外文關鍵詞： light emitting diode, GaN, inductively coupled plasma
相關次數： 點閱：83  下載：14 
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    • 　　由於大多數氮化鎵系列發光二極體都成長在絕緣性的藍寶石基板上，使得元件的正負極皆在基板的上方。因此在本論文中，我們利用電感耦合電漿蝕刻技術來製作藍光二極體，並利用交流濺鍍系統沈積實驗過程中所需之薄膜。
    　　電感耦合電漿蝕刻的系統參數當中，我們由實驗過程可以發現：對氮化鎵的乾蝕刻而言，氯氣（Cl2）以及三氯化硼（BCl3）的混合氣體可以達到不錯的蝕刻效果。其中當氯氣比例為百分之九十的時候為最佳化的條件。另外，在工作壓力對蝕刻的影響方面，我們可以發現壓力大於15＊10-3托耳（torr）的時候，表面聚合物的累積會明顯增加，而且這將會影響到化學蝕刻反應以及蝕刻速率的穩定性。
    　　對透明導電層而言，表面處理是必須而且有效提高特性的方法。利用傳輸線模型以及歐傑電子光譜儀等分析我們可以發現在熱處理過後，透明導電層在歐姆特性、穿透率以及發光效率上皆有顯著的改善。

    　　Most GaN-based LEDs are grown on the insulated sapphire substrates and as a result, the p-pad and n-pad are both deposited on the top side of substrate. In this thesis, we use inductively coupled plasma (ICP) to fabricate blue LEDs and RF sputtering system to deposit thin films.
    　　Among parameters of ICP system, it is observed that the mixed gases of Cl2 and BCl3 are suitable for the GaN plasma etching. And based on our experiment, the optimal condition is obtained with the Cl2 ratio reaches 90%. Besides, the working pressure is another major parameter for ICP. It is found that when pressure is higher than 15 mtorr, it will increase the piling up of residuals on surface.
    　　As far as transparent conductive layer (TCL) is concerned, the surface treatment is essential and effective method to improve its characteristics. By TLM, AES depth profiles and other analysis we can find that electrical and optical performance of TCL are evidently improved by thermal treatment.

    Contents 摘要……………………………………………………………………I Abstract………………………………………………………III 誌謝……………………………………………………………V Contents.………………………………………………………VI Table captions.…………………………………………………IX Figure captions…………………………………………………X Chapter 1 Introduction.…………………………………………1 1.1 Background………………………………………………………1 1.2 Organization……………………………………………………3 Chapter 2 Theoretical Description for GaN LED…………4 2.1 GaN structure……………………………………………………4 2.1.1 Historical survey of GaN……………………………………………………4 2.1.2 Grown structure……………………………………………………4 2.1.3 The role of hydrogen in GaN……………………………………………5 2.1.4 Dopant passivation by hydrogen…………………………………….....6 2.2 GaN based LED……………………………………………………7 2.2.1 LED devices………………………………………………………7 2.2.2 Quantum efficiency……………………………………………8 2.2.3 Light extraction………………………………………………9 2.2.4 Current spreading and current blocking layers…………………………10 Chapter 3 The Parameters of ICP system for GaN etching…14 3.1 Comparison between wet and dry etching for III-V compounds………14 3.2 The plasma etching………………………………………………………16 3.2.1 Reactive ion etching (RIE) ………………………………………………18 3.2.2 High-density plasma etching…………………………………………18 3.3 Relations between ICP parameters and etching profiles……………………20 3.3.1 The principle of plasma chemistry…………………………………………20 3.3.2 Working pressure…………………………………………………….22 3.3.3 The substrate temperature……………………………………………..22 3.3.4 Other conditions………………………………………………….......23 Chapter 4 Fabrication of GaN LED……………………….….24 4.1 Overview of fabrication procedure……………………………………...24 4.1.1 Preparation of wafer……………………………………………..…...24 4.1.2 Wafer cleaning……………………………………………25 4.1.3 Define mesa by ICP etching………………………………25 4.1.4 Deposition of TCL……………………………………………………25 4.1.5 n-pad formation………………………………………………………26 4.1.6 p-pad deposition…………………………………………………………26 4.2 The metal-semiconductor contact……………………………………….27 4.2.1. The ohmic contact to n-GaN…………………………………………28 4.2.2. The ohmic contact to p-GaN…………………………………………29 4.3 The TCL for GaN LED………………………………………………………29 4.4 Equipments………………………………………………30 4.4.1 ICP system………………………………………………30 4.4.2 RF sputtering system…………………………………………………30 Chapter 5 Improvement of LED by Surface Treatment……32 5.1 Requirement of surface treatment………………………………………32 5.2 The transparent conductive layer………………………………...……...32 5.2.1 The Ni/Au oxidation mechanism…………………………33 5.3 Experimental results and discussion…………………… 35 5.3.1 The LED performance……………………………………35 5.3.2 TLM method……………………………………………………………36 5.3.3 Ohmic behavior…………………………………………………………37 5.3.4 The transmittance…………………………………………38 5.3.5 Inter-diffusion for TiN in the interface………………………39 Chapter 6 Conclusion and Future Work………………………41 6.1 Conclusion………………………………………………………41 6.2 Future work………42 References……………………………………………………….43 自傳………………………………………………………………87

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