臺灣博碩士論文加值系統

近年來，微型發光二極體已逐漸成為極具商業潛力的元件，整合多樣功能性模組可應用於微影像顯示、微投影器、無光罩微影（Mask-free Photolithography）、光驅基因工程（Optogenetics）等領域。而本研究以開發圖像顯示用單石化（Monolithic）微型發光二極體（LED）陣列及其相關製程技術為目的，研製藍光微型LED 陣列，其重點在於克服因微型化所衍生之電阻與邊緣效應，抑制陣列畫素間之光互擾（Optical Crosstalk），並提升光萃取效率與改善散熱而引入的覆晶鍵合技術，皆為了尋求製程技術的精進以提升陣列元件之畫素良率與均勻度。最終實現一覆晶式64 × 64 之行列選址式（Row-Column-Addressed）微型LED陣列，其在100 uA (25 A/cm2) 下之啟動電壓為2.89 V，逆偏漏電流在-5 V之下為41.62 pA，光輸出功率在電流100 μA (25 A/cm2)、20 mA (5 kA/cm2)下可各達9.5 μW、0.42 mW。
由於藍寶石基板的低熱傳導性質及絕緣特性，覆晶技術對陣列元件有絕對助益，更可使微型LED 陣列作為多用途基底，提升產品效益。考量未來主流應用於高密度陣列畫素與大陣列尺寸，本研究使用銦凸塊為起點，建立高6 μm銦凸塊製程技術，於適當蒸鍍參數下，歸納出凸塊面積與高度之關係；並發展出適當之覆晶鍵合、底填程序及參數，且以串聯迴路之測試結構確認接合良率可達100 %，單點接合電阻為0.3 Ω，最後加入底填技術加強覆晶類型元件。以此研究成果為根基，未來將實現高畫素陣列，提升產品水平，銜接漸趨成長之可攜式微型投影市場，拓展LED 產值。

Recently, the micro-light-emitting diode has become a potential commercial device, which is integrated with functional module for widely applications, such as micro-display, micro-projector, mask-free photolithography, and optogenetics. In this research, a monolithic 450 nm GaN-based 64 × 64 micro-light-emitting diode arrays (μLEDA) with flip-chip bonding is demonstrated. To realize a high-quality μLEDA, this research has to deal with issues raised by area shrinkage and arrayed emitters. Area shrinkage results in increased series resistance and enhanced perimeter effect, while arrayed emitters result in optical crosstalk. Furthermore, the flip-chip boning technology is introduced for enhancing the extraction efficiency and improving heat dissipation. Underfilling is also added to the process to improve the stability of the devices. We delve into these problems and find appropriate countermeasures to raise the yield and uniformity of the μLEDA. The operation voltage at 100 μA (25 A/cm2) and leakage current at -5 V are 2.89 V and 41.62 pA, respectively. And the output power at 100 μA (25 A/cm2) and 20 mA (5 kA/cm2) could be achieved to 9.5 μW and 0.42 mW, respectively.
In order to develop applications of active-matrix of μLEDA in the future, the flip-chip bonding technology must be investigated. In this thesis, we evaporated 6 μm-thick indium bumps and induced the relationship between the bump area and height. The bonding process is optimized by varying bonding force, temperature and time. The 120 × 120 indium bumps array is fabricated, which includes the daisy chains design for examining each of contact resistance is about 0.3 Ω and the yield is up to 100%.
In summary, 450 nm GaN-based 64 × 64 μLEDA with flip chip bonding is demonstrated in this thesis. We believed that these technologies play an important role to make μLEDA be a potential candidate for portable micro-projector with lowest power consumption.

中文摘要.................................................I
ABSTRACT...............................................II
誌謝..................................................III
CONTENTS...............................................IV
LIST OF FIGURES........................................VI
LIST OF TABLES..........................................X
Chapter 1. Introduction.................................1
1-1 Development of III-nitride-based micro light emitting diodes..................................................1
1-2 Flip-chip technology................................3
1-3 Research motivation and purpose.....................4
Chapter 2. Backgrounds..................................7
2-1 Light emitting diode basis: electrical properties...7
2-2 Light emitting diode basis: optical properties......9
2-3 Theory of current spreading layer..................10
2-4 Flip-chip packaging basis..........................11
2-5 Daisy chain testing................................14
2-6 Characterization instruments.......................15
2-6-1 Current-voltage (I-V) characteristic measurement system.................................................15
2-6-2 Electroluminescence (EL) measurement system......16
2-6-3 Light output power-current (L-I) measurement.....17
2-7-4 Divergence angle measurement system..............19
Chapter 3. μLEDA Device Structure and Fabrications.....21
3-1 Epitaxial structure design concept.................21
3-2 The design of Masks................................21
3-3 Experiment process of 64 × 64 μLEDA................24
3-4 Experimental process of daisy chain test...........33
Chapter 4. Characteristic of micro-LED array and investigation of indium bump...........................37
4-1 Passive matrix of 64 × 64 blue micro-LED array.....37
4-1-1 I-V characteristics analysis of blue μLEDA.......40
4-1-2 Electroluminescence (EL) spectrum of blue μLEDA..47
4-1-3 Light output power-current (L-I) of blue μLEDA...49
4-1-4 Divergence angle of blue μLEDA...................50
4-1-5 Demonstration....................................51
4-2 Indium bump investigation for flip chip bonding....51
4-2-1 Relation between the indium bump area and height.52
4-2-2 The underfill test...............................55
4-2-3 The bonding condition and resistance test........56
Chapter 5. Conclusions.................................63
References.............................................64

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