隨著現今科技的日益進步，電子產品為因應消費者的需求，必須朝向更高效能、體積更小的趨勢發展，三維立體封裝(3D IC)技術因而產生。因為內部尺寸更微縮小，線路生成之焦耳熱會比過去覆晶封裝來的高，而多層矽晶片的堆疊結構，熱源只能由外部晶片的散熱，因此會使得3D IC中的微小銲錫球產生一個較大的溫度梯度，可能會對銲錫內部造成可靠度上的問題。
本篇論文分別研究了銀原子在熱壓接和製程中的融熔銲錫以及固態時效中的銲錫在溫度梯度環境下的熱遷移行為，並且皆與等溫實驗相比較，可從中發現在有溫度梯度環境下之銲錫會有Ag3Sn介金屬化合物不對稱成長及聚集的現象。在經過熱遷移測試的融熔態銲錫內部中，試片冷端的Ag3Sn介金屬化合物的厚度會較熱端的Ag3Sn介金屬化合物來的厚很多;而經過熱遷移測試後的微小銲錫球中則發現Ag3Sn介金屬化合物的分布有趨向於喜歡累積於冷端的現象。我們從而推斷銀原子在溫度梯度下擴散至冷端的熱遷移行為可能是造成Ag3Sn介金屬化合物不對稱成長現象的主要原因，除此之外，文中也分別探討了融熔態及固態銲錫在溫度梯度下Ag3Sn介金屬化合物的成長機制，並進一步去計算出銀原子在融熔銲錫及固態銲錫內的Q*值(Heat of transport)分別為 +14.90 kJ/mole 和 +13.34 kJ/mole.

Three-dimensional integrated circuit (3DIC) technology has become the major trend of electronic packaging in microelectronic industry. To effectively remove heat in stacked ICs, the temperature gradient must be established across the chips. Furthermore, because of the trend of even higher device current density, the joule heating would be more serious and the temperature gradient across the solder joints is expected to be larger. In this study, we investigated thermomigration behavior in SnAg solders during liquid-state and solid-state aging process, respectively. As compared to isothermal process, the Ag and Ag3Sn IMCs were dissolved near the hot end and asymmetric growth of Ag3Sn on both interfaces was observed. We proposed that asymmetric growth of Ag3Sn behaviors was due to diffusion of Ag toward the cold side under a temperature gradient, and thereby leading abnormal Ag3Sn IMCs growth at cold side. In addition, the corresponding growth mechanism of Ag3Sn IMC caused by thermomigration of Ag was discussed and growth rate of Ag3Sn IMCs at cold side was found to linearly increase with solid-aging time under a temperature gradient. The intrinsic parameter, heat of transport (Q*) of Ag, in molten-state and solid-state solders was calculated as +14.90 kJ/mole and +13.34 kJ/mole, respectively.

Abstract i
摘要 ii
致謝 iii
Table of Content v
Table of Figures viii
List of Tables xv
Chapter 1 Introduction 1
Chapter 2 Literature Review 4
2.1 SnAg Alloy 4
2.2 Sn/Ag Interfacial Reaction 7
2.4 Electromigration 11
2.4.1Basic theory of electromigration 11
2.4.2Electromigration of Ag atoms 13
2.5 Thermomigration 17
2.5.1 Basic theory of thermomigration 17
2.5.2 Joule heating induced temperature gradient in Flip-chip solder 19
2.5.3 Thermomigration in SnPb solder joints 20
2.5.4 Thermomigration in Pb-free solder joints 22
2.6 Thermo-compression Bonding Technology 33
Chapter 3 Experiment 35
3.1 Thermomigration of Ag during reflow process 35
3.2 Thermomigration on Ag during solid-state aging process 36
3.3 Characterization methods 38
Chapter 4 Experimental Results 46
4.1 Thermomigration and isothermal test of Ag/SnAg/Ag sample during reflow process 46
4.1.1 Microstructural evolution of Ag/SnAg/Sn sample under temperature gradient 46
4.1.2 Microstructural evolution of Ag/SnAg/Sn sample under isothermal reflow 58
4.1.3 Finite element analysis on the temperature distribution in Ag/SnAg/Ag specimen 64
4.2 Thermomigration and isothermal test of 3D IC micro bump during solid-state aging process 68
Chapter 5 Discussions 82
5.1 The growth mechanism of Ag3Sn under a temperature gradient 82
5.1.1 Ag/SnAg/Ag sample during thermo-compression bonding (reflow) process 82
5.1.2 3D IC micro bumps during solid state aging process 91
5.2 Calculation of Heat of transport (Q*) of Ag 97
5.2.1 Q* of Ag in molten-state SnAg solder in Sn/SnAg/Sn sample 97
5.2.2 Q* of Ag in solid-state SnAg solder in 3D IC micro bump 98
Chapter 6 Conclusions 102
References 104

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