近幾十年來，以半導體為中心的電子工業急速發展，半導體在現代科技中扮演相當重要的角色。由於打線接合技術能夠有效使微小晶片與外面電路做溝通，在後端封裝階段常被選擇。金線的使用已經廣泛且成熟，但考量金價急遽成長，遂尋找成本相對較低的銅線及銀線替代金線進行研究。銀線擁有良好的電性及機械性質，然尚未有銀線腐蝕及破壞模式相關研究，此研究主要探討銀鈀合金打線經高溫儲存與溫度循環測試下在腐蝕環境中的可靠度及破壞模式。高溫儲存測試的條件為將試片置於150°C烘箱中加溫500小時，溫度循環測試的條件則是在30分鐘的區間溫度由-55°C升至125°C並一共進行250次循環，而未經高溫儲存及溫度循環測試的試片則為對照組。所有試片隨後放入鹽水噴霧試驗機中進行鹽霧試驗，進行氯離子腐蝕測試。未經高溫儲存及溫度循環測試的試片經鹽水噴霧後，鋁板因加凡尼腐蝕，在48小時到60小時鹽水噴霧的區間造成打線裂縫延伸而脫落。高溫儲存測試試片在96小時到168小時區間鹽水噴霧後，破壞發生於銀鋁介金屬化合物生成處，裂縫使介金屬化合物分為上下兩層，上層介金屬化合物成分為Ag2Al及Ag3Al，下層介金屬化合物成分為Ag3Al2。溫度循環測試試片在192小時至240小時區間鹽水噴霧後打線脫落，在銀鋁交界處可能形成很薄的一層介金屬化合物及因溫度循環生成的微小裂縫，介金屬化合物及裂縫成為防止加凡尼腐蝕的原因，遂腐蝕從鋁板邊緣慢速往中心進行至裂縫完全延伸。

Semiconductor had become one of the most influential sectors among worldwide industries. Among the modern semiconductor IC packaging technologies, wire bonding is the most efficient technique for connecting Integrated Circuit (IC) to the motherboard. Gold wires have been widely utilized as the wire bonding material for decades. However, the rising gold price hindered further applications in electronic devices. The alternative wire bonding materials, such as Cu and Ag, have become potential candidates to replace Au wires. Ag was reported to have profound electrical and mechanical properties. Nevertheless, not many studies have focused on the halogen induced failure mechanism of the Ag alloy wires. In this study, we investigated the failure mechanism of Ag-4Pd alloy wire bonded on Al metallization under acceleration tests and corrosive environments. The samples were conducted with high temperature storage test (HTST) at 150°C for 500 hours and thermal cycle test (TCT) in the range of -55°C to 125°C per 30 minutes for 250 cycles as acceleration tests. The as-bonded samples and the samples after HTST and TCT were further set in the 5% NaCl salt spray chamber for chlorine corrosion test. The as-bonded encountered the fastest failure in the 48 hours to 60 hours interval of salt spray, which the failure at the Al metallization was caused by galvanic corrosion. The failure of the HTST samples occurred at the Ag-Al IMC layer and the bond detached from the bond pad in the 96 hours to 168 hours interval of salt spray. The crack propagated through the IMC layer and separated the IMC into two layers; the upper layer included Ag2Al and Ag3Al, and the lower layer was detected to be Ag3Al2. The ball bond detachment of the TCT samples took place in the 192 hours to 240 hours interval of salt spray. It is possible that a thin layer of IMC and slight cracks formed at the Ag-Al interface during the thermal cycle process act as a barrier to prevent the galvanic corrosion. As a result, the Al metallization was corroded from the edge to the center in a slow rate.

摘要 i
Abstract ii
致謝 iv
List of Figures vii
List of Tables x
Chapter 1 Introduction 1
Chapter 2 Literature Review 3
2-1 Bonding process 3
2-1-1 Thermosonic Bonding 4
2-1-2 Bond Pull Test (BPT) 5
2-2 Wire Bonding Materials and Evolution 7
2-2-1 Wire Bonding Materials 7
2-2-2 Ag and Ag Alloy Wires 9
2-2-3 Ag-Al system 10
2-2-4 Metallization Selection 13
2-3 Reliability Tests 14
2-3-1 High Temperature Storage Test 14
2-3-2 Thermal Cycle Test 16
2-4 Corrosion and Failure of the Wire Bonding 18
2-4-1 Failure of Au wires and Cu wires 18
2-4-2 Failure of Ag wires 20
2-5 Motivation 21
Chapter 3 Experimental Details 22
3-1 Specimen Preparation 22
3-2 Bond Pull Test (BPT) 26
3-3 High Temperature Storage Test 27
3-4 Thermal Cycle Test 28
3-5 Ssalt Spray 29
3-6 Microstructure Observation 30
Chapter 4 Results 31
4-1 Bond Pull Test (BPT) 31
4-1-1 As-bonded Samples 31
4-1-2 High Temperature Storage Test Samples 35
4-1-3 Thermal Cycle Test Samples 40
4.2 Morphology and Cross-section Observation 44
4-2-1 As-bonded Samples 44
4-2-2 High Temperature Storage Test Samples 47
4-2-3 Thermal Cycle Test Samples 54
4-3 Bond Failure after Salt Spray 53
4-4 Microstucture Observation of As-bonded samples after Salt Spray 54
4-4-1 Morphology 54
4-4-2 Cross-section and Crack Propagation 56
4-5 Microstucture Observation of samples post High Temperature Storage Test after Salt Spray 64
4-5-1 Morphology 64
4-5-2 Cross-section and Crack Propagation 65
4-6 Microstucture Observation of samples post Thermal Cycle Test after Salt Spray 72
4-6-1 Morphology 72
4-6-2 Cross-section and Crack Propagation 73
Chapter 5 Discussion 79
5-1 Failure Mechanism of the As-bonded samples after salt spray 79
5-2 Failure Mechanism of samples post High Temperature Storage Test after salt spray 83
5-2-1 The Growth of the IMCs 83
5-2-2 Failure Mechanism and Crack Propagation 85
5-3 Failure Mechanism samples post Thermal Cycle Test after salt spray 88
5-4 Comparison between As-bonded, HTS and TC Samples 91
Chapter 6 Conclusions 94
Reference 96

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