打線是一種被廣泛應用在電子產品中的接合技術，主要於導通訊號，由於鋁金屬有著導電性佳、便宜及質地軟的特性，鋁打線很有潛力能取代金線以及銅線。本研究即是研究接合在銅基板上、直徑為2 mil的鋁線在攝氏150度、2 和 7×10^4 A/cm^2電遷移條件下的微結構改變及破壞機制。經實驗發現電阻會先下降而後上升，直到鋁線熔毀。且雖然電遷移後介金屬化合物(IMC)的成長並不明顯，但當電子流從Cu流向Al時，焊點介面的IMC厚度通常比相反電子流流向的IMC厚。並且實驗後還發現鋁線內的晶粒大幅成長而形成竹狀結構，且在鋁線表面靠電子流從Cu流向Al的一側有類似竹節的形狀產生。此次研究將會針對電遷移實驗後試片造成電阻、接點微結構及鋁線表面形貌的機制進行探討。

Wire bonding technology has been utilized in semiconductor packaging industry for electrical connections. Due to low cost, good conductivity, softness and the ability to be bonded under room temperature, Al wire bonding has been considered as a potential candidate to replace the Au and Cu. This study investigates microstructural evolution and failure mechanisms of 2 mil Al wedge-wedge bonding bonded on Cu pad under current density of 2 and 7×10^4 A/cm^2 at 150 ℃. During electromigration tests, resistance decreased first and then increased till wires failed. Though the growth of intermetallic compounds (IMC) at the bonded interface change insignificantly after electromigration tests, the thickness of IMCs at the bonding interface where electron flowed form Cu to Al is usually larger than that at the interface where electron flowed in the opposite direction. Furthermore, considerable grain growth, bamboo structure and bamboo nodes were observed in Al wires. The corresponding mechanism of IMC growth at the interface, resistance change and as well as the formation of bamboo nodes were discussed.

摘要 I
Abstract III
致謝 IV
List of Figures IX
List of Tables XVIII
Chapter 1 Introduction 1
Chapter 2 Literature Review 3
2-1 Wire Bonding Techniques 3
2-1-1 Thermosonic Ball/ Wedge Bonding 5
2-1-2 Ultrasonic Wedge/ Wedge Bonding 7
2-2 Bonding Parameter 8
2-2-1 Ultrasonic Power 9
2-2-2 Bonding Force 11
2-2-3 Bonding Time 12
2-3 Materials and Interface Microstructure Evolution 12
2-3-1 Materials of wires and pads 13
2-3-2 Al-Cu System 17
2-4 Electromigration 22
2-4-1 Electromigration in Metals 23
2-4-2 Joule Heating Effect 26
2-4-3 Polarity Effect 28
2-4-4 EM in Wire Bonding 31
Chapter 3 Experimental Details 32
3-1 Specimen Preparation 32
3-2 Bond Pull Test 34
3-3 Electromigration Test 35
3-4 Joule Heating Effect 38
3-5 ANSYS Simulation 39
Chapter 4 Experimental Results 41
4-1 Bond Pull Test 41
4-2 As-received Samples 42
4-2-1 As-received Wires 42
4-2-2 As-received Bonds 42
4-3 Joule Heating Measurement 45
4-4 Resistance versus Time (RVT) Curves 47
4-5 Simulation 49
4-5-1 Samples Under 2×10^4 A/cm^2 Current Density 49
4-5-2 Samples Under 7×10^4 A/cm^2 Current Density 53
4-6 Microstructure of Bonds after EM Tests 57
4-6-1 Sample No. 1 57
4-6-2 Sample No. 2 61
4-6-3 Sample No. 4 65
4-6-4 Sample No. 5 70
4-6-5 Sample No. 6 73
4-7 Outward Appearance of Wires after EM Tests 77
4-8 Microstructure of Wires after EM Tests 87
4-8-1 Sample No. 1 87
4-8-2 Sample No. 4 89
4-8-3 Sample No. 5 91
4-9 Isothermal Samples 93
4-9-1 Wires Annealed at 370 ℃ 93
4-9-2 Bonds Annealed at 170 ℃ 97
Chapter 5 Discussion 100
5-1 Resistance Change during EM Tests 100
5-2 Appearance Change of wires 107
5-3 IMC Evolution 114
Chapter 6 Conclusions 117
Reference 119

[1] A.Engineering, “Wire bonding using copper wire,” 2008.
[2] T. K.Omiyama, Y. C.Honan, J. O.Nuki, M. K.Oizumi, andT. S.Higemura, “High-Temperature Thick Al Wire Bonding Technology for High-Power Modules High-Temperature Thick Al Wire Bonding Technology for High-Power Modules Emitter electrode Gate electrode,” vol. 5030.
[3] A.Wire, “Development of High-Reliability Thick Al-Mg 2 Si Wire Bonds for High-Power Modules,” no. June, pp. 279–282, 2012.
[4] H.Xu et al., “Intermetallics Intermetallic phase transformations in Au e Al wire bonds,” vol. 19, pp. 1808–1816, 2011.
[5] H. T.Orchard andA. L.Greer, “Electromigration Effects on Intermetallic Growth at Wire-Bond Interfaces,” vol. 35, no. 11, pp. 1961–1968, 2006.
[6] E.Zin et al., “Mechanism of Electromigration in Au / Al Wirebond and its Effects Cu,” pp. 943–947, 2009.
[7] F. W.Wulff, C. D.Breach, D.Stephan, S.Saraswati, andK. J.Dittmer, “Characterisation of intermetallic growth in copper and gold ball bonds on aluminium metallization,” Proc. 6th Electron. Packag. Technol. Conf. (EPTC 2004) (IEEE Cat. No.04EX971), pp. 348–353, 2004.
[8] B.Yytanyik-yeetaninfienoncom andK. S.Sim, “Effect of Cu and PdCu wire bonding on bond pad splash,” Electron. Lett., vol. 50, pp. 8–11, 2014.
[9] B.Chylak, J.Ling, H.Clauberg, T.Thieme, F.Washington, andA. D.Gmbh, “Next Generation Nickel-Based Bond Pads Enable Copper Wire Bonding Bond Pad Design for Cu wire bonding.”
[10] H.Ji, M.Li, C.Wang, J.Guan, andH.Sur, “Evolution of the bond interface during ultrasonic Al – Si wire wedge bonding process,” vol. 182, pp. 202–206, 2007.
[11] M.Hook, D.Xu, andM.Mayer, “Electromigration testing of wire bonds,” pp. 1–6, 2014.
[12] O.Mokhtari et al., “Investigation of Formation and Growth Behavior of Cu / Al Intermetallic Compounds during Isothermal Aging,” pp. 1–7, 2014.
[13] M.Ciappa, “Selected failure mechanisms of modern power modules,” vol. 42, pp. 653–667, 2002.
[14] S.Ramminger, P.Ttirkes, andG.Wachutka, “Crack Mechanism in Wire Bonding Joints,” Microelectron. Reliab., vol. 38, pp. 1301–1305, 1998.
[15] H.Xu, C.Liu, V.V.Silberschmidt, andZ.Chen, “Growth of intermetallic compounds in thermosonic copper wire bonding on aluminum metallization,” J. Electron. Mater., vol. 39, no. 1, pp. 124–131, 2010.
[16] H.Xu, C.Liu, V.V.Silberschmidt, S. S.Pramana, T. J.White, andZ.Chen, “A re-examination of the mechanism of thermosonic copper ball bonding on aluminium metallization pads,” Scr. Mater., vol. 61, no. 2, pp. 165–168, 2009.
[17] H.Xu et al., “Behavior of aluminum oxide , intermetallics and voids in Cu – Al wire bonds,” vol. 59, pp. 5661–5673, 2011.
[18] S.Wang, L.Gao, andM.Li, “application on bonding,” pp. 789–793, 2013.
[19] H. A.Mustain, A. B.Lostetter, andW. D.Brown, “Evaluation of Gold and Aluminum Wire Bond Performance for High Temperature ( 500 ° C ) Silicon Carbide ( SiC ) Power Modules,” pp. 1623–1628, 2005.
[20] P. S.Chauhan, A.Choubey, Z.Zhong, andM. G.Pecht, Copper Wire Bonding. .
[21] Y.Long, J.Twiefel, andJ.Wallaschek, “Journal of Materials Processing Technology A review on the mechanisms of ultrasonic wedge-wedge bonding,” J. Mater. Process. Tech., vol. 245, pp. 241–258, 2017.
[22] H. O.Willrich, “Application of Ultrasonic Waves,” Weld. J., vol. 18(1), pp. 61–66, 1950.
[23] D.HPC., “Ultrasonic welding,” vol. 3, no. 4, pp. 190–196, 1965.
[24] K. C.Joshi, “The formation of ultrasonic bonds between metals,” Weld. J., vol. 50, no. 1971, p. 840, 1971.
[25] U.High, “Observation of Ultrasonic Al-Si Wire Wedge Bond Interface Using High Resolution Transmission Electron Microscope,” 2007, vol. 0, pp. 2–5.
[26] J.Ho, C.Chen, andC.Wang, “Thin film thermal sensor for real time measurement of contact temperature during ultrasonic wire bonding process,” vol. 111, pp. 188–195, 2004.
[27] B.Lasgesecker, “Effects of ultrasound on deformation characteristics of metals,” IEEE Trans. Sonics Ultrason., vol. 13, no. 1, 1966.
[28] A.O., Ultrasound in liquid and solid metals. CRC Press, 1994.
[29] C. D.Breach andF. W.Wulff, “Microelectronics Reliability A brief review of selected aspects of the materials science of ball bonding,” Microelectron. Reliab., vol. 50, no. 1, pp. 1–20, 2010.
[30] J.Qi, N. C.Hung, M.Li, andD.Liu, “Effects of process parameters on bondability in ultrasonic ball bonding,” vol. 54, pp. 293–297, 2006.
[31] T. K.Lee, C. D.Breach, W. L.Chong, andD.Optimization, “Comparsion of Au / Al and Cu / Al in Wirebonding Assembly and Reliability,” in Microsystems, Packaging, Assembly and Circuits Technology Conference, 2011, pp. 234–237.
[32] H.Chu, J.Hu, L.Jin, andY.Jie, “Defect Analysis of Copper Ball Bonding,” in ICEPT-HDP 2008, 2008, no. 10, pp. 8–10.
[33] R.Gao andL.Han, “Experimental studies of bonding pressure on heavyaluminum wire bonding strength,” Piezoelectectr. Acoustoopt, vol. 29, no. 3, p. 2007, 2007.
[34] J.Tsujino, H.Yoshihara, K.Kamimoto, andY.Osada, “Welding characteristics and temperature rise of high frequency and complex vibration ultrasonic wire bonding,” Ultrasonics, vol. 36, no. 1–5, pp. 59–65, 1998.
[35] G.Hu, “Comparison of copper, silver and gold wire bonding on interconnect metallization,” in ICEPT-HDP 2012 Proceedings - 2012 13th International Conference on Electronic Packaging Technology and High Density Packaging, 2012, pp. 529–533.
[36] T. S.Epithelium et al., Silver Metallization: Stability and Reliability. Springer-Verlag London, 2009.
[37] L. J.Kai et al., “Silver alloy wire bonding,” Proc. - Electron. Components Technol. Conf., no. February, pp. 1163–1168, 2012.
[38] D. R.Smith andF. R.Fickett, “Low-Temperature Properties of Silver,” J. Res. Natl. Inst. Stand. Technol., vol. 100, no. 2, p. 119, 1995.
[39] N. J.Noolu, N. M.Murdeshwar, K. J.Ely, J. C.Lippold, andW. a.Baeslack, “Degradation and failure mechanisms in thermally exposed Au–Al ball bonds,” J. Mater. Res., vol. 19, no. 5, pp. 1374–1386, 2004.
[40] H.Xu et al., “New mechanisms of void growth in Au-Al wire bonds: Volumetric shrinkage and intermetallic oxidation,” Scr. Mater., vol. 65, no. 7, pp. 642–645, 2011.
[41] M.Drozdov, G.Gur, Z.Atzmon, andW. D.Kaplan, “Detailed investigation of ultrasonic Al-Cu wire-bonds: II. Microstructural evolution during annealing,” J. Mater. Sci., vol. 43, no. 18, pp. 6038–6048, 2008.
[42] H. J.Kim et al., “Effects of Cu/Al intermetallic compound (IMC) on copper wire and aluminum pad bondability,” in Advances in Electronic Materials and Packaging 2001, 2001, pp. 44–51.
[43] H.Clauberg, P.Backus, andB.Chylak, “Nickel-palladium bond pads for copper wire bonding,” Microelectron. Reliab., vol. 51, no. 1, pp. 75–80, 2011.
[44] P.Liu, L.Tong, J.Wang, L.Shi, andH.Tang, “Challenges and developments of copper wire bonding technology,” Microelectronics Reliability, vol. 52, no. 6. pp. 1092–1098, 2012.
[45] R.Schmidt, C.König, andP.Prenosil, “Novel wire bond material for advanced power module packages,” Microelectron. Reliab., vol. 52, no. 9–10, pp. 2283–2288, 2012.
[46] A.Shah, M.Mayer, Y. N.Zhou, S. J.Hong, andJ. T.Moon, “Low-stress thermosonic copper ball bonding,” IEEE Trans. Electron. Packag. Manuf., vol. 32, no. 3, pp. 176–184, 2009.
[47] J.Premkumar, B. S.Kumar, M.Madhu, M.Sivakumar, K. Y. J.Song, andY. M.Wong, “Key factors in Cu wire bonding reliability: Remnant aluminum and Cu/Al IMC thickness,” in 10th Electronics Packaging Technology Conference, EPTC 2008, 2008, pp. 971–975.
[48] T.Chen andK.Jude, “17 . 5um Thin Cu Wire Bonding For Fragile Low-K Wafer Technology,” in Electronics Packaging Technology Conference, 2010, pp. 355–358.
[49] D.Adams andT. L.Alford, “Encapsulated silver for integrated circuit metallization,” Materials Science and Engineering R: Reports, vol. 40, no. 6. pp. 207–250, 2003.
[50] T. E.Graedel, “Corrosion mechanisms for silver exposed to the atmosphere,” J. Electrochem. Soc., vol. 139, no. 7, pp. 1963–1970, 1992.
[51] T. B.Massalski, Binary Alloy Phase Diagrams, vol. 2. 1990.
[52] E. A.Owen et al., “X-RAY AXALY-SIS OF SOLID SOLUTIONS,” Proc Phys Soc, vol. 36, p. 14, 1924.
[53] L. D.Gulay andB.Harbrecht, “The crystal structure of ζ1-Al3Cu4,” J. Alloys Compd., vol. 367, no. 1–2, pp. 103–108, 2004.
[54] W.Depmeier, “Structure of cubic aluminate sodalite Ca8[Al12O24](WO4)2 in comparison with its orthorhombic phase and with cubic Sr8[Al12O24](CrO4)2,” Acta Crystallogr. Sect. B, vol. 44, no. 3, pp. 201–207, 1988.
[55] L.Arnberg andS.Westman, “Crystal perfection in a noncentrosymmetric alloy. Refinement and test of twinning of the ?????Cu9Al4 structure,” Acta Crystallogr. Sect. A, vol. 34, no. 3, pp. 399–404, 1978.
[56] A.Meetsma, J. L.DeBoer, andS.VanSmaalen, “Refinement of the crystal structure of tetragonal Al2Cu,” J. Solid State Chem., vol. 83, no. 2, pp. 370–372, 1989.
[57] R.Pretorius, T. K.Marais, andC. C.Theron, “Thin film compound phase formation sequence: An effective heat of formation model,” Materials Science Reports, vol. 10, no. 1–2. pp. 1–83, 1993.
[58] R. T.Downs andM.Hall-Wallace, “The American Mineralogist crystal structure database,” Am. Mineral., vol. 88, no. 1, pp. 247–250, 2003.
[59] H. E.Swason, R. K.Fuyat, andG. M.Ugrinic, Standard X-ray Diffraction Powder Patterns. Washington, DC: U.S. Dept. of commerce: National Bureau of Standards, 1985.
[60] F.Haidara, M. C.Record, B.Duployer, andD.Mangelinck, “Investigation of reactive phase formation in the Al-Cu thin film systems,” Surf. Coatings Technol., vol. 206, no. 19–20, pp. 3851–3856, 2012.
[61] O.Mokhtari et al., “Effect of isothermal aging on the growth behavior of Cu/Al intermetallic compounds,” in ICEP 2014, 2014, pp. 144–147.
[62] K. N.Tu, “APPLIED PHYSICS REVIEWS — FOCUSED REVIEW Recent advances on electromigration in very-large-scale-integration of interconnects,” vol. 94, no. 9, 2003.
[63] P. S. H. andThomas andK.IBM, “Electromigration in metals,” Prog. Phys, vol. 52, pp. 301–348, 1989.
[64] K. N.Tu, “Electromigration in stressed thin films,” Phys. Rev. B, vol. 45, no. 3, pp. 1409–1413, 1992.
[65] J. R.Lloyd, “Electromigration in Thin Film Conductors,” Defect Diffus. Forum, vol. 143–147, pp. 1661–1672, 1997.
[66] H. B.Huntington andA. R.Grone, “Current-induced marker motion in gold wires,” J. Phys. Chem. Solids, vol. 20, no. 1, pp. 76–87, 1961.
[67] K. L.Lee, C. K.Hu, andK. N.Tu, “In situ scanning electron microscope comparison studies on electromigration of Cu and Cu(Sn) alloys for advanced chip interconnects,” J. Appl. Phys., vol. 78, no. 7, pp. 4428–4437, 1995.
[68] I. A.Blech, “Electromigration in thin aluminum films on titanium nitride,” J. Appl. Phys., vol. 47, no. 4, pp. 1203–1208, 1976.
[69] P.I, Introduction to Thermodynamics of Irreversible Processes. Springfield, IL: CC Thomas, 1955.
[70] T. H.Yang, Y. M.Lin, andF. Y.Ouyang, “Joule-heating-induced damage in Cu-Al wedge bonds under current stressing,” J. Electron. Mater., vol. 43, no. 1, pp. 270–276, 2014.
[71] B.Krabbenborg, “High current bond design rules based on bond pad degradation and fusing of the wire,” Microelectron. Reliab., vol. 39, no. 1, pp. 77–88, 1999.
[72] H.Gan andK. N.Tu, “Effect of electromigration on intermetallic compound formation in Pb-free solder - Cu interfaces,” 52Nd Electron. Components Technol. Conf. 2002 Proc., no. 1, pp. 1206–1212, 2002.
[73] H.Gan, W. J.Choi, G.Xu, andK. N.Tu, “Electromigration om Solder Joints and Solder Lines,” J. Met., vol. 54, no. 6, pp. 34–37, 2002.
[74] F. Y.Ouyang, H.Hsu, Y. P.Su, andT. C.Chang, “Electromigration induced failure on lead-free micro bumps in three-dimensional integrated circuits packaging,” J. Appl. Phys., vol. 112, no. 2, 2012.
[75] A.Birolini, “Investigation on The Long Term of Power IGBT Modulus,” in Proceedings of 1995 International Symposium on Power Semiconductor Devices & ICs, 1995, pp. 443–448.
[76] A. F.Mayadas andM.Shatzkes, “Electrical-resistivity model for polycrystalline films: The case of arbitrary reflection at external surfaces,” Phys. Rev. B, vol. 1, no. 4, pp. 1382–1389, 1970.
[77] E. T.Ogawa, K. D.Lee, V. A.Blaschke, andP. S.Ho, “Electromigration reliability issues in dual-damascene Cu interconnections,” IEEE Trans. Reliab., vol. 51, no. 4, pp. 403–419, 2002.
[78] C.-K.Hu andJ. M. E.Harper, “Copper interconnections and reliability,” Mater. Chem. Phys., vol. 52, pp. 5–16, 1998.
[79] J.Joseph Clement, “Electromigration modeling for integrated circuit interconnect reliability analysis,” IEEE Trans. Device Mater. Reliab., vol. 1, no. 1, pp. 33–42, 2001.
[80] A. S.Budiman et al., “Plasticity-amplified diffusivity: Dislocation cores as fast diffusion paths in CU interconnects,” in Annual Proceedings - Reliability Physics (Symposium), 2007, pp. 122–127.
[81] C. K.Hu, M. B.Small, K. P.Rodbell, C.Stanis, P.Blauner, andP. S.Ho, “Electromigration failure due to interfacial diffusion in fine Al alloy lines,” Appl. Phys. Lett., vol. 62, no. 9, pp. 1023–1025, 1993.
[82] A.Wolfenden andJ. M.Wolla, “Mechanical damping and dynamic modulus measurements in alumina and tungsten fibre-reinforced aluminium composites,” J. Mater. Sci., vol. 24, no. 9, pp. 3205–3212, 1989.
[83] W. F.Gale andT. C.Totemeir, “Smithells Metals Reference Book,” Smithells Met. Ref. B., pp. 1–2072, 2004.
[84] a.Charlesby, CRC materials science and engineering handbook, vol. 49, no. 2. 1997.
[85] A.Lodder andJ. P.Dekker, “The electromigration force in metallic bulk,” in Fourth international workshop on stress induced phenomena in metallization, 1998, pp. 315–328.