本研究係探討3D IC微凸塊在通電狀態之下，接點內部發生的材料反應。實驗共有四種不同結構的微凸塊，分別為TiCuCuNi/Sn1.8Ag/ ENEPIG、TiCuCuNi/Sn1.8Ag/OSP-Cu、TiCuCu/Sn1.8Ag/OSP-Cu、以及TiCuCu/Sn1.8Ag/ENEPIG，並於125℃的環境溫度施予電流密度1×104 A/cm2，通電24、100、200、300小時、以及測試至失效(566小時)。為了瞭解接點內部的材料反應與IMC在接點中的生成行為與分佈，接點先研磨拋光至最大截面之後，再從與最大截面垂直的方向研磨次截面。
實驗結果顯示，長時間通電後，伴隨凸塊底層金屬(Under bump metallization, UBM)與/或基板金屬的消耗，大量IMC生成佔滿整個接點，並且於部份接點中產生孔洞(void)及裂縫(crack)。此外於TiCuCu/Sn1.8Ag/OSP-Cu結構中，觀察到明顯Cu6Sn5與Cu3Sn之間的轉換(transformation)現象，而Ag3Sn、微孔洞(microvoid)以及剩餘未反應完的Cu6Sn5聚集在接點中央區域，使得裂縫形成在該區域。另外截面分析顯示IMC並非均勻分佈於接點中，受到電流方向影響，IMC分佈於特定區域，因此有偏析(segregation)的現象。最終IMC的形成與缺陷的產生，導致接點電阻隨著通電時間增長而緩慢上升，通電最末階段，電阻急遽增加則可能是鋁導線處失效所導致。

This present study investigated the materials interactions of 3D IC microbump structures induced by current stressing. The four types of microbump structure investigated include: TiCuCuNi/Sn1.8Ag/ENEPIG, TiCuCuNi/Sn1.8Ag/OSP-Cu, TiCuCu/Sn1.8Ag/OSP-Cu, and TiCuCu/Sn1.8Ag/ENEPIG. The current stressing was conducted at a current density of 1.0×104 A/cm2 under 125℃ for various durations of 24hr, 100hr, 200hr, 300hr, and test to fail(566hr). In order to have a good understanding to the materials interactions and the IMCs growth behaviors and distribution, the bumps were ground and polished to the maximum cross-section first, followed by grinding and polishing on the perpendicular direction at different cross-section. The experimental results reveal that the IMCs grew to almost completely occupy the entire solder bump accompanied under bump metal (UBM) and/or substrate consumption after long time current stressing. Voids and cracks were found to form within the micrbumps. The transformation between Cu6Sn5 and Cu3Sn was observed. The Ag3Sn, microvoids, and remained Cu6Sn5 gathered at the center of solder joint, which resulted in crack formation along the central region of the joint. The sub-cross-sectional analysis reveals that the IMCs distribution was not uniform. The IMCs segregated at certain corner of the joint and was related to the current flow direction. The resistances of the microbumps will increase gradually when caused by IMCs formation. The abruptly increase in resistances at the final stage of current stressing might be attributed to the defect formation at the Al trace.

1. K. Sakuma, P. S. Andry, B. Dang, J. Maria, C. K. Tsang, C. Patel, S. L. Wright, and B. Webb, “3D Chip Stacking Technology with Low-Volume Lead-Free Interconnections”, Proceeding of IEEE Electronic Components and Technology Conference, 2007, pp. 627~632.
2. J. H. Lau, “Overview and Outlook of Through-Silicon-Via (TSV) and 3D Integrations”, Microelectronics International, Vol. 8, No. 2, 2011, pp. 8~12.
3. J. H. Lau, Flip Chip Technologies, McGraw-Hill, New York, 1995, Chapter 3.
4. M. Pecht, Integrated Circuit, Hybrid, and Multichip Module Package Design Guidelines, John Wiley & Sons, New York, 1994, Chapter 7.
5. M. Abtew and G. Selvaduray, “Lead-free Solders in Microelectronics”, Materials Science and Engineering, Vol. 27, 2000, pp. 95~141.
6. E. B. Webb, G. S Grest, D. R. Heine, and J. J. Hoyt, “Dissolutive Wetting of Ag on Cu: A Molecular Dynamics Simulation Study”, Acta Materialia, Vol. 53, 2005, pp. 3163~3177.
7. S. Wiegele, P. Thompson, R. Lee, and E. Ramsland, “Reliability and Process Characterization Electroless Nickel-Gold/Solder Flip Chip Interconnect and Technology”, Proceeding of IEEE Electronic Components and Technology Conference, 1998, pp. 861~866.
8. J. H. Lau, Chip on Board Technologies for Multichip Modules, Van Nostrand Reinhold, New York, 1995, Chapter 5.
9. T. L. Shao, Y. H. Chen, S. H. Chiu, and C. Chen, “Electromigration Failure Mechanisms for SnAg 3.5 solder bumps on Ti/Cr-Cu/Cu and Ni(P)/Au Metallization Pads”, Journal of Applied Physics, Vol. 96, No. 8, 2004, pp. 4518~4524.
10. Y. L. Lin, C. W. Chang, C. M. Tsai, C. W. Lee, and C. R. Kao, “Electromigration-Induced UBM Consumption and the Resulting Failure Mechanisms in Flip-Chip Solder Joints”, Journal of Electronic Materials, Vol. 35, No. 5, 2006, pp. 1010~1016.
11. W. J. Choi, E. C. C. Yeh, and K. N. Tu, “Mean-Time-to-Failure Study of Flip Chip Solder Joints on Cu/Ni(V)/Al Thin-Film Under-Bump-Metallization”, Journal of Applied Physics, Vol. 94, No. 9, 2003, pp. 5665~5671.
12. A. Munding, H. Hubner, A. Kaiser, S. Penka, P. Bankart, and E. Kohn, Wafer Level 3-D ICs Process Technology, Springer Science & Business Media, New York, 2008, p. 132.
13. Y. L. Lin, Y. S. Lai, Y. W. Lin, and C. R. Kao, “Effect of UBM Thickness on the Mean Time to Failure of Flip-Chip Solder Joints under Electromigration”, Journal of Electronic Materials, Vol. 37, No. 1, 2008, pp. 96~101.
14. S. Lee, Y. X. Guo and C. K. Ong, “Electromigration Effect on Cu-pillar(Sn) Bumps”, Proceeding of IEEE Electronics Packaging Technology Conference, Vol. 1, 2005, pp. 135~139.
15. J. W. Nah, J. O. Suh, and K. N. Tu, “Electromigration in Flip Chip Solder Joints Having a Thick Cu Column Bump and a Shallow Solder Interconnect”, Journal of Applied Physics, Vol. 100, No. 12, 2006, pp. 123513-1~123513-5.
16. Y. S. Lai, Y. T. Chiu, C. W. Lee, Y. H. Shao, and J. Chen, “Electromigration Reliability and Morphologies of Cu Pillar Flip-Chip Solder Joints”, Proceeding of IEEE Electonic Components and Technology Conference, 2008, pp. 330~335.
17. J. W. Nah, K. Chen, J. O. Suh, and K. N. Tu, “Electromigration Study in Flip Chip Solder Joints”, Proceeding of IEEE Electronic Components and Technology Conference, 2007, pp. 1450~1455.
18. L. Xu, J. K. Han, J. Liang, K. N. Tu, and Y. S. Lai, “Electromigration Induced High Fraction of Compound Formation in SnAgCu Flip Chip Solder Joints with Copper Column”, Applied Physics Letters, Vol. 92, 2008, pp. 262104-1~262104-3.
19. R. Labie, T. Webers, C. Winters, V. Cherman, K. Croes, and B. Vandevelde, “Electromigration Failure Mechanisms for Different Flip Chip Bump Configurations”, Proceeding of IEEE International Reliability Physics Symposium, 2011, pp. 5F.4.1~5F.4.5.
20. J. H. Yoo, I. S. Kang, G. J. Jung, S. Kim, H. S Ahn, W. H. Choi, K. S. Jun, D. W. Jang, I. H. Baek, J. N. Yu, “Analysis of Electromigration for Cu Pillar Bump in Flip Chip Package”, Proceeding of IEEE Electronics Packaging Technology Conference, 2010, pp. 129~133.
21. H. Y. Chuang, T. L. Yang, M. S. Kuo, Y. J. Chen, J. J. Yu, C. C. Li, and C. R. Kao, “Critical Concerns in Soldering Reactions Arising from Space Confinement in 3-D IC Packages”, Proceeding of IEEE Transactions on Device and Materials Reliability, Vol. 12, No. 2, 2012, pp. 233~240.
22. L. Yin and P. Borgesen, “On the Root Cause of Kirkendall Voiding in Cu3Sn”, Journal of Materials Research, Vol. 26, No. 3, 2011, pp. 455~466.
23. K. S. Kim, S. H. Huh, K. Suganuma, “Effects of Intermetallic Compounds on Properties of Sn-Ag-Cu Lead-free Soldered Joints”, Journal of Alloys and Compounds, Vol. 352, 2003, pp. 226~236.
24. Y. Wang, S. H. Chae, R. Dunne, Y. Takahashi, K. Mawatari, P. Steinmann, T. Bonifield, T. Jiang, J. Im, and P. S. Ho, “Effect of Intermetallic Formation on Electromigration Reliability of TSV-Microbump Joints in 3D Interconnect”, Proceeding of IEEE Electronic Components and Technology Conference, 2012, pp. 319~325.
25. C. C. Lee, P. J. Wang, and J. S. Kim, “Are Intermetallics in Solder Joints Really Brittle?”, Proceeding of IEEE Electronic Components and Technology Conference, 2007, pp. 648~652.
26. D. Q. Yu, T. C. Chai, M. L. Thew, Y. Y. Ong, V. S. Rao, L. C. Wai, and J. H. Lau, ”Electromigration Study of 50μm Pitch Micro Solder Bumps using Four-Point Kelvin Structure”, Proceeding of IEEE Electronic Components and Technology Conference, 2009, pp. 930~935.
27. C. C. Wei, C. H. Yu, C. H. Tung, R. Y. Huang, C. C. Hsieh, C. C. Chiu, H. Y. Hsiao, Y. W. Chang, C. K. Lin, Y. C. Liang, C. Chen, T. C. Yeh, C. Lin, and C. H. Yu, “Comparison of the Electromigration Behaviors Between Micro-bumps and C4 Solder Bumps”, Proceeding of IEEE Electronic Components and Technology Conference, 2011, pp. 706~710.
28. C. K. Lin, Y. W. Chang, and C. Chen, “Experimental and Simulation Analysis of Concave-down Resistance Curve during Electromigration in Solder Joints”, Journal of Applied Physics, Vol. 115, 2014, pp. 083707-1~083707-6.
29. S. W. Chen, C. M. Chen, and W. C. Liu, “Electric Current Effects Upon the Sn/Cu and Sn/Ni Interfacial Reactions”, Journal of Electronic Materials, Vol. 27, No. 11, 1998, pp. 1193~1199.
30. W. J. Deng, K. L. Lin, Y. T. Chiu, Y. S. Lai, “Electromigration-Induced Accelerated Consumption of Cu Pad in Flip Chip Sn2.6Ag Solder Joints”, Proceeding of IEEE Electronic Components and Technology Conference, 2011, pp. 114~117.
31. J. Keller, D. Baither, U. Wilke, G. Schmitz, “Mechanical Properties of Pb-Free SnAg Solder Joints”, Acta Materialia, Vol. 59, No.7, 2011, pp. 2731~2741.
32. T. B. Massalski, Binary Alloy Phase Diagrams, ASM International, Materials Park, Ohio, Vol. 1, 1986, p. 71.
33. D. Shangguan, Lead-Free Solder Interconnect Reliability, ASM International, Materials Park, Ohio, 2005, Chpater 3.
34. H. T. Lee , Y. F. Chen , T. F. Hong, and K. T. Shih, “Effect of Cooling Rate on Ag3Sn Formation in Sn-Ag Based Lead-Free Solder”, Proceeding of IEEE Electronics Packaging Technology Conference, 2009, pp. 875~878.
35. P. Snugovsky, P. Arrowsmith, and M. Romansky, “Electroless Ni/Immersion Au Interconnects: Investigation of Black Pad in Wire Bonds and Solder Joints”, Journal of Electronic Materials, Vol. 30, No. 9, 2001, pp. 1262~1270.
36. S. P. Peng, D. Lin, and C. E. Ho, “Comparative Study of Au/Pd/Ni(P) Surface Finish in Eutectic PbSn and Sn3Ag0.5Cu Soldering Systems”, Proceeding of International Microsystems, Packaging, Assembly and Circuits Technology Conference, 2009, pp. 505~508.
37. T. B. Massalski, Binary Alloy Phase Diagrams, ASM International, Materials Park, Ohio, Vol. 1, 1986, p. 965.
38. K. N. Tu, and R. D. Thompson, “Kinetics of Interfacial Reaction in Bimetallic Cu-Sn Thin Films”, Acta Materialia, Vol. 30, 1982, pp. 947~952.
39. K. N. Tu, “Cu/Sn Interfacial Reactions: Thin-film Case versus Bulk Case”, Materials Chemistry and Physics, Vol. 46, 1996, pp. 217~223.
40. Z. Mei, M. Ahmad, M. Hu, and G. Ramakrishna, “Kirkendall Voids at Cu/Solder Interface and Their Effects on Solder Joint Reliability”, Proceeding of IEEE Electronic Components and Technology Conference, Vol. 1, 2005, pp. 415~420.
41. J. Yu and J. Y. Kim, “Effects of Residual S on Kirkendall Void Formation at Cu/Sn–3.5Ag Solder Joints”, Acta Materialia, Vol. 56, No. 19, 2008, pp. 5514~5523.
42. T. B. Massalski, Binary Alloy Phase Diagrams, ASM International, Materials Park, Ohio, Vol. 2, 1986, p. 1759.
43. W. J. Tomlinson and H. G. Rhodes, “Kinetics of Intermetallic Compound Growth between Nickel, Electroless Ni-P, Electroless Ni-B and Tin at 453 to 493K”, Journal of Materials Science, Vol. 22, No. 5, 1987, pp. 1769~1772.
44. S. Bader, W. Gust, and H. Hieber, “Rapid Formation of Intermetallic Compounds by Interdiffusion in the Cu-Sn and Ni-Sn Systems”, Acta Metallurgica et Materialia, Vol. 43, No. 1, 1995, pp. 329~337.
45. T. B. Massalski, Binary Alloy Phase Diagrams, ASM International, Materials Park, Ohio, Vol. 2, 1986, p. 316.
46. T. Laurila, V. Vuorinen, J. K. Kivilahti, “Interfacial Reactions between Lead-Free Solders and Common Base Materials”, Materials Science and Engineering: R: Reports, Vol. 49, No. 1-2, 2005, pp. 1~60.
47. T. B. Massalski, Binary Alloy Phase Diagrams, ASM International, Materials Park, Ohio, Vol. 2, 1986, p. 1874.
48. C. E. Ho, W. Gierlotka, and S. W. Lin, “Strong Effect of Pd Concentration on the Soldering Reaction Between Ni and Sn–Pd Alloys”, Journal of Materials Research, Vol. 25, No. 11, 2010, pp. 2078~2081.
49. J. V. Ek and A. Lodder, “Electromigration of Hydrogen in Metals”, Defect and Diffusion Forum, Vol. 115, 1994, pp. 3~4.
50. V. B. Fiks, “On the Mechanism of the Ions in Metals”, Soviet Physics-Solid State, Vol. 1, 1959, pp. 14~18.
51. H. B. Huntington and A. R. Grone, “Current-Induced Marker Motion in Gold Wires”, Journal of Physics and Chemistry of Solids, Vol. 20, 1961, pp. 76~87.
52. L. Zhang, S. Ou, J. Huang, K. N. Tu, S. Gee, and L. Nguyen, “Effect of Current Crowding on Void Propagation at the Interface between Intermetallic Compound and Solder in Flip Chip Solder Joints”, Applied Physics Letters, Vol. 88, No. 1, 2006, pp. 012106-1~012106-3.
53. K. N. Tu, Solder Joint Technology Materials, Properties, and Reliability, Springer, New York, 2007, p. 253.
54. J. H. Ke, T. L. Yang, Y. S. Lai, and C. R. Kao, “Analysis and Experimental Verification of the Competing Degradation Mechanisms for Solder Joints under Electron Current Stressing”, Acta Materialia, Vol. 59, No. 6, 2011, pp. 2462~2468.
55. C. K. Lin, W. A. Tsao, Y. C. Liang, and C. Chen, “Temperature-Dependent Failure Mechanism of SnAg Solder Joints with Cu Metallization after Current Stressing: Experimentation and Analysis”, Journal of Applied Physics, Vol. 114, No. 11, 2013, pp. 113711-1~113711-7.
56. H. Gan and K. N. Tu, “Polarity Effect of Electromigration on Kinetics of Intermetallic Compound Formation in Pb-free Solder V-groove Samples”, Journal of Applied Physics, Vol. 97, No. 6, 2005, pp. 063514-1~063514-10.
57. Y. H. Hsiao, K. L. Lin, C. W. Lee, Y. H. Shao, and Y. S. Lai, “Study of Electromigration-Induced Failures on Cu Pillar Bumps Joined to OSP and ENEPIG Substrates”, Journal of Electronic Materials, Vol. 41, No. 12, 2012, pp. 3368~3374.
58. W. Y. Chen, T. C. Chiu, K. L. Lin, and Y. S Lai, “Electro-recrystallization of Intermetallic Compound in the Sn0.7Cu Solder Joint”, Intermetallics, Vol. 26, 2012, pp. 40~43.
59. W. C. Wang, K. L. Lin, Y.T. Chiu, and Y. S. Lai, “The Growth and Segregation of Intermetallic Compounds in the Bulk of Flip Chip Sn2.4Ag Solder Joint under Electrical Current Stressing”, Proceeding of IEEE Electronic Components and Technology Conference, 2013, pp. 1600~1605.
60. W. Roush and J. Jaspal, “Thermomigration in Lead-indium Solder”, Proceeding of 32nd Electronic Components Conference, 1982, pp. 342~345.
61. A. T. Huang, A. M. Gusak, K. N. Tu, and Y. S. Lai, “Thermomigration in SnPb Composite Flip Chip Solder Joints”, Applied Physics Letters, Vol. 88, No. 14, 2006, pp. 141911-1~141911-3.
62. F. Y. Ouyang and W. C. Jhu, “Comparison of Thermomigration Behaviors between Pb-free Flip Chip Solder Joints and Microbumps in Three Dimensional Integrated Circuits: Bump Height Effect”, Journal of Applied Physics, Vol. 113, No. 4, 2013, pp. 043711-1~043711-8.
63. C. C. Li, Z. X. Zhu, M. H. Chen, and C. R. Kao, “Volume Shrinkage Induced by Interfacial Reactions in Micro Joints”, Proceeding of IEEE International Symposium on Advanced Packaging Materials, Session 1-2, No. 21, 2013, pp. 8~14.
64. H. Hsu, T. Y. Lin, and F. Y. Ouyang, “Evaluation of Electromigration Behaviors of Pb-Free Microbumps in Three-Dimensional Integrated Circuit Packaging”, Journal of Electronic Materials, Vol. 43, No. 1, 2014, pp. 236~246.
65. Y. C. Liang, W. A. Tsao, C. Chen, D. J. Yao, and A. T. Huang, “Influence of Cu Column Under-Bump-Metallizations on Current Crowding and Joule Heating Effects of Electromigration in Flip-Chip Solder Joints”, Journal of Applied Physics, Vol. 111, No. 4, 2012, pp. 043705-1~043705-7.
66. L. Y. Hsiao, G. Y. Jang, K. J. Wang, and J. G. Duh, “Inhibiting AuSn4 Formation by Controlling the Interfacial Reaction in Solder Joints” Journal of Electronic Materials, Vol. 36, No. 11, 2007, pp. 1476~1482.
67. 李魁斌, “銅與鎳在銲料中的交互作用”, 國立中央大學碩士論文, 民國九十四年, pp. 48~50.
68. T. C. Huang, T. L. Yang, J. H. Ke, C. H. Hsueh, and C. R. Kao, “Effects of Sn Grain Orientation on Substrate Dissolution and Intermetallic Precipitation in Solder Joints Under Electron Current Stressing”, Scripta Materialia, Vol. 80, 2014, pp. 37~41.
69. B. J. Kim, G. T. Lim, J. Kim, K. Lee, Y. B. Park, H. Y. Lee, and Y. C. Joo, “Intermetallic Compound Growth and Reliability of Cu Pillar Bumps Under Current Stressing”, Journal of Electronic Materials, Vol. 39, No. 10, 2010, pp. 2281~2285.
70. H. T. Chen, C. Q. Wang, C. Yan, Y. Huang, and Y. H. Tian, “Effects of Solder Volume on Formation and Redeposition of Au-Containing Intermetallics in Ni/Au-SnAgCu-Ni(P) Solder Joints”, Journal of Electronic Materials, Vol. 36, No. 1, 2007, pp. 33~39.
71. Y. M. Lin, C. J. Zhan, J. Y. Juang, J. H. Lau, T. H. Chen, R. Lo, M. Kao, T. Tian, and K. N. Tu, “Electromigration in Ni/Sn Intermetallic Micro Bump Joint for 3D IC Chip Stacking”, Proceeding of IEEE Electronic Components and Technology Conference, 2011, pp. 351~357.