近年來，為了突破摩爾定律的瓶頸，3D IC封裝技術被視為極具前景的技術，而其中直接銅-銅接合技術(Direct Cu-Cu Bonding)極有潛力在將來取代銲錫球更縮小電子產品體積。本研究主要目的為研究銅薄膜在退火以及接合過程中的微結構變化，例如異常晶粒成長及消除雙晶的現象。首先，利用濺鍍方法製備高密度(111)方向雙晶銅薄膜，並進行熱處理及接合的實驗，再來，利用聚焦離子束、X-射線繞射分析及電子背向散射繞射等儀器來分析銅薄膜的微結構影像。為了製備出熱穩定性高的銅薄膜，我們藉由調整鍍膜機中不同電子槍功率及基板負偏壓來找到最佳化區間，並利用兩段式鍍膜的方法進一步改善銅膜品質，當銅膜試片在200℃下退火2小時之後，(111)方向的比例仍高達將近100%。再者，分析薄膜對薄膜接合試片的接合面後，發現在250℃下只要接合25分鐘就已有接合率超過80%的接合品質，而且不需要任何化學研磨拋光（CMP）的前處理，並發現應力驅使異常晶粒成長、雙晶柱合併變寬及側向成長快速等現象。在接合過程中，三交點成長和Nabarro-Herring Creep為接合主宰因子，伴隨著靠近基板的細小銅晶粒長大和側向成長，以及銅晶粒方向由(111)轉換成(200)的輔佐下，更加消除介面、提升接合品質。接著為了更符合高階電子產品的封裝結構需求，利用黃光微影實驗製備尺寸40微米到100微米的凸塊，亦成功達到凸塊對薄膜及凸塊對凸塊的接合，其接合率有超過80%良好的接合品質。最後，我們利用剪力測試及熱循環測試來分析接合試片的可靠度，發現接合試片的剪切力強度可以高達16Mpa且破裂面在矽晶片上，而試片在-55 ℃ ~150 ℃熱循環500 圈後，亦發現微結構並沒有顯著地改變，孔洞沒有因此變多、接合面沒有新的裂痕產生，藉由這兩種可靠度測試可以證明此研究的接合試片接合性質十分良好。

Cu-Cu direct bonding has become a promising method to achieve 3D IC package in semiconductor industry. The aim of this study was to investigate the microstructure evolution of Cu thin films during annealing and bonding processes, such as the mechanism of detwinning and abnormal grain growth. Highly (111)-preferred orientation nanotwinned Cu thin films were prepared by sputtering system, followed by heat treatment and direct bonding processes. The cross-sectional image and grain orientation were observed by FIB/SEM, XRD and EBSD. The optimized deposition parameter for nanotwinned Cu thin film to form was found by two-step deposition method. The percentage of（111）orientation of Cu could be as high as almost 100% at 200℃ for 2 hours, which presents high thermal stability of Cu thin films during heat treatment. Furthermore, the bonding interfaces of Cu-Cu direct bonding had superior quality and the bonding ratio could be achieved to 80% at 250℃ for 25 minutes without any CMP process. The phenomenon of stress-induced abnormal grain growth was also observed in bonding samples and the mechanism of Cu direct bonding started growing from the triple junctions coupled with Nabarro-Herring Creep. Grain growth of tiny grains near the substrate and lateral growth further eliminate the voids and enhance the bonding quality. Finally, to simulate the package in 3D IC, microbumps were fabricated by lithography. The bonding processes of bump - film and bump - bump were achieved and were passed by the reliability test such as Shear test and TCT test with excellent results.

中文摘要 i
Abstract ii
致謝 iii
Content v
List of Figures ix
List of Tables xviii
Chapter 1 Introduction 1
Chapter 2 Literature Review 3
2.1 Nanotwinned structure 5
2.1.1 Stacking Fault Energy 9
2.1.2 Deformation Twin and Growth Twin 9
2.2 Deposition Method 11
2.3 Characteristics of Nano-twinned Copper 14
2.3.1 Ultrahigh Strength and High Electrical Conductivity 14
2.3.2 Electromigration resistance and Thermal Stabilities 16
2.4 Direct Copper to Copper Bonding 18
2.5 Abnormal Grain Growth in Nano-twinned Copper Thin Film 20
2.6 Bonding Mechanism 23
2.6.1 Nabarro-Herring Creep 23
2.6.2 Modified Fullman and Fisher model 24
Chapter 3 Experimental processes 26
3.1 Sputtered Deposition System 27
3.2 Specimen Preparation and Pattern Production 29
3.2.1 Photo Lithography 29
3.2.2 Wet etching 33
3.3 Heat Treatment and Bonding Process 33
3.3.1 Tubular Furnace 34
3.3.2 Bonding Process (Film-Film, Bump-Film and Bump-Film) 35
3.3.3 Grinding and Polishing 35
3.4 Characteristics of Composition and Structure 36
3.4.1 Cross-sectional Image and Thickness: FIB/SEM 37
3.4.2 Crystal Structure and Preferred Orientation: XRD 39
3.4.3 Crystal Structure and Preferred Orientation: EBSD 41
3.5 Characteristics of Properties 43
3.5.1 Surface Roughness: AFM 43
3.5.2 Electrical Resistivity: Four-Point Probe 43
3.5.3 Reliability test: Shear test of Film-film specimen 45
3.5.4 Reliability test: Temperature Cycle Test (TCT) of Bump-Film specimen 46
Chapter 4 Results and Discussions 47
4.1 As-Deposited Copper Thin Film and Copper Bump 47
4.1.1 Surface Morphology & Cross-sectional Microstructure 47
4.1.2 Surface Roughness 57
4.1.3 Electrical Resistivity 61
4.1.4 Two - Step deposition process 63
4.2 Microstructure of Copper Thin Film during Annealing Process 66
4.3 The microstructure evolution during annealing processes 71
4.4 Microstructure and Properties of Direct Bonding Processes 72
4.4.1 Microstructure and Properties of Copper Film to Film Bonding 73
4.4.2 Microstructure and Properties of Copper Bump to Film Bonding 76
4.4.3 Microstructure and Properties of Copper Bump to Bump Bonding 78
4.4.4 Reliability test - Shear test and TCT test 80
4.5 The microstructure evolution during bonding processes 82
4.6 Mechanism of Abnormal Grain Growth during the Bonding Process 86
4.6.1 Stress-induced abnormal grain growth 86
4.6.2 Lateral growth 89
4.6.3 The bonding mechanisms during bonding processes 91
Chapter 5 Conclusion 95
Future Work 96
References 97
Appendix A AFM 3D Images 101

[1] W. R. Davis, J. Wilson, S. Mick, J. Xu, H. Hua, C. Mineo, et al., "Demystifying 3D ICs: The pros and cons of going vertical," IEEE Design & Test of Computers, vol. 22, pp. 498-510, 2005.
[2] R. R. Schaller, "Moore's law: past, present and future," IEEE spectrum, vol. 34, pp. 52-59, 1997.
[3] R. Labie, P. Limaye, K. Lee, C. Berry, E. Beyne, and I. De Wolf, "Reliability testing of Cu-Sn intermetallic micro-bump interconnections for 3D-device stacking," in 3rd Electronics System Integration Technology Conference ESTC, 2010, pp. 1-5.
[4] T. Suga, "Feasibility of surface activated bonding for ultra-fine pitch interconnection-A new concept of bump-less direct bonding for system level packaging," in 2000 Proceedings. 50th Electronic Components and Technology Conference (Cat. No. 00CH37070), 2000, pp. 702-705.
[5] S. Towle and P. H. Wermer, "Microelectronic package having a bumpless laminated interconnection layer," ed: Google Patents, 2003.
[6] S. Towle and P. H. Wermer, "Method of fabricating microelectronic package having a bumpless laminated interconnection layer," ed: Google Patents, 2006.
[7] Lei Lu, Yongfeng Shen, Xianhua Chen, Lihua Qian, and K. Lu, "Ultrahigh Strength and High Electrical Conductivity in Copper," Science, vol. 304, p. 422, 2004.
[8] C.-M. Liu, H.-w. Lin, Y.-C. Chu, C. Chen, D.-R. Lyu, K.-N. Chen, et al., "Low-temperature direct copper-to-copper bonding enabled by creep on highly (111)-oriented Cu surfaces," Scripta Materialia, vol. 78-79, pp. 65-68, 2014.
[9] Y.-C. Chu and C. Chen, "Anisotropic grain growth to eliminate bonding interfaces in direct copper-to-copper joints using <111>-oriented nanotwinned copper films," Thin Solid Films, vol. 667, pp. 55-58, 2018.
[10] J. Y. Juang, C. L. Lu, K. J. Chen, C. A. Chen, P. N. Hsu, C. Chen, et al., "Copper-to-copper direct bonding on highly (111)-oriented nanotwinned copper in no-vacuum ambient," Sci Rep, vol. 8, p. 13910, Sep 17 2018.
[11] N.-C. Lee, Reflow soldering processes: Elsevier, 2002.
[12] O. Anderoglu, A. Misra, H. Wang, and X. Zhang, Thermal stability of sputtered Cu films with nanoscale growth twins vol. 103, 2008.
[13] K. N. Tu, H.-Y. Hsiao, and C. Chen, "Transition from flip chip solder joint to 3D IC microbump: Its effect on microstructure anisotropy," Microelectronics Reliability, vol. 53, pp. 2-6, 2013.
[14] J. H. Lau, "The Most Cost-Effective Integrator (TSV Interposer) for 3D IC Integration System-in-Package (SiP)," Proceedings of the ASME 2011 Pacific Rim Technical Conference & Exposition, 2011.
[15] I.A. Ovid'ko and A. G. Sheinerman, "Mechanical properties of nanotwinned metals, a review," 2015.
[16] J.-H. Huang, "Lecture-notes of Physical Metallurgy (I)," 2012.
[17] M. J. Aziz, "Thermodynamics of diffusion under pressure and stress: Relation to point defect mechanisms," Applied Physics Letters, vol. 70, pp. 2810-2812, 1997.
[18] O. Anderoglu, A. Misra, H. Wang, and X. Zhang, "Thermal stability of sputtered Cu films with nanoscale growth twins," Journal of Applied Physics, vol. 103, p. 094322, 2008.
[19] L. Lu, Y. Shen, X. Chen, L. Qian, and K. Lu, "Ultrahigh Strength and High Electrical Conductivity in Copper," Science, vol. 304, p. 422, 2004.
[20] O. Anderoglu, A. Misra, H. Wang, F. Ronning, M. F. Hundley, and X. Zhang, "Epitaxial nanotwinned Cu films with high strength and high conductivity," Applied Physics Letters, vol. 93, p. 083108, 2008.
[21] I. J. Beyerlein, X. Zhang, and A. Misra, "Growth Twins and Deformation Twins in Metals," Annual Review of Materials Research, vol. 44, pp. 329-363, 2014.
[22] V. Germain, J. Li, D. Ingert, Z. L. Wang, and M. P. Pileni, "Stacking Faults in Formation of Silver Nanodisks," The Journal of Physical Chemistry B, vol. 107, pp. 8717-8720, 2003/08/01 2003.
[23] G. Meng, Y. Shao, T. Zhang, Y. Zhang, and F. Wang, "Synthesis and corrosion property of pure Ni with a high density of nanoscale twins," Electrochimica Acta, vol. 53, pp. 5923-5926, 2008.
[24] F. Sun, G. Meng, T. Zhang, Y. Shao, F. Wang, C. Dong, et al., "Electrochemical corrosion behavior of nickel coating with high density nano-scale twins (NT) in solution with Cl−," Electrochimica Acta, vol. 54, pp. 1578-1583, 2/1/ 2009.
[25] X. Zhang, O. Anderoglu, R. G. Hoagland, and A. Misra, "Nanoscale growth twins in sputtered metal films," JOM, vol. 60, pp. 75-78, 2008/09/01 2008.
[26] F. K. Yan, G. Z. Liu, N. R. Tao, and K. Lu, "Strength and ductility of 316L austenitic stainless steel strengthened by nano-scale twin bundles," Acta Materialia, vol. 60, pp. 1059-1071, 2012.
[27] J. W. Christian and S. Mahajan, "Deformation twinning," Progress in Materials Science, vol. 39, pp. 1-157, 1995.
[28] H. Suzuki and C. S. Barrett, "Deformation twinning in silver-gold alloys," Acta Metallurgica, vol. 6, pp. 156-165, 1958.
[29] S. R. K. EHAB EL-DANAF, and ROGER D. DOHERTY, "Influence of Grain Size and Stacking-Fault Energy on Deformation Twinning in Fcc Metals," METALLURGICAL AND MATERIALS TRANSACTIONS A, vol. 30A, 1999.
[30] K. C. Chen, W. W. Wu, C. N. Liao, L. J. Chen, and K. N. Tu, "Observation of atomic diffusion at twin-modified grain boundaries in copper," Science, vol. 321, pp. 1066-9, Aug 22 2008.
[31] S CRONJE∗, R E KROON, and W. R. a. J. H. NEETHLING, "Twinning in copper deformed at high strain rates," Bull. Mater. Sci., vol. 36, p. 157, 2013.
[32] "Sputter deposition, http://www.oxford-vacuum.com/background/thin_film/sputtering.htm," Oxford Vacuum Science.
[33] Kathy Cook and Maggie Zoberbier, "TSV Processing and Wafer Stacking.."
[34] Min Ni, Qing Su, ZongwuTang, and J. Kawa, "Efficient Design Practices for Thermal Management of TSV based 3D IC System," ISPD, 2010.
[35] Y.-S. Huang, C.-M. Liu, W.-L. Chiu, and C. Chen, "Grain growth in electroplated (111)-oriented nanotwinned Cu," Scripta Materialia, vol. 89, pp. 5-8, 2014.
[36] W. D. Callister Jr and D. G. Rethwisch, Fundamentals of materials science and engineering: an integrated approach: John Wiley & Sons, 2012.
[37] K.-C. Chen, W.-W. Wu, C.-N. Liao, L.-J. Chen, and K. N. Tu, "Observation of Atomic Diffusion at Twin-Modified Grain Boundaries in Copper," Science, vol. 321, pp. 1066-1069, August 22, 2008 2008.
[38] C. Saldana, T. G. Murthy, M. R. Shankar, E. A. Stach, and S. Chandrasekar, "Stabilizing nanostructured materials by coherent nanotwins and their grain boundary triple junction drag," Applied Physics Letters, vol. 94, p. 021910, 2009.
[39] M. Upmanyu, D. J. Srolovitz, L. S. Shvindlerman, and G. Gottstein, "Molecular dynamics simulation of triple junction migration," Acta Materialia, vol. 50, pp. 1405-1420, 2002.
[40] U. Czubayko, V. G. Sursaeva, G. Gottstein, and L. S. Shvindlerman, "Influence of triple junctions on grain boundary motion," Acta Materialia, vol. 46, pp. 5863-5871, 10/9/ 1998.
[41] B. Rebhan and K. Hingerl, "Physical mechanisms of copper-copper wafer bonding," Journal of Applied Physics, vol. 118, p. 135301, 2015.
[42] J. Cho, S. Yu, M. P. C. Roma, S. Maganty, and S. Park, E. Bersch, et al., "Mechanism of Low-Temperature Copper-to-Copper Direct Bonding for 3D TSV Package Interconnection," Electronic Components & Technology Conference, 2013.
[43] T. Chih-Han, L. Chien-Min, L. Han-Wen, C. Yi-Cheng, C. Chih, L. Dian-Rong, et al., "Low-temperature and low pressure copper-to-copper direct bonding enabled by creep on highly (111)-oriented Cu surfaces," in Electronics Packaging and iMAPS All Asia Conference (ICEP-IACC), 2015 International Conference on, 2015, pp. 523-526.
[44] C. V. Thompson and R. Carel, "Stress and grain growth in thin films," Journal of the Mechanics and Physics of Solids, vol. 44, pp. 657-673, 1996.
[45] H. J. Frost, C. V. Thompson, and D. T. Walton, "Simulation of thin film grain structures—II. Abnormal grain growth," Acta Metallurgica et Materialia, vol. 40, pp. 779-793, 1992.
[46] L. X. Di Xu, Vinay Sriram, Ke Sun, Jenn-Ming Yang, and K.-N. Tu, "Nanotwin-modified Copper Interconnects and Its Effect on the Physical Properties of Copper," 2009.
[47] C. Herring, "Diffusional Viscosity of a Poly crystalline Solid," J. Appl. Phys., vol. 21,437-445, 1950.
[48] R. L. fullman and J. C. Fisher, "Formation of Annealing Twins During Grain Growth," Journal of Applied Physics, vol. 22, 1350, 1951.
[49] Kriegor27, "The principle of FIB," Wikipedia, 1999.
[50] A. J. Bushby, M. P'Ng K, R. D. Young, C. Pinali, C. Knupp, and A. J. Quantock, "Imaging three-dimensional tissue architectures by focused ion beam scanning electron microscopy," Nat Protoc, vol. 6, pp. 845-58, Jun 2011.
[51] M. K. Adam J. Schwartz, Brent L. Adams, David P. Field, "Electron Backscatter Diffraction in Materials Science," 2009.
[52] S. M. Sze, VLSI technology: McGraw-hill, 1988.
[53] M. Hasegawa, M. Mieszala, Y. Zhang, R. Erni, J. Michler, and L. Philippe, "Orientation-controlled nanotwinned copper prepared by electrodeposition," Electrochimica Acta, vol. 178, pp. 458-467, 2015.
[54] H. Lee, S. S. Wong, and S. D. Lopatin, "Correlation of stress and texture evolution during self-and thermal annealing of electroplated Cu films," Journal of Applied Physics, vol. 93, pp. 3796-3804, 2003.
[55] C.-L. Lu, H.-W. Lin, C.-M. Liu, Y.-S. Huang, T.-L. Lu, T.-C. Liu, et al., "Extremely anisotropic single-crystal growth in nanotwinned copper," NPG Asia Materials, vol. 6, pp. e135-e135, 2014.
[56] J. Greiser, P. Müllner, and E. Arzt, "Abnormal growth of “giant” grains in silver thin films," Acta materialia, vol. 49, pp. 1041-1050, 2001.
[57] S.-Y. Liang, J.-M. Song, S.-K. Huang, Y.-T. Chiu, D. Tarng, and C.-P. Hung, "Light enhanced direct Cu bonding for advanced electronic assembly," Journal of Materials Science: Materials in Electronics, vol. 29, pp. 14144-14150, 2018.
[58] Z. Liu, J. Cai, and Q. Wang, "Interfacial morphology and grain orientation during bumpless direct Cu bonding," Thin Solid Films, vol. 595, pp. 118-123, 2015.
[59] G. Gottstein, L. S. Shvindlerman, and B. Zhao, "Thermodynamics and kinetics of grain boundary triple junctions in metals: Recent developments," Scripta Materialia, vol. 62, pp. 914-917, 2010.