Journal of the Microelectronics and Packaging Society (마이크로전자및패키징학회지)

The Korean Microelectronics and Packaging Society (한국마이크로전자및패키징학회)
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Evaluation of 12nm Ti Layer for Low Temperature Cu-Cu Bonding

저온 Cu-Cu본딩을 위한 12nm 티타늄 박막 특성 분석

  • Park, Seungmin (Department of Manufacturing System and Design Engineering, Seoul National University of Science and Technology) ;
  • Kim, Yoonho (Department of Manufacturing System and Design Engineering, Seoul National University of Science and Technology) ;
  • Kim, Sarah Eunkyung (Department of Nano-IT Convergence Engineering, Seoul National University of Science and Technology)
  • 박승민 (서울과학기술대학교, MSDE학과) ;
  • 김윤호 (서울과학기술대학교, MSDE학과) ;
  • 김사라은경 (서울과학기술대학교, 나노IT융합공학과)
  • Received : 2021.07.27
  • Accepted : 2021.08.12
  • Published : 2021.09.30
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Abstract

Miniaturization of semiconductor devices has recently faced a physical limitation. To overcome this, 3D packaging in which semiconductor devices are vertically stacked has been actively developed. 3D packaging requires three unit processes of TSV, wafer grinding, and bonding, and among these, copper bonding is becoming very important for high performance and fine-pitch in 3D packaging. In this study, the effects of Ti nanolayer on the antioxidation of copper surface and low-temperature Cu bonding was investigated. The diffusion rate of Ti into Cu is faster than Cu into Ti in the temperature ranging from room temperature to 200℃, which shows that the titanium nanolayer can be effective for low-temperature copper bonding. The 12nm-thick titanium layer was uniformly deposited on the copper surface, and the surface roughness (Rq) was lowered from 4.1 nm to 3.2 nm. Cu bonding using Ti nanolayer was carried out at 200℃ for 1 hour, and then annealing at the same temperature and time. The average shear strength measured after bonding was 13.2 MPa.

최근 반도체 소자의 소형화는 물리적 한계에 봉착했으며, 이를 극복하기 위한 방법 중 하나로 반도체 소자를 수직으로 쌓는 3D 패키징이 활발하게 개발되었다. 3D 패키징은 TSV, 웨이퍼 연삭, 본딩의 단위공정이 필요하며, 성능향상과 미세피치를 위해서 구리 본딩이 매우 중요하게 대두되고 있다. 본 연구에서는 대기중에서의 구리 표면의 산화방지와 저온 구리 본딩에 티타늄 나노 박막이 미치는 영향을 조사하였다. 상온과 200℃ 사이의 낮은 온도 범위에서 티타늄이 구리로 확산되는 속도가 구리가 티타늄으로 확산되는 속도보다 빠르게 나타났고, 이는 티타늄 나노 박막이 저온 구리 본딩에 효과적임을 보여준다. 12 nm 티타늄 박막은 구리 표면 위에 균일하게 증착되었고, 표면거칠기(Rq)를 4.1 nm에서 3.2 nm로 낮추었다. 티타늄 나노 박막을 이용한 구리 본딩은 200℃에서 1 시간 동안 진행하였고, 이후 동일한 온도와 시간 동안 열처리를 하였다. 본딩 이후 측정된 평균 전단강도는 13.2 MPa이었다.

Keywords

Acknowledgement

This research was supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Science and ICT (NRF-2018R1A2B6003921) and also was partially supported by the Ministry of Trade, Industry & Energy (#20003524).

References

  1. P. Ramm, A. Klumpp, R. Merkel, J. Weber, R. Wieland, A. Ostmann, and J. Wolf, "3D System Integration Technologies", Mat. Res. Soc. Symp. Proc., 766, E5.6.1 (2003)/
  2. S. E. Kim, and S. Kim, "Wafer level Cu-Cu direct bonding for 3D integration", Microelectron. Eng., 137, 158-163 (2015)/ https://doi.org/10.1016/j.mee.2014.12.012
  3. H. Seo, H. Park, and S. E. Kim, "Cu-SiO2 Hybrid Bonding", J. Microelectron. Packag. Soc., 27(1), 17-24 (2020)/
  4. K. Banerjee, S. J. Souri, P. Kapur, and K. C. Saraswat, "3-D ICs: A Novel Chip Design for Improving Deep-Submicrometer Interconnect Performance and Systems-on-Chip Integration", Proc. IEEE, 89(5), 602-633 (2001)/ https://doi.org/10.1109/5.929647
  5. K. N. Chen, C. S. Tan, A. Fan, and R. Reif, "Copper Bonded Layers Analysis and Effects of Copper Surface Conditions on Bonding Quality for Three-Dimensional Integration", J. Electron. Mater., 34(12), 1464-1467 (2005)/ https://doi.org/10.1007/s11664-005-0151-0
  6. B. Rebhan, and K. Hingerl, "Physical mechanisms of copper-copper wafer bonding", J. Appl. Phys., 118(13), 135301 (2015). https://doi.org/10.1063/1.4932146
  7. Y. M. Lin, C. J. Zhan, K. S. Kao, C. W. Fan, S. C. Chung, Y. W. Huang, S. Y. Huang, J. Y. Chang, T. F. Yang, J. H. Lau, and T. H. Chen, "Low Temperature Bonding using Non-conductive adhesive for 3D chip stacking with 30um-Pitch Micro Solder Bump Interconnections", IEEE 6th IMPACT, 478-481 (2011).
  8. Y. Kim, S. Park, and S. E. Kim, "Effect of Ag Nanolayer in Low Temperature Cu/Ag-Ag/Cu Bonding", J. Microelectron. Packag. Soc., 28(2), 59-64 (2021). https://doi.org/10.6117/KMEPS.2021.28.2.059
  9. S. Bonam, A. K. Panigrahi, C. H. Kumar, S. R. K. Vanjari, and S. G. Singh, "Interface and Reliability Analysis of Au-Passivated Cu-Cu Fine-Pitch Thermocompression Bonding for 3-D IC Applications", IEEE Trans. Comp. Packag. Manufact. Technol., 9(7), 1227-1234 (2019). https://doi.org/10.1109/tcpmt.2019.2912891
  10. Y. P. Huang, Y. S. Chien, R. N. Tzeng, and K. N. Chen, "Demonstration and Electrical Performance of Cu-Cu Bonding at 150o C With Pd Passivation", IEEE Trans. Electron Devices, 62(8), 2587-2592 (2015). https://doi.org/10.1109/TED.2015.2446507
  11. Y. P. Huang, Y. S. Chien, R. N. Tzeng, M. S. Shy, T. H. Lin, K. H. Chen, C. T. Chiu, J. C. Chiou, C. T. Chuang, W. Hwang, H. M. Tong, and K. N. Chen, "Novel Cu-to-Cu Bonding With Ti Passivation at 180℃ in 3-D Integration", IEEE Electron Dev. Lett., 34(12), 1551-1553 (2013). https://doi.org/10.1109/LED.2013.2285702
  12. K. Panigrahi, S. Bonam, T. Ghosh, S. G. Singh, and S. R. K. Vanjari, "Ultra-thin Ti Passivation mediated breakthrough in high quality Cu-Cu bonding at Low Temperature and pressure", Mater. Lett., 169, 269-272 (2016). https://doi.org/10.1016/j.matlet.2016.01.126
  13. K. Panigrahi, S. Bonam, T. Ghosh, S. R. K. Vanjari, and S. G. Singh, "High quality fine-pitch Cu-Cu Wafer-on-Wafer bonding with optimized Ti passivation at 160℃", 2016 IEEE 66th ECTC, 1791-1796 (2016).
  14. K. Panigrahi, T. Ghosh, S. R. K. Vanjari, and S. G. Singh, "Demonstration of sub 150℃ Cu-Cu thermocompression bonding for 3D IC applications, utilzing an ultra-thin layer of Manganin alloy as an effective surface passivation layer", Mater. Lett., 194, 86-89 (2017). https://doi.org/10.1016/j.matlet.2017.02.041
  15. K. Panigrahi, T. Ghosh, S. R. K. Vanjari, and S. G. Singh, "Oxidation Resistive, CMOS Compatible Copper-Based Alloy Ultrahin Films as a Superior Passivation Mechanism for Achieving 150℃ Cu-Cu Wafer on Wafer Thermocompression Bonding", IEEE Trans. Electron Devices, 64(3), 1239-1245 (2017). https://doi.org/10.1109/TED.2017.2653188
  16. R. Gao, J. Li, Y. A. Shen, and H. Nishikawa, "A Cu-Cu Bonding Method Using Preoxidized Cu Microparticles under Formic Acid Atmosphere", 2019 IEEE ICEP, 159-162 (2019).
  17. W. F. Gale, and T. C. Totemeir, "Smithells Metals Reference Book", Elsevier (2013).
  18. S. Tsukimoto, T. Kabe, K. Ito, and M. Murakami, "Effect of Annealing Ambient on the Self-Formation Mechnism of Diffusion Barrier Layer Used in Cu(Ti) Interconnects", J. Electron. Mater., 36(3), 258-265 (2007). https://doi.org/10.1007/s11664-007-0094-8
  19. E. Gemelli, N. H. A. Camargo, "Oxidation kinetics of commercially pure titanium", Revista Materia, 12(3), 525-531 (2007). https://doi.org/10.1590/S1517-70762007000300014
  20. Y. Iijima, K. Hoshino, and K. I. Hirano, "Diffusion of Titanium in Copper", Metall. Trans. A 8.6, 997-1001 (1977). https://doi.org/10.1007/BF02661585
  21. Taguchi, and Y. Iijima, "Diffusion of copper, silver and gold in α-titanium", Philos. Mag. A, 72(6), 1649-1655 (1995). https://doi.org/10.1080/01418619508243935
  22. H. Mehrer, "Diffusion in Solid: fundamentals, methods, materials, diffusion-controlled processes", Springer Science and Business Media, 155 (2007).
  23. S. Bokstein, V. I. Vunkov, E. V. Golosov, M. I. Karpov, Y. R. Kolobov, D. A. Kolesnikov, V. P. Korzhov, and A. O. Rodin, "Structure and Diffusion Processes in Laminated Composites of a Cu-Ti System", Russ. Phys. J., 52(8), 811-815 (2009). https://doi.org/10.1007/s11182-010-9313-5
  24. K. Y. Lim, Y. S. Lee, Y. D. Chung, I. W. Lyo, C. N. Whang, J. Y. Won, and H. J. Kang, "Grain Boundary Diffusion of Cu in TiN Film by X-ray Photoelectron Spectroscopy", Appl. Phys. A, 70(4), 431-434 (2000). https://doi.org/10.1007/s003390051062
  25. Q. Jiang, S. H. Zhang, and J. C. Li, "Grain Size-dependent Diffusion Activation Energy in Nanomaterials", Solid State Commun., 130(9), 581-584 (2004). https://doi.org/10.1016/j.ssc.2004.03.033