Surface activated bonding

Surface activated bonding (SAB) is a low temperature wafer bonding technology with atomically clean and activated surfaces. Surface activation prior to bonding by using fast atom bombardment is typically employed to clean the surfaces. High strength bonding of semiconductor, metal, and dielectric can be obtained even at room temperature.[1][2]

Overview

In the standard SAB method, wafer surfaces are activated by argon fast atom bombardment in ultra-high vacuum (UHV) of 10−4–10−7 Pa. The bombardment removes adsorbed contaminants and native oxides on the surfaces. The activated surfaces are atomically clean and reactive for formation of direct bonds between wafers when they are brought into contact even at room temperature.

Researches on SAB

The SAB method has been studied for bonding of various materials, as shown in Table I.

Table I. Studies of standard SAB for various materials
Si Ge GaAs SiC Cu Al2O3 SiO2
Si [3][4] [5] [6] [7][8]
Ge [9]
GaAs [5] [10]
SiC [6] [10] [11]
Cu [12][13]
Al2O3 [7][8] [7]
SiO2 Failure[7]

The standard SAB, however, failed to bond some materials such as SiO2 and polymer films. The modified SAB was developed to solve this problem, by using a sputtering deposited Si intermediate layer to improve the bond strength.

Table II. Modified SAB with Si intermediate layer
Bonding intermediate layer References
SiO2-SiO2 Sputtered Fe-Si on SiO2 [14]
Polymer films Sputtered Fe-Si on both sides [15][16][17]
Si-SiC Sputtered Si on SiC [18]
Si-SiO2 Sputtered Si on SiO2 [19]

The combined SAB has been developed for SiO2-SiO2 and Cu/SiO2 hybrid bonding, without use of any intermediate layer.

Table III. Combined SAB using Si-containing Ar beam
Bond interface References
SiO2-SiO2 Direct bond interface [20]
Cu-Cu, SiO2-SiO2, SiO2-SiNx direct bond interface [21]

Technical Specifications
Materials
Advantages
  • Low process temperature: room temperature–200 °C
  • No concerns of thermal stress and damages
  • High bonding quality
  • Semiconductor and metal bonding interfaces without oxides
  • Completely dry process without wet chemical cleaning
  • Process compatibility to semiconductor technology
Drawbacks
  • High vacuum level (10−4–10−7 Pa)
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References
  1. "Room Temperature Wafer Bonding Machine BOND MEISTER｜Mitsubishi Heavy Industries Machine Tool Co., Ltd". www.mhi-machinetool.com.
  2. Ltd, Mitsubishi Heavy Industries. "MHI Develops World's First 12-inch Wafer Bonding Machine | Mitsubishi Heavy Industries, Ltd. Global Website". Mitsubishi Heavy Industries, Ltd.
  3. Takagi, H.; Kikuchi, K.; Maeda, R.; Chung, T. R.; Suga, T. (1996-04-15). "Surface activated bonding of silicon wafers at room temperature". Applied Physics Letters. 68 (16): 2222–2224. Bibcode:1996ApPhL..68.2222T. doi:10.1063/1.115865. ISSN 0003-6951.
  4. Wang, Chenxi; Suga, Tadatomo (2011-05-01). "Room-Temperature Direct Bonding Using Fluorine Containing Plasma Activation" (PDF). Journal of the Electrochemical Society. 158 (5): H525–H529. doi:10.1149/1.3560510. ISSN 0013-4651.
  5. J. Liang, T. Miyazaki, M. Morimoto, S. Nishida, N. Watanabe, and N. Shigekawa, “Electrical Properties of p-Si/n-GaAs Heterojunctions by Using Surface-Activated Bonding,” Appl. Phys. Express, vol. 6, no. 2, p. 021801, Feb. 2013. Available: http://dx.doi.org/10.7567/APEX.6.021801
  6. Liang, J.; Nishida, S.; Arai, M.; Shigekawa, N. (2014-04-21). "Effects of thermal annealing process on the electrical properties of p+-Si/n-SiC heterojunctions". Applied Physics Letters. 104 (16): 161604. Bibcode:2014ApPhL.104p1604L. doi:10.1063/1.4873113. ISSN 0003-6951.
  7. H. Takagi, J. Utsumi, M. Takahashi, and R. Maeda, “Room-Temperature Bonding of Oxide Wafers by Ar-beam Surface Activation,” ECS Trans., vol. 16, no. 8, pp. 531–537, Oct. 2008. Available: http://dx.doi.org/10.1149/1.2982908
  8. Ichikawa, Masatsugu; Fujioka, Akira; Kosugi, Takao; Endo, Shinya; Sagawa, Harunobu; Tamaki, Hiroto; Mukai, Takashi; Uomoto, Miyuki; Shimatsu, Takehito (2016). "High-output-power deep ultraviolet light-emitting diode assembly using direct bonding". Applied Physics Express. 9 (7): 072101. Bibcode:2016APExp...9g2101I. doi:10.7567/apex.9.072101.
  9. Higurashi, Eiji; Sasaki, Yuta; Kurayama, Ryuji; Suga, Tadatomo; Doi, Yasuo; Sawayama, Yoshihiro; Hosako, Iwao (2015-03-01). "Room-temperature direct bonding of germanium wafers by surface-activated bonding method". Japanese Journal of Applied Physics. 54 (3): 030213. Bibcode:2015JaJAP..54c0213H. doi:10.7567/jjap.54.030213.
  10. Higurashi, Eiji; Okumura, Ken; Nakasuji, Kaori; Suga, Tadatomo (2015-03-01). "Surface activated bonding of GaAs and SiC wafers at room temperature for improved heat dissipation in high-power semiconductor lasers". Japanese Journal of Applied Physics. 54 (3): 030207. Bibcode:2015JaJAP..54c0207H. doi:10.7567/jjap.54.030207.
  11. Mu, F.; Iguchi, K.; Nakazawa, H.; Takahashi, Y.; Fujino, M.; Suga, T. (30 June 2016). "Direct Wafer Bonding of SiC-SiC by SAB for Monolithic Integration of SiC MEMS and Electronics". ECS Journal of Solid State Science and Technology. 5 (9): P451–P456. doi:10.1149/2.0011609jss.
  12. Kim, T. H.; Howlader, M. M. R.; Itoh, T.; Suga, T. (2003-03-01). "Room temperature Cu–Cu direct bonding using surface activated bonding method". Journal of Vacuum Science & Technology A. 21 (2): 449–453. Bibcode:2003JVST...21..449K. doi:10.1116/1.1537716. ISSN 0734-2101.
  13. Shigetou, A.; Itoh, T.; Matsuo, M.; Hayasaka, N.; Okumura, K.; Suga, T. (2006-05-01). "Bumpless interconnect through ultrafine Cu electrodes by means of surface-activated bonding (SAB) method". IEEE Transactions on Advanced Packaging. 29 (2): 218–226. doi:10.1109/TADVP.2006.873138. ISSN 1521-3323.
  14. R. Kondou and T. Suga, “Room temperature SiO2 wafer bonding by adhesion layer method,” presented at the Electronic Components and Technology Conference (ECTC), 2011 IEEE 61st, 2011, pp. 2165–2170. Available: http://dx.doi.org/10.1109/ECTC.2011.5898819
  15. T. Matsumae, M. Fujino, and T. Suga, “Room-temperature bonding method for polymer substrate of flexible electronics by surface activation using nano-adhesion layers,” Japanese Journal of Applied Physics, vol. 54, no. 10, p. 101602, Oct. 2015. Available: http://dx.doi.org/10.7567/JJAP.54.101602
  16. Matsumae, Takashi; Nakano, Masashi; Matsumoto, Yoshiie; Suga, Tadatomo (2013-03-15). "Room Temperature Bonding of Polymer to Glass Wafers Using Surface Activated Bonding (SAB) Method". ECS Transactions. 50 (7): 297–302. doi:10.1149/05007.0297ecst. ISSN 1938-6737.
  17. Takeuchi, K.; Fujino, M.; Suga, T.; Koizumi, M.; Someya, T. (2015-05-01). "Room temperature direct bonding and debonding of polymer film on glass wafer for fabrication of flexible electronic devices". Electronic Components and Technology Conference (ECTC) , 2015 IEEE 65th: 700–704. doi:10.1109/ECTC.2015.7159668. ISBN 978-1-4799-8609-5.
  18. Mu, Fengwen; Iguchi, Kenichi; Nakazawa, Haruo; Takahashi, Yoshikazu; Fujino, Masahisa; Suga, Tadatomo (2016-04-01). "Room-temperature wafer bonding of SiC–Si by modified surface activated bonding with sputtered Si nanolayer". Japanese Journal of Applied Physics. 55 (4S): 04EC09. Bibcode:2016JaJAP..55dEC09M. doi:10.7567/jjap.55.04ec09.
  19. K. Tsuchiyama, K. Yamane, H. Sekiguchi, H. Okada, and A. Wakahara, “Fabrication of Si/SiO2/GaN structure by surface-activated bonding for monolithic integration of optoelectronic devices,” Japanese Journal of Applied Physics, vol. 55, no. 5S, p. 05FL01, May 2016. Available: http://dx.doi.org/10.7567/JJAP.55.05FL01
  20. He, Ran; Fujino, Masahisa; Yamauchi, Akira; Suga, Tadatomo (2016-04-01). "Combined surface-activated bonding technique for low-temperature hydrophilic direct wafer bonding". Japanese Journal of Applied Physics. 55 (4S): 04EC02. Bibcode:2016JaJAP..55dEC02H. doi:10.7567/jjap.55.04ec02.
  21. He, Ran; Fujino, Masahisa; Yamauchi, Akira; Wang, Yinghui; Suga, Tadatomo (2016-01-01). "Combined Surface Activated Bonding Technique for Low-Temperature Cu/Dielectric Hybrid Bonding". ECS Journal of Solid State Science and Technology. 5 (7): P419–P424. doi:10.1149/2.0201607jss. ISSN 2162-8769.
  22. He, Ran; Fujino, Masahisa; Yamauchi, Akira; Suga, Tadatomo (2015-03-01). "Novel hydrophilic SiO2 wafer bonding using combined surface-activated bonding technique". Japanese Journal of Applied Physics. 54 (3): 030218. Bibcode:2015JaJAP..54c0218H. doi:10.7567/jjap.54.030218.
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