Surface activated bonding

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Surface activated bonding (SAB) is a non-high-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]

Contents

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
SiGeGaAsSiCCuAl2O3SiO2
Si [3] [4] [5] [6] [7] [8]
Ge [9]
GaAs [5] [10]
SiC [6] [10] [11]
Cu [12] [13]
Al2O3 [7] [8] [7]
SiO2Failure [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 layerReferences
SiO2-SiO2Sputtered Fe-Si on SiO2 [14]
Polymer filmsSputtered Fe-Si on both sides [15] [16] [17]
Si-SiCSputtered Si on SiC [18]
Si-SiO2Sputtered 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 interfaceReferences
SiO2-SiO2Direct bond interface [20]
Cu-Cu, SiO2-SiO2, SiO2-SiNxdirect 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)

Related Research Articles

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References

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  11. 1 2 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. 1 2 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. S2CID   98719282.
  13. 1 2 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. S2CID   27663896.
  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 doi : 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 doi : 10.7567/JJAP.54.101602
  16. 1 2 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. Bibcode:2013ECSTr..50g.297M. doi:10.1149/05007.0297ecst. ISSN   1938-6737.
  17. 1 2 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". 2015 IEEE 65th Electronic Components and Technology Conference (ECTC). pp. 700–704. doi:10.1109/ECTC.2015.7159668. ISBN   978-1-4799-8609-5. S2CID   11395361.
  18. 1 2 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. S2CID   124719605.
  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 doi : 10.7567/JJAP.55.05FL01
  20. 1 2 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. S2CID   123656692.
  21. 1 2 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. S2CID   101149612.
  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 . S2CID   119520218.
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