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.

Overview

In the standard SAB method, wafer surfaces are activated by argon fast atom bombardment in ultra-high vacuum (UHV) of 10⁻⁶–10⁻⁷ 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.

Technical Specifications

Materials	Semiconductor: Si-Si,[1][2] Ge-Ge,[3] GaAs-SiC,[4] SiC-SiC,[5] Si-SiC,[6][7] etc. Metal: Al, Cu-Cu,[8][9] etc. Dielectric: Polymer films,[10][11] SiO2,[12][13] etc.
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 Process compatibility to semiconductor technology
Drawbacks	High vacuum level

References

1. 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. doi:10.1063/1.115865. ISSN 0003-6951.
2. Wang, Chenxi; Suga, Tadatomo (2011-05-01). "Room-Temperature Direct Bonding Using Fluorine Containing Plasma Activation". Journal of The Electrochemical Society 158 (5): H525–H529. doi:10.1149/1.3560510. ISSN 0013-4651.
3. 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). doi:10.7567/jjap.54.030213.
4. 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). doi:10.7567/jjap.54.030207.
5. Suga, Tadatomo; Mu, Fengwen; Fujino, Masahisa; Takahashi, Yoshikazu; Nakazawa, Haruo; Iguchi, Kenichi (2015-03-01). "Silicon carbide wafer bonding by modified surface activated bonding method". Japanese Journal of Applied Physics 54 (3). doi:10.7567/jjap.54.030214.
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. doi:10.1063/1.4873113. ISSN 0003-6951.
7. 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). doi:10.7567/jjap.55.04ec09.
8. 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. doi:10.1116/1.1537716. ISSN 0734-2101.
9. 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.
10. 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.
11. 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.
12. 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). doi:10.7567/jjap.55.04ec02.
13. 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). doi:10.7567/jjap.54.030218.