Surface Activated Bonding (SAB)
www.3dic.org/Surface activated bonding (SAB)
Surface activated bonding (SAB) is a low temperature wafer bonding technology with atomically clean and activated surfaces. Surface activation prior to bonding by using Ar beam bombardment is typically employed to clean and activate the surfaces. High strength bonding of semiconductor, metal, and dielectric can be obtained at <200°C or even at room temperature.
In the standard SAB method, wafer surfaces are activated by Ar 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.
Modified SAB using Si intermediate layer
The standard SAB failed to bond some merterials such as SiO2 and polymer films. The modified SAB was developed to solve this problem, by using a sputtering deposted Si intermediate layer to improve the bond stregnth.
|Bonding intermediate layer||References|
|SiO2-SiO2||Sputtered Fe-Si on SiO2|||
|Polymer films||Sputtered Fe-Si on both sides|||
|Si-SiC||Sputtered Si on SiC|||
|Si-SiO2||Sputtered Si on SiO2|||
Combined SAB for Cu/SiO2 hybrid bonding
The combined surface activated bonding (SAB) technique is developed for Cu/SiO2 hybrid bonding without any intermediate layer. This technique employs a combination of surface irradiation using a Si-containing Ar beam and prebonding attach-detach procedure prior to bonding in vacuum, followed by postbonding annealing in ambient pressure. The bonding method has also been found effective for SiO2-SiO2, SiO2-SiNx, and Cu-Cu bonding at 200°C.  The benefits of the combined SAB are low bonding temperature, excellent bond strength of dielectric-dielectric (SiO2-SiO2 and SiO2-SiNx) and Cu-Cu bonds for Cu/dielectric hybrid bonding, and absence of any deposited intermediate layer.
|SiO2-SiO2||direct bond interface|||
|SiO2-SiNx||direct bond interface|||
|Cu-Cu||direct bond interface|||
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- 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
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- 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
- R. He, M. Fujino, A. Yamauchi, and T. Suga, “Combined surface-activated bonding technique for low-temperature hydrophilic direct wafer bonding,” Japanese Journal of Applied Physics, vol. 55, no. 4S, p. 04EC02, Apr. 2016. Available: http://dx.doi.org/10.7567/JJAP.55.04EC02
- R. He, M. Fujino, A. Yamauchi, Y. Wang, and T. Suga, “Combined Surface Activated Bonding Technique for Low-Temperature Cu/Dielectric Hybrid Bonding,” ECS Journal of Solid State Science and Technology, vol. 5, no. 7, pp. P419–P424, 2016. Available: http://dx.doi.org/10.1149/2.0201607jss