Hostname: page-component-7bb8b95d7b-wpx69 Total loading time: 0 Render date: 2024-09-11T15:23:29.220Z Has data issue: false hasContentIssue false
  • English
  • Français

Fluxless Bonding Using Vacuum Ultraviolet and Formic Acid for 3D Interconnects

Published online by Cambridge University Press:  01 February 2011

Katsuyuki Sakuma ,
Naoko Unami ,
shuichi Shoji  and
Jun Mizuno
Katsuyuki Sakuma
Affiliation:
[email protected], IBM, Tokyo Research Laboratory, 1623-14, shimotsuruma, Yamato, Kanagawa, 2428502, Japan, 81-46-215-4255, 81-46-273-7413
Naoko Unami
Affiliation:
[email protected], Waseda University, Tokyo, Japan
shuichi Shoji
Affiliation:
[email protected], Waseda University, Tokyo, Japan
Jun Mizuno
Affiliation:
[email protected], Waseda University, Tokyo, Japan
Get access

Abstract

We have developed a novel surface treatment process using vacuum ultraviolet (VUV) light with a wavelength of 172 nm and formic acid vapor. A previous study showed that the VUV process can help remove the organic contaminants on the bonding surfaces and improve the shear strength. This new work focuses on studying the effects of VUV/O3 and formic acid treatments. The formic acid (HCOOH) vapor removes the metal oxides from the surfaces before the bonding process. Evaporated Cu/Sn and immersion Au were used for the bonding micro-bumps and bonding pads in our evaluations. Different cleaning conditions with VUV/O3, formic acid vapor, or both were compared and evaluated. X-ray Photoelectron Spectroscopy (XPS) was used to study the surface elemental composition of the micro-bumps and pad surfaces before and after the cleaning process. The photoelectron spectra of C1s, Sn3d, and Au4f were obtained with XPS. The XPS results showed the atomic carbon concentrations were significantly decreased by the VUV/O3 treatment process, while the Sn and Au concentrations were increased by the VUV/O3 and formic acid treatment because of the removal of the organic contaminants and metal oxides from the surfaces. The bonding strength of the Cu/Sn bumps was evaluated using a shear test tool. The results shows that the combination of VUV/O3 and formic acid treatment obtains the highest average shear strength among the treatments tested, with a shear strength almost 2.5 times stronger than the untreated samples.

Keywords

bondingpackagingx-ray photoelectron spectroscopy (XPS)
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1249: Symposia E/F – Advanced Interconnects and Chemical Mechanical Planarization for Micro-and Nanoelectronics , 2010 , 1249-F09-04
Copyright
Copyright © Materials Research Society 2010

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

1 Sakuma, K. Nagai, N. Mizuno, J. and Shoji, S.., “Vacuum Ultraviolet (VUV) Surface treatment Process for Flip Chip and 3-D Interconnections,” Electronic Components and Technology Conference (ECTC), pp.641–647, 2009.Google Scholar
2 Nah, J-W. et al., “Investigation of Flip Chip Under Bump Metallization Systems of Cu Pads,” IEEE Transactions on Components and Packaging Technologies, Vol. 25, No.1, 2002.Google Scholar
3 Koyanagi, M. Kurino, H. Lee, K.W. Sakuma, K. Miyakawa, N. and Itani, H. “Future Systemon-Silicon LSI chips,” IEEE MICRO, Vol 18, no. 4, pp.17–22, Jul/Aug. (1998).Google Scholar
4 Ramm, P. Klumpp, A. Merkel, R. Weber, J. Wieland, R. Ostmann, A. and Wolf, J. “3D System Integration Technologies,” Materials Research Society Symposium Proceedings, Boston, (2003).Google Scholar
5 Knickerbocker, J.U. et al., “Three-dimensional silicon integration,” IBM J. Res. & Dev. 52, No. 6, pp. 553–570 (2008).Google Scholar
6 Sakuma, K. et al., “3D Chip Stacking Technology with Low-Volume Lead-Free Interconnections,” Proceedings of the 57th Electronic Components and Technology Conference (ECTC), pp. 627–632, 2007.Google Scholar
7 Ohara, Y. et al., “10 μm pitch Fine Pitch Cu/Sn Micro-Bumps for 3-D Super-Chip Stack,” International 3D System Integration Conference (3D-SIC), 2009.Google Scholar
8 Sakuma, K. et al., “IMC bonding for 3D Interconnection,” to be published in Electronic Components and Technology Conference (ECTC), 2010.Google Scholar
9 et, Y. H. Chan al., “Improvements in Au Wire Bondability of Rigid and Flexible Substrates using Plasma Cleaning,,” IEEE International Conference on Electronic Packaging Technology, 2005 Google Scholar
10 Nicolussi, G. and Beck, E. “Plasma Chemical Cleaning of Chip Carrier in a Downstream Hollow Cathode Discharge,” IEEE advanced semiconductor manufacturing conference, pp172–176, 2002.Google Scholar
11 Koo, J-M et al., “Atmospheric Pressure Plasma Cleaning of Gold Flip Chip Bump for Ultrasonic Flip Chip Bonding,” Journal of Physics: Conf. Ser. 100 012034, 2008 Google Scholar
12 Lin, W. and Lee, Y. C. “Study of Fluxless Soldering Using Formic Acid Vapor,” IEEE Transactions on Advanced Packaging, Vol.,22, No. 4, Nov., 1999 Google Scholar
13 Nordin, R. A. et al., “High performance optical data link array technology,” in Proc. 43rd Electron. Comp. Technol. Comp., 1993.Google Scholar
14 Sakuma, K. Mizuno, J. Nagai, N. Unami, N. and Shoji, S. “Effects of Vacuum Ultraviolet Surface Treatment on the Bonding Interconnections for Flip Chip and 3-D Integration,” to be published in IEEE transactions on Electronics Packaging Manufacturing, 2010.Google Scholar