J. Semicond. > 2013, Volume 34 > Issue 10 > 106001
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SEMICONDUCTOR TECHNOLOGY

Low temperature Sn-rich Au-Sn wafer-level bonding

Zhiqiang Fang1, 2, Xu Mao1, 2, Jinling Yang1, 2, and Fuhua Yang1

+ Author Affiliations

 Corresponding author: Yang Jinling, jlyang@semi.ac.cn

DOI: 10.1088/1674-4926/34/10/106001

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Abstract: Sn-rich Au-Sn solder bonding has been systematically investigated for low cost and low temperature wafer-level packaging of high-end MEMS devices. The AuSn2 phase with the highest Vickers-hardness among the four stable intermetallic compounds of the Au-Sn system makes a major contribution to the high bonding shear strength. The maximum shear strength of 64 MPa and a leak rate lower than 4.9×10-7 atm·cc/s have been obtained for Au46Sn54 solder bonded at 310℃. This wafer-level low cost bonding technique with high bonding strength can be applied to MEMS devices requiring low temperature packaging.

Key words: MEMS packaging, Au-Sn solder, Sn-rich, bonding strength



[1]
McNulty J C. Processing and reliability issues for eutectic AuSn solder joint. 41st Int Symp on Microelectronics, 2008:909
[2]
Oppermann H. The role of Au/Sn solder in packaging engineering materials and processes:materials for information technology devices, interconnects and packaging. London:Springer, 2006:377
[3]
Okamoto H, Massatski T B. Monograph series on alloy phase diagrams:phase diagram of binary gold alloys. Metals Park, OH:ASM International, 1987
[4]
Kim D, Kim J, Wang G L, et al. Nucleation and growth of intermetallics and gold clusters on thick tin layers in electroplating process. Mater Sci Eng A, 2005, 393:315 doi: 10.1016/j.msea.2004.11.022
[5]
Matijasevic G S, Lee C C, Wang C Y. Au-Sn alloy phase diagram and properties related to its use as a bonding medium. Thin Solid Films, 1993, 223:276 doi: 10.1016/0040-6090(93)90533-U
[6]
Lee C C, Chuang R W. Fluxless non-eutectic joints fabricated using gold-tin multilayer composite. IEEE Trans Comp Packag Technol, 2003, 26:416 doi: 10.1109/TCAPT.2003.815109
[7]
Kim J S, Wang P J, Lee C C. Fluxless hermetic lid sealing using electroplated Sn-rich solder. IEEE Trans Comp Packag Technol, 2008, 31:719 doi: 10.1109/TCAPT.2008.922000
[8]
Chromik R R, Wang D N, Shugar A, et al. Mechanical properties of intermetallic compounds in the Au-Sn system. J Mater Res, 2005, 20:2161 doi: 10.1557/JMR.2005.0269
[9]
Buene L, Falkenberg-Arell H, Gjonnes J, et al. A study of evaporated gold-tin films using transmission electron microscopy:Ⅱ. Thin Solid Films, 1980, 67:95 doi: 10.1016/0040-6090(80)90292-8
[10]
Nakahara S, McCoy R J, Buene L, et al. Room temperature interdiffusion studies of Au/Sn thin film couples. Thin Solid Films, 1981, 84:185 doi: 10.1016/0040-6090(81)90468-5
Fig. 1.  Au-Sn binary equilibrium phase diagram[3].

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Fig. 2.  Fabrication process flow of the substrate and cap wafers.

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Fig. 3.  Optical images of the bonded (a) glass-silicon wafers and (b) glass-glass wafers with Au-Sn solder.

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Fig. 4.  Dependence of shear strengths on Sn content for the joints bonded at 310 ℃ for 60 min and under a static pressure of 7 MPa. The average is done for four experimental data.

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Fig. 5.  XRD spectrums for the interlayer with Au : Sn weight ratio: (a) 80 : 20, (b) 30 : 70, and (c) 46 : 54 bonded at 310 ℃.

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Fig. 6.  Dependence of shear strengths on temperature for the joint with Au : Sn weight ratio of 46 : 54 bonded for 60 min under a static pressure of 7 MPa. The average is done for four experimental data.

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Fig. 7.  SEM image for the cross section of the glass-silicon sample bonded under 7 MPa at 310 ℃ for 60 min.

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Table 1.   Shear strengths of solder joints bonded at 310 ℃ for 60 min.
[1]
McNulty J C. Processing and reliability issues for eutectic AuSn solder joint. 41st Int Symp on Microelectronics, 2008:909
[2]
Oppermann H. The role of Au/Sn solder in packaging engineering materials and processes:materials for information technology devices, interconnects and packaging. London:Springer, 2006:377
[3]
Okamoto H, Massatski T B. Monograph series on alloy phase diagrams:phase diagram of binary gold alloys. Metals Park, OH:ASM International, 1987
[4]
Kim D, Kim J, Wang G L, et al. Nucleation and growth of intermetallics and gold clusters on thick tin layers in electroplating process. Mater Sci Eng A, 2005, 393:315 doi: 10.1016/j.msea.2004.11.022
[5]
Matijasevic G S, Lee C C, Wang C Y. Au-Sn alloy phase diagram and properties related to its use as a bonding medium. Thin Solid Films, 1993, 223:276 doi: 10.1016/0040-6090(93)90533-U
[6]
Lee C C, Chuang R W. Fluxless non-eutectic joints fabricated using gold-tin multilayer composite. IEEE Trans Comp Packag Technol, 2003, 26:416 doi: 10.1109/TCAPT.2003.815109
[7]
Kim J S, Wang P J, Lee C C. Fluxless hermetic lid sealing using electroplated Sn-rich solder. IEEE Trans Comp Packag Technol, 2008, 31:719 doi: 10.1109/TCAPT.2008.922000
[8]
Chromik R R, Wang D N, Shugar A, et al. Mechanical properties of intermetallic compounds in the Au-Sn system. J Mater Res, 2005, 20:2161 doi: 10.1557/JMR.2005.0269
[9]
Buene L, Falkenberg-Arell H, Gjonnes J, et al. A study of evaporated gold-tin films using transmission electron microscopy:Ⅱ. Thin Solid Films, 1980, 67:95 doi: 10.1016/0040-6090(80)90292-8
[10]
Nakahara S, McCoy R J, Buene L, et al. Room temperature interdiffusion studies of Au/Sn thin film couples. Thin Solid Films, 1981, 84:185 doi: 10.1016/0040-6090(81)90468-5

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    Received: 07 March 2013 Revised: 20 March 2013 Online: Published: 01 October 2013

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      Article Navigation >  Journal of Semiconductors  > 2013  >  34(10): 106001
      Zhiqiang Fang, Xu Mao, Jinling Yang, Fuhua Yang. Low temperature Sn-rich Au-Sn wafer-level bonding[J]. Journal of Semiconductors, 2013, 34(10): 106001. doi: 10.1088/1674-4926/34/10/106001 ****Z Q Fang, X Mao, J L Yang, F H Yang. Low temperature Sn-rich Au-Sn wafer-level bonding[J]. J. Semicond., 2013, 34(10): 106001. doi: 10.1088/1674-4926/34/10/106001.
      Citation:
      Zhiqiang Fang, Xu Mao, Jinling Yang, Fuhua Yang. Low temperature Sn-rich Au-Sn wafer-level bonding[J]. Journal of Semiconductors, 2013, 34(10): 106001. doi: 10.1088/1674-4926/34/10/106001 ****
      Z Q Fang, X Mao, J L Yang, F H Yang. Low temperature Sn-rich Au-Sn wafer-level bonding[J]. J. Semicond., 2013, 34(10): 106001. doi: 10.1088/1674-4926/34/10/106001.
      shu

      Low temperature Sn-rich Au-Sn wafer-level bonding

      DOI: 10.1088/1674-4926/34/10/106001
      • 1.

        Research Center of Engineering for Semiconductor Integrated Technology, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China

      • 2.

        State Key Laboratory of Transducer Technology, Shanghai 200050, China

      Funds:

      the State Key Development Program for Basic Research of China 2009CB320305

      Project supported by the State Key Development Program for Basic Research of China (Nos. 2009CB320305, 2011CB933102) and the National Natural Science Foundation of China (Nos. 61234007, 61201104, 61274001)

      the National Natural Science Foundation of China 61274001

      the State Key Development Program for Basic Research of China 2011CB933102

      the National Natural Science Foundation of China 61234007

      the National Natural Science Foundation of China 61201104

      More Information
      • Corresponding author: Yang Jinling, jlyang@semi.ac.cn
      • Received Date: 2013-03-07
      • Revised Date: 2013-03-20
      • Published Date: 2013-10-01

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