Wafer-Level AuSn/Pt Solid-Liquid Interdiffusion Bonding

Antti Rautiainen, Vesa Vuorinen, Hannele Heikkinen, Mervi Paulasto-Krockel

Research output: Contribution to journalArticleScientificpeer-review

1 Citation (Scopus)

Abstract

In this paper, wafer-level AuSn/Pt solid-liquid interdiffusion bonding for hermetic encapsulation of microelectromechanical systems (MEMS) is evaluated. Although AuSn is used for bonding of ICs, the implementation of AuSn diffusion bonding in MEMS applications requires thorough understanding of its compatibility with the complete layer stack including adhesion, buffer, and metallization layers. Partitioning of the layer stacks is possible in MEMS devices consisting of several silicon wafers since the device wafer carrying functional structures and the encapsulation wafer have different restrictions on process integration and applicable metal deposition techniques. In this paper, CMOS/MEMS compatible sputtered platinum is utilized on the device wafer as a contact metallization for Au-Sn metallized cap wafer. The role of the platinum layer thickness as well as the nickel and molybdenum buffer layers on mechanical reliability were tested. The mechanical shear and tensile tests were performed for samples after bonding as well as after high-temperature storage and thermal shock tests. The results were rationalized based on the combined microstructural, thermodynamic, and fracture surface analyses. High-strength and thermodynamically stable bonds were achieved, exhibiting shear strength up to $~ $180 MPa and tensile strength up to $~ $80 MPa. Platinum was consumed completely during bonding and was observed to dissolve mainly into the (Au,Pt)Sn phase. Thicker platinum layer (200 versus 100 nm) increased the (Au,Pt)Sn phase thickness and resulted in higher strength. The molybdenum buffer layer under the platinum metallization increased the tensile strength significantly.

Original languageEnglish
Article number8248642
Pages (from-to)169-176
Number of pages8
JournalIEEE Transactions on Components, Packaging and Manufacturing Technology
Volume8
Issue number2
DOIs
Publication statusPublished - 1 Feb 2018
MoE publication typeA1 Journal article-refereed

Fingerprint

Interdiffusion (solids)
Platinum
MEMS
Metallizing
Liquids
Molybdenum
Buffer layers
Encapsulation
Tensile strength
Diffusion bonding
Thermal shock
Nickel
Silicon wafers
Shear strength
Buffers
Adhesion
Metals
Thermodynamics

Keywords

  • Au-Sn-Pt system
  • Bonding
  • Gold
  • intermetallic comp- ounds (IMCs)
  • Metallization
  • Micromechanical devices
  • Molybdenum
  • Platinum
  • remelting temperature
  • solid-liquid interdiffu- sion (SLID) bonding.

Cite this

Rautiainen, Antti ; Vuorinen, Vesa ; Heikkinen, Hannele ; Paulasto-Krockel, Mervi. / Wafer-Level AuSn/Pt Solid-Liquid Interdiffusion Bonding. In: IEEE Transactions on Components, Packaging and Manufacturing Technology. 2018 ; Vol. 8, No. 2. pp. 169-176.
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Rautiainen, A, Vuorinen, V, Heikkinen, H & Paulasto-Krockel, M 2018, 'Wafer-Level AuSn/Pt Solid-Liquid Interdiffusion Bonding', IEEE Transactions on Components, Packaging and Manufacturing Technology, vol. 8, no. 2, 8248642, pp. 169-176. https://doi.org/10.1109/TCPMT.2017.2780102

Wafer-Level AuSn/Pt Solid-Liquid Interdiffusion Bonding. / Rautiainen, Antti; Vuorinen, Vesa; Heikkinen, Hannele; Paulasto-Krockel, Mervi.

In: IEEE Transactions on Components, Packaging and Manufacturing Technology, Vol. 8, No. 2, 8248642, 01.02.2018, p. 169-176.

Research output: Contribution to journalArticleScientificpeer-review

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KW - Bonding

KW - Gold

KW - intermetallic comp- ounds (IMCs)

KW - Metallization

KW - Micromechanical devices

KW - Molybdenum

KW - Platinum

KW - remelting temperature

KW - solid-liquid interdiffu- sion (SLID) bonding.

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