Wafer-level SLID bonding for MEMS encapsulation

H Xu (Corresponding Author), Tommi Suni, V Vuorinen, J Li, Hannele Heikkinen, Philippe Monnoyer, M Paulasto-Kröckel

Research output: Contribution to journalArticleScientificpeer-review

22 Citations (Scopus)

Abstract

Hermetic packaging is often an essential requirement to enable proper functionality throughout the device's lifetime and ensure the optimal performance of a micro electronic mechanical system (MEMS) device. Solid-liquid interdiffusion (SLID) bonding is a novel and attractive way to encapsulate MEMS devices at a wafer level. SLID bonding utilizes a low-melting-point metal to reduce the bonding process temperature; and metallic seal rings take out less of the valuable surface area and have a lower gas permeability compared to polymer or glass-based sealing materials. In addition, ductile metals can adopt mechanical and thermo-mechanical stresses during their service lifetime, which improves their reliability. In this study, the principles of Au-Sn and Cu-Sn SLID bonding are presented, which are meant to be used for wafer-level hermetic sealing of MEMS resonators. Seal rings in 15.24 cm silicon wafers were bonded at a width of 60 µm, electroplated, and used with Au-Sn and Cu-Sn layer structures. The wafer bonding temperature varied between 300 °C and 350 °C, and the bonding force was 3.5 kN under the ambient pressure, that is, it was less than 0.1 Pa. A shear test was used to compare the mechanical properties of the interconnections between both material systems. In addition, important factors pertaining to bond ring design are discussed according to their effects on the failure mechanisms. The results show that the design of metal structures can significantly affect the reliability of bond rings.
Original languageEnglish
Pages (from-to)226- 235
Number of pages9
JournalAdvances in Manufacturing
Volume1
Issue number3
DOIs
Publication statusPublished - 2013
MoE publication typeA1 Journal article-refereed

Keywords

  • MEMS
  • SLID bonding
  • TLP bonding
  • defects
  • shear test
  • reliability

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  • Cite this

    Xu, H., Suni, T., Vuorinen, V., Li, J., Heikkinen, H., Monnoyer, P., & Paulasto-Kröckel, M. (2013). Wafer-level SLID bonding for MEMS encapsulation. Advances in Manufacturing, 1(3), 226- 235. https://doi.org/10.1007/s40436-013-0035-0