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Sensors 2016, 16(11), 1819; doi:10.3390/s16111819

Wafer-Level Vacuum Packaging of Smart Sensors

Electronics and Applied Physics Division, RTI International, Research Triangle Park, NC 27709, USA
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Academic Editor: Vittorio M. N. Passaro
Received: 16 August 2016 / Revised: 16 October 2016 / Accepted: 18 October 2016 / Published: 31 October 2016
(This article belongs to the Section Physical Sensors)
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Abstract

The reach and impact of the Internet of Things will depend on the availability of low-cost, smart sensors—“low cost” for ubiquitous presence, and “smart” for connectivity and autonomy. By using wafer-level processes not only for the smart sensor fabrication and integration, but also for packaging, we can further greatly reduce the cost of sensor components and systems as well as further decrease their size and weight. This paper reviews the state-of-the-art in the wafer-level vacuum packaging technology of smart sensors. We describe the processes needed to create the wafer-scale vacuum microchambers, focusing on approaches that involve metal seals and that are compatible with the thermal budget of complementary metal-oxide semiconductor (CMOS) integrated circuits. We review choices of seal materials and structures that are available to a device designer, and present techniques used for the fabrication of metal seals on device and window wafers. We also analyze the deposition and activation of thin film getters needed to maintain vacuum in the ultra-small chambers, and the wafer-to-wafer bonding processes that form the hermetic seal. We discuss inherent trade-offs and challenges of each seal material set and the corresponding bonding processes. Finally, we identify areas for further research that could help broaden implementations of the wafer-level vacuum packaging technology. View Full-Text
Keywords: wafer-level vacuum packaging; hermetic packaging; wafer-to-wafer bonding; smart sensors; microelectromechanical (MEMS); eutectic bonding; solid-liquid interdiffusion (SLID) bonding; metal-metal bonding; thin-film getter; AuSn; CuSn; AuSi; AlGe; AuIn wafer-level vacuum packaging; hermetic packaging; wafer-to-wafer bonding; smart sensors; microelectromechanical (MEMS); eutectic bonding; solid-liquid interdiffusion (SLID) bonding; metal-metal bonding; thin-film getter; AuSn; CuSn; AuSi; AlGe; AuIn
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Hilton, A.; Temple, D.S. Wafer-Level Vacuum Packaging of Smart Sensors. Sensors 2016, 16, 1819.

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