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Micromachines 2018, 9(4), 174; https://doi.org/10.3390/mi9040174

Comprehensive Die Shear Test of Silicon Packages Bonded by Thermocompression of Al Layers with Thin Sn Capping or Insertions

1
Micro System Integration Center, Tohoku University, 6-6-01, Aoba, Aramaki, Aoba-ku, Sendai 980-3579, Japan
2
Graduate School of Engineering, Tohoku University, 6-6-01, Aoba, Aramaki, Aoba-ku, Sendai 980-3579, Japan
*
Author to whom correspondence should be addressed.
Received: 15 March 2018 / Revised: 5 April 2018 / Accepted: 8 April 2018 / Published: 11 April 2018
(This article belongs to the Special Issue Wafer Level Packaging of MEMS)
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Abstract

Thermocompression bonding for wafer-level hermetic packaging was demonstrated at the lowest temperature of 370 to 390 °C ever reported using Al films with thin Sn capping or insertions as bonding layer. For shrinking the chip size of MEMS (micro electro mechanical systems), a smaller size of wafer-level packaging and MEMS–ASIC (application specific integrated circuit) integration are of great importance. Metal-based bonding under the temperature of CMOS (complementary metal-oxide-semiconductor) backend process is a key technology, and Al is one of the best candidates for bonding metal in terms of CMOS compatibility. In this study, after the thermocompression bonding of two substrates, the shear fracture strength of dies was measured by a bonding tester, and the shear-fractured surfaces were observed by SEM (scanning electron microscope), EDX (energy dispersive X-ray spectrometry), and a surface profiler to clarify where the shear fracture took place. We confirmed two kinds of fracture mode. One mode is Si bulk fracture mode, where the die shear strength is 41.6 to 209 MPa, proportionally depending on the area of Si fracture. The other mode is bonding interface fracture mode, where the die shear strength is 32.8 to 97.4 MPa. Regardless of the fracture modes, the minimum die shear strength is practical for wafer-level MEMS packaging. View Full-Text
Keywords: thermocompression bonding; vacuum seal; Al–Al bonding; low temperature bonding; shear fracture strength; fracture mechanism; Sn thermocompression bonding; vacuum seal; Al–Al bonding; low temperature bonding; shear fracture strength; fracture mechanism; Sn
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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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Satoh, S.; Fukushi, H.; Esashi, M.; Tanaka, S. Comprehensive Die Shear Test of Silicon Packages Bonded by Thermocompression of Al Layers with Thin Sn Capping or Insertions. Micromachines 2018, 9, 174.

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