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Characterization of Low Temperature, Wafer-Level Gold-Gold Thermocompression Bonds

Published online by Cambridge University Press:  10 February 2011

Christine H. Tsau
Affiliation:
Massachusetts Institute of Technology, Cambridge, MA
Martin A. Schmidt
Affiliation:
Massachusetts Institute of Technology, Cambridge, MA
S. Mark Spearing
Affiliation:
Massachusetts Institute of Technology, Cambridge, MA
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Abstract

Low temperature, wafer-level bonding offers several advantages in MEMS packaging, such as device protection during aggressive processing/handling and the possibility of vacuum sealing. Although thermocompression bonding can be achieved with a variety of metals, gold is often preferred because of its acceptance in die bonding [1] and its resistance to oxidation. This study demonstrates that the simultaneous application of moderate pressure (0.5 MPa) and temperature (300°C) produces strong wafer-level bonds. A four-point benddelamination technique was utilized to quantify bond toughness. Test specimens exhibited constant load versus displacement behavior during steady state crack propagation. Two distinct fracture modes were observed: cohesive failure within the Au and adhesive failure at the Ti-Si interface. The strain energy release rate for Au-Au fracture was found to be higher than that associated with Ti-Si fracture, consistent with the greater plastic deformation that occurs in the metal during fracture.

Type
Research Article
Copyright
Copyright © Materials Research Society 2000

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