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Micromachines 2017, 8(5), 158; doi:10.3390/mi8050158

Investigation of Au/Si Eutectic Wafer Bonding for MEMS Accelerometers

1,2,3,* , 1,2,3
,
1,2
and
1,2
1
National Key Laboratory of Fundamental Science of Novel Micro/Nano Device and System Technology, Chongqing University, Chongqing 400030, China
2
Key Laboratory of Optoelectronic Technologyand System of the Education Ministry of China, Chongqing University, Chongqing 400030, China
3
Center for Inteligent Sensing Tchnology, College of Optoelectronic Engineering, Chongqing University, Chongqing 400030, China
*
Author to whom correspondence should be addressed.
Academic Editors: Frank Niklaus and Roy Knechtel
Received: 21 December 2016 / Revised: 2 May 2017 / Accepted: 9 May 2017 / Published: 15 May 2017
(This article belongs to the Special Issue 3D Integration Technologies for MEMS)
View Full-Text   |   Download PDF [3581 KB, uploaded 15 May 2017]   |  

Abstract

Au/Si eutectic bonding is considered to BE a promising technology for creating 3D structures and hermetic packaging in micro-electro-mechanical system (MEMS) devices. However, it suffers from the problems of a non-uniform bonding interface and complex processes for the interconnection of metal wires. This paper presents a novel Au/Si eutectic wafer bonding structure and an implementation method for MEMS accelerometer packaging. The related processing parameters influencing the Au/Si eutectic bonding quality were widely investigated. It was found that a high temperature of 400 °C with a low heating/cooling rate of 5 °C/min is crucial for successful Au/Si eutectic bonding. High contact force is beneficial for bonding uniformity, but the bonding strength and bonding yield decrease when the contact force increases from 3000 to 5000 N due to the metal squeezing out of the interface. The application of TiW as an adhesion layer on a glass substrate, compared with a commonly used Cr or Ti layer, significantly improves the bonding quality. The bonding strength is higher than 50 MPa, and the bonding yield is above 90% for the presented Au/Si eutectic bonding. Furthermore, the wafer-level vacuum packaging of the MEMS accelerometer was achieved based on Au/Si eutectic bonding and anodic bonding with one process. Testing results show a nonlinearity of 0.91% and a sensitivity of 1.06 V/g for the MEMS accelerometer. This Au/Si eutectic bonding process can be applied to the development of reliable, low-temperature, low-cost fabrication and hermetic packaging for MEMS devices. View Full-Text
Keywords: heating/cooling rate; contact force; adhesion layer; bonding strength; bonding interface; wafer-level packaging heating/cooling rate; contact force; adhesion layer; bonding strength; bonding interface; wafer-level packaging
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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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Li, D.; Shang, Z.; She, Y.; Wen, Z. Investigation of Au/Si Eutectic Wafer Bonding for MEMS Accelerometers. Micromachines 2017, 8, 158.

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