A Method for Wafer-Scale Encapsulation of Large Lateral Deflection MEMS Devices

Packaging of microelectromechanical systems (MEMS) is a critical step in the transition from development to commercialized product. This paper presents a thin-film encapsulation process that allows varying trench widths suitable for MEMS devices with lateral deflections as large as 20 ¿m. The proces...

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Bibliographic Details
Published in:Journal of microelectromechanical systems 2010-02, Vol.19 (1), p.28-37
Main Authors: Graham, A.B., Messana, M.W., Hartwell, P.G., Provine, J., Yoneoka, S., Melamud, R., Bongsang Kim, Howe, R.T., Kenny, T.W.
Format: Article
Language:English
Subjects:
Applied sciences
Commercialization
Cross-disciplinary physics: materials science
rheology
Deflection
Deposition
Devices
Electronics
Electrostatic devices
Encapsulation
Exact sciences and technology
Hafnium
Instruments, apparatus, components and techniques common to several branches of physics and astronomy
Materials science
Mechanical engineering. Machine design
Mechanical instruments, equipment and techniques
Methods of deposition of films and coatings
film growth and epitaxy
Microelectromechanical devices
Microelectromechanical systems
Microelectronic fabrication (materials and surfaces technology)
Microelectronics
micromachining
Micromechanical devices
Micromechanical devices and systems
Packaging
Physics
Planarization
Precision engineering, watch making
Resonators
Sealing
Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
Sensors
Thin film devices
Trenches
Wire
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Description
Summary:Packaging of microelectromechanical systems (MEMS) is a critical step in the transition from development to commercialized product. This paper presents a thin-film encapsulation process that allows varying trench widths suitable for MEMS devices with lateral deflections as large as 20 ¿m. The process involves the deposition and planarization of a sacrificial-oxide layer of up to 23 ¿m thick, the deposition of a 20 ¿m epitaxial-silicon sealing cap, the release of structures using hydrofluoric acid (HF) vapor, and the sealing of the structure at low pressure. Devices produced using this encapsulation method are capable of surviving standard backend processes such as wafer singulation and wire bonding. Among the numerous types of devices encapsulated, two different types of silicon MEMS resonators were fabricated. These functioning resonators demonstrate the ability of the process to successfully encapsulate devices, taking advantage of both large and small trench widths. Such a generalized fabrication platform greatly expands the possibilities of the wafer-scale encapsulation to numerous MEMS devices and retains the robustness necessary for backend processing.
ISSN:1057-7157
1941-0158
DOI:10.1109/JMEMS.2009.2035717