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Special Section on Reliability, Packaging, Testing, and Characterization of MEMS and MOEMS III

Analytical design of polymer-encapsulated radio frequency microelectromechanical devices

[+] Author Affiliations
Pejman Monajemi

1005 Hamilton Avenue, Menlo Park, California 94025

J. Micro/Nanolith. MEMS MOEMS. 11(2), 021207 (May 10, 2012). doi:10.1117/1.JMM.11.2.021207
History: Received November 1, 2011; Revised January 5, 2012; Accepted January 19, 2012
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Abstract.  An analytical design of radio frequency microelectromechanical (RF MEMS) devices and fabrication and encapsulation results is discussed. The encapsulated MEMS device is an in-plane variable capacitor (varactor), continuously tuned up to 115% at 3.25 V, showing a Q factor of 49 at 1 GHz at zero bias and self-resonance frequency above 5 GHz. The 60-μm-thick device measures 0.6mm×0.6mm and is fabricated using high-aspect ratio single-crystal and polysilicon technology, having an air gap of 0.8 μm for tuning and 2 μm for actuation. The effect of gap size, substrate doping, and gold coating on Q is studied. The wafer-level encapsulation is done by the thermal decomposition of a sacrificial polymer through a polymer overcoat at 130°C–150°C, followed by gold evaporation to provide a degree of hermeticity. The overcoat polymer is patterned instead of screen printed, which defines the package boundary, providing a small amount of interconnection. The encapsulated device measures 0.7mm×0.7mm, which is only 35% larger than the MEMS device. The insertion loss of the 1μm/20μm gold/Avatrel package is measured to be 1.4 dB at 1 GHz and 1.51 dB at 5 GHz, and the calculated nitrogen permeability is less than 1 Barrer. The temperature stability of the rest and the maximum capacitance is better than 7%, in the range of 3050°C.

© 2012 Society of Photo-Optical Instrumentation Engineers

Citation

Pejman Monajemi
"Analytical design of polymer-encapsulated radio frequency microelectromechanical devices", J. Micro/Nanolith. MEMS MOEMS. 11(2), 021207 (May 10, 2012). ; http://dx.doi.org/10.1117/1.JMM.11.2.021207


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