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A fabrication process based on structural layer formation using Au–Au thermocompression bonding for RF MEMS capacitive switches and their performance

Published online by Cambridge University Press:  30 July 2014

Cagri Cetintepe ,
Ebru Sagiroglu Topalli ,
Simsek Demir ,
Ozlem Aydin Civi  and
Tayfun Akin
Cagri Cetintepe*
Affiliation:
Department of Electrical and Electronics Engineering, Middle East Technical University, Ankara, Turkey. Phone: +90 312 210 2301
Ebru Sagiroglu Topalli
Affiliation:
Middle East Technical University – MEMS Research and Applications Center, Ankara, Turkey. Phone: +90 312 210 6310
Simsek Demir
Affiliation:
Department of Electrical and Electronics Engineering, Middle East Technical University, Ankara, Turkey. Phone: +90 312 210 2301
Ozlem Aydin Civi
Affiliation:
Department of Electrical and Electronics Engineering, Middle East Technical University, Ankara, Turkey. Phone: +90 312 210 2301
Tayfun Akin
Affiliation:
Department of Electrical and Electronics Engineering, Middle East Technical University, Ankara, Turkey. Phone: +90 312 210 2301 Middle East Technical University – MEMS Research and Applications Center, Ankara, Turkey. Phone: +90 312 210 6310
*
Corresponding author: C. Cetintepe Email: ccagri@metu.edu.tr
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Abstract

This paper presents a radio frequency micro-electro-mechanical-systems (RF MEMS) fabrication process based on a stacked structural layer and Au–Au thermocompression bonding, and reports on the performance of a sample RF MEMS switch design implemented with this process. The structural layer consists of 0.1 µm SiO2/0.2 µm SixNy/1 µm Cr–Au layers with a tensile stress less than 50 MPa deposited on a silicon handle wafer. The stacked layer is bonded to a base wafer where the transmission lines and the isolation dielectric of the capacitive switch are patterned. The process flow does not include a sacrificial layer; a recess etched in the base wafer provides the air gap instead. The switches are released by thinning and complete etching of the silicon handle wafer by deep reactive ion etching (DRIE) and tetramethylammonium hydroxide (TMAH) solution, respectively. Millimeter-wave measurements of the fabricated RF MEMS switches demonstrate satisfactory up-state performance with the worst-case return and insertion losses of 13.7 and 0.38 dB, respectively; but the limited isolation at the down-state indicates a systematic problem with these first-generation devices. Optical profile inspections and retrospective electromechanical analyses not only confirm those measurement results; but also identify the problem as the curling of the MEMS bridges along their width, which can be alleviated in the later fabrication runs through proper mechanical design.

Keywords

RF-MEMS and MOEMSModelingSimulation and characterizations of devices and circuits
Type
Research Papers
Information
International Journal of Microwave and Wireless Technologies , Volume 6 , Issue 5: MEMSWAVE Symposium 2013 , October 2014 , pp. 473 - 480
Copyright
Copyright © Cambridge University Press and the European Microwave Association 2014 

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