MEMs Tunable Fabry-Perot Interferometers

Bulk micromachining of a MEMS tunable Fabry-Perot interferometer: effect of residual silicon on device performance

[+] Author Affiliations
Rohit Srivastava

Louisiana Tech University, Institute for Micromanufacturing, Biomedical Engineering Program, Ruston, Louisiana?71272

U. Gururaj Shenoy

Louisiana Tech University, Biomedical Engineering Program, Ruston, Louisiana?71272

Scott R. Forrest, S. Chinnayelka, Javeed Shaikh Mohammed

Louisiana Tech University, Institute for Micromanufacturing, Ruston, Louisiana?71272

Ronald S. Besser

Louisiana Tech University, Chemical Engineering Program, Ruston, Louisiana?71272

Michael J. McShane

Louisiana Tech University, Institute for Micromanufacturing, and Biomedical Engineering Program, Ruston, Louisiana?71272 E-mail: mcshane@latech.edu

J. Micro/Nanolith. MEMS MOEMS. 3(4), 579-588 (Oct 01, 2004). doi:10.1117/1.1794707
History: Received Oct. 31, 2003; Revised Mar. 22, 2004; Accepted Apr. 21, 2004; Online October 08, 2004
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A broadband tunable filter for the infrared spectral region is desired for use as a wavelength selective element in a miniature absorption spectrometer. We present the design, fabrication, packaging, and characterization of a bulk micromachined Fabry-Perot interferometer (FPI) for meeting this need. A novel approach to fabricate a MEMS-based tunable resonant cavity using two separate wafers bonded using a “lock-and-key” spacer design is outlined, with the goal of realizing electrostatically actuated membranes from films predeposited on base substrates. This ability could enable the pursuit of MEMS devices without in-house chemical vapor deposition (CVD) capability, after overcoming the shortcomings of bulk micromachining. The FPI device was designed with a planar structure comprising two face-to-face bonded chips of overall lateral dimension 10×10mm with deflection regions of 2×2mm. The device employs electrostatic actuation to tune the output wavelength, for which finite element modeling predicted low (<1V) actuation voltages for movement of the membrane. Experimental results from device testing (mechanical) were found to differ from the theoretical predictions, primarily due to fabrication issues. Specifically, the device performance was found to be greatly influenced by the amount of residual silicon on the wafer chip following inductively coupled plasma (ICP) backside etching, with high voltages (30 times higher than modeled) required for actuation of the device. Through a combination of modeling and experimental measurements, it is demonstrated that the ability to produce MEMS devices by releasing membranes from films predeposited on substrates is highly susceptible to error in etching and packaging.© 2004 Society of Photo-Optical Instrumentation Engineers.

© 2004 Society of Photo-Optical Instrumentation Engineers

Citation

Rohit Srivastava ; U. Gururaj Shenoy ; Scott R. Forrest ; S. Chinnayelka ; Javeed Shaikh Mohammed, et al.
"Bulk micromachining of a MEMS tunable Fabry-Perot interferometer: effect of residual silicon on device performance", J. Micro/Nanolith. MEMS MOEMS. 3(4), 579-588 (Oct 01, 2004). ; http://dx.doi.org/10.1117/1.1794707


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