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Journal of Micro/Nanolithography, MEMS, and MOEMS

Bulk micromachining of a MEMS tunable Fabry-Perot interferometer: effect of residual silicon on device performance
Author(s): Rohit Srivastava; Urvi Gururaj Shenoy; Scott Forrest; Swetha Chinnayelka; J. Shaikh Mohammed; Ronald S. Besser; Michael J. McShane
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Paper Abstract

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 10×10 mm with deflection regions of 2X2 mm. The device employs electrostatic actuation to tune the output wavelength, for which finite element modeling predicted low (<1 V) 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.

Paper Details

Date Published: 1 October 2004
PDF: 10 pages
J. Micro/Nanolith. MEMS MOEMS 3(4) doi: 10.1117/1.1794707
Published in: Journal of Micro/Nanolithography, MEMS, and MOEMS Volume 3, Issue 4
Show Author Affiliations
Rohit Srivastava, Louisiana Tech Univ. (United States)
Urvi Gururaj Shenoy, Louisiana Tech Univ. (United States)
Scott Forrest, Louisiana Tech Univ. (United States)
Swetha Chinnayelka, Louisiana Technical Univ. (United States)
J. Shaikh Mohammed, Louisiana Tech Univ. (United States)
Ronald S. Besser, Stevens Institute of Technology (United States)
Michael J. McShane, Louisiana Tech Univ. (United States)

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