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Proceedings Paper

Low-coherence interferometric absolute distance gauge for study of MEMS structures
Author(s): Wojciech J. Walecki; Kevin Lai; Alexander Pravdivtsev; Vitali Souchkov; Phuc Van; Talal Azfar; Tim Wong; S. H. Lau; Ann Koo
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Paper Abstract

The most commonly employed tools for wafer thickness and topography metrology are based on capacitance method, which due to physical size of probes, and may not be suitable for direct measurement of multi-layer non-conductive wafers or Micro Electromechanical Systems (MEMS) structures. Recently developed that low coherence interferometry provides solution, which overcomes limitations of these methods. Selected MEMS applications including characterization of deep (high aspect) trenches and membrane structures have been also developed. The above listed applications were limited to measurements of relative distance between two optical interfaces in material transparent at the wavelength of probing radiation. Absolute distance gauging by fiber optic low coherence interferometer is difficult due to large thermal drift (of the order of 0.04 mm/K). We demonstrate that this drift is a result of thermal changes of refractive index of fiber optic glass. We present solution eliminating this drift is based on introduction of the additional reference plane in the signal arm of the Michelson interferometer. Use of this reference plane eliminates influence of changes of refractive index of glass fibers on result of measurement and improves thermal stability of low coherence interferometer by three orders of magnitude.

Paper Details

Date Published: 22 January 2005
PDF: 7 pages
Proc. SPIE 5716, Reliability, Packaging, Testing, and Characterization of MEMS/MOEMS IV, (22 January 2005); doi: 10.1117/12.590013
Show Author Affiliations
Wojciech J. Walecki, Frontier Semiconductor, Inc. (United States)
Kevin Lai, Frontier Semiconductor, Inc. (United States)
Alexander Pravdivtsev, Frontier Semiconductor, Inc. (United States)
Vitali Souchkov, Frontier Semiconductor, Inc. (United States)
Phuc Van, Frontier Semiconductor, Inc. (United States)
Talal Azfar, Frontier Semiconductor, Inc. (United States)
Tim Wong, Frontier Semiconductor, Inc. (United States)
S. H. Lau, Frontier Semiconductor, Inc. (United States)
Ann Koo, Frontier Semiconductor, Inc. (United States)


Published in SPIE Proceedings Vol. 5716:
Reliability, Packaging, Testing, and Characterization of MEMS/MOEMS IV
Danelle M. Tanner; Rajeshuni Ramesham, Editor(s)

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