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Optical Engineering

Silicon wafer thickness variation measurements using the National Institute of Standards and Technology infrared interferometer
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Paper Abstract

Decreasing depths of focus, coupled with increasing silicon wafer diameters, place greater restrictions on chucked wafer flatness in photolithography processes. A measurement device is described that measures thickness variation of double-sided polished wafers using an IR source and vidicon detector. Various possible instrument configurations are described with the focus on a setup that uses a collimated wavefront to produce interference fringes between the front and back surfaces of the plane parallel wafer. Experimental results are presented. These tests include (1) a drift test; (2) comparisons between measurements performed using different collimators and, subsequently, wavefronts; (3) an exploration of the impact of phase change on reflection due to the wafer clamping method; and (4) an intercomparison with thickness measurements recorded by a capacitance gage-based instrument and surface measurements obtained using a separate visible wavelength interferometer.

Paper Details

Date Published: 1 August 2003
PDF: 10 pages
Opt. Eng. 42(8) doi: 10.1117/1.1589757
Published in: Optical Engineering Volume 42, Issue 8
Show Author Affiliations
Tony L. Schmitz, Univ. of Florida (United States)
Angela D. Davies, Univ. of North Carolina/Charlotte (United States)
Chris Evans, Hymatic Engineering (United Kingdom)
Robert E. Parks

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