1 August 2003 Silicon wafer thickness variation measurements using the National Institute of Standards and Technology infrared interferometer
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Optical Engineering, 42(8), (2003). doi:10.1117/1.1589757
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.
Tony L. Schmitz, Angela D. Davies, Chris Evans, Robert E. Parks, "Silicon wafer thickness variation measurements using the National Institute of Standards and Technology infrared interferometer," Optical Engineering 42(8), (1 August 2003). http://dx.doi.org/10.1117/1.1589757
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KEYWORDS
Semiconducting wafers

Silicon

Interferometers

Collimators

Reflection

Wavefronts

Collimation

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