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Silicon Wafer Thickness Variation Measurements Using the NIST Infrared Interferometer



Angela Davies, Tony L. Schmitz, R E. Parks, Christopher J. Evans


?creasing depths of focus, coupled with increasing silicon wafer diameters, place greater restrictions on chucked wafer flatness in photolithography processes. In this work, a measurement device is described that measures thickness variation of double side polished wafers using an infrared source and vidicon detector. Various possible instrument configurations are described with the focus on a setup which uses a collimated wavefront to produce interference fringes between the front and back surfaces of the plane parallel wafer. Experimental results are presented, including a drift test; comparisons between measurements performed using different collimators and, subsequently, wavefronts; an exploration of the impact of phase change on reflection due to the clamping method; and an intercomparison with thickness measurements recorded by a capacitance gage-based instrument and surface measurements obtained using a separate visible wavelength interferometer.
Optical Engineering
42 (8)


interferometry, photolithography, silicon wafer, thickness variation


Davies, A. , Schmitz, T. , Parks, R. and Evans, C. (2003), Silicon Wafer Thickness Variation Measurements Using the NIST Infrared Interferometer, Optical Engineering (Accessed June 22, 2024)


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Created August 1, 2003, Updated February 19, 2017