12 April 2013 Optomechanical characterization of large wafer stepper-optics with respect to centering errors, lens distances, and center thicknesses
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Abstract
One key technology in mass microchip-production is an optical projection system (wafer stepper) for deep UV photolithography. Modern wafer stepper-optics featuring sub-200nm resolution, consist of 20 to 25 glass elements with a weight of up to 1000 kg including mechanical parts. After the careful glass element-manufacturing, the optical performance of the system is highly influenced by the precise mechanical alignment of all individual lens elements. The imaging quality of such systems is extremely sensitive to alignment errors as they may severely degrade the imaging quality. Therefore, the optical design of a stepper optic has tight tolerances for the alignment in the sub-μm and arc second range. We will present a high resolution optical measurement system that performs non-contact measurements of centering errors of each surface in an assembled optics with a measurement accuracy of 0.1 μm, and it determines the air gap-distances and lens center-thicknesses with a measurement accuracy of 1.0 μm.
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Daniel Stickler, Patrik Langehanenberg, Bernd Lüerß, Josef Heinisch, "Optomechanical characterization of large wafer stepper-optics with respect to centering errors, lens distances, and center thicknesses", Proc. SPIE 8683, Optical Microlithography XXVI, 86832C (12 April 2013); doi: 10.1117/12.2011492; https://doi.org/10.1117/12.2011492
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