23 July 1985 Phase Gratings As Waferstepper Alignment Marks For All Process Layers
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The performance of a wafer stepper alignment system based upon phase gratings etched in the silicon has been investigated both experimentally and theoretically. Measurements of the alignment accuracy as a function of the light intensity reflected from the wafer show that the accuracy is better than 0.1 micron down to reflectivities as low as 0.15%. The various factors influencing the alignment signal by processing layers have been analyzed. A standard marker geometry is given, which produces a 0.1 micron alignment accuracy for the vast majority of processing conditions. For some special cases such as planarizing resist layers a different marker geometry is preferrable.
© (1985) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
S. Wittekoek, J. van der Werf, R. A. George, "Phase Gratings As Waferstepper Alignment Marks For All Process Layers", Proc. SPIE 0538, Optical Microlithography IV, (23 July 1985); doi: 10.1117/12.947743; https://doi.org/10.1117/12.947743


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