17 October 2008 Extracting mask error function from intensity slices
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Abstract
A new method to calculate Mask Error Enhancement Function, or MEEF, from the intensity slope of the unperturbed geometry and intensity offset of the perturbed mask is derived. In the limit of small perturbations, the intensity slope technique is predicted to be the same as MEEF values calculated from the ratio of wafer to mask CD differences scaled by the magnification. Full chip process window simulations were done to compare the accuracy of this new approach for 45 to 90nm mask designs for line, space and contact features. The standard deviation was less than 0.11 and the largest deviation was only 12% for over 5200 MEEF calculations. Below MEEF values of 20, the standard deviation was less 0.065 and all simulations were within ±0.5. A significant discovery in this work is the inverse relationship between image intensity slope rather than NILS or ILS at the location of the printed feature edge and MEEF. Since the image slope decreases closer to the intensity extrema, high MEEF regions are predicted to be those that print closest to the minimum and maximum intensities.
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David Ziger, "Extracting mask error function from intensity slices", Proc. SPIE 7122, Photomask Technology 2008, 71223W (17 October 2008); doi: 10.1117/12.801821; https://doi.org/10.1117/12.801821
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