| 摘要 |
A method for correcting proximity effects on a mask used in a lithographic process is described. Proximity effects are recognized to be low-pass filter in nature and full advantage of this fact is taken. Shapes having a high radius of curvature are replaced with mask patterns having smaller radii of curvature, rendering the image less susceptible to low-pass filtering effects while achieving a high fidelity printing on the mask. This approach provides better control to the mask designer to handle critical dimensions of the shapes on the mask. The method for correcting proximity effects on a mask includes the steps of providing at least one curved shape to approximate the contour of a polygon on the mask, the polygon controlling the contour of the a least one curved shape; defining the curved shape by way of a plurality of radii of curvature; assigning to each side of the polygon one of the radii of curvature; modifying the radius of curvature at each of the sides of the polygon until each of the radii of curvature reaches the maximum allowable limit for that side, the maximum allowable limit being determined from stored values of radii of curvature corresponding to a plurality of predetermined curved shapes; and combining respective curved shapes assigned to adjacent polygon sides to form a resultant closed curved shape.
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