Patent ID: 8612900

Claim:
A method, implemented by a computer, of optimizing an initial design rule into an updated design rule for producing a mask layout to be imaged by a lithographic apparatus, the method comprising: selecting an initial design rule for the mask layout; selecting an autocorrelation function associated with a predefined optical condition of the lithographic apparatus; selecting respective diffraction order functions for at least two polygons in the mask layout; determining, using the computer, a desired distance between the at least two polygons by cross-correlating the diffraction order functions and the autocorrelation function to obtain an estimate of illumination intensity at locations of a wafer plane associated with the at least two polygons upon an illumination of the mask layout by the lithographic apparatus; updating the initial design rule to generate the updated design rule based on the determined value of the desired distance between the at least two polygons; and wherein determining the desired distance between the at least two adjacent polygons includes: calculating an image log slope (ILS) of an intensity profile at an edge of a calculated image of a first polygon including a contribution of a calculated image of at least one other polygon located at an initial distance ‘a 0 ’ defined in the initial design rule; tracking variation of the ILS with variation of ‘a 0 ’; and selecting a value of ‘a 0 ’ where the variation of the ILS is minimal to be the desired distance between the first polygon and the at least one other polygon.