Patent ID: 7117478

Claim:
A method of inspecting a first marginal area of a design on or in a photomask, the method comprising: evaluating a response of a lithographic design on wafer to a change in at least one process parameter of a photolithographic process to determine the first marginal area, including: generating a pixel-based bitmap representation of the lithographic design, wherein the pixel-based bitmap includes pixel data, and wherein the lithographic design includes at least a portion that is associated with the first marginal area of the design on or in the photomask; generating a first simulated image of the lithographic design on wafer using (1) the pixel-based bitmap representation of the lithographic design and (2) a first relationship representing an imaging path of projection and illumination optics of the photolithographic process, wherein the photolithographic process uses photolithographic equipment; generating a second simulated image of the lithographic design on wafer using (1) the pixel-based bitmap representation of the lithographic design and (2) a second relationship representing an imaging path of projection and illumination optics of the photolithographic process; wherein a difference between (I) the first relationship representing the imaging path of the projection and illumination optics of the photolithographic process and (ii) the second relationship representing the imaging path of the projection and illumination optics of the photolithographic process includes the change in the at least one process parameter of the photolithographic process; and determining the first marginal area of the lithographic design using the first simulated image and the second simulated image; inspecting the first marginal area of the design on or in the photomask using at least one metrology or inspection tool.