Patent ID: 7336341

Claim:
A simulator of a lithography tool comprising: a correcting parameter memory configured to store a correcting scaling value and a correcting bias, the correcting scaling value being used to correct a focus error of a projection optical system in the lithography tool, the correcting bias being used to correct a critical dimension error generated in the lithography tool; a model simulation engine configured to simulate an image formation by the lithography tool, by using a corrected focus, to model a calculated critical dimension of a simulated image, the corrected focus being calculated by multiplying an actual defocus of the projection optical system in the lithography tool by the correcting scaling value, the actual defocus being used to form an actual image by the lithography tool, the actual image corresponding to the simulated image; and a bias corrector configured to add the correcting bias to the calculated critical dimension to make the simulated image approximate to the actual image.