Patent ID: 7873204

Claim:
A method for inspecting a photomask to identify lithographically significant defects, the method comprising: providing a photomask for inspection, the photomask configured to achieve photolithographic transfer of a mask pattern onto a substrate using a lithography system; producing a transmission intensity image and a reflection intensity image of the photomask using an inspection apparatus having a larger numerical aperture at the reticle plane than that of the lithography system; processing the transmission intensity image and the reflection intensity image together to recover a band limited mask pattern; providing a model of the lithography system to be employed in lithographic transfer of the mask pattern onto a substrate; adapting the model of the lithography system so that the band limited mask pattern can be input into the model of the lithography system to obtain an aerial image of the mask pattern; processing the aerial image together with a photoresist model consistent with the photoresist used in the lithographic transfer of the mask pattern onto a substrate with said lithography system, said processing yielding a resist-modeled image that corresponds to a printed image pattern printed onto the substrate using said photomask; and determining if the photomask has lithographically significant defects.