Inspection methods and systems for lithographic masks
US7564545B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Mar 15, 2007 |
| Grant date | Jul 21, 2009 |
| Priority date | — |
| Expiry date | Feb 14, 2028 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/705
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
Disclosed are apparatus and methods for finding lithographically significant defects on a reticle. In general, at least a pair of related intensity images of the reticle in question are obtained using an inspection apparatus. The intensity images are obtained such that each of the images experience different focus settings for the reticle so that there is a constant focus offset between the two focus values of the images. These images are then analyzed to obtain a transmission function of the reticle. This transmission function is then input into a model of the lithography system (e.g., a stepper, scanner, or other related photolithography system) to then produce an aerial image of the reticle pattern. The aerial image produced can then be input to a photoresist model to yield a “resist-modeled image” that corresponds to an image pattern to be printed onto the substrate using the reticle. This resist-modeled image can then be compared with a reference image to obtain defect information. In particular, due to the introduction of the lithography tool and photoresist model, this defect information pertains to lithographically significant defects.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.