Method and system for evaluating an object that has a repetitive pattern
US8228497B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 11, 2008 |
| Grant date | Jul 24, 2012 |
| Priority date | — |
| Expiry date | Aug 14, 2030 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/95623
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and system for evaluating an object that has a repetitive pattern. Illumination optics of an optical unit are adapted to scan a spot of radiation over a repetitive pattern that includes multiple regularly repeating structural elements that are optically distinguishable from their background, generating a diffraction pattern that includes multiple diffraction lobes. Collection optics are adapted to focus radiation from the repetitive pattern onto a detector. The focused radiation includes a single diffraction lobe while not including other diffraction lobes. A grey field detector generates detection signals, responsive to the focused collected radiation. The optical unit is adapted to maintain, at a detection surface of the grew field detector, a radiation pattern that includes a first radiation pattern component resulting from the repetitive pattern and a second radiation pattern component resulting from a defect; wherein the first radiation pattern component is stronger than the second radiation component.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.