Imaging overlay with mutually coherent oblique illumination
US12032300B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 12, 2022 |
| Grant date | Jul 9, 2024 |
| Priority date | — |
| Expiry date | Jul 12, 2042 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/706851
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An overlay metrology system may include illumination sources configured to generate one or more pairs of mutually coherent illumination beams and illumination optics to direct the pairs of illumination beams to an overlay target at common altitude incidence angles and symmetrically opposed azimuthal incidence angles, where the overlay target includes two or more grating structures distributed along one or more measurement directions. The system may further include imaging optics to image the overlay target onto detectors when implementing the metrology recipe, where an image of a particular one of the two or more grating structures is generated exclusively with a single non-zero diffraction order of light from each of the illumination beams within the particular one of the pairs of illumination beams. The system may further include a controller to determine overlay measurements based on images of the overlay target.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.