Mark, overlay target, and methods of alignment and overlay
US11086232B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Aug 23, 2018 |
| Grant date | Aug 10, 2021 |
| Priority date | — |
| Expiry date | Aug 23, 2038 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F9/7076
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A resonant amplitude grating mark has a periodic structure configured to scatter radiation incident on a surface plane of the alignment mark. The scattering is mainly by excitation of a resonant mode in the periodic structure parallel to the surface plane. The effective refractive indexes and lengths of portions of the periodic structure are configured to provide an optical path length of the unit cell in the direction of periodicity that equals an integer multiple of a wavelength present in the spectrum of the radiation. The effective refractive indexes and lengths of the portions are also configured to provide an optical path length of the second portion in the direction of periodicity that is equal to half of the wavelength present in the spectrum of the radiation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.