Method for determining the thickness of a contaminating layer and/or the type of contaminating material, optical element and EUV-lithography system
US10627217B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 12, 2017 |
| Grant date | Apr 21, 2020 |
| Priority date | — |
| Expiry date | Apr 12, 2037 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2021/9511
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The invention relates to a method for determining the thickness of a contaminating layer and/or the type of a contaminating material on a surface (7) in an optical system, in particular on a surface (7) in an EUV lithography system, comprising: irradiating the surface (7) on which plasmonic nanoparticles (8a,b) are formed with measurement radiation (10), detecting the measurement radiation (10a) scattered at the plasmonic nanoparticles (8a,b), and determining the thickness of the contaminating layer and/or the type of the contaminating material on the basis of the detected measurement radiation (10a). The invention also relates to an optical element (1) for reflecting EUV radiation (4), and to an EUV lithography system.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.