Method for producing a reflective optical element for EUV-lithography
US9733580B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 20, 2013 |
| Grant date | Aug 15, 2017 |
| Priority date | — |
| Expiry date | Dec 30, 2033 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG21K1/062
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A method aleviating blistering, cracking and chipping in topmost layers of a multilayer system exposed to reactive hydrogen, when producing a reflective optical element (50) having a maximum reflectivity at an operating wavelength of 5 nm to 20 nm. A multilayer system (51) composed of 30-60 stacks (53) is applied to a substrate (52). Each stack has a layer (54) of thickness dMLs composed of a high refractive index material and a layer (55) of thickness dMLa composed of a low refractive index material. The thickness ratio is dMLa/(dMLa+dMLs)=ΓML. Two to five further stacks (56) are applied to the multilayer system. at least one further stack having a layer (54) of thickness ds composed of a high refractive index material and a layer (55) of thickness da composed of a low refractive index material, wherein the thickness ratio is da/(da+ds)=Γ and wherein Γ≠ΓML.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.