Fraunhofer Institute for Applied Optics and Precision Engineering IOF
Fraunhofer Institute for Applied Optics and Precision Engineering IOF

EUV/XUV Coatings

Coatings and coating systems for the extreme ultraviolet spectral range

 

In recent years, optics development has increasingly focused on optical components for ever shorter wavelengths. This trend is based on the one hand on the demand to increase the resolving power of optical systems and on the other hand on the availability of powerful beam sources in the extreme ultraviolet (EUV) and soft X-ray range.


New applications of optics for short wavelengths

In addition to EUV lithography (λ = 13.5 nm), outstanding applications of EUV and X-ray optics include: applications in astronomy, beamline optics for synchrotrons, optics for X-ray lasers and, in the future, XFELs. There is also great potential for microscopy in the so-called water window (λ = 2.4 nm ... 4.4 nm). In this spectral range, many biological samples are transparent and thus particularly easily accessible for investigations. The extremely short wavelengths enable unprecedented resolutions and thus completely new examination methods in biology and medicine. Reflection values of 5.2 % at 2.48 nm and 20 % at 3.1 nm were achieved by multilayer systems based on chromium, vanadium and scandium.

 

Our services in the field of EUV/XUV coatings

We offer customers from industry and research a comprehensive range of services consisting of design of optical coating systems, development of coating processes for different applications and the characterization of EUV components. 

 

High demands for coatings for the EUV spectral range

Special coatings are essential for optical components at extremely short wavelengths. The short wavelengths place stringent demands on film materials, thickness precision, composition, purity, roughness, morphology, as well as their interaction with surrounding materials. As a result, EUV / XUV coatings have to be fabricated with highest precision to achieve high quality. Moreover, the desired properties have to be stable even under harsh environmental conditions such as high temperatures. 

 

In-house EUV developments since 1997

 

In 1997, Fraunhofer IOF started with the design, manufacturing and characterization of multilayer systems for the EUV spectral range with a special focus on EUV lithography (EUVL) at a wavelength of 13.5 nm. In the past two decades, Fraunhofer IOF established itself as a reliable partner for various industrial suppliers of EUVL equipment.

 

Two researchers together carry a collector mirror in their hands.
© Fraunhofer IOF
660 mm collector mirror manufactured at Fraunhofer IOF for extreme ultraviolet lithography (EUVL).

Tailored solutions

In addition to the improvement of reflective properties at a wavelength of 13.5 nm, numerous R&D projects were successfully performed at Fraunhofer IOF for different industrial partners:

  • Thermally stable EUV coatings (T > 500 °C) with R > 60 % @ 13.5 nm,
  • Broadband and narrowband mirrors for the 10…100 nm spectral range,
  • Highly reflective layer systems for the 2.5 nm to 100 nm spectral range,
  • Development of the coating technologies for reducing layer stresses,
  • Construction of deposition tools for laterally graded multilayer coatings,
  • Capping layers for EUVL (with enhanced optics lifetime),
  • Cleaning strategies of contaminated EUV optics,
  • Roughness and defect mapping of EUV components before and after coating,
  • Roughness evolution modelling and virtual coating of EUV coatings,
  • Instrument for EUV scattering and reflectance measurements based on laboratory GDP source

 

Researcher sit at the characterization facility in the laboratory and measures the coatings of an EUV mirror.
© Fraunhofer IOF
Characterization of an EUV collector mirror with the versatile system ALBATROSS at Fraunhofer IOF.

More information on EUV mirrors

 

EUV broadband mirrors

Periodic multilayer mirrors for the EUV spectral range reflect only in a narrow spectral and angular range (typical for 13.5 nm: FWHM = 0.5 nm, FWHM = 10°). New coating designs allow enlarging the usable region. EUV broadband mirrors can be used for diverse applications such as coating of high-NA optics for EUV lithography, maximizing of integral reflectance using broadband EUV sources and optics for attosecond pulses.

We offer:

- Design, fabrication and characterization of broadband mirrors for the EUV spectral region according to customized requirements
- Optimization of wavelength ranges
- Optimization of angular ranges
- Coating of different substrate materials (e.g. fused silica, silica, ULETM, Zerodur®)
- Coating of different substrate geometries (e.g. flat, spheres, aspheres)  

 

EUV narrowband mirrors

Standard multilayer mirrors for the EUV spectral range reflect in a narrow wavelength range and are therefore usable as monochromators (typical for 13.5 nm: FWHM = 0.5 nm, FWHM = 10°), however with a low resolution. New coating designs developed at Fraunhofer IOF allow improving the resolution considerably. EUV narrow band mirrors can be used for diverse applications such as monochromators for EUV broadband sources and separation of higher harmonics in the EUV spectral range.

We offer:

- Design, fabrication and characterization of narrowband mirrors for the EUV spectral region according to customized requirements
- Optimization of bandwidth for different wavelength and angles of incidence
- Coating of different substrate materials (e.g. fused silica, silica, ULETM, Zerodur®)
- Coating of different substrate geometries (e.g. flat, spheres, aspheres)

 

Our infrastructure and equipment

For our work we use a broad pool of design, coating, and characterization techniques (complete overview). The Nessy 3 coating system for coating production by means of magnetron sputtering is at the center of our work.

 

Future technologies on behalf of industry and science

 

While EUV coatings have now found their way into commercial production and represent a key element of the latest generation of lithography systems, we are working on further improvements and pushing the boundaries to ever shorter wavelengths, better performance and thus opening up new fields of application.

As an application-oriented research facility, we work together with project partners from science and industry to make new technologies and applications in the extreme ultraviolet spectral range of light possible. We develop optics adapted to the needs of our customers, whose coating systems provide excellent results under the extraordinary requirements of wavelengths in the EUV and soft X-ray range.  

 

Coating system Nessy in the laboratory of the Fraunhofer IOF.
© Fraunhofer IOF
Coating system Nessy at Fraunhofer IOF for EUV coatings produced by magnetron sputtering.

Our research strength

 

Articles of the annual report

The research strength of our experts is reflected, among other things, in the contributions to the Fraunhofer IOF Annual Report. In this report, selected research results from the previous year are published annually (Archive Annual Reports). Here you can find the contributions on developments around coatings for the extreme ultraviolet spectral range from the past years:

  • Article about the German Future Prize for EUV lithography "Three times German Future Prize" (Annual Report 2020, pages 6-9)
  • "The first step for a new lithography generation" (Annual Report 2016, pages 74-75)
  • "High-reflective XUV multilayer mirrors" (Annual Report 2015, pages 68-69)

 

Excellent scientific publications and patents

A large number of scientific results are published by our researchers in scientific journals and a wide variety of developments have already been successfully patented. We offer adapted licenses for our patented processes.

A list of technical papers as well as patents on EUV and XUV coatings can be found below:

Selection of scientific publications

Patent selection

 

German Future Prize

The German President awarded the German Future Prize 2020 to the team of experts led by Dr. Peter Kürz, ZEISS Semiconductor Manufacturing Technology Division, Dr. Michael Kösters, TRUMPF Lasersystems for Semiconductor Manufacturing, and Dr. Sergiy Yulin, Fraunhofer IOF.

They are involved in the development and industrial series production of EUV technology. The future technology, which is secured by over 2,000 patents and forms the basis for digitization, enables applications such as autonomous driving, 5G, artificial intelligence, and other innovations.

Read more

Further Information

From the successful project work of many years, Fraunhofer IOF has established a broad knowledge about the development and production of different reflection optics for the spectral range from 1-100 nm. This includes the fundamental understanding of layer growth processes, the use of new design approaches to minimize roughness and interdiffusion at the layer interfaces as well as the further development of various coating technologies.

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We develop customized solutions for photonic problems from industry and science.

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If you have any questions about the cooperation with Fraunhofer IOF, you can find more information under the following link: 

 

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Functional Surfaces and Coatings

Get an overview of the entire range of services offered by our scientific department "Functional Surfaces and Coatings" at Fraunhofer IOF.

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