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Refurbishing Used Optics

Introduction to synchrotron refurbishment & coating capabilities

Synchrotron beamline end stations and analytical instruments most often operate with high intensity X-rays. Such high intensity beams can result in damaging single film and multilayer coatings. Because synchrotron and similar custom made optics typically require extremely precise coatings on premium quality substrates, these substrates and coatings can be very expensive and require long lead times.

Rigaku Innovative Technologies (RIT) has developed a proprietary refurbishment methodology that restores synchrotron and custom multilayer systems to their original quality and performance. Their advanced techniques for high-performance multilayer optics, used in synchrotron and extreme-ultraviolet lithography (EUVL) applications, help reduce costs and lead times for setting up experimental equipment, beamline end stations, and repairing damaged multilayers.

Optical refurbishment: An effective alternative to purchasing new multilayer optics

Do your optics qualify for refurbishment or recovery?

Optical refurbishment is an effective and efficient solution to address these major challenges:

  • Recovery of optical performance by removing the damaged multilayer
  • Removal of contaminants often without damaging the underlying multilayer structure
  • Preserve the original high quality substrate surface without the need for re-polishing
  • Retain sufficient surface quality so the optic can be reused for subsequent re-deposition of a similar highly reflecting vacuum-deposited thin film
  • Maintain low micro roughness on any scale, from Low Spatial Frequency Roughness to High Spatial Frequency Roughness

Inspection Methods

RIT utilizes a multistep inspection process for assessing the quality of an optic surface. A few of our techniques and metrology tools include:

  • A visual inspection to determine large-scale surface damage or contaminates such as haze, discoloration, micro-pitting or other damage modes
  • An optical inspection of large areas for scattered defects and flaws, including both brightfield and darkfield objectives capable of locating particles as small as 0.5 µm diameter
  • A Glancing X-ray Reflectometer (GXR) measurement of X-ray reflectivity to examine the condition of any coating and the substrate.

RIT has successfully repeated various refurbishment projects toward the recovery of high-quality custom optics that include the full removal of multilayer or single-film coating and substrate preservation for custom and commercial optics for synchrotron and EUVL customers for which optical degradation remains an important factor.

Contact RIT to learn more about how you can save money and time by choosing refurbishment

Refurbishment of multilayer EUV optics based on Mo/Si coating

Wet etching: Mo/Si ML on Si substrate

EUV mirrors consisting of multilayer structures deposited on silicon substrates were etched clean then another Mo/Si multilayer structure was deposited. Then the refurbishment process was repeated 5 times. The observed roughness increase was from ~0.19nm to 0.26nm and the EUV reflectivity loss was measured to be 1.2%.

EUV - refurbishment (graphic17)EUV Reflectivity after 5 refurbishment cycles

Reactive Ion Etching

Cu-Ka reflectivity curves from EUV mirror before and after RIE. Absence of reflectivity peaks and the critical angle position demonstrate a successful removal of a multilayer structure from a silicon substrate. EUV reflectivity of a re-coated multilayer structure is currently under testing.

EUV - refurbishment (graphic18)Angular reflectivity of Cu-Ka (λ=0.154nm) radiation from EUV mirror before and after RIE.

Synchrotron case study

RIT has successfully refurbished optics that were damaged or were no longer useful since the purpose of the beamline changed. These jobs include:

  • A highly damaged optic after approximately 10 years of use is functional again
  • A substrate in which the original surface was contaminated was stripped, cleaned and recoated
  • Multilayer de-adhesion (peeling) after use was corrected by stripping and recoating the optic with a new multilayer
  • Removal of a perfect single film in order to re-task the expensive optic for a different energy range by applying a different coating material
  • Removal of functional multilayer coating and recoating with a different multilayer material

Synchrotron refurbishd (graphic01)

Multilayer or optical refurbishment can become a fundamental part of extending the end of life and financial investment contributed to synchrotron and custom multilayer optics.

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