Substrate recovery layers for EUVL optics: Effects on multilayer reflectivity and surface roughness

Research output: Contribution to journalConference articleAcademicpeer-review

Abstract

We have investigated the use of separation, or substrate recovery layers (SRL) enabling the re-usage of optics substrates after deposition of multilayer reflective coatings, in particular Mo/Si multilayers as used for Extreme UV lithography. An organic material, a polyimide, was applied, from other work known to reduce the roughness of the substrate1'2. It appeared to be possible to remove the multilayer coating, including the SRL, without any damage or roughening of the substrate surface. The SRL was spin-coated at 1500 - 6000 rpm on different substrate types (Si, quartz, Zerodur) with diameters up to 100 mm. For this range of parameters, the multilayer centroid wavelength value remained unchanged, while its reflectivity loss, upon applying the SRL, was limited to typically 0.7%. The latter is demonstrated to be caused by a minor increase of the SRL surface roughness in the high spatial frequency domain. The AFM characterized roughness remained constant at 0.2 nm during all stages of the substrate recovery process, independent of the initial substrate roughness.

Original languageEnglish
Article number651730
JournalProceedings of SPIE - the international society for optical engineering
Volume6517
Issue numberPART 2
DOIs
Publication statusPublished - 16 Oct 2007
Externally publishedYes
EventEmerging Lithographic Technologies XI 2007 - San Jose, United States
Duration: 27 Feb 20071 Mar 2007

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Extreme ultraviolet lithography
Extreme Ultraviolet Lithography
Reflectivity
Surface Roughness
Multilayer
Optics
Multilayers
surface roughness
roughness
Recovery
Surface roughness
recovery
Substrate
optics
reflectance
Substrates
Roughness
Coating
Reflective coatings
coatings

Cite this

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title = "Substrate recovery layers for EUVL optics: Effects on multilayer reflectivity and surface roughness",
abstract = "We have investigated the use of separation, or substrate recovery layers (SRL) enabling the re-usage of optics substrates after deposition of multilayer reflective coatings, in particular Mo/Si multilayers as used for Extreme UV lithography. An organic material, a polyimide, was applied, from other work known to reduce the roughness of the substrate1'2. It appeared to be possible to remove the multilayer coating, including the SRL, without any damage or roughening of the substrate surface. The SRL was spin-coated at 1500 - 6000 rpm on different substrate types (Si, quartz, Zerodur) with diameters up to 100 mm. For this range of parameters, the multilayer centroid wavelength value remained unchanged, while its reflectivity loss, upon applying the SRL, was limited to typically 0.7{\%}. The latter is demonstrated to be caused by a minor increase of the SRL surface roughness in the high spatial frequency domain. The AFM characterized roughness remained constant at 0.2 nm during all stages of the substrate recovery process, independent of the initial substrate roughness.",
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Substrate recovery layers for EUVL optics : Effects on multilayer reflectivity and surface roughness. / Nedelcu, I.; Van De Kruijs, R. W E; Yakshin, A. E.; Louis, E.; Bijkerk, F.; Muellender, S.

In: Proceedings of SPIE - the international society for optical engineering, Vol. 6517, No. PART 2, 651730, 16.10.2007.

Research output: Contribution to journalConference articleAcademicpeer-review

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AU - Louis, E.

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AU - Muellender, S.

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