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

I. Nedelcu*, R.W.E. van de Kruijs, A.E. Yakshin, E. Louis, F. Bijkerk, S. Muellender

*Corresponding author for this work

Research output: Contribution to journalConference articleAcademicpeer-review


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
Issue numberPART 2
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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