Interface roughness in Mo/Si multilayers

I. Nedelcu* (Corresponding Author), R.W.E. van de Kruijs, A.E. Yakshin, F. Tichelaar, E. Zoethout, E. Louis, H. Enkisch, S. Muellender, F. Bijkerk

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

26 Citations (Scopus)


In this work we present a study of surface roughness development at the molybdenum-on-silicon and silicon-on-molybdenum interfaces in Mo/Si multilayers as employed in Extreme UV lithography. Thin Mo/Si multilayers, with layer thicknesses of 3-5 nm, were deposited using electron beam evaporation. The effect of ion treatment on the surface roughness was studied by X-ray reflectometry and transmission electron microscopy. Without ion treatment we observed build up of correlated roughness. The roughness development is shown here to depend strongly on the thickness of the crystalline Mo layer. Independent of the Mo ratio in a period, we show that a minimal amount of ion treatment is required to smoothen the multilayer roughness, which is also confirmed by EUV reflectivity measurements. At high ion energies the layers become smoother due to a larger ion penetration depth. The higher penetration depth is also shown to initiate additional interdiffusion and structural changes at buried interfaces.

Original languageEnglish
Pages (from-to)434-438
Number of pages5
JournalThin solid films
Issue number2 SPEC. ISS.
Publication statusPublished - 25 Oct 2006
Externally publishedYes


  • Interface roughness
  • Multilayers
  • Thin film deposition
  • X-ray scattering


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