Fabrication of Mo/Si multilayer mirrors for extreme ultraviolet lithography by means of superconducting bulk magnet magnetron sputtering

U. Mizutani, T. Yamaguchi, H. Ikuta, T. Tomofuji, Y. Yanagi, Y. Itoh, T. Oka

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The fabrication of a highly reflective multi-layer film is an urgent need in the next-generation extreme ultraviolet (EUV) lithography to print ever-smaller circuit patterns onto semiconductor wafers by using extremely short wavelength (13.5 nm) light. For this purpose, we have synthesized the Mo/Si multi-layer films by employing the two-cathode superconducting bulk magnet magnetron sputtering apparatus. The films were made by repeatedly depositing a pair of 4.5 nm thick Si and then 2.5 nm thick Mo layer up to 40 or 50 pairs on the Si wafer with its root-mean square (rms) surface roughness of 0.1 nm. The resulting rms surface roughness of the Mo/Si multi-layer film turned out to be 0.12 nm. The transmission electron microscope (TEM) studies revealed the inter-diffusion layer thicknesses of Si-on-Mo and Mo-on-Si layers to be 0.5 and 1.5 nm, respectively. The EUV-reflectivity was theoretically calculated to reach the value of 70%, when these structural data are inserted into the reflectivity formula. However, the highest EUV-reflectivity so far observed was 67% in the normal incident condition. The 2-3% shortage of the reflectivity is attributed to the presence of residual Xe gas atoms incorporated into the film during deposition in the reduced Xe gas atmosphere.

Original languageEnglish
Pages (from-to)1456-1460
Number of pages5
JournalPhysica C: Superconductivity and its applications
Volume468
Issue number15-20
DOIs
Publication statusPublished - 2008 Sep 15

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Keywords

  • EUV lithography
  • Magnetron sputtering
  • Mo/Si multilayer
  • Superconducting bulk magnet

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering

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