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Cold-developed electron-beam-patterned ZEP 7000 for fabrication of 13 nm nickel zone plates
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
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2009 (English)In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 27, no 6, 2593-2596 p.Article in journal (Refereed) Published
Abstract [en]

Cold development was applied to improve the resolution in a trilayer resist that is used for the fabrication of state-of-the-art soft x-ray microscopy zone plates. By decreasing the temperature of the hexyl acetate developer to -50 degrees C, 11 nm half-pitch gratings have been resolved in the electron-beam resist ZEP 7000. 12 nm half-pitch gratings have been successfully transferred, via the intermediate SiO2 hardmask, into the bottom polyimide layer by CHF3 and O-2 reactive ion etching. The trilayer resist, including optimized cold development, has finally been used in an electroplating-based process for the fabrication of nickel zone plates. Zone plates with down to 13 nm outermost zone width have been fabricated and 2.4% average groove diffraction efficiency has been measured for zone plates with 15 nm outermost zone width and a nickel height of 55 nm.

Place, publisher, year, edition, pages
2009. Vol. 27, no 6, 2593-2596 p.
Keyword [en]
electron beam lithography, nickel, optical fabrication, resists, zone, plates, x-ray microscopy, resolution, poly(methylmethacrylate), temperature, dynamics
Identifiers
URN: urn:nbn:se:kth:diva-19051DOI: 10.1116/1.3237140ISI: 000272803400055Scopus ID: 2-s2.0-72849123318OAI: oai:DiVA.org:kth-19051DiVA: diva2:337098
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
In thesis
1. High-Resolution Nanostructuring for Soft X-Ray Zone-Plate Optics
Open this publication in new window or tab >>High-Resolution Nanostructuring for Soft X-Ray Zone-Plate Optics
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Diffractive zone-plate lenses are widely used as optics in high-resolution x-ray microscopes. The achievable resolution in such microscopes is presently not limited by the x-ray wavelength but by limitations in zone-plate nanofabrication. Thus, for the advance of high-resolution x-ray microscopy, progress in zone-plate nanofabrication methods are needed.

 

This Thesis describes the development of new nanofabrication processes for improved x-ray zone-plate optics. Cold development of the electron-beam resist ZEP7000 is applied to improve the resolution of soft x-ray Ni zone plates. The influence of developer temperature on resist contrast, resolution, and pattern quality is investigated. With an optimized process, Ni zone plates with outermost zone widths down to 13 nm are demonstrated. To enhance the diffraction efficiency of Ni zone plates, the concept of Ni-Ge zone plates is introduced. The applicability of Ni-Ge zone plates is first demonstrated in a proof-of-principle experiment, and then extended to cold-developed Ni zone plates with outermost zone widths down to 13 nm. For 15-nm Ni-Ge zone plates a diffraction efficiency of 4.3% at a wavelength of 2.88 nm is achieved, which is about twice the efficiency of state-of-the-art 15-nm Ni zone plates. To further increase both resolution and diffraction efficiency of soft x-ray zone plates, a novel fabrication process for W zone plates is developed. High resolution is provided by salty development of the inorganic electron-beam resist HSQ, and cryogenic RIE in a SF6 plasma is investigated for high-aspect-ratio W structuring. We demonstrate W zone plates with 12-nm outermost zone width and a W height of 90 nm, resulting in a 30% increase in theoretical diffraction efficiency compared to 13-nm efficiency-enhanced Ni-Ge zone plates. In addition to soft x-ray zone plates, some lenses for hard x-ray free-electron-laser applications were also fabricated during this Thesis work. Fabrication processes for the materials W, diamond, and Pt were developed. We demonstrate Pt and W-diamond zone plates with 100-nm outermost zone width and respective diffraction efficiencies of 8.2% and 14.5% at a photon energy of 8 keV.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. xii, 70 p.
Series
Trita-FYS, ISSN 0280-316X ; 2011:55
Keyword
zone plates; x-ray optics; x-ray microscopy; high resolution; nanofabrication; electron beam lithography; reactive ion etching; tungsten; nickel; germanium
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-47409 (URN)978-91-7501-175-2 (ISBN)
Public defence
2011-12-02, FA31, Roslagstullsbacken 21, KTH/Albanova, Stockholm, 10:00 (English)
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Note
QC 20111114Available from: 2011-11-14 Created: 2011-11-08 Last updated: 2011-11-14Bibliographically approved

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Hertz, Hans M.Holmberg, Anders

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