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Nanopattern transfer to SiO2 by ion track lithography and highly selective HF vapor etching
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Ion Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Ion Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Ion Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
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2007 (English)In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 25, no 3, 862-867 p.Article in journal (Refereed) Published
Abstract [en]

The authors present a method for high aspect ratio nanopatterning of high density (1010  pores/cm2) self-assembled porous alumina membrane pattern into thermally grown SiO2 on silicon. The pattern transfer is accomplished by irradiating through 2  µm thick porous alumina membrane with swift heavy ions (4  MeV Cl2+). Ions passing through the nanopores in the mask at a fairly high fluence (typically 1014  ions/cm2) are impinging on the substrate and creating a continuous volume of overlapping ion tracks of damage. The damage is sufficient to be selectively etched by HF vapor from an aqueous HF solution. From an alumina mask with pores of 70  nm diameter, a pattern of pores of 77  nm in diameter and the same distance of 100  nm between the centers of the pores was transferred. The deepest observed etched pores were 355  nm, giving an aspect ratio of 5, which is up to 40 times larger compare to earlier work where HF wet etching was used. This ion track lithography technique shows a potential to produce nanostructures with even higher aspect ratios.

Place, publisher, year, edition, pages
2007. Vol. 25, no 3, 862-867 p.
Keyword [en]
silicon compounds, nanopatterning, nanolithography, ion beam effects, etching, masks, resists, porosity, nanoporous materials
National Category
Engineering and Technology Physical Sciences
URN: urn:nbn:se:uu:diva-94957DOI: 10.1116/1.2738481ISI: 000247551300033OAI: oai:DiVA.org:uu-94957DiVA: diva2:168991
Available from: 2006-10-13 Created: 2006-10-13 Last updated: 2016-04-11Bibliographically approved
In thesis
1. Nanopatterning by Swift Heavy Ions
Open this publication in new window or tab >>Nanopatterning by Swift Heavy Ions
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Today, the dominating way of patterning nanosystems is by irradiation-based lithography (e-beam, DUV, EUV, and ions). Compared to the other irradiations, ion tracks created by swift heavy ions in matter give the highest contrast, and its inelastic scattering facilitate minute widening and high aspect ratios (up to several thousands). Combining this with high resolution masks it may have potential as lithography technology for nanotechnology. Even if this ‘ion track lithography’ would not give a higher resolution than the others, it still can pattern otherwise irradiation insensitive materials, and enabling direct lithographic patterning of relevant material properties without further processing. In this thesis ion tracks in thin films of polyimide, amorphous SiO2 and crystalline TiO2 were made. Nanopores were used as templates for electrodeposition of nanowires.

In lithography patterns are defined by masks. To write a nanopattern onto masks e-beam lithography is used. It is time-consuming since the pattern is written serially, point by point. An alternative approach is to use self-assembled patterns. In these first demonstrations of ion track lithography for micro and nanopatterning, self-assembly masks of silica microspheres and porous alumina membranes (PAM) have been used.

For pattern transfer, different heavy ions were used with energies of several MeV at different fluences. The patterns were transferred to SiO2 and TiO2. From an ordered PAM with pores of 70 nm in diameter and 100 nm inter-pore distances, the transferred, ordered patterns had 355 nm deep pores of 77 nm diameter for SiO2 and 70 nm in diameter and 1,100 nm deep for TiO2. The TiO2 substrate was also irradiated through ordered silica microspheres, yielding different patterns depending on the configuration of the silica ball layers.

Finally, swift heavy ion irradiation with high fluence (above 1015/cm2) was assisting carbon nanopillars deposition in a PAM used as template.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 48 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 229
Materials science, swift heavy ions, lithography, nanopatterning, self-assembly, Materialvetenskap
urn:nbn:se:uu:diva-7183 (URN)91-554-6676-1 (ISBN)
Public defence
2006-11-03, Siegbahns Salen, The Ångstöm Laboratory, Lägerhyddsvägen, Uppsala, 09:30
Available from: 2006-10-13 Created: 2006-10-13Bibliographically approved

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Jensen, JensPossnert, GöranBoman, MatsHjort, Klas
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