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Proceedings Paper

Process conditions for the fabrication of subwavelength-scale structures by x-ray lithography in PMMA films
Author(s): Sven C. Achenbach; Timo Mappes; Rainer Fettig; Jeanine Kando; Juergen Mohr
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Paper Abstract

Periodically structured dielectric media with lattices on a sub-wavelength scale are receiving increased attention as they enable a variety of photonics applications. Fabrication, however, still imposes challenges to the scientific community. This article discusses process modifications in deep X-ray lithography to reduce minimum feature size and eventually allow the fabrication of high aspect ratio photonic crystal slabs with a moderate refractive index. Proximity printing requires an X-ray mask with high contrast and lateral resolution. Electron beam writing exposure doses were optimized to pattern feature sizes down to 400 nm in 3 μm thick resist. The voids were subsequently electroformed with 2 μm gold to generate the absorbers on a suspended silicon nitride membrane. The mask was copied into PMMA films of 5 μm thickness using X-ray lithography at about 0.4 nm. The yield of free standing smallest features is limited by adhesion of the resist to the substrate. Structures with aspect ratios as high as 8 to 12 tend to collapse after dip development. Periodic features are increased on the order of tens of nanometers compared to mask absorbers. Lattice constants need to be slightly reduced at fixed pore diameters before first photonic demonstrators made of PMMA can be fabricated.

Paper Details

Date Published: 15 September 2004
PDF: 9 pages
Proc. SPIE 5450, Photonic Crystal Materials and Nanostructures, (15 September 2004); doi: 10.1117/12.546030
Show Author Affiliations
Sven C. Achenbach, Forschungszentrum Karlsruhe (Germany)
Timo Mappes, Forschungszentrum Karlsruhe (Germany)
Rainer Fettig, Forschungszentrum Karlsruhe (Germany)
Jeanine Kando, Forschungszentrum Karlsruhe (Germany)
Juergen Mohr, Forschungszentrum Karlsruhe (Germany)

Published in SPIE Proceedings Vol. 5450:
Photonic Crystal Materials and Nanostructures
Richard M. De La Rue; Pierre Viktorovitch; Clivia M. Sotomayor Torres; Michele Midrio, Editor(s)

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