Abstract
SU8 submicron structures with an aspect ratio of more than 50 are made by soft X-ray lithography using modified spectra of the synchrotron radiation at the ANKA LITHO-1 beamline, which includes a chromium mirror. The X-ray spectrum is additional shaped by a beam stop and a filter to a narrow band in order to reduce the influence of diffraction and photoelectrons. The exposure determination is based on the measured threshold doses for used SU-8 resist layers as well as on the calculated diffractive distribution of an absorbed power. Post-exposure bake of the resist is performed at low temperature and low pressure to avoid changes of the structural size because of shrinkage due to temperature changes and to eliminate a “skin” layer at the top of the resist. SU8 structures with lateral dimensions of 1 μm and heights from 50 to 80 μm have been fabricated defect free with the optimized process.
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References
ANKA Instrumentation Book (2006) In: Baumbach T, Goettlicher J, Hagelstein M (eds) ANKA Angstroemquelle Karlsruhe, Institute for Synchrotron Radiation, Forschungszentrum Karlsruhe GmbH. http://ankaweb.fzk.de/_file/extras/extras_download_3.pdf
Ehrfeld W, Muenchmeyer D (1991) Three-dimensional microfabrication using synchrotron radiation. Nucl Instrum Methods Phys Res A 303:523–531
Feiertag G, Ehrfeld W, Lehr H, Schmidt A, Schmidt M (1997) Calculation and experimental determination of the structure transfer accuracy in deep X-ray lithography. J Micromech Microeng 7:23–331
Feldman M, Sun J (1992) Resolution limits in X-ray lithography. J Vac Sci Technol B10:3173–3176
Grün AE (1957) Lumineszenz-photometrische Messungen der Energieabsorption im Strahlungsfeld von Elektronenquellen. Eindimensionaler Fall in Luft. Z Naturforsch 12A:89–95
Handbook of physics (1967) In: Condon EU, Odishaw H (eds) 2nd edn. McGraw-Hill, New York
Mappes T, Achenbach S, Mohr J (2007) Process conditions in X-ray lithography for the fabrication of devices with sub-micron features sizes. Microsyst Technol 13:355–360
Megtert S, Pantenburg FJ, Achenbach S, Kupka R, Mohr J, Roulliay M (1999) Preliminary results on the use of mirrors for LIGA process. Proc SPIE 3680:917–923
Menz W, Mohr J (1997) Microsystemtechnik fuer Ingenieure. VCH A Wiley Cmpany, Weinheim
Müller C, Mohr J (1993) Microspectrometer fabricated by the LIGA-Process. Interdiscip Sci Rev 18:273–279
Nazmov V, Reznikova E, Mohr J, Snigirev A, Snigireva I, Achenbach S, Saile V (2004a) Fabrication and preliminary testing of X-ray lenses in thick SU-8 resist layers. Microsyst Technol 10:716–721
Nazmov V, Reznikova E, Somogyi A, Mohr J, Saile V (2004b) Planar sets of cross X-ray refractive lenses from SU-8 polymer. Proc SPIE 5539:235–243
Nazmov V, Reznikova E, Mohr J (2005) Investigation of radiation-induced thermal flexure of X-ray lithography mask during tilted exposure. In: Book of abstracts of high aspect ratio micro structure technology workshop, Gyeongju, Korea, pp 130–131
Pantenburg F, Mohr J (1995) Influence of secondary effects on structure quality in deep X-ray lithography. Nucl Instrum Methods Phys Res B 97:551–556
Perennes F, Pantenburg FJ (2001) Adhesion improvement in deep X-ray lithography process using a central beam-stop. Nucl Instrum Methods Phys Res B 174:317–323
Reznikova E, Nazmov V, Mohr J (2002) Deep X-ray lithography characteristics of SU-8 photo-resist. In: Digest reports of the XIV Russian Synchrotron radiation conference (SR-2002), July 15–19, Novosibirsk, Russia, p 137
Reznikova E, Mohr J, Hein H (2005a) Deep photo-lithography characterization of SU-8 resist layers. Microsyst Technol 11:282–291
Reznikova E, Nazmov V, Mohr J (2005b) Characterization of pre- and post-exposure baking for ultra-deep X-ray lithography with SU-8 resist. In: Book of abstracts of high aspect ratio micro structure technology workshop (HARMST-2005), Gyeongju, Korea, pp 78–79
Acknowledgments
The authors would like to thank Siemens AG (Dr. E. Hempel) for partly funding the research work, Dr. Ch. David (Paul Scherrer Institute, Switzerland) for discussion of the results, Dr. T. Mappes (Institute of Microstructure Technology/FZK, Germany) for a discussion about optimal doses for E-beam lithography exposure of PMMA and to Dr. F.-J. Pantenburg (Institute of Microstructure Technology/FZK, Germany) for his introduction about operating peculiarities at the LITHO-1 station.
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Reznikova, E., Mohr, J., Boerner, M. et al. Soft X-ray lithography of high aspect ratio SU8 submicron structures. Microsyst Technol 14, 1683–1688 (2008). https://doi.org/10.1007/s00542-007-0507-x
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DOI: https://doi.org/10.1007/s00542-007-0507-x