The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
Aalto

Fabrication Process Development for Silicon Micro and Nanosystems

Nikolai Chekurov

Doctoral dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the School of Electrical Engineering for public examination and debate in Auditorium AS1 at the Aalto University (Espoo, Finland) on the 25th of November 2011 at 12 noon.

Overview in PDF format (ISBN 978-952-60-3593-2)   [1304 KB]
Dissertation is also available in print (ISBN 978-952-60-3592-5)

Abstract

Micromechanical devices have been fabricated out of silicon for decades, but only recently even smaller structures - nanodevices have become experimentally possible. Traditionally silicon devices are fabricated using separate lithography and various etching methods.

This thesis work concentrates on developing fabrication techniques for silicon micro and nanostructures. The goal was to achieve nanometer-scale feature size and simultaneously significantly speed up the most time consuming phases. For testing purposes also functional devices were designed and fabricated.

Main discoveries are related to the use of ion beam writing in a nonstandard manner. Instead of direct milling, methods were developed to directly use the beam to replace time consuming lithography step by the substrate treatment by ions. As a result, several silicon-based fabrication techniques were developed that require only a few processing steps and therefore can be realized in less than one day. The main achievement is in overcoming some of the limitations of serial writing methods such as those required in electron beam lithography or focused ion beam processing. High aspect ratio (laterally small, but tall) structures were successfully obtained using both technologies for the pattern transfer.

Fabrication techniques, described in this thesis, open up an opportunity for the developers to almost instantly test their ideas using functional components by altering the way nanosystems are developed. The presented methods cannot easily be extended to mass production but are appropriate in basic research and prototyping.

This thesis consists of an overview and of the following 7 publications:

  1. O. Hahtela, N. Chekurov, and I. Tittonen. 2005. Non-tilting out-of-plane mode high-Q mechanical silicon oscillator. Journal of Micromechanics and Microengineering, volume 15, number 10, pages 1848-1853. © 2005 Institute of Physics Publishing (IOPP). By permission.
  2. N. Chekurov, M. Koskenvuori, V.-M. Airaksinen, and I. Tittonen. 2007. Atomic layer deposition enhanced rapid dry fabrication of micromechanical devices with cryogenic deep reactive ion etching. Journal of Micromechanics and Microengineering, volume 17, number 8, pages 1731-1736. © 2007 Institute of Physics Publishing (IOPP). By permission.
  3. N. Chekurov, K. Grigoras, A. Peltonen, S. Franssila, and I. Tittonen. 2009. The fabrication of silicon nanostructures by local gallium implantation and cryogenic deep reactive ion etching. Nanotechnology, volume 20, number 6, 065307, 5 pages. © 2009 Institute of Physics Publishing (IOPP). By permission.
  4. Nikolai Chekurov, Kestutis Grigoras, Antti Peltonen, Sami Franssila, and Ilkka Tittonen. 2009. Localized gallium doping and cryogenic deep reactive ion etching in fabrication of silicon nanostructures. In: Daryush Ila, Paul K. Chu, Naoki Kishimoto, Jörg K. N. Lindner, and John E. E. Baglin (editors). Proceedings of the 2009 MRS Spring Meeting & Exhibit: Symposium DD – Ion Beams and Nano-Engineering. San Francisco, CA, USA. 13-17 April 2009. Warrendale, PA, USA. Materials Research Society. Materials Research Society Symposium Proceedings, volume 1181, 1181-DD07-01, 6 pages. ISBN 978-1-60511-154-4. © 2009 Materials Research Society (MRS). By permission.
  5. N. Chekurov, K. Grigoras, L. Sainiemi, A. Peltonen, I. Tittonen, and S. Franssila. 2010. Dry fabrication of microdevices by the combination of focused ion beam and cryogenic deep reactive ion etching. Journal of Micromechanics and Microengineering, volume 20, number 8, 085009, 6 pages. © 2010 Institute of Physics Publishing (IOPP). By permission.
  6. Päivi Sievilä, Nikolai Chekurov, and Ilkka Tittonen. 2010. The fabrication of silicon nanostructures by focused-ion-beam implantation and TMAH wet etching. Nanotechnology, volume 21, number 14, 145301, 6 pages. © 2010 Institute of Physics Publishing (IOPP). By permission.
  7. J. P. Pekola, V. F. Maisi, S. Kafanov, N. Chekurov, A. Kemppinen, Yu. A. Pashkin, O.-P. Saira, M. Möttönen, and J. S. Tsai. 2010. Environment-assisted tunneling as an origin of the Dynes density of states. Physical Review Letters, volume 105, number 2, 026803, 4 pages. © 2010 American Physical Society (APS). By permission.

Keywords: silicon, microfabrication, nanofabrication, focused ion beam, deep reactive ion etching

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Last update 2012-07-25