AVS 61st International Symposium & Exhibition
    Helium Ion Microscopy Focus Topic Thursday Sessions
       Session HI+2D+AS+MC-ThA

Paper HI+2D+AS+MC-ThA9
Helium Ion Beam Lithography for Nanoscale Patterning

Thursday, November 13, 2014, 5:00 pm, Room 316

Session: Nanoengineering with Helium Ion Beams
Presenter: Stuart Boden, University of Southampton, UK
Authors: X. Shi, University of Southampton, UK
D.M. Bagnall, University of New South Wales, UK
S.A. Boden, University of Southampton, UK
Correspondent: Click to Email
Electron beam lithography (EBL), the modification of thin films of resist by a focused beam of electrons to create a pattern that is subsequently transferred into the substrate, is a key technology in the development of nanoscale electronic devices. However, with the demand for ever smaller features and pattern dimensions, new lithographic techniques are required to extend beyond existing limits of EBL. One such emerging technology is helium ion beam lithography (HIBL), driven by the development of the helium ion microscope, a tool capable of producing a high intensity beam of helium ions focused to a sub-nanometer spot [1]. Preliminary studies on HIBL using typical EBL resist materials such as PMMA and HSQ have shown that HIBL has several advantages over EBL, including a smaller spot size (potentially leading to higher resolution patterning) and a decrease in the exposure dose required and so the potential for faster pattern definition and therefore higher throughput. Furthermore, proximity effects, which are caused by beam scattering leading to inadvertent exposure of surrounding material, and are problematic when producing high density patterns in EBL, are massively reduced in HIBL [2], [3].

Here, the latest results from an experimental investigation into the HIBL technique will be presented. Areas of PMMA films of various thicknesses are exposed to different helium ion doses. After subsequent development in MIBK/IPA, atomic force microscopy is used to measure residual layer thickness in order to generate exposure response curves for different initial thicknesses of resist. High sensitivity is confirmed with full exposure of 50 nm thick layers achieved with a helium ion dose of only ~2 µC/cm2. Experiments to characterise minimum feature size and proximity effects are currently underway. The use of other high resolution resists will also be investigated with the aim of providing a thorough assessment of the capabilities and limitations of this emerging nano-patterning technique.

[1] L. Scipioni, L. A. Stern, J. Notte, S. Sijbrandij, and B. Griffin, “Helium Ion Microscope,” Adv. Mater. Process., vol. 166, pp. 27–30, 2008.

[2] D. Winston, B. M. Cord, B. Ming, D. C. Bell, W. F. DiNatale, L. A. Stern, A. E. Vladar, M. T. Postek, M. K. Mondol, J. K. W. Yang, and K. K. Berggren, “Scanning-helium-ion-beam lithography with hydrogen silsesquioxane resist,” J. Vac. Sci. Technol. B., vol. 27, no. 6, pp. 2702–2706, 2009.

[3] V. Sidorkin, E. van Veldhoven, E. van der Drift, P. Alkemade, H. Salemink, and D. Maas, “Sub-10-nm nanolithography with a scanning helium beam,” J. Vac. Sci. Technol. B., vol. 27, no. 4, p. L18, 2009.