Nanoscale imaging and compositional analysis in the helium ion microscope

Nanoscale imaging and compositional analysis in the helium ion microscope

Klingner, N.; Heller, R.; Hlawacek, G.; Möller, W.; Facsko, S.

Ongoing miniaturization in semiconductor industry, nanotechnology and life science demands further improvements for high-resolution imaging, fabrication and analysis of the produced nanostructures. Continuously shrinking object dimensions led to an enhanced demand on spatial resolution and surface sensitivity of modern analysis techniques.
Ion beam analysis performed on nanometer scale may comply with this challenge. Therefore a minimal probe size is required which can be achieved using a Gas Field Ionization Source (GFIS) in a Helium Ion Microscope (HIM). Due to the high brightness of up to 5•109 A•cm-2•sr-1 and the sharp primary ion energy of 30000 ± 1 eV spot sizes of 0.5 nm can be achieved.
Besides the probe size, the nanoscale analysis is limited by the extremely small amount of sample material and the resulting severe ion beam damage. Only the combination of the techniques with highest degree of information could reveal the composition of nanoscale objects.
Secondary Ion Mass Spectrometry (SIMS), as one of the most powerful techniques for surface analysis directly provides information about elemental, molecular and even isotopic composition. However, quantification in mixed layers cannot be done from pure SIMS measurements without comparison to standards. This drawback is partly compensated by Rutherford Backscattering Spectrometry (RBS) but at a loss of sensitivity. In order to combine this compositional information with the high resolution Secondary Electron (SE) imaging correlative microscopy represents the best way.
Recently, we implemented minimal invasive Time of Flight (TOF) spectrometry into the HIM to enable SIMS as well as RBS [1, 2]. The TOF measurements are triggered by blanking the primary ion beam into an existing Faraday cup and release the beam for short time windows to ensure minimal applied fluencies and obtaining a maximum of information from the region of interest.
In the present contribution we intent to present the technical realization of our approach and show results, drawbacks and derive conclusions for the practical use of this promising technique.
[1] N. Klingner, R. Heller, G. Hlawacek, J. von Borany, J.A. Notte, J. Huang, S. Facsko. Ultramicroscopy 162 (2016), 91-97
[2] R. Heller, N. Klingner, G. Hlawacek. Helium Ion Microscopy, Chapter 12, Springer (2016)

Keywords: HIM SIMS Nano TOF

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Publ.-Id: 26186