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Eingeladener Vortrag
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A reference material for calibration and testing of instruments with nanometric lateral resolution
(2002)
Ringversuch zur Bestimmung von Stufenhöhen im Nanometerbereich mit der Rasterkraftmikroskopie
(2003)
A new type of test sample for the determination of lateral resolution in surface analysis is presented. The certified reference material BAM-L002 Nanoscale strip pattern for length calibration and testing of lateral resolution is an embedded cross-section of epitaxially grown layers of AlxGa1-xAs and InxGa1-xAs on GaAs substrate. The surface of the sample provides a flat pattern with strip widths of 0.4-500 nm. The combination of gratings, isolated narrow strips and sharp edges of wide strips offers improved possibilities for the calibration of a length scale, the determination of lateral resolution and the optimization of instrument settings. The feasibility of the reference material for an analysis of lateral resolution is demonstrated for SIMS.
Results of the inter-laboratory comparison "Determination of nanometric step heights with AFM"
(2001)
Zusammenfassung
Some methods of nano-scale analysis are on the threshold of being a standard method in industry and therefore quality assurance becomes important. But, at the present time, there are deficits in standardisation and validation of these methods. Therefore, we have organised method comparisons and interlaboratory comparisons to overcome these deficits. We report the results of an interlaboratory comparison in step-height determination by atomic force microscopy and the development of a reference material for laterally resolving methods of material analysis.
Zum Stand des Ringversuchs "Stufenhöhen" und erste Auswertung der Umfrage zur QS in der Nanoanalytik
(2000)
Lateral resolution of secondary ion mass spectrometry - results of an inter-laboratory comparison
(2007)
Recently, BAM organised an inter-laboratory comparison focussed on lateral resolution and accuracy of sub-micron length measurements by secondary ion mass spectrometry (SIMS). Results were submitted by 16 laboratories from 10 countries. The task was to analyse a cross-sectioned semiconductor multilayer stack. The resulting strip pattern in the surface of the sample shows narrow strips, step transitions and gratings of different periods. Imaging analysis of this pattern enables the determination of relevant parameters related to the lateral resolution: (i) The width (FWHM) of the primary ion beam, (ii) the distance between 16% and 84% intensity points in a profile across the image of a step transition and (iii) the modulation of intensity in the images of gratings with different periods. The parameter's data reported by the participants vary in a wide range. A strong variation in the data of primary ion beam width was observed for results measured with the same type of instrument. The distance between two narrow strips was measured with high accuracy. Twelve of sixteen of the submitted values are within the limits of uncertainty of the reference value 964 ± 35 nm. This result shows that the calibration of the length scale of the SIMS instruments is already rather precise in most of the participating laboratories.
Further progress in the spatial resolution of X-ray microscopes is currently impaired by fundamental limitations in the production of X-ray diffractive lenses. Here, we demonstrate how advanced thin film technologies can be applied to boost the fabrication and characterization of ultrahigh resolution X-ray optics. Specifically, Fresnel zone plates were fabricated by combining electron-beam lithography with atomic layer deposition and focused ion beam induced deposition. They were tested in a scanning transmission X-ray microscope at 1.2 keV photon energy using line pair structures of a sample prepared by metalorganic vapor phase epitaxy. For the first time in X-ray microscopy, features below 10 nm in width were resolved.
Lateral resolution, also called image resolution, is the most relevant quality parameter of maps and line scans. Therefore well defined procedures for the determination of lateral resolution are required. In the surface analysis community different definitions of lateral resolution are in use and there is no generally accepted method for the determination of lateral resolution which meets the demands of the state-of-the-art in surface analysis. We propose the determination of lateral resolution by imaging of well defined square-wave gratings with finely graded periods. This method enables the real time estimation of lateral resolution and the adjustment of instrument settings with respect to lateral resolution. The effect of noise and contrast on lateral resolution has been analysed by numerically simulated images of square-wave gratings. A new resolution criterion has been developed which is based on the dip-to-noise ratio and takes into account the sampling step width by introducing a "reduced noise". The contrast transfer function has been introduced and its relation to lateral resolution in the presence of noise was analysed. For that reason an "effective cut-off frequency" was defined which is the reciprocal of the lateral resolution. Normalized values of lateral resolution and their relation to signal-to-noise ratio and sampling step width were given for Gaussian and Lorentzian line spread functions. These values enable the calculation of experimental parameters which are necessary to get a required value of lateral resolution. Finally the successful application of the proposed approach to determine lateral resolution has been demonstrated by ToF-SIMS element mapping of the certified reference material BAM-L200.
Development of reference materials for surface technology in the micrometer and nanometer range
(2004)