The ability to measure step height and to calibrate step height artefacts is of vital interest in nanometrology. On that score the WGDM7 decided in 1998 to include measurements of step heights in a series of comparisons on the field of nanometrology.The comparison about step height (NANO2) started in September 2000 with the Physikalisch-Technische Bundesanstalt (PTB) as pilot laboratory. Fourteen national metrology institutes worldwide participated in this comparison. A set of five step height standards in the range from 7 nm to 800 nm was used for the comparison. The lateral size of the structures of the step height standards was chosen so that the height could be measured by different types of instruments, for example, interference microscopes, stylus instruments and scanning probe microscopes (SPM). The reference values were calculated as the weighted mean of all measurements that fulfilled the En < 1 criteria.Most of the results were in good agreement with the reference values. It is noticeable that the results obtained by different types of instruments are quite compatible. Also this comparison is the first comprehensive test of the reliability of SPM and their suitability for traceable measurements of step heights. Further it was shown that today step heights on samples can be measured with uncertainties in the sub-nanometre range. Differences in the calculation of the uncertainty depend on the types of instruments and on the users. For each class of instrument, e.g. SPM, it would be meaningful to homogenise these models. Hence the results of this comparison are of great importance in many respects.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the Mutual Recognition Arrangement (MRA).

A commercial scanning force microscope (SFM) has been modified by the incorporation of three miniature laser interferometers, and new calibration methods have been applied so that requirements resulting from traceability of measurement results to metrological primary standards can be better fulfilled. The progress attainable in this way refers to the accurate positioning of the probe with respect to the points to be sampled on the surface. The paper gives a brief introduction to the SFM and the interferometers, the approach to three-dimensional calibration of the SFM, selected calibration results and the compensation of calibration errors by the control software of the SFM. The SFM is applied to the determination of the coating thickness of corresponding artefacts. These results are consistent with those achieved by interference optical microscopy.A commercial scanning force microscope (SFM), VERITEKT 3 [1], is used to determine the surface topography of microstructures (e.g. artefacts for the thickness of coatings [2], optical gratings [3] and microhardness indenters [4]). The measurement results must be traceable to metrological primary standards.In the past, we calibrated the SFM by reference to calibrated artefacts [2]. To further improve its accuracy, we have fitted in the SFM a laser-interferometric 3D measurement system consisting of three miniature laser interferometers [5].The impulses emitted by the interferometers during movements along the axes can be used to generate calibration points within the measurement range of the SFM. The interferometers offer the opportunity to determine the metrological performance of the SFM -the performance of the scanner unit in particular -more completely and more suitably than is possible with other approaches known to date.As regards traceability, we understand the SFM to be a kind of miniature three-coordinate measuring system. Independent of the strategy on which the calibration is based, we have as the final calibration result regression functions which * Corresponding author describe the spatially dependent non-linearity and the crosstalk in the direction of the axes, and, in addition, functions which reflect displacements of the specimen in the x-and ydirections due to Abbe errors.For all three axes, compensation functions or data sets derived from these have been implemented in the SFM's control software. The consequence of this compensation by software is that nearly perfect calibrated equidistant scales and orthogonal axes of movement are obtained. The SFM is then capable of performing dimensional measurements with uncertainties of only a few nanometers.The SFM, with the incorporated laser interferometers, calibration results referring to a kind of pre-calibration and further evaluations revealing the 3D nature of the performance of the SFM, is described in [6]. This paper covers: -a brief introduction to the SFM and the interferometers -the approach to 3D calibration of the SFM and selected calibration results -a comparison of the results of the calibration...

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