We describe a metrological large range scanning probe microscope (LR-SPM) with an Abbe error free design and direct interferometric position measurement capability, aimed at versatile traceable topographic measurements that require nanometer accuracy. A dual-stage positioning system was designed to achieve both a large measurement range and a high measurement speed. This dual-stage system consists of a commercially available stage, referred to as nanomeasuring machine (NMM), with a motion range of 25 mm×25 mm×5 mm along x, y, and z axes, and a compact z-axis piezoelectric positioning stage (compact z stage) with an extension range of 2 μm. The metrological LR-SPM described here senses the surface using a stationary fixed scanning force microscope (SFM) head working in contact mode. During operation, lateral scanning of the sample is performed solely by the NMM. Whereas the z motion, controlled by the SFM signal, is carried out by a combination of the NMM and the compact z stage. In this case the compact z stage, with its high mechanical resonance frequency (greater than 20 kHz), is responsible for the rapid motion while the NMM simultaneously makes slower movements over a larger motion range. To reduce the Abbe offset to a minimum the SFM tip is located at the intersection of three interferometer measurement beams orientated in x, y, and z directions. To improve real time performance two high-end digital signal processing (DSP) systems are used for NMM positioning and SFM servocontrol. Comprehensive DSP firmware and Windows XP-based software are implemented, providing a flexible and user-friendly interface. The instrument is able to perform large area imaging or profile scanning directly without stitching small scanned images. Several measurements on different samples such as flatness standards, nanostep height standards, roughness standards as well as sharp nanoedge samples and 1D gratings demonstrate the outstanding metrological capabilities of the instrument.

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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...

The traceability of metrological scanning probe microscopes (MSPMs) is achieved in most cases by laser interferometers. Different means have been adopted to account for the nonlinearity of those interferometers. The thorough investigation of an existing MSPM shows the necessity of interferometrical position measurement with real time full-bandwidth nonlinearity correction. The paper demonstrates that the ellipse parameters of Heydemann nonlinearity correction are sufficiently stable and position independent. This is used in reducing the signal processing time by calculating the ellipse parameters in advance and fixing them during real time nonlinearity correction. As a result, a real time signal processing system with the ability of executing Heydemann correction in 0.32 µs and a complete demodulation in 2.2 µs is designed and implemented. It reduces the residual nonlinearity of interferometers from about 3.5 to <0.3 nm. Some measurement results of a flatness standard illustrate the effectiveness of this new method.

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