A novel approach for accurate and traceable calibration of stylus tip geometry is introduced in the paper. The approach consists of several steps. Firstly, the geometry of an AFM tip is calibrated to a kind of line width standard whose geometry is traceably calibrated to the lattice constant of crystal silicon. Then, the stylus tip to be calibrated is measured by the calibrated AFM tip in an AFM, thus its tip geometry can be accurately determined after the contribution of the AFM tip geometry being corrected from the measured AFM image. After being calibrated, the stylus tip can be applied in measurements of vast microstructures and surfaces, where the measurement results can be in turn corrected using the characterized stylus tip geometry. In such a way, the stylus tip geometry and its measurement results can be finally traceable to the lattice constant of silicon, using this bottom-up approach. Detailed experimental examples are illustrated. For a stylus type RFTHB-50 studied in this paper, its tip radius is measured as 1.727 µm with a standard deviation of 0.007 µm. It is significantly smaller than its nominal value of 2 µm, indicating the need of the calibration. The application of calibrated stylus tip in measurements of microspheres is demonstrated. Compared to conventional tip characterization methods based on tip characterizers the proposed method has advantages of (i) no risk of damaging sharp edges of tip characterizers, (ii) capable of directly characterizing the 3D geometry of stylus tip, (iii) high accuracy.

In this article a new offline method for correcting non-linear drift in all three dimensions (3D) is presented. Using this method, a sample region is measured in multiple sub-measurements, each with increased sampling distance and thus reduced measurement time. The datasets of the sub-measurements are aligned using a point-to-plane iterative closest point algorithm to reconstruct and correct the 3D drift. Afterwards, the corrected datasets are fused into a single dataset. Compared to conventional drift-correction methods, the new method has the advantages of drift correction in full 3D with higher temporal resolution, less extra measurement time and data redundancy, as well as high application flexibility (e.g. compatibility to non-raster sampling). However, the resulting dataset might have slightly decreased resolution. If a high-resolution low-drift dataset is required, the method can be applied in an extended way, where an additional high-resolution measurement is taken whose drift can be corrected by the aforementioned dataset generated by data fusion. Two experimental measurements and a simulation study have been carried out in a new low-noise 3D atomic force microscope, showing great application potential of the proposed method.

We present a new method for traceable calibration of size and form error of microspheres, which was realised by stitching a series of atomic force microscopic (AFM) images measured at different orientations of microspheres using the metrological large range AFM of the PTB. The stitching algorithm is achieved using an iterative closest point (ICP) point-to-plane algorithm. As the AFM tip geometry is one of the most significant error sources for the developed method, it was traceably calibrated to a line width standard (type IVPS100-PTB), whose feature geometry was calibrated with a traceable route to the lattice constant of crystal silicon. Measurement setup, scan strategy, and data evaluation processes have been detailed in the paper. Measurement results show high stability and robustness of the developed method. For instance, the standard deviation of four repeated measurements reaches 5 nm, indicating promising performance.

A method to correct non-linear drift distortions in all three coordinate axes of atomic force microscope (AFM) images is presented. The method uses two measurements of the sample with two fast scan axes orthogonal to each other. Both AFM images are divided into segments and the shifts of the surface features of the segments of both images are determined. From these shifts subsequently the drift of both measurements is calculated. Depending on the segments used, significant non-linearities of the drift can be corrected. The two required measurements for this method do not have to be carried out in direct succession. With this method it is therefore possible to correct drift in an existing AFM image by measuring the sample again later. Although the method has been developed for AFM, it can also be used for other scanning probe microscopes.