1 Department of Management Engineering, Technical University of Denmark
The need of measuring narrow structures, in the micro and nano scale, over a broader range, can be satisfied by the use of highly resolving techniques, such as atomic force microscopy (AFM), in combination with probe relocation and data file stitching. At the Technical University of Denmark, research has been carried out over the past years involving an AFM probe mounted on a coordinate measuring machine (CMM). Sensor repositioning by the CMM has made possible the inspection of relatively large samples, which are normally not investigable with AFMs. The latest step in the development of the instrument was the development of stitching software. Successful stitching of AFM scans is demonstrated in this report. Single data files in the millimetre range can be obtained, which are entirely based on AFM probing. High definition of nanostructures can therefore be combined with a measuring range covering applications in micro-technology and in surface metrology. The paper addresses the description of the stitching procedure, its validation, and a more comprehensive metrological evaluation of the AFM-CMM instrument performance. Experimental validation of the method was performed by the use of: • A synthetic image featuring a 2D pattern for testing the stitching code performance • An optical standard containing several line patterns, for testing the whole measuring system (AFM-CMM-software) Quantitative analysis was based on: • Dimensional parameters based on the cross correlation function; these were calculated over the synthetic image, and the result of several partitioning and stitching operations, respectively. • FFT and dimensional measurements performed on the lines patterns resulting from stitching of single AFM scans. Deviations below 1% were experienced when measuring dimensions of several hundreds of micrometers on the stitched data file.