Sem/fib Stage Calibration with Photogrammetric Methods
نویسندگان
چکیده
Precise sample stage positioning plays an important role for various FIB (Focused Ion Beam) and SEM (scanning electron microscope) applications in microand nanotechnology. During the last few years, FIB instruments have become an indispensable tool for sample preparation, prototyping and micro-machining. Modern FIB devices are equipped with an additional electron column. Such combined SEM/FIB devices not only offer the possibility of forming structures by the focused ion beam, but also to almost instantly image the results in a non-destructive manner with the electron probe. Because of the fact that the ion column and the electron column are located at different positions in respect to each another, the sample has to be orientated normal to the beam by a positioning stage. Within a joint project we investigated the accuracy of SEM/FIB positioning stage operations. Therefore, the repetition uncertainty of the positioning stage was determined by applying photogrammetric methods that were adapted to the microrange for the geometrical calibration of SEMs, and, by using a special 3D calibration structure with control points of approximately 100 nm in diameter (nanomarker). Photogrammetric calibration and analysis of the SEM/FIB system using the nanomarker coordinates worked reliably. The tilting repetition uncertainty of the positioning stage determined by photogrammetric selfcalibration was less than 0.03 degrees, whereas the rotation repetition uncertainty was less than 0.09 degrees. With the resulting measurement uncertainties, metrological analysis of prototyping and micro-machining processes is possible in future.
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