Metrological performance of SEM 3D techniques
Author(s): Marinello Francesco1, Carmignato Simone2, Savio Enrico3, Bariani Paolo4, Horsewell Andy5, De Chiffre Leonardo6
Affiliation(s): 1CIVEN - Coordinamento Interuniversitario Veneto per le Nanotecnologie, 2 DTG, University of Padova, 3 DIMEG, University of Padova, 4 Schaefer South-East Europe s.r.l., 5 DTU, Center for Nanoscopy, 6 DTU, Mechanical Engineering
Topic: 4. Image Processing and Simulation
Scanning Electron Microscopes (SEMs) are widely used in industrial and academic research applications due to their ability to imagine surfaces with high spatial resolution and with a large depth of focus. SEM images are purely two dimensional, as they are built up of intensity variations revealed as an electron beam is scanned over the specimen surface (secondary emission detection). Nevertheless the third dimension can be reconstructed by means of a stereo-pair technique. However a prerequisite for 3D-SEM implementation in the quality control, is that calibrations methods have to be developed to establish traceability to metre unit. In this work, an experimental study is presented that addresses the performance of 3D topography calculation and reconstruction, based on secondary electron imaging and stereo-pair technique. The influence of various factors on the quality of the reconstruction is analysed within the paper. In particular the critical role played by the quality of the scanned images, the tilting angle and its relative uncertainty, the magnification and the deviations from the eucentricity condition are studied, in order to define a strategy to optimize the measurements taking account of the critical factors in SEM 3D reconstruction.