Metrological performance of SEM 3D techniques

This paper addresses the metrological performance of three-dimensional measurements performed with Scanning Electron Microscopes (SEMs) using reconstruction of surface topography through stereo-photogrammetry. Reconstruction is based on the model function introduced by Piazzesi adapted for eucentrically tilted stereopairs. The work provides a theoretical description of the effects that the main instrumental variables and measurement parameters have on the reconstruction accuracy. Two main classes of influencing factors are recognised: the first one is related to the measurement operation and the instrument set-up; the second concerns the quality of scanned images and represents the major criticality in the application of SEMs for 3D characterizations. In particular the critical role played by 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 optimise the measurements taking account of the critical factors in SEM 3D reconstruction. Investigations were performed on a novel sample, specifically developed and implemented for the tests.