The method for the reconstruction of complex images of specimens using backscattered electrons

The backscattered electron signal (BSE) is widely used for investigation of specimen surfaces in a scanning electron microscope (SEM). The development of multiple detector systems for BSE signal detection and the methods of digital processing of these signals have allowed for reconstruction of the third dimension on the basis of the two-dimensional (2-D) SEM image. A technique for simultaneous mapping of material composition (COMPO mode) and reconstruction of surface topography (TOPO mode) has also been proposed. This method is based on the measurements of BSE currents sensed by four semiconductor detectors versus the inclination angle of surface. To improve the separation of topographic and material contrasts in SEM, a correction of the TOPO and COMPO modes (resulting from a theoretical description of the system: electron beam, specimen, and detector) was applied. The proposed method can be used for a correct reconstruction of the surface image when the surface slope is <60 degrees. The measuring limit of the slope was closely connected with the detector setup. Next, the digital simulation of the colors was performed (after application of the method of linearization of BSE characteristic versus atomic number). This procedure to increase the SEM resolution for the BSE signal by use of digital image processing allows for a better distinction between the two elements with high atomic numbers.