A method for three-dimensional reconstruction and imaging of surface topography in a scanning electron microscope (SEM) is briefly presented. The method is based on the ‘shape from shadows’ approach and is particularly suitable for relatively smooth surfaces, where stereoscopic methods may be less efficient. The authors used a quadruple secondary electron detector system and new numerical procedures for signal processing, which quite effectively curb main errors inherent in the method. Results of experiments prove that the vertical inaccuracy of the reconstructed shape may be reduced below 10% of the view field dimensions, if local surface inclination angles are less than 65°. Thus, a SEM equipped with the system designed by the authors may serve as a tool for the inspection and measurement of geometrical issues for several classes of micro-mechanical structures.
Summary: This paper is a contribution to development of electron beam profilography based on the so called "shape from shading" technique. A new formula of signal processing in a two detector system has been proposed. The formula cn be applied to all the signals showing Lambert's angular distribution. The signal processing may be realized in "real time" in a simple analog processing system. However, an accuracy of the profiles is limited by numerous errors, mainly by shadowing effects. As the shadowing causes disturbances of the signal flow, a proper design of the detection system is necessary to reduce the errors.
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