Effect of increasing the coefficient of backscattered electrons for multilayer nanostructures and image contrast inversion in scanning electron microscopy

We discuss the reasons for an increase in the coefficient of backscattered electrons (BSEs) for multilayer film nanostructures during their study with a scanning electron microscope (SEM) and consider the conditions for the occurrence of contrast inversion of their images. A complete analytical expression for the signal detected in the BSE regime by an SEM is derived for the first time for multilayer nanostructures. Solving direct and inverse problems relating the signal values to the composition of a three-dimensional sample as a function of the energy of probe electrons allows the thicknesses and depths of nano-objects to be determined in a matrix array with high spatial resolution. The main calculations in this paper are performed using refined empirical formulas corresponding to the experimental data obtained by the authors or presented in the cited literature.