Electron backscattering coefficient from 3D nanostructures and determination of subsurface inhomogeneity depth in a scanning electron microscope

Abstract

In this work, empirical relations are proposed for determination of the coefficient and the energy of backscattered electrons (BSE) depending on target atomic number Z, incident energy ЕВ, and angle α of primary electrons. Analytical expressions for detected signals in the BSE mode in a scanning electron microscope (SEM) have been obtained for homogeneous bulk targets and for three-dimensional nanostructures “thin films on a massive substrate.” An important role of a detector response function in the signal formation in the SEM is shown. An explanation is given for the effect of increasing the BSE coefficient and image contrast inversion on multilayer thin-film nanostructures with a specific sample composition depending on the ЕВ energy. An algorithm for determining the thicknesses and depths of fragments of three-dimensional nanostructures is proposed, based on the solutions to both direct and inverse problems.