Three Dimensional Surface Reconstruction using Scanning Electron Microscopy and the Design of a Nanostructured Electron Trap

摘要

This paper gives an overview of the possible methods for a three-dimensional surface acquisition in the micrometer scale. It is pointed out that Scanning Electron Microscopy is a capable method for measurement tasks of this kind; therefore, it presents possible ways for implementing this technique in a three-dimensional surface reconstruction. The improved photometric method promises the best performance; its further implementation is developed and explained. Therefore, some modifications of the employed Scanning Electron Microscope (SEM) are described, for instance, the integration of two supplemental detectors, a modified collector grid and a gun shielding. All modifications were evaluated using FEM-Simulations before their implementation. A signal mixing is introduced in order to still be able to use the improved photometric method with four detectors in spite of the fact that it was designed for a two-detector system. For verification purposes, a sphere normal is measured by means of the modified system. It can be seen that the maximal detectable slope angle could be increased compared to the old photometric method. In addition, we introduce an electron trap consisting of nano structured titanium. The structure is tested regarding its ability to catch electrons of different energies and compared to non structured titanium. The trap can later be implemented on the bottom of the electron gun to catch unwanted backscattered electron (BSE) emission which could otherwise affect the three-dimensional reconstruction.