Comparison between Energy Straggling Strategy and Continuous Slowing Down Approximation in Monte Carlo Simulation of Secondary Electron Emission of Insulating Materials

Secondary electrons are commonly used for imaging in scanning electron microscopes, with applications ranging from secondary electron doping contrast in p-n junctions, line-width measurement in critical-dimension scanning electron microscopy and dimensional parameters evaluation in the production of masks and wafers in the semiconductor industry, to the study of biological samples. This paper describes the secondary electron emission yield calculated using two different Monte Carlo approaches. In the first, based on the energy straggling strategy, one takes into account all the single energy losses suffered by each electron in the secondary electron cascade. This method has been demonstrated to be very accurate for the calculation of the secondary electron yield and of the secondary electron energy distribution as well. An alternative way to calculate the secondary electron yield is based on a continuous slowing down approximation and uses as input the electron stopping power of the material being considered. As this work demonstrates that the secondary electron yields calculated using the two approaches are very close and in agreement with the experiment, the much faster continuous slowing down approximation is recommended. On the other hand, if other physical quantities, such as the secondary electron distributions, are required, the energy straggling strategy should be preferred, even if it requires much longer CPU times, due to its stronger physical background.