ELECTRON TRAJECTORY TRACKING ALGORITHMS FOR ANALYSING VOLTAGE CONTRAST SIGNALS IN THE SCANNING ELECTRON MICROSCOPE.

Abstract

This paper presents three tracking algorithms for computing the trajectory of secondary electrons in the specimen chamber of the scanning electron microscope (SEM). The potential distribution has been calculated previously with a separate finite-element method. The first algorithm uses a constant time step and the second algorithm uses a step size that spans the entire mesh. Both these algorithms assume a constant electric field between adjacent points of travel of the electron. This assumption introduces inaccuracies especially at low electron energies and in regions where the electric field changes quickly over a small distance. The third algorithm assumes that the electric field varies linearly within a mesh. Simulation results show that this algorithm is reasonably accurate even for electrons with low energies. The advantage of the finite-element method over the finite-difference method for this application are highlighted.