Model improvements to simulate charging in SEM

Abstract

Charging of insulators is a complex phenomenon to simulate since the accuracy of the simulations is very sensitive to the interaction of electrons with matter and electric fields. In this study, we report model improvements for a previously developed Monte-Carlo simulator to more accurately simulate samples that charge. The improvements include both modelling of low energy electron scattering and charging of insulators. The new first-principle scattering models provide a more realistic charge distribution cloud in the material, and a better match between non-charging simulations and experimental results. Improvements on charging models mainly focus on redistribution of the charge carriers in the material with an induced conductivity (EBIC) and a breakdown model, leading to a smoother distribution of the charges. Combined with a more accurate tracing of low energy electrons in the electric field, we managed to reproduce the dynamically changing charging contrast due to an induced positive surface potential.

Local voltage contrast changes in MOSFET using scanning electron microscopy with photoelectron beam technology

“…According to a report by K. T. Arat et al 4,5 , the simulated equilibrium state is reached such that δ ~ 1 for SiO2 in positive charging mode. On the other hand, in a report by T. Thome et al, 6 when the irradiation current density is increased, δ of Al2O3 in the equilibrium state becomes less than 1.…”