Refined physical model for understanding the secondary electron doping contrast mechanism

Abstract

This paper explores the use of secondary electron (SE) doping contrast in scanning electron microscopy (SEM) for visualizing and quantifying doping in silicon carbide (SiC), a vital wide bandgap semiconductor for power electronics. Traditional methods, such as scanning spreading resistance microscopy and scanning capacitance microscopy, face challenges with SiC due to its high hardness. We propose a theoretical model based on potential differences between n- and p-doped areas, differing from the conventional surface band bending theory. The experimental data align well with our model, revealing insights into SE yield variations due to doping concentrations. The study also examines surface patch fields above p–n junctions and the effect of sample bias on SE yield, differentiating the impacts of surface band-bending and external patch fields. Our findings show strong agreement between theory and experiment, explaining contrast characteristics in energy-filtered secondary electron images. This work enhances the understanding of doping contrast mechanisms in SEM, enabling the development of a quantitative dopant profiling method for SiC.