Numerical analysis for verifying the performance of lens system in a scanning electron microscope

This work presents an analysis of the lens system in a thermionic scanning electron microscope (SEM) using a numerical computation and an optics-based calculation. The behaviors and characteristics of the electron beam are analyzed and the focusing capability is investigated. The beam spot size is estimated by calculation and proved by experiment. The characteristics and properties determining the SEM performance are investigated for various design parameters through a numerical analysis and an optics-based calculation. Particularly, a combination of two approaches gives more detailed information than a single approach in investigating an extremely small beam spot by demagnification through the electromagnetic lens system in a SEM column.