Monte Carlo study of the effective electron beam shape in scanning electron microscopic imaging

Abstract

Theoretical analysis of dimensional measurements made using a scanning electron microscope (SEM) requires a raw image to be corrected for the probe shape of the incident electron beam. In this paper, an effective electron beam shape (EEBS), which differs from the Gaussian profile conventionally assumed in SEM image analysis, was studied using a Monte Carlo simulation method. A model of a focusing electron beam with finite width due to aberration was used in simulating the SEM image of gold particles on a carbon substrate. It was found that the EEBS is local to the electron beam landing position and deviates significantly from the Gaussian profile; it is strongly dependent on both the sample topography and the electron beam focusing condition.