Analysis of the image formation mechanism on high energy scanning electronmicroscopy

The image formation mechanism of the high-energy scanning electron microsco py is analyzed by a Monte Carlo simulation of electron trajectories in a sp ecimen. It is shown that only secondary electrons which are produced direct ly by incident primary electrons carry information of the three-dimensional hole structure at the specimen surface. The major contribution to the sign al is due to the secondary electrons emitted from the side-wall of the hole . Even if the hr,le is covered by a 39-nm-thick carbon film, the edge contr ast of the hole is appreciable as the primary electron is incident normal t o the surface. If there is an aperture in the film covering the hole, secon dary electrons from the side-wall of the hole contribute to the signal.