Theoretical study of the ultimate resolution of SEM

SUMMARY This work aims to clarify the problem of why the ultimate resolution assessed experimentally from the observation of 0.8 nm separation of Au‐Pd fine particles is beyond the theoretical resolution limit of scanning electron microscopy (SEM). The correlation between the spatial distribution of secondary electrons on a sample surface and the resolution estimated by edge‐to‐edge separation in SEM was studied by a Monte Carlo simulation with secondary electron generation included. The result clearly indicates that the edge‐to‐edge separation can extend beyond the theoretical ultimate resolution, particularly by image processing for contrast expansion and by improving the signal to noise ratio (S/N).