Objective comparison of scanning ion and scanning electron microscope images

Abstract

Common and different aspects of scanning electron microscope (SEM) and scanning ion microscope (SIM) images are discussed from a viewpoint of interaction between ion or electron beams and specimens. The SIM images [mostly using 30 keV Ga focused ion beam (FIB)] are sensitive to the sample surface as well as to low-voltage SEM images. Reasons for the SIM images as follows: (1) no backscattered-electron excitation; (2) low yields of backscattered ions; and (3) short ion ranges of 20-40nm, being of the same order of escape depth of secondary electrons (SE) [=(3-5) times the SE mean free path]. Beam charging, channeling, contamination, and surface sputtering are also commented upon.