Shadow imaging of surface topography in a conventional scanning electron microscope by forward scattered electrons

Abstract

A method has been devised to allow shadow imaging of bulk sample surface topography to be carried out in a conventional scanning electron microscope. The electrons that form shadow images are those that strike the surface at a grazing incidence, undergo scattering and take off in the forward direction. Some of these forward scattered electrons are allowed to pass through a small detector aperture, which is placed over a YAG scintillator just beneath the specimen in the horizontal plane. The images are formed in a normal vacuum of about 10 −7 Torr, using either a tungsten or a LaB 6 filament, a probe current of about 100 pA and at 20kV. The resolution in a shadow image is better than 10 nm.