The field of electron and ion optics is based on the analogy between
geometrical light optics and the motion of charged particles in
electromagnetic fields. The spectacular development of the electron
microscope clearly shows the possibilities of image formation by charged
particles of wavelength much shorter than that of visible light. As new
applications such as particle accelerators, cathode ray tubes, mass and
energy spectrometers, microwave tubes, scanning-type analytical
instruments, heavy beam technologies, etc. emerged, the scope of
particle beam optics has been exten- ded to the formation of fine
probes. The goal is to concentrate as many particles as possible in as
small a volume as possible. Fabrication of microcircuits is a good
example of the growing importance of this field. The current trend is
towards increased circuit complexity and pattern density. Because of the
diffraction limitation of processes using optical photons and the
technological difficulties connected with x-ray processes, charged
particle beams are becoming popular. With them it is possible to write
directly on a wafer under computer control, without using a mask.
Focused ion beams offer especially great possibilities in the submicron
region. Therefore, electron and ion beam technologies will most probably
playa very important role in the next twenty years or so.