PCT No. PCT / US96 / 09906 Sec. 371 Date Mar. 9, 1998 Sec. 102(e) Date Mar. 9, 1998 PCT Filed Jul. 6, 1996 PCT Pub. No. WO96 / 41362 PCT Pub. Date Dec. 19, 1996Disclosed are lens apparatus in which a beam of charged particlesis brought to a focus by means of a
magnetic field, the lens being situated behind the target position. In illustrative embodiments, a lens apparatus is employed in a scanning
electron microscopeas the sole lens for high-resolution focusing of an
electron beam, and in particular, an
electron beam having an accelerating
voltage of from about 10 to about 30,000 V. In one embodiment, the lens apparatus comprises an electrically-conducting coil arranged around the axis of the beam and a magnetic
pole piece extending along the axis of the beam at least within the space surrounded by the coil. In other embodiments, the lens apparatus comprises a
magnetic dipole or virtual
magnetic monopole fabricated from a variety of materials, including permanent magnets,
superconducting coils, and magnetizable spheres and needles contained within an energy-conducting coil. Multiple-array lens apparatus are also disclosed for simultaneous and / or consecutive imaging of multiple images on single or multiple specimens. The invention further provides apparatus, methods, and devices useful in focusing
charged particle beams for lithographic processes.