Raster shaped beam, electron beam exposure strategy using a two dimensional multipixel flash field
 An electron beam column (or other charged particle beam column) for lithography which exposes a surface to variable shapes in a raster scan. The beam column includes an electron (or ion) source that generates a charged particle beam, a transfer lens, an upper aperture, an upper deflector, a lower aperture, a lower deflector, magnetic deflection coils, and a beam objective lens. The beam is first shaped as a square in cross section by the upper aperture. The upper deflector changes the direction of the square shaped beam to pass through a specific portion of an opening defined in the lower aperture to shape the beam as desired. The lower aperture defines either a cross shaped opening or four L-shaped openings arranged as corners of a square. The combination of upper and lower apertures enable definition of exterior and interior corners as well as horizontal and vertical edges of a pattern, so that only one flash need be exposed in any one location on the surface. The lower deflector reverses any change in direction imposed by the upper deflector and further applies a retrograde scan to counteract a movement of the beam by the magnetic coils in a raster scan. The retrograde scan ensures that an exposure exposes an intended target area. 
Etec Systems, Inc.
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Stephen A. Weidong Allan L. Jeffery K. Lee H.
Rishton Wang Sagle Varner Veneklasen