SHAPED SHADOW PROJECTION FOR AN ELECTRON BEAM COLUMN

摘要

A shaped electron beam column focuses electrons from an electron source (102) to produce a shadow image (114) of a shaped aperture (104) on a writing plane (108). The shadow image of the shaped aperture is the defocused image of a shape aperture. This defocused shadow image is in the object plane (112) of the shaped electron beam column. The shadow image in the writing plane is defocused because an electron beam lens (106) produces a focused image (110) of the electron source off the writing plane. The size of the shadow image on the writing plane may be altered by adjusting the electron beam lens to change the distance between the electron source image and the writing plane, i.e., defocus. Thus, a relatively large shaped aperture may be used in comparison to shaped apertures used in conventional electron beam columns. Further, only a small total linear demagnification may be used, which permits the length of the shaped electron beam column to be decreased. Consequently, the electron-electron interactions are reduced resulting in increased edge resolution of the image on the writing plane and increased current in the shaped electron beam column thereby increasing throughput.