Electron beam lithography system

Claim 1

An E-beam system for writing a pattern on a wafer comprising: an electron source and means for accelerating an electron beam (10) along a system axis (102) and through an illuminating aperture (20); first magnetic focus means, having a first focal length, (8) disposed along said system axis, having a first magnetic symmetry axis, and intercepting said electron beam for operating on said electron beam emerging from said illuminating aperture; first and second deflection means (32, 34) disposed along said system axis between said first magnetic focus means and said reticle for displacing said electron beam so that said electron beam travels along a reticle axis (104) parallel to said system axis and intersecting an nth reticle subfield; a first section of a second magnetic focus means (40), having a second focal length, and disposed along said system axis between said first magnetic focus means and a reticle, having a second magnetic symmetry axis, and intercepting said electron beam, said first magnetic focus means and said first section of said second focus means cooperating to focus said displaced electron beam to form an image of said illuminating aperture on a reticle (204), said image of said illuminating aperture covering said nth reticle subfield of a plurality of N noncontiguous reticle subfields of said reticle that are separated from one another by a subfield separation distance, said nth subfield intercepting said reticle axis and containing at least 10 4 pixels, whereby all of said pixels of said nth subfield are exposed to said beam simultaneously, a second section of said second magnetic focus means disposed along said system axis between said reticle and said wafer for operating on said electron beam from said subfield; third deflection means (66) disposed along said system axis and intercepting said electron beam from said third focus means travelling along said reticle axis for deflecting said electron beam back toward said system axis and through a pivot point on said system axis; fourth deflection means (68) disposed along said system axis and intercepting said electron beam for deflecting said electron beam from said third deflection means to a wafer axis (106) parallel to said system axis and on the opposite side of said system axis from said reticle axis; third magnetic focus means (52) disposed along said system axis, having a third magnetic symmetry axis and intercepting said electron beam from said fourth deflection means, said third magnetic focus means cooperating with said second section of said second magnetic focus means to focus an image of said reticle subfield carried by said electron beam on a corresponding nth wafer subfield of a plurality of N contiguous wafer subfields on a wafer (224), each of said second and third magnetic focus means including magnetic axis-shifting means (43, 45, 53) for controllably translating magnetic fields of said magnetic focus means such that said magnetic fields are substantially parallel to and azimuthally symmetric about said reticle axis and said wafer axis, respectively, whereby said second magnetic symmetry axis is coincident with said reticle axis and said third magnetic symmetry axis is coincident with said wafer axis; and a controller connected to said source, said second magnetic focus means, and said third magnetic focus means for controlling the electron beam duration, said first, second, third, and fourth beam deflection means and said magnetic fields of said second and third magnetic focus means and said magnetic axis-shifting means.