Numerous largely unpredictable criticalities of operating parameters arise in
electron beam projection
lithography systems to maintain
throughput comparable to optical projection
lithography systems as minimum feature size is reduced below one-half micron and resolution requirements are increased. Using an
electron beam projection
lithography system having a high emittance
electron source, variable axis lenses, curvilinear
beam trajectory and constant
reticle and / or target motion in a dual scanning mode wherein the target and / or
wafer is constantly moved orthogonally to the direction of beam scan, high
throughput is obtained consistent with 0.1 mu m feature size ground rules utilizing a column length of greater than 400 mm, a beam current of between about 4 and 35 mu A, a
beam energy of between about 75 and 175 kV, a sub-
field size between about 0.1 and 0.5 mm at the target at an optical
reduction factor between about 3:1 and 5:1, a
numerical aperture greater than 2 mrad and preferably between about 3 and 8 mrad and a scan length between about 20 mm and 55 mm.
Reticle and target speed preferably differ by about the optical
reduction factor.