Patent ID: 7391034

Claim:
An apparatus for impinging a focused electron beam onto a substrate, the apparatus comprising: an irradiation source of electrons configured to originate electrons for an electron beam; a first non-axisymmetric lens configured to focus the beam in a first linear dimension; a second non-axisymmetric lens configured to focus the beam in a second linear dimension which is substantially perpendicular to the first linear dimension; a third non-axisymmetric lens configured to focus the beam in the first linear dimension; and a fourth non-axisymmetric lens configured to focus the beam in the second linear dimension so as to produce a focused image of the source at an image plane, wherein a first cross-over line is formed along the second linear dimension between the second non-axisymmetric lens and the third non-axisymmetric lens, and wherein a second cross-over line is formed along the first linear dimension between the third non-axisymmetric lens and the fourth non-axisymmetric lens.