Slit lens arrangement for particle beams

Abstract

A slit lens arrangement for particle beams, and particularly for the projection of a mask onto a workpiece, includes a combined lens, having a cylinder lens and a quadrupole lens, the optical axes of which run parallel to each other, so that the optical axis of the quadrupole lens may be displaced in a parallel manner and which may have a gap-like opening between the pole shoes or in the electrodes with the same spatial relationship to each other. Both lenses are thus so arranged relative to each other, that the focussing of the quadrupole lens occurs in that plane in which the cylinder lens is not focussed, and the defocusing of the quadrupole lens occurs in that plane in which the cylinder lens focuses. Two combined lenses are provided with functionally identical elements arranged such that the optical axes of both lenses lie coaxial to each other, defining the mid-axis of the total system and in which the beam path is telescopic throughout the entire slit lens arrangement. The optical axis of the image is given by the optical axis of the quadrupole. Further, the diffraction plane, or aperture plane, for the total system lies between both combined lenses and fixes a point on the mid-axis, relative to which the combined lenses are arranged, so that the above are anti-symmetric to each other and simultaneously fill the condition that the separation of the first and the second combined lenses from the diffraction plane and the assembly and/or the fields of functionally identical elements in the combined lenses is in a ratio which corresponds to the image scale, preferably, reduction ratio. The shifts of the optical axes of the quadrupole lenses of both combined lenses occur in diametrically opposed directions, such that the size of the shifts are in a ratio to each other which corresponds to the image scale, preferably, the reduction ratio.