Device and method for forming a plurality of charged particle beamlets

A charged particle beam device comprising:

• a charged particle source and a multi-aperture plate, the multi-aperture plate comprising an inner aperture for passing an inner beam of charged particles and a plurality of outer apertures, each for passing one of a plurality of outer beamlets of charged particles;
• each of the outer apertures being substantially equidistant from an optical axis;
• an objective lens configured to focus the outer beamlets, uncompensated for a field curvature aberration, to a plurality of focal points on a virtual ring having a center along the optical axis, the objective lens configured to subject the outer beamlets to the field curvature aberration which axially displaces the virtual ring relative to a virtual focal point of an uncompensated inner beamlet;
• and
• a compensation lens, located between the charged particle source and the objective lens, configured to operate on the inner beamlet to form a compensated inner beamlet, the compensation lens configured to axially offset a compensated focal point of the inner beamlet from the virtual focal point,
• such that the compensated focal point of the compensated inner beamlet is coplanar with the virtual ring.

A charged particle beam device comprising:

• a charged particle source and a multi-aperture plate, the multi-aperture plate comprising an inner aperture for passing an inner beam of charged particles and a plurality of outer apertures arranged in a hexagon shape for passing a plurality of outer beamlets;
• an objective lens configured to focus inner beamlet and the plurality of outer beamlets, and configured to subject each of the outer beamlets to a field curvature aberration, the outer beamlets being uncompensated for the field curvature aberration induced by the objective lens;
• and
• a compensation lens, located between the charged particle source and the objective lens configured to compensate only the inner beamlet such that the objective lens focuses the inner beamlet onto the same plane as the focii of the outer beamlets.