Apparatus of plural charged-particle beams
One modified source-conversion unit and one method to reduce the Coulomb Effect in a multi-beam apparatus are proposed. In the modified source-conversion unit, the aberration-compensation function is carried out after the image-forming function has changed each beamlet to be on-axis locally, and therefore avoids undesired aberrations due to the beamlet tilting/shifting. A Coulomb-effect-reduction means with plural Coulomb-effect-reduction openings is placed close to the single electron source of the apparatus and therefore the electrons not in use can be cut off as early as possible.
1. A method for converting a single charged particle source into a plurality of virtual sub-sources, comprising steps of:
deflecting, by a plurality of micro-deflectors of a micro-deflector array, a charged-particle beam of the single charged-particle source into a plurality of parallel beamlets forming a plurality of virtual images respectively, wherein each of the plurality of virtual images is one of the plurality of sub-sources;
adding, by a plurality of micro-compensators of a micro-compensator array, aberrations to each of the plurality of virtual images, wherein each micro-compensator of the plurality of micro-compensators is aligned with a corresponding one of the micro-deflectors; and
cutting a current of each of the plurality of beamlets.
2. The method of claim 1 , further comprising:
avoiding radiation damage due to the plurality of beamlets.