Apparatus of plural charged-particle beams

A multi-beam apparatus for observing a surface of a sample, comprising:

• an electron source;
• a collimating lens below said electron source;
• a source-conversion unit below said collimating lens;
• a primary projection imaging system below said source-conversion unit;
• a deflection scanning unit below said source-conversion unit;
• a sample stage below said primary projection imaging system;
• a beam separator below said source-conversion unit;
• a secondary projection imaging system above said beam separator;
• and
• an electron detection device with a plurality of detection elements,
• wherein said electron source, said collimating lens and said source-conversion unit are aligned with a primary optical axis of said apparatus, and said sample stage sustains said sample so that said surface faces to said primary projection imaging system,
• wherein said source-conversion unit comprises a beamlet-forming means with a plurality of beam-limit openings and an image-forming means with a plurality of electron optics elements each having a micro-multipole-lens,
• wherein said electron source generates a primary-electron beam along said primary optical axis, and said collimating lens collimates said primary-electron beam into said source-conversion unit,
• wherein a plurality of beamlets of said primary-electron beam respectively passes through said plurality of beam-limit openings and is focused to form a plurality of parallel images of said electron source by said plurality of electron optics elements respectively, and said plurality of beam-limit openings limits currents of said plurality of beamlets,
• wherein said primary projection imaging system projects said plurality of parallel images onto said surface and therefore said plurality of beamlets forms a plurality of probe spots thereon, said micro-multipole-lens of said each electron optics element compensates off-axis aberrations of one corresponding probe spot, and said deflection scanning unit deflects said plurality of beamlets to scan said plurality of probe spots respectively over a plurality of scanned regions within an observed area on said surface,
• wherein a plurality of secondary electron beams is generated by said plurality of probe spots respectively from said plurality of scanned regions and directed into said secondary projection imaging system by said beam separator, said secondary projection imaging system focuses and keeps said plurality of secondary electron beams to be detected by said plurality of detection elements respectively, and each detection element therefore provides an image signal of one corresponding scanned region.

A method to configure a source-conversion unit in a multi-beam apparatus for observing a surface of a sample, comprising:

• providing a beamlet-forming means with a plurality of beam-limit openings;
• providing an image-forming means with a plurality of electron optics elements;
• providing one or more micro-multipole-lenses in each of said plurality of electron optics elements;
• and
• enabling said one or more micro-multipole-lenses to generate a round-lens field, a dipole field and a quadrupole field for compensating field curvature, distortion and astigmatism of one corresponding probe spot of said apparatus.

A method to reduce Coulomb effect in a multi-beam apparatus for observing a surface of a sample, comprising:

• placing a pre-beamlet-forming means between an electron source and a source-conversion unit of said apparatus,
• wherein said pre-beamlet-forming means has a plurality of beamlet-forming apertures which divide a primary-electron beam of said electron source into a plurality of beamlets,
• wherein a plurality of beam-limit openings of said source-conversion unit limits currents of said plurality of beamlets, and
• wherein said source-conversion unit includes one or more micro-multipole-lenses that compensate off-axis aberrations of a corresponding probe spot.

A device for providing multiple sources, comprising:

• a charged-particle source for providing a primary beam along an optical axis of the device;
• means for forming a plurality of parallel images of the charged-particle source and for generating a plurality of dipole fields and quadrupole fields, wherein the plurality of parallel images becomes multiple sources that emit a plurality of beamlets respectively;
• and
• means for selecting currents of the plurality of beamlets with positions of the plurality of parallel images being remained, between the charged-particle source and the imaging means.

A device for providing multiple sources, comprising:

• a charged-particle source for providing a primary beam along an optical axis of the device;
• a lens for condensing the primary beam along the optical axis;
• a plate including a plurality of openings for trimming the primary beam into a plurality of beamlets;
• and
• a plurality of micro-multi pole-lens for respectively focusing the plurality of beamlets to form a plurality of images of the charged-particle source, and providing a plurality of dipole fields and quadrupole fields individually, wherein the plurality of images becomes the multiple sources which emit the plurality of beamlets respectively.