主权项 |
1. A multi-beam apparatus for observing a surface of a sample, comprising:
an electron source; a condenser lens below said electron source; a source-conversion unit below said condenser lens; an objective lens below said source-conversion unit; a deflection scanning unit below said source-conversion unit; a sample stage below said objective lens; a beam separator below said source-conversion unit; a secondary projection imaging system; and an electron detection device with a plurality of detection elements,
wherein said electron source, said condenser lens and said objective lens are aligned with a primary optical axis of said apparatus, and said sample stage sustains said sample so that said surface faces to said objective lens,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,wherein said electron source generates a primary-electron beam along said primary optical axis, and said primary-electron beam is focused by said condenser lens to become a substantially parallel beam and then incident into said source-conversion unit,wherein a plurality of beamlets of said primary-electron beam exits from said source-conversion unit, said plurality of beamlets respectively passes through said plurality of beam-limit openings and is deflected by said plurality of electron optics elements towards said primary optical axis, and deflection angles of said plurality of beamlets are different;wherein said plurality of beamlets is focused by said objective lens onto said surface and forms a plurality of probe spots thereon, 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, and currents of said plurality of probe spots are limited by said plurality of beam-limit openings,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. |