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In multi electron beam systems, "Neighbours Matter".

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Summary
This summary is machine-generated.

The Multi Beam Scanning Electron Microscope's aperture lens array can cause fourfold astigmatism due to electrostatic interactions. A proposed correction involves shaping aperture lenses to counteract this aberration, improving beam quality.

Keywords:
ALAInteractionsMBSMBSEMNeighboring-apertures

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Area of Science:

  • Electron Microscopy
  • Optical Physics
  • Materials Science

Background:

  • Multi Beam Scanning Electron Microscopes (MBSEM) utilize aperture lens arrays (ALA) to generate multiple electron beams.
  • Electrostatic interactions between closely spaced apertures in an ALA can induce optical aberrations.
  • A square grid arrangement of apertures leads to a specific aberration: fourfold astigmatism.

Purpose of the Study:

  • To analyze the impact of aperture lens array geometry on beam aberrations in MBSEM.
  • To investigate the phenomenon of fourfold astigmatism caused by electrostatic interactions.
  • To propose and validate a method for correcting fourfold astigmatism.

Main Methods:

  • Three-dimensional (3D) simulations were employed to model the electrostatic interactions and aberration effects.
  • Experimental validation was conducted to confirm the simulation results.
  • A novel correction scheme involving modified aperture lens profiles was developed.

Main Results:

  • The study confirms that closely spaced apertures in an ALA, particularly in a square grid, introduce significant fourfold astigmatism.
  • Simulations and experiments demonstrated the detrimental effect of this aberration on beam spot quality.
  • The proposed correction scheme, using non-round aperture profiles, effectively counterbalances the fourfold astigmatism.

Conclusions:

  • Fourfold astigmatism is an inherent aberration in certain ALA configurations for MBSEM.
  • The electrostatic interactions between adjacent apertures are the primary cause.
  • A practical correction method using tailored aperture lens shapes can mitigate this aberration, enhancing MBSEM performance.