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SEM Lens Aberration: Astigmatism

SEM Lens Aberration: Astigmatism. Amin Cheraghi Shirazi Jan. 2013 CAMTEC Nanofabrication Workshop. SEM. Lens Aberrations. Spherical Aberration Chromatic Aberration Diffraction Astigmatism. Spherical Aberration. Chromatic Aberration. Diffraction.

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SEM Lens Aberration: Astigmatism

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  1. SEM Lens Aberration:Astigmatism AminCheraghiShirazi Jan. 2013 CAMTEC Nanofabrication Workshop

  2. SEM

  3. LensAberrations • Spherical Aberration • Chromatic Aberration • Diffraction • Astigmatism

  4. Spherical Aberration

  5. Chromatic Aberration

  6. Diffraction • Electrons wavelengths being out of phase • Lens will focus electrons of different phase to a different point • Monochromatic and Coherent

  7. Astigmatism • Non-uniform magnetic field • No perfect cylindrical symmetry

  8. Astigmatism Other Reasons • Micro-structural inhomogeneities • Local variations in the magnetic field strength • Not precisely centered apertures • Apertures contamination

  9. Astigmatism Correction • Stigmators • both in the illumination and imaging system

  10. Thank You!!!

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