The present invention, in some embodiments thereof, relates to particle beam manipulation and, more particularly, but not exclusively, to particle beam manipulation employing phase modulation.
A scanning electron microscope (SEM) and a scanning transmission electron microscope (STEM) are combined with an electron optical device such as an electron lens to form an extremely small electron beam crossover (hereinafter, will be referred to as a beam probe) on the plane of an observed sample. Transmission scattered electrons, reflected electrons, secondary electrons, or derived X-rays from a small region irradiated by the beam probe are measured to obtain information on the structure and composition of the small region. The electron microscope two-dimensionally scans the beam probe on the plane of a sample by means of an electromagnetic electron beam deflector, obtaining a two-dimensional image.
The resolution of a high-resolution electron microscope is far from being optimal, mainly due to the spherical aberration of the objective lens. Attempts have been made over the years to correct these aberrations. Known in the art are techniques which include taking a series of images of the object under variable objective focus conditions [E. J. Kirkland, Ultramicroscopy 15, 151-172 (1984)], and holographic techniques [A. Tonomura et al, Jpn. J. Appl. Phys. 18, 1373-1377 (1979)]. Also known are techniques that employ quadrupole-octopole [O. L. Krivanek, Ultramicroscopy 78, 1-11 (1999)] or hexapole [M. Haider et al, Nature 392, 768 (1998)] electromagnetic correctors.