Patent ID: 6858844
Filing Date: 2005-02-22
Classification: H01J

Abstract:
1. A method for determining geometrical-optical aberrations up to and including 3rd order in particle-optical, probe-forming systems, in particular scanning electron microscopes that include an essentially punctiform source, which emits a particle beam, lenses for influencing the particle beam, the particle beam having particles that image an object, and a detector for registering the particles or imaging the object, the method comprising: imaging the object by the particle beam, which is focussed on the object; recording the image; repeating the imaging and recording steps utilizing an overfocussed and an underfocused beam, which produce overfocussed and underfocussed images; transforming the overfocussed and underfocussed images in Fourier space; dividing the transformation of the overfocussed image by a transformed focussed image thereby obtaining a first quotient; and dividing the transformation of the underfocussed image by the transformed focussed image, thereby obtaining a second quotient, wherein the first and second quotients are reverse transformed and thereby brightness profiles of the probes, are determined, the asymmetry of the profiles with respect to a center, a width of the profiles, in particular the half-value width, and/or the curvature of the profiles in the center are determined, and wherein differences of the profiles of the probes are used to determine the image aberrations.