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US 2010/0246993 A1Published application
Method for determining distortions in a particle-optical apparatus
AssigneeFEI Company
InventorsBernd Rieger, Michiel van der Stam
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AssigneeFEI Company
InventorsBernd Rieger, Michiel van der Stam
Estimating the term…
The invention relates to a method of determining the distortions in the projection system of a TEM, and a method of correcting for these aberrations. The aberrations are determined by collecting a large number of images of a sample, the sample slightly displaced between each acquisition of an image. On the images sub-fields (303, 304-i) showing identical parts of the sample are compared. These sub-fields (303, 304-i) will show small differences, corresponding to differential aberrations. In this way the differential aberrations in a large number of points can determined, after which the aberrations for each point can be determined by integration. By now correcting the position of each detected pixel in an image to be displayed, the displayed image has much reduced aberrations. An advantage of the method according to the invention is that no highly accurate steps of the sample are needed, nor is a sample with known geometry needed.
Method of determining distortions in a particle-optical apparatus, said apparatus equipped with:
The method of any of the preceding claims in which the small part of the object is centered round the particle-optical axis on one image and the distortion of the image is determined with the intersection (303) of the particle-optical axis and the image as a reference point.
The method of any of the preceding claims in which the determined sub-image distortions comprise a change in magnification in a first and a second direction and a rotation of the sub-image, all as a function of the position relative to the reference point.
The method of any of the preceding claims in which the sub-image distortions are used to construct a table or formula representing the distortion of the image as a function of the position in the image.
The method of any of the preceding claims in which the sub-image distortions are determined at different magnifications of the projection system and/or different energies of the particles forming the beam of particles.
The method of any of the preceding claims in which at least two of the image comprise multiple sub-images.
Dependencies are inferred from the claim text.