Radiant energy – Inspection of solids or liquids by charged particles – Electron microscope type
Reexamination Certificate
2006-01-10
2006-01-10
Berman, Jack I. (Department: 2881)
Radiant energy
Inspection of solids or liquids by charged particles
Electron microscope type
C250S307000, C250S310000, C250S398000
Reexamination Certificate
active
06984823
ABSTRACT:
There are provided an electron microscope capable of carrying out focusing and astigmatism correction without depending on characteristics of a sample, and a method for controlling its focus position.The electron microscope according to the present invention comprises: an electron optical system (2); a focus control part (3); an image detecting part (4); a first operating part (11) for mutually dividing first and second transformed images (9) and (10), which are obtained by carrying out the fast Fourier transform of first and second images (7) and (8) detected at two focus positions of a first focus position (f1) and a second focus position (f2) shifted from the first focus position by a known focus shifted quantity Δf, to obtain a measured divided quantity Rexp; divided quantity data (12) previously prepared and stored as a function of focus positions and spatial frequencies as a set of theoretical divided quantities, the theoretical divided quantities being obtained by substituting the two focus positions shifted by the focus shifted quantity Δf for an image transfer function (r,f) to obtain first and second transfer function values K(r;f) and (r;f+Δf) to mutually divide the first and second transfer function values K(r;f1) and (r;f+Δf) on a spatial frequency plane; and a second operating part (13) for making a reference to the divided quantity data (12) to derive a theoretical divided quantity K(r;f0) correlating to the measured divided quantity Rexp, and for deriving a focus position f0corresponding to the derived theoretical divided quantity K(r;f0)/K(r;f0+Δf) as a first focus position f1.
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Baba Norio
Iwaki Masaya
Berman Jack I.
Birch & Stewart Kolasch & Birch, LLP
Riken
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