Patent ID: 7060986

Claim:
An automated method of correcting aberrations in an electron beam, comprising the steps of: obtaining a first image when the electron beam is in its initial state; obtaining a second image when a cross section of the beam faces in a certain direction and assumes a linear form; obtaining a third linear image facing at right angles to the second image; deconvoluting the second and third images using the first image to thereby measure distance (deviation) of the axis of the electron beam from the center of each image; providing feedback to static electric fields of an objective lens and a multipole aberration corrector so as to eliminate the deviation, thus correcting the deviation of the axis; varying a value of a quadrupole electric field in the initial condition of the beam to create an underfocused state compared with an original state; obtaining a first image in the underfocused state; creating an overfocused state compared with the original state; obtaining a second image in the overfocused state; autocorrelating each of the first and second images with itself to obtain autocorrelation images; measuring degree of defocus of the electron beam from widths of peaks in the autocorrelation images; providing feedback to the quadrupole electric field of the aberration corrector or to the static electric field and quadrupole magnetic field, thus focusing the beam; slightly increasing and decreasing the accelerating voltage of the electron beam in the initial state of the beam and obtaining two images; autocorrelating each defocus of the electron beam caused by the increase or decrease in the accelerating voltage with itself to thereby calculate autocorrelations; providing feedback to the static electric field and quadrupole magnetic field of the aberration corrector based on results of the calculations, thus correcting chromatic aberration; obtaining a first image when the electron beam is in its initial state; varying the value of the quadrupole electric field of the aberration corrector to create an underfocused state compared with the original state; obtaining a second image in the underfocused state; varying the value of the quadrupole electric field to create an overfocused state compared with the original state; obtaining a third image in the overfocused state; deconvoluting the second and third images using the first image; and providing feedback to the quadrupole electric field, hexapole electric field, and octopole electric field of the multipole aberration corrector based on results of the deconvolution so as to reduce aperture aberration in the beam, thus correcting the aperture aberration.