Patent ID: 7659507

Claim:
An automatic method of axial adjustments for use in an electron beam system having: an electron beam source for producing an electron beam; a system of condenser lenses for focusing the electron beam produced from the electron beam source; an objective lens for focusing the electron beam onto a specimen; deflector lenses for scanning the electron beam over the specimen; aberration correction means having plural stages of combinations of electric or magnetic multipole lenses and electric-magnetic compound multipole lenses and acting to correct aberrations in the electron beam; a control power supply for supplying electric signals to the lenses; detection means for detecting electrons emanating from the specimen in response to the scanning; storage means for storing an output signal from the detection means as data about a scanned image; positional deviation computation means for calculating positional deviations of the image based on the data about the scanned image; and control means for calculating an optimum value of electric signal at which an orbit of the electron beam in the aberration correction means is brought into coincidence with a reference orbit based on the calculated positional deviations and sending an instruction to the control power supply such that an electric signal based on the calculated value is supplied to a multipole lens in the first stage of the aberration correction means, said automatic method of axial adjustments comprising the steps of: calculating positional deviations of the image from scanned image data obtained whenever a different intensity of electric signal is supplied to multipole lenses in a stage which is included in said plural stages and whose center is passed through by the reference orbit when plural different electric signals are successively supplied to the multipole lens in the first stage; calculating an optimum value of electric signal based on the electric signals supplied to the multipole lens in the first stage and on the calculated positional deviations; and supplying the optimum value of electric signal to the multipole lens in the first stage.