Auto focusing apparatus of scanning electron microscopes

Details Auto focusing apparatus of scanning electron microscopes Auto focusing apparatus of scanning electron microscopes

1994-12-14

1996-04-30

Berman, Jack I.

Radiant energy

Inspection of solids or liquids by charged particles

Electron probe type

250396R, 250397, H01J 3721

Patent

active

055127479

ABSTRACT:
An auto focusing apparatus of a scanning electron microscope includes an auto focusing mechanism which calculates a focus evaluation value, using an electron signal or picture signal generated from a specimen when the specimen is scanned by an electron beam focused by an objective lens, and controls an exciting current of the objective lens according to said focus evaluation value. A focus correction value register and a focus correction mechanism for correcting the focused position determined by the aforementioned auto focusing mechanism by as much as the correction value registered in the focus correction value register are provided.

REFERENCES:
patent: 4514634 (1985-04-01), Lawson
patent: 4724319 (1988-02-01), Shirota
patent: 5032725 (1991-07-01), Kanda
patent: 5198668 (1993-03-01), Yamada
patent: 5313062 (1994-05-01), Yamada
patent: 5393977 (1995-02-01), Okura et al.
patent: 5404012 (1995-04-01), Yamada

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