Apparatus for detecting focused condition of charged particle be

Details Apparatus for detecting focused condition of charged particle be Apparatus for detecting focused condition of charged particle be

1987-11-04

1989-02-14

Anderson, Bruce C.

Radiant energy

Inspection of solids or liquids by charged particles

Electron probe type

250397, G01N 2300

Patent

active

048048402

ABSTRACT:
It is important for the automatic focusing apparatus incorporated in a scanning-type electron microscope to precisely monitor the focused condition of the electron beam. In an apparatus according to the present invention, the signal emanating from a specimen in response to the irradiation of the electron beam is detected, and the resulting signal is differentiated. The differentiated signal is converted into pulses by a voltage-to-frequency converter circuit. The total count of the pulses is used to monitor the focused condition of the electron beam. This permits the focused condition of the beam to be precisely monitored if the detected signal varies greatly in magnitude.

REFERENCES:
patent: 3937959 (1976-02-01), Namae
patent: 4199681 (1980-04-01), Namae
patent: 4214163 (1980-07-01), Namae et al.
patent: 4288692 (1981-09-01), Schamber et al.

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