Radiant energy – With charged particle beam deflection or focussing – With target means
Patent
1989-11-01
1990-10-02
Berman, Jack I.
Radiant energy
With charged particle beam deflection or focussing
With target means
250396ML, 250310, H01J 3709
Patent
active
049610031
ABSTRACT:
An apparatus for directing a scanned electron beam to a sample along an axis. An objective magnetic lens of a single-pole type focusses the scanned electron beam onto the sample. The objective magnetic lens includes a central pole portion extending along the axis and having a central end face effective to generate a magnetic field for focusing the scanned electron beam onto the sample and a peripheral sleeve portion extending along the axis and having a peripheral edge face effective to form a magnetic circuit between the central end face and the peripheral edge face, the peripheral sleeve portion having an inner radius R. A magnetic shield member is disposed to surround the sample to magnetically shield the same. The magnetic shield member has a central section spaced axially from the central end face of the pole portion a distance L which is not substantially less than R so that the magnetic shield member is not magnetically coupled to the magnetic circuit, and a peripheral section spaced from the peripheral edge face of the peripheral sleeve a spatial gap sufficient to magnetically isolate the magnetic shield member from the magnetic lens.
REFERENCES:
patent: 3870891 (1975-03-01), Mulvey
patent: 4882486 (1989-11-01), Kruit
Berman Jack I.
Seiko Instruments Inc.
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