Scanning electron beam apparatus

Details Scanning electron beam apparatus Scanning electron beam apparatus

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

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