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Voltage Contrast Detector for Scanning Electron Microscopy

IP.com Disclosure Number: IPCOM000078521D
Original Publication Date: 1973-Jan-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Touw, TR: AUTHOR

Abstract

In a voltage-contrast detector of the type described by J. R. Banbury and W. C. Nixon in J. Sci. Inst., Ser. 2, Vol. 2, pp. 1055-1059, there is a planar element at specimen potential above the specimen, with an aperture to admit the primary electron beam to the specimen, and to allow secondary electrons to enter the detector. This aperture has previously been of fixed size, large enough not to interfere with scanning of the specimen at low magnifications.

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Voltage Contrast Detector for Scanning Electron Microscopy

In a voltage-contrast detector of the type described by J. R. Banbury and W.
C. Nixon in J. Sci. Inst., Ser. 2, Vol. 2, pp. 1055-1059, there is a planar element at specimen potential above the specimen, with an aperture to admit the primary electron beam to the specimen, and to allow secondary electrons to enter the detector. This aperture has previously been of fixed size, large enough not to interfere with scanning of the specimen at low magnifications.

The voltage contrast is improved by making this aperture directly above the specimen variable in size, adjustable to fit the magnification desired (smaller diameter for higher magnifications). This may be done with a selectable series of discrete aperture sizes or (preferably) with a single continuously-variable aperture such as an iris diaphragm. At each magnification, the variable aperture extends the voltage range of monotonic response in voltage contrast and decreases the effect on response, due to transverse electric fields at the specimen.

These improvements are due to two effects of making the aperture as small as possible, consistent with the scan pattern at each magnification. The first effect is to make the electric field between specimen and detector more uniform. The second effect is to select those electrons least affected by transverse fields, viz. those emitted most nearly normal to the specimen surface. The same benefits may be obtained b...