US3643191A - Electron lens for electron microscope and the like - Google Patents

Electron lens for electron microscope and the like Download PDF

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Publication number
US3643191A
US3643191A US44935A US3643191DA US3643191A US 3643191 A US3643191 A US 3643191A US 44935 A US44935 A US 44935A US 3643191D A US3643191D A US 3643191DA US 3643191 A US3643191 A US 3643191A
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US
United States
Prior art keywords
magnetic
magnetic path
path unit
electron
lens
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Expired - Lifetime
Application number
US44935A
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English (en)
Inventor
Shozo Kasai
Daisaburo Shimizu
Shinjiro Katagiri
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Hitachi Ltd
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Hitachi Ltd
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Filing date
Publication date
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Publication of US3643191A publication Critical patent/US3643191A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement or ion-optical arrangement
    • H01J37/10—Lenses
    • H01J37/14—Lenses magnetic
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement or ion-optical arrangement
    • H01J37/10—Lenses
    • H01J37/14—Lenses magnetic
    • H01J37/141—Electromagnetic lenses

Definitions

  • This invention relates to electron lenses for use in electron microscopes and the like, and more particularly to an electron lens which is provided with means for preventing undesirable deflection of the electron beam due to leakage flux produced by the lens itself or any other flux produced by other sources.
  • Leakage flux is produced more or less by electron lenses used in electron microscopes and the like, and especially the greatest amount of leakage flux is produced by the objective lens among the electron lenses.
  • This leakage flux is objectionable in that the magnetic field of the lens is thereby distributed asymmetrically relative to the optical axis of the electron microscope, resulting in the presence of a magnetic field, that is, a deflecting magnetic field in a direction perpendicular to the optical axis. Since the electron beam is always subjected to deflection by this deflecting magnetic field, the following disadvantages result:
  • the leakage flux is increased and decreased depending on the variation in the exciting current supplied to the electron lens. Accordingly, the electron image of a specimen appearing on the fluorescent screen moves to and fro, each time the exciting current supplied to the electron lens is adjusted.
  • means such as a device for moving the electron gun in the horizontal direction has been provided so as to effect the so-called aligning manipulation for aligning the path of the electron beam with the optical axis.
  • aligning manipulation it is difficult to sufficiently and satisfactorily align the path of the electron beam with the optical axis.
  • Another object of the present invention is to simplify and facilitate the adjusting manipulation by the compensating means.
  • a further object of the present invention is to eliminate the need for mechanically moving the electron gun and the focusing lens in an electron microscope or the like by using an electron lens provided with the compensating means in such an electron microscope or the like.
  • the electron lens according to the present invention is characterized by the fact that the electron lens includes at least one movable magnetic compensating piece which is in partial contact with-a lower magnetic path unit and is moved relative to the lower magnetic path unit by manipulation from the exterior of the lens.
  • FIG. 1 is a schematic view showing the principle of the present invention.
  • FIGS. 2 through 6 are schematic views showing preferred embodiments of the present invention.
  • an exciting coil l' is wound in such a manner as to define a hollow space therein and is covered on its outer peripheral surface with an iron cover I.
  • the upper and lower end surfaces of the exciting coil 1' are covered with an upper magnetic path unit 2 and a lower magnetic path unit 3, respectively.
  • An upper magnetic pole piece 4 and a lower magnetic pole piece 5 are disposed within the hollow space in the exciting coil 1, and a spacer 5' of antimagnetic material is disposed between these two pole pieces 4 and 5.
  • the portion occupied by the spacer 5 alternately may be left in the form of an air gap.
  • the electron lens having a structure as described above further includes a magnetic compensating piece 6 in the form of circular plate of ferromagnetic material in bodily contact with the lower magnetic path unit 3 and a plurality of adjusting screws 7 for causing movement of the magnetic compensating piece 6 relative to the lower magnetic path unit 3.
  • a deflecting magnetic field (hereinafter to be referred to as a compensating magnetic field) appears due to the insertion of the magnetic compensating piece 6.
  • the magnitude and the direction of this compensating magnetic field can be varied by suitably moving and adjusting the position of the magnetic compensating piece 6 by the adjusting screws 7 so that the compensating magnetic field cancels the deflecting magnetic field due to the leakage flux described previously.
  • FIG. 2 An embodiment of the present invention which overcomes the above problem is shown in FIG. 2, in which it will be seen that a magnetic compensating piece 8 is in partial contact with the lower magnetic path unit 3.
  • a part B of the flux B is shunted to the magnetic compensating piece 8 and flows into the lower magnetic path unit 3 again at a portion in the vicinity of the lower magnetic pole piece 5.
  • the flux varies relatively greatly as the magnetic compensating piece 8 is moved to an adjusted position by the adjusting screws 7, and the amount of compensation is substantially proportional to the moving distance of the magnetic compensating piece 8 thereby widening the range of compensation.
  • an airgap 9 is formed in the lower magnetic path unit 3 so that the majority of the flux passes through magnetic compensating pieces 10 thereby directly controlling the magnetic reluctance of the lens.
  • a further embodiment of the present invention shown in FIG. 4 is so constructed that a magnetic compensating piece 11 having such a structure as extending above and beneath the lower magnetic path unit 3 prevents outward flow of the leakage flux produced in the air gap of the lower magnetic path unit 3.
  • a portion of the coil bobbin for the exciting coil 1 serves as a magnetic compensating piece. More precisely, the coil bobbin is composed of portions A and A made of ferromagnetic material and a portion A;, made of antimagnetic material. The portion A for example, may be in partial contact with the lower magnetic path unit 3 and is arranged to be moved to an adjusted position by the adjusting screws 7.
  • Still another embodiment of the present invention shown in FIG. 6 is so constructed that a part of the magnetic compensating piece 12 is inicontact with the lower magnetic path unit 3 adjacent to the lower magnetic pole piece 5.
  • the present invention provides an electron lens which does not deflect the electron beam and has a widened range of magnetic field compensation by virtue of the provision of the magnetic compensating pieces.
  • An electron lens for use in an electron microscope or similar apparatus comprising an exciting coil wound to define a hollow space therein, an iron cover covering the outer peripheral surface of said exciting coil, magnetic path units covering both end surfaces of said exciting coil, magnetic pole pieces disposed in spaced relationship within said hollow space of said exciting coil in contact with said magnetic path units, at least one magnetic compensating piece in partial contact with one of said magnetic path units and movable thereon, and means for moving the partial contact portion of said magnetic compensating piece on said magnetic path unit so as to adjust the reluctance of said magnetic path unit to compensate for the undesirable deflecting magneticfield magnetic path unit includes an annular airgap located between the areas of contact with said first and second flanges so that the majority of flux passes through said magnetic compensating piece.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Electron Beam Exposure (AREA)
  • Electron Sources, Ion Sources (AREA)
US44935A 1969-06-13 1970-06-10 Electron lens for electron microscope and the like Expired - Lifetime US3643191A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP5507769 1969-06-13

Publications (1)

Publication Number Publication Date
US3643191A true US3643191A (en) 1972-02-15

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ID=12988624

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US44935A Expired - Lifetime US3643191A (en) 1969-06-13 1970-06-10 Electron lens for electron microscope and the like

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US (1) US3643191A (enrdf_load_stackoverflow)
GB (1) GB1290240A (enrdf_load_stackoverflow)
NL (1) NL147280B (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2920594A1 (de) * 1978-09-01 1980-03-20 Xerox Corp Bandstuetz- und -steuermodul
FR2491258A1 (fr) * 1980-09-29 1982-04-02 Le N Proizv Dispositif optoelectronique pour appareils a sonde electronique
US4698611A (en) * 1986-12-03 1987-10-06 General Electric Company Passive shimming assembly for MR magnet

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2586559A (en) * 1950-02-23 1952-02-19 Gen Electric Multiple element electron lens arrangement
US2637000A (en) * 1951-02-15 1953-04-28 Magnetic electron -lens

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2586559A (en) * 1950-02-23 1952-02-19 Gen Electric Multiple element electron lens arrangement
US2637000A (en) * 1951-02-15 1953-04-28 Magnetic electron -lens

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2920594A1 (de) * 1978-09-01 1980-03-20 Xerox Corp Bandstuetz- und -steuermodul
FR2491258A1 (fr) * 1980-09-29 1982-04-02 Le N Proizv Dispositif optoelectronique pour appareils a sonde electronique
US4698611A (en) * 1986-12-03 1987-10-06 General Electric Company Passive shimming assembly for MR magnet

Also Published As

Publication number Publication date
GB1290240A (enrdf_load_stackoverflow) 1972-09-20
NL7008534A (enrdf_load_stackoverflow) 1970-12-15
NL147280B (nl) 1975-09-15

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