US3811059A - Electron gun device of field emission type - Google Patents

Electron gun device of field emission type Download PDF

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Publication number
US3811059A
US3811059A US00211201A US21120171A US3811059A US 3811059 A US3811059 A US 3811059A US 00211201 A US00211201 A US 00211201A US 21120171 A US21120171 A US 21120171A US 3811059 A US3811059 A US 3811059A
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United States
Prior art keywords
enclosure
disposed
magnetic
focusing lens
electron beam
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Expired - Lifetime
Application number
US00211201A
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English (en)
Inventor
S Katagiri
A Tonomura
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Hitachi Ltd
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Hitachi Ltd
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Publication date
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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
    • H01J37/06—Electron sources; Electron guns
    • H01J37/073—Electron guns using field emission, photo emission, or secondary emission electron sources

Definitions

  • An electron gun device of the field emission type has an enclosure, at least a part of which is of nonmagnetic material, an accelerating electrode having a first and second anode each comprising a magnetic material and disposed in said enclosure, and a focusing lens disposed outside the non-magnetic part of said enclosure, wherein gas is evacuated from said enclosure whereby a high intensity electron beam is obtained.
  • the conventional field emission type electron gun device used for electron microscopes comprises a needle-shaped cathode tip, accelerating electrodes, and a focusing lens for focusing electrons emitted from said tip into a fine beam.
  • This type of electron gun device requires an ultrahigh vacuum such as, for example, pressures below Torr, to maintain a stable field. If the vacuum is 10' Torr, the electron beam from said tip varies by l to 4 percent in terms of the current generated. At such vacuum, the field emission intensity decreases to make the electron gun device substantially impractical.
  • An object of the invention is to provide an electron gun device operable to produce a high intensity electron beam.
  • Another object of the invention is to provide an electron gun device readily capable of providing a very high vacuum.
  • a further object of the invention is to provide an electron gun device which can be constructed into a small size.
  • a still further object of the invention is to provide an electron gun device suited for use as a source of electrons for an electron beam in the electron microscope and the like.
  • an electron gun device in which the accelerating electrode is made of a magnetic material, the walls forming a space in which said accelerating electrode is disposed are made of a non-magnetic material, and said focusing lens is disposed outside said non-magnetic member so that the magnetic flux from the focusing lens is introduced into said accelerating electrode.
  • FIG. I there is shown a conventional electron gun device of the field emission type in which the electron beam emitted from a tip 2 by field emission in a vacuum-tight enclosure 1 is accelerated and converged by an accelerating electrode consisting of a first anode 3A and a second anode 3B, and then is focused by an annular focusing lens consisting of a cylindrical coil 4, a magnetic path 5 and a gap 6.
  • an isolator 7 of the insulating material is interposed between the first and second anodes 3A and 3B.
  • the focusing lens is located inside the enclosure 1 and the magnetic path 5 is of a ferrous metal or the like, the quantity of the gas evacuated through the surface of the magnetic path 5 is inevitably quite large. Because the gas is evacuated in such a manner, there are difficulties in keeping the space 1 at pressures below IO Torr despite the fact that the pressure must be below 10 Torr in order to maintain a stable field emission from the tip 2.
  • the electron gun device in accordance with the present invention is so arranged that, as illustrated in FIG. 2, part of the enclosure 1 is constituted of a non-magnetic material 8, the first and second anodes 3A and 3B are made of a magnetic material, and a focusing lens is disposed in close contact with the outer side of said non-magnetic part 8 of the enclosure 1.
  • a magnetic path 5 is disposed about the coil 4 for the focusing lens so that said first and second anodes may be operable as pole pieces.
  • the enclosure 1 it is sufficient for the enclosure 1 to contain only the first and second electrodes 3A and 3B and insulator 7. This serves to make the quantity of evacuating gas smaller than in the prior art arrangement having the focusing lens in the enclosure 1.
  • the invention also makes it possible to construct the electron beam accelerating parts to be integral with the focusing part, and to reduce the size of the device-as awhole. This is why the inner surface area of the enclosure 1' can be reduced and pressures of about l0 Torr can be maintained inside the spac thereof.
  • an intermediate lensand an objective lens and the like are disposed after the stage formed by said second anode 3B (FIG. 2).
  • the space (not shown diagrammatically) in which said lenses are located communicates with the space in the closure 1 accommodating the intermediate lens and other electrodes, through an aperture 9 provided in the second anode 3B.
  • the space accommodating the intermediate lens, etc., and the space inside the enclosure 1 can be considered to be independent of each other in view of the small size of aperture 9.
  • a pressure difference can be maintained between said two spaces even if the space accommodating the intermediate lens, etc., is of such material as will allow a large amount of gas to escape.
  • the space inside the enclosure 1 where the accelerating electrode is located is not affected by gas evacuation.
  • the magnetic flux produced in the coil 4 and magnetic path 5 of the focusing lens disposed outside the non-magnetic body 8 of the enclosure 1 is introduced through the non-magnetic body 8 into the first and second anodes 3A and 3B of magnetic material.
  • the static electric field and the static magnetic field produce field distributions which are formed simultaneously and independently of each other.
  • said anodes 3A and 3B become operable as an electric field lens and a magnetic field lens as well.
  • the device having a lens capable of forming a magnetic field in addition to an electric field makes it possibleto reduce the amount of aberation in the electron beam by controlling the magnetic field.
  • a high intensity electron beam can be easily realized.
  • ultra-high vacuum conditions can be obtained free of the influence caused by the evacuating gas, and'therefore the intensity of the electron beam can be markedly increased.
  • the invention can be applied to all the electron gun devices of the field emission type which at least comprises a needle-shaped cathode tip, accelerating electrodes, and a focusing lens for thereby focusing the electrons into a beam.
  • a vacuum-tight enclosure made at least in part of non-magnetic material, means in said enclosure for generating an electron beam along a beam path by field emission, accelerating electrode means including a first anode and a second anode each made of magnetic material and being disposed in spaced relationship in said enclosure adjacent the non-magnetic portion thereof along said beam path for accelerating said electron beam, and focusing lens means disposed outside said enclosure adjacent the non-magnetic portion of said enclosure for focusing said electron beam, said nonmagnetic portion of said enclosure being disposed between said accelerating electrode means and said focusing lens means.
  • An electron gun device of the field emission type a vacuum-tight enclosure made at least in part of nonmagnetic material, means in said enclosure for generuting an electron beam along a beam path by field emission, accelerating electrode means including a first anode and a second anode each made of magnetic material and being disposed in spaced relationship in said enclosure adjacent the non-magnetic portion thereof along said beam path for accelerating said electron beam, and focusing lens means disposed outside said enclosure adjacent the non-magnetic portion of said enclosure for focusing said electron beam, said focusing lens being formed by an annular coil and a magnetic cover surrounding all of said coil except an inner annular portion surrounding a central space which forms a lens gap the non-magnetic portion of said enclosure being disposed in said lens gapof said focusing lens.
  • An electron gun device of the field emission type comprising: a vacuum-tight enclosure; means including a cathode tip for emitting an electron beam along a beam path by field emission in said vacuum tight enclosure, accelerating electrode means including a first and a second anode disposed in said enclosure along said beam path for accelerating the electron beam'emitted from said cathode tip, and focusing lens means including a cylindrical coil and a magnetic cover surrounding said coil and having a gap disposed therein for focusing the electron beam passing through said accelerating electrode means;
  • At least a part of said enclosure is formed of a non-magnetic material
  • said first and second anodes being formed of a magnetic material and being disposed inside said enclosure adjacent the part of the enclosure made of non-magnetic material
  • said focusing lens being disposed outside said enclosure adjacent the part of the enclosure made of non-magnetic material so that the nonmagnetic portion of said enclosure is disposed in said lens gap, whereby said first'and second anodes additionally operate as pole pieces for said focusing lens means.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electron Sources, Ion Sources (AREA)
US00211201A 1970-12-24 1971-12-23 Electron gun device of field emission type Expired - Lifetime US3811059A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP45116718A JPS5015109B1 (enrdf_load_stackoverflow) 1970-12-24 1970-12-24

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US3811059A true US3811059A (en) 1974-05-14

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US00211201A Expired - Lifetime US3811059A (en) 1970-12-24 1971-12-23 Electron gun device of field emission type

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JP (1) JPS5015109B1 (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0036618A1 (de) * 1980-03-20 1981-09-30 Siemens Aktiengesellschaft Hochstrom-Elektronenquelle

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1779794A (en) * 1929-06-22 1930-10-28 Westinghouse Electric & Mfg Co Oscillograph
US2468403A (en) * 1946-05-13 1949-04-26 Cathodeon Ltd Electron microscope and other electronic apparatus employing electron lenses
US2619607A (en) * 1951-03-10 1952-11-25 Glaser Steers Corp Internal focusing device
GB1012040A (en) * 1961-05-27 1965-12-08 United Aircraft Corp Apparatus for producing a narrow high-intensity beam of charged particles
US3678333A (en) * 1970-06-15 1972-07-18 American Optical Corp Field emission electron gun utilizing means for protecting the field emission tip from high voltage discharges
US3728570A (en) * 1968-07-07 1973-04-17 Department Of Eng University O Electron probe forming system

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1779794A (en) * 1929-06-22 1930-10-28 Westinghouse Electric & Mfg Co Oscillograph
US2468403A (en) * 1946-05-13 1949-04-26 Cathodeon Ltd Electron microscope and other electronic apparatus employing electron lenses
US2619607A (en) * 1951-03-10 1952-11-25 Glaser Steers Corp Internal focusing device
GB1012040A (en) * 1961-05-27 1965-12-08 United Aircraft Corp Apparatus for producing a narrow high-intensity beam of charged particles
US3728570A (en) * 1968-07-07 1973-04-17 Department Of Eng University O Electron probe forming system
US3678333A (en) * 1970-06-15 1972-07-18 American Optical Corp Field emission electron gun utilizing means for protecting the field emission tip from high voltage discharges

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0036618A1 (de) * 1980-03-20 1981-09-30 Siemens Aktiengesellschaft Hochstrom-Elektronenquelle

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Publication number Publication date
JPS5015109B1 (enrdf_load_stackoverflow) 1975-06-02

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