US3925706A - Field emission electron gun device of the automatic control type - Google Patents

Field emission electron gun device of the automatic control type Download PDF

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Publication number
US3925706A
US3925706A US410444A US41044473A US3925706A US 3925706 A US3925706 A US 3925706A US 410444 A US410444 A US 410444A US 41044473 A US41044473 A US 41044473A US 3925706 A US3925706 A US 3925706A
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Prior art keywords
cathode
anode
electron
control electrode
disposed
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US410444A
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English (en)
Inventor
Setsuo Nomura
Tsutomu Komoda
Yasushi Nakaizumi
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Hitachi Ltd
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Hitachi Ltd
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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
    • H01J37/24—Circuit arrangements not adapted to a particular application of the tube and not otherwise provided for
    • H01J37/243—Beam current control or regulation circuits
    • 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

  • ABSTRACT A field emission electron gun device wherein the quantity of electrons in the electron beam is automatically controlled by means of a control electrode disposed adjacent the cathode.
  • the control electrode is disposed behind the cathode tip in the direction of beam projection so that the electron optical characteristics will not deteriorate although the voltage applied to the control electrode varies.
  • the present invention relates to a field emission electron gun, and more particularly to a field emission electron gun wherein the emission cur-rent is automatically controlled.
  • the ordinary field emission electron gun has several disadvantages, one of which relates to the fact that the stability of the generated electrons is not as good as that provided by a thermionic emission gun.
  • an emission current control electrode may be added to an ordinary field emission electrode gun which comprises a cathode, a first anode and a second anode, and the potential of the emission current control electrode (Va) is controlled automatically with respect to the changes of the quantity of electrons in the electron beam (le).
  • the electron gun is referred to as a field emission electron gun of the automatic control type, by which a very stable electron beam may be obtained.
  • this type of electron gun has certain disadvantages with respect to the electron optical characteristics thereof. That is, the attachment of an emission current control electrode has the same effect as a weak electrostatic lens disposed between the cathode and the first anode.
  • the potential of the control electrode Ve which also determines the focal distance fe of the lens, continuously varies so as to maintain the magnitude of the electron beam current Ie at a predetermined value
  • the electron optical characteristics i.e., the position of the convergence point of the electron beam
  • this type of electron gun fails to provide a sufficient convergence of the electron beam in a practical device such as an electron microscope of the scanning type so that it may not be usable in such a device where a very fine electron beam is required.
  • the object of the present invention is to provide a field emission electron gun of the emission current automatic control type, in'which the electron optical emission electron gun in such a manner that the surface of the first anode opposed to the cathode is semispherical with the tip of the cathode at the geometric center thereof and the emission current control elec- 5 trode is disposed more adjacent to the cathode body than the tip of the cathode (opposed-side of the first anode as seen from the tip of cathode).
  • FIG. 1 is a schematic diagram of an embodiment of a field emission electron gun of the automatic control -'type in accordance with the present invention
  • FIG. 2 is a graph showing the functional relationship between f0 and Ve when an emission current control electrode is disposed in front of the tip of the cathode and at the rear thereof;
  • FIG. 3 is a graph showing the functional relationship between f0 and Ve when the surface of a first anode opposed to the cathode is cut flat and semi-spherically.
  • FIG. 1 there is generally shown an example of a field emission electron gun system of the automatic control type, which comprises a cathode l 1, an annularly or cylindrically shaped emission current control electrode 12, a first anode 13, an accelerating anode l4 and a specimen 15.
  • the control electrode 12 is disposed at the rear portion behind the tip of the cathode 11.
  • the anode 13 is cut in such a manner that it has a semi-spherical or hemispherical surface on the side thereof facing the cathode 11.
  • An accelerating voltage generating source 16 is connected to anode 13 and a cathode heating power source 17 is connected in series with source 16 to the cathode 11.
  • the electron beam which is directed to the specimen 15 is detected by a detecting known device 20, from which output signals are fed to a control device 19 to adjust the control potential level Ve of the control voltage source 18 to a proper value.
  • the detecting device 20 measures the value of the beam current derived from the specimen 15 by way of a resistor 21 connected between the specimen and ground.
  • the potential across resistor 21 is measured by an amplifier 23 connected via a variable capacitor 22 to the resistor 21 so that variations in the current through resistor 21 produce a signal output from amplifier 23, which signal is applied in control of voltage source 18.
  • the operation by which the voltage Ve of the emission current control source 18 is automatically 'controlled in order to maintain the magnitude of the electron beam current to a given value is similar to that of the aforementioned field emission electron gun of the automatic control type. It is preferable that changes in the electron optical characteristics of the electron beam corresponding to the changes in voltage Ve (Ave) be as small as possible. It has been suggested that the electron optical characteristic of the electron beam is represented by the convergence position (f0) of the electron beam. Therefore, the changes in the electron optical characteristic of the electron beam can be reduced by decreasing the changes info (Afo) corresponding to A Ve.
  • FIG. 2 shows the measurements of the functional relationship between f and Ve when the emission current control electrode 12 is displaced.
  • FIG. 3 shows the measurements of the functional relationship between f0 and Ve when the first anode is changed in shape.
  • f0 represents the imaginary convergence position (imaginary light source position) of the electron beam at the side of the cathode 11, and its magnitude indicates the value measured in the direction from the tip of cathode 11 to the opposed side of the first anode 13.
  • the length between the cathode 11 and the first anode is 33mm
  • the voltage across the cathode l1 and the first anode is 3KV.
  • the curve 100 shows the functional relationship between f0 and Ve when the emission current control electrode 12 is placed in front of the cathode tip
  • the curve 200 shows the functional relationship between f0 and Ve when it is placed at the rear of the cathode tip as seen in FIG. 1.
  • the curve 101 shows the functional relationship between f0 and Ve when the surface of the first anode 13 is flat on the side facing cathode 11.
  • a curve 201 shows the functional relationship between f0 and Ve when the surface of anode 13 facing cathode l 1 is semi-spherical with the cathode tip positioned at the geometric center thereof.
  • the value Afo/AVe can be reduced by providing the emission current control electrode 12 at the rear of the tip of cathode 11.
  • the value Afo/AVe can be reduced by forming the surface of anode 13 facing cathode 11 to be semi-spherical with the cathode tip at the geometric center thereof.
  • the value of Afo/AVe when the surface of the first anode 13 is semispherical becomes less than percent of that when the surface is flat.
  • the magnitude of the variation is the same as the effect due to chromatic aberration which existed in the ordinary field emission electron gun.
  • a very fine electron beam may be maintained. That is, a very fine and stable electron beam can be obtained without deteriorating the electronic optical characteristics by means of the field emission electron gun of the automatic control type, as provided in accordance with the present invention.
  • the purpose of the invention may be sufficiently accomplished by either providing the emission current control electrode 12 at the rear of cathode tip or cutting the surface of the first anode 13 in a semi-spherical shape, or both methods may be carried out together.
  • an electron gun device of the field emission type for generating an electron beam having a disposed along a beam path a cathode having an electron emitting surface, a first anode and a second anode, and further including means for applying an electric voltage between said cathode and said first anode so as to produce an electric field therebetween which causes electrons to be emitted from said cathode toward said first and second anodes, and means for detecting the electron beam current
  • the improvement comprising a substantially cylindrically shaped control electrode the entire length of which is disposed behind the electron emitting surface of said cathode with respect to the direction of electron emission and voltage control means responsive to said detection means for applying a variable voltage to said control electrode whereby the field emission current from said cathode is controlled in accordance with the output from said detecting means.
  • an electron gun device of the field emission type for generating an electron beam having disposed along a beam path a cathode, a first anode and a second anode, and further including means for applying an electric voltage between said cathode and said first anode so as to produce an electric field therebetween which causes electrons to be emitted from said cathode toward said first and second anodes, and means for detecting the electron beam current
  • the improvement comprising a control electrode disposed in the vicinity of said cathode and voltage control means responsive to said detection means for applying a variable voltage to said control electrode, whereby the field emission current from said cathode is controlled in accordance with the output from said detecting means, said first anode having a hemispherical surface facing said cathode with said cathode being disposed at the geometric center thereof.
  • an electron gun device of the field emission type for generating an electron beam having disposed along a beam path a cathode, a first anode and a second anode, and further including means for applying an electric voltage between said cathode and said first anode so as to produce an electric field therebetween which causes electrons to be emitted from said cathode toward said first and second anodes, and means for detecting the electron beam current
  • said first anode has a hemispherical surface facing said cathode with said cathode being disposed at the geometric center thereof.
  • an electron gun device of the field emission type for generating an electron beam having disposed along a beam path, in sequential order, a cathode, a first anode and a second anode, and further including means for applying an electric voltage between said cathode and said first anode, so as to produce an electric field therebetween which causes electrons to be emitted from said cathode toward said first and second anodes, and means for detecting the electron beam current
  • said first anode has a surface which faces said cathode, said surface being non-linearly sloped.
  • an electron gun device of the field emission type for generating an electron beam having disposed along a beam path a cathode, a first anode and a second anode, and further including means for applying an electric voltage between said cathode and said first anode, so as to produce an electric field therebetween which causes electrons to be emitted from said cathode toward said first and second anodes, and means for detecting the electron beam current
  • said first anode has a concave surface which faces said cathode.
  • control electrode disposed in the vicinity 6 of said cathode and voltage control means, responsive to said detection means, for applying a variable voltage to said control electrode.
  • cathode is a point source cathode and said control electrode is a cylindrically shaped electrode surrounding the body of said cathode behind said cathode tip.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electron Sources, Ion Sources (AREA)
US410444A 1973-02-23 1973-10-29 Field emission electron gun device of the automatic control type Expired - Lifetime US3925706A (en)

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JP48021287A JPS49112565A (enrdf_load_stackoverflow) 1973-02-23 1973-02-23

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US3925706A true US3925706A (en) 1975-12-09

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JP (1) JPS49112565A (enrdf_load_stackoverflow)
DE (1) DE2353872A1 (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5025196A (en) * 1986-06-02 1991-06-18 Canon Kabushiki Kaisha Image forming device with beam current control

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4786844A (en) * 1987-03-30 1988-11-22 Rpc Industries Wire ion plasma gun
US4749911A (en) * 1987-03-30 1988-06-07 Rpc Industries Ion plasma electron gun with dose rate control via amplitude modulation of the plasma discharge
US8938333B2 (en) 2012-06-27 2015-01-20 Bose Corporation Active wheel damping
US9102209B2 (en) 2012-06-27 2015-08-11 Bose Corporation Anti-causal vehicle suspension

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3659135A (en) * 1969-11-22 1972-04-25 Philips Corp Electron gun having cathode with cylindrical extension and control grid with conical section
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
US3760383A (en) * 1971-07-01 1973-09-18 Gen Electric Erration storage system with collimated electron beam for minimal spherical ab
US3786305A (en) * 1972-05-15 1974-01-15 Hitachi Ltd Field emission electron gun

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3659135A (en) * 1969-11-22 1972-04-25 Philips Corp Electron gun having cathode with cylindrical extension and control grid with conical section
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
US3760383A (en) * 1971-07-01 1973-09-18 Gen Electric Erration storage system with collimated electron beam for minimal spherical ab
US3786305A (en) * 1972-05-15 1974-01-15 Hitachi Ltd Field emission electron gun

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5025196A (en) * 1986-06-02 1991-06-18 Canon Kabushiki Kaisha Image forming device with beam current control

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DE2353872A1 (de) 1974-08-29
JPS49112565A (enrdf_load_stackoverflow) 1974-10-26

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