US3890535A - Ion sources - Google Patents

Ion sources Download PDF

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Publication number
US3890535A
US3890535A US296594A US29659472A US3890535A US 3890535 A US3890535 A US 3890535A US 296594 A US296594 A US 296594A US 29659472 A US29659472 A US 29659472A US 3890535 A US3890535 A US 3890535A
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United States
Prior art keywords
electrode
anode
extraction orifice
extraction
pressure
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Expired - Lifetime
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US296594A
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English (en)
Inventor
Guy Gautherin
Jean Aubert
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Bpifrance Financement SA
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Agence National de Valorisation de la Recherche ANVAR
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J27/00—Ion beam tubes
    • H01J27/02—Ion sources; Ion guns
    • H01J27/08—Ion sources; Ion guns using arc discharge
    • H01J27/10—Duoplasmatrons ; Duopigatrons

Definitions

  • the ion source comprises a primary plasma generator constituted by a hot cathode and an anode, between which an arc is produced, and by an intermediate electrode enclosing the arc in proximity to an extraction orifice pierced in the anode.
  • Magnetic field creating means are provided between the intermediate electrode and the extraction orifice, which has a relative small cross-section so that the pressure of the gases occurring inside the primary plasma generator is independent of the pressure existing downstream of the extraction orifice. This pressure downstream of extraction orifice is less than the pressure inside the primary plasma generator.
  • a fifth electrode is arranged downstream of the extraction orifice of the anode and upstream of the extraction electrode and means are provided for applying to this fifth electrode a positive potential with respect to that of the anode and of adjustable value, which is small in absolute value with respect to the potential of the extraction electrode.
  • duoplasmatron an ion source which is constituted by a hot cathode, an intermediate electrode and an anode pierced by an extraction orifice.
  • an arc is produced between the cathode and the anode and this arc is pinched in the vicinity of said extraction orifice by means of, on one hand, an electrostatic effect caused by the intermediate electrode and, on the other hand, by the effect of a magnetic lens whose poles are constituted by the anode and the intermediate electrode, means for the production of a magnetic field being provided to create such a field between the intermediate electrode and the anode, this magnetic field having the axial direction, that is to say the direction of a line joining the hot cathode and the extraction orifice.
  • a plasma formed by a mixture of electrons and positive ions.
  • the extraction orifice has relatively small dimensions.
  • Improvements according to the present invention seek to increase to an appreciable extent, the ion current of the plasma obtained.
  • the ion source according to the invention enables, in addition, variation of the energy of the electrons that it produces, to obtain not only positive ions but also negative ions and, the generation of a plasma composed of neutral particles.
  • the ion source according to the invention is characterised by the fact that it comprises, in addition to the three usual electrodes of the duoplasmatron (that is to say a hot cathode, an intermediate electrode and an anode pierced by an extraction orifice) constituting a primary plasma generator, and the usual downstream extraction electrode a fifth electrode arranged downstream of the extraction orifice of the anode but upstream of the extraction electrode and means for applying to the fifth electrode a positive potential with respect to that of the anode, these means being arranged so that said positive potential has an adjustable value, preferably higher than a critical valve, but much less in absolute value than the potential of the extraction electrode.
  • the duoplasmatron that is to say a hot cathode, an intermediate electrode and an anode pierced by an extraction orifice
  • the usual downstream extraction electrode a fifth electrode arranged downstream of the extraction orifice of the anode but upstream of the extraction electrode and means for applying to the fifth electrode a positive potential with respect to that of the an
  • the fourth electrode has advantageously the shape of an expansion chamber; in this case, this electrode can also comprise means for creating magnetic induction in said chamber.
  • the fifth electrode is advantageously located adjacent the anode without an intervening expansion space.
  • the expansion chamber comprises an orifice for the introduction of gas or vapor intended to be ionised by the primary plasma.
  • said chamber comprises heating means to vaporise solid substances introduced inside this chamber, the vaporised substances being also intended to be ionised.
  • FIG. 1 illustrates a first embodiment of the invention
  • FIG. 2 is a diagram which shows the intensity of the currents of ions and of electrons obtained by the device according to the invention, as a function of the voltage between the fourth electrode and the anode, and
  • FIG. 3 illustrates a second embodiment of the invention.
  • the ion source according to the invention comprises, firstly, in known manner, a primary plasma generator 1 (FIGS. 1 and 3) of the duoplasmatron type.
  • This primary plasma generator is composed of a hot cathode 2, of an intermediate electrode 3 brought to a potential greater than that of the cathode 2 and an anode 4 pierced by an extraction orifice 5 and brought to a potential, generally that of ground, greater than that of the electrode 3.
  • Magnetic field-creating means 3a are provided to create a magnetic field between the intermediate electrode and the extraction orifice.
  • a gas for example hydrogen there is produced an arc between the cathode 2 and the anode 4.
  • This generator 1 then emits a jet of plasma downstream of the extraction orifice 5, this jet of plasma being composed of electrons and primary ions.
  • the extraction orifice 5 has relatively re prised dimensions its cross-section being at the most, equal to 5 mm.
  • the latter feature has the object of enabling the pressure p, of the gases occurring upstream of the anode to be uninfluenced by the pressure p (less than p of the gases occurring downstream of the anode; in other words, the gases downstream of the anode must not reach the cathode 2.
  • the ion source shown in FIG. 1 includes an extraction electrode 18 and also comprises, in addition, according to the invention, a fifth electrode 6 and means 7 for bringing this electrode 6 to a positive potential with respect to the anode 4, whose value is adjustable.
  • this potential is greater than a critical value V
  • the potential of the electrode 6 being positive with respect to that of the anode, there is hence obtained, at the outlet of the duoplasmatron, current of electrons.
  • Means 7 are composed, for example, as in the embodiment of the invention shown in FIG. I, of a direct current source 8 in series with an adjustable resistance 9. In the embodiment of the invention shown in FIG. 3, said means 7 are composed of a direct current source 10 whose voltage is adjustable.
  • the electrode 6 has, in general, the shape of a reservoir or expansion chamber and is arranged downstream and facing the expansion orifice 5 so as to receive the jet of plasma produced by the generator 1.
  • the reservoir formed by the electrode 6 is empty and, in another embodiment, said reservoir contains a gas or a vapor. This gas or this vapor can be such that, if it were in contact with the filament of the cathode 2, it would damage the latter.
  • the abovesaid value V is a critical value for the voltage between the anode 4 and the electrode 6; when this voltage exceeds this value V there is produced a sudden increase in intensity, respectively, of the ion current and, to a lesser degree of the electron current, at the level of the electrode 6.
  • the inventors have, in fact, noted that starting from a certain positive value V of the potential difference between the electrode 6 and the anode 4, there is produced a new ionisation or arc between the anode 4 and the electrode 6 manifested by the abovesaid sudden increases in intensity. This phenomenon is illustrated by FIG.
  • the duoplasmatron or generator 1 contained argon, and the electrode 6, in the shape of a reservoir, also contained argon.
  • the critical value V was found to be comprised, according to the conditions of the experiment, between 25 and 30 volts.
  • the generator 1 contained argon whilst the electrode 6, in the form of a reservoir, contained oxygen, it was then noted that the critical voltage was around 50 volts and that this voltage V diminished when the pressure of oxygen in the electrode 6 increased.
  • the critical voltage V depends, firstly, on the nature of the gases present in the generator 1 and, possibly in the electrode 6, secondly, on the conditions of discharge in the generator l and on the pressure of the gas which is possibly present, in the electrode 6. It was found that V had a value comprised between 5 and 100 volts.
  • the electrode 6 has substantially the shape of a cylinder of which the axis extends that of the duoplasmatron and provides an inlet aperture 13, facing the extraction orifree 5, and an outlet aperture 14 through which is injected the ion current and electrons formed inside this electrode 6.
  • the electrode 6 which forms, in this case, an expansion chamber, comprises, in addition, means 15 for enabling the introduction of a gas or of a vapour inside the said chamber, this gas or this vapour being intended to be ionised by the electrons and primary ions emerging from the duoplasmatron.
  • the means 15 are, for example, constituted by an outer reservoir (not shown) and an intake pipe.
  • this induction having preferably a direction substantially parallel to the axis of the cylinder formed by the electrode 6.
  • the inventors have, in fact, noted that the presence of a magnetic induction inside the expansion chamber increases the ionic and electronic intensities inside the latter as well as the yield of ionisation in this chamber.
  • An extraction electrode I8, known in itself, is arranged downstream of the electrode 6.
  • This electrode 18 enables, when it is suitably polarised, the extraction, from the expansion chamber formed by the electrode 6, of positive or negative ions which have arrived or been formed in said electrode 6.
  • the potential of this electrode 18 relative to the electrodes of the source has, in a general way, a very high value with respect to the relative potential of the electrodes of the source. If the potential of the electrode 18 is positive, it will be the negative ions and the electrons which will be extracted, whilst, if the potential of this electrode 18 is negative, it will be the positive ions which will be extracted through this electrode.
  • the electrode 6 also has the shape of an expansion chamber but it is formed in the shape of an oven provided with heating means 22 to vaporise a substance 19 which has been introduced into this oven.
  • the source comprises, in addition, downstream of the electrode 6, after its outlet aperture 14, magnetic separating means 20 adapted to separate the trajectory of primary ions from that of (positive or negative) ions produced in the expansion chamber.
  • magnetic separating means 20 adapted to separate the trajectory of primary ions from that of (positive or negative) ions produced in the expansion chamber.
  • an electrode 21 brought to a positive potential with respect to that of the electrode 6 and which is adapted to trap the electrons of the plasma beam emerging from the source.
  • the ion source according to the invention enables the obtaining of intense ion beams from various materials without there being any risk of contamination of the filament of the hot cathode by these materials.
  • the pressure inside the latter can be varied on condition, of course, that this pressure remains less than that which exists inside the primary generator 1.
  • the ion source which has just been described with respect to FIGS. 1 to 3 can lend itself to numerous applications and there may be mentioned, by way of example, application of ions for doping semi-conductor materials.
  • ions for doping semi-conductor materials.
  • positive ions acceptors:l3 (boron), P (phosphorus) and 0* (oxygen)
  • donors Fe (iron), Si (silicon) and O.
  • the ion source according to the invention can also be used for a mass spectrometer and a VAN-DE-GRAAFF type accelerator.
  • Ion source comprising a primary plasma generator constituted by a hot cathode and an anode, between which an arc is produced, said anode defining an extraction orifice, and by an intermediate electrode pinching the arc in proximity to said extraction orifice in the anode, magnetic field producing means creating a magnetic field between the intermediate electrode and the extraction orifice, an extraction electrode downstream of said anode, said extraction orifice of the anode having a relatively small cross-section so that the pressure of the gases occurring inside said primary plasma generator is independent of the pressure existing downstream of said extraction orifice, said pressure downstream of the extraction orifice being less than said pressure inside the primary plasma generator, said generator comprising a fifth electrode arranged downstream of the.
  • Ion source according to claim 2 wherein the fifth electrode is in the form of an enclosure including an inlet aperture, arranged adjacent the extraction orifice without intervening expansion space but leaving an insulation space, and an outlet aperture.
  • Ion source according to claim 4 comprising means for creating magnetic induction inside said enclosure.
  • Ion source according to claim 4 comprising means arranged downstream of said outlet aperture for separating secondary ions formed in said enclosure from the primary ions formed in said primary plasma generator.
  • Ion source comprising a primary plasma generator constituted by a hot cathode and an anode, between which an arc is produced, said anode defining an extraction orifice, and by an intermediate electrode pinching the arc in proximity to said extraction orifice in the anode, magnetic field producing means creating a magnetic field between the intermediate electrode and the extraction orifice, said extraction orifice having a relatively small cross-section so that the pressure of the gases occurring inside said primary plasma generator is independent of the pressure existing downstream of said extraction orifice, said pressure downstream of the extraction orifice being less than said pressure inside the primary plasma generator.
  • said generator comprising an additional electrode arranged downstream of said extraction orifice of the anode.
  • said additional electrode being in the form of an enclosure including an inlet aperture arranged adjacent the extraction orifice without an intervening expansion space but leaving an insulation space, and an outlet aperture, means for applying to said additional electrode a potential posi tive with respect to that of the anode and of adjustable value, and means for introducing a gas or a vapor into said enclosure.
  • Ion source comprising a primary plasma generator constituted by a hot cathode and an anode, between which an arc is produced, said anode defining an extraction orifice, and by an intermediate electrode pinching the arc in proximity to said extraction orifice in the anode, magnetic field producing means creating a magnetic field between the intermediate electrode and the extraction orifice, said extraction orifice having a relatively small cross-section so that the pressure of the gases occurring inside said primary plasma generator is independent of the pressure existing downstream of said extraction orifice, said pressure downstream of the extraction orifice being less than said pressure inside the primary plasma generator, said generator comprising an additional electrode arranged downstream of said extraction orifice of the anode, said additional electrode being in the form of an enclosure including an inlet aperture arranged adjacent the extraction orifice without an intervening expansion space but leaving an insulation space, and an outlet aperture, means for applying to said additional electrode a potential positive with respect to that of the anode and of adjustable value, and heating means for vaporizing a solid substance present inside said enclosure.
  • Ion source comprising a primary plasma generator constituted by a hot cathode and an anode, between which an arc is produced, said anode defining an extraction orifice, and by an intermediate electrode pinching the arc in proximity to said extraction orifice in the anode, magnetic field producing means creating a magnetic field between the intermediate electrode and the extraction orifice, said extraction orifice having a relatively small cross-section so that the pressure of the gases occurring inside said primary plasma generator is independent of the pressure existing downstream of said extraction orifice, said pressure downstream of the extraction orifice being less than said pressure inside the primary plasma generator, said generator comprising an additional electrode arranged downstream of said extraction orifice of the anode, said additional electrode being in the form of an enclosure including an inlet aperture arranged adjacent the extraction orifice without an intervening expansion space but leaving an insulation space, and an outlet aperture, means for applying to said additional electrode a potential positive with respect to that of the anode and of adjustable value, and means for creating magnetic induction inside said enclosure.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Electron Sources, Ion Sources (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
US296594A 1971-10-13 1972-10-11 Ion sources Expired - Lifetime US3890535A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7136701A FR2156978A5 (enrdf_load_stackoverflow) 1971-10-13 1971-10-13

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US3890535A true US3890535A (en) 1975-06-17

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US (1) US3890535A (enrdf_load_stackoverflow)
DE (1) DE2249999A1 (enrdf_load_stackoverflow)
FR (1) FR2156978A5 (enrdf_load_stackoverflow)
GB (1) GB1411428A (enrdf_load_stackoverflow)
NL (1) NL7213791A (enrdf_load_stackoverflow)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4045677A (en) * 1976-06-11 1977-08-30 Cornell Research Foundation, Inc. Intense ion beam generator
US4301391A (en) * 1979-04-26 1981-11-17 Hughes Aircraft Company Dual discharge plasma device
US4529571A (en) * 1982-10-27 1985-07-16 The United States Of America As Represented By The United States Department Of Energy Single-ring magnetic cusp low gas pressure ion source
US4560907A (en) * 1982-06-25 1985-12-24 Hitachi, Ltd. Ion source
US4587430A (en) * 1983-02-10 1986-05-06 Mission Research Corporation Ion implantation source and device
US4620095A (en) * 1984-01-18 1986-10-28 Miziolek Andrzej W Ion neutralization resonance emission elemental detector
AT381826B (de) * 1984-10-11 1986-12-10 Voest Alpine Ag Plasmabrenner
USRE34806E (en) * 1980-11-25 1994-12-13 Celestech, Inc. Magnetoplasmadynamic processor, applications thereof and methods
US5838012A (en) * 1997-03-19 1998-11-17 Genus, Inc. Charge exchange cell
US20100320395A1 (en) * 1999-12-13 2010-12-23 Semequip, Inc. External cathode ion source

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2550681B1 (fr) * 1983-08-12 1985-12-06 Centre Nat Rech Scient Source d'ions a au moins deux chambres d'ionisation, en particulier pour la formation de faisceaux d'ions chimiquement reactifs

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3238414A (en) * 1965-07-28 1966-03-01 George G Kelley High output duoplasmatron-type ion source
US3265918A (en) * 1961-12-11 1966-08-09 High Voltage Engineering Corp Ion source having plasma control means
US3631283A (en) * 1968-04-09 1971-12-28 Thomson Csf Device for producing high intensity ion beams

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3265918A (en) * 1961-12-11 1966-08-09 High Voltage Engineering Corp Ion source having plasma control means
US3238414A (en) * 1965-07-28 1966-03-01 George G Kelley High output duoplasmatron-type ion source
US3631283A (en) * 1968-04-09 1971-12-28 Thomson Csf Device for producing high intensity ion beams

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4045677A (en) * 1976-06-11 1977-08-30 Cornell Research Foundation, Inc. Intense ion beam generator
US4301391A (en) * 1979-04-26 1981-11-17 Hughes Aircraft Company Dual discharge plasma device
USRE34806E (en) * 1980-11-25 1994-12-13 Celestech, Inc. Magnetoplasmadynamic processor, applications thereof and methods
US4560907A (en) * 1982-06-25 1985-12-24 Hitachi, Ltd. Ion source
US4529571A (en) * 1982-10-27 1985-07-16 The United States Of America As Represented By The United States Department Of Energy Single-ring magnetic cusp low gas pressure ion source
US4587430A (en) * 1983-02-10 1986-05-06 Mission Research Corporation Ion implantation source and device
US4620095A (en) * 1984-01-18 1986-10-28 Miziolek Andrzej W Ion neutralization resonance emission elemental detector
AT381826B (de) * 1984-10-11 1986-12-10 Voest Alpine Ag Plasmabrenner
US5838012A (en) * 1997-03-19 1998-11-17 Genus, Inc. Charge exchange cell
US20100320395A1 (en) * 1999-12-13 2010-12-23 Semequip, Inc. External cathode ion source
US8502161B2 (en) * 1999-12-13 2013-08-06 Semequip, Inc. External cathode ion source

Also Published As

Publication number Publication date
GB1411428A (en) 1975-10-22
DE2249999A1 (de) 1973-04-19
FR2156978A5 (enrdf_load_stackoverflow) 1973-06-01
NL7213791A (enrdf_load_stackoverflow) 1973-04-17

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