EP0300566B1 - Liquid metal ions source with a vacuum arc - Google Patents

Liquid metal ions source with a vacuum arc Download PDF

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Publication number
EP0300566B1
EP0300566B1 EP88201511A EP88201511A EP0300566B1 EP 0300566 B1 EP0300566 B1 EP 0300566B1 EP 88201511 A EP88201511 A EP 88201511A EP 88201511 A EP88201511 A EP 88201511A EP 0300566 B1 EP0300566 B1 EP 0300566B1
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Prior art keywords
anode
metal
ion source
cathode
reservoir
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German (de)
French (fr)
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EP0300566A1 (en
Inventor
Henri Société Civile S.P.I.D. Bernardet
Jean-Claude Société Civile S.P.I.D. Pauwels
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Koninklijke Philips NV
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SODERN SA
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
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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
    • H01J27/20—Ion sources; Ion guns using particle beam bombardment, e.g. ionisers
    • H01J27/22—Metal ion sources
    • 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

Definitions

  • the invention relates to a vacuum arc ion source comprising a cathode, a control trigger, an anode and means for polarizing said cathode, control trigger and anode so that a first jet of plasma emanating from said cathode is formed in the anode-cathode space, the electrons of said plasma being attracted to the anode to heat the material until it vaporizes and to then ionize the vapor emitted in order to form a second jet of plasma emanating from the anode and directed to an extraction electrode.
  • Ion sources are used in many devices: implanters, accelerators, neutron tubes, mass spectrometers, etc.
  • vacuum arc sources offer the possibility of reducing the pumping means between the ion source and the acceleration zone and of having large extraction surfaces.
  • the anode is an electron collector while the cathode emits electrons and plasma (formed from the cathode material).
  • the reduction in the anode surface exposed to the electronic flux has the effect of causing an increase in the density of the electron bombardment and consequently of the energy deposited.
  • a threshold value a function of the anode and cathode materials, of the arc current and of the exposed anode surface, the appearance of light areas themselves emitting plasma from the anode material.
  • the properties of the emitted plasmas are close to those of the cathode spots (angle, density, speed), but the flow of matter emitted in the form of plasma can be controlled (geometric structure, arc current, temporal characteristics of the pulses) by l intermediary of the temperature of the anode which thus results from the energy brought by the electrons and from the energy dissipated, on the anode in particular, in the creation of the vapor emitted and then ionized.
  • the duration of use of a vacuum arc ion source is generally limited.
  • the present invention aims to create a plasma source for which this period of use is increased.
  • the vacuum arc ion source comprises means for providing a layer of metal to cover the anode surface, said means comprising a reservoir for metal and a wall permeable to metal. between the tank and the anode surface.
  • the metal is vaporized and ionized on the anode surface. To compensate for the losses of metal, this is transferred from the tank to the anode surface through the wall. The duration of use of the ion source is thereby increased.
  • the permeable wall is preferably made of a material which has a large difference in temperature with respect to the metal necessary for obtaining the same vapor pressure.
  • the plasma will then be composed exclusively of metal ions originating from the metal layer.
  • Said permeable wall is preferably arranged so as not to be blocked by the deposition of cathode material.
  • Said cathode material is preferably chosen so as not to disturb the wettability characteristics of the anode.
  • said metal is a liquid and said wall separating the reservoir from the anode surface is made of a material comprising numerous pores allowing the passage of liquid metal by capillary action such as for example a sintered tungsten or nickel.
  • said metal is a liquid and said tank-anodic surface separation wall is crossed by contiguous slots allowing the surface of the anode to be fed by surface diffusion.
  • An interesting solution for materials liquid at room temperature such as mercury is the use of an anode cooled at low temperature and capable of being supplied by the high vapor pressure (for example some 10 ⁇ 3 torrs) of this compound in the residual vacuum.
  • the material condenses on the anode and is thus vaporized and ionized, as for metals in the liquid phase, by the electrons of the arc.
  • Another solution making it possible to increase the duration of use of the ion sources is the use of cathode material much less refractory than the anode but compatible with the wettability properties necessary: to unclog the pores or the orifices of arrival liquid metal (or liquefied), the ion source is operated without liquid metal, at higher energies allowing the creation of anode spots on the cathode material deposited on the anode. The energy must however remain below the threshold leading to anode spots on solid anode material. This mode (called conditioning) is preparatory to the proper functioning of the ion source.
  • FIG. 1a represents the block diagram of a source of liquid metal ions with a vacuum arc of the biplanar type according to the invention.
  • Figure 1b shows sections of porous anode and anode with slots.
  • FIG. 5 represents the block diagram of a source of liquid metal ions with a vacuum arc of the coplanar type according to the invention.
  • FIG. 1a a section along a vertical plane shows a metal cathode 1 in the form of a circular crown, the face opposite the opening 2 is protected by an insulating screen 3.
  • the anode 4 disposed opposite the opening 2 along the axis of the crown and held by an insulating disc 5 forming a screen, according to the invention comprises a reservoir 6 containing the liquid metal 7.
  • the lower part of this reservoir has a narrowed shape so as to present a surface area 8 of small dimensions constituting the anode proper separated from the liquid area of the reservoir by a wall 9.
  • auxiliary electrodes 10 and 11 in the form of a crown for example and separated by a groove 12 of the order of 0.1 mm and constituting the control trigger.
  • This auxiliary discharge is essential for the correct functioning of the source; it could be of another definition and for example obtained by an anodic trigger very close to the cathode of the source.
  • cathode 3 and anode 5 screens serve as a support for crown 1 and reservoir 6 respectively and to form a screen for microparticles possibly released by the anode in the volume where ionization occurs and occult the cathode and the trigger which emit parasitic ions.
  • the wall 9 separating the liquid metal 7 from the anode surface 8 is made of a material comprising numerous pores 13, as shown in FIG. 1b, showing a section with enlarged area of this wall in a horizontal plane. This gives the passage by capillarity from the reservoir part to the anode surface.
  • the mode of supply of this anode surface can also be achieved by means of contiguous slots 14 passing through the wall 9 as shown in FIG. 1b also showing a section with enlarged area of this wall in a horizontal plane.
  • the anodic surface is thus covered by surface diffusion and the anodic material chosen is then a function of its characteristics of wettability by the liquid metal.
  • the wall 9 is constituted for example by a porous sintered system such as tungsten. This frit is surrounded by the liquid metal which has diffused by capillary action towards the surface area 8 of the anode opposite the opening 2.
  • the plasma jets 15 and 16 emitted respectively by the trigger and the cathode produce between the cathode and the anode a flow of electrons 17 which comes to controllably heat the part of the anode constituted by the sintered element in intimate contact with the diffused metal element.
  • the metal element is gallium, it has a vapor pressure of 1 mm of mercury at a temperature of 300 ° C, while the tungsten used as a support material has the same vapor pressure at 4500 ° C .
  • the metal element alone will be vaporized to form, after ionization, a plasma jet 18 directed perpendicular to the anode surface and composed exclusively of metal ions.
  • the pressure of the liquid metal in the tank can be fixed by a piston 19 and spring 20 system.
  • the tank is provided with a drain 21 which can be replaced by a tap.
  • a heating system can be arranged to liquefy non-liquid metals at room temperature.
  • FIG. 2a shows a structure in which a plurality of sources identical to the basic model described above is used.
  • the upper part and the lower part are respectively a vertical section along the plane passing through AA ′ and a horizontal section along the plane passing through BB ′ on which we have identified the cathodes 1 with their screens 3, the triggers 10, the anode surfaces 8 and the anode supports 5, the liquid metal 7 and the porous anode parts 9.
  • FIG. 2b represents a structure with anode in the shape of a thin crown.
  • a multicore of concentric anodes 22 can thus be arranged as indicated on the horizontal section along the plane passing through BB ′.
  • the cathode 24 and its screen 23 as well as the trigger 25 are also in the form of a crown.
  • the vertical section along the plane passing through AA ′ does not differ from that shown in Figure 2a.
  • the anodes 26 are in the form of flat parallelepipeds arranged at 90 °; they are separated by the screens 27.
  • the cathodes 28 and their insulating screen 29, the triggers 30 are arranged along the generatrices of a cylinder as indicated on the sections vertical along the plane passing through AA ′ and horizontal along the plane passing through BB ′.
  • FIG. 4 shows a structure with several superimposed anodes, each of them 31 having the shape of a flat cylinder.
  • the cathodes 32 and their screens 33 as well as the triggers 34 are arranged in crowns also superimposed.
  • a vertical central column 35 common to anodic multicylinders, allows their supply of liquid metal, as indicated on the vertical sections along the plane AA ′ and horizontal along the plane BB ′.
  • the structures presented in the previous figures are of the biplanar type, that is to say that the anode and the cathode are in different planes and that the cathode and anode plasmas are projected in opposite directions.
  • An example of another so-called coplanar version is shown in Figure 5; as for the biplanar version, the cathode can have the shape of a circular crown 36 whose small anode 4 is located on the axis.
  • An insulating material 37 separates the two electrodes and insulates them to voltages which can vary from a few kilovolts to about twenty kilovolts.
  • the insulator also has the function of moving the emission of the cathode spots away from the axis so as to facilitate their interception by a screen 38 pierced in its center with an orifice allowing essentially and only the plasma 18 emitted by the spot anodic.
  • the trigger 10, 11 required for the control can be circular and of the same structure as in the biplanar source.
  • the biplanar structure has the advantage of being easier to initiate (lower anode-cathode voltage and lower trigger control current) due to the shorter and more direct path of the electrons.
  • the invention also covers all the versions of cathode electrode shape intermediate between the so-called biplanar and coplanar structures as shown in the diagrams in FIG. 6, representing a structure with a semi-cylindrical cathode 39 and in FIGS. 7a and 7b representing structures with frustoconical cathodes 40 and 41.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Electron Sources, Ion Sources (AREA)

Description

L'invention concerne une source d'ions à arc sous vide comportant une cathode, une gachette de commande, une anode et des moyens de polarisation desdites cathode, gachette de commande et anode de telle façon qu'un premier jet de plasma émanant de ladite cathode soit formé dans l'espace anode-cathode, les électrons dudit plasma étant attirés sur l'anode pour en échauffer le matériau jusqu'à sa vaporisation et pour ioniser ensuite la vapeur émise afin de former un second jet de plasma émanant de l'anode et dirigés vers une électrode d'extraction.The invention relates to a vacuum arc ion source comprising a cathode, a control trigger, an anode and means for polarizing said cathode, control trigger and anode so that a first jet of plasma emanating from said cathode is formed in the anode-cathode space, the electrons of said plasma being attracted to the anode to heat the material until it vaporizes and to then ionize the vapor emitted in order to form a second jet of plasma emanating from the anode and directed to an extraction electrode.

Les sources d'ions sont utilisées dans de nombreux dispositifs : implantateurs, accélérateurs, tubes à neutrons, spectromètres de masse, etc.Ion sources are used in many devices: implanters, accelerators, neutron tubes, mass spectrometers, etc.

Par rapport aux sources d'ions à décharge dans les gaz, les sources à arc sous vide offrent la possibilité de réduire les moyens de pompage entre la source d'ions et la zone d'accélération et de disposer de grandes surfaces d'extraction.Compared to ion discharge sources in gases, vacuum arc sources offer the possibility of reducing the pumping means between the ion source and the acceleration zone and of having large extraction surfaces.

Dans un arc de configuration classique l'anode est un collecteur d'électrons tandis que la cathode est émetteur d'électrons et de plasma (formé à partir du matériau cathodique).In an arc of conventional configuration, the anode is an electron collector while the cathode emits electrons and plasma (formed from the cathode material).

La réduction de la surface anodique exposée au flux électronique a pour effet d'entraîner une augmentation de la densité du bombardement électronique et par conséquent de l'énergie déposée.The reduction in the anode surface exposed to the electronic flux has the effect of causing an increase in the density of the electron bombardment and consequently of the energy deposited.

Il en résulte pour une valeur seuil, fonction des matériaux anodique et cathodique, du courant d'arc et de la surface anodique exposée, l'apparition de zones lumineuses elles-mêmes émettrices de plasma à partir du matériau anodique. Les propriétés des plasmas émis sont proches de celles des spots cathodiques (angle, densité, vitesse), mais le flux de matière émis sous forme de plasma peut être contrôlé (structure géométrique, courant de l'arc, caractéristiques temporelles des impulsions) par l'intermédiaire de la température de l'anode qui résulte ainsi de l'énergie apportée par les électrons et de l'énergie dissipée, sur l'anode en particulier, dans la création de la vapeur émise et ensuite ionisée.This results in a threshold value, a function of the anode and cathode materials, of the arc current and of the exposed anode surface, the appearance of light areas themselves emitting plasma from the anode material. The properties of the emitted plasmas are close to those of the cathode spots (angle, density, speed), but the flow of matter emitted in the form of plasma can be controlled (geometric structure, arc current, temporal characteristics of the pulses) by l intermediary of the temperature of the anode which thus results from the energy brought by the electrons and from the energy dissipated, on the anode in particular, in the creation of the vapor emitted and then ionized.

La durée d'utilisation d'une source d'ions à arc sous vide est généralement limitée. En utilisant le principe de création de spot anodique, la présente invention vise à créer une source de plasma pour laquelle cette durée d'utilisation est accrue.The duration of use of a vacuum arc ion source is generally limited. Using the principle of creating an anode spot, the present invention aims to create a plasma source for which this period of use is increased.

L'article "Metal vapor vacuum arc ion source", de i.G. Brown et al., dans Rev. Sci. Instrum., vol. 57, No6, Juin 1986, p.1069-1084, décrit une source d'ions à arc sous vide et fait référence en page 1070 au principe de création de spot anodique.The article "Metal vapor vacuum arc ion source", by iG Brown et al., In Rev. Sci. Instrum., Vol. 57, No. 6, June 1986, p.1069-1084, discloses an ion source vacuum arc and refers on page 1070 to the principle of creation of anode spot.

A cet effet et conformément à l'invention, la source d'ions à arc sous vide comporte des moyens de fournir une couche d'un métal pour recouvrir la surface anodique, lesdits moyens comprenant un réservoir pour le métal et une paroi perméable au métal entre le réservoir et la surface anodique.For this purpose and in accordance with the invention, the vacuum arc ion source comprises means for providing a layer of metal to cover the anode surface, said means comprising a reservoir for metal and a wall permeable to metal. between the tank and the anode surface.

En cours d'utilisation, le métal est vaporisé et ionisé sur la surface anodique. Pour compenser les pertes de métal, celui-ci est transféré du réservoir à la surface anodique à travers la paroi. La durée d'utilisation de la source d'ions est de ce fait augmentée.In use, the metal is vaporized and ionized on the anode surface. To compensate for the losses of metal, this is transferred from the tank to the anode surface through the wall. The duration of use of the ion source is thereby increased.

La paroi perméable est réalisée de préférence dans un matériau qui présente par rapport au métal une grande différence de températures nécessaires à l'obtention d'une même tension de vapeur.The permeable wall is preferably made of a material which has a large difference in temperature with respect to the metal necessary for obtaining the same vapor pressure.

Le plasma sera alors composé exclusivement d'ions métal provenant de la couche métallique.The plasma will then be composed exclusively of metal ions originating from the metal layer.

Ladite paroi perméable est de préférence disposée de façon à ne pas être obturée par le dépôt de matériau cathodique.Said permeable wall is preferably arranged so as not to be blocked by the deposition of cathode material.

Ledit matériau cathodique est de préférence choisi de façon à ne pas perturber les caractéristiques de mouillabilité de l'anode.Said cathode material is preferably chosen so as not to disturb the wettability characteristics of the anode.

Dans une première variante, ledit métal est un liquide et ladite paroi séparant le réservoir de la surface anodique est constituée d'un matériau comportant de nombreux pores permettant le passage du métal liquide par capillarité tel que par exemple un fritté en tungstène ou de nickel.In a first variant, said metal is a liquid and said wall separating the reservoir from the anode surface is made of a material comprising numerous pores allowing the passage of liquid metal by capillary action such as for example a sintered tungsten or nickel.

Dans une seconde variante, ledit métal est un liquide et ladite paroi de séparation réservoir-surface anodique est traversée par des fentes contiguës permettant l'alimentation de la surface de l'anode par diffusion superficielle.In a second variant, said metal is a liquid and said tank-anodic surface separation wall is crossed by contiguous slots allowing the surface of the anode to be fed by surface diffusion.

Deux groupes de métaux liquides sont utilisables :

  • les métaux liquides à température ambiante et à faible tension de vapeur (gallium, caesium, alliage gallium-indium...)
  • les métaux liquéfiés par chauffage du réservoir et à faible tension de vapeur (étain, indium, bismuth, plomb...).
Two groups of liquid metals can be used:
  • liquid metals at room temperature and at low vapor pressure (gallium, caesium, gallium-indium alloy ...)
  • metals liquefied by heating the tank and at low vapor pressure (tin, indium, bismuth, lead ...).

Une solution intéressante pour les matériaux liquides à température ambiante tel que le mercure est l'emploi d'une anode refroidie à basse température et susceptible d'être alimentée par la tension de vapeur importante (par exemple quelques 10⁻³ torrs) de ce composé dans le vide résiduel. Le matériau se condense sur l'anode et est ainsi vaporisé et ionisé, comme pour les métaux en phase liquide, par les électrons de l'arc.An interesting solution for materials liquid at room temperature such as mercury is the use of an anode cooled at low temperature and capable of being supplied by the high vapor pressure (for example some 10⁻³ torrs) of this compound in the residual vacuum. The material condenses on the anode and is thus vaporized and ionized, as for metals in the liquid phase, by the electrons of the arc.

Une autre solution permettant d'augmenter la durée d'utilisation des sources d'ions est l'utilisation de matériau cathodique beaucoup moins réfractaire que l'anode mais compatible avec les propriétés de mouillabilité nécessaires : pour désobturer les pores ou les orifices d'arrivée du métal liquide (ou liquéfié), on fait fonctionner la source d'ions sans métal liquide, à des énergies plus élevées permettant la création de spots anodiques sur le matériau cathodique déposé sur l'anode. L'énergie doit par contre rester inférieure au seuil conduisant à des spots anodiques sur matériau anodique massif. Ce mode (dit de conditionnement) est préparatoire au bon fonctionnement de la source d'ions.Another solution making it possible to increase the duration of use of the ion sources is the use of cathode material much less refractory than the anode but compatible with the wettability properties necessary: to unclog the pores or the orifices of arrival liquid metal (or liquefied), the ion source is operated without liquid metal, at higher energies allowing the creation of anode spots on the cathode material deposited on the anode. The energy must however remain below the threshold leading to anode spots on solid anode material. This mode (called conditioning) is preparatory to the proper functioning of the ion source.

La description suivante en regard des dessins annexés, le tout donné à titre d'exemple, fera bien comprendre comment l'invention peut être réalisée.The following description with reference to the accompanying drawings, all given by way of example, will make it clear how the invention can be implemented.

La figure 1a représente le schéma de principe d'une source d'ions de métaux liquides à arc sous vide de type biplanaire conforme à l'invention.FIG. 1a represents the block diagram of a source of liquid metal ions with a vacuum arc of the biplanar type according to the invention.

La figure 1b représente des coupes d'anode poreuse et d'anode avec fentes.Figure 1b shows sections of porous anode and anode with slots.

A partir du schéma de principe de la figure 1a, on peut concevoir diverses structures de sources de plasma :

  • Figure 2a : une structure "multipoints" constituée de nombreux éléments identiques.
  • Figure 2b : une structure "en couronne" avec anode en forme de couronne et son système multispots cathodiques.
  • Figure 3 : une structure "cylindrique" avec les cathodes disposées suivant les génératrices d'un cylindre.
  • Figure 4 : une structure "multi-annulaire" à anodes sous forme de cylindres plats et cathodes disposées en couronne. Cette structure est constituée par la mise en parallèle d'éléments identiques.
From the block diagram of FIG. 1a, it is possible to design various structures of plasma sources:
  • Figure 2a: a "multipoint" structure made up of many identical elements.
  • Figure 2b: a "crown" structure with anode in the form of a crown and its cathode multispot system.
  • Figure 3: a "cylindrical" structure with the cathodes arranged along the generatrices of a cylinder.
  • Figure 4: a "multi-annular" structure with anodes in the form of flat cylinders and cathodes arranged in a crown. This structure is made up of parallel elements that are identical.

La figure 5 représente le schéma de principe d'une source d'ions de métaux liquides à arc sous vide de type coplanaire conforme à l'invention.FIG. 5 represents the block diagram of a source of liquid metal ions with a vacuum arc of the coplanar type according to the invention.

On peut également concevoir les structures de sources suivantes intermédiaires entre la structure de type biplanaire et la structure de type coplanaire :

  • Figure 6 : une structure à cathode cylindrique.
  • Figures 7a et 7b : des structures à cathode tronconique.
One can also conceive the following source structures intermediate between the biplanar type structure and the coplanar type structure:
  • Figure 6: a cylindrical cathode structure.
  • Figures 7a and 7b: frustoconical cathode structures.

Les éléments correspondants sur ces différentes figures seront indiqués par le même chiffre de référence.The corresponding elements in these different figures will be indicated by the same reference number.

Sur la figure 1a, une coupe suivant un plan vertical fait apparaître une cathode en métal 1 en forme de couronne circulaire dont la face en regard de l'ouverture 2 est protégée par un écran isolant 3.In FIG. 1a, a section along a vertical plane shows a metal cathode 1 in the form of a circular crown, the face opposite the opening 2 is protected by an insulating screen 3.

L'anode 4 disposée en face de l'ouverture 2 suivant l'axe de la couronne et maintenue par un disque isolant 5 formant écran, comporte selon l'invention un réservoir 6 contenant le métal liquide 7. La partie inférieure de ce réservoir a une forme rétrécie de manière à présenter une zone superficielle 8 de petites dimensions constituant l'anode proprement dite séparée de la zone liquide du réservoir par une paroi 9.The anode 4 disposed opposite the opening 2 along the axis of the crown and held by an insulating disc 5 forming a screen, according to the invention comprises a reservoir 6 containing the liquid metal 7. The lower part of this reservoir has a narrowed shape so as to present a surface area 8 of small dimensions constituting the anode proper separated from the liquid area of the reservoir by a wall 9.

Pour favoriser l'amorçage d'un arc entre la cathode et l'anode, on peut utiliser une décharge produite entre deux électrodes auxiliaires 10 et 11 en forme de couronne par exemple et séparées par un sillon 12 de l'ordre de 0,1 mm et constituant la gachette de commande. Cette décharge auxiliaire est indispensable au fonctionnement correct de la source ; elle pourraît être d'une autre définition et par exemple obtenue par une gachette anodique très proche de la cathode de la source.To favor the initiation of an arc between the cathode and the anode, it is possible to use a discharge produced between two auxiliary electrodes 10 and 11 in the form of a crown for example and separated by a groove 12 of the order of 0.1 mm and constituting the control trigger. This auxiliary discharge is essential for the correct functioning of the source; it could be of another definition and for example obtained by an anodic trigger very close to the cathode of the source.

Le rôle des écrans de cathode 3 et d'anode 5 est de servir de support respectivement à la couronne 1 et au réservoir 6 et de former écran aux microparticules éventuellement libérées par l'anode dans le volume où se produit l'ionisation et d'occulter la cathode et la gâchette qui émettent des ions parasites.The role of cathode 3 and anode 5 screens is to serve as a support for crown 1 and reservoir 6 respectively and to form a screen for microparticles possibly released by the anode in the volume where ionization occurs and occult the cathode and the trigger which emit parasitic ions.

La paroi 9 séparant le métal liquide 7 de la surface anodique 8 est constituée d'un matériau comportant de nombreux pores 13, tels que représentés sur la figure 1b, montrant une coupe avec zone agrandie de cette paroi suivant un plan horizontal. On obtient ainsi le passage par capillarité de la partie réservoir à la surface anodique.The wall 9 separating the liquid metal 7 from the anode surface 8 is made of a material comprising numerous pores 13, as shown in FIG. 1b, showing a section with enlarged area of this wall in a horizontal plane. This gives the passage by capillarity from the reservoir part to the anode surface.

Le mode d'alimentation de cette surface anodique peut également être réalisé au moyen de fentes contiguës 14 traversant la paroi 9 telles que représentées sur la figure 1b montrant également une coupe avec zone agrandie de cette paroi suivant un plan horizontal. La surface anodique est ainsi recouverte par diffusion superficielle et le matériau anodique choisi est alors fonction de ses caractéristiques de mouillabilité par le métal liquide.The mode of supply of this anode surface can also be achieved by means of contiguous slots 14 passing through the wall 9 as shown in FIG. 1b also showing a section with enlarged area of this wall in a horizontal plane. The anodic surface is thus covered by surface diffusion and the anodic material chosen is then a function of its characteristics of wettability by the liquid metal.

Selon l'invention, la paroi 9 est constituée par exemple par un système à fritté poreux tel que le tungstène. Ce fritté est entouré par le métal liquide qui a diffusé par capillarité vers la zone superficielle 8 de l'anode en regard de l'ouverture 2.According to the invention, the wall 9 is constituted for example by a porous sintered system such as tungsten. This frit is surrounded by the liquid metal which has diffused by capillary action towards the surface area 8 of the anode opposite the opening 2.

Les jets de plasma 15 et 16 émis respectivement par la gachette et la cathode produisent entre cathode et anode un flux d'électrons 17 qui vient échauffer de façon contrôlable la partie de l'anode constituée par l'élément fritté en contact intime avec l'élément métal diffusé.The plasma jets 15 and 16 emitted respectively by the trigger and the cathode produce between the cathode and the anode a flow of electrons 17 which comes to controllably heat the part of the anode constituted by the sintered element in intimate contact with the diffused metal element.

Si par exemple l'élément métal est du gallium, celui-ci présente une tension de vapeur de 1 mm de mercure à la température de 300°C, alors que le tungstène servant de matériau support présente la même tension de vapeur à 4500°C.If, for example, the metal element is gallium, it has a vapor pressure of 1 mm of mercury at a temperature of 300 ° C, while the tungsten used as a support material has the same vapor pressure at 4500 ° C .

Si donc la température de l'anode est bien contrôlée, l'élément métal sera seul vaporisé pour former après ionisation un jet de plasma 18 dirigé perpendiculairement à la surface anodique et composé exclusivement d'ions métal.If therefore the temperature of the anode is well controlled, the metal element alone will be vaporized to form, after ionization, a plasma jet 18 directed perpendicular to the anode surface and composed exclusively of metal ions.

La pression du métal liquide dans le réservoir peut être fixée par un système à piston 19 et à ressort 20. Le réservoir est muni d'un queusot de vidange 21 auquel on peut substituer un robinet.The pressure of the liquid metal in the tank can be fixed by a piston 19 and spring 20 system. The tank is provided with a drain 21 which can be replaced by a tap.

Un système de chauffage non représenté peut être disposé pour liquéfier les métaux non liquides à la température ambiante.A heating system, not shown, can be arranged to liquefy non-liquid metals at room temperature.

Diverses structures de sources de plasma peuvent être utilisées.Various plasma source structures can be used.

La figure 2a montre une structure dans laquelle on utilise une pluralité de sources identiques au modèle de base décrit ci-dessus. La partie supérieure et la partie inférieure sont respectivement une coupe verticale suivant le plan passant par AA′ et une coupe horizontale suivant le plan passant par BB′ sur lesquelles on a repéré les cathodes 1 avec leurs écrans 3, les gachettes 10, les surfaces anodiques 8 et les supports d'anode 5, le métal liquide 7 et les parties poreuses d'anode 9.FIG. 2a shows a structure in which a plurality of sources identical to the basic model described above is used. The upper part and the lower part are respectively a vertical section along the plane passing through AA ′ and a horizontal section along the plane passing through BB ′ on which we have identified the cathodes 1 with their screens 3, the triggers 10, the anode surfaces 8 and the anode supports 5, the liquid metal 7 and the porous anode parts 9.

La figure 2b représente une structure avec anode en forme de couronne de faible épaisseur. Une multicouronne d'anodes concentriques 22 peut ainsi être disposée comme indiqué sur la coupe horizontale suivant le plan passant par BB′. Entourant chaque anode, la cathode 24 et son écran 23 ainsi que la gachette 25 sont également en forme de couronne. La coupe verticale suivant le plan passant par AA′ ne diffère pas de celle représentée sur la figure 2a.FIG. 2b represents a structure with anode in the shape of a thin crown. A multicore of concentric anodes 22 can thus be arranged as indicated on the horizontal section along the plane passing through BB ′. Surrounding each anode, the cathode 24 and its screen 23 as well as the trigger 25 are also in the form of a crown. The vertical section along the plane passing through AA ′ does not differ from that shown in Figure 2a.

Sur la structure de la figure 3, les anodes 26 sont en forme de parallélépipèdes plats disposés à 90° ; elles sont séparées par les écrans 27. Les cathodes 28 et leur écran isolant 29, les gachettes 30 sont disposés suivant les génératrices d'un cylindre comme indiqué sur les coupes verticale suivant le plan passant par AA′ et horizontale suivant le plan passant par BB′.In the structure of FIG. 3, the anodes 26 are in the form of flat parallelepipeds arranged at 90 °; they are separated by the screens 27. The cathodes 28 and their insulating screen 29, the triggers 30 are arranged along the generatrices of a cylinder as indicated on the sections vertical along the plane passing through AA ′ and horizontal along the plane passing through BB ′.

La figure 4 montre une structure à plusieurs anodes superposées, chacune d'elles 31 ayant la forme d'un cylindre plat. Les cathodes 32 et leurs écrans 33 ainsi que les gachettes 34 sont disposés en couronnes également superposées. Une colonne centrale verticale 35 commune aux multicylindres anodiques, permet leur alimentation en métal liquide, comme indiqué sur les coupes verticale suivant le plan AA′ et horizontale suivant le plan BB′.FIG. 4 shows a structure with several superimposed anodes, each of them 31 having the shape of a flat cylinder. The cathodes 32 and their screens 33 as well as the triggers 34 are arranged in crowns also superimposed. A vertical central column 35 common to anodic multicylinders, allows their supply of liquid metal, as indicated on the vertical sections along the plane AA ′ and horizontal along the plane BB ′.

Les structures présentées sur les figures précédentes sont de type biplanaire, c'est-à-dire que l'anode et la cathode sont dans des plans différents et que les plasmas cathodiques et anodiques sont projetés dans des directions opposées. Un exemple d'une autre version dite coplanaire est présentée sur la figure 5 ; comme pour la version biplanaire, la cathode peut avoir la forme d'une couronne circulaire 36 dont l'anode 4 de petite dimension, serait située sur l'axe. Un matériau isolant 37 sépare les deux électrodes et les isole jusqu'à des tensions susceptibles de varier de quelques kilovolts à une vingtaine de kilovolts.The structures presented in the previous figures are of the biplanar type, that is to say that the anode and the cathode are in different planes and that the cathode and anode plasmas are projected in opposite directions. An example of another so-called coplanar version is shown in Figure 5; as for the biplanar version, the cathode can have the shape of a circular crown 36 whose small anode 4 is located on the axis. An insulating material 37 separates the two electrodes and insulates them to voltages which can vary from a few kilovolts to about twenty kilovolts.

L'isolant a pour office également d'éloigner l'émission des spots cathodiques de l'axe de façon à faciliter leur interception par un écran 38 percé en son centre d'un orifice laissant passer essentiellement et uniquement le plasma 18 émis par le spot anodique.The insulator also has the function of moving the emission of the cathode spots away from the axis so as to facilitate their interception by a screen 38 pierced in its center with an orifice allowing essentially and only the plasma 18 emitted by the spot anodic.

La gachette 10, 11 nécessaire à la commande peut être circulaire et de même structure que dans la source biplanaire.The trigger 10, 11 required for the control can be circular and of the same structure as in the biplanar source.

Sous l'aspect fonctionnel, la structure biplanaire présente l'avantage d'être plus facile à initier (tension anode-cathode et courant de commande de gachette plus faibles) en raison du trajet plus court et plus direct des électrons.From a functional point of view, the biplanar structure has the advantage of being easier to initiate (lower anode-cathode voltage and lower trigger control current) due to the shorter and more direct path of the electrons.

L'invention couvre également toutes les versions de forme d'électrode cathodique intermédiaire entre les structures dites biplanaires et coplanaires comme le montrent les schémas de la figure 6, représentant une structure à cathode semi-cylindrique 39 et des figures 7a et 7b représentant des structures à cathodes tronconiques 40 et 41.The invention also covers all the versions of cathode electrode shape intermediate between the so-called biplanar and coplanar structures as shown in the diagrams in FIG. 6, representing a structure with a semi-cylindrical cathode 39 and in FIGS. 7a and 7b representing structures with frustoconical cathodes 40 and 41.

Claims (11)

  1. A vacuum arc ion source comprising a cathode (1), a control gate (10, 11) and an anode (4) and means for polarizing said cathode (1), control gate (10, 11) and anode (4) in such a manner that a first jet of plasma emanating from said cathode is formed in the space between anode and cathode, the electrons of said plasma being attracted by the anode to heat the material until its vaporization and to subsequently ionize the vapour emitted to form a second jet of plasma emanating from the anode and directed towards an extraction electrode, characterized in that the vacuum arc ion source comprises means for providing a metal layer for covering the anode surface (8), said means comprising a reservoir (6) for the metal and a metal-permeable partition (9) between the reservoir (6) and the anode surface (8).
  2. An ion source as claimed in Claim 1, characterized in that the permeable partition (9) is formed from a material having with respect to the metal a great difference of the temperatures required to obtain the same vapour tension.
  3. An ion source as claimed in Claim 1 or 2, characterized in that the permeable partition (9) is disposed in such a way that it is not obturated by the deposition of cathode material.
  4. An ion source as claimed in any one of the Claims 1, 2 or 3, characterized in that the cathode material is chosen to be such that it does not disturb the wettability properties.
  5. An ion source as claimed in any one of the preceding Claims, characterized in that said metal is liquid and said permeable partition separating the reservoir (6) from the anode surface (8) is constituted by a material comprising a large number of pores.
  6. An ion source as claimed in Claim 5, characterized in that the partition (9) is a frit of tungsten or nickel.
  7. An ion source as claimed in any one of the Claims 1, 2 or 4, characterized in that said metal is liquid and said partition (9) separating the reservoir (6) from the anode surface (8) is traversed by contiguous slots (14) permitting of feeding the anode surface by superficial diffusion.
  8. An ion source as claimed in any one of the Claims 5, 6 or 7, characterized in that the metal is a liquid metal at the ambient temperature and having a low vapour tension.
  9. An ion source as claimed in Claim 8, characterized in that the metal is an element from the group comprising gallium, caesium and mercury.
  10. An ion source as claimed in any one of the Claims 5, 6 or 7, characterized in that the reservoir (6) is provided with heating means and the metal is liquefiable by heating the reservoir, said metal having a low vapour tension.
  11. An ion source as claimed in Claim 10, characterized in that the metal is an element from the group comprising tin, indium, bismuth and lead.
EP88201511A 1987-07-22 1988-07-14 Liquid metal ions source with a vacuum arc Expired - Lifetime EP0300566B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8710391 1987-07-22
FR8710391A FR2618604B1 (en) 1987-07-22 1987-07-22 LIQUID METAL ION SOURCE WITH VACUUM ARC

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EP0300566A1 EP0300566A1 (en) 1989-01-25
EP0300566B1 true EP0300566B1 (en) 1993-02-10

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EP (1) EP0300566B1 (en)
JP (1) JPH01157046A (en)
DE (1) DE3878331T2 (en)
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EP0399374B1 (en) * 1989-05-26 1995-04-19 Micrion Corporation Ion source method and apparatus
US5089707A (en) * 1990-11-14 1992-02-18 Ism Technologies, Inc. Ion beam generating apparatus with electronic switching between multiple cathodes
JP3060876B2 (en) * 1995-02-15 2000-07-10 日新電機株式会社 Metal ion implanter
US7058024B1 (en) 1999-02-03 2006-06-06 Lucent Technologies, Inc. Automatic telecommunications link identification system
US7276847B2 (en) * 2000-05-17 2007-10-02 Varian Semiconductor Equipment Associates, Inc. Cathode assembly for indirectly heated cathode ion source
AT500917B8 (en) * 2004-07-20 2007-02-15 Arc Seibersdorf Res Gmbh LIQUID METAL ION SOURCE
JP4988327B2 (en) * 2006-02-23 2012-08-01 ルネサスエレクトロニクス株式会社 Ion implanter
KR20080112790A (en) * 2007-06-22 2008-12-26 삼성전자주식회사 Method for forming film of semicondoctor device
DE102007058504A1 (en) 2007-12-05 2009-07-09 Acino Ag Transdermal therapeutic system containing a modulator of nicotinic acetylcholine receptors (nAChR)
BR112015023115A2 (en) * 2013-03-15 2017-07-18 Gen Electric cold cathode switch device and power converter
CN104217911A (en) * 2013-10-18 2014-12-17 常州博锐恒电子科技有限公司 Side-outgoing MEVVA (metal vapor vacuum arc) ion source
JP6927493B2 (en) * 2016-10-11 2021-09-01 国立大学法人横浜国立大学 Ion source
US11728140B1 (en) * 2022-01-31 2023-08-15 Axcelis Technologies, Inc. Hydraulic feed system for an ion source

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JPS57205953A (en) * 1981-06-12 1982-12-17 Jeol Ltd Ion source
JPS58163135A (en) * 1982-03-20 1983-09-27 Nippon Denshi Zairyo Kk Ion source
JPS61142645A (en) * 1984-12-17 1986-06-30 Hitachi Ltd Ion source for combined use by positive and negative polarity
US4638210A (en) * 1985-04-05 1987-01-20 Hughes Aircraft Company Liquid metal ion source
JPS62259332A (en) * 1985-10-23 1987-11-11 Nippon Denshi Zairyo Kk Ion generating device

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EP0300566A1 (en) 1989-01-25
DE3878331D1 (en) 1993-03-25
DE3878331T2 (en) 1993-08-05
JPH01157046A (en) 1989-06-20
FR2618604A1 (en) 1989-01-27
US5008585A (en) 1991-04-16
FR2618604B1 (en) 1989-11-24

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