EP0532411B1 - Elektronzyklotronresonanz-Ionenquelle mit koaxialer Zuführung elektromagnetischer Wellen - Google Patents

Elektronzyklotronresonanz-Ionenquelle mit koaxialer Zuführung elektromagnetischer Wellen Download PDF

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Publication number
EP0532411B1
EP0532411B1 EP92402460A EP92402460A EP0532411B1 EP 0532411 B1 EP0532411 B1 EP 0532411B1 EP 92402460 A EP92402460 A EP 92402460A EP 92402460 A EP92402460 A EP 92402460A EP 0532411 B1 EP0532411 B1 EP 0532411B1
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EP
European Patent Office
Prior art keywords
enclosure
tube
ion source
cavity
source according
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Expired - Lifetime
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EP92402460A
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English (en)
French (fr)
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EP0532411A1 (de
Inventor
Bernard Jacquot
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
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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
    • H01J27/16—Ion sources; Ion guns using high-frequency excitation, e.g. microwave excitation
    • H01J27/18—Ion sources; Ion guns using high-frequency excitation, e.g. microwave excitation with an applied axial magnetic field

Definitions

  • the present invention relates to an improvement of an ion source with electronic cyclotron resonance (ECR) allowing, in particular, the production of multicharged ions.
  • ECR electronic cyclotron resonance
  • the ions are obtained by ionization, in a closed enclosure, such as a microwave cavity, of a gaseous medium consisting of one or more gases or metallic vapors, by means of electrons strongly accelerated by electronic cyclotron resonance.
  • HF high frequency electromagnetic field
  • the quantity of ions that can be produced results from the competition between two processes: on the one hand, the formation of ions by electronic impact on neutral atoms constituting the gas to be ionized and, on the other hand, the destruction of these same ions by recombination, single or multiple, during a collision of the latter with a neutral atom; this neutral atom can come from the gas not yet ionized or else be produced on the walls of the enclosure by impact of an ion on said walls.
  • This drawback is avoided by confining, in the enclosure constituting the source, the ions formed, as well as the electrons used for their ionization.
  • This is achieved by creating inside the enclosure radial and axial magnetic fields, defining a so-called "equimagnetic" surface, having no contact with the walls of the enclosure and on which the condition of electronic cyclotron resonance is satisfied.
  • This surface has the shape of a rugby ball. The closer this equimagnetic surface is to the walls of the enclosure, the greater its efficiency because it makes it possible to limit the volume of presence of neutral atoms and therefore the amount of collisions between ions and neutral atoms.
  • This surface also makes it possible to confine the ions and the electrons produced by ionization of the gas. Thanks to this confinement, the electrons created have the time to bombard the same ion several times and fully ionize it.
  • FIG. 1 there is shown schematically an ion source according to the prior art.
  • This source comprises an enclosure 1 constituting a resonant cavity which can be excited by a high frequency electromagnetic field (HF).
  • HF high frequency electromagnetic field
  • This electromagnetic field is produced by a generator 3 of electromagnetic waves; it is introduced inside the enclosure 1 via a waveguide 5 and a transition cavity 20.
  • This source also includes an externally shielded magnetic structure (7, 9, 11), the shielding 11 of which makes it possible to magnetize only the volume useful for electronic cyclotron resonance in the enclosure 1.
  • This magnetic structure further comprises the shielding 11, permanent magnets 7 and solenoids 9, arranged around the enclosure 1 and respectively creating a radial magnetic field and an axial magnetic field. These two magnetic fields are superimposed and distributed throughout the enclosure; they thus form a resulting magnetic field which defines the resonant equimagnetic surface 13 inside the enclosure 1.
  • First and second pipes 21 and 23 connect the opening 19 of the shield 11 to respective openings 25 and 27 of the transition cavity 20, these openings being located on the lateral faces of the cavity 20 which has the shape of a cube.
  • the ratio of the diameters of these two pipes 21, 23 is such that it is possible to assimilate the latter to a coaxial line of characteristic impedance of the order of 85 Ohms.
  • a coaxial line preferably propagates an electromagnetic Transverse Electro-Magnetic (TEM) mode in which the electromagnetic field E is transverse to the direction of propagation of the waves and perpendicular to the surface of the conductors, that is to say pipes 21, 23.
  • TEM Transverse Electro-Magnetic
  • said gas is introduced into the enclosure 1 via a gas pipe 30 connected to the opening 27 of the transition cavity 20.
  • the gas and the electromagnetic waves introduced into the cavity 20 are transmitted to enclosure 1 by the first and second pipes 21 and 23, the role of which is to enable said waves to be transmitted to said enclosure and to inject them there along the longitudinal axis 15.
  • enclosure 1 the combination of the axial magnetic field and the electromagnetic field makes it possible to strongly ionize the gas introduced.
  • the electrons produced are then strongly accelerated by electronic cyclotron resonance, which leads to the formation of a plasma of hot electrons confined in the volume limited by the equimagnetic surface 13.
  • the ions then formed in enclosure 1 are extracted therefrom by an electric extraction field generated by a potential difference applied between an electrode 31 and enclosure 1.
  • the electrode 31 and enclosure 1 are all two connected to a source 33 of electrical power, the electrode 31 being positioned outside the opening 17 of the enclosure 1.
  • a pulse generator 35 itself located upstream of a power source 37 connected to the generator d 'electromagnetic waves.
  • Said pulse generator 35 controls said power source 37 by adjusting the useful cycle, namely the ratio between the duration of a pulse and the period of the pulses.
  • means 39 for measuring total pressure are connected to an input of a comparator 41, the output of which is itself connected to a valve 43 of the gas pipe 30.
  • a comparator 41 On a second input of the comparator 41, a reference voltage R is applied and compared with the measured value of the ion current to give, at the output of the comparator, the value to be transmitted to the valve 43.
  • This valve 43 makes it possible to act on the quantity of gas to be introduced into enclosure 1, so as to automatically regulate the ion current.
  • an adaptation piston 45 connected to a third lateral opening 29 of the cavity 20, makes it possible to adjust the internal volume of said cavity 20.
  • the adjustment of said piston 45 is used to tune all the internal volumes of the cavity 20 on the frequency of the electromagnetic waves in order to obtain a minimum of reflected waves, that is to say waves which return to the wave generator 3.
  • these internal volumes are tuned to the frequency of the electromagnetic waves, the waves injected into the cavity 20 by the generator 3 are almost completely transmitted, via the pipes 21 and 23, to the enclosure 1 containing the plasma, then absorbed by the equimagnetic surface 13 .
  • the second pipe 23 is transparent to electromagnetic waves at its end 23a, the end close to the opening 19 of the enclosure 1 located opposite the shielding 11.
  • this transparent part 23a there is an axial magnetic field from the solenoids, an electromagnetic field and a high gas pressure.
  • the electromagnetic field comes from electromagnetic waves transmitted between the first pipe 21 and a non-transparent part 23b of the second pipe 23, and which pass through the transparent part 23a of the second pipe 23. Therefore, an electronic cyclotron resonance can take place at inside the end 23a of the second pipe 23 in a volume where there is a high gas pressure.
  • This transparent end to the electromagnetic waves therefore constitutes a self-regulated pre-ionization stage, where the excess incident power of the electromagnetic waves is transmitted without reflection to the electronic cyclotron resonance zone formed by the equimagnetic surface 13.
  • the plasma confined in the equimagnetic surface 13 naturally carries a positive potential with respect to the enclosure 1.
  • the electrons of this confined plasma are heated by the cyclotronic resonance of the electrons and some of these electrons, too energetic, s escape from containment. They will then strike enclosure 1 which, under this effect, charges negatively.
  • the confined plasma therefore has a more positive polarity than that of enclosure 1.
  • the potential difference created between the enclosure 1 and the confined plasma is at the origin of an electric field E.
  • This field E allows in particular the transfer of the confined ions towards the opening 17 of the enclosure 1.
  • the preionization plasma which extends to the equimagnetic surface 13 is in contact with the confined plasma. Now, said plasma preionization conductive and brought to the same potential as the enclosure 1. The electric field E is then disturbed, which affects the capacities of the ion source.
  • the present invention precisely makes it possible to optimize this electric field E by isolating the preionization plasma from the confined plasma while ensuring the transmission of the electromagnetic wave. It proposes, in fact, a central injection system for the preionization plasma electrically supplied by a voltage source.
  • This source is characterized in that the second pipe, in which a resonance occurs at a resonance point, is connected to a second source of electrical power.
  • the first and second electrical power sources are identical and of the same polarity so as to bring the enclosure and the second pipe to the same potential with respect to the ground.
  • the transparent tube is made of quartz
  • the conductive tube is made of copper
  • the refractory metal tube is made of a tantalum sheet.
  • Figure 2 shows an ion source according to the invention. It represents, in fact, the ion source of the prior art, as described above, to which is added a second electrical power source 50 and on which the second pipe has been modified in accordance with the invention. This pipe bears, in FIG. 2, the reference 52.
  • the second power source 50 is identical and of the same polarity as the first power source 33. It allows the delivery of a variable voltage between substantially 10 and 20 Kv.
  • the power source 50 is connected, by its positive pole, to the second pipe 52 and, by its negative pole, to the earth as well as to the negative pole of the power source 33.
  • the existence of the second power source 50 makes it possible to bring the enclosure 1 and the pipe 52 to potentials independent of each other, and to identical polarities.
  • the pipe 52 will retain its positive polarity, as will the preionization plasma that it contains.
  • said preionization plasma which has a polarity roughly similar to the polarity of the plasma confined in the equimagnetic surface 13, remains isolated from the confined plasma.
  • This pipe 52 comprises a quartz tube 53 placed inside the first pipe 21 and which crosses the entire cavity 20 to the mouth of the gas pipe 30.
  • This quartz tube 53 can be, more generally, a tube made of a dielectric transparent material.
  • quartz has the advantage of not allowing degassing.
  • the pipe 52 also comprises a very thin copper tube 54 threaded on the quartz tube 53, that is to say surrounding said quartz tube so as to match the external surface of the quartz tube 53.
  • This copper tube 54 is conductive and allows the electromagnetic waves introduced into the pipe 21 to be transmitted.
  • the copper tube 54 is welded to the wall 28 of the cavity 20.
  • the copper tube 54 does not completely cover the quartz tube 53. In fact, a part 53a of the quartz tube 53 must remain transparent to electromagnetic waves.
  • the copper tube 54 can be replaced by the metallization of the quartz tube 53, that is to say by a silver deposit on said quartz tube.
  • the pipe 52 further comprises a refractory metal tube 55 threaded inside the quartz tube 53, that is to say placed against the internal wall of said quartz tube.
  • the refractory metal tube 55 can be produced by a thin tantalum sheet wound inside the quartz tube 53 so as to match its internal surface of almost perfect way.
  • This refractory metal tube 55 can also be produced, according to the same principle, by a sheet of tunsgtene.
  • This refractory metal tube 55 covers the internal surface of the quartz tube 53 over its entire length, except in its part 53a which is left transparent to electromagnetic waves.
  • the electric fields (not shown in the figures) of the electromagnetic waves are optimum at points A, B and C represented in FIG. 2. More precisely, the RCE resonance is optimized at point C, when the electric field reaches its maximum value, when it is perpendicular to the resonant induction field and when it is on a cylinder of small radius, that is to say on the second pipe 52 of small radius.
  • the preionization plasma created in the pipe 52 is so dense that it becomes practically conductive, flourishing up to the equimagnetic surface 13, thus reaching point B.
  • This equimagnetic surface 13 contains the confined plasma which is capable of absorbing and reflecting electromagnetic waves, thus making said surface 13 semiconductor, from point B to point A.
  • the RCE ion source behaves like a coaxial line up to point A of the magnetic axis 15. This open line is then the seat of standing waves between point A and piston 45.
  • the distance L between the point C and the tube 55 is 2.96 cm.
  • the positive polarization of the pipe 52 by a power source 50 makes it possible to isolate the pre-ionized plasma in said pipe and the plasma confined in the equimagnetic surface 13 so as to obtain the optimum establishment of the electric field E of extraction ions without disturbing the transmission of electromagnetic waves necessary for the RCE phenomenon.
  • This device makes it possible to increase the performance of a known ion source (such as that shown in FIG. 1) by a factor of 3 to 4.

Claims (8)

  1. Elektronenzyklotronresonanz-Ionenquelle, umfassend:
    - einen Behälter (1), der ein Plasma von durch Elektronenzyklotronresonanz erzeugten Ionen und Elektronen enthält,
    - eine magnetische Struktur (11), die den Behälter umgibt und in seinem Inneren zwei magnetische Felder, ein radiales und ein axiales, erzeugt, welche ein Einschließen in dem Behälter sicherstellen,
    - ein System zur Extraktion der Ionen aus dem Behälter, das an eine Quelle (33) zur elektrischen Versorgung angeschlossen ist,
    - einen Hohlraumresonator (20) für Übergänge, der mit einem Generator (3) elektromagnetischer Wellen verbunden ist,
    - eine erste Rohrleitung (21), die leitfähig ist und den Behälter und den Hohlraumresonator vakuumdicht verbindet, und
    - eine zweite Rohrleitung (52), die mindestens zum Teil leitfähig ist, durch die erste Rohrleitung sowie durch den Hohlraumresonator axial hindurchgeht und in dem Behälter mündet,
       dadurch gekennzeichnet, daß die zweite Rohrleitung, in der eine Resonanz an einem Resonanzpunkt (C) auftritt, an eine zweite Quelle (50) zur elektrischen Versorgung angeschlossen ist.
  2. Ionenquelle nach Anspruch 1, dadurch gekennzeichnet, daß die erste und die zweite Quelle zur elektrischen Versorgung gleichartig und von gleicher Polarität sind, um den Behälter und die zweite Rohrleitung auf das gleiche Potential gegenüber der Masse zu bringen.
  3. Ionenquelle nach einem der Ansprüche 1 und 2, dadurch gekennzeichnet, daß die zweite Rohrleitung
    - ein strahlungsdurchlässiges Rohr (53) aus einem dielektrischen Material,
    - ein leitfähiges Rohr (54) von geringer Dicke, welches zum Teil das transparente Rohr überdeckt, und
    - ein Rohr aus hitzebeständigem Metall (55) von geringer Dicke umfaßt, das an einem Teil der Innenfläche des transparenten Rohres angebracht ist.
  4. Ionenquelle nach Anspruch 3, dadurch gekennzeichnet, daß das leitfähige Rohr das transparente Rohr von dem Teil an, der durch den Hohlraumresonator hindurchgeht, bis hin zu einer kritischen Entfernung L = C/F von dem Resonanzpunkt (C) überdeckt, worin C die Lichtgeschwindigkeit ist und F die Frequenz der elektromagnetischen Welle.
  5. Ionenquelle nach einem der Ansprüche 3 und 4, dadurch gekennzeichnet, daß das Rohr aus hitzebeständigem Metall den Teil der Innenfläche des transparenten Rohres von dem Teil an, der durch den Hohlraumresonator hindurchgeht, bis hin zu einer kritischen Entfernung L = C/F von dem Resonanzpunkt (C) überdeckt, worin C die Lichtgeschwindigkeit ist und F die Frequenz der elektromagnetischen Welle.
  6. Ionenquelle nach einem der Ansprüche 3 bis 5, dadurch gekennzeichnet, daß das strahlungsdurchlässige Rohr ein Quarzrohr ist.
  7. Ionenquelle nach einem der Ansprüche 3 bis 6, dadurch gekennzeichnet, daß das leitfähige Rohr aus Kupfer ist.
  8. Ionenquelle nach einem der Ansprüche 3 bis 7, dadurch gekennzeichnet, daß das Rohr aus hitzebeständigem Metall mit einer Tantalfolie hergestellt ist.
EP92402460A 1991-09-11 1992-09-09 Elektronzyklotronresonanz-Ionenquelle mit koaxialer Zuführung elektromagnetischer Wellen Expired - Lifetime EP0532411B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9111206A FR2681186B1 (fr) 1991-09-11 1991-09-11 Source d'ions a resonance cyclotronique electronique et a injection coaxiale d'ondes electromagnetiques.
FR9111206 1991-09-11

Publications (2)

Publication Number Publication Date
EP0532411A1 EP0532411A1 (de) 1993-03-17
EP0532411B1 true EP0532411B1 (de) 1995-12-06

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EP92402460A Expired - Lifetime EP0532411B1 (de) 1991-09-11 1992-09-09 Elektronzyklotronresonanz-Ionenquelle mit koaxialer Zuführung elektromagnetischer Wellen

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US (1) US5350974A (de)
EP (1) EP0532411B1 (de)
JP (1) JPH05205648A (de)
DE (1) DE69206543T2 (de)
FR (1) FR2681186B1 (de)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5539274A (en) * 1993-09-07 1996-07-23 Tokyo Electron Limited Electron beam excited plasma system
US6812647B2 (en) * 2003-04-03 2004-11-02 Wayne D. Cornelius Plasma generator useful for ion beam generation
FR2861947B1 (fr) * 2003-11-04 2007-11-09 Commissariat Energie Atomique Dispositif pour controler la temperature electronique dans un plasma rce
US20080128641A1 (en) * 2006-11-08 2008-06-05 Silicon Genesis Corporation Apparatus and method for introducing particles using a radio frequency quadrupole linear accelerator for semiconductor materials
US20100290575A1 (en) * 2009-05-15 2010-11-18 Rosenthal Glenn B Particle beam isotope generator apparatus, system and method
CN101808459A (zh) * 2010-03-16 2010-08-18 清华大学 一种用于管状高分子材料支架内表面改性的低温等离子体处理装置
CN102333410B (zh) * 2011-09-16 2013-02-06 西安交通大学 一种用于刻蚀光阻材料的大气压冷等离子体射流装置

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2556498B1 (fr) * 1983-12-07 1986-09-05 Commissariat Energie Atomique Source d'ions multicharges a plusieurs zones de resonance cyclotronique electronique
FR2595868B1 (fr) * 1986-03-13 1988-05-13 Commissariat Energie Atomique Source d'ions a resonance cyclotronique electronique a injection coaxiale d'ondes electromagnetiques

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DE69206543D1 (de) 1996-01-18
US5350974A (en) 1994-09-27
JPH05205648A (ja) 1993-08-13
DE69206543T2 (de) 1996-07-11
EP0532411A1 (de) 1993-03-17
FR2681186A1 (fr) 1993-03-12
FR2681186B1 (fr) 1993-10-29

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