Classifications

• • 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
  • H01J37/32—Gas-filled discharge tubes
  • H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
  • H01J37/32357—Generation remote from the workpiece, e.g. down-stream
• • 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 electronic cyclotron resonance device for creating an ion beam. More particularly, the invention relates to an ion source which comprises means for supplying gas, microwave power and electrical voltage.
• a surface to be treated is immersed in a vacuum enclosure as well as a device capable of projecting an ion beam on said surface.
• the gas is conveyed in an ionization chamber where it is simultaneously subjected to the action of a variable electric field at very high frequency and of a permanent magnetic field, under such conditions is in electronic cyclotron resonance, which increases the ionization efficiency of the gas.
• One of the major drawbacks of the known devices lies in the fact that the gas is not suitably located in the ionization chamber, so that it only undergoes partial ionization.
• the electric power which is necessary for the excitation of the gas is supplied by a microwave generator whose power must be coupled to the plasma so that it occurs only very little. radiation losses outside the device.
• the present invention aims to provide a simple and economical device which in particular overcomes the drawbacks mentioned above and which is also compact and reliable.
• the present invention relates to an electronic cyclotron resonance device for creating an ion beam comprising an ionization chamber, means for supplying gas inside the ionization chamber, and a coaxial transmission line.
• the gas supply means comprising a conduit whose inlet orifice is located outside the device, and whose l outlet port opens into the ionization chamber, characterized in that an antenna is housed in the ionization chamber, the outlet port of the conduit for the gas supply means opening out to the inside said antenna, which is in the form of a closed hollow body and has orifices provided in its wall so that a gas introduced into the conduit spreads into the ionization chamber through the 'antenna, at i inside an electronic cyclotron resonance zone.
• the orifices of the antenna are provided with capillary tubes.
• the conduit is electrically conductive and one of its ends is electrically connected to the antenna, its other end being electrically connected to the wall of the ionization chamber at a point which is distant from the coaxial line of transmission by an odd multiple of a quarter of the wavelength in vacuum of the microwave.
• the antenna is not in direct contact with the wall of the ionization chamber, but it is placed at the same electrical potential as the wall of the ionization chamber, by being connected to it by the through the electrically conductive conduit.
• the electrical connection thus indirectly established between the antenna and the wall of the ionization chamber is transparent to microwaves, so that the transmission of microwaves to the antenna is not disturbed.
• the coaxial transmission line comprises a coupling system constituted by two capacitors, the first being formed on the central conductor of the coaxial line, and having a length equal to an odd multiple of a quarter of the wavelength in the dielectric of this capacitor of the microwave, and the second being formed on the external conductor of the coaxial line, and having a length equal to an odd multiple of a quarter of the wavelength in the vacuum of the microwave.
• the capacitor provided on the central conductor lets pass the electrical signal from the microwave generator while ensuring galvanic isolation between the parts of the transmission line located on either side of said capacitor, while the capacitor provided on the external conductor also ensures galvanic isolation and constitutes a barrier vis-à-vis the outside, which prevents microwave radiation.
• This solution thus makes it possible to bring the microwave power in the transmission line maintained at zero average potential to the vicinity of the ionization chamber.
• This device comprises a coaxial connector element 1 which is intended to be assembled with another coaxial connector element (not shown), connected to a coaxial cable (not shown) coming from a microwave generator (not shown).
• the central contact 2 of the coaxial connector element 1 is extended by an electric line formed by a first central conductor 3 and a second central conductor 4. These two central conductors are coupled at their ends by means of an axial recess 5 formed at the end of the first central conductor 3 and to a protruding pin 6 of the corresponding end of the second central conductor 4, which pin 6 enters the recess 5 of the first central conductor, a dielectric 7 providing galvanic isolation between these two central conductors.
• the ends of the two central conductors thus coupled form a first capacitor within the meaning of the invention.
• the overlap length between pin 6 and recess 5 is equal to an odd multiple of a quarter of the wavelength in dielectric 7 of the microwave supplied by the microwave generator.
• Each central conductor is housed in a cylindrical cavity 8, 9 formed, for the first central conductor 3, in a first cylindrical body 10, forming an external conductor, integral with the external part of the connector element 1, and, for the second central conductor 4, in a second cylindrical body 11, forming an external conductor, integral with an ionization chamber 12.
• the second cylindrical body 11 has a tubular wall 11a which surrounds the first cylindrical body 10 over a height 10a equal to an odd multiple of a quarter of the wavelength in the vacuum of the microwave.
• This arrangement constitutes a second capacitor within the meaning of the invention, and forms with the first capacitor 5, 6, 7 a coupling system which makes it possible to transmit the microwave energy from the coaxial transmission line to the ionization chamber. 12.
• the second central conductor 4 extends to an antenna 14 housed in the ionization chamber 12 and being in the form of a closed cylindrical hollow body.
• An alumina ring 15 is provided at the base of the antenna 14 to, on the one hand, avoid direct electrical contact between the wall of the ionization chamber 12 and the antenna 14 and, on the other hand, maintain a gas tightness between the interior volume of the ionization chamber 12 and the free annular space 13 lai ⁇ é around the second tube 4.
• the antenna 14 is provided at its lower end with a plurality of orifices provided with capillary tubes 16 which communicate the interior of the antenna with the ionization chamber.
• a bent conduit 17, electrically conductive opens on the one hand inside the antenna 14, on the other hand outside the device.
• a gas is introduced into the bent conduit 17, it diffuses into the ionization chamber 12 through capillary tubes 16 which have the function of directing the gas towards the electronic cyclotron resonance zone 19, shown diagrammatically in broken lines, in distributing it as homogeneously as possible in this zone 19.
• the bent conduit 17 comprises a branch 17a coaxial with the second central conductor 4 and located inside the latter, and a branch 17b perpendicular to said second central conductor 4, located in the sleeve 18.
• the distance which separates the disc 20 from the second tube 4 is equal to an odd multiple of a quarter of the wavelength in the vacuum of the microwave, so that the electrical connection which is established by the disc 20 between the electrical conduit 17 and the sleeve 18 is transparent to microwaves.
• this electrical connection has the sole effect of equalizing the potentials of the ionization chamber and the antenna. In this way, the formation of excessively large ion sheaths in the ionization chamber 12, in particular around the antenna 14, is avoided.
• a set of extraction grids 21 is placed at the outlet of the ionization chamber.
• dielectric balls 22 are arranged in rings at the periphery of each central conductor.
• Ball supports 23 are provided for this purpose in the first and second bodies 10 and 11 to immobilize the balls 22 bearing against the conductors 3 and 4. Although these supports 23 extend over the entire periphery of the central conductors, only a part has been shown in the drawing for the sake of clarity.
• the entire device is intended to be placed inside a vacuum enclosure (not shown) in which a secondary vacuum or an ultra-vacuum is established.
• the gas is introduced into the ionization chamber 12 through the bent conduit 17 and the antenna 14, at a pressure between 10 ⁇ and 10 " Torr.
• the configuration in two bodies 10 and 11 of the device allows the rotation of the ionization chamber 12 with respect to its axis, the first body 10 remaining fixed while the second body 11, integral with the ionization chamber, rotates with the latter.
• the coupling system with two capacitors which has a shape of revolution, then also serves as a rotary connecting piece ensuring the continuity of the electric line despite the rotational movements of the ionization chamber 12.
• a set of inclined extraction grids 21 is thus provided so that the rotation of the ionization chamber results in a change of orientation of the ion beam.
• a flexible conduit is advantageously used so as to allow the angular movement of the branch 17b of the conduit perpendicular to the second tube 4.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Plasma & Fusion (AREA)
• Analytical Chemistry (AREA)
• Combustion & Propulsion (AREA)
• Particle Accelerators (AREA)
• Electron Sources, Ion Sources (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 1995
  • 1995-02-16 FR FR9501771A patent/FR2730858B1/fr not_active Expired - Fee Related
• 1996
  • 1996-02-16 WO PCT/FR1996/000259 patent/WO1996025755A1/fr not_active Ceased
  • 1996-02-16 EP EP96904156A patent/EP0809855A1/de not_active Withdrawn
  • 1996-02-16 JP JP8524727A patent/JPH11500570A/ja active Pending

Non-Patent Citations (1)

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