EP0056899A1 - Gasionenquelle - Google Patents

Gasionenquelle Download PDF

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Publication number
EP0056899A1
EP0056899A1 EP19810305685 EP81305685A EP0056899A1 EP 0056899 A1 EP0056899 A1 EP 0056899A1 EP 19810305685 EP19810305685 EP 19810305685 EP 81305685 A EP81305685 A EP 81305685A EP 0056899 A1 EP0056899 A1 EP 0056899A1
Authority
EP
European Patent Office
Prior art keywords
gas
needle
ion source
electrode
gas ion
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP19810305685
Other languages
English (en)
French (fr)
Inventor
Neil Arthur Pashley
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dubilier Scientific Ltd
Original Assignee
Dubilier Scientific Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Dubilier Scientific Ltd filed Critical Dubilier Scientific Ltd
Publication of EP0056899A1 publication Critical patent/EP0056899A1/de
Ceased legal-status Critical Current

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Classifications

    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/06—Sources
    • H01J2237/08—Ion sources
    • H01J2237/0802—Field ionization sources
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/06—Sources
    • H01J2237/08—Ion sources
    • H01J2237/0802—Field ionization sources
    • H01J2237/0807—Gas field ion sources [GFIS]

Definitions

  • the present invention relates to a gas ion source such as used in industry for material processing and surface analysis in vacuum.
  • ion beams are generated either by a glow discharge, electron bombardment excitation or radio frequency (RF) excitation.
  • RF radio frequency
  • a gas stream is ionised by an electric field set up between a first electrode in the form of a hollow needle through which a gas to be ionised may flow and a second electrode situated adjacent the needle in such a manner that gas issuing from the interior of the needle is ionised by electrons excited by the electric field.
  • the gas used is argon, but the ionisation of other gases and volatile metals is also possible.
  • Satisfactory ionisation of gas depends on two factors: gas pressure and excitation force.
  • the structure of the preferred embodiment of the ion source of this invention localises these two factors to provide a well-defined origin of ionisation unlike, for example, the conventional gas discharge source which can ionise anywhere between two spaced plates.
  • the existence of a well-defined origin of ionisation leads to improved focussing of the ion beam and greater current density.
  • the relatively narrow needle orifice opens into a large space, with the second, or extractor, electrode positioned in front of, but spaced from, the open end of the needle.
  • This construction leads to the two necessary conditions for satisfactory ionisation of the gas: firstly, emergence of gas from the narrow orifice into the large space leads to a localised region of relatively high gas pressure in the immediate area of the orifice; secondly the physical narrowness of the needle about the orifice means that the electric field set up between the needle and the extractor electrode is also in the same area.
  • the atoms of gas emerge from the needle, they enter the high pressure region and are ionised by electrons traversing the inter-electrode space.
  • the resulting ions are then accelerated away from the needle in a well-defined narrow beam by means of the extractor electrode.
  • the extractor electrode is formed with an aperture through which the ion beam may pass.
  • the gas ion source comprises a needle assembly 1 and extractor 2 which are carried on a mounting flange 3 by means of a pair of spaced pillars 4.
  • the needle assembly comprises a hollow needle 5 made of refractory metal such as tungsten which is mounted in an insulating support 6. Gas is supplied to the interior passage 7 within the needle 5 via a tube 8 which passes through the flange 3. If desired preheating of the gas may be carried out by means of a heater (not shown) associated with the tube 8. Such preheating may be desirable in certain circumstances in order to prevent the condensation of volatile vapours in the tube.
  • the needle tapers at its free end to a diameter typically of 75yc.
  • the outlet end of passage 7 likewise tapers at the free end of the needle to provide a constriction having a diameter typically of 25 ⁇ .
  • the extractor 2 comprises a flat circular extractor electrode 9 having a through-aperture 10, typically of 100 ⁇ . diameter, at its centre.
  • the electrode 9 is supported by a generally cylindrical electrode support member 11 in such a way that the aperture 10 lies directly in front of the exit of the needle 5.
  • the distance between the extractor electrode and the tip of the needle is typically lmm.
  • the extractor electrode and needle are connected by way of pillars 4 to respective terminals of an electrical power supply unit (not shown) so that, in use, the needle has a positive potential with respect to the extractor electrode.
  • the voltage applied between the needle and the extractor electrode is typically between 5,000 and 10,000 volts.
  • a suitable gas such as argon is passed along the tube 8 to the passage 7 within the needle.
  • the constricted portion at the mouth of the passage 7 has a self-regulating effect and ensures that a well defined stream of gas emerges into the space between the needle and the extractor electrode.
  • the sudden emergence of gas from the constricted portion of passage 7 into the relatively wide space within the extractor results in a localised region of relatively high pressure at the exit of the passage 7 and it is in this high pressure region, subjected as it is to the electric field existing between the needle and the extractor electrode, that the ionisation of the gas takes place.
  • the ions are created in a highly localised self contained and self sustaining discharge which is initiated by some random external event.
  • the ion source is used in an evacuated atmosphere, with ambient pressures no greater than 10- 5 mm Hg.
  • ambient pressure is 1 millionth of an atmosphere while the pressure in the localised high pressure region adjacent the exit to the passage 7 is typically k atmosphere. This leads to a very considerable pressure gradient in the 1 mm space between the tip of the needle and the extractor electrode.
  • FIG. 3 shows a typical experimental test set-up.
  • the ion source is mounted within a vacuum chamber 12 above a collector electrode 13. Gas to be ionised is supplied to tube 8 form a cylinder 14, the inlet gas pressure being monitored by a gauge 15.
  • An electrical power supply 16 has positive and negative outputs connected to the needle 5 and extractor 2 respectively in order to produce a high electric field between the two.
  • the collector electrode is likewise connected to the negative output, via a microammeter.
  • the ion beam is drawn out of the ion source by means of the electric field existing between the extractor electrode and the needle.
  • the extractor electrode is intended to provide the high electrical gradient needed for ionisation and also to provide the acceleration of the ion beam as it leaves the region of ionisation.
  • the collector electrode is intended to represent a target workpiece which is to be bombarded, and is not part of the ion source per se.
  • the energy of the ion beam as it strikes the collector electrode is dependent upon the magnitude of the voltage between the needle and the collector electrode.
  • the potential of the collector electrode will be capable of adjustment independently of that of the extractor electrode in order to take account of varying requirements in use.
  • the ion source described above can be used with a wide variety of gases and volatile metals. Examples are argon, helium, neon, nitrogen, hydrogen, deuterium, oxygen or volatile arsenic or boron. In the case of oxygen, problems can arise due to erosion of the needle, and the source should be operated at a lower current to reduce this.
  • the gas pressure, as recorded on gauge 15, is in the region of 120 to 280 mm Hg.
  • the ion source described above will produce a reliable high intensity beam of ions and finds wide application in industry in particular for material processing and surface analysis.
  • the ion source is mounted within a vacuum chamber and the beam of ions for example argon ions, produced by the source is directed at the target material.
  • the resultant ion bombardment will sputter or etch away material from the target. Electrons and ions released by the target during ion bombardment can be analysed to determine the existence and concentration of the various elements present.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Electron Sources, Ion Sources (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
EP19810305685 1980-12-04 1981-12-02 Gasionenquelle Ceased EP0056899A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8038922 1980-12-04
GB8038922 1980-12-04

Publications (1)

Publication Number Publication Date
EP0056899A1 true EP0056899A1 (de) 1982-08-04

Family

ID=10517754

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19810305685 Ceased EP0056899A1 (de) 1980-12-04 1981-12-02 Gasionenquelle

Country Status (2)

Country Link
EP (1) EP0056899A1 (de)
JP (1) JPS57132654A (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0063493B1 (de) * 1981-04-20 1985-09-04 Inoue-Japax Research Incorporated Verfahren und Vorrichtung für die Bearbeitung von Werkstücken mittels Ionen
EP0346271A1 (de) * 1988-06-10 1989-12-13 Sri International Nach der Mikroelektronik aufgebauter Feldionisator und Verfahren zur Herstellung desselben
EP1826809A1 (de) * 2006-02-22 2007-08-29 FEI Company Partikel-Optisches Gerät ausgestattet mit einer Gasionenquelle
US9941094B1 (en) 2017-02-01 2018-04-10 Fei Company Innovative source assembly for ion beam production

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3309873A (en) * 1964-08-31 1967-03-21 Electro Optical Systems Inc Plasma accelerator using hall currents
US3955090A (en) * 1973-12-27 1976-05-04 Exxon Nuclear Company, Inc. Sputtered particle flow source for isotopically selective ionization
FR2344116A1 (fr) * 1976-03-11 1977-10-07 Schwerionenforsch Gmbh Source de production d'ions a charge simple ou multiple
DE2701395B2 (de) * 1977-01-14 1979-03-29 Dr. Franzen Analysentechnik Gmbh & Co Kg, 2800 Bremen Ionenquelle für die chemische Ionisierung von Atomen und Molekülen

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3309873A (en) * 1964-08-31 1967-03-21 Electro Optical Systems Inc Plasma accelerator using hall currents
US3955090A (en) * 1973-12-27 1976-05-04 Exxon Nuclear Company, Inc. Sputtered particle flow source for isotopically selective ionization
FR2344116A1 (fr) * 1976-03-11 1977-10-07 Schwerionenforsch Gmbh Source de production d'ions a charge simple ou multiple
DE2701395B2 (de) * 1977-01-14 1979-03-29 Dr. Franzen Analysentechnik Gmbh & Co Kg, 2800 Bremen Ionenquelle für die chemische Ionisierung von Atomen und Molekülen

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0063493B1 (de) * 1981-04-20 1985-09-04 Inoue-Japax Research Incorporated Verfahren und Vorrichtung für die Bearbeitung von Werkstücken mittels Ionen
EP0346271A1 (de) * 1988-06-10 1989-12-13 Sri International Nach der Mikroelektronik aufgebauter Feldionisator und Verfahren zur Herstellung desselben
EP1826809A1 (de) * 2006-02-22 2007-08-29 FEI Company Partikel-Optisches Gerät ausgestattet mit einer Gasionenquelle
EP1830383A3 (de) * 2006-02-22 2007-12-19 FEI Company Mit einer Gasionenquelle ausgestattete teilchenoptische Vorrichtung
CN101026080B (zh) * 2006-02-22 2010-04-21 Fei公司 装备有气体离子源的粒子光学设备
US7772564B2 (en) 2006-02-22 2010-08-10 Fei Company Particle-optical apparatus equipped with a gas ion source
US9941094B1 (en) 2017-02-01 2018-04-10 Fei Company Innovative source assembly for ion beam production
US10651005B2 (en) 2017-02-01 2020-05-12 Fei Company Innovative source assembly for ion beam production

Also Published As

Publication number Publication date
JPS57132654A (en) 1982-08-17

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PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Designated state(s): AT BE CH DE FR GB IT LU NL SE

17P Request for examination filed

Effective date: 19830204

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN REFUSED

18R Application refused

Effective date: 19850624

IECL Ie: translation for ep claims filed
RIN1 Information on inventor provided before grant (corrected)

Inventor name: PASHLEY, NEIL ARTHUR