EP0570211A1 - Structure cathodiques - Google Patents

Structure cathodiques Download PDF

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Publication number
EP0570211A1
EP0570211A1 EP93303680A EP93303680A EP0570211A1 EP 0570211 A1 EP0570211 A1 EP 0570211A1 EP 93303680 A EP93303680 A EP 93303680A EP 93303680 A EP93303680 A EP 93303680A EP 0570211 A1 EP0570211 A1 EP 0570211A1
Authority
EP
European Patent Office
Prior art keywords
aperture
tip
coating
substrate
grid layer
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.)
Withdrawn
Application number
EP93303680A
Other languages
German (de)
English (en)
Inventor
Neil Alexander Cade
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.)
BAE Systems Electronics Ltd
Original Assignee
GEC Marconi Ltd
Marconi Co 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 GEC Marconi Ltd, Marconi Co Ltd filed Critical GEC Marconi Ltd
Publication of EP0570211A1 publication Critical patent/EP0570211A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/022—Manufacture of electrodes or electrode systems of cold cathodes
    • H01J9/025—Manufacture of electrodes or electrode systems of cold cathodes of field emission cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2201/00—Electrodes common to discharge tubes
    • H01J2201/30—Cold cathodes
    • H01J2201/304—Field emission cathodes
    • H01J2201/30403—Field emission cathodes characterised by the emitter shape
    • H01J2201/30426—Coatings on the emitter surface, e.g. with low work function materials

Definitions

  • This invention relates to cathode structures, and particularly to the manufacture of field emission cathodes.
  • Typical field emitter cathodes shown schematically in Figure 1 of the accompanying drawings, consist of tips 1 which are 1-2 ⁇ m high and are a few ( ⁇ 10) microns apart, with each tip in the centre of an aperture 3 in a grid 5, the grid being supported on, but electrically isolated from, the tip-bearing substrate 6 by an insulating spacer layer 7. With this geometry, emission currents of many micro-amps per tip are obtained from each tip for grid-tip voltages of about 100V, provided that the tips have radii of approximately 10nm.
  • the individual tips must have very accurately similar tip radii if each is to contribute to the total emission current at the single common applied voltage. It is only by having very similar emission currents from each tip that high total currents can be achieved.
  • the total current per tip which can be achieved from such an array is less than a tenth of the maximum current which can be achieved from individual tips.
  • control of the accuracy of the tip geometry to within 1nm allows such an array to produce average currents per tip of approximately half the maximum individual tip current.
  • An object of the present invention is to provide a process for finely controlling the chemical, structural and geometric properties of field emission cathode tips in order to achieve larger and more stable emission currents.
  • a process for manufacturing a field emission electrode structure comprising the steps of forming a tapered cathode tip on a substrate; forming a grid layer spaced from the substrate and having an aperture substantially aligned with the cathode tip; and depositing a coating on the tip by evaporation or sputtering of coating material.
  • conventional field emission cold cathodes comprise an array of emitter tips 1 from which electrons are extracted by applying a high voltage (about 100V) to the grid structure 5, which is supported approximately 1-2 ⁇ m from the tip-bearing substrate 6 by the insulating spacer layer 7.
  • the aperture 9 in the spacer layer is preferably larger than the aperture 3 in the grid so that, over a reasonable range of angles close to the cathode axis there is no line of sight view of the insulation layer 7 from an evaporation source mentioned below.
  • a thin tip coating 11 (Figure 2) is formed by evaporation of a material (preferably a metal) on to the whole cathode structure after the fabrication of the Figure 1 device is complete.
  • a material preferably a metal
  • the lack of a line of sight view of the insulation layer from the evaporation source 8 ensures that no metal layer is formed on the insulating spacer layer 7 around the aperture 9, so that there is no shorting between the tips and the grid.
  • this process step can be carried out at the end of the cathode fabrication and after the electrical connections have been made, the step is ideally effected in the final vacuum enclosure of the device of which the cathode is a part.
  • the coating may be applied by a process similar to the firing of a reactive metal getter in a conventional thermionic cathode device. In the present invention, however, the process brings about coating of the cathode, and not removal of unwanted materials as is the intention with a getter.
  • micromachined silicon tips may be coated with a few nanometres of a non-reactive and refractory metal such as Pd, Ir or Pt. Provided that the tips are maintained at low temperature, such coatings will be relatively stable. However, it may be advantageous for the formation of the associated silicide structure (e.g. PdSi2) which will form, if the coating is carried out on cathodes maintained at high temperature, or during subsequent annealing to a high temperature. In the particular case of Pd, silicide formation will be rapid at about 400°C.
  • a non-reactive and refractory metal such as Pd, Ir or Pt.
  • silicides formed and annealed at about 500°C will form epitaxial, oriented coatings which will result in similar crystallographic orientations and therefore similar work functions on different tips, leading to similar convergence of emission properties of each tip in the array.
  • amorphisation of the emitter surface will lead to similar effects.
  • ion bombardment cleaning preferably done by introducing a noble gas into the device encapsulation and creating a plasma by suitable biasing of subsidiary electrodes (not shown), is preferably carried out to clean the tip surfaces prior to metal deposition. This process will result in an amorphous (Si) tip surface, subsequent to metal deposition. The same process may be repeated to produce an amorphous metal coating.
  • the final emitter surface is preferably a refractory metal, such material is not easily evaporated.
  • a refractory coating may be formed, however, by coating the emitter tip 1 with a lower melting point material such as Ti and subsequently reacting it with either the (Si) substrate or by gas phase atoms encircling the tip.
  • a refractory metallic TiN film may be formed by ion bombarding the evaporated Ti coating with nitrogen ions.
  • the evaporated material is made to cover not only the emitter tips but also the upper surface of the grid 5 (and also the upper surface of any additional grid (not shown) which may be provided spaced from the grid 5.
  • the layer 11 formed on the grid 5 provides an advantage in that, if the device has to operate in an environment in which the vacuum is imperfect, any resulting ion bombardment which tends to sputter coating off the tips 1, as indicated by arrows 13, will also sputter some coating off the grid or grids, as indicated by arrows 15, so that the coating material sputtered off the grid(s) will tend to recoat the tips.
  • the grid 5 (and preferably any additional grid) is made of the same material as the coating layer 11. If then, in use, the tips are subjected to ion bombardment, any coating material lost from the tips will tend to be replaced by material sputtered from the grid(s).

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Cold Cathode And The Manufacture (AREA)
EP93303680A 1992-05-15 1993-05-12 Structure cathodiques Withdrawn EP0570211A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB929210419A GB9210419D0 (en) 1992-05-15 1992-05-15 Cathode structures
GB9210419 1992-05-15

Publications (1)

Publication Number Publication Date
EP0570211A1 true EP0570211A1 (fr) 1993-11-18

Family

ID=10715537

Family Applications (1)

Application Number Title Priority Date Filing Date
EP93303680A Withdrawn EP0570211A1 (fr) 1992-05-15 1993-05-12 Structure cathodiques

Country Status (3)

Country Link
EP (1) EP0570211A1 (fr)
JP (1) JPH0644893A (fr)
GB (2) GB9210419D0 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2719155A1 (fr) * 1994-04-25 1995-10-27 Commissariat Energie Atomique Procédé de réalisation de sources d'électrons à micropointes et source d'électrons à micropointes obtenue par ce procédé.
FR2719156A1 (fr) * 1994-04-25 1995-10-27 Commissariat Energie Atomique Source d'électrons à micropointes, les micropointes comportant deux parties.
DE19609234A1 (de) * 1996-03-09 1997-09-11 Deutsche Telekom Ag Röhrensysteme und Herstellungsverfahren hierzu
US8557884B2 (en) 2002-05-31 2013-10-15 Owens Corning Intellectual Capital, Llc To enhance the thermal insulation of polymeric foam by reducing cell anisotropic ratio and the method for production thereof
US9190237B1 (en) 2014-04-24 2015-11-17 Nxp B.V. Electrode coating for electron emission devices within cavities

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5693235A (en) * 1995-12-04 1997-12-02 Industrial Technology Research Institute Methods for manufacturing cold cathode arrays
US6356014B2 (en) 1997-03-27 2002-03-12 Candescent Technologies Corporation Electron emitters coated with carbon containing layer

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2536363A1 (de) * 1974-08-16 1976-02-26 Hitachi Ltd Duennschicht-feldelektronenemissionsquelle und verfahren zu ihrer herstellung
EP0434330A2 (fr) * 1989-12-18 1991-06-26 Seiko Epson Corporation Dispositif à émission de champ et son procédé de fabrication

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3665241A (en) * 1970-07-13 1972-05-23 Stanford Research Inst Field ionizer and field emission cathode structures and methods of production
EP0365630B1 (fr) * 1988-03-25 1994-03-02 Thomson-Csf Procede de fabrication de sources d'electrons du type a emission de champ, et son application a la realisation de reseaux d'emetteurs
US5064396A (en) * 1990-01-29 1991-11-12 Coloray Display Corporation Method of manufacturing an electric field producing structure including a field emission cathode
EP0539365B1 (fr) * 1990-07-18 1997-04-23 International Business Machines Corporation Structures et procedes de fabrication de cathodes a emission de champ

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2536363A1 (de) * 1974-08-16 1976-02-26 Hitachi Ltd Duennschicht-feldelektronenemissionsquelle und verfahren zu ihrer herstellung
EP0434330A2 (fr) * 1989-12-18 1991-06-26 Seiko Epson Corporation Dispositif à émission de champ et son procédé de fabrication

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
EXTENDED ABSTRACTS vol. 86-1, no. 1, May 1986, PENNINGTON, NEW JERSEY, USA pages 403 - 404 H.H. BUSTA ET AL. 'Micromachined tungsten field emitters' *

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2719155A1 (fr) * 1994-04-25 1995-10-27 Commissariat Energie Atomique Procédé de réalisation de sources d'électrons à micropointes et source d'électrons à micropointes obtenue par ce procédé.
FR2719156A1 (fr) * 1994-04-25 1995-10-27 Commissariat Energie Atomique Source d'électrons à micropointes, les micropointes comportant deux parties.
EP0689222A2 (fr) * 1994-04-25 1995-12-27 Commissariat A L'energie Atomique Procédé de réalisation de sources d'électrons à micropointes et source d'électrons à micropointes obtenue par ce procédé
EP0689222A3 (fr) * 1994-04-25 1996-02-07 Commissariat Energie Atomique Procédé de réalisation de sources d'électrons à micropointes et source d'électrons à micropointes obtenue par ce procédé
US5635790A (en) * 1994-04-25 1997-06-03 Commissariat A L'energie Atomique Process for the production of a microtip electron source and microtip electron source obtained by this process
EP0856868A2 (fr) * 1994-04-25 1998-08-05 Commissariat A L'energie Atomique Procédé de réalisation de sources d'électrons à micropointes et source d'électrons à micropointes obtenue par ce procédé
EP0856868A3 (fr) * 1994-04-25 1998-09-30 Commissariat A L'energie Atomique Procédé de réalisation de sources d'électrons à micropointes et source d'électrons à micropointes obtenue par ce procédé
DE19609234A1 (de) * 1996-03-09 1997-09-11 Deutsche Telekom Ag Röhrensysteme und Herstellungsverfahren hierzu
US8557884B2 (en) 2002-05-31 2013-10-15 Owens Corning Intellectual Capital, Llc To enhance the thermal insulation of polymeric foam by reducing cell anisotropic ratio and the method for production thereof
US9190237B1 (en) 2014-04-24 2015-11-17 Nxp B.V. Electrode coating for electron emission devices within cavities

Also Published As

Publication number Publication date
JPH0644893A (ja) 1994-02-18
GB9210419D0 (en) 1992-07-01
GB9309727D0 (en) 1993-06-23
GB2267176A (en) 1993-11-24

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