EP0726590B1 - Herstellungsverfahren einer Feldemissionskaltkathode - Google Patents

Herstellungsverfahren einer Feldemissionskaltkathode Download PDF

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Publication number
EP0726590B1
EP0726590B1 EP96102013A EP96102013A EP0726590B1 EP 0726590 B1 EP0726590 B1 EP 0726590B1 EP 96102013 A EP96102013 A EP 96102013A EP 96102013 A EP96102013 A EP 96102013A EP 0726590 B1 EP0726590 B1 EP 0726590B1
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EP
European Patent Office
Prior art keywords
cone
refractory metal
silicon
field emission
oxidation
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.)
Expired - Lifetime
Application number
EP96102013A
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English (en)
French (fr)
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EP0726590A3 (de
EP0726590A2 (de
Inventor
Toshio Kaihara
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NEC Corp
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NEC Corp
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Publication of EP0726590A3 publication Critical patent/EP0726590A3/de
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    • 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
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/30—Cold cathodes, e.g. field-emissive cathode
    • H01J1/304—Field-emissive cathodes
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2209/00—Apparatus and processes for manufacture of discharge tubes
    • H01J2209/02—Manufacture of cathodes
    • H01J2209/022—Cold cathodes
    • H01J2209/0223—Field emission cathodes
    • H01J2209/0226—Sharpening or resharpening of emitting point or edge

Definitions

  • the invention relates to a method for forming a field emission cold cathode, and more particularly to a method for forming a cone-shaped field emission cold cathode having a top which is sharply pointed for improvements of emission properties.
  • Gate electrodes 15 made of a refractory metal such as tungsten, molybdenum, tantalum and niobium are formed on the insulation film 14.
  • the gate electrodes 15 have the same level as the top of each of the cone-shaped field emission cold cathodes 12.
  • the gate electrode 15 encompasses and is separated from the top portion of each the cone-shaped field emission cold cathodes 12.
  • a bias is applied at a few voltages between the gate electrode. 15 and the cone-shaped field emission cold cathode 12 so as to cause electron emission from the top of each the cone-shaped field emission cold cathodes 12 without heating the cathodes 12.
  • FIG. 2A A conventional method for forming a cone-shaped field emission cold cathode of Spindt type will be described with reference to FIGS. 2A through 2E.
  • a silicon oxide film 14A having a thickness of 1 micrometers is formed on a silicon substrate 11 by a chemical vapor deposition.
  • a gate layer 15A is deposited on the silicon oxide film 14A.
  • the gate layer 15A has a thickness of 0.4 micrometers and is made of a refractory metal such as tungsten, molybdenum, tantalum and niobium.
  • a photo-resist film 16 is applied on the gate layer 15A.
  • holes 16a having a diameter of 1 micrometer are formed in the photo-resist film 16 at a pitch of 10 micrometers.
  • the gate layer 15A and the silicon oxide film 14A are selectively etched using the photo-resist film 16 to thereby form an insulator 14 having a cavity 13 and a gate electrode 15.
  • the photo-resist film 16 used is then removed.
  • refractory metal atoms such as tungsten, molybdenum, tantalum and niobium are deposited in a vertical direction to the surface of the silicon substrate 11 whereby a refractory metal cone 12 is formed in the cavity 13 and further a refractory metal layer 18 is deposited on the aluminum film 17.
  • the refractory metal layer 18 has a concave portion being cone-shaped and posited over the opening 15a.
  • the refractory metal layer 18 and the aluminum film 17 are removed to expose the gate electrode 15 on the silicon oxide film 14 and the refractory metal cone 12 within the cavity 13.
  • the refractory metal cone 12 serves as a cone-shaped cathode.
  • the cone 12 is formed by the vertical deposition of refractory metal atoms while the aluminum film 17 is formed by the deposition of aluminum at the oblique angle.
  • the deposition at the oblique angle of aluminum on the gate electrode 15 tends to cause a small variation in the shape and the position of the opening edge of the aluminum film 17.
  • the shape of the cone 12 depends upon the shape and the position of the opening edge of the aluminum film 17. Any small variation in the shape or the position of the opening edge of the aluminum film 17 results in a considerable variation in the shape of the cone 12, particularly the top shape thereof.
  • the top shape of the cone 12 serving as the cathode is extremely influential.
  • any slight deformation of the top of the cone 12 results in a considerable deterioration of the electron emission properties. This may result in a reduction in the yield of the field emission electron gun having the cone-shaped field emission cold cathode.
  • the oxide film which coats the refractory metal cone is selectively etched using the lift-off process using a fluorine acid so that the top portion of the refractory cone is exposed. If the lift-off process is used with a fluorine acid to selectively remove the oxide film covering the top of the cone, then the top of the refractory metal cone is likely deformed from the desirable top shape which is sharply pointed. Any small variation in the shape or the position of the opening edge of the aluminum film 17 results in a considerable variation in the shape of the cone 12, particularly the top shape thereof. For the emission properties, the top shape of the cone 12 serving as the cathode is extremely influential. Any slight deformation of the top of the cone results in a considerable deterioration of the electron emission properties.
  • FR-A-2 700 222 discloses sharpening a Si cone by oxidising the surface of the cone.
  • the present invention provides a method for forming a cone-shaped field emission cold cathode on a substrate.
  • the method comprises the following steps.
  • a silicon oxide layer is deposited by a chemical vapor deposition on the substrate.
  • a gate layer made of a refractory metal is deposited on the silicon oxide layer.
  • a photo-resist pattern is provided on the gate layer .
  • the gate layer and the silicon oxide layer are selectively etched by using the photo-resist pattern as a mask to form a cavity having an opening.
  • a surface of the silicon containing refractory metal cone is subjected to an oxidation of silicon which is contained in the refractory metal.
  • the oxidation has rates which increase toward a top portion of the silicon containing refractory metal cone, to thereby form a silicon oxide film which coats the silicon containing refractory metal cone.
  • An interface between the silicon oxide film and the silicon containing refractory metal cone has sloped angles which increase toward the top portion.
  • the silicon oxide film is removed to expose a reshaped silicon containing refractory metal cone which has a sharply pointed top.
  • the reshaped silicon containing refractory metal cone has a surface having sloped angles which increase toward the sharply pointed top.
  • the present invention provides a method for reshaping up a cone-like electrode which is made of a refractory metal containing silicon.
  • the method comprises the following steps. A surface of the cone-like electrode is subjected to an oxidation of silicon which is contained in the refractory metal. The oxidation is generated at rates which increase toward a top portion of the cone-like electrode. As a result, a silicon oxide film is formed, which coats the cone-like electrode. An interface between the silicon oxide film and the cone-like electrode has sloped angles which increase toward the top portion. The silicon oxide film is removed to thereby expose a reshaped cone electrode which has a sharply pointed top. The reshaped cone electrode has a surface having sloped angles which increase toward the sharply pointed top.
  • the above oxidation of the surface of the cone-shaped field emission cold cathode for reshaping the same results in that the refractory metal content in the unoxidized part of the cone-shaped field emission cold cathode is increased and the silicon content therein is decreased.
  • This results in the reshaped field emission cold cathode is made of the refractory metal having a lower silicon content.
  • This refractory metal having a lower silicon content has a relatively low work function which permits the desirable electron emission properties.
  • the oxidation may be carried out in a dried or steamed atmosphere.
  • the silicon oxide film may be removed by a diluted fluorine acid solution.
  • the refractory metal has a silicon content in the range of 1-10%.
  • the refractory metal may be one selected from the group consisting of tungsten, molybdenum, tantalum and niobium.
  • the present invention provides a method for forming a cone-shaped field emission cold cathode on a substrate.
  • the method comprises the following steps.
  • a silicon oxide layer is deposited by a chemical vapor deposition on the substrate.
  • a gate layer made of a refractory metal is deposited on the silicon oxide layer.
  • a photo-resist pattern is provided on the gate layer .
  • the gate layer and the silicon oxide layer are selectively etched by using the photo-resist pattern as a mask to form a cavity having an opening.
  • a metal material is deposited on the gate layer during which the substrate rotates in a plane parallel to a surface of the substrate at a predetermined oblique angle to the plane to thereby form a metal film having an opening edge which extends toward a center of the opening from an edge of the gate layer.
  • a silicon containing refractory metal material containing silicon is deposited on the metal film and within the cavity in a vertical direction to a surface of the substrate to thereby form a silicon containing refractory metal cone in the cavity and further to form a refractory metal layer on the metal film. The refractory metal layer and the metal film are removed to expose the silicon containing refractory metal cone.
  • a surface of the silicon containing refractory metal cone is subjected to an oxidation of silicon which is contained in the refractory metal.
  • the oxidation has rates which increase toward a top portion of the silicon containing refractory metal cone, to thereby form a silicon oxide film which coats the silicon containing refractory metal cone.
  • An interface between the silicon oxide film and the silicon containing refractory metal cone has sloped angles which increase toward the top portion.
  • the silicon oxide film is removed to expose a reshaped silicon containing refractory metal cone which has a sharply pointed top.
  • the reshaped silicon containing refractory metal cone has a surface having sloped angles which increase toward the sharply pointed top.
  • the refractory metal which contains silicon allows the oxidation of the surface of the silicon containing refractory metal cone electrode.
  • the oxidation of the surface of the silicon containing refractory metal cone electrode is carried out to reshape the silicon containing refractory metal cone electrode.
  • the oxidation process for reshaping the silicon containing refractory metal cone electrode results in a desired shape of the electrode having both a sharply pointed top and a surface which increase in the sloped angle toward the top portion thereof.
  • the oxidation of the surface of the silicon containing refractory metal cone electrode reshapes it, thereby resulting in the desired shape of the cone electrode having both a sharply pointed top and a surface which increase in the sloped angle toward the top portion thereof.
  • This may result in a high yield of the field emission electron gun having the cone-shaped field emission cold cathode.
  • the cone-shaped field emission cold cathode has a sharply pointed top portion without any variation in the shape.
  • the cone-shaped field emission cold cathode also has a surface which is curved to increase the sloped angle toward the top portion.
  • the top portion sharply pointed is suitable for obtaining stable and desirable electron emission.
  • the above oxidation of the surface of the cone-shaped field emission cold cathode for reshaping the same results in that the refractory metal content in the unoxidized part of the cone-shaped field emission cold cathode is increased and the silicon content therein is decreased.
  • This results in the reshaped field emission cold cathode is made of the refractory metal having a lower silicon content.
  • This refractory metal having a lower silicon content has a relatively low work function which permits the desirable electron emission properties.
  • FIGS. 3A through 3G A preferred embodiment according to the present invention will be described with reference to FIGS. 3A through 3G, wherein there is provided a novel method for forming a field emission cold cathode having a top sharply pointed without any deformation.
  • a silicon oxide film 5A having a thickness of 1 micrometer is deposited by a chemical vapor deposition on a silicon substrate 2.
  • a gate layer 6A having a thickness of 0.4 micrometers and being made of a refractory metal such as tungsten and molybdenum is deposited on the silicon oxide film 5A.
  • a photo-resist film is applied on the gate layer 6A. Holes having a diameter of 1 micrometer are formed at a pitch of 10 micrometers.
  • the gate layer 6A and the silicon oxide film 5A are sequentially and selectively etched using the photo-resist film 6 having the holes as a mask to thereby form a silicon oxide film 5A which has a cavity 4 and a gate electrode 5 having an opening.
  • the silicon substrate 2 is rotated in a plane parallel to the surface of the silicon substrate 2, during which aluminum is deposited at an oblique angle of 15 degrees to the surface of the silicon substrate 2 to thereby form an aluminum film having a thickness of 0.15 micrometers.
  • the aluminum film has an opening edge extending toward the center of the opening from the edge of the gate electrode 5 thereby making the opening of the gate electrode 5 narrow.
  • a refractory metal such as tungsten, molybdenum, tantalum and niobium is prepared, which contains silicon, wherein the content of silicon is in the range of 1-10%.
  • the silicon containing refractory metal is deposited in a vertical direction to the surface of the silicon substrate 2.
  • a silicon containing refractory metal cone 3 is formed in the cavity 4 and further a refractory metal layer 8 is deposited on the aluminum film 7.
  • the refractory metal layer 8 has a concave portion being cone-shaped and posited over the opening of the gate electrode and over the cavity 4.
  • the refractory metal layer 8 and the aluminum film 7 are removed to expose the gate electrode 15 on the silicon oxide film 5 and the silicon containing refractory metal cone 3 within the cavity 4.
  • the refractory metal cone 3 serves as a cone-shaped cathode.
  • the silicon containing refractory metal cone 3 is subjected to an oxidation of silicon contained in the refractory metal cone 3 in a dried or steamed atmosphere to thereby form a silicon oxide film 9 on a surface of the silicon containing refractory metal cone 3.
  • the rate of oxidation of the surface of the silicon containing refractory metal cone 3 is different between the top portion and the bottom portion. Since the bottom portion of the silicon containing refractory metal cone 3 has a larger volume than the top portion, the rate of the oxidation at the bottom portion is lower than the top portion. As a result, the silicon oxide film on the top portion of the silicon containing refractory metal cone 3 has a larger thickness than the bottom portion thereof.
  • the sloped angle of the interface between the silicon oxide film 9 and the silicon containing refractory metal cone 3 increases toward the top portion thereof.
  • the silicon oxidation increases the content of the refractory metal and decreases the silicon content.
  • the silicon oxide film 9 is removed by using a diluted fluorine acid solution to thereby expose silicon containing refractory metal cone 3 having a reshaped surface which has a sloped angle increasing toward the top portion thereof.
  • the top of the silicon containing refractory metal cone 3 illustrated in FIG. 3G is more sharply pointed, than that illustrated in FIG. 3E.
  • FIGS. 3A through 3E are the same as the conventional processes illustrated in FIGS. 2A through 2E except in that the cone 3 is made of the silicon containing refractory metal.
  • the refractory metal which contains silicon allows the oxidation of the surface of the cone in the process illustrated in FIG. 3F.
  • the oxidation of the surface of the silicon containing refractory metal cone 3 is carried out to reshape up the silicon containing refractory metal cone 3.
  • the oxidation process for reshaping the silicon containing refractory metal cone 3 results in a desired shape of the cathode 3 having both a sharply pointed top and a surface which increase in the sloped angle toward the top portion thereof.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Cold Cathode And The Manufacture (AREA)

Claims (6)

  1. Verfahren zur Herstellung einer Feldemissionskaltkathode, welche aus einem Silizium aufweisenden temperaturbeständigen Metall hergestellt ist, durch Umformen einer konusförmigen Elektrode, wobei das Verfahren dadurch gekennzeichnet ist, daß:
    die Oberfläche der konusförmigen Elektrode (3) einer Oxidation des Siliziums, welches im temperaturbeständigen Metall enthalten ist, ausgesetzt ist, wobei die Oxidationsrate zum oberen Ende der konusförmigen Elektrode (3) hin zunimmt und sich dabei ein Siliziumoxid-Film (9) ausbildet, welcher die konusförmige Elektrode (3) überzieht, wobei die Übergangsfläche zwischen dem Siliziumoxid-Film (9) und der konusförmigen Elektrode (3) Neigungswinkel aufweist, welche zum oberen Ende dieser hin zunehmen; und
    der Siliziumoxid-Film (9) entfernt wird und somit eine umgeformte konusförmige Elektrode (3) freigelegt wird, welche ein spitz zulaufendes oberes Ende aufweist, wobei die umgeformte konusförmige Elektrode (3) eine Oberfläche mit Neigungswinkeln, welche zum Ende des spitz zulaufenden oberen Endes hin zunehmen, aufweist.
  2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die Oxidation in Trockenatmosphäre durchgeführt wird.
  3. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die Oxidation in Dampf atmosphäre durchgeführt wird.
  4. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß der Siliziumoxid-Film (7) mit Hilfe einer wässrigen Fluoursäure-Lösung entfernt wird.
  5. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß das temperaturbeständige Metall einen Siliziumanteil im Bereich von 1 bis 10 % aufweist.
  6. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß das temperaturbeständige Metall aus der Gruppe ausgewählt wird, welche Wolfram, Molybdän, Tantal oder Niob aufweist.
EP96102013A 1995-02-13 1996-02-12 Herstellungsverfahren einer Feldemissionskaltkathode Expired - Lifetime EP0726590B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP23582/95 1995-02-13
JP2358295A JPH08222126A (ja) 1995-02-13 1995-02-13 電界放出冷陰極の製造方法

Publications (3)

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EP0726590A2 EP0726590A2 (de) 1996-08-14
EP0726590A3 EP0726590A3 (de) 1996-12-11
EP0726590B1 true EP0726590B1 (de) 1999-04-07

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EP96102013A Expired - Lifetime EP0726590B1 (de) 1995-02-13 1996-02-12 Herstellungsverfahren einer Feldemissionskaltkathode

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JP (1) JPH08222126A (de)
KR (1) KR0181326B1 (de)
DE (1) DE69601961T2 (de)

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4855636A (en) * 1987-10-08 1989-08-08 Busta Heinz H Micromachined cold cathode vacuum tube device and method of making
US5201992A (en) * 1990-07-12 1993-04-13 Bell Communications Research, Inc. Method for making tapered microminiature silicon structures
US5332627A (en) * 1990-10-30 1994-07-26 Sony Corporation Field emission type emitter and a method of manufacturing thereof
JP2550798B2 (ja) * 1991-04-12 1996-11-06 富士通株式会社 微小冷陰極の製造方法
KR960009127B1 (en) * 1993-01-06 1996-07-13 Samsung Display Devices Co Ltd Silicon field emission emitter and the manufacturing method

Also Published As

Publication number Publication date
EP0726590A3 (de) 1996-12-11
DE69601961D1 (de) 1999-05-12
JPH08222126A (ja) 1996-08-30
KR960032553A (ko) 1996-09-17
EP0726590A2 (de) 1996-08-14
KR0181326B1 (ko) 1999-03-20
DE69601961T2 (de) 1999-10-14

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