EP0616356A1 - Micropoint display device and method of fabrication - Google Patents

Micropoint display device and method of fabrication Download PDF

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Publication number
EP0616356A1
EP0616356A1 EP94400562A EP94400562A EP0616356A1 EP 0616356 A1 EP0616356 A1 EP 0616356A1 EP 94400562 A EP94400562 A EP 94400562A EP 94400562 A EP94400562 A EP 94400562A EP 0616356 A1 EP0616356 A1 EP 0616356A1
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EP
European Patent Office
Prior art keywords
layer
grids
microtips
electrically insulating
thin
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EP94400562A
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German (de)
French (fr)
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EP0616356B1 (en
Inventor
Robert Meyer
Michel Borel
Brigitte Montmayeul
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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
    • H01J3/00—Details of electron-optical or ion-optical arrangements or of ion traps common to two or more basic types of discharge tubes or lamps
    • H01J3/02—Electron guns
    • H01J3/021—Electron guns using a field emission, photo emission, or secondary emission electron source
    • H01J3/022—Electron guns using a field emission, photo emission, or secondary emission electron source with microengineered cathode, e.g. Spindt-type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/10—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes
    • H01J31/12—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes with luminescent screen
    • H01J31/123—Flat display tubes
    • H01J31/125—Flat display tubes provided with control means permitting the electron beam to reach selected parts of the screen, e.g. digital selection
    • H01J31/127—Flat display tubes provided with control means permitting the electron beam to reach selected parts of the screen, e.g. digital selection using large area or array sources, i.e. essentially a source for each pixel group
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2329/00—Electron emission display panels, e.g. field emission display panels
    • H01J2329/86—Vessels
    • H01J2329/8625—Spacing members
    • H01J2329/863—Spacing members characterised by the form or structure

Definitions

  • the present invention relates to a microtip display device and a method of manufacturing this device.
  • a microtip display device comprises a source of electrons with microtip emissive cathodes and a cathodoluminescent anode comprising a layer of cathodoluminescent material and placed opposite the source of electrons with emissive microtip cathodes which is more simply called "cathode”.
  • detachment of powder, local degassing, an electrically charged spacer can trigger a regime of electric arc between the anode and the cathode, which results in the destruction of the display device over a more or less large area.
  • This arc regime phenomenon is all the more likely to occur when the anode voltage which is applied is high and the distance between the anode and the cathode is small.
  • microtip sources include parallel cathode conductors and grids which are parallel and form an angle with the cathode conductors.
  • These grids are generally metallic and, in the event of a short circuit or an arc regime between the cathodoluminescent anode and the microtip source of a device, nothing limits the electric current between the anode and the grids and the device. then risks being destroyed.
  • the object of the present invention is to remedy this drawback.
  • the means capable of avoiding the disturbance of the electric field comprise another thin layer which covers said thin insulating layer and which is sufficiently conductive to allow the flow of parasitic electrical charges which may be created during the operation of the device and which also has holes opposite the microtips.
  • This other thin layer which has an electrical conductivity sufficient to allow the flow of charges can be conductive but, preferably, it is resistive to allow only this flow.
  • the total thickness of the thin layer or layers formed on the grids can be for example between a few tens of nanometers and a few hundred nanometers.
  • the diameter of the holes formed in said thin insulating layer is greater than the diameter of the holes formed in the grids to avoid disturbance of the electric field created between the microtips and the grids, this thin insulating layer thus being over-etched.
  • said thin insulating layer can be over-etched and / or covered with the layer sufficiently conductive to allow the flow of parasitic electrical charges.
  • the device which is the subject of the invention may comprise, on the grids, a thin insulating layer, for example made of silica or silicon nitride, and a resistive layer, for example made of resistive silicon or of SnO2.
  • a thin insulating layer for example made of silica or silicon nitride
  • a resistive layer for example made of resistive silicon or of SnO2.
  • this device also comprises a resistive layer which is interposed between each cathode conductor and the corresponding microtips, the latter thus resting on this resistive layer.
  • Such a resistive layer is of the kind described in documents (2) and (3) mentioned above.
  • the present invention also relates to a method of manufacturing the microtip display device which is also the subject of the invention, method according to which said cathodoluminescent anode is formed on the first substrate, and the cathode conductors, said electrically insulating layer, a grid layer intended for forming the grids, the holes and then the microtips, this process being characterized in that said thin electrically insulating layer is further formed on the grid layer and in that said electrically insulating thin layer is associated with means capable of avoiding the disturbance, by this electrically insulating thin layer, of the electric field created between the microtips and the grids.
  • the grid layer is etched to form the grids, advantageously before the holes and the thin layer are formed.
  • said thin electrically insulating layer is formed before the holes.
  • This other thin layer which is sufficiently conductive to allow the flow of parasitic electrical charges, can be formed before or advantageously after the step of forming the holes.
  • a protective layer can be formed on said thin electrically insulating layer either directly or over said other thin layer sufficiently conductive to allow the flow of charges when it exists.
  • This protective layer can be deposited before or advantageously after the holes have been formed.
  • This protective layer can be removed by etching after the step of forming the microtips.
  • this protective layer is not removed or is only partially removed after the step of forming the microtips.
  • the layer or layers formed over the grids, which are resistive or conductive, can be deposited after the holes have been made.
  • This known device comprises a cathodoluminescent anode formed on a glass substrate 2 and comprising a conductive and transparent layer 4, for example made of ITO and, on this layer 4, a layer 6 of luminescent powder.
  • the device of FIG. 1 also comprises a source of microtip electrons formed on another insulating substrate 8 and comprising cathode conductors such as the conductor 10, a layer insulating 12 formed on these cathode conductors and grids such as the grid 14, formed on the insulating layer 12 and perpendicular to the cathode conductors 10.
  • a source of microtip electrons formed on another insulating substrate 8 and comprising cathode conductors such as the conductor 10, a layer insulating 12 formed on these cathode conductors and grids such as the grid 14, formed on the insulating layer 12 and perpendicular to the cathode conductors 10.
  • Microtips such as microtip 16 are formed on the latter, in holes 17 made in the grids and the insulating layer 12.
  • spacers such as the spacer 18 are disposed between the cathodoluminescent anode and the grids to maintain the rigidity of the device when a vacuum is created between the cathodoluminescent anode and the source of microtip electrons.
  • Such a device is extremely sensitive to short circuits, very unstable and difficult to control.
  • the device according to the invention differs from the device in FIG. 1 in that it further comprises an electrically insulating layer 20, formed on the grids and pierced opposite the microtips. , this layer 20 being provided to limit the current between the anode and the grids.
  • the device of FIG. 2 also comprises a layer 21 which covers the layer 20 and which is sufficiently conductive to allow the flow of parasitic electrical charges likely to be created during the operation of the device and which also has holes facing the microtips. .
  • This layer 21 avoids the disturbance, by layer 20, of the electric field created between the microtips and the grids when the device is operating.
  • the layer 21 does not exist and, to avoid disturbance of the electric field, the diameter of the holes formed in the layer 20 is greater than that of the holes formed in the grids.
  • the invention is preferably applied to microtip display devices whose electron source comprises a resistive layer between the cathode conductors and the microtips which rest on this resistive layer.
  • Figure 3 is a schematic and partial view of a device according to the invention which comprises such a resistive layer between the cathode conductors and the microtips.
  • This device of Figure 3 differs from the device of Figure 2 in that it comprises in addition a resistive layer 22 between the insulating layer 12 and the cathode conductors 24 which are here meshed as in document (3).
  • the device is thus protected against any risk of short circuit.
  • the most important advantage of the invention is that it makes it possible to increase the anode voltage and, possibly, to decrease the space between the anode and the source of microtip electrons without risk of electrical accident liable to destroy the device.
  • an insulating layer 26 of silica (FIG. 4) is deposited on the grids.
  • the thickness of this layer 26 is for example equal to 0.2 ⁇ m.
  • This layer 26 can be produced by chemical vapor deposition, by sputtering or by any other method of depositing thin layers.
  • This layer 28 is for example equal to 50 nm.
  • This layer 28 is preferably formed by evaporation by means of an electron gun or by spraying.
  • holes the diameter of which is of the order of 1.4 ⁇ m, are etched in the thin conductive layer 28, the insulating layer 12, the grid layer 14 and insulating layer 26, inside the mesh of the conductors cathodic, or more exactly plumb with the domains delimited by these meshes.
  • a wet etching process or a dry etching process can be used.
  • a reactive ion etching process is used to etch the metal layers and the insulating layers.
  • a chemical over-etching of the silica of the layer 12 is carried out, this over-etching being for example a few hundred nanometers (length e in FIG. 4), which makes it possible to enlarge the holes at the level of this layer 12.
  • an over-etching of the layer 26 is carried out in order to allow the grids to be released around the holes 30 and therefore to avoid a disturbance of the electric field (during operation of the device) between the microtips 16 and the grids, this disturbance being caused by a charging phenomenon of the insulating layer 26.
  • microtips 16 are then produced according to the method described in the document (1) mentioned above.
  • the contact points for the row conductors and the column conductors are released if necessary.
  • the thin conductive layer 28 can optionally be removed by appropriate etching.
  • the thin conductive layer (sufficiently conductive to allow the flow of charges) can be deposited after etching the holes, in which case the bottom of the holes is covered by this layer.
  • FIG. 5 schematically and partially illustrates this case where the thin conductive layer 28 is deposited after etching the holes and it can be seen that the bottom of the holes is covered by this fine conductive layer 28 (which covers the insulating layer 26 of silica already mentioned in the description of Figure 4).
  • microtips 16 are thus above the thin conductive layer.
  • the deposition of the thin conductive layer, after etching the holes, makes it possible to avoid etching of this layer.

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  • Cold Cathode And The Manufacture (AREA)
  • Electrodes For Cathode-Ray Tubes (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)

Abstract

According to the invention, a cathodoluminescent anode (4, 6) is formed on an insulating substrate (2), and cathodic conductors (10), an insulating layer (12), a gate layer (14) intended for forming gates, holes (17) in the insulating layer and the gate layer, and micropoints (16) in these holes are formed on another insulating substrate (8). In addition, an insulating thin film (20) is formed on the gate layer, in order to limit the current which can flow between the anode and the gates. This thin film is associated with means (21) capable of preventing this electrically insulating thin film from disturbing the electric field created between the micropoints and the gates. Application to flat screens. <IMAGE>

Description

La présente invention concerne un dispositif d'affichage à micropointes ("microtip display device") et un procédé de fabrication de ce dispositif.The present invention relates to a microtip display device and a method of manufacturing this device.

Elle s'applique notamment au domaine de la visualisation et, plus particulièrement, aux écrans plats.It applies in particular to the field of visualization and, more particularly, to flat screens.

On connaît déjà des dispositifs d'affichage à micropointes par les documents suivants, auxquels on se reportera :

  • (1) Demande de brevet français n° 8601024 du 24 Janvier 1986, correspondant à EP-A-0234989 et à US-A-4,857,161
  • (2) Demande de brevet français n° 8715432 du 6 novembre 1987, correspondant à US-A-4,940,916
  • (3) Demande de brevet français n° 9007347 du 13 juin 1990, correspondant à EP-A-0461990.
Microtip display devices are already known from the following documents, to which reference will be made:
  • (1) French patent application No. 8601024 of January 24, 1986, corresponding to EP-A-0234989 and US-A-4,857,161
  • (2) French patent application n ° 8715432 of November 6, 1987, corresponding to US-A-4,940,916
  • (3) French patent application no. 9007347 of June 13, 1990, corresponding to EP-A-0461990.

Un dispositif d'affichage à micropointes comprend une source d'électrons à cathodes émissives à micropointes et une anode cathodoluminescente comportant une couche d'un matériau cathodoluminescent et placée en regard de la source d'électrons à cathodes émissives à micropointes qui est plus simplement appelée "cathode".A microtip display device comprises a source of electrons with microtip emissive cathodes and a cathodoluminescent anode comprising a layer of cathodoluminescent material and placed opposite the source of electrons with emissive microtip cathodes which is more simply called "cathode".

Des défauts d'isolation électrique sont susceptibles d'apparaître entre cette cathode et l'anode cathodoluminescente pour les raisons suivantes :

  • 1) La distance entre cette anode et la cathode est faible (quelques dizaines à quelques centaines de µm, typiquement 200 µm).
  • 2) Le matériau cathodoluminescent de l'anode est généralement sous forme de poudre dont l'adhérence est incertaine.
  • 3) Des espaceurs sont disposés entre l'anode et la cathode pour maintenir la rigidité du dispositif d'affichage au moment où le vide est fait dans celui-ci ; ces espaceurs sont préférentiellement sous forme de billes électriquement isolantes ; ces espaceurs sont susceptibles de constituer des points faibles vis-à-vis de l'isolation électrique.
Electrical insulation faults are likely to appear between this cathode and the cathodoluminescent anode for the following reasons:
  • 1) The distance between this anode and the cathode is small (a few tens to a few hundred microns, typically 200 microns).
  • 2) The cathodoluminescent material of the anode is generally in the form of powder whose adhesion is uncertain.
  • 3) Spacers are arranged between the anode and the cathode to maintain the rigidity of the display device when the vacuum is created therein; these spacers are preferably in the form of electrically insulating balls; these spacers are likely to constitute weak points vis-à-vis the electrical insulation.

En particulier, un décollement de poudre, un dégazage local, un espaceur électriquement chargé peuvent déclencher un régime d'arc électrique entre l'anode et la cathode, qui entraîne la destruction du dispositif d'affichage sur une zone plus ou moins étendue.In particular, detachment of powder, local degassing, an electrically charged spacer can trigger a regime of electric arc between the anode and the cathode, which results in the destruction of the display device over a more or less large area.

Ce phénomène de régime d'arc est d'autant plus susceptible de se produire que la tension d'anode qui est appliquée est forte et que la distance entre l'anode et la cathode est faible.This arc regime phenomenon is all the more likely to occur when the anode voltage which is applied is high and the distance between the anode and the cathode is small.

Or, pour améliorer les performances du dispositif d'affichage, il est précisément souhaitable d'augmenter cette tension d'anode (pour augmenter la brillance de l'écran du dispositif) et de diminuer l'espace entre l'anode et la cathode (pour pouvoir utiliser des espaceurs plus petits et donc moins visibles et/ou pour améliorer la résolution).However, to improve the performance of the display device, it is precisely desirable to increase this anode voltage (to increase the brightness of the screen of the device) and to decrease the space between the anode and the cathode ( to be able to use smaller spacers and therefore less visible and / or to improve the resolution).

Dans les dispositifs connus d'affichage à micropointes, les sources à micropointes comprennent des conducteurs cathodiques parallèles et des grilles qui sont parallèles et font un angle avec les conducteurs cathodiques.In known microtip display devices, microtip sources include parallel cathode conductors and grids which are parallel and form an angle with the cathode conductors.

Ces grilles sont généralement métalliques et, en cas de court-circuit ou de régime d'arc entre l'anode cathodoluminescente et la source à micropointes d'un dispositif, rien ne limite le courant électrique entre l'anode et les grilles et le dispositif risque alors d'être détruit.These grids are generally metallic and, in the event of a short circuit or an arc regime between the cathodoluminescent anode and the microtip source of a device, nothing limits the electric current between the anode and the grids and the device. then risks being destroyed.

La présente invention a pour but de remédier à cet inconvénient.The object of the present invention is to remedy this drawback.

Elle a tout d'abord pour objet un dispositif d'affichage à micropointes, ce dispositif comprenant un premier substrat électriquement isolant portant une anode cathodoluminescente et un deuxième substrat électriquement isolant portant, en regard du premier substrat :

  • une première série d'électrodes parallèles jouant le rôle de conducteurs cathodiques et portant des micropointes ("microtips") en matériau émetteur d'électrons,
  • une couche électriquement isolante sur ces conducteurs cathodiques,
  • une deuxième série d'électrodes parallèles jouant le rôle de grilles, placées sur cette couche isolante et faisant un angle avec les conducteurs cathodiques, des trous étant formés dans la couche isolante et les grilles pour le passage des micropointes,

ce dispositif étant caractérisé en ce qu'il comprend en outre, sur les grilles, une couche mince électriquement isolante, pour limiter le courant électrique susceptible de circuler entre l'anode cathodoluminescente et les grilles et empêcher la survenance d'un arc électrique entre cette anode et ces grilles, cette couche mince comportant aussi des trous en regard des micropointes, et en ce que ladite couche mince électriquement isolante est associée à des moyens aptes à éviter la perturbation, par cette couche mince électriquement isolante, du champ électrique créé entre les micropointes et les grilles.It firstly relates to a microtip display device, this device comprising a first electrically insulating substrate carrying a cathodoluminescent anode and a second electrically insulating substrate carrying, opposite the first substrate:
  • a first series of parallel electrodes acting as cathode conductors and carrying microtips ("microtips") made of electron emitting material,
  • an electrically insulating layer on these cathode conductors,
  • a second series of parallel electrodes acting as grids, placed on this insulating layer and at an angle with the cathode conductors, holes being formed in the insulating layer and the grids for the passage of the microtips,

this device being characterized in that it further comprises, on the grids, an electrically insulating thin layer, in order to limit the electric current capable of flowing between the cathodoluminescent anode and the grids and prevent the occurrence of an electric arc between this anode and these grids, this thin layer also comprising holes opposite the microtips, and in that said electrically insulating thin layer is associated with means capable of avoiding disturbance, by this electrically insulating thin layer, of the electric field created between the microtips and the grids.

L'utilisation d'une telle couche mince sur les grilles du dispositif permet de diminuer fortement les risques de mauvais fonctionnement de ce dernier même en cas de défaut de nature électrique.The use of such a thin layer on the grids of the device makes it possible to greatly reduce the risks of the latter malfunctioning even in the event of an electrical fault.

De préférence, les moyens aptes à éviter la perturbation du champ électrique comprennent une autre couche mince qui recouvre ladite couche mince isolante et qui est suffisamment conductrice pour permettre l'écoulement de charges électriques parasites susceptibles d'être créées pendant le fonctionnement du dispositif et qui comporte aussi des trous en regard des micropointes.Preferably, the means capable of avoiding the disturbance of the electric field comprise another thin layer which covers said thin insulating layer and which is sufficiently conductive to allow the flow of parasitic electrical charges which may be created during the operation of the device and which also has holes opposite the microtips.

Cette autre couche mince qui présente une conductivité électrique suffisante pour permettre l'écoulement des charges peut être conductrice mais, de préférence, elle est résistive pour permettre seulement cet écoulement.This other thin layer which has an electrical conductivity sufficient to allow the flow of charges can be conductive but, preferably, it is resistive to allow only this flow.

L'épaisseur totale de la ou des couches minces formées sur les grilles peut être comprise par exemple entre quelques dizaines de nanomètres et quelques centaines de nanomètres.The total thickness of the thin layer or layers formed on the grids can be for example between a few tens of nanometers and a few hundred nanometers.

De préférence également, le diamètre des trous formés dans ladite couche mince isolante est supérieur au diamètre des trous formés dans les grilles pour éviter la perturbation du champ électrique créé entre les micropointes et les grilles, cette couche mince isolante étant ainsi surgravée.Preferably also, the diameter of the holes formed in said thin insulating layer is greater than the diameter of the holes formed in the grids to avoid disturbance of the electric field created between the microtips and the grids, this thin insulating layer thus being over-etched.

Ainsi, ladite couche mince isolante peut être surgravée et/ou recouverte de la couche suffisamment conductrice pour permettre l'écoulement de charges électriques parasites.Thus, said thin insulating layer can be over-etched and / or covered with the layer sufficiently conductive to allow the flow of parasitic electrical charges.

Ceci permet d'éviter l'accumulation de charges parasites au voisinage des micropointes pendant le fonctionnement du dispositif.This avoids the accumulation of parasitic charges in the vicinity of the microtips during the operation of the device.

Le dispositif objet de l'invention peut comporter, sur les grilles, une couche mince isolante, par exemple en silice ou en nitrure de silicium, et une couche résistive, par exemple en silicium résistif ou en SnO₂.The device which is the subject of the invention may comprise, on the grids, a thin insulating layer, for example made of silica or silicon nitride, and a resistive layer, for example made of resistive silicon or of SnO₂.

Selon un mode de réalisation préféré du dispositif objet de l'invention, ce dispositif comprend en outre une couche résistive qui est interposée entre chaque conducteur cathodique et les micropointes correspondantes, ces dernières reposant ainsi sur cette couche résistive.According to a preferred embodiment of the device which is the subject of the invention, this device also comprises a resistive layer which is interposed between each cathode conductor and the corresponding microtips, the latter thus resting on this resistive layer.

Une telle couche résistive est du genre de celles qui sont décrites dans les documents (2) et (3) mentionnés plus haut.Such a resistive layer is of the kind described in documents (2) and (3) mentioned above.

La présente invention a également pour objet un procédé de fabrication du dispositif d'affichage à micropointes qui fait également l'objet de l'invention, procédé selon lequel on forme ladite anode cathodoluminescente sur le premier substrat, et on forme sur le deuxième substrat les conducteurs cathodiques, ladite couche électriquement isolante, une couche de grille destinée à la formation des grilles, les trous puis les micropointes, ce procédé étant caractérisé en ce qu'on forme en outre ladite couche mince électriquement isolante sur la couche de grille et en ce que ladite couche mince électriquement isolante est associée à des moyens aptes à éviter la perturbation, par cette couche mince électriquement isolante, du champ électrique créé entre les micropointes et les grilles.The present invention also relates to a method of manufacturing the microtip display device which is also the subject of the invention, method according to which said cathodoluminescent anode is formed on the first substrate, and the cathode conductors, said electrically insulating layer, a grid layer intended for forming the grids, the holes and then the microtips, this process being characterized in that said thin electrically insulating layer is further formed on the grid layer and in that said electrically insulating thin layer is associated with means capable of avoiding the disturbance, by this electrically insulating thin layer, of the electric field created between the microtips and the grids.

Dans le procédé objet de l'invention, la couche de grille est gravée pour former les grilles, avantageusement avant la formation des trous et de la couche mince.In the process which is the subject of the invention, the grid layer is etched to form the grids, advantageously before the holes and the thin layer are formed.

Selon un mode de mise en oeuvre particulier du procédé objet de l'invention, ladite couche mince électriquement isolante est formée avant les trous.According to a particular embodiment of the process which is the subject of the invention, said thin electrically insulating layer is formed before the holes.

On peut former en outre, sur ladite couche mince électriquement isolante, une autre couche mince qui est suffisamment conductrice pour permettre l'écoulement de charges électriques parasites susceptibles d'être créées pendant le fonctionnement du dispositif.It is also possible to form, on said thin electrically insulating layer, another thin layer which is sufficiently conductive to allow the flow of parasitic electrical charges likely to be created during the operation of the device.

Cette autre couche mince, qui est suffisamment conductrice pour permettre l'écoulement de charges électriques parasites, peut être formée avant ou avantageusement après l'étape de formation des trous.This other thin layer, which is sufficiently conductive to allow the flow of parasitic electrical charges, can be formed before or advantageously after the step of forming the holes.

Une couche de protection peut être formée sur ladite couche mince électriquement isolante soit directement soit par dessus ladite autre couche mince suffisamment conductrice pour permettre l'écoulement des charges lorsqu'elle existe.A protective layer can be formed on said thin electrically insulating layer either directly or over said other thin layer sufficiently conductive to allow the flow of charges when it exists.

Cette couche de protection peut être déposée avant ou avantageusement après la formation des trous.This protective layer can be deposited before or advantageously after the holes have been formed.

Cette couche de protection peut être éliminée par gravure après l'étape de formation des micropointes.This protective layer can be removed by etching after the step of forming the microtips.

En variante, cette couche de protection n'est pas éliminée ou n'est que partiellement éliminée après l'étape de formation des micropointes.As a variant, this protective layer is not removed or is only partially removed after the step of forming the microtips.

La ou les couches formées par dessus les grilles, qui sont résistives ou conductrices, peuvent être déposées après la réalisation des trous.The layer or layers formed over the grids, which are resistive or conductive, can be deposited after the holes have been made.

La présente invention sera mieux comprise à la lecture de la description d'exemples de réalisation donnés ci-après à titre purement indicatif et nullement limitatif, en faisant référence aux dessins annexés sur lesquels :

  • la figure 1 est une vue schématique et partielle d'un dispositif d'affichage à micropointes connu,
  • la figure 2 est une vue schématique et partielle d'un dispositif d'affichage à micropointes conforme à la présente invention,
  • la figure 3 est une vue schématique et partielle d'un autre dispositif conforme à la présente invention, dans lequel une couche résistive est formée sur les conducteurs cathodiques,
  • la figure 4 est une vue schématique et partielle d'un autre dispositif conforme à l'invention dans lequel la couche isolante qui est formée sur les grilles est surgravée, et
  • la figure 5 est une vue schématique et partielle d'un autre dispositif conforme à l'invention dans lequel une fine couche électriquement conductrice est déposée après gravure des trous du dispositif.
The present invention will be better understood on reading the description of exemplary embodiments given below by way of purely indicative and in no way limiting, with reference to the appended drawings in which:
  • FIG. 1 is a schematic and partial view of a known microtip display device,
  • FIG. 2 is a schematic and partial view of a microtip display device according to the present invention,
  • FIG. 3 is a schematic and partial view of another device according to the present invention, in which a resistive layer is formed on the cathode conductors,
  • FIG. 4 is a schematic and partial view of another device according to the invention in which the insulating layer which is formed on the grids is over-etched, and
  • Figure 5 is a schematic and partial view of another device according to the invention in which a thin electrically conductive layer is deposited after etching the holes in the device.

Sur la figure 1, on a représenté, de façon schématique et partielle un dispositif connu d'affichage à micropointes.In Figure 1, there is shown schematically and partially a known microtip display device.

Ce dispositif connu comprend une anode cathodoluminescente formée sur un substrat en verre 2 et comportant une couche conductrice et transparente 4, par exemple en ITO et, sur cette couche 4, une couche 6 de poudre luminescente.This known device comprises a cathodoluminescent anode formed on a glass substrate 2 and comprising a conductive and transparent layer 4, for example made of ITO and, on this layer 4, a layer 6 of luminescent powder.

Le dispositif de la figure 1 comprend aussi une source d'électrons à micropointes formée sur un autre substrat 8 isolant et comprenant des conducteurs cathodiques tels que le conducteur 10, une couche isolante 12 formée sur ces conducteurs cathodiques et des grilles telles que la grille 14, formées sur la couche isolante 12 et perpendiculaires aux conducteurs cathodiques 10.The device of FIG. 1 also comprises a source of microtip electrons formed on another insulating substrate 8 and comprising cathode conductors such as the conductor 10, a layer insulating 12 formed on these cathode conductors and grids such as the grid 14, formed on the insulating layer 12 and perpendicular to the cathode conductors 10.

Des micropointes telles que la micropointe 16 sont formées sur ces derniers, dans des trous 17 réalisés dans les grilles et la couche isolante 12.Microtips such as microtip 16 are formed on the latter, in holes 17 made in the grids and the insulating layer 12.

De plus, des espaceurs tels que l'espaceur 18 sont disposés entre l'anode cathodoluminescente et les grilles pour maintenir la rigidité du dispositif lorsque le vide est fait entre l'anode cathodoluminescente et la source d'électrons à micropointes.In addition, spacers such as the spacer 18 are disposed between the cathodoluminescent anode and the grids to maintain the rigidity of the device when a vacuum is created between the cathodoluminescent anode and the source of microtip electrons.

Dans ce dispositif, rien n'est prévu, en cas de défaut d'isolation électrique, pour limiter le courant électrique I entre l'anode et les grilles, entre l'anode et les micropointes, et entre les micropointes et les grilles.In this device, nothing is provided, in the event of an electrical insulation fault, to limit the electric current I between the anode and the grids, between the anode and the microtips, and between the microtips and the grids.

Un tel dispositif est extrêmement sensible aux courts-circuits, très instable et difficile à maîtriser.Such a device is extremely sensitive to short circuits, very unstable and difficult to control.

Le dispositif conforme à l'invention, qui est schématiquement et partiellement représenté sur la figure 2 diffère du dispositif de la figure 1 par le fait qu'il comprend en outre une couche 20 électriquement isolante, formée sur les grilles et percée en regard des micropointes, cette couche 20 étant prévue pour limiter le courant entre l'anode et les grilles.The device according to the invention, which is schematically and partially shown in FIG. 2, differs from the device in FIG. 1 in that it further comprises an electrically insulating layer 20, formed on the grids and pierced opposite the microtips. , this layer 20 being provided to limit the current between the anode and the grids.

Le dispositif de la figure 2 comprend aussi une couche 21 qui recouvre la couche 20 et qui est suffisamment conductrice pour permettre l'écoulement de charges électriques parasites susceptibles d'être créées pendant le fonctionnement du dispositif et qui comporte aussi des trous en regard des micropointes.The device of FIG. 2 also comprises a layer 21 which covers the layer 20 and which is sufficiently conductive to allow the flow of parasitic electrical charges likely to be created during the operation of the device and which also has holes facing the microtips. .

Cette couche 21 évite la perturbation, par la couche 20, du champ électrique créé entre les micropointes et les grilles lorsque le dispositif fonctionne.This layer 21 avoids the disturbance, by layer 20, of the electric field created between the microtips and the grids when the device is operating.

Dans une variante non représentée, la couche 21 n'existe pas et, pour éviter la perturbation du champ électrique, le diamètre des trous formés dans la couche 20 est supérieur à celui des trous formés dans les grilles.In a variant not shown, the layer 21 does not exist and, to avoid disturbance of the electric field, the diameter of the holes formed in the layer 20 is greater than that of the holes formed in the grids.

On peut aussi réaliser un dispositif conforme à l'invention dans lequel à la fois la couche 21 existe et cette condition sur les diamètres est réalisée.It is also possible to produce a device according to the invention in which both the layer 21 exists and this condition on the diameters is fulfilled.

On a symbolisé par une flèche en pointillés sur la figure 2 le courant limité i entre l'anode et les grilles.The limited current i between the anode and the grids has been symbolized by a dotted arrow in FIG. 2.

Cette limitation constitue déjà une amélioration très importante.This limitation already constitutes a very significant improvement.

Cependant, rien n'est encore prévu pour limiter le courant entre l'anode et les micropointes et entre les grilles et les micropointes.However, nothing is yet planned to limit the current between the anode and the microtips and between the grids and the microtips.

C'est pourquoi l'invention est de préférence appliquée aux dispositifs d'affichage à micropointes dont la source d'électrons comporte une couche résistive entre les conducteurs cathodiques et les micropointes qui reposent sur cette couche résistive.This is why the invention is preferably applied to microtip display devices whose electron source comprises a resistive layer between the cathode conductors and the microtips which rest on this resistive layer.

Une telle source d'électrons est décrite dans les documents (2) et (3) mentionnés plus haut.Such an electron source is described in documents (2) and (3) mentioned above.

La figure 3 est une vue schématique et partielle d'un dispositif conforme à l'invention qui comprend une telle couche résistive entre les conducteurs cathodiques et les micropointes.Figure 3 is a schematic and partial view of a device according to the invention which comprises such a resistive layer between the cathode conductors and the microtips.

Ce dispositif de la figure 3 se distingue du dispositif de la figure 2 par le fait qu'il comprend en outre une couche résistive 22 entre la couche isolante 12 et les conducteurs cathodiques 24 qui sont ici maillés comme dans le document (3).This device of Figure 3 differs from the device of Figure 2 in that it comprises in addition a resistive layer 22 between the insulating layer 12 and the cathode conductors 24 which are here meshed as in document (3).

Grâce à la couche isolante 20 formée sur les grilles et à la couche résistive formée sur les conducteurs cathodiques, tous les courants i (entre l'anode et les grilles, entre l'anode et les micropointes et entre ces micropointes et les grilles) sont maîtrisés et limités.Thanks to the insulating layer 20 formed on the grids and to the resistive layer formed on the cathode conductors, all the currents i (between the anode and the grids, between the anode and the microtips and between these microtips and the grids) are controlled and limited.

Le dispositif est ainsi protégé contre tout risque de court-circuit.The device is thus protected against any risk of short circuit.

L'avantage le plus important de l'invention est de permettre d'accroître la tension d'anode et, éventuellement, de diminuer l'espace entre l'anode et la source d'électrons à micropointes sans risque d'accident électrique susceptible de détruire le dispositif.The most important advantage of the invention is that it makes it possible to increase the anode voltage and, possibly, to decrease the space between the anode and the source of microtip electrons without risk of electrical accident liable to destroy the device.

On donne ci-après, à titre purement indicatif et nullement limitatif, en faisant référence aux figures 4 et 5, quelques exemples d'un procédé de fabrication de dispositifs d'affichage à micropointes conformes à l'invention.A few examples of a method for manufacturing microtip display devices according to the invention are given below, purely by way of non-limiting indication, with reference to FIGS. 4 and 5.

Dans ces exemples :

  • les conducteurs cathodiques, tels que le conducteur cathodique 24 sont en niobium, ont une épaisseur de 0,2 µm et une structure en treillis avec par exemple des mailles carrées dont le pas vaut 25 µm et ces conducteurs cathodiques sont gravés pour former les colonnes du dispositif,
  • la couche résistive 22 est en silicium amorphe dopé au phosphore, elle est déposée sur les conducteurs cathodiques et l'épaisseur de cette couche résistive est de l'ordre de 1 µm,
  • la couche isolante 12 est en silice, elle est déposée sur la couche résistive 22 en silicium et l'épaisseur de cette couche isolante 12 est également de l'ordre de 1 µm, et
  • une couche métallique 14 en niobium formant la couche de grille est déposée sur cette couche isolante 12 en silice et l'épaisseur de cette couche métallique est de l'ordre de 0,4 µm, cette couche métallique en niobium étant gravée pour former les grilles suivant les lignes du dispositif.
In these examples:
  • the cathode conductors, such as the cathode conductor 24 are made of niobium, have a thickness of 0.2 μm and a lattice structure with for example square meshes whose pitch is equal to 25 μm and these cathode conductors are etched to form the columns of the device,
  • the resistive layer 22 is made of amorphous silicon doped with phosphorus, it is deposited on the cathode conductors and the thickness of this resistive layer is of the order of 1 μm,
  • the insulating layer 12 is made of silica, it is deposited on the resistive layer 22 of silicon and the thickness of this insulating layer 12 is also of the order of 1 μm, and
  • a metallic layer 14 made of niobium forming the grid layer is deposited on this insulating layer 12 made of silica and the thickness of this metallic layer is of the order of 0.4 μm, this metallic layer of niobium being etched to form the grids along the lines of the device.

Dans un premier exemple du procédé, une couche isolante 26 en silice (figure 4) est déposée sur les grilles.In a first example of the method, an insulating layer 26 of silica (FIG. 4) is deposited on the grids.

L'épaisseur de cette couche 26 est par exemple égale à 0,2 µm.The thickness of this layer 26 is for example equal to 0.2 μm.

Cette couche 26 est réalisable par dépôt chimique en phase vapeur, par pulvérisation cathodique ou par toute autre méthode de dépôt de couches minces.This layer 26 can be produced by chemical vapor deposition, by sputtering or by any other method of depositing thin layers.

Une fine couche suffisamment conductrice 28, par exemple en niobium, en molybdène ou encore en SnO₂, est déposée sur cette couche de silice 26 pour permettre la réalisation des micropointes et éventuellement l'écoulement des charges parasites au cours du fonctionnement du dispositif lorsque cette couche est conservée.A thin sufficiently conductive layer 28, for example made of niobium, molybdenum or SnO₂, is deposited on this silica layer 26 to allow the creation of microtips and possibly the flow of parasitic charges during operation of the device when this layer is kept.

L'épaisseur de cette couche 28 est par exemple égale à 50 nm.The thickness of this layer 28 is for example equal to 50 nm.

Cette couche 28 est de préférence formée par évaporation au moyen d'un canon à électrons ou par pulvérisation.This layer 28 is preferably formed by evaporation by means of an electron gun or by spraying.

Dans l'exemple considéré, où l'on utilise des conducteurs cathodiques formant des mailles, des trous, dont le diamètre est de l'ordre de 1,4 µm, sont gravés dans la fine couche conductrice 28, la couche isolante 12, la couche de grille 14 et la couche isolante 26, à l'intérieur des mailles des conducteurs cathodiques, ou plus exactement à l'aplomb des domaines que délimitent ces mailles.In the example considered, where cathode conductors forming meshes are used, holes, the diameter of which is of the order of 1.4 μm, are etched in the thin conductive layer 28, the insulating layer 12, the grid layer 14 and insulating layer 26, inside the mesh of the conductors cathodic, or more exactly plumb with the domains delimited by these meshes.

On peut utiliser un procédé de gravure humide ou un procédé de gravure sèche.A wet etching process or a dry etching process can be used.

De préférence, on utilise un procédé de gravure ionique réactive pour graver les couches métalliques et les couches isolantes.Preferably, a reactive ion etching process is used to etch the metal layers and the insulating layers.

De préférence également, on réalise une sur-gravure chimique de la silice de la couche 12, cette sur-gravure étant par exemple de quelques centaines de nanomètres (longueur e de la figure 4), ce qui permet d'agrandir les trous au niveau de cette couche 12.Preferably also, a chemical over-etching of the silica of the layer 12 is carried out, this over-etching being for example a few hundred nanometers (length e in FIG. 4), which makes it possible to enlarge the holes at the level of this layer 12.

Un tel procédé de sur-gravure est connu et permet d'éviter la métallisation des bords des trous dans la silice au cours de la réalisation des micropointes.Such an over-etching process is known and makes it possible to avoid metallization of the edges of the holes in the silica during the production of the microtips.

Avantageusement une sur-gravure de la couche 26 est réalisée afin de permettre de dégager les grilles autour des trous 30 et donc d'éviter une perturbation du champ électrique (lors du fonctionnement du dispositif) entre les micropointes 16 et les grilles, cette perturbation étant provoquée par un phénomène de charge de la couche isolante 26.Advantageously, an over-etching of the layer 26 is carried out in order to allow the grids to be released around the holes 30 and therefore to avoid a disturbance of the electric field (during operation of the device) between the microtips 16 and the grids, this disturbance being caused by a charging phenomenon of the insulating layer 26.

Il est possible de réaliser en même temps les sur-gravures des couches 12 et 26 lorsque celles-ci sont faites du même matériau, ce qui est le cas dans l'exemple décrit.It is possible to produce the over-etchings of layers 12 and 26 at the same time when they are made of the same material, which is the case in the example described.

Les micropointes 16 sont ensuite réalisées selon le procédé décrit dans le document (1) mentionné plus haut.The microtips 16 are then produced according to the method described in the document (1) mentioned above.

La fine couche conductrice 28 de protection permet

  • une meilleure adhérence d'une couche de nickel (non représentée) qui est utilisée lors de l'élaboration des micropointes (voir le document (1))
  • l'assurance de la continuité électrique pendant la phase de dissolution électrochimique du nickel.
The thin conductive protective layer 28 allows
  • better adhesion of a nickel layer (not shown) which is used during the development of the microtips (see document (1))
  • ensuring electrical continuity during the electrochemical dissolution phase of nickel.

Une fois les micropointes réalisées, les prises de contact des conducteurs de lignes et des conducteurs de colonnes sont dégagées si nécessaire.Once the microtips have been made, the contact points for the row conductors and the column conductors are released if necessary.

La fine couche conductrice 28 peut éventuellement être éliminée par une gravure appropriée.The thin conductive layer 28 can optionally be removed by appropriate etching.

On décrit maintenant un autre exemple de procédé en faisant référence à la figure 5.Another example of the process will now be described with reference to FIG. 5.

Dans cet exemple, la fine couche conductrice (suffisamment conductrice pour permettre l'écoulement des charges) peut être déposée après gravure des trous, auquel cas le fond des trous est recouvert par cette couche.In this example, the thin conductive layer (sufficiently conductive to allow the flow of charges) can be deposited after etching the holes, in which case the bottom of the holes is covered by this layer.

La figure 5 illustre schématiquement et partiellement ce cas où la fine couche conductrice 28 est déposée après gravure des trous et l'on voit que le fond des trous est recouvert par cette fine couche conductrice 28 (qui recouvre la couche isolante 26 en silice déjà mentionnée dans la description de la figure 4).FIG. 5 schematically and partially illustrates this case where the thin conductive layer 28 is deposited after etching the holes and it can be seen that the bottom of the holes is covered by this fine conductive layer 28 (which covers the insulating layer 26 of silica already mentioned in the description of Figure 4).

On voit aussi sur la figure 5 que les micropointes 16 sont ainsi au-dessus de la fine couche conductrice.It can also be seen in FIG. 5 that the microtips 16 are thus above the thin conductive layer.

Le dépôt de la fine couche conductrice, après gravure des trous, permet d'éviter la gravure de cette couche.The deposition of the thin conductive layer, after etching the holes, makes it possible to avoid etching of this layer.

Claims (9)

Dispositif d'affichage à micropointes, ce dispositif comprenant un premier substrat électriquement isolant (2) portant une anode cathodoluminescente (4, 6) et un deuxième substrat électriquement isolant (8) portant, en regard du premier substrat (2) : - une première série d'électrodes parallèles jouant le rôle de conducteurs cathodiques (10, 24) et portant des micropointes (16) en matériau émetteur d'électrons, - une couche électriquement isolante (12) sur ces conducteurs cathodiques, - une deuxième série d'électrodes parallèles jouant le rôle de grilles (14), placées sur cette couche isolante (12) et faisant un angle avec les conducteurs cathodiques, des trous (17, 30) étant formés dans la couche isolante et les grilles pour le passage des micropointes, ce dispositif étant caractérisé en ce qu'il comprend en outre, sur les grilles, une couche mince (20, 26) électriquement isolante, pour limiter le courant électrique susceptible de circuler entre l'anode cathodoluminescente et les grilles et empêcher la survenance d'un arc électrique entre cette anode et ces grilles, cette couche mince comportant aussi des trous en regard des micropointes et en ce que ladite couche mince électriquement isolante est associée à des moyens aptes à éviter la perturbation, par cette couche mince électriquement isolante, du champ électrique créé entre les micropointes et les grilles.Microtip display device, this device comprising a first electrically insulating substrate (2) carrying a cathodoluminescent anode (4, 6) and a second electrically insulating substrate (8) carrying, opposite the first substrate (2): - a first series of parallel electrodes acting as cathode conductors (10, 24) and carrying microtips (16) made of electron emitting material, - an electrically insulating layer (12) on these cathode conductors, - A second series of parallel electrodes acting as grids (14), placed on this insulating layer (12) and at an angle with the cathode conductors, holes (17, 30) being formed in the insulating layer and the grids for the passage of microtips, this device being characterized in that it further comprises, on the grids, a thin electrically insulating layer (20, 26), in order to limit the electric current liable to circulate between the cathodoluminescent anode and the grids and prevent the occurrence of an electric arc between this anode and these grids, this thin layer also comprising holes opposite the microtips and in that said electrically insulating thin layer is associated with means capable of avoiding the disturbance, by this electrically insulating thin layer, of the field created between the microtips and the grids. Dispositif selon la revendication 1, caractérisé en ce que les moyens aptes à éviter la perturbation du champ électrique comprennent une autre couche mince (28) qui recouvre ladite couche mince isolante et qui est suffisamment conductrice pour permettre l'écoulement de charges électriques parasites susceptibles d'être créées pendant le fonctionnement du dispositif et qui comporte aussi des trous en regard des micropointes.Device according to claim 1, characterized in that the means capable of avoiding the disturbance of the electric field comprise another thin layer (28) which covers said thin layer insulating and which is sufficiently conductive to allow the flow of parasitic electrical charges likely to be created during the operation of the device and which also has holes opposite the microtips. Dispositif selon l'une quelconque des revendications 1 et 2, caractérisé en ce que le diamètre des trous formés dans ladite couche mince isolante (26) est supérieur au diamètre des trous formés dans les grilles, pour éviter la perturbation du champ électrique créé entre les micropointes et les grilles, cette couche mince isolante étant ainsi surgravée.Device according to any one of claims 1 and 2, characterized in that the diameter of the holes formed in said thin insulating layer (26) is greater than the diameter of the holes formed in the grids, to avoid disturbance of the electric field created between the microtips and grids, this thin insulating layer thus being over-etched. Dispositif selon l'une quelconque des revendications 1 à 3, caractérisé en ce qu'il comprend en outre une couche résistive (22) qui est interposée entre chaque conducteur cathodique et les micropointes (16) correspondantes, ces dernières reposant ainsi sur cette couche résistive.Device according to any one of Claims 1 to 3, characterized in that it further comprises a resistive layer (22) which is interposed between each cathode conductor and the corresponding microtips (16), the latter thus resting on this resistive layer . Procédé de fabrication du dispositif d'affichage à micropointes selon la revendication 1, procédé selon lequel on forme ladite anode cathodoluminescente (4, 6) sur le premier substrat (2), et on forme sur le deuxième substrat (8) les conducteurs cathodiques (10, 24), ladite couche électriquement isolante (12), une couche de grille (14) destinée à la formation des grilles, les trous (17, 30) puis les micropointes (16), ce procédé étant caractérisé en ce qu'on forme en outre ladite couche mince (20, 26) électriquement isolante sur la couche de grille et en ce que ladite couche mince électriquement isolante est associée à des moyens aptes à éviter la perturbation, par cette couche mince électriquement isolante, du champ électrique créé entre les micropointes et les grilles.Method of manufacturing the microtip display device according to claim 1, method according to which said cathodoluminescent anode (4, 6) is formed on the first substrate (2), and the cathode conductors (8) are formed on the second substrate (8) 10, 24), said electrically insulating layer (12), a grid layer (14) intended for the formation of grids, the holes (17, 30) then the microtips (16), this process being characterized in that further forms said electrically insulating thin layer (20, 26) on the grid layer and in that said electrically insulating thin layer is associated with means capable of avoiding the disturbance, by this electrically insulating thin layer, of the electric field created between microtips and grids. Procédé selon la revendication 5, caractérisé en ce que ladite couche mince électriquement isolante (26) est formée avant les trous.Method according to claim 5, characterized in that said thin electrically insulating layer (26) is formed before the holes. Procédé selon la revendication 6, caractérisé en ce qu'on forme en outre, sur ladite couche mince électriquement isolante (26), une autre couche mince (28) qui est suffisamment conductrice pour permettre l'écoulement de charges électriques parasites susceptibles d'être créées pendant le fonctionnement du dispositif.A method according to claim 6, characterized in that a further thin layer (28) is formed on said thin electrically insulating layer (26) which is sufficiently conductive to allow the flow of parasitic electrical charges liable to be created during the operation of the device. Procédé selon l'une quelconque des revendications 6 et 7, caractérisé en ce qu'on forme sur la couche mince la plus externe réalisée sur les grilles une couche protectrice.Process according to either of Claims 6 and 7, characterized in that a protective layer is formed on the outermost thin layer produced on the grids. Procédé selon l'une quelconque des revendications 7 et 8, caractérisé en ce que la ou les couches formées par-dessus les grilles, qui sont résistives ou conductrices, sont déposées après la réalisation des trous.Method according to either of Claims 7 and 8, characterized in that the layer or layers formed over the grids, which are resistive or conductive, are deposited after the holes have been made.
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FR2836280A1 (en) * 2002-02-19 2003-08-22 Commissariat Energie Atomique EMISSIVE LAYER CATHODE STRUCTURE FORMED ON RESISTIVE LAYER
WO2003071571A1 (en) * 2002-02-19 2003-08-28 Commissariat A L'energie Atomique Cathode structure for an emission display
US6917147B2 (en) 2002-02-19 2005-07-12 Commissariat A L'energie Atomique Cathode structure with emissive layer formed on a resistive layer
US7759851B2 (en) 2002-02-19 2010-07-20 Commissariat A L'energie Atomique Cathode structure for emissive screen

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DE69410512D1 (en) 1998-07-02
EP0616356B1 (en) 1998-05-27
JPH06325690A (en) 1994-11-25
FR2702869B1 (en) 1995-04-21
FR2702869A1 (en) 1994-09-23
DE69410512T2 (en) 1998-12-17

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