EP1023741B1 - Electron source with microtips, with focusing grid and high microtip density, and flat screen using same - Google Patents

Electron source with microtips, with focusing grid and high microtip density, and flat screen using same Download PDF

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Publication number
EP1023741B1
EP1023741B1 EP98949053A EP98949053A EP1023741B1 EP 1023741 B1 EP1023741 B1 EP 1023741B1 EP 98949053 A EP98949053 A EP 98949053A EP 98949053 A EP98949053 A EP 98949053A EP 1023741 B1 EP1023741 B1 EP 1023741B1
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EP
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Prior art keywords
holes
insulating layer
microtips
conductive layer
layer
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EP98949053A
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German (de)
French (fr)
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EP1023741A1 (en
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Aimé Perrin
Brigitte Montmayeul
Robert Meyer
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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

Definitions

  • the present invention relates to a microtip electron source, focusing gate and high micropoint density. It also relates to a flat screen using such a source.
  • FR-A-2 593 953 and FR-A-2 623 013 disclose cathodoluminescence display devices excited by field emission. These devices comprise a source of electrons with microtip emitting cathodes.
  • FIG. 1 is a cross-sectional view of such a microtip display screen.
  • the screen consists of a cathode 1, which is a flat structure, arranged opposite another plane structure forming the anode 2.
  • the cathode 1 and the anode 2 are separated by a space in which the empty.
  • the cathode 1 comprises a glass substrate 11 on which is deposited the conductive level 12 in contact with the electron emitting tips 13.
  • the conductive level 12 is covered with an insulating layer 14, for example silica, itself covered of a conductive layer 15.
  • the anode 2 comprises a transparent substrate 21 covered with a transparent electrode 22 on which phosphorescent phosphors or phosphors 23 are deposited.
  • the operation of this screen will now be described.
  • the anode 2 is brought to a positive voltage of several hundred volts with respect to the tips 13 (typically 200 to 500 V).
  • a positive voltage of a few tens of volts typically 60 to 100 V
  • Electrons are then torn off at the tips 13 and are attracted to the anode 2.
  • the trajectories electrons are included in a cone of half-angle at the apex ⁇ depending on different parameters, among others the shape of the tips 13. This angle causes a defocusing of the electron beam 31 all the more important that the distance between the anode and the cathode is big.
  • Figure 2 illustrates the case where the focusing grid is disposed on the cathode.
  • Figure 2 take the example of Figure 1 but limited to a single microtip for clarity in the drawing.
  • An insulating layer 16 has been deposited on the extraction grid 15 and supports a metal layer 17 serving as a focusing grid. Holes 19, of suitable diameter (typically between 8 and 10 ⁇ m) and concentric with the holes 18, have been etched in the layers 16 and 17.
  • the insulating layer 16 serves to electrically isolate the extraction grid 15 and the focusing grid 17.
  • the focusing grid is polarized with respect to the cathode so as to give the electron beam 32 the shape shown in FIG.
  • the distance between two adjacent microtips is of the order of 3 microns.
  • this distance is of the order of 10 to 12 microns.
  • the density of microtips that is to say the density of electron emitters, is between 9 and 16 times lower. This results in a decrease in brightness of the screen.
  • the phosphors are deposited on the anode in the form of parallel strips, successively red-green-blue, etc.
  • the phosphors are deposited on the anode in the form of parallel strips, successively red-green-blue, etc.
  • the focusing is done in the direction perpendicular to these bands to avoid color mixing.
  • the invention makes it possible to remedy the problem of the low density of microtips presented by the electron beam sources of the prior art. This is achieved by replacing the circular openings of the focusing grid with slots.
  • the invention is particularly effective in an application to flat screens where the phosphors are arranged in strips. It is proposed to engrave, in the focusing grid, openings in the form of slots, the microtips being aligned on the axes of these slots. By arranging the phosphors located on the anode in the form of strips parallel to the slits of the electron source and just above the corresponding slots, the electrons emitted by the microtips of these slots remain concentrated on the phosphor strip which makes them face. There will be no color mixing. If the focus is not obtained in the direction of the bands, there is a slight spreading of the pixel in this direction, which does not affect the quality of the image.
  • the focusing grid according to the present invention thus provides a focus function in a single direction.
  • the microtip electron source may comprise a plurality of electron emission zones arranged in the form of matrix arrangements in rows and in columns, the cathode conductors and the gate electrodes being in number corresponding to the lines and columns to provide matrix access to the microtip electron source.
  • each transmission zone comprises several rows of microtips
  • each row of microtips corresponds to one or more slots in the focusing grid.
  • the subject of the invention is also a device comprising a first and a second planar structure maintained facing each other and at a determined distance from each other by means forming spacer, the first planar structure comprising, on its inner face to the device, a micropoint electron source as defined above, the second planar structure comprising, on its inner face to the device, anode means.
  • Such a device can be used to form a flat display screen, phosphors being interposed between the microtip electron source and the anode means.
  • the invention also relates to a flat display screen comprising a first and a second planar structure held opposite and at a determined distance from one another by spacer means, the first planar structure comprising on its face internal to the screen, a micropoint electron source as defined above, of the type in which each emission zone comprising several rows of microtips, at each row of microtips, corresponds to one or more slots in the focusing grid, the second planar structure comprising, on its internal face to the screen, a conductive anode-forming layer supporting luminophores arranged in bands of alternately red, green and blue color, each strip being located parallel to and facing a series (line or column) of electron emission zones, the slots of the focusing grid having their main axis directed in the direction of the phosphor strips res, each transmission area defining a pixel for the viewing screen.
  • microtip electron source according to the present invention can be used in connection with anodes of different structure, in particular conventional structures. made for CRT screens, suitable for flat screens.
  • the step of deepening the holes can be performed by etching. This step and the step of etching the second insulating layer can be conducted simultaneously.
  • the deepening step of the holes in the first insulating layer and the step of lateral etching of the second insulating layer may be carried out simultaneously and carried out by isotropic etching.
  • the step of drilling holes can be performed by etching.
  • the elimination step of the electrolytically deposited conductive material can be carried out by chemical dissolution.
  • the cathodic connection means can be obtained by deposition of cathode conductors on the support, followed by a deposit of a resistive layer.
  • Figure 3 is a partial view in section of a micropoint electron source according to the invention. It was developed from a glass support 40. On this support 40, a first layer 41 forming cathodic connection means, a first insulating layer 42, was successively deposited. and a first conductive layer 43. In the layers 42 and 43, holes 44 have been etched to the first layer 41. Point-shaped electron emitters 45 have been deposited within the holes 44. and in contact with the first layer 41. The microtips 45 are arranged in alignments. For use of the electron source as a cathode of a flat color display, the microtip alignments are parallel to the phosphor strips disposed on the anode of the screen.
  • the conductive layer 43 serves as an electron extraction grid. It is covered with an insulating layer 46 (second insulating layer) and a conductive layer 47 (second conductive layer). Slots 48 have been made in the layers 46 and 47 until reaching the extraction grid 43.
  • the axes of the slits 48 coincide with the axes of the emitter or microtip alignments 45.
  • the slits 48 may have a width of 8 to 10 ⁇ m.
  • the pitch of the slots (along their main axis), and consequently the pitch of the emitter lines, is 10 to 12 ⁇ m.
  • the distance between two emitters of the same line is of the order of 3 ⁇ m.
  • the solution proposed by the invention therefore makes it possible to have an emitter density which is 3 to 4 times higher than in the case where the focusing is carried out in all the directions of each of the emitters (case of FIG. 2).
  • the micropoint electron source shown in Figure 3 is generally intended to be used as a cathode of a flat display panel.
  • This flat screen is a device consisting of a cathode structure and an anodic structure vis-à-vis, between which was evacuated.
  • the distance separating the extraction grid 43 from the focusing grid 47 is very small. In some use cases, it could result in a risk of arc in the vacuum between these two grids.
  • FIG. 4 A solution to overcome this drawback is shown in Figure 4 where the same elements as for Figure 3 are designated by the same references.
  • the slots 48 have been limited to the focusing grid.
  • the insulating layer 46 has been etched with slots 49 centered on the corresponding emitter lines and of width less than the width of the slits 48.
  • the insulating layer 46 may be pierced with concentric holes in the holes 44.
  • the diameter of these concentric holes or the width of the slots 49, as the case may be, may be two to three times the diameter of the holes 44.
  • the extension of the insulating layer 46 on the extraction grid 43 provides better protection against electric arcs.
  • the electrons emitted by the microtips corresponding to a focusing gate slot of an electron source according to the present invention are focused in the direction perpendicular to the axis of the slot. They deviate very little from the plane perpendicular to the source and passing through the axis of the slot. The impacts of these electrons on a plane parallel to the cathode are therefore located in a narrow band parallel to the axis of the slot but a little longer than this.
  • the electron sources as represented in FIGS. 3 and 4 can be produced by using conventional deposition, photolithography and etching techniques in microelectronics, the microtips being produced according to the known art.
  • simulation calculations show that the quality of the focus depends on the centering of the focusing grid along the axis of the emitters and that this parameter is very sensitive.
  • the required accuracy requires the use of high performance devices that will be less suitable as the size of the screens to achieve increases.
  • FIGS. 5A to 5D A first example of this method is illustrated in FIGS. 5A to 5D. It provides a microtip electron source of the type shown in FIG.
  • a metal layer was deposited on a glass slide 50 which has been etched to form columns 51.
  • a resistive layer 52 has then been uniformly deposited and has a flat surface.
  • a first insulating layer 53, a conductive layer 54 and a second insulating layer 55 are successively deposited.
  • Insulating layers 53 and 55 may be silica.
  • the conductive layer 54 intended to form the electron extraction grid may be made of niobium.
  • holes 56 are engraved in the insulating layer 55, the centers of which are aligned on lines parallel to each other.
  • the holes 56 reveal the conductive layer 54.
  • the distance between two successive holes of the same line is of the order of 3 microns.
  • the distance between two consecutive lines is about 10 to 12 ⁇ m. For the sake of clarity, only a small portion of a single line of holes is shown in FIG.
  • the next step (see FIG. 5B) consists in electrolytic deposition of a conductive material (for example an iron-nickel alloy) on the revealed portions of the conductive layer 54, that is to say at the bottom of the holes 56.
  • a conductive material for example an iron-nickel alloy
  • the thickness of the electrolytic deposit is adjusted so as to obtain, for each hole, the growth of a mushroom whose foot fills the hole and such that the cap develops on the outer face of the insulating layer 55. Growth is continued until the diameter of the cap reaches the desired width for the slot of the focusing grid. This width being approximately 10 microns, the mushrooms will coalesce to form a mass 57 in the form of a half-cylinder with a diameter equal to the desired width of the slot.
  • a second conductive layer is deposited in order to form the focusing grid.
  • This second conductive layer (made of metal or another resistive material) is deposited on the insulating layer 55 between the masses 57, to constitute the deposit 58, and on the masses 57 to constitute the deposit 59, as shown in FIG. 5B.
  • Each mass 57 serves as a mask for opening the focusing grid. As the axis of each half-cylinder forming a mass passes through the line joining the centers of the holes, the resulting opening will be automatically centered on this line.
  • the masses 57 are then chemically dissolved and the structure shown in FIG. 5C is obtained.
  • the openings 60 made in the focusing grid 58 are centered on the axes of the holes 56.
  • the metal layer 54 is then etched anisotropically through the holes 56 to deepen this hole to the first insulating layer 53.
  • the anisotropic etching is continued in the insulating layer 53 until reaching the resistive layer 52.
  • the insulating layers 53 and 55 are both made of silica in the example described, the etching both of these layers can be performed simultaneously.
  • holes 61 and 64 (in the extension of the holes 56 in FIG. 5C) are obtained passing respectively through the conductive layer 54 and the insulating layer 53.
  • a slot-like opening 62 is also obtained in FIG. the continuity of the slot 60.
  • microtips 63 are then conventionally made at the bottom of the holes 61.
  • the microtips, the holes of the extraction grid and the slots of the focusing grid are thus self-aligned.
  • FIGS. 6A to 6E A second example of a self-alignment method is illustrated in FIGS. 6A to 6E. It provides a microtip electron source of the type shown in FIG.
  • columns 71 of cathode conductors and a resistive layer 72 were deposited on a glass slide 70, as in the first example of the method.
  • a resin layer 85 has finally been deposited.
  • the choice of the thicknesses of the layers and the materials used may be the same as for the first example of the method.
  • Holes 76 have been opened in the resin layer 85 which serves as a mask for etching the insulating layer 75 and conducting layer 74. Holes 76 are thus deepened until reaching the first insulating layer 73.
  • the first insulating layer 73 is then chemically etched so as to extend the holes to the resistive layer 72. By performing an isotropic etching, a significant overgraving is obtained and the holes 84 made in the first insulating layer will have the profile shown in Figure 6B.
  • the second insulating layer 75 being of the same nature as the first insulating layer 73, is etched identically. An increase in the diameter of the holes 76 is obtained between the conductive layer 74 and the resin layer 85, which provides cavities 82. This increase in diameter is equal to at least twice the thickness of the first insulating layer 73.
  • Figure 6C shows the structure obtained after removal of the resin layer.
  • the second insulating layer 75 has holes 82 coaxial with the holes 76 of the conductive layer 74 but of larger diameter. These holes 82 may be insulated or secant (as shown in Figure 6C) following the thickness of the first insulating layer 73 and the distance between the holes 76 of the same line of holes.
  • An electrolytic deposition of a conductive material is then carried out from the conductive layer 74.
  • the deposition step is conducted so as to obtain masses 77 in the form of a half-cylinder, with a diameter equal to the desired width for the slot of the focusing grid (for example 10 ⁇ m). This is shown in Figure 6D.
  • a second conductive layer is deposited to form the focusing grid.
  • the deposit 78 is obtained between the masses 77 and the deposit 79 on the masses 77.
  • the masses 77 are then chemically dissolved to give the structure the profile shown in Figure 6E.
  • the openings 80 made in the focusing grid 78 are centered on the axes of holes 76.
  • This grid 78 is placed on the insulating layer 75 itself having an opening (constituted by the succession of adjacent holes 82) centered on the line of the holes. holes 76, the opening in the second insulating layer 75 being less wide than that of the focusing grid 78.
  • microtips 83 are then conventionally carried out at the bottom of the holes 84.
  • the microtips, the holes of the extraction grid and the slots of the focusing grid are thus self-aligned.
  • the electron source with microtips may be as shown in Figures 7 and 8. These figures show only part of the source of electrons corresponding to a pixel of the screen.
  • the holes 61 of the extraction grid, at the bottom of which are placed the electron emitters, are aligned in the slots 60 of the focusing grid 58. These slots can be the length of the pixel, as in FIG. can be divided into several parts, as in Figure 8.

Description

Domaine techniqueTechnical area

La présente invention concerne une source d'électrons à micropointes, à grille de focalisation et à densité élevée de micropointes. Elle concerne également un écran plat utilisant une telle source.The present invention relates to a microtip electron source, focusing gate and high micropoint density. It also relates to a flat screen using such a source.

Etat de la techniqueState of the art

Les documents FR-A-2 593 953 et FR-A-2 623 013 divulguent des dispositifs de visualisation par cathodoluminescence excitée par émission de champ. Ces dispositifs comprennent une source d'électrons à cathodes émissives à micropointes.Documents FR-A-2 593 953 and FR-A-2 623 013 disclose cathodoluminescence display devices excited by field emission. These devices comprise a source of electrons with microtip emitting cathodes.

A titre d'illustration, la figure 1 est une vue en coupe transversale d'un tel écran de visualisation à micropointes. Par souci de simplification, seulement quelques micropointes alignées ont été représentées. L'écran est constitué par une cathode 1, qui est une structure plane, disposée en regard d'une autre structure plane formant l'anode 2. La cathode 1 et l'anode 2 sont séparées par un espace dans lequel on a fait le vide. La cathode 1 comprend un substrat de verre 11 sur lequel est déposé le niveau conducteur 12 en contact avec les pointes émettrices d'électrons 13. Le niveau conducteur 12 est recouvert d'une couche isolante 14, par exemple en silice, elle-même recouverte d'une couche conductrice 15. Des trous 18, d'environ 1,3 µm de diamètre, ont été réalisés au travers des couches 14 et 15 jusqu'au niveau conducteur 12 pour déposer les pointes 13 sur ce niveau conducteur. La couche conductrice 15 sert de grille d'extraction pour les électrons qui seront émis par les pointes 13. L'anode 2 comprend un substrat transparent 21 recouvert d'une électrode transparente 22 sur laquelle sont déposés des phosphores luminescents ou luminophores 23.By way of illustration, FIG. 1 is a cross-sectional view of such a microtip display screen. For the sake of simplification, only a few aligned microtips have been represented. The screen consists of a cathode 1, which is a flat structure, arranged opposite another plane structure forming the anode 2. The cathode 1 and the anode 2 are separated by a space in which the empty. The cathode 1 comprises a glass substrate 11 on which is deposited the conductive level 12 in contact with the electron emitting tips 13. The conductive level 12 is covered with an insulating layer 14, for example silica, itself covered of a conductive layer 15. Holes 18, about 1.3 μm in diameter, were made through the layers 14 and 15 to the conductive level 12 to deposit the tips 13 on this driver level. The conductive layer 15 serves as an extraction grid for the electrons that will be emitted by the tips 13. The anode 2 comprises a transparent substrate 21 covered with a transparent electrode 22 on which phosphorescent phosphors or phosphors 23 are deposited.

Le fonctionnement de cet écran va maintenant être décrit. L'anode 2 est portée à une tension positive de plusieurs centaines de volts par rapport aux pointes 13 (typiquement 200 à 500 V). Sur la grille d'extraction 15, on applique une tension positive de quelques dizaines de volts (typiquement 60 à 100 V) par rapport aux pointes 13. Des électrons sont alors arrachés aux pointes 13 et sont attirés par l'anode 2. Les trajectoires des électrons sont comprises dans un cône de demi-angle au sommet θ dépendant de différents paramètres, entre autres de la forme des pointes 13. Cet angle entraîne une défocalisation du faisceau d'électrons 31 d'autant plus importante que la distance entre l'anode et la cathode est grande. Or, l'une des façons d'augmenter le rendement des phosphores, donc la luminosité des écrans, est de travailler avec des tensions anode-cathode plus grandes (entre 1 000 et 10 000 V), ce qui implique d'écarter davantage l'anode et la cathode afin d'éviter la formation d'un arc électrique entre ces deux électrodes.The operation of this screen will now be described. The anode 2 is brought to a positive voltage of several hundred volts with respect to the tips 13 (typically 200 to 500 V). On the extraction grid 15, a positive voltage of a few tens of volts (typically 60 to 100 V) is applied relative to the points 13. Electrons are then torn off at the tips 13 and are attracted to the anode 2. The trajectories electrons are included in a cone of half-angle at the apex θ depending on different parameters, among others the shape of the tips 13. This angle causes a defocusing of the electron beam 31 all the more important that the distance between the anode and the cathode is big. However, one of the ways to increase the phosphor yield, and therefore the brightness of the screens, is to work with larger anode-cathode voltages (between 1000 and 10 000 V), which implies further separation. anode and the cathode to prevent the formation of an electric arc between these two electrodes.

Si on désire conserver une bonne résolution sur l'anode, il faut refocaliser le faisceau d'électrons. Cette refocalisation est obtenue classiquement grâce à une grille qui peut être soit placée entre l'anode et la cathode, soit disposée sur la cathodeIf you want to keep a good resolution on the anode, you have to refocus the electron beam. This refocusing is conventionally obtained thanks to a grid which can be placed between the anode and the cathode, or arranged on the cathode

La figure 2 illustre le cas où la grille de focalisation est disposée sur la cathode. La figure 2 reprend l'exemple de la figure 1 mais limité à une seule micropointe pour plus de clarté dans le dessin. Une couche isolante 16 a été déposée sur la grille d'extraction 15 et supporte une couche métallique 17 servant de grille de focalisation. Des trous 19, de diamètre adéquat (typiquement entre 8 et 10 µm) et concentriques aux trous 18, ont été gravés dans les couches 16 et 17. La couche isolante 16 sert à isoler électriquement la grille d'extraction 15 et la grille de focalisation 17. La grille de focalisation est polarisée par rapport à la cathode de façon à donner au faisceau d'électrons 32 la forme représentée à la figure 2.Figure 2 illustrates the case where the focusing grid is disposed on the cathode. Figure 2 take the example of Figure 1 but limited to a single microtip for clarity in the drawing. An insulating layer 16 has been deposited on the extraction grid 15 and supports a metal layer 17 serving as a focusing grid. Holes 19, of suitable diameter (typically between 8 and 10 μm) and concentric with the holes 18, have been etched in the layers 16 and 17. The insulating layer 16 serves to electrically isolate the extraction grid 15 and the focusing grid 17. The focusing grid is polarized with respect to the cathode so as to give the electron beam 32 the shape shown in FIG.

Dans le cas d'un écran à micropointes sans grille de focalisation, tel que celui représenté sur la figure 1, la distance entre deux micropointes adjacentes est de l'ordre de 3 µm. Pour un écran à micropointes avec grille de focalisation, tel que représenté sur la figure 2, cette distance est de l'ordre de 10 à 12 µm. Dans ce cas, la densité de micropointes, c'est-à-dire la densité d'émetteurs d'électrons, est entre 9 et 16 fois plus faible. Ceci a pour conséquence une baisse de luminosité de l'écran.In the case of a microtip screen without focusing grid, such as that shown in Figure 1, the distance between two adjacent microtips is of the order of 3 microns. For a microtip screen with focusing grid, as shown in Figure 2, this distance is of the order of 10 to 12 microns. In this case, the density of microtips, that is to say the density of electron emitters, is between 9 and 16 times lower. This results in a decrease in brightness of the screen.

Dans un écran plat, les luminophores sont déposées sur l'anode sous forme de bandes parallèles, successivement rouge-vert-bleu, etc. Pour une bonne qualité de l'image restituée, il est impératif qu'il n'y ait pas de mélange de couleurs. Pour cela, il faut que tous les électrons émis par un pixel d'une couleur donnée aillent sur le luminophore correspondant, et non pas sur des luminophores voisins. On obtient ce résultat par le phénomène de focalisation. Etant donnée la structure en bandes des luminophores, il est important que la focalisation se fasse dans la direction perpendiculaire à ces bandes pour éviter les mélanges de couleurs.In a flat screen, the phosphors are deposited on the anode in the form of parallel strips, successively red-green-blue, etc. For a good quality of the rendered image, it is imperative that there is no color mixing. For that, it is necessary that all the electrons emitted by a pixel of a given color go on the corresponding phosphor, and not on neighboring luminophores. This result is obtained by the focusing phenomenon. Given the band structure of the phosphors, it is important that the focusing is done in the direction perpendicular to these bands to avoid color mixing.

Exposé de l'inventionPresentation of the invention

L'invention permet de remédier au problème de la faible densité de micropointes présentée par les sources d'électrons à grille de focalisation de l'art antérieur. Ceci est obtenu en remplaçant les ouvertures circulaires de la grille de focalisation par des fentes.The invention makes it possible to remedy the problem of the low density of microtips presented by the electron beam sources of the prior art. This is achieved by replacing the circular openings of the focusing grid with slots.

L'invention s'avère particulièrement efficace dans une application aux écrans plats où les luminophores sont disposés en bandes. Il est proposé de graver, dans la grille de focalisation, des ouvertures en forme de fentes, les micropointes étant alignées sur les axes de ces fentes. En disposant les luminophores situés sur l'anode sous forme de bandes parallèles aux fentes de la source d'électrons et juste au-dessus des fentes correspondantes, les électrons émis par les micropointes de ces fentes restent concentrés sur la bande de luminophore qui leur fait face. Il n'y aura donc pas de mélange de couleurs. Si la focalisation n'est pas obtenue dans le sens des bandes, il se produit un léger étalement du pixel dans cette direction, ce qui nuit assez peu à la qualité de l'image.The invention is particularly effective in an application to flat screens where the phosphors are arranged in strips. It is proposed to engrave, in the focusing grid, openings in the form of slots, the microtips being aligned on the axes of these slots. By arranging the phosphors located on the anode in the form of strips parallel to the slits of the electron source and just above the corresponding slots, the electrons emitted by the microtips of these slots remain concentrated on the phosphor strip which makes them face. There will be no color mixing. If the focus is not obtained in the direction of the bands, there is a slight spreading of the pixel in this direction, which does not affect the quality of the image.

La grille de focalisation conforme à la présente invention procure donc une fonction de focalisation dans une seule direction.The focusing grid according to the present invention thus provides a focus function in a single direction.

L'invention a donc pour objet une source d'électrons à micropointes comportant :

  • au moins une zone d'émission électronique constituée d'une pluralité de micropointes reliées électriquement à un conducteur cathodique,
  • au moins une électrode de grille, disposée en vis-à-vis de ladite zone d'émission électronique et percée d'ouvertures situées en regard des micropointes, pour extraire les électrons des micropointes,
  • une grille de focalisation des électrons émis, disposée en vis-à-vis de l'électrode de grille, et possédant des moyens d'ouverture situés en regard des micropointes, caractérisée en ce que les moyens d'ouverture de la grille de focalisation comprennent au moins une fente située en regard d'au moins deux micropointes successives,
et en ce que la grille de focalisation est séparée de l'électrode de grille d'extraction disposée en vis-à-vis par une couche de matériau électriquement isolant pourvue d'une fente alignée sur la fente de la grille de focalisation, ou d'une succession de trous alignés sur la fente de la grille de focalisation, et de largeur inférieure à la largeur de la fente de la grille de focalisation.The subject of the invention is therefore a source of microtip electrons comprising:
  • at least one electron emission zone consisting of a plurality of microtips electrically connected to a cathode conductor,
  • at least one gate electrode, disposed opposite said electron emission zone and pierced with apertures facing the microtips, for extracting the electrons from the microtips,
  • a focusing gate of the emitted electrons disposed opposite the gate electrode, and having opening means situated opposite the microtips, characterized in that the means for opening the focusing gate comprise at least one slot located opposite at least two successive microtips,
and in that the focusing grid is separated from the extraction grid electrode disposed facing a layer of electrically insulating material provided with a slot aligned with the slot of the focusing grid, or a succession of holes aligned on the slot of the focusing grid, and of width less than the width of the slot of the focusing grid.

Selon une disposition avantageuse, la source d'électrons à micropointes peut comprendre une pluralité de zones d'émission électronique disposées sous forme d'arrangement matriciel en lignes et en colonnes, les conducteurs cathodiques et les électrodes de grille étant en nombre correspondant aux lignes et aux colonnes pour conférer un accès matriciel à la source d'électrons à micropointes.According to an advantageous arrangement, the microtip electron source may comprise a plurality of electron emission zones arranged in the form of matrix arrangements in rows and in columns, the cathode conductors and the gate electrodes being in number corresponding to the lines and columns to provide matrix access to the microtip electron source.

Si chaque zone d'émission comporte plusieurs rangées de micropointes, à chaque rangée de micropointes correspond une ou plusieurs fentes dans la grille de focalisation.If each transmission zone comprises several rows of microtips, each row of microtips corresponds to one or more slots in the focusing grid.

L'invention a aussi pour objet un dispositif comportant une première et une deuxième structure plane maintenues en regard et à une distance déterminée l'une de l'autre par des moyens formant entretoise, la première structure plane comprenant, sur sa face interne au dispositif, une source d'électrons à micropointes telle que définie ci-dessus, la deuxième structure plane comprenant, sur sa face interne au dispositif, des moyens formant anode.The subject of the invention is also a device comprising a first and a second planar structure maintained facing each other and at a determined distance from each other by means forming spacer, the first planar structure comprising, on its inner face to the device, a micropoint electron source as defined above, the second planar structure comprising, on its inner face to the device, anode means.

Un tel dispositif peut être utilisé pour constituer un écran plat de visualisation, des luminophores étant interposés entre la source d'électrons à micropointes et les moyens formant anode.Such a device can be used to form a flat display screen, phosphors being interposed between the microtip electron source and the anode means.

L'invention a encore pour objet un écran plat de visualisation comportant une première et une deuxième structure plane maintenues en regard et à une distance déterminée l'une de l'autre par des moyens formant entretoise, la première structure plane comprenant, sur sa face interne à l'écran, une source d'électrons à micropointes telle que définie ci-dessus, du type où chaque zone d'émission comportant plusieurs rangées de micropointes, à chaque rangée de micropointes correspond une ou plusieurs fentes dans la grille de focalisation, la deuxième structure plane comprenant, sur sa face interne à l'écran, une couche conductrice formant anode et supportant des luminophores disposés en bandes de couleur alternativement rouge, verte et bleue, chaque bande étant située parallèlement et en regard d'une série (ligne ou colonne) de zones d'émission électronique, les fentes de la grille de focalisation ayant leur axe principal dirigé dans le sens des bandes de luminophores, chaque zone d'émission définissant un pixel pour l'écran de visualisation.The invention also relates to a flat display screen comprising a first and a second planar structure held opposite and at a determined distance from one another by spacer means, the first planar structure comprising on its face internal to the screen, a micropoint electron source as defined above, of the type in which each emission zone comprising several rows of microtips, at each row of microtips, corresponds to one or more slots in the focusing grid, the second planar structure comprising, on its internal face to the screen, a conductive anode-forming layer supporting luminophores arranged in bands of alternately red, green and blue color, each strip being located parallel to and facing a series (line or column) of electron emission zones, the slots of the focusing grid having their main axis directed in the direction of the phosphor strips res, each transmission area defining a pixel for the viewing screen.

Bien entendu, la source d'électrons à micropointes selon la présente invention peut être utilisée en relation avec des anodes de structure différente, en particulier des structures classiques réalisées pour des écrans à tube cathodique, adaptées aux écrans plats.Of course, the microtip electron source according to the present invention can be used in connection with anodes of different structure, in particular conventional structures. made for CRT screens, suitable for flat screens.

L'invention a en outre pour objet un procédé de fabrication d'une source d'électrons à micropointes et à grille de focalisation, comprenant :

  • une étape où l'on dépose successivement sur une face d'un support électriquement isolant : des moyens de connexion cathodiques, une première couche isolante électriquement d'épaisseur adaptée à la hauteur des futures micropointes, une première couche conductrice destinée à former la grille d'extraction, une deuxième couche isolante électriquement d'épaisseur correspondant à la distance devant séparer la grille d'extraction de la grille de focalisation,
  • une étape consistant à percer la deuxième couche isolante de trous atteignant la première couche conductrice, les axes des trous correspondant aux axes des futures micropointes, le diamètre de ces trous étant adapté à la taille des futures micropointes,
  • une étape de dépôt électrolytique de matériau conducteur dans lesdits trous, la première couche conductrice servant d'électrode au cours de l'électrolyse, le dépôt électrolytique remplissant lesdits trous à partir de la première couche conductrice et débordant sur la deuxième couche isolante en donnant d'abord au matériau conducteur déposé électrolytiquement la forme de champignons dont les chapeaux reposent sur la deuxième couche isolante, le dépôt électrolytique étant mené pour faire croître ensuite, par coalescence des chapeaux de champignons formés dans des trous adjacents et suffisamment proches, une masse de forme sensiblement demi-cylindrique par ensemble de trous adjacents et suffisamment proches,
  • une étape de dépôt d'une deuxième couche conductrice destinée à former la grille de focalisation, cette deuxième couche conductrice étant en un matériau de nature différente de celle du matériau conducteur déposé électrolytiquement,
  • une étape d'élimination du matériau conducteur déposé électrolytiquement, cette élimination laissant, dans la deuxième couche conductrice, une fente par masse précédemment formée et d'axe principal aligné sur les trous par lesquels elle a crû,
  • une étape d'approfondissement des trous jusqu'aux moyens de connexion cathodiques,
  • une étape de gravure de la deuxième couche isolante pour faire apparaître la première couche conductrice,
  • une étape de formation des micropointes sur les moyens de connexion cathodiques révélés par l'étape d'approfondissement des trous.
The invention further relates to a method of manufacturing a micropoint electron source and focusing gate comprising:
  • a step where one successively deposits on one face of an electrically insulating support: cathodic connection means, a first electrically insulating layer of thickness adapted to the height of the future microtips, a first conductive layer intended to form the grid of extraction, a second electrically insulating layer of thickness corresponding to the distance to separate the extraction grid from the focusing grid,
  • a step of piercing the second insulating layer of holes reaching the first conductive layer, the axes of the holes corresponding to the axes of the future microtips, the diameter of these holes being adapted to the size of the future microtips,
  • a step of electrolytic deposition of conductive material in said holes, the first conductive layer serving as an electrode during the electrolysis, the electrolytic deposition filling said holes from the first conductive layer and overflowing on the second insulating layer, giving firstly to the conductive material deposited electrolytically the form of mushrooms whose hats rest on the second insulating layer, the electrolytic deposition being carried out to then grow, by coalescence of the mushroom caps formed in adjacent holes and sufficiently close, a mass of shape substantially half-cylindrical per set of adjacent holes and sufficiently close,
  • a step of depositing a second conductive layer intended to form the focusing grid, this second conductive layer being made of a material of a different nature from that of the electrolytically deposited conductive material,
  • a step of removing the conductive material electrolytically deposited, this elimination leaving, in the second conductive layer, a slit per mass previously formed and main axis aligned with the holes through which it has grown,
  • a step of deepening the holes to the cathodic connection means,
  • a step of etching the second insulating layer to reveal the first conductive layer,
  • a step of forming the microtips on the cathodic connection means revealed by the step of deepening the holes.

L'étape d'approfondissement des trous peut être réalisée par gravure. Cette étape ainsi que l'étape de gravure de la deuxième couche isolante peuvent être menées simultanément.The step of deepening the holes can be performed by etching. This step and the step of etching the second insulating layer can be conducted simultaneously.

L'invention a en outre pour objet un procédé de fabrication d'une source d'électrons à micropointes et à grille de focalisation comprenant :

  • une étape où l'on dépose successivement sur une face d'un support électriquement isolant : des moyens de connexion cathodiques, une première couche isolante électriquement d'épaisseur adaptée à la hauteur des futures micropointes, une première couche conductrice destinée à former la grille d'extraction, une deuxième couche isolante électriquement d'épaisseur correspondant à la distance devant séparer la grille d'extraction de la grille de focalisation, une couche de masquage,
  • une étape consistant à percer des trous au travers de l'ensemble constitué par la couche de masquage, la deuxième couche isolante et la première couche conductrice jusqu'à atteindre la première couche isolante, les axes des trous correspondant aux axes des futures micropointes, le diamètre de ces trous étant adapté à la taille des futures micropointes,
  • une étape d'approfondissement des trous dans la première couche isolante jusqu'aux moyens de connexion cathodiques,
  • une étape de gravure latérale de la deuxième couche isolante pour augmenter le diamètre des trous percés précédemment jusqu'à une valeur déterminée, cette gravure latérale pouvant rendre sécants des trous adjacents et suffisamment proches,
  • une étape d'enlèvement de la couche de masquage,
  • une étape de dépôt électrolytique de matériau conducteur dans lesdits trous, la première couche conductrice servant d'électrode au cours de l'électrolyse, le dépôt électrolytique remplissant lesdits trous à partir de la première couche conductrice et débordant sur la deuxième couche isolante en donnant d'abord au matériau conducteur déposé électrolytiquement la forme de champignons dont les chapeaux reposent sur la deuxième couche isolante, le dépôt électrolytique étant mené pour faire croître ensuite, par coalescence des chapeaux de champignons formés dans des trous adjacents et suffisamment proches, une masse de forme sensiblement demi-cylindrique par ensemble de trous adjacents et suffisamment proches,
  • une étape de dépôt d'une deuxième couche conductrice destinée à former la grille de focalisation, cette deuxième couche conductrice étant en un matériau de nature différente de celle du matériau conducteur déposé électrolytiquement,
  • une étape d'élimination du matériau conducteur déposé électrolytiquement, cette élimination laissant, dans la deuxième couche conductrice, une fente par masse précédemment formée et d'axe principal aligné sur les trous par lesquels elle a crû,
  • une étape de formation des micropointes sur les moyens de connexion cathodiques au travers des trous qui ont été réalisés dans la première couche conductrice et la première couche isolante.
The invention further relates to a method of manufacturing a micropoint electron source and focusing gate comprising:
  • a step where one successively deposits on one face of an electrically insulating support: cathodic connection means, a first electrically insulating layer of thickness adapted to the height of the future microtips, a first conductive layer intended to form the grid of extraction, a second electrically insulating layer of thickness corresponding to the distance to separate the extraction grid from the focusing grid, a masking layer,
  • a step of drilling holes through the assembly consisting of the masking layer, the second insulating layer and the first conductive layer to reach the first insulating layer, the axes of the holes corresponding to the axes of the future microtips, the diameter of these holes being adapted to the size of the future microtips,
  • a step of deepening the holes in the first insulating layer to the cathodic connection means,
  • a step of etching the second insulating layer laterally to increase the diameter of the previously drilled holes to a predetermined value, this lateral etching being able to make intersecting holes adjacent and sufficiently close,
  • a step of removing the masking layer,
  • a step of electrolytic deposition of conductive material in said holes, the first conductive layer serving as an electrode during the electrolysis, the electrolytic deposition filling said holes from the first conductive layer and overflowing on the second insulating layer, giving firstly to the conductive material deposited electrolytically the form of mushrooms whose hats rest on the second insulating layer, the electrolytic deposition being carried out to then grow, by coalescence of the mushroom caps formed in adjacent holes and sufficiently close, a mass of shape substantially half-cylindrical per set of adjacent holes and sufficiently close,
  • a step of depositing a second conductive layer intended to form the focusing grid, this second conductive layer being in a material of a different nature from that of the electrolytically deposited conductive material,
  • a step of removing the conductive material electrolytically deposited, this elimination leaving, in the second conductive layer, a slit per mass previously formed and main axis aligned with the holes through which it has grown,
  • a step of forming the microtips on the cathodic connection means through the holes that have been made in the first conductive layer and the first insulating layer.

L'étape d'approfondissement des trous dans la première couche isolante et l'étape de gravure latérale de la deuxième couche isolante peuvent être menées simultanément et effectuées par gravure isotrope.The deepening step of the holes in the first insulating layer and the step of lateral etching of the second insulating layer may be carried out simultaneously and carried out by isotropic etching.

Quel que soit le procédé mis en oeuvre, l'étape consistant à percer des trous peut être réalisée par gravure. L'étape d'élimination du matériau conducteur déposé électrolytiquement peut être réalisée par dissolution chimique. Les moyens de connexion cathodiques peuvent être obtenus par un dépôt de conducteurs cathodiques sur le support, suivi d'un dépôt d'une couche résistive.Whatever the method used, the step of drilling holes can be performed by etching. The elimination step of the electrolytically deposited conductive material can be carried out by chemical dissolution. The cathodic connection means can be obtained by deposition of cathode conductors on the support, followed by a deposit of a resistive layer.

Brève description des figuresBrief description of the figures

L'invention sera mieux comprise et d'autres avantages et particularités apparaîtront dans la description qui va suivre, donnée à titre d'exemple non limitatif, accompagnée des dessins annexés parmi lesquels :

  • la figure 1 est illustrative d'un écran plat à micropointes selon l'art connu,
  • la figure 2 est illustrative d'un écran plat à micropointes et à grille de focalisation selon l'art connu,
  • la figure 3 est une vue partielle et en perspective d'une première variante de source d'électrons à micropointes selon la présente invention,
  • la figure 4 est une vue partielle et en perspective d'une deuxième variante de source d'électrons à micropointes selon la présente invention,
  • les figures 5A à 5D sont illustratives d'un procédé de fabrication d'une source d'électrons à micropointes du type représenté à la figure 3,
  • les figures 6A à 6E sont illustratives d'un procédé de fabrication d'une source d'électrons à micropointes du type représenté à la figure 4,
  • la figure 7 est une vue de dessus d'une première source d'électrons à micropointes pour écran plat de visualisation selon la présente invention, cette vue ne montrant qu'une partie de la source d'électrons correspondant à un pixel de l'écran,
  • la figure 8 est une vue de dessus d'une deuxième source d'électrons à micropointes pour écran plat de visualisation selon la présente invention, cette vue ne montrant qu'une partie de la source d'électrons correspondant à un pixel de l'écran.
The invention will be better understood and other advantages and particularities will appear in the description which follows, given by way of nonlimiting example, accompanied by the appended drawings among which:
  • FIG. 1 is illustrative of a microtip flat screen according to the prior art,
  • FIG. 2 is illustrative of a flat screen with microtips and focusing grid according to the prior art,
  • FIG. 3 is a partial view in perspective of a first variant of electron source with microtips according to the present invention,
  • FIG. 4 is a partial view in perspective of a second variant of micropoint electron source according to the present invention,
  • FIGS. 5A to 5D are illustrative of a method of manufacturing a microtip electron source of the type shown in FIG. 3,
  • FIGS. 6A to 6E are illustrative of a method for manufacturing a microtip electron source of the type shown in FIG. 4,
  • FIG. 7 is a top view of a first microtip electron source for a flat screen display according to the present invention, this view showing only a part of the electron source corresponding to a pixel of the screen; ,
  • FIG. 8 is a view from above of a second microtip electron source for a flat display screen according to the present invention, this view showing only a part of the electron source corresponding to a pixel of the screen; .

Description détaillée de modes de réalisation de l'inventionDETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

La figure 3 est une vue partielle et en coupe d'une source d'électrons à micropointes selon l'invention. Elle a été élaborée à partir d'un support en verre 40. Sur ce support 40, on a successivement déposé une première couche 41 formant des moyens de connexion cathodiques, une première couche isolante 42 et une première couche conductrice 43. Dans les couches 42 et 43, on a gravé des trous 44 jusqu'à la première couche 41. Des émetteurs d'électrons 45, en forme de pointes, ont été déposés à l'intérieur des trous 44 et en contact avec la première couche 41. Les micropointes 45 sont disposées en alignements. Pour une utilisation de la source d'électrons comme cathode d'un écran plat de visualisation en couleurs, les alignements de micropointes sont parallèles aux bandes de luminophores disposées sur l'anode de l'écran.Figure 3 is a partial view in section of a micropoint electron source according to the invention. It was developed from a glass support 40. On this support 40, a first layer 41 forming cathodic connection means, a first insulating layer 42, was successively deposited. and a first conductive layer 43. In the layers 42 and 43, holes 44 have been etched to the first layer 41. Point-shaped electron emitters 45 have been deposited within the holes 44. and in contact with the first layer 41. The microtips 45 are arranged in alignments. For use of the electron source as a cathode of a flat color display, the microtip alignments are parallel to the phosphor strips disposed on the anode of the screen.

La couche conductrice 43 sert de grille d'extraction des électrons. Elle est recouverte d'une couche isolante 46 (deuxième couche isolante) et d'une couche conductrice 47 (deuxième couche conductrice). Des fentes 48 ont été réalisées dans les couches 46 et 47 jusqu'à atteindre la grille d'extraction 43. Les axes des fentes 48 sont confondus avec les axes des alignements d'émetteurs ou micropointes 45. Les fentes 48 peuvent avoir une largeur de 8 à 10 µm. Le pas des fentes (selon leur axe principal), et en conséquence le pas des lignes d'émetteurs, est de 10 à 12 µm. La distance entre deux émetteurs d'une même ligne est de l'ordre de 3 µm. La solution proposée par l'invention permet donc d'avoir une densité d'émetteurs qui est 3 à 4 fois plus élevée que dans le cas où la focalisation est réalisée dans toutes les directions de chacun des émetteurs (cas de la figure 2).The conductive layer 43 serves as an electron extraction grid. It is covered with an insulating layer 46 (second insulating layer) and a conductive layer 47 (second conductive layer). Slots 48 have been made in the layers 46 and 47 until reaching the extraction grid 43. The axes of the slits 48 coincide with the axes of the emitter or microtip alignments 45. The slits 48 may have a width of 8 to 10 μm. The pitch of the slots (along their main axis), and consequently the pitch of the emitter lines, is 10 to 12 μm. The distance between two emitters of the same line is of the order of 3 μm. The solution proposed by the invention therefore makes it possible to have an emitter density which is 3 to 4 times higher than in the case where the focusing is carried out in all the directions of each of the emitters (case of FIG. 2).

La source d'électrons à micropointes représentée à la figure 3 est généralement destinée à être utilisée comme cathode d'un écran plat de visualisation. Cet écran plat est un dispositif constitué d'une structure cathodique et d'une structure anodique en vis-à-vis, entre lesquelles on a fait le vide. La distance séparant la grille d'extraction 43 de la grille de focalisation 47 est très faible. Dans certains cas d'utilisation, il pourrait en résulter un risque d'arc électrique dans le vide entre ces deux grilles.The micropoint electron source shown in Figure 3 is generally intended to be used as a cathode of a flat display panel. This flat screen is a device consisting of a cathode structure and an anodic structure vis-à-vis, between which was evacuated. The distance separating the extraction grid 43 from the focusing grid 47 is very small. In some use cases, it could result in a risk of arc in the vacuum between these two grids.

Une solution pour remédier à cet inconvénient est représentée à la figure 4 où les mêmes éléments que pour la figure 3 sont désignés par les mêmes références. Dans le cas de la figure 4, les fentes 48 ont été limitées à la grille de focalisation. La couche isolante 46 a été gravée de fentes 49 centrées sur les lignes d'émetteurs correspondantes et de largeur inférieure à la largeur des fentes 48. A titre de variante, la couche isolante 46 peut être percée de trous concentriques aux trous 44. Le diamètre de ces trous concentriques ou la largeur des fentes 49, selon le cas, peut être de deux à trois fois le diamètre des trous 44. Ainsi, le prolongement de la couche isolante 46 sur la grille d'extraction 43 assure une meilleure protection contre les arcs électriques.A solution to overcome this drawback is shown in Figure 4 where the same elements as for Figure 3 are designated by the same references. In the case of FIG. 4, the slots 48 have been limited to the focusing grid. The insulating layer 46 has been etched with slots 49 centered on the corresponding emitter lines and of width less than the width of the slits 48. Alternatively, the insulating layer 46 may be pierced with concentric holes in the holes 44. The diameter of these concentric holes or the width of the slots 49, as the case may be, may be two to three times the diameter of the holes 44. Thus, the extension of the insulating layer 46 on the extraction grid 43 provides better protection against electric arcs.

Les électrons émis par les micropointes correspondant à une fente de grille de focalisation d'une source d'électrons selon la présente invention sont focalisés dans la direction perpendiculaire à l'axe de la fente. Ils ne s'écartent que très peu du plan perpendiculaire à la source et passant par l'axe de la fente. Les impacts de ces électrons sur un plan parallèle à la cathode sont donc situés dans une bande étroite parallèle à l'axe de la fente mais un peu plus longue que celle-ci.The electrons emitted by the microtips corresponding to a focusing gate slot of an electron source according to the present invention are focused in the direction perpendicular to the axis of the slot. They deviate very little from the plane perpendicular to the source and passing through the axis of the slot. The impacts of these electrons on a plane parallel to the cathode are therefore located in a narrow band parallel to the axis of the slot but a little longer than this.

Les sources d'électrons telles que représentées aux figures 3 et 4 peuvent être réalisées en utilisant des techniques de dépôt, de photolithographie et de gravure classiques en microélectronique, les micropointes étant réalisées selon l'art connu. Cependant, les calculs de simulation montrent que la qualité de la focalisation dépend du centrage de la grille de focalisation suivant l'axe des émetteurs et que ce paramètre est très sensible. La précision requise nécessite l'utilisation d'appareils très performants qui seront d'autant moins adaptés que la taille des écrans à réaliser augmente.The electron sources as represented in FIGS. 3 and 4 can be produced by using conventional deposition, photolithography and etching techniques in microelectronics, the microtips being produced according to the known art. However, simulation calculations show that the quality of the focus depends on the centering of the focusing grid along the axis of the emitters and that this parameter is very sensitive. The required accuracy requires the use of high performance devices that will be less suitable as the size of the screens to achieve increases.

Pour remédier à ce problème, il est proposé de réaliser la grille de focalisation par un procédé d'auto-alignement.To remedy this problem, it is proposed to make the focusing grid by a self-alignment process.

Un premier exemple de ce procédé est illustré par les figures 5A à 5D. Il permet d'obtenir une source d'électrons à micropointes du type de celle représentée à la figure 3.A first example of this method is illustrated in FIGS. 5A to 5D. It provides a microtip electron source of the type shown in FIG.

En se référant à la figure 5A, on a déposé sur une lame de verre 50 une couche métallique qui a été gravée pour constituer des colonnes 51. Une couche résistive 52 a ensuite été déposée de manière uniforme et de manière à présenter une surface plane. Sur la couche résistive 52, on a déposé ensuite successivement une première couche isolante 53, une couche conductrice 54 et une deuxième couche isolante 55. L'épaisseur de ces différentes couches est adaptée à la structure désirée. Les couches isolantes 53 et 55 peuvent être en silice. La couche conductrice 54, destinée à former la grille d'extraction des électrons peut être en niobium.Referring to FIG. 5A, a metal layer was deposited on a glass slide 50 which has been etched to form columns 51. A resistive layer 52 has then been uniformly deposited and has a flat surface. On the resistive layer 52, a first insulating layer 53, a conductive layer 54 and a second insulating layer 55 are successively deposited. The thickness of these different layers is adapted to the desired structure. Insulating layers 53 and 55 may be silica. The conductive layer 54 intended to form the electron extraction grid may be made of niobium.

Ensuite, par des techniques classiques de photolithographie et de gravure, on grave dans la couche isolante 55 des trous 56 dont les centres sont alignés sur des droites parallèles entre elles. Les trous 56 révèlent la couche conductrice 54. La distance entre deux trous successifs d'une même ligne est de l'ordre de 3 µm. La distance entre deux lignes consécutives est d'environ 10 à 12 µm. Par souci de clarté, on n'a représenté sur la figure 5A qu'une petite partie d'une seule ligne de trous.Then, by conventional photolithography and etching techniques, holes 56 are engraved in the insulating layer 55, the centers of which are aligned on lines parallel to each other. The holes 56 reveal the conductive layer 54. The distance between two successive holes of the same line is of the order of 3 microns. The distance between two consecutive lines is about 10 to 12 μm. For the sake of clarity, only a small portion of a single line of holes is shown in FIG.

L'étape suivante (voir la figure 5B) consiste à effectuer un dépôt électrolytique d'un matériau conducteur (par exemple un alliage fer-nickel) sur les parties révélées de la couche conductrice 54, c'est-à-dire au fond des trous 56. L'épaisseur du dépôt électrolytique est ajusté de façon à obtenir, pour chaque trou, la croissance d'un champignon dont le pied remplit le trou et tel que le chapeau se développe sur la face externe de la couche isolante 55. La croissance est poursuivie jusqu'à ce que le diamètre du chapeau atteigne la largeur désirée pour la fente de la grille de focalisation. Cette largeur étant environ de 10 µm, les champignons vont coalescer pour constituer une masse 57 en forme de demi-cylindre de diamètre égal à la largeur désirée de la fente.The next step (see FIG. 5B) consists in electrolytic deposition of a conductive material (for example an iron-nickel alloy) on the revealed portions of the conductive layer 54, that is to say at the bottom of the holes 56. The thickness of the electrolytic deposit is adjusted so as to obtain, for each hole, the growth of a mushroom whose foot fills the hole and such that the cap develops on the outer face of the insulating layer 55. Growth is continued until the diameter of the cap reaches the desired width for the slot of the focusing grid. This width being approximately 10 microns, the mushrooms will coalesce to form a mass 57 in the form of a half-cylinder with a diameter equal to the desired width of the slot.

On dépose ensuite, par une technique de dépôt sous vide adaptée à la nature du matériau à déposer, une seconde couche conductrice afin de former la grille de focalisation. Cette seconde couche conductrice (en métal ou en un autre matériau résistif) se dépose sur la couche isolante 55 entre les masses 57, pour constituer le dépôt 58, et sur les masses 57 pour constituer le dépôt 59, comme cela est représenté sur la figure 5B. Chaque masse 57 sert de masque pour l'ouverture de la grille de focalisation. Comme l'axe de chaque demi-cylindre formant une masse passe par la ligne qui joint les centres des trous, l'ouverture obtenue sera automatiquement centrée sur cette ligne.Then, by a vacuum deposition technique adapted to the nature of the material to be deposited, a second conductive layer is deposited in order to form the focusing grid. This second conductive layer (made of metal or another resistive material) is deposited on the insulating layer 55 between the masses 57, to constitute the deposit 58, and on the masses 57 to constitute the deposit 59, as shown in FIG. 5B. Each mass 57 serves as a mask for opening the focusing grid. As the axis of each half-cylinder forming a mass passes through the line joining the centers of the holes, the resulting opening will be automatically centered on this line.

Les masses 57 sont ensuite dissoutes chimiquement et on obtient la structure représentée à la figure 5C. Les ouvertures 60 pratiquées dans la grille de focalisation 58 sont centrées sur les axes des trous 56.The masses 57 are then chemically dissolved and the structure shown in FIG. 5C is obtained. The openings 60 made in the focusing grid 58 are centered on the axes of the holes 56.

La couche métallique 54 est ensuite gravée de manière anisotrope au travers des trous 56 pour approfondir ce trou jusqu'à la première couche isolante 53. La gravure anisotrope est poursuivie dans la couche isolante 53 jusqu'à atteindre la couche résistive 52. Les couches isolantes 53 et 55 étant toutes deux en silice dans l'exemple décrit, la gravure de ces deux couches peut être effectuée simultanément. On obtient, comme le montre la figure 5D, des trous 61 et 64 (dans le prolongement des trous 56 de la figure 5C) traversant respectivement la couche conductrice 54 et la couche isolante 53. On obtient également une ouverture 62 en forme de fente dans la continuité de la fente 60.The metal layer 54 is then etched anisotropically through the holes 56 to deepen this hole to the first insulating layer 53. The anisotropic etching is continued in the insulating layer 53 until reaching the resistive layer 52. The insulating layers 53 and 55 are both made of silica in the example described, the etching both of these layers can be performed simultaneously. As shown in FIG. 5D, holes 61 and 64 (in the extension of the holes 56 in FIG. 5C) are obtained passing respectively through the conductive layer 54 and the insulating layer 53. A slot-like opening 62 is also obtained in FIG. the continuity of the slot 60.

Les micropointes 63 sont ensuite réalisées de manière classique, au fond des trous 61. Les micropointes, les trous de la grille d'extraction et les fentes de la grille de focalisation sont donc auto-alignés.The microtips 63 are then conventionally made at the bottom of the holes 61. The microtips, the holes of the extraction grid and the slots of the focusing grid are thus self-aligned.

Un deuxième exemple de procédé d'auto-alignement est illustré par les figures 6A à 6E. Il permet d'obtenir une source d'électrons à micropointes du type de celle représentée à la figure 4.A second example of a self-alignment method is illustrated in FIGS. 6A to 6E. It provides a microtip electron source of the type shown in FIG.

En se référant à la figure 6A, on a déposé sur une lame de verre 70, comme pour le premier exemple de procédé, des colonnes 71 de conducteurs cathodiques et une couche résistive 72. Sur la couche résistive 72, on a déposé ensuite successivement une première couche isolante 73, une couche conductrice 74 et une deuxième couche isolante 75 de même nature que la première couche isolante 73. Une couche de résine 85 a finalement été déposée. Le choix des épaisseurs des couches et des matières utilisées peut être le même que pour le premier exemple de procédé.Referring to FIG. 6A, columns 71 of cathode conductors and a resistive layer 72 were deposited on a glass slide 70, as in the first example of the method. On the resistive layer 72, a first insulating layer 73, a conductive layer 74 and a second insulating layer 75 of the same nature as the first insulating layer 73. A resin layer 85 has finally been deposited. The choice of the thicknesses of the layers and the materials used may be the same as for the first example of the method.

Des trous 76 ont été ouverts dans la couche de résine 85 qui sert de masque pour la gravure de la couche isolante 75 et de la couche conductrice 74. Les trous 76 sont donc approfondis jusqu'à atteindre la première couche isolante 73.Holes 76 have been opened in the resin layer 85 which serves as a mask for etching the insulating layer 75 and conducting layer 74. Holes 76 are thus deepened until reaching the first insulating layer 73.

On procède ensuite à la gravure chimique de la première couche isolante 73 de façon à prolonger les trous jusqu'à la couche résistive 72. En pratiquant une gravure isotrope, on obtient une surgravure importante et les trous 84 réalisés dans la première couche isolante vont avoir le profil montré sur la figure 6B. La deuxième couche isolante 75, étant de même nature que la première couche isolante 73, est gravée de manière identique. On obtient une augmentation du diamètre des trous 76, entre la couche conductrice 74 et la couche de résine 85, qui fournit des cavités 82. Cette augmentation de diamètre est égale à au moins deux fois l'épaisseur de la première couche isolante 73.The first insulating layer 73 is then chemically etched so as to extend the holes to the resistive layer 72. By performing an isotropic etching, a significant overgraving is obtained and the holes 84 made in the first insulating layer will have the profile shown in Figure 6B. The second insulating layer 75, being of the same nature as the first insulating layer 73, is etched identically. An increase in the diameter of the holes 76 is obtained between the conductive layer 74 and the resin layer 85, which provides cavities 82. This increase in diameter is equal to at least twice the thickness of the first insulating layer 73.

La figure 6C représente la structure obtenue après enlèvement de la couche de résine. La deuxième couche isolante 75 présente des trous 82 coaxiaux avec les trous 76 de la couche conductrice 74 mais de plus grand diamètre. Ces trous 82 peuvent être isolés ou sécants (ce que montre la figure 6C) suivant l'épaisseur de la première couche isolante 73 et la distance entre les trous 76 d'une même ligne de trous.Figure 6C shows the structure obtained after removal of the resin layer. The second insulating layer 75 has holes 82 coaxial with the holes 76 of the conductive layer 74 but of larger diameter. These holes 82 may be insulated or secant (as shown in Figure 6C) following the thickness of the first insulating layer 73 and the distance between the holes 76 of the same line of holes.

On réalise ensuite un dépôt électrolytique d'un matériau conducteur à partir de la couche conductrice 74. L'étape de dépôt est menée de façon à obtenir des masses 77 en forme de demi-cylindre, de diamètre égal à la largeur désirée pour la fente de la grille de focalisation (par exemple 10 µm). C'est ce que montre la figure 6D.An electrolytic deposition of a conductive material is then carried out from the conductive layer 74. The deposition step is conducted so as to obtain masses 77 in the form of a half-cylinder, with a diameter equal to the desired width for the slot of the focusing grid (for example 10 μm). This is shown in Figure 6D.

Comme pour le premier exemple de procédé, on dépose une seconde couche conductrice afin de former la grille de focalisation. On obtient le dépôt 78 entre les masses 77, et le dépôt 79 sur les masses 77.As for the first example of the method, a second conductive layer is deposited to form the focusing grid. The deposit 78 is obtained between the masses 77 and the deposit 79 on the masses 77.

Les masses 77 sont ensuite dissoutes chimiquement pour conférer à la structure le profil représenté à la figure 6E. Les ouvertures 80 pratiquées dans la grille de focalisation 78 sont centrées sur les axes de trous 76. Cette grille 78 est posée sur la couche isolante 75 possédant elle-même une ouverture (constituée par la succession des trous adjacents 82) centrée sur la ligne des trous 76, l'ouverture dans la deuxième couche isolante 75 étant moins large que celle de la grille de focalisation 78.The masses 77 are then chemically dissolved to give the structure the profile shown in Figure 6E. The openings 80 made in the focusing grid 78 are centered on the axes of holes 76. This grid 78 is placed on the insulating layer 75 itself having an opening (constituted by the succession of adjacent holes 82) centered on the line of the holes. holes 76, the opening in the second insulating layer 75 being less wide than that of the focusing grid 78.

On réalise ensuite, de manière classique, les micropointes 83 au fond des trous 84. Les micropointes, les trous de la grille d'extraction et les fentes de la grille de focalisation sont donc auto-alignés.The microtips 83 are then conventionally carried out at the bottom of the holes 84. The microtips, the holes of the extraction grid and the slots of the focusing grid are thus self-aligned.

Vue de dessus, la source d'électrons à micropointes, par exemple obtenue par le premier exemple de procédé d'auto-alignement, peut se présenter comme le montrent les figures 7 et 8. Ces figures ne montrent qu'une partie de la source d'électrons correspondant à un pixel de l'écran. Les trous 61 de la grille d'extraction, au fond desquels sont placés les émetteurs d'électrons, sont alignés dans les fentes 60 de la grille de focalisation 58. Ces fentes peuvent faire la longueur du pixel, comme sur la figure 7. Elles peuvent être scindées en plusieurs parties, comme sur la figure 8.Viewed from above, the electron source with microtips, for example obtained by the first example of self-alignment process, may be as shown in Figures 7 and 8. These figures show only part of the source of electrons corresponding to a pixel of the screen. The holes 61 of the extraction grid, at the bottom of which are placed the electron emitters, are aligned in the slots 60 of the focusing grid 58. These slots can be the length of the pixel, as in FIG. can be divided into several parts, as in Figure 8.

Claims (14)

  1. Microtip electron source comprising:
    - at least one electron emission zone composed of a plurality of microtips (45, 63, 83) connected electrically to a cathode conductor (41, 51, 71),
    - at least one gate electrode (43, 54, 74), positioned opposite said electron emission zone and pierced with apertures (61) located opposite the microtips, to extract the electrons from the microtips,
    - an emitted electron focusing gate (47, 58, 78), positioned opposite the gate electrode, and comprising aperture means located opposite the microtips, characterized in that the aperture means of the focusing gate comprises at least one slit (48, 60, 80) located opposite at least two successive microtips,
    and in that the focusing gate (47, 58, 78) is separated from the extraction gate electrode (43, 54, 74) positioned opposite it by a layer of electrically insulating material (46, 55, 75) comprising a slit (48, 49, 62, 82) aligned with the slit (48, 60, 80) of the focusing gate (47, 58, 78), or a succession of holes aligned with the focusing gate slit, of a width less than that of the focusing gate slit.
  2. Microtip electron source according to claim 1, characterized in that it comprises a plurality of electron emission zones arranged in the form of a matrix in rows and columns, with the number of cathode conductors and gate electrodes corresponding to the rows and columns to give the microtip electron source a matric access.
  3. Microtip electron source according to claim 2, characterized in that each emission zone comprising several rows of microtips, each row of microtips has one or more corresponding slits (60) in the focusing gate (58).
  4. Device comprising a first and second plane structure maintained opposite and at a determined distance from each other by means forming a spacer, the first plane structure comprising, on its inner device face, a microtip electron source according to any of claims 1 to 3, and the second plane structure comprising, on its inner device face, means forming the anode.
  5. Flat display screen composed of a device according to claim 4, with luminophors placed between the microtip electron source and the means forming the anode.
  6. Flat display screen comprising a first and second plane structure maintained opposite and at a determined distance from each other by means forming a spacer, the first plane structure comprising, on its inner screen face, a microtip electron source according to claim 3, and the second plane structure comprising, on its inner screen face, a conductive layer forming the anode and supporting luminophors arranged in alternating red, green and blue bands, with each band located parallel to and opposite a series (row or column) of electron emission zones, with the main axis of the focusing gate slits directed in the direction of the luminophor bands and each emission zone defining a pixel for the display screen.
  7. Microtip and focusing gate electron source manufacturing process, comprising:
    - a step in which the following are successively deposited on one face of an electrically insulating substrate (50): cathode connection means (51, 52), a first electrically insulating layer (53) of a thickness adapted to the height of the future microtips, a first conductive layer (54) intended to form the extraction gate, a second electrically insulating layer (55) of a thickness corresponding to the distance to separate the extraction gate from the focusing gate,
    - a step consisting of piercing the second insulating layer (55) with holes (56) up to the first conductive layer (54), with the axes of the holes corresponding to the axes of the future microtips and the diameter of these holes adapted to the size of the future microtips,
    - an electrolytic deposition step of conductive material in said holes, with the first conductive layer (54) acting as the electrode during the electrolysis, the electrolytic deposit filling said holes (56) from the first conductive layer (54) and flowing onto the second insulating layer (55), first of all giving the electrolytically deposited conductive material the shape of mushrooms, the caps of which rest on the second insulating layer (55), with the electrolytic deposit subsequently producing, due to coalescence of the mushroom caps formed in adjacent and sufficiently close holes, an approximately semicylindrical shaped mass (57) for each set of adjacent and sufficiently close holes,
    - a deposition step of a second conductive layer (58, 59) intended to form the focusing gate, with the material of this second conductive layer being different to that of the electrolytically deposited conductive material,
    - an electrolytically deposited material removal step, with this removal leaving, in the second conductive layer (58), one slit (60) for each previously formed mass, the main axis of which is aligned with the holes (56) with which it was formed,
    - a deepening step of the holes (56) up to the cathode connection means (51, 52) ,
    - an etching step of the second insulating layer (55) to reveal the first conductive layer (54),
    - a microtip (63) formation step on the cathode connection means (51, 52) revealed by the hole deepening step.
  8. Process according to claim 7, characterized in that the hole deepening step is performed by etching.
  9. Process according to claim 8, characterized in that the hole deepening step and the etching step of the second insulating layer (55) are performed simultaneously.
  10. Microtip and focusing gate electron source manufacturing process, comprising:
    - a step in which the following are successively deposited on one face of an electrically insulating substrate (70): cathode connection means (71, 72), a first electrically insulating layer (73) of a thickness adapted to the height of the future microtips, a first conductive layer (74) intended to form the extraction gate, a second electrically insulating layer (75) of a thickness corresponding to the distance to separate the extraction gate from the focusing gate, a masking layer (85),
    - a step consisting of piercing holes (76) through the complex formed by the masking layer (85), the second insulating layer (75) up to the first conductive layer (73), with the axes of the holes (76) corresponding to the axes of the future microtips and the diameter of these holes adapted to the size of the future microtips,
    - a hole deepening step in the first insulating layer up to the cathode connection means (71, 72),
    - a lateral etching step of the second insulating layer (75) to increase the diameter of the holes pierced previously to a determined value, with this lateral etching being able to render adjacent and sufficiently close holes secant,
    - a masking layer (85) removal step,
    - an electrolytic deposition step of conductive material in said holes, with the first conductive layer (74) acting as the electrode during the electrolysis, the electrolytic deposit filling said holes from the first conductive layer (74) and flowing into the second insulating layer (75), first of all giving the electrolytically deposited conductive material the shape of mushrooms, the caps of which rest on the second insulating layer (75), with the electrolytic deposit subsequently producing, due to coalescence of the mushroom caps formed in adjacent and sufficiently close holes, an approximately semicylindrical shaped mass (77) for each set of adjacent and sufficiently close holes,
    - a deposition step of a second conductive layer (78, 79) intended to form the focusing gate, with the material of this second conductive layer being different to that of the electrolytically deposited conductive material,
    - an electrolytically deposited material removal step, with this removal leaving, in the second conductive layer (78), one slit (80) for each previously formed mass (77), the main axis of which is aligned with the holes with which it was formed,
    - a microtip (83) formation step on the cathode connection means (71, 72) through the holes (76) produced in the first conductive layer (74) and the first insulating layer (73).
  11. Process according to claim 10, characterized in that the hole deepening step in the first insulating layer (73) and the lateral etching step of the second insulating layer (75) are performed simultaneously by isotropic etching.
  12. Process according to any of claims 7 to 11, characterized in that the step consisting of piercing holes is performed by etching.
  13. Process according to any of claims 7 to 12, characterized in that the electrolytically deposited conductive material removal step is performed by chemical dissolution.
  14. Process according to any of claims 7 to 13, characterized in that the cathode connection means (51, 71) are obtained by deposition of cathode conductors on the substrate (50, 70), followed by deposition of a resistive layer (52, 72).
EP98949053A 1997-10-14 1998-10-13 Electron source with microtips, with focusing grid and high microtip density, and flat screen using same Expired - Lifetime EP1023741B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR9712826 1997-10-14
FR9712826A FR2769751B1 (en) 1997-10-14 1997-10-14 ELECTRON SOURCE WITH MICROPOINTS, WITH FOCUSING GRID AND HIGH DENSITY OF MICROPOINTS, AND FLAT SCREEN USING SUCH A SOURCE
PCT/FR1998/002197 WO1999019896A1 (en) 1997-10-14 1998-10-13 Electron source with microtips, with focusing grid and high microtip density, and flat screen using same

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EP1023741B1 true EP1023741B1 (en) 2006-06-14

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JP4219724B2 (en) * 2003-04-08 2009-02-04 三菱電機株式会社 Method for manufacturing cold cathode light emitting device
US7911123B2 (en) * 2005-07-04 2011-03-22 Samsung Sdi Co., Ltd. Electron emission device and electron emission display using the electron emission device
WO2007033247A2 (en) * 2005-09-14 2007-03-22 Littelfuse, Inc. Gas-filled surge arrester, activating compound, ignition stripes and method therefore
KR20070044175A (en) * 2005-10-24 2007-04-27 삼성에스디아이 주식회사 Electron emission element and electron emission device having the same
JP5403862B2 (en) * 2006-11-28 2014-01-29 チェイル インダストリーズ インコーポレイテッド Method for producing fine metal pattern

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FR2593953B1 (en) 1986-01-24 1988-04-29 Commissariat Energie Atomique METHOD FOR MANUFACTURING A DEVICE FOR VIEWING BY CATHODOLUMINESCENCE EXCITED BY FIELD EMISSION
FR2623013A1 (en) 1987-11-06 1989-05-12 Commissariat Energie Atomique ELECTRO SOURCE WITH EMISSIVE MICROPOINT CATHODES AND FIELD EMISSION-INDUCED CATHODOLUMINESCENCE VISUALIZATION DEVICE USING THE SOURCE
US5063327A (en) * 1988-07-06 1991-11-05 Coloray Display Corporation Field emission cathode based flat panel display having polyimide spacers
JP2653008B2 (en) * 1993-01-25 1997-09-10 日本電気株式会社 Cold cathode device and method of manufacturing the same
EP0614209A1 (en) * 1993-03-01 1994-09-07 Hewlett-Packard Company A flat panel display
TW272322B (en) * 1993-09-30 1996-03-11 Futaba Denshi Kogyo Kk
US5528103A (en) * 1994-01-31 1996-06-18 Silicon Video Corporation Field emitter with focusing ridges situated to sides of gate
US5543691A (en) * 1995-05-11 1996-08-06 Raytheon Company Field emission display with focus grid and method of operating same
FR2757999B1 (en) * 1996-12-30 1999-01-29 Commissariat Energie Atomique SELF-ALIGNMENT PROCESS THAT CAN BE USED IN MICRO-ELECTRONICS AND APPLICATION TO THE REALIZATION OF A FOCUSING GRID FOR FLAT SCREEN WITH MICROPOINTS
FR2779271B1 (en) * 1998-05-26 2000-07-07 Commissariat Energie Atomique METHOD FOR MANUFACTURING A MICROPOINT ELECTRON SOURCE WITH A SELF-ALIGNED FOCUSING GRID

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JP2001520437A (en) 2001-10-30
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EP1023741A1 (en) 2000-08-02
US6534913B1 (en) 2003-03-18
FR2769751B1 (en) 1999-11-12
JP4220122B2 (en) 2009-02-04
WO1999019896A1 (en) 1999-04-22
FR2769751A1 (en) 1999-04-16

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