EP0851451B1 - Process for self-aligning, usable in microelectronics and the use for the production of a focussing grid for a microtip flat display panel - Google Patents

Process for self-aligning, usable in microelectronics and the use for the production of a focussing grid for a microtip flat display panel Download PDF

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Publication number
EP0851451B1
EP0851451B1 EP97403163A EP97403163A EP0851451B1 EP 0851451 B1 EP0851451 B1 EP 0851451B1 EP 97403163 A EP97403163 A EP 97403163A EP 97403163 A EP97403163 A EP 97403163A EP 0851451 B1 EP0851451 B1 EP 0851451B1
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Prior art keywords
layer
insulating layer
conducting layer
small diameter
holes
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German (de)
French (fr)
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EP0851451A1 (en
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Aimé Perrin
Brigitte Montmayeul
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/022—Manufacture of electrodes or electrode systems of cold cathodes
    • H01J9/025—Manufacture of electrodes or electrode systems of cold cathodes of field emission cathodes

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  • the present invention relates to a self-alignment method usable in microelectronics for get alignment of holes formed at different levels. This process applies in particular to the realization of a screen focusing grid microtip dish.
  • each levels should be positioned relative to the previous thanks to alignment marks judiciously placed. This method is difficult of use if one of the levels requires a very great positioning accuracy and it becomes unusable if one of the levels consists of patterns arranged randomly.
  • a microelectronic structure that requires very high precision in the positioning of its different levels is constituted by a flat screen to microtips.
  • Documents FR-A-2 593 953 and FR-A-2 623 013 disclose such devices visualization by cathodoluminescence excited by field emission. These devices include a electron source with microtip emissive cathodes.
  • FIG. 1 is a view in cross section of such a display screen at microtips.
  • the screen consists of a cathode 1, which is a flat structure, arranged opposite to another planar structure forming the anode 2.
  • the cathode 1 and anode 2 are separated by a space in which there is empties.
  • the cathode 1 comprises a substrate of glass 11 on which the conductor level 12 is deposited in contact with the electron emitting tips 13.
  • the conductive level 12 is covered with a layer insulating 14, for example made of silica, itself covered with a conductive layer 15.
  • Anode 2 includes a transparent substrate 21 covered with a transparent electrode 22 on which are deposited luminescent phosphors 23.
  • 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 from the points 13 and are attracted to the anode 2.
  • the trajectories of the electrons are included in a cone of half angle at the top ⁇ depending on different parameters, among others of the shape of the tips 13. This angle causes a defocus of the beam of electrons 31 all the more important as the distance between the anode and the cathode is large.
  • One of the ways to increase the yield of phosphorus so the screen brightness is to work with higher anode-cathode voltages (between 1000 and 5000 V), which involves spreading the anode further and the cathode to avoid the formation of an arc electric between these two electrodes.
  • the electron beam must be refocused.
  • This refocusing is conventionally obtained thanks to a grid which can either be placed between the anode and the cathode, is disposed on the cathode.
  • Figure 2 illustrates the case where the grid focusing is arranged on the cathode.
  • Figure 2 takes again the example of figure 1 but limited to one single microtip for clarity in the drawing.
  • An insulating layer 16 has been deposited on the grid extraction 15 and supports a metal layer 17 serving as a focus grid. Holes 19, of adequate diameter (typically between 8 and 10 ⁇ m) and concentric with holes 18, have been engraved in the layers 16 and 17.
  • the insulating layer 16 is used to insulate electrically the extraction grid 15 and the grid of focus 17.
  • the focus grid is polarized with respect to the anode so as to give the electron beam 32 the shape shown in the figure 2.
  • the method according to the invention makes it possible to obtain aligning holes formed at different levels. he is particularly recommended for making the grid focusing a flat screen with microtips.
  • This method consists in carrying out, on the structure concerned, the mask corresponding to a level from patterns from the previous level, which allows you to self-alignment of this level with respect to previous. After completion of the level considered (usually a deposit or an engraving), the mask is removed by dissolution for example.
  • This layer of a material of a different nature than that of the electrolytically deposited conductive material can be deposited using a deposition technique vacuum adapted to the nature of the material (evaporation, cathode sputtering, ).
  • This layer of a material of a different nature than that of the electrolytically deposited conductive material can be deposited using a deposition technique vacuum adapted to the nature of the material (evaporation, cathode sputtering, ).
  • the deepening stages of small diameter and large diameter holes are carried out simultaneously.
  • the following description will focus on the realization of a microtip cathode provided with an electron focusing grid. Through for simplicity, the following drawings do not will show only one microtip although the invention allows the simultaneous realization of a plurality of microtips.
  • the screen is of the access type matrix, the column electrodes being arranged on the cathode.
  • Figure 3A is a cross-sectional view. It illustrates the preparatory stages of training of a microtip cathode.
  • a glass slide 41 supports a metallic layer, which has been deposited on the blade and etched to form columns 42, and a resistive layer 43. These different layers are filed in a conventional manner.
  • an insulating layer 44 On the resistive layer 43, we deposit successively (see Figure 3B) an insulating layer 44, a conductive layer 45 and an insulating layer 46.
  • the insulating layers 44 and 46 may be in silica.
  • the conductive layer 45 can be made of niobium. It is intended to form the extraction grid for electrons.
  • the next step is to burn holes in the insulating layer 46. These holes can be obtained thanks to a photomask or a network of microbeads.
  • a resin layer is deposited on the insulating layer 46. This resin layer is exposed through a mask. After development, the insulating layer 46 is etched to the metal layer 45. Then the remaining resin is dissolved.
  • FIG. 3C where a single hole 47 is represented.
  • the next step is an essential step in present invention.
  • a material conductor for example an iron-nickel alloy
  • the thickness of the deposit electrolytic is adjusted so as to obtain, in each hole 47, a mushroom 50 (see FIG. 3D) such that the foot 51 of the mushroom fills the hole 47 and as the cap 52 develops on the face upper layer of insulating layer 46 until the diameter of the cap 52 reaches the desired diameter of focus grid hole.
  • the conductive layer forming the grid focusing 55 can be made of a metal or a other slightly conductive material, for example a metal oxide.
  • the structure of cathode by etching the metal layer 45 and the insulating layer 44 until reaching the layer resistive 43.
  • the insulating layers 44 and 46 being both in silica, in the example described, the etching of the insulating layer 44 and etching of the insulating layer 46 can be performed simultaneously.
  • the cathode tips 60. Once this step is completed, the cathode is finished. Its transmitters (spikes), its extraction grid and its focus grid are self-aligned (see Figure 3H).

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Cold Cathode And The Manufacture (AREA)
  • Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)

Description

La présente invention concerne un procédé d'auto-alignement utilisable en micro-électronique pour obtenir l'alignement de trous formés à différents niveaux. Ce procédé s'applique en particulier à la réalisation d'une grille de focalisation pour écran plat à micropointes.The present invention relates to a self-alignment method usable in microelectronics for get alignment of holes formed at different levels. This process applies in particular to the realization of a screen focusing grid microtip dish.

Lorsqu'une structure micro-électronique nécessite pour sa réalisation plusieurs niveaux comportant un motif ou un ensemble de motifs et que ces niveaux sont réalisés par des techniques de photomasquage, chacun des niveaux doit être positionné par rapport au précédent grâce à des marques d'alignement judicieusement placées. Cette méthode est difficile d'utilisation si l'un des niveaux demande une très grande précision de positionnement et elle devient inutilisable si l'un des niveaux est constitué de motifs disposés de façon aléatoire.When a microelectronic structure requires for its realization several levels including a pattern or set of patterns and that these levels are made by photomasking techniques, each levels should be positioned relative to the previous thanks to alignment marks judiciously placed. This method is difficult of use if one of the levels requires a very great positioning accuracy and it becomes unusable if one of the levels consists of patterns arranged randomly.

Une structure micro-électronique qui exige une très grande précision dans le positionnement de ses différents niveaux est constituée par un écran plat à micropointes. Les documents FR-A-2 593 953 et FR-A-2 623 013 divulguent de tels dispositifs de visualisation par cathodoluminescence excitée par émission de champ. Ces dispositifs comprennent une source d'électrons à cathodes émissives à micropointes.A microelectronic structure that requires very high precision in the positioning of its different levels is constituted by a flat screen to microtips. Documents FR-A-2 593 953 and FR-A-2 623 013 disclose such devices visualization by cathodoluminescence excited by field emission. These devices include a electron source with microtip emissive 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 23.By way of illustration, FIG. 1 is a view in cross section of such a display screen at microtips. For the sake of simplification, only some aligned microtips have been shown. The screen consists of a cathode 1, which is a flat structure, arranged opposite to another planar structure forming the anode 2. The cathode 1 and anode 2 are separated by a space in which there is empties. The cathode 1 comprises a substrate of glass 11 on which the conductor level 12 is deposited in contact with the electron emitting tips 13. The conductive level 12 is covered with a layer insulating 14, for example made of silica, itself covered with a conductive layer 15. Holes 18, about 1.3 µm in diameter, were made at through layers 14 and 15 to the conductive level 12 to drop the tips 13 on this level driver. The conductive layer 15 serves as a grid of extraction for the electrons which will be emitted by the tips 13. Anode 2 includes a transparent substrate 21 covered with a transparent electrode 22 on which are deposited luminescent phosphors 23.

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  dépendant de différents paramètres, entre autres de la forme des pointes 13. Cet angle entraíne 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 1000 et 5000 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. 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, apply a positive voltage of a few tens of volts (typically 60 to 100 V) with respect to at the tips 13. Electrons are then torn from the points 13 and are attracted to the anode 2. The trajectories of the electrons are included in a cone of half angle at the top  depending on different parameters, among others of the shape of the tips 13. This angle causes a defocus of the beam of electrons 31 all the more important as the distance between the anode and the cathode is large. One of the ways to increase the yield of phosphorus so the screen brightness, is to work with higher anode-cathode voltages (between 1000 and 5000 V), which involves spreading the anode further and the cathode to avoid the formation of an arc electric between these two electrodes.

Si on désire conserver une bonne définition 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 cathode.If we want to keep a good definition on the anode, the electron beam must be refocused. This refocusing is conventionally obtained thanks to a grid which can either be placed between the anode and the cathode, is disposed 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 l'anode de façon à donner au faisceau d'électrons 32 la forme représentée à la figure 2.Figure 2 illustrates the case where the grid focusing is arranged on the cathode. Figure 2 takes again the example of figure 1 but limited to one single microtip for clarity in the drawing. An insulating layer 16 has been deposited on the grid extraction 15 and supports a metal layer 17 serving as a focus grid. Holes 19, of adequate diameter (typically between 8 and 10 µm) and concentric with holes 18, have been engraved in the layers 16 and 17. The insulating layer 16 is used to insulate electrically the extraction grid 15 and the grid of focus 17. The focus grid is polarized with respect to the anode so as to give the electron beam 32 the shape shown in the figure 2.

Des calculs de simulation montrent que le centrage des trous de la grille de focalisation par rapport à ceux de la grille d'extraction est extrêmement critique. La réalisation de la grille de focalisation par une technique classique de photomasquage devient alors très difficile, surtout pour de grandes surfaces d'écran. En outre, si les trous de la grille d'extraction sont faits en utilisant un réseau de microbilles, leur disposition est aléatoire, ce qui interdit l'utilisation d'un photomasque pour réaliser les trous de la grille de focalisation. Simulation calculations show that centering holes in the focus grid with respect to those of the extraction grid is extremely critical. The realization of the focus grid by a classic photomask technique becomes so very difficult, especially for large areas screen. Also, if the grid holes extraction are done using a network of microbeads, their arrangement is random, which prohibits the use of a photomask to carry out the holes of the focusing grid.

Le procédé selon l'invention permet d'obtenir l'alignement de trous formés à différents niveaux. Il est particulièrement recommandé pour réaliser la grille de focalisation d'un écran plat à micropointes. Ce procédé consiste à réaliser, sur la structure concernée, le masque correspondant à un niveau à partir des motifs du niveau précédent, ce qui permet d'avoir un auto-alignement de ce niveau par rapport au précédent. Après réalisation du niveau considéré (généralement un dépôt ou une gravure), le masque est enlevé par dissolution par exemple.The method according to the invention makes it possible to obtain aligning holes formed at different levels. he is particularly recommended for making the grid focusing a flat screen with microtips. This method consists in carrying out, on the structure concerned, the mask corresponding to a level from patterns from the previous level, which allows you to self-alignment of this level with respect to previous. After completion of the level considered (usually a deposit or an engraving), the mask is removed by dissolution for example.

L'invention a donc pour objet un procédé d'auto-alignement utilisable en micro-électronique pour obtenir l'alignement d'au moins un groupe de deux trous, l'un de ces trous (ou trou de grand diamètre) étant formé dans un niveau supérieur et l'autre de ces trous (ou trou de petit diamètre) étant formé dans un niveau inférieur d'une structure empilée, caractérisé en ce qu'il consiste à :

  • prévoir une couche conductrice dans la structure, ladite couche conductrice pouvant être connectée à un circuit électrique extérieur,
  • déposer une couche isolante sur ladite couche conductrice,
  • percer la couche isolante d'un trou dudit petit diamètre et atteignant ladite couche conductrice,
  • effectuer un dépôt électrolytique de matériau conducteur dans le trou de petit diamètre, la couche conductrice servant d'électrode au cours de l'électrolyse, le dépôt électrolytique remplissant le trou de petit diamètre à partir de la couche conductrice et débordant sur ladite couche isolante pour donner au matériau conducteur déposé électrolytiquement la forme d'un champignon dont le chapeau repose sur ladite couche isolante, le dépôt électrolytique étant mené jusqu'à ce que le diamètre du chapeau atteigne la dimension du grand diamètre,
  • déposer sur la structure obtenue une couche d'un matériau de nature différente de celle du matériau conducteur déposé électrolytiquement,
  • élimination du champignon, cette élimination laissant, dans la dernière couche déposée, un trou de grand diamètre aligné sur le trou de petit diamètre.
The subject of the invention is therefore a self-alignment method usable in microelectronics to obtain the alignment of at least one group of two holes, one of these holes (or large diameter hole) being formed in one upper level and the other of these holes (or small diameter hole) being formed in a lower level of a stacked structure, characterized in that it consists of:
  • providing a conductive layer in the structure, said conductive layer being able to be connected to an external electrical circuit,
  • depositing an insulating layer on said conductive layer,
  • pierce the insulating layer with a hole of said small diameter and reaching said conductive layer,
  • carrying out an electrolytic deposition of conductive material in the small diameter hole, the conductive layer serving as an electrode during electrolysis, the electrolytic deposition filling the small diameter hole from the conductive layer and overflowing on said insulating layer to give the conductive material electrolytically deposited in the form of a mushroom, the cap of which rests on said insulating layer, the electroplating being carried out until the diameter of the cap reaches the dimension of the large diameter,
  • depositing on the structure obtained a layer of a material of a different nature from that of the conductive material deposited electrolytically,
  • elimination of the fungus, this elimination leaving, in the last layer deposited, a large diameter hole aligned with the small diameter hole.

Cette couche d'un matériau de nature différente de celle du matériau conducteur déposé électrolytiquement peut être déposée à l'aide d'une technique de dépôt sous vide adaptée à la nature du matériau (évaporation, pulvérisation cathodique,...).This layer of a material of a different nature than that of the electrolytically deposited conductive material can be deposited using a deposition technique vacuum adapted to the nature of the material (evaporation, cathode sputtering, ...).

Le procédé peut comprendre en outre les étapes consistant à :

  • d'abord, approfondir le trou de petit diamètre jusqu'à un premier niveau déterminé,
  • ensuite approfondir le trou de grand diamètre jusqu'à un deuxième niveau déterminé compris entre la face supérieure de la couche isolante et le premier niveau déterminé.
The method can also include the steps of:
  • first, deepen the small diameter hole to a first determined level,
  • then deepen the large diameter hole to a second determined level between the upper face of the insulating layer and the first determined level.

L'invention a aussi pour objet un procédé d'auto-alignement de la grille de focalisation par rapport à la grille d'extraction dans une cathode à micropointes, les micropointes devant être formées sur un niveau conducteur, chaque micropointe devant être alignée avec un trou de petit diamètre de la grille d'extraction et avec un trou de grand diamètre de la grille de focalisation correspondants, le procédé comprenant :

  • une étape de dépôt d'une première couche isolante sur le niveau conducteur,
  • une étape de dépôt d'une première couche conductrice destinée à former la grille d'extraction sur la première couche isolante,
  • une étape de dépôt d'une deuxième couche isolante sur la première couche conductrice,
caractérisé en ce qu'il comprend en outre :
  • une étape consistant à percer la deuxième couche isolante de trous de petit diamètre atteignant la première couche conductrice,
  • une étape de dépôt électrolytique de matériau conducteur dans les trous de petit diamètre, la première couche conductrice servant d'électrode au cours de l'électrolyse, le dépôt électrolytique remplissant les trous de petit diamètre à partir de la première couche conductrice et débordant sur ladite deuxième couche isolante pour donner au matériau conducteur déposé électrolytiquement la forme de champignons dont les chapeaux reposent sur ladite deuxième couche isolante, le dépôt électrolytique étant mené jusqu'à ce que le diamètre des chapeaux atteigne la dimension du grand diamètre,
  • une étape de dépôt sur la structure obtenue 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 des champignons, cette élimination laissant, dans la deuxième couche conductrice, des trous de grand diamètre alignés sur les trous de petit diamètre,
  • une étape d'approfondissement des trous de petit diamètre jusqu'au niveau conducteur,
  • une étape d'approfondissement des trous de grand diamètre jusqu'à la première couche conductrice,
  • une étape de formation des micropointes.
A subject of the invention is also a method of self-alignment of the focusing grid with respect to the extraction grid in a microtip cathode, the microtips having to be formed on a conductive level, each microtip having to be aligned with a hole of small diameter of the extraction grid and with a hole of large diameter of the corresponding focusing grid, the method comprising:
  • a step of depositing a first insulating layer on the conductive level,
  • a step of depositing a first conductive layer intended to form the extraction grid on the first insulating layer,
  • a step of depositing a second insulating layer on the first conductive layer,
characterized in that it further comprises:
  • a step consisting in piercing the second insulating layer with small diameter holes reaching the first conductive layer,
  • a step of electrolytic deposition of conductive material in the holes of small diameter, the first conductive layer serving as an electrode during the electrolysis, the electrolytic deposition filling the holes of small diameter from the first conductive layer and overflowing on said second insulating layer to give the conductive material electrolytically deposited in the form of fungi, the caps of which rest on said second insulating layer, the electrolytic deposition being carried out until the diameter of the caps reaches the dimension of the large diameter,
  • a step of depositing on the structure obtained 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 conductive material deposited electrolytically,
  • a step of eliminating the fungi, this elimination leaving, in the second conductive layer, large diameter holes aligned with the small diameter holes,
  • a step of deepening small diameter holes up to the conductive level,
  • a step of deepening large diameter holes to the first conductive layer,
  • a microtip formation step.

Cette couche d'un matériau de nature différente de celle du matériau conducteur déposé électrolytiquement peut être déposée à l'aide d'une technique de dépôt sous vide adaptée à la nature du matériau (évaporation, pulvérisation cathodique,...).This layer of a material of a different nature than that of the electrolytically deposited conductive material can be deposited using a deposition technique vacuum adapted to the nature of the material (evaporation, cathode sputtering, ...).

De préférence, les étapes d'approfondissement des trous de petit diamètre et de grand diamètre sont menées simultanément.Preferably, the deepening stages of small diameter and large diameter holes are carried out simultaneously.

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

  • les figures 1 et 2 sont illustratives d'un écran plat à micropointes selon l'art connu,
  • les figures 3A à 3H sont illustratives du procédé selon la présente invention, appliqué à la réalisation d'une cathode à micropointes pourvue d'une grille de focalisation.
The invention will be better understood and other advantages and features will appear in the description which follows, given by way of nonlimiting example, accompanied by the appended drawings among which:
  • FIGS. 1 and 2 are illustrative of a flat screen with microtips according to the known art,
  • FIGS. 3A to 3H are illustrative of the method according to the present invention, applied to the production of a microtip cathode provided with a focusing grid.

A titre d'exemple , la suite de la description va porter sur la réalisation d'une cathode à micropointes pourvue d'une grille de focalisation d'électrons. Par souci de simplification, les dessins suivants ne montreront qu'une seule micropointe bien que l'invention permette la réalisation simultanée d'une pluralité de micropointes. L'écran est du type à accès matriciel, les électrodes colonne étant disposées sur la cathode.By way of example, the following description will focus on the realization of a microtip cathode provided with an electron focusing grid. Through for simplicity, the following drawings do not will show only one microtip although the invention allows the simultaneous realization of a plurality of microtips. The screen is of the access type matrix, the column electrodes being arranged on the cathode.

La figure 3A est une vue en coupe transversale. Elle illustre les étapes préparatoires de la formation d'une cathode à micropointes. Une lame de verre 41 supporte une couche métallique, qui a été déposée sur la lame et gravée pour constituer des colonnes 42, et une couche résistive 43. Ces différentes couches sont déposées de manière classique.Figure 3A is a cross-sectional view. It illustrates the preparatory stages of training of a microtip cathode. A glass slide 41 supports a metallic layer, which has been deposited on the blade and etched to form columns 42, and a resistive layer 43. These different layers are filed in a conventional manner.

Sur la couche résistive 43, on dépose successivement (voir la figure 3B) une couche isolante 44, une couche conductrice 45 et une couche isolante 46. Les couches isolantes 44 et 46 peuvent être en silice. La couche conductrice 45 peut être en niobium. Elle est destinée à former la grille d'extraction des électrons.On the resistive layer 43, we deposit successively (see Figure 3B) an insulating layer 44, a conductive layer 45 and an insulating layer 46. The insulating layers 44 and 46 may be in silica. The conductive layer 45 can be made of niobium. It is intended to form the extraction grid for electrons.

L'étape suivante consiste à graver des trous dans la couche isolante 46. Ces trous peuvent être obtenus grâce à un photomasque ou un réseau de microbilles. Dans le cas de l'utilisation d'un photomasque, une couche de résine est déposée sur la couche isolante 46. Cette couche de résine est insolée au travers d'un masque. Après développement, la couche isolante 46 est gravée jusqu'à la couche métallique 45. Ensuite la résine subsistante est dissoute. On obtient la structure illustrée par la figure 3C où un seul trou 47 est représenté.The next step is to burn holes in the insulating layer 46. These holes can be obtained thanks to a photomask or a network of microbeads. In the case of the use of a photomask, a resin layer is deposited on the insulating layer 46. This resin layer is exposed through a mask. After development, the insulating layer 46 is etched to the metal layer 45. Then the remaining resin is dissolved. We get the structure illustrated in FIG. 3C where a single hole 47 is represented.

L'étape suivante est une étape essentielle de la présente invention. Au cours de cette étape, on effectue un dépôt électrolytique d'un matériau conducteur (par exemple un alliage fer-nickel) sur les parties dégagées de la couche conductrice 45, c'est-à-dire au fond des trous 47. L'épaisseur du dépôt électrolytique est ajusté de façon à obtenir, dans chaque trou 47, un champignon 50 (voir la figure 3D) tel que le pied 51 du champignon remplisse le trou 47 et tel que le chapeau 52 se développe sur la face supérieure de la couche isolante 46 jusqu'à ce que le diamètre du chapeau 52 atteigne le diamètre désiré de trou de grille de focalisation.The next step is an essential step in present invention. During this step, we electroplates a material conductor (for example an iron-nickel alloy) on the exposed parts of the conductive layer 45, that is to say at the bottom of the holes 47. The thickness of the deposit electrolytic is adjusted so as to obtain, in each hole 47, a mushroom 50 (see FIG. 3D) such that the foot 51 of the mushroom fills the hole 47 and as the cap 52 develops on the face upper layer of insulating layer 46 until the diameter of the cap 52 reaches the desired diameter of focus grid hole.

On dépose ensuite (voir la figure 3E), par une technique de dépôt sous vide adaptée à la nature du matériau à déposer, une couche conductrice pour former la grille de focalisation 55 sur la face supérieure de la structure ainsi obtenue. Cette couche conductrice se dépose sur les chapeaux 52 des champignons 50 et sur les parties de la couche isolante 46 laissées libres par les champignons. Chaque chapeau de champignon sert alors de masque pour l'ouverture de la grille de focalisation 55, autour du trou 47. Cette ouverture se trouve alignée automatiquement sur le trou 47. On remarque que la partie 53 du chapeau 52, tangente à la couche conductrice formant la grille de focalisation 55 n'est pas ou pratiquement pas recouverte.Then deposit (see Figure 3E), by a vacuum deposition technique adapted to the nature of the material to be deposited, a conductive layer to form the focusing grid 55 on the upper face of the structure thus obtained. This conductive layer is deposits on the hats 52 mushrooms 50 and on the parts of the insulating layer 46 left free by mushrooms. Each mushroom cap serves then mask for opening the grid of focusing 55, around hole 47. This opening is is automatically aligned with hole 47. We note that the part 53 of the cap 52, tangent to the conductive layer forming the focusing grid 55 is not or practically not covered.

La couche conductrice formant la grille de focalisation 55 peut être constituée d'un métal ou d'un autre matériau légèrement conducteur, par exemple un oxyde métallique.The conductive layer forming the grid focusing 55 can be made of a metal or a other slightly conductive material, for example a metal oxide.

Les champignons sont ensuite dissous chimiquement par attaque à partir de la partie 53 du chapeau 52. On obtient alors, comme le montre la figure 3F, une grille de focalisation 55 dont les trous 56 sont auto-alignés avec les trous 47 de la couche isolante 46.The mushrooms are then dissolved chemically by attack from part 53 of hat 52. We then obtains, as shown in Figure 3F, a grid focusing 55 whose holes 56 are self-aligned with the holes 47 of the insulating layer 46.

On poursuit l'élaboration de la structure de cathode par gravure de la couche métallique 45 et de la couche isolante 44 jusqu'à atteindre la couche résistive 43. Les couches isolantes 44 et 46 étant toutes deux en silice, dans l'exemple décrit, la gravure de la couche isolante 44 et la gravure de la couche isolante 46 peuvent être effectuées simultanément. On obtient, comme le montre la figure 3G, un trou 47' au travers de la couche conductrice 45 et de la couche isolante 44 dans la continuité du trou 47, et un trou 56' dans la continuité du trou 56.The structure of cathode by etching the metal layer 45 and the insulating layer 44 until reaching the layer resistive 43. The insulating layers 44 and 46 being both in silica, in the example described, the etching of the insulating layer 44 and etching of the insulating layer 46 can be performed simultaneously. We get, as shown in the figure 3G, a hole 47 'through the conductive layer 45 and of the insulating layer 44 in the continuity of the hole 47, and a hole 56 ′ in the continuity of the hole 56.

Il reste à réaliser, de manière classique, les pointes 60 de la cathode. Une fois cette étape achevée, la cathode est terminée. Ses émetteurs (les pointes), sa grille d'extraction et sa grille de focalisation sont auto-alignés (voir la figure 3H).It remains to carry out, in a conventional manner, the cathode tips 60. Once this step is completed, the cathode is finished. Its transmitters (spikes), its extraction grid and its focus grid are self-aligned (see Figure 3H).

Claims (9)

  1. Self-alignment process usable in microelectronics to obtain alignment of at least one group of holes, one of said holes (or large diameter hole) being formed in an upper level and the other hole (or small diameter hole) being formed in a lower level of a stacked structure, consisting of:
    providing a conducting layer (45) in the structure, said conducting layer possibly being connected to an external electrical circuit,
    disposing an insulating layer (46) on said conducting layer (45),
    piercing the insulating layer (46) with a hole of said small diameter (47) that penetrates as far as the conducting layer (450,
    carrying out an electrolytic deposit of a conducting material in the small diameter hole (47) using the conducting layer (45) as the electrode during the electrolysis procedure, said electrolytic deposit filling the same diameter hole (47) from the conducting layer (45) and causing the deposit to overflow onto said insulating layer (46) to give the electrolytically deposited conducting material the shape of a mushroom (50) whose head (52) rests on said insulating layer, the electrolytic deposition being continued until the diameter of the mushroom head (52) attains the size of the large diameter,
    depositing on the structure thereby obtained a conducting layer (55) of a different type of material from the electrolytically deposited conducting material,
    removing the mushroom (50), thereby leaving a large diameter hole (56) aligned with a small diameter hole (57) in the last layer deposited.
  2. Process of claim 1, including the following steps:
    firstly deepen the small diameter hole (47, 47') to a given first level,
    then deepen the large diameter hole (56, 56') to a given second level that lies between the upper surface of the insulating layer (46) and the given first layer.
  3. Process according to either of the claims 1 and 2, characterized in that insulating layer (46) is pierced by etching.
  4. Process according to any one of the claims 1 to 3, characterized in that the mushroom (50) is removed by chemical dissolution.
  5. Process for self-aligning the focusing grid (55) with the extraction grid (45) in a micropoint cathode (60), said micropoints (60) being formed on a conducting layer (42, 43) and each micropoint (60) being aligned with a small diameter hole (47') in the extraction grid (45) and with a large diameter hole (56, 56') in the corresponding focusing grid (55), said process comprising:
    a stage in which a first insulating layer (44) is deposited on the conducting layer (42, 43),
    a stage in which a first conducting layer is deposited to form the extraction grid (45) on the first insulating layer (44),
    a stage in which a second insulating layer (46) is deposited on the first conducting layer (45), characterized by the fact that it also comprises:
    a stage that consists of piercing the second insulating layer (46) with small diameter holes (47) that penetrate as far as the first conducting layer (45),
    a stage in which a conducting material is electrolytically deposited in the small diameter holes (47), the first conducting layer (45) acting as the electrode during the electrolysis procedure, said electrolytic deposit filling the small diameter holes (47) beginning at the first conducting layer (450 and overflowing onto said second insulating layer (46) to give the electrolytically deposited conducting material the shape of mushrooms (50) whose heads (52) rest on said second insulating layer (46), the electrolytic deposition being continued until the diameter of the mushroom heads (52) attains the size of the large diameter,
    a stage in which a second conducting layer is deposited on the structure thereby obtained, said second conducting layer being designed to form the focusing grid (55) and made of a different type of material from the electrolytically deposited conducting material,
    a stage in which the mushrooms (50) are eliminated to leave large diameter holes (56) in the second conducting layer (55), said holes being aligned with the small diameter holes (47),
    a stage in which the small diameter holes (47') are deepened to reach the first conducting layer (42, 43),
    a stage in which the large diameter holes (56, 56') are deepened to reach the first conducting layer (45),
    a stage in which the micropoints (60) are formed.
  6. Process according to claim 5, characterized in that the small diameter holes (47') and the large diameter holes (56, 56') are deepened simultaneously.
  7. Process according to one of the claims 5 or 6, characterized in that the small diameter holes (47, 47') are obtained by etching.
  8. Process according to any one of the claims 5 to 7, characterized in that the large diameter holes (56') in the second insulating layer (46) are deepened by etching.
  9. Process according to any one of the claims 5 to 8, characterized in that the mushrooms are removed by chemical dissolving.
EP97403163A 1996-12-30 1997-12-24 Process for self-aligning, usable in microelectronics and the use for the production of a focussing grid for a microtip flat display panel Expired - Lifetime EP0851451B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9616196A FR2757999B1 (en) 1996-12-30 1996-12-30 SELF-ALIGNMENT PROCESS THAT CAN BE USED IN MICRO-ELECTRONICS AND APPLICATION TO THE REALIZATION OF A FOCUSING GRID FOR FLAT SCREEN WITH MICROPOINTS
FR9616196 1996-12-30

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EP0851451A1 EP0851451A1 (en) 1998-07-01
EP0851451B1 true EP0851451B1 (en) 2001-11-14

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US (1) US5981304A (en)
EP (1) EP0851451B1 (en)
JP (1) JPH10221861A (en)
DE (1) DE69708257T2 (en)
FR (1) FR2757999B1 (en)

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Publication number Priority date Publication date Assignee Title
FR2769751B1 (en) * 1997-10-14 1999-11-12 Commissariat Energie Atomique ELECTRON SOURCE WITH MICROPOINTS, WITH FOCUSING GRID AND HIGH DENSITY OF MICROPOINTS, AND FLAT SCREEN USING SUCH A SOURCE
US6032923A (en) * 1998-01-08 2000-03-07 Xerox Corporation Fluid valves having cantilevered blocking films
FR2779271B1 (en) * 1998-05-26 2000-07-07 Commissariat Energie Atomique METHOD FOR MANUFACTURING A MICROPOINT ELECTRON SOURCE WITH A SELF-ALIGNED FOCUSING GRID
FR2779243B1 (en) * 1998-05-26 2000-07-07 Commissariat Energie Atomique PROCESS FOR PRODUCING SELF-ALIGNED OPENINGS ON A STRUCTURE BY PHOTOLITHOGRAPHY, PARTICULARLY FOR MICROPOINT FLAT SCREEN

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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
US5249340A (en) * 1991-06-24 1993-10-05 Motorola, Inc. Field emission device employing a selective electrode deposition method
JPH05242794A (en) * 1991-11-29 1993-09-21 Motorola Inc Field emission device with integrated electrostatic field lens
US5186670A (en) * 1992-03-02 1993-02-16 Micron Technology, Inc. Method to form self-aligned gate structures and focus rings
FR2723799B1 (en) * 1994-08-16 1996-09-20 Commissariat Energie Atomique METHOD FOR MANUFACTURING A MICROPOINT ELECTRON SOURCE

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JPH10221861A (en) 1998-08-21
FR2757999A1 (en) 1998-07-03
EP0851451A1 (en) 1998-07-01
US5981304A (en) 1999-11-09
FR2757999B1 (en) 1999-01-29
DE69708257T2 (en) 2002-07-25
DE69708257D1 (en) 2001-12-20

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