EP0634769B1 - Manufacturing method for micropoint electron sources - Google Patents

Manufacturing method for micropoint electron sources Download PDF

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Publication number
EP0634769B1
EP0634769B1 EP94401582A EP94401582A EP0634769B1 EP 0634769 B1 EP0634769 B1 EP 0634769B1 EP 94401582 A EP94401582 A EP 94401582A EP 94401582 A EP94401582 A EP 94401582A EP 0634769 B1 EP0634769 B1 EP 0634769B1
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Prior art keywords
holes
grid
mask
defects
source
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German (de)
French (fr)
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EP0634769A1 (en
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Pierre Vaudaine
Brigitte Montmayeul
Michel Borel
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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
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/022—Manufacture of electrodes or electrode systems of cold cathodes
    • H01J9/025—Manufacture of electrodes or electrode systems of cold cathodes of field emission cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2201/00—Electrodes common to discharge tubes
    • H01J2201/30—Cold cathodes
    • H01J2201/319—Circuit elements associated with the emitters by direct integration

Definitions

  • the present invention relates to an improvement to a method for manufacturing a microtip electron source. It makes it possible to improve the uniformity and / or the reproducibility of the emission of cathodes with microtips and to relax the manufacturing constraints.
  • Microtip emissive cathodes are sources of electrons used in particular in the field of visualization and in particular for flat screens. They can also be used in electron guns or in vacuum gauges.
  • Document FR-A-2 593 953 describes a method of manufacturing a display device by cathodoluminescence excited by field emission.
  • the electron source is a microtip cathode deposited on a glass substrate and having a matrix structure.
  • FIG. 1 schematically represents a known source of electrons with microtip emissive cathodes described in detail in the aforementioned document FR-A-2 623 013.
  • This source has a matrix structure and optionally comprises on a substrate 2, for example made of glass, a thin layer of silica 4.
  • a plurality of electrodes 5 in the form of parallel conductive strips playing the role of cathodic conductors and constituting the columns of the matrix structure.
  • the cathode conductors are each covered by a resistive layer 7 which can be continuous (except on the ends to allow the connection of the cathode conductors with polarization means 20).
  • Above the insulating layer 8 are formed a plurality of electrodes 10 also in the form of parallel conductive strips. These electrodes 10 are perpendicular to the electrodes 5 and play the role of grids which constitute the lines of the matrix structure.
  • a resistive layer can optionally be placed above or below the electrodes 10.
  • Document EP-A-0 461 990 recommends using electrodes (for example cathode conductors) in the form of a lattice so that the microtips are arranged in the openings of the lattice of these electrodes.
  • the breakdown resistance no longer depends, in the first order, on the thickness of the resistive layer but on the distance between the cathode conductor and the microtip.
  • Figure 2 is a schematic top view of the electron source and Figure 3 is an enlarged and sectional view along the axis III-III of Figure 2.
  • This matrix structure comprises a substrate 1, for example made of glass, and possibly a thin layer 6 of silica. On the silica layer 6 is formed a series of parallel electrodes 3, each having a lattice structure, playing the role of cathode conductors. These are the columns of the matrix structure.
  • the cathode conductors 3 are covered by the resistive layer 9 made of silicon and by the insulating layer 11 made of silica. Above the insulating layer 11 is formed another series of parallel electrodes also having an openwork but different structure, designed to minimize the areas of overlap with the cathode conductors. These electrodes are perpendicular to the cathode conductors and constitute the grids. These are the lines of the matrix structure.
  • Figures 2 and 3 show a detail of one of the grids of the device.
  • the grid bearing the general reference 13, comprises parallel tracks 14 orthogonally cutting other parallel tracks 15.
  • the grid has enlarged zones 17, here of square shape. It can be seen in FIG. 2 that the areas 16 of overlap of the cathode conductor 3 and tracks 14 and 15 of the grid have a very small surface.
  • the enlarged zones 17 are located in the center of the meshes forming the cathode conductor.
  • microwares 18 are formed in the thickness of the grid and of the insulating layer 11.
  • the microtips 19 are deposited in these holes and rest on the resistive layer 9.
  • a micro-hole and micro-tip assembly constitutes a micro-emitter of electrons.
  • the micro-emitters occupy the central regions of the mesh of the conductor lattice cathodic and the enlarged and square areas 17 of the grid. In the case shown in Figures 2 and 3, each of the meshes of the cathode conductor or each enlarged grid area comprises 16 micro-emitters.
  • the dimensions of the micro-transmitters are optimized to obtain the best emission. These are the diameter of the holes, the geometry of the points, the thickness of the insulating layer and the thickness of the grid. Indeed, the emission current strongly depends on these dimensions. It is inversely proportional to the diameter of the holes. It is optimum when the holes are circular and decreases when the holes lose this circular shape, for example when they become oval. The emission current is still optimum when the tips of the tips are located in the thickness of the gate conductor. It decreases very quickly when the points are high and they protrude above the grid or when they are low and their top remains below the grid. The position of the apex of the points is related to the thickness of the insulating layer in which the holes are etched and to the geometry of the points, in particular the angle of the cone which they form.
  • the emitted current is constant. If, in the emissive surface of a cathode or if from one cathode to another, the diameter of the holes varies in an uncontrolled way, or even if the points come out of the thickness of the grids, the emitted current will vary and the uniformity of emission or its reproducibility is no longer guaranteed. This amounts to saying that the emission is affected if the manufacturing parameters exceed the admissible tolerance range for obtaining the dimensions required for the micro-emitters.
  • the equipment used for the manufacture of the emissive cathode is not perfect and their performance is only optimum and reproducible within a certain tolerance. If this tolerance is wider than that of the emissive structure, the characteristics of the emission are affected. On the other hand, certain defects originate from or are amplified by the substrate, in particular by its lack of flatness.
  • the invention overcomes these drawbacks by intervening on a mask used during the manufacture of microtip cathodes to voluntarily create regularly distributed defects, at a sufficiently fine periodicity to make them invisible and in a range of sufficiently large dimensions or shapes. large or in sufficient number to drown all the defects (voluntary and involuntary).
  • the mask is corrected to provide it, over its entire surface, with holes of diameters varying according to a distribution making it possible to encompass these manufacturing defects.
  • the mask is corrected to provide it, over its entire surface, with round holes and oval holes whose major axes lie in the direction of the small axes of the oval holes of defective grid, the round holes and the oval correction holes being regularly mixed on the mask.
  • the number of holes in the mask is increased so that the grid of future sources is provided with a number of holes equivalent to a good positioning of the holes by compared to the grid.
  • the method of manufacturing the holes can advantageously be a photolithographic method.
  • the emissive structure illustrated in FIGS. 2 and 3 can advantageously be produced by a known method and briefly summarized below.
  • a metal layer is deposited, for example by sputtering.
  • This metallic layer can be a niobium layer 2000 angstroms thick.
  • the cathode conductors 3 are produced from the previously deposited metal layer by giving them a lattice shape. This can be done by photolithography and reactive ion etching.
  • the resistive layer 9 made of doped silicon is then deposited, for example by sputtering.
  • the thickness of this layer can be 5000 angstroms.
  • an insulating layer 11 for example made of silica, is deposited by a chemical vapor deposition (CVD) technique or by sputtering.
  • CVD chemical vapor deposition
  • the vapor deposition technique is preferably used, which makes it possible to obtain an oxide layer of uniform quality and of constant thickness.
  • niobium approximately 400 nm thick is deposited, for example by vacuum evaporation, from which the gate conductors are formed by photolithography and reactive ion etching.
  • the holes for the microtip housing are formed by a photolithography method. For this, a layer of photosensitive resin is spread over the grid conductors or the areas of the insulating layer 11 exposed, then dried in an oven. The resin layer is exposed to ultraviolet rays through an opaque mask provided with holes corresponding to the holes to be obtained on the grid conductors and the insulating layer. For this, the mask was positioned relative to the substrate to obtain the grid holes at the desired locations.
  • the same hole mask is used for all substrates. In the case of a sunstroke nearby, this mask is at scale 1 and covers the entire emissive surface. In the case of exposure by photo-repeater, it can be at scale 5 and cover only a fraction of the emissive surface. The elementary insolation step is then repeated as many times as necessary to cover the entire emissive surface.
  • the substrate After exposure, the substrate is soaked in a developer bath in order to open the holes in the resin.
  • a dry etching process makes it possible to etch the holes in the grid conductors and then in the insulating layer 11, the resin layer serving as a mask.
  • the resin layer is removed, for example by a wet chemical process.
  • microtips occurs in three stages.
  • a layer of nickel is first deposited by evaporation under vacuum and at high incidence relative to the perpendicular to the substrate so that the nickel is deposited only on the upper face of the structure and on the flanks of the holes of the grid previously etched. in the structure but not at the bottom of the holes made in the insulation.
  • the material which is to form the points 19 is deposited in a direction perpendicular to the substrate so as to deposit this material on the nickel layer previously deposited and also at the bottom of the holes.
  • this new layer for example molybdenum
  • the holes gradually become blocked and a cone (microtip) is formed in each hole. The deposit is stopped when the holes are plugged.
  • the nickel layer is then dissolved by an electrochemical process, which makes it possible to evacuate the molybdenum layer which it supports on the upper face of the structure, while keeping the tips in the holes.
  • the points are therefore automatically centered in the holes.
  • Their height depends on the angle of the cone which is linked to the deposition parameters and also to the diameter of the holes. At a constant cone angle, the wider the holes, the higher the points and vice versa.
  • An inhomogeneous emission from a microtip cathode can be linked to a variation too significant diameter of the holes on the structure constituting the cathode. If, for example, the exposure was carried out with a photo-repeater which remakes its focusing at each stage, this focusing can be disturbed locally by defects in the flatness of the substrate. As a result, for example, certain areas of the structure fall outside the depth of field and, as a result, the holes come out too small. To remedy this defect, holes of different diameters are mixed on the emissive surface so as to always have a certain number of micro-emitters which emit at their optimum level. The overall emission level is reduced but it is homogeneous.
  • FIG. 4 shows part of a mask 30 intended for the creation of micro-holes in a microtip cathode structure used for a fluorescent screen.
  • This part of the mask comprises three adjacent sets of holes 31, 32 and 33, corresponding to three adjacent meshes defined by the cathode conductors on the cathode. These three meshes constitute an elementary group. Several of these elementary groups are needed to help form a pixel on the screen.
  • Each mesh comprises for example sixteen micro-emitters which emit at their optimum level when the diameter of the micro-holes is 1.3 ⁇ m as announced above.
  • the assembly 31 is formed of holes of 1.1 ⁇ m in diameter, that is to say theoretically producing holes of 1.1 ⁇ m on the emissive structure.
  • the assembly 32 is formed of 1.3 ⁇ m holes in diameter, that is to say theoretically producing 1.3 ⁇ m holes on the emissive structure.
  • the assembly 33 is formed of holes of 1.5 ⁇ m in diameter, that is to say theoretically producing holes of 1.5 ⁇ m on the emissive structure.
  • the emissive structure therefore comprises an equally distributed distribution of assemblies such as 31, 32 and 33.
  • the micro-emitters corresponding to the assemblies 32 which will emit in an optimum manner.
  • the other micro-transmitters, corresponding to sets 31 and 33 will have a very reduced emission. If in other areas of the emissive structure the transfer of the holes of the mask was badly carried out and that results in an increase in diameter of the micro-holes of the electron source of 0.2 ⁇ m, these are the micro transmitters corresponding to the assemblies 31 which will emit in an optimum manner.
  • the other micro-transmitters, corresponding to sets 32 and 33 will have a very reduced emission.
  • the same reasoning can be used for sets 33 in the event of a 0.2 ⁇ m diameter reduction. As a result, there is always the same number of micro-emitters emitting optimally distributed uniformly over the entire source which thus emits homogeneously.
  • An inhomogeneous emission from a microtip cathode can also be linked to an alteration in the shape of the holes transferred to the emissive structure.
  • An aberration of the optics of the exposure equipment can lead to obtaining oval holes inclined for example at 45 ° to the left. So from a mask having uniformly round holes one can obtain on the emissive structure zones with round holes corresponding to an optic without aberration and zones with holes all oval and also inclined and corresponding to an optic with aberration.
  • the correction to be made on the mask then consists of regularly mixing, over the entire surface of the mask, round holes with oval holes inclined at 45 ° to the right.
  • FIG. 5 shows part of such a corrective mask and representing a set of sixteen holes corresponding to a mesh of the emissive structure. It is noted that this assembly comprises eight round holes 41 and eight oval holes 42 inclined to the right, the round and oval holes being regularly distributed. On the mask, all the sets of holes are identical to those shown in Figure 5.
  • FIG. 6 in this case represents the shapes of holes reproduced on a mesh 45 of the emissive structure by the holes of the mask 40 of FIG. 5.
  • the circular holes 41 of the mask correspond to the emissive structure of the oval holes 46 inclined to the left .
  • the oval holes 42 inclined to the right correspond to the emissive structure of the circular holes 47.
  • the balance of the holes on the whole of the emissive structure reveals as many inclined oval holes as round holes, the oval holes inclined to the left and on the right giving the same emission level for micro-transmitters. It will be understood that the emission level from the cathode is homogeneous over the entire emissive surface.
  • An inhomogeneous emission from a microtip cathode can also be linked to an incorrect positioning of the grids relative to the microtips.
  • the misalignment is large enough (greater than 2 ⁇ m) so that holes are outside the enlarged areas reserved for them in the grid.
  • Figure 7 gives an example of such a misalignment.
  • the enlarged and square area 17 is not centered in the mesh 21 defined by the cathode conductor 3. Of the sixteen micro-transmitters shown, seven are outside the area 17 and do not emit.
  • the area covered by the holes 18 is enlarged in the mesh beyond the square area 17 so that if this area 17 is off-center in the mesh, it still covers the same number of microtips.
  • simply increase the number of holes in the mask so as to transfer the desired number of holes.
  • a mesh By way of example, to always have sixteen micro-transmitters in operation, it is possible, for a mesh, to provide 36 holes arranged in a square on the corresponding part of the mask.
  • Figure 8 shows the result obtained for a square area 17 centered in the mesh 21.
  • Figure 9 shows the result obtained for a square area 17 offset from the mesh 21. In both cases, there are always sixteen micro- transmitters in operation.

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  • Cold Cathode And The Manufacture (AREA)

Description

La présente invention concerne un perfectionnement à un procédé de fabrication d'une source d'électrons à micropointes. Elle permet d'améliorer l'uniformité et/ou la reproductibilité de l'émission des cathodes à micropointes et de relâcher les contraintes de fabrication.The present invention relates to an improvement to a method for manufacturing a microtip electron source. It makes it possible to improve the uniformity and / or the reproducibility of the emission of cathodes with microtips and to relax the manufacturing constraints.

Les cathodes émissives à micropointes sont des sources d'électrons utilisées notamment dans le domaine de la visualisation et en particulier pour les écrans plats. Elles peuvent aussi être utilisées dans des canons à électrons ou encore dans des jauges à vide.Microtip emissive cathodes are sources of electrons used in particular in the field of visualization and in particular for flat screens. They can also be used in electron guns or in vacuum gauges.

Le document FR-A-2 593 953 décrit un procédé de fabrication d'un dispositif de visualisation par cathodoluminescence excitée par émission de champ. La source d'électrons est une cathode à micropointes déposée sur un substrat en verre et possédant une structure matricielle.Document FR-A-2 593 953 describes a method of manufacturing a display device by cathodoluminescence excited by field emission. The electron source is a microtip cathode deposited on a glass substrate and having a matrix structure.

Les documents FR-A-2 623 013 et FR-A-2 663 462 décrivent des perfectionnements apportés à cette cathode à micropointes. Ils concernent en particulier l'amélioration de l'uniformité d'émission en limitant le courant dans les pointes qui émettent le plus. Ce résultat est obtenu en introduisant une résistance en série avec les micropointes. Cette résistance est constituée à partir d'une couche résistive continue ou non. La figure 1 représente schématiquement une source connue d'électrons à cathodes émissives à micropointes décrite en détails dans le document FR-A-2 623 013 précité. Cette source a une structure matricielle et comprend éventuellement sur un substrat 2, par exemple en verre, une mince couche de silice 4. Sur cette couche de silice 4 sont formées une pluralité d'électrodes 5 en forme de bandes conductrices parallèles jouant le rôle de conducteurs cathodiques et constituant les colonnes de la structure matricielle. Les conducteurs cathodiques sont recouverts chacun par une couche résistive 7 qui peut être continue (excepté sur les extrémités pour permettre la connexion des conducteurs cathodiques avec des moyens de polarisation 20). Une couche électriquement isolante 8, en silice, recouvre les couches résistives 7. Au-dessus de la couche isolante 8 sont formées une pluralité d'électrodes 10 également en forme de bandes conductrices parallèles. Ces électrodes 10 sont perpendiculaires aux électrodes 5 et jouent le rôle de grilles qui constituent les lignes de la structure matricielle. Une couche résistive peut éventuellement être disposée au-dessus ou au-dessous des électrodes 10.The documents FR-A-2 623 013 and FR-A-2 663 462 describe improvements made to this cathode with microtips. They concern in particular the improvement of the uniformity of emission by limiting the current in the peaks which emit the most. This is achieved by introducing resistance in series with the microtips. This resistance is formed from a continuous or non-continuous resistive layer. FIG. 1 schematically represents a known source of electrons with microtip emissive cathodes described in detail in the aforementioned document FR-A-2 623 013. This source has a matrix structure and optionally comprises on a substrate 2, for example made of glass, a thin layer of silica 4. On this layer of silica 4 are formed a plurality of electrodes 5 in the form of parallel conductive strips playing the role of cathodic conductors and constituting the columns of the matrix structure. The cathode conductors are each covered by a resistive layer 7 which can be continuous (except on the ends to allow the connection of the cathode conductors with polarization means 20). An electrically insulating layer 8, made of silica, covers the resistive layers 7. Above the insulating layer 8 are formed a plurality of electrodes 10 also in the form of parallel conductive strips. These electrodes 10 are perpendicular to the electrodes 5 and play the role of grids which constitute the lines of the matrix structure. A resistive layer can optionally be placed above or below the electrodes 10.

Le document EP-A-0 461 990 préconise d'utiliser des électrodes (par exemple les conducteurs cathodiques) en forme de treillis de manière que les micropointes soient disposées dans les ouvertures du treillis de ces électrodes. Dans cette configuration, la résistance au claquage ne dépend plus, au premier ordre, de l'épaisseur de la couche résistive mais de la distance entre le conducteur cathodique et la micropointe.Document EP-A-0 461 990 recommends using electrodes (for example cathode conductors) in the form of a lattice so that the microtips are arranged in the openings of the lattice of these electrodes. In this configuration, the breakdown resistance no longer depends, in the first order, on the thickness of the resistive layer but on the distance between the cathode conductor and the microtip.

Un autre perfectionnement à ces cathodes à micropointes a été apporté par le document EP-A-0 558 393 au nom du présent demandeur. Ce perfectionnement consiste à réduire les risques de courts-circuits entre les lignes et les colonnes par l'intermédiaire des micropointes. Pour ce faire, on réduit au maximum les zones de recouvrement des deux séries d'électrodes. Ceci est illustré par les figures 2 et 3 jointes en annexe.Another improvement to these microtip cathodes has been brought by document EP-A-0 558 393 in the name of the present applicant. This improvement consists in reducing the risks of short circuits between the rows and the columns by means of microtips. To do this, the overlap areas of the two sets of electrodes are reduced as much as possible. This is illustrated by Figures 2 and 3 attached in the appendix.

La figure 2 est une vue de dessus schématique de la source d'électrons et la figure 3 est une vue agrandie et en coupe selon l'axe III-III de la figure 2. Cette structure matricielle comprend un substrat 1, par exemple en verre, et éventuellement une mince couche 6 de silice. Sur la couche de silice 6 est formée une série d'électrodes parallèles 3, chacune ayant une structure en treillis, jouant le rôle de conducteurs cathodiques. Ce sont les colonnes de la structure matricielle.Figure 2 is a schematic top view of the electron source and Figure 3 is an enlarged and sectional view along the axis III-III of Figure 2. This matrix structure comprises a substrate 1, for example made of glass, and possibly a thin layer 6 of silica. On the silica layer 6 is formed a series of parallel electrodes 3, each having a lattice structure, playing the role of cathode conductors. These are the columns of the matrix structure.

Les conducteurs cathodiques 3 sont recouverts par la couche résistive 9 en silicium et par la couche isolante 11 en silice. Au-dessus de la couche isolante 11 est formée une autre série d'électrodes parallèles ayant également une structure ajourée mais différente, dessinée pour minimiser les zones de recouvrement avec les conducteurs cathodiques. Ces électrodes sont perpendiculaires aux conducteurs cathodiques et constituent les grilles. Ce sont les lignes de la structure matricielle.The cathode conductors 3 are covered by the resistive layer 9 made of silicon and by the insulating layer 11 made of silica. Above the insulating layer 11 is formed another series of parallel electrodes also having an openwork but different structure, designed to minimize the areas of overlap with the cathode conductors. These electrodes are perpendicular to the cathode conductors and constitute the grids. These are the lines of the matrix structure.

Les figures 2 et 3 montrent un détail de l'une des grilles du dispositif. La grille, portant la référence générale 13, comporte des pistes parallèles 14 coupant orthogonalement d'autres pistes parallèles 15. Aux intersections des pistes 14 et 15 entre elles, la grille présente des zones élargies 17, ici de forme carrée. On voit sur la figure 2 que les zones 16 de recouvrement du conducteur cathodique 3 et des pistes 14 et 15 de la grille ont une surface très faible. Les zones élargies 17 sont situées au centre des mailles formant le conducteur cathodique.Figures 2 and 3 show a detail of one of the grids of the device. The grid, bearing the general reference 13, comprises parallel tracks 14 orthogonally cutting other parallel tracks 15. At the intersections of the tracks 14 and 15 therebetween, the grid has enlarged zones 17, here of square shape. It can be seen in FIG. 2 that the areas 16 of overlap of the cathode conductor 3 and tracks 14 and 15 of the grid have a very small surface. The enlarged zones 17 are located in the center of the meshes forming the cathode conductor.

Dans les zones de croisement des conducteurs cathodiques et des grilles, des microtrous 18 sont formés dans l'épaisseur de la grille et de la couche isolante 11. Les micro-pointes 19 sont déposées dans ces trous et reposent sur la couche résistive 9. Un ensemble micro-trou et micro-pointe constitue un micro-émetteur d'électrons. Les micro-émetteurs occupent les régions centrales des mailles du treillis du conducteur cathodique et les zones élargies et carrées 17 de la grille. Dans le cas représenté sur les figures 2 et 3, chacune des mailles du conducteur cathodique ou chaque zone élargie de grille comporte 16 micro-émetteurs.In the crossing zones of the cathode conductors and of the grids, microwares 18 are formed in the thickness of the grid and of the insulating layer 11. The microtips 19 are deposited in these holes and rest on the resistive layer 9. A micro-hole and micro-tip assembly constitutes a micro-emitter of electrons. The micro-emitters occupy the central regions of the mesh of the conductor lattice cathodic and the enlarged and square areas 17 of the grid. In the case shown in Figures 2 and 3, each of the meshes of the cathode conductor or each enlarged grid area comprises 16 micro-emitters.

Les dimensions des micro-émetteurs sont optimisées pour obtenir la meilleure émission. Il s'agit du diamètre des trous, de la géométrie des pointes, de l'épaisseur de la couche isolante et de l'épaisseur de la grille. En effet, le courant d'émission dépend fortement de ces dimensions. Il est inversement proportionnel au diamètre des trous. Il est optimum lorsque les trous sont circulaires et diminue lorsque les trous perdent cette forme circulaire, par exemple lorsqu'ils deviennent ovales. Le courant d'émission est encore optimum lorsque le sommet des pointes est situé dans l'épaisseur du conducteur de grille. Il diminue très vite lorsque les pointes sont hautes et qu'elles dépassent au-dessus de la grille ou lorsqu'elles sont basses et que leur sommet reste en dessous de la grille. La position du sommet des pointes est liée à l'épaisseur de la couche isolante dans laquelle sont gravés les trous et à la géométrie des pointes, notamment à l'angle du cône qu'elles forment.The dimensions of the micro-transmitters are optimized to obtain the best emission. These are the diameter of the holes, the geometry of the points, the thickness of the insulating layer and the thickness of the grid. Indeed, the emission current strongly depends on these dimensions. It is inversely proportional to the diameter of the holes. It is optimum when the holes are circular and decreases when the holes lose this circular shape, for example when they become oval. The emission current is still optimum when the tips of the tips are located in the thickness of the gate conductor. It decreases very quickly when the points are high and they protrude above the grid or when they are low and their top remains below the grid. The position of the apex of the points is related to the thickness of the insulating layer in which the holes are etched and to the geometry of the points, in particular the angle of the cone which they form.

A titre d'exemple, lorsque les conditions suivantes sont réalisées :

  • épaisseur de la couche isolante 11 = 1 µm,
  • diamètre des trous 18 = 1,3 µm,
  • pointes 19 en molybdène déposées par évaporation perpendiculairement à la surface,
  • épaisseur de grille dans la zone élargie = 0,4 µm, alors le sommet des pointes est situé dans l'épaisseur de la grille.
For example, when the following conditions are met:
  • thickness of the insulating layer 11 = 1 μm,
  • hole diameter 18 = 1.3 µm,
  • molybdenum tips 19 deposited by evaporation perpendicular to the surface,
  • grid thickness in the enlarged area = 0.4 µm, then the tips of the tips are located in the thickness of the grid.

Malgré l'amélioration de l'uniformité d'émission apportée par les perfectionnements successifs divulgués dans les documents cités ci-dessus, on a constaté des inhomogénéités liées à des défauts dans la structure des cathodes à micropointes. Ces défauts peuvent provenir de l'imperfection des procédés de fabrication des micro-émetteurs. Ils peuvent provenir également d'un manque de planéité du substrat sur lequel est élaborée la cathode.Despite the improvement in emission uniformity brought about by the successive improvements disclosed in the documents cited above, we have noted inhomogeneities linked to defects in the structure of microtip cathodes. These defects can come from the imperfection of the manufacturing processes of micro-transmitters. They can also come from a lack of flatness of the substrate on which the cathode is made.

Parmi les défauts décelés, on peut citer :

  • le manque d'uniformité du diamètre ou de la forme des micro-trous, ou la mauvaise reproductibilité de ces paramètres (diamètre, forme) d'un écran à l'autre,
  • le mauvais alignement entre les pointes émissives et les grilles qui font que certaines pointes n'émettent pas.
Among the defects detected, we can cite:
  • the lack of uniformity in the diameter or shape of the micro-holes, or the poor reproducibility of these parameters (diameter, shape) from one screen to another,
  • the bad alignment between the emissive points and the grids which make that certain points do not emit.

Ceci est dû au mauvais contrôle des paramètres de fabrication et/ou aux imperfections des équipements utilisés. Tant que le sommet des pointes reste dans l'épaisseur de la grille et que le diamètre des trous est constant, le courant émis est constant. Si, dans la surface émissive d'une cathode ou si d'une cathode à une autre, le diamètre des trous varie de façon incontrôlée, ou encore si les pointes sortent de l'épaisseur des grilles, le courant émis va varier et l'uniformité d'émission ou sa reproductibilité n'est plus assurée. Cela revient à dire que l'émission se trouve affectée si les paramètres de fabrication sortent de la plage de tolérances admissibles pour l'obtention des dimensions requises pour les micro-émetteurs.This is due to poor control of the manufacturing parameters and / or imperfections in the equipment used. As long as the tips of the tips remain within the thickness of the grid and the diameter of the holes is constant, the emitted current is constant. If, in the emissive surface of a cathode or if from one cathode to another, the diameter of the holes varies in an uncontrolled way, or even if the points come out of the thickness of the grids, the emitted current will vary and the uniformity of emission or its reproducibility is no longer guaranteed. This amounts to saying that the emission is affected if the manufacturing parameters exceed the admissible tolerance range for obtaining the dimensions required for the micro-emitters.

Or, les équipements utilisés pour la fabrication de la cathode émissive ne sont pas parfaits et leurs performances ne sont optimum et reproductibles que dans une certaine tolérance. Si cette tolérance est plus large que celle de la structure émissive, les caractéristiques de l'émission sont affectées. D'autre part, certains défauts ont pour origine ou sont amplifiés par le substrat, notamment par son manque de planéité.However, the equipment used for the manufacture of the emissive cathode is not perfect and their performance is only optimum and reproducible within a certain tolerance. If this tolerance is wider than that of the emissive structure, the characteristics of the emission are affected. On the other hand, certain defects originate from or are amplified by the substrate, in particular by its lack of flatness.

L'invention permet de remédier à ces inconvénients en intervenant sur un masque utilisé lors de la fabrication des cathodes à micropointes pour créer volontairement des défauts régulièrement répartis, selon une périodicité suffisamment fine pour les rendre invisibles et dans une fourchette de dimensions ou de formes suffisamment grande ou en nombre suffisant pour noyer tous les défauts (volontaires et involontaires).The invention overcomes these drawbacks by intervening on a mask used during the manufacture of microtip cathodes to voluntarily create regularly distributed defects, at a sufficiently fine periodicity to make them invisible and in a range of sufficiently large dimensions or shapes. large or in sufficient number to drown all the defects (voluntary and involuntary).

L'invention a donc pour objet un procédé de fabrication d'une source d'électrons à micropointes, les micropointes étant reliées électriquement à au moins un conducteur cathodique et étant situées dans des trous pratiqués dans au moins une grille d'extraction des électrons, le procédé utilisant une étape de masquage pour réaliser les trous de la grille au moyen d'un masque présentant des trous correspondants, les trous du masque ayant des dimensions et des formes déterminées pour théoriquement conduire à l'obtention de trous dans la grille de dimensions, de formes et de positions comprises dans des tolérances données, les sommets des micropointes devant se trouver dans l'épaisseur de la grille, caractérisé en ce que, après avoir réalisé une source d'électrons selon ledit procédé :

  • on évalue si la source a une émission suffisamment homogène et/ou reproductible à une autre source,
  • si l'émission de la source est jugée inhomogène et/ou non reproductible, on détermine les défauts qui sont la cause de cette émission inhomogène et/ou non reproductible et qui sont dus à des formes, à des dimensions ou à des positions de trous tombant en dehors des tolérances ou au fait que les sommets de micropointes ne se trouvent pas dans l'épaisseur de la grille,
  • on corrige alors le masque utilisé pour rendre homogène et/ou reproductible les futures sources élaborées par ce procédé, la correction consistant à modifier les formes et/ou les dimensions d'au moins certains trous du masque et/ou le nombre de trous du masque pour compenser des défauts déterminés précédemment en créant ainsi volontairement des défauts et/ou des trous supplémentaires régulièrement répartis sur la surface émissive de telle sorte que l'on a toujours le même nombre de micropointes émettant de façon optimum répartis uniformément sur l'ensemble de la source. On entend par reproductibilité de l'émission le niveau et/ou l'uniformité de l'émission.
The subject of the invention is therefore a method of manufacturing a source of electrons with microtips, the microtips being electrically connected to at least one cathode conductor and being located in holes made in at least one electron extraction grid, the method using a masking step to make the holes in the grid by means of a mask having corresponding holes, the holes in the mask having dimensions and shapes determined to theoretically lead to obtaining holes in the grid of dimensions , of shapes and positions included in given tolerances, the vertices of the microtips having to be in the thickness of the grid, characterized in that, after having produced an electron source according to said process:
  • we assess whether the source has a sufficiently homogeneous and / or reproducible emission to another source,
  • if the emission of the source is judged inhomogeneous and / or not reproducible, one determines the defects which are the cause of this inhomogeneous and / or not reproducible and which are due to forms, dimensions or positions of holes falling outside the tolerances or the fact that the vertices of microtips are not within the thickness of the grid,
  • the mask used to make the future sources developed by this process is homogeneous and / or reproducible, the correction consisting in modifying the shapes and / or the dimensions of at least certain holes in the mask and / or the number of holes in the mask to compensate for faults determined previously by thus voluntarily creating faults and / or additional holes regularly distributed over the emissive surface so that there is always the same number of microtips emitting optimally distributed uniformly over the whole of the source. By reproducibility of the emission is meant the level and / or uniformity of the emission.

Si les défauts sont dus à une variation en dehors des tolérances du diamètre des trous de la grille, on corrige le masque pour le pourvoir, sur toute sa surface, de trous de diamètres variant selon une distribution permettant d'englober ces défauts de fabrication.If the defects are due to a variation outside the tolerances of the diameter of the holes of the grid, the mask is corrected to provide it, over its entire surface, with holes of diameters varying according to a distribution making it possible to encompass these manufacturing defects.

Si les défauts sont dus à la présence de trous de grille ovales, on corrige le masque pour le pourvoir, sur toute sa surface, de trous ronds et de trous ovales dont les grands axes se trouvent dans la direction des petits axes des trous ovales de grille défectueux, les trous ronds et les trous ovales de correction étant régulièrement mélangés sur le masque.If the defects are due to the presence of oval grid holes, the mask is corrected to provide it, over its entire surface, with round holes and oval holes whose major axes lie in the direction of the small axes of the oval holes of defective grid, the round holes and the oval correction holes being regularly mixed on the mask.

Si les défauts sont dus à un mauvais positionnement des trous par rapport à la grille, on augmente le nombre de trous dans le masque de façon que la grille des futures sources soit pourvue d'un nombre de trous équivalent à un bon positionnement des trous par rapport à la grille.If the defects are due to a bad positioning of the holes relative to the grid, the number of holes in the mask is increased so that the grid of future sources is provided with a number of holes equivalent to a good positioning of the holes by compared to the grid.

Le procédé de fabrication des trous peut avantageusement être un procédé photolithographique.The method of manufacturing the holes can advantageously be a photolithographic method.

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

  • la figure 1 représente de manière schématique une source d'électrons à cathodes émissives à micropointes selon l'art connu ;
  • les figures 2 et 3 illustrent une source d'électrons à micropointes pour laquelle les conducteurs cathodiques et les grilles ont une structure en treillis ;
  • les figures 4 et 5 représentent des parties de masques utilisés lors de la mise en oeuvre du procédé perfectionné selon l'invention ;
  • la figure 6 montre des formes de trous reproduits sur une maille de la structure émissive après la mise en oeuvre du procédé perfectionné selon l'invention ;
  • la figure 7 illustre un défaut structurel sur une source d'électrons à micropointes selon l'art antérieur ;
  • les figures 8 et 9 illustrent des résultats obtenus sur une source d'électrons à micropointes après la mise en oeuvre du procédé perfectionné selon l'invention.
The invention will be better understood and other advantages and features will appear on reading the description which follows, given by way of nonlimiting example, accompanied by the appended drawings among which:
  • FIG. 1 schematically represents a source of electrons with microtip emissive cathodes according to the prior art;
  • FIGS. 2 and 3 illustrate a source of microtip electrons for which the cathode conductors and the grids have a lattice structure;
  • Figures 4 and 5 show parts of masks used during the implementation of the improved method according to the invention;
  • FIG. 6 shows the shapes of holes reproduced on a mesh of the emissive structure after the implementation of the improved method according to the invention;
  • FIG. 7 illustrates a structural defect on a source of microtip electrons according to the prior art;
  • Figures 8 and 9 illustrate results obtained on a microtip electron source after the implementation of the improved method according to the invention.

La structure émissive illustrée par les figures 2 et 3 peut avantageusement être réalisée par un procédé connu et brièvement résumé ci-dessous.The emissive structure illustrated in FIGS. 2 and 3 can advantageously be produced by a known method and briefly summarized below.

Sur le substrat isolant 1, par exemple en verre, recouvert d'une fine couche 6 de silice d'environ 1000 angströms, on dépose une couche métallique par exemple par pulvérisation cathodique. Cette couche métallique peut être une couche de niobium de 2000 angströms d'épaisseur.On the insulating substrate 1, for example made of glass, covered with a thin layer 6 of silica of approximately 1000 angstroms, a metal layer is deposited, for example by sputtering. This metallic layer can be a niobium layer 2000 angstroms thick.

On réalise à partir de la couche métallique précédemment déposée les conducteurs cathodiques 3 en leur donnant une forme en treillis. Ceci peut être réalisé par photolithographie et gravure ionique réactive.The cathode conductors 3 are produced from the previously deposited metal layer by giving them a lattice shape. This can be done by photolithography and reactive ion etching.

On dépose ensuite, par exemple par pulvérisation cathodique, la couche résistive 9 en silicium dopé. L'épaisseur de cette couche peut être de 5000 angströms.The resistive layer 9 made of doped silicon is then deposited, for example by sputtering. The thickness of this layer can be 5000 angstroms.

Sur la couche résistive 9 on dépose une couche isolante 11, par exemple en silice, par une technique de dépôt chimique en phase vapeur (CVD) ou par pulvérisation cathodique. On utilise de préférence la technique de dépôt en phase vapeur qui permet d'obtenir une couche d'oxyde de qualité homogène et d'épaisseur constante.On the resistive layer 9 an insulating layer 11, for example made of silica, is deposited by a chemical vapor deposition (CVD) technique or by sputtering. The vapor deposition technique is preferably used, which makes it possible to obtain an oxide layer of uniform quality and of constant thickness.

Sur la couche isolante 11, on dépose par exemple par évaporation sous vide une couche de niobium d'environ 400 nm d'épaisseur à partir de laquelle on forme les conducteurs de grille par photolithographie et gravure ionique réactive.On the insulating layer 11, a layer of niobium approximately 400 nm thick is deposited, for example by vacuum evaporation, from which the gate conductors are formed by photolithography and reactive ion etching.

Les trous destinés au logement des micropointes sont formés par une méthode de photolithographie. Pour cela, une couche de résine photosensible est étalée sur les conducteurs de grille ou les zones de la couche isolante 11 mises à nu, puis séchée en étuve. La couche de résine est insolée aux rayons ultraviolets à travers un masque opaque pourvu de trous correspondant aux trous à obtenir sur les conducteurs de grille et la couche isolante. Pour cela, le masque a été positionné par rapport au substrat pour obtenir les trous de grille aux emplacement voulus.The holes for the microtip housing are formed by a photolithography method. For this, a layer of photosensitive resin is spread over the grid conductors or the areas of the insulating layer 11 exposed, then dried in an oven. The resin layer is exposed to ultraviolet rays through an opaque mask provided with holes corresponding to the holes to be obtained on the grid conductors and the insulating layer. For this, the mask was positioned relative to the substrate to obtain the grid holes at the desired locations.

Le même masque de trous est utilisé pour tous les substrats. Dans le cas d'une insolation à proximité, ce masque est à l'échelle 1 et couvre toute la surface émissive. Dans le cas d'une insolation par photo-répéteur, il peut être à l'échelle 5 et ne couvrir qu'une fraction de la surface émissive. L'étape élémentaire d'insolation est alors répétée autant de fois qu'il est nécessaire pour couvrir toute la surface émissive.The same hole mask is used for all substrates. In the case of a sunstroke nearby, this mask is at scale 1 and covers the entire emissive surface. In the case of exposure by photo-repeater, it can be at scale 5 and cover only a fraction of the emissive surface. The elementary insolation step is then repeated as many times as necessary to cover the entire emissive surface.

Après insolation, le substrat est trempé dans un bain de développeur afin d'ouvrir les trous dans la résine. Un procédé de gravure sèche permet de graver les trous dans les conducteurs de grille puis dans la couche isolante 11, la couche de résine servant de masque. Enfin, la couche de résine est enlevée par exemple par un procédé chimique humide.After exposure, the substrate is soaked in a developer bath in order to open the holes in the resin. A dry etching process makes it possible to etch the holes in the grid conductors and then in the insulating layer 11, the resin layer serving as a mask. Finally, the resin layer is removed, for example by a wet chemical process.

La formation des micropointes s'effectue en trois étapes. On dépose d'abord une couche de nickel par évaporation sous vide et sous forte incidence par rapport à la perpendiculaire au substrat de manière que le nickel se dépose uniquement sur la face supérieure de la structure et sur les flancs des trous de la grille précédemment gravés dans la structure mais pas au fond des trous réalisés dans l'isolant. Par évaporation sous vide, on dépose le matériau devant former les pointes 19 suivant une direction perpendiculaire au substrat de façon à déposer ce matériau sur la couche de nickel déposée précédemment et également au fond des trous. Au fur et à mesure de la croissance de cette nouvelle couche (par exemple en molybdène), les trous se bouchent progressivement et il se forme un cône (une micropointe) dans chaque trou. Le dépôt est arrêté lorsque les trous sont bouchés.The formation of microtips occurs in three stages. A layer of nickel is first deposited by evaporation under vacuum and at high incidence relative to the perpendicular to the substrate so that the nickel is deposited only on the upper face of the structure and on the flanks of the holes of the grid previously etched. in the structure but not at the bottom of the holes made in the insulation. By evaporation under vacuum, the material which is to form the points 19 is deposited in a direction perpendicular to the substrate so as to deposit this material on the nickel layer previously deposited and also at the bottom of the holes. As this new layer (for example molybdenum) grows, the holes gradually become blocked and a cone (microtip) is formed in each hole. The deposit is stopped when the holes are plugged.

La couche de nickel est ensuite dissoute par un procédé électrochimique, ce qui permet d'évacuer la couche en molybdène qu'elle supporte sur la face supérieure de la structure, tout en conservant les pointes dans les trous. Les pointes sont donc centrées automatiquement dans les trous. Leur hauteur dépend de l'angle du cône qui est lié aux paramètres de dépôt et également au diamètre des trous. A angle de cône constant, plus les trous sont larges, plus les pointes sont hautes et inversement.The nickel layer is then dissolved by an electrochemical process, which makes it possible to evacuate the molybdenum layer which it supports on the upper face of the structure, while keeping the tips in the holes. The points are therefore automatically centered in the holes. Their height depends on the angle of the cone which is linked to the deposition parameters and also to the diameter of the holes. At a constant cone angle, the wider the holes, the higher the points and vice versa.

Une émission inhomogène d'une cathode à micropointes peut être liée à une variation trop importante du diamètre des trous sur la structure constituant la cathode. Si par exemple l'insolation a été réalisée avec un photo-répéteur qui refait sa mise au point à chaque étape, cette mise au point peut être perturbée localement par des défauts de planéité du substrat. Il en résulte par exemple que certaines zones de la structure tombent en dehors de la profondeur de champ et, en conséquence, les trous sortent trop petits. Pour remédier à ce défaut, on mélange sur la surface émissive, des trous de différents diamètres de façon à avoir toujours un certain nombre de micro-émetteurs qui émettent à leur niveau optimum. Le niveau d'émission global est diminué mais il est homogène.An inhomogeneous emission from a microtip cathode can be linked to a variation too significant diameter of the holes on the structure constituting the cathode. If, for example, the exposure was carried out with a photo-repeater which remakes its focusing at each stage, this focusing can be disturbed locally by defects in the flatness of the substrate. As a result, for example, certain areas of the structure fall outside the depth of field and, as a result, the holes come out too small. To remedy this defect, holes of different diameters are mixed on the emissive surface so as to always have a certain number of micro-emitters which emit at their optimum level. The overall emission level is reduced but it is homogeneous.

La correction a faire intervenir sur le masque consiste donc à le pourvoir de trous de différents diamètres régulièrement répartis sur la surface émissive. La figure 4 montre une partie d'un masque 30 destiné à la création de micro-trous dans une structure de cathode à micropointes utilisée pour un écran fluorescent. Cette partie du masque comprend trois ensembles adjacents de trous 31, 32 et 33, correspondant à trois mailles adjacentes définies par les conducteurs cathodiques sur la cathode. Ces trois mailles constituent un groupe élémentaire. Il faut plusieurs de ces groupes élémentaires pour contribuer à former un pixel sur l'écran.The correction to be made to the mask therefore consists in providing it with holes of different diameters regularly distributed over the emissive surface. FIG. 4 shows part of a mask 30 intended for the creation of micro-holes in a microtip cathode structure used for a fluorescent screen. This part of the mask comprises three adjacent sets of holes 31, 32 and 33, corresponding to three adjacent meshes defined by the cathode conductors on the cathode. These three meshes constitute an elementary group. Several of these elementary groups are needed to help form a pixel on the screen.

Chaque maille comprend par exemple seize micro-émetteurs qui émettent à leur niveau optimum lorsque le diamètre des micro-trous est de 1,3 µm comme il a été annoncé plus haut.Each mesh comprises for example sixteen micro-emitters which emit at their optimum level when the diameter of the micro-holes is 1.3 μm as announced above.

Sur le masque, l'ensemble 31 est formé de trous de 1,1 µm de diamètre, c'est-à-dire produisant théoriquement des trous de 1,1 µm sur la structure émissive. L'ensemble 32 est formé de trous de 1,3 µm de diamètre, c'est-à-dire produisant théoriquement des trous de 1,3 µm sur la structure émissive. L'ensemble 33 est formé de trous de 1,5 µm de diamètre, c'est-à-dire produisant théoriquement des trous de 1,5 µm sur la structure émissive. La structure émissive comprend donc une répartition également distribuée d'ensembles tels que 31, 32 et 33.On the mask, the assembly 31 is formed of holes of 1.1 μm in diameter, that is to say theoretically producing holes of 1.1 μm on the emissive structure. The assembly 32 is formed of 1.3 μm holes in diameter, that is to say theoretically producing 1.3 µm holes on the emissive structure. The assembly 33 is formed of holes of 1.5 μm in diameter, that is to say theoretically producing holes of 1.5 μm on the emissive structure. The emissive structure therefore comprises an equally distributed distribution of assemblies such as 31, 32 and 33.

Dans les zones de la structure émissive où le report des trous du masque a été correctement effectué, ce sont les micro-émetteurs correspondant aux ensembles 32 qui émettront de façon optimum. Les autres micro-émetteurs, correspondant aux ensembles 31 et 33 auront une émission très réduite. Si dans d'autres zones de la structure émissive le report des trous du masque a été mal effectué et qu'il en résulte une augmentation de diamètre des micro-trous de la source d'électrons de 0,2 µm, ce sont les micro-émetteurs correspondant aux ensembles 31 qui émettront de façon optimum. Les autres micro-émetteurs, correspondant aux ensembles 32 et 33 auront une émission très réduite. Le même raisonnement peut être repris pour les ensembles 33 en cas de diminution de diamètre de 0,2 µm. Il en résulte que l'on a toujours le même nombre de micro-émetteurs émettant de façon optimum répartis uniformément sur l'ensemble de la source qui émet ainsi de façon homogène.In the areas of the emissive structure where the transfer of the mask holes has been correctly carried out, it is the micro-emitters corresponding to the assemblies 32 which will emit in an optimum manner. The other micro-transmitters, corresponding to sets 31 and 33 will have a very reduced emission. If in other areas of the emissive structure the transfer of the holes of the mask was badly carried out and that results in an increase in diameter of the micro-holes of the electron source of 0.2 µm, these are the micro transmitters corresponding to the assemblies 31 which will emit in an optimum manner. The other micro-transmitters, corresponding to sets 32 and 33 will have a very reduced emission. The same reasoning can be used for sets 33 in the event of a 0.2 µm diameter reduction. As a result, there is always the same number of micro-emitters emitting optimally distributed uniformly over the entire source which thus emits homogeneously.

Il entre bien sûr dans le cadre de la présente invention de mélanger sur le masque plus que trois diamètres différents de trous.It is of course within the scope of the present invention to mix on the mask more than three different hole diameters.

Une émission inhomogène d'une cathode à micropointes peut aussi être liée à une altération de la forme des trous reportés sur la structure émissive. Une aberration de l'optique de l'équipement d'insolation peut conduire à l'obtention de trous ovales inclinés par exemple à 45° sur la gauche. Ainsi, à partir d'un masque possédant uniformément des trous ronds on peut obtenir sur la structure émissive des zones à trous ronds correspondant à une optique sans aberration et des zones à trous tous ovales et également inclinés et correspondant à une optique avec aberration.An inhomogeneous emission from a microtip cathode can also be linked to an alteration in the shape of the holes transferred to the emissive structure. An aberration of the optics of the exposure equipment can lead to obtaining oval holes inclined for example at 45 ° to the left. So from a mask having uniformly round holes one can obtain on the emissive structure zones with round holes corresponding to an optic without aberration and zones with holes all oval and also inclined and corresponding to an optic with aberration.

La correction à faire intervenir sur le masque consiste alors à mélanger régulièrement, sur toute la surface du masque, des trous ronds avec des trous ovales inclinés à 45° sur la droite. La figure 5 montre une partie d'un tel masque correcteur et représentant un ensemble de seize trous correspondant à une maille de la structure émissive. On remarque que cet ensemble comprend huit trous ronds 41 et huit trous ovales 42 inclinés à droite, les trous ronds et ovales étant régulièrement répartis. Sur le masque, tous les ensembles de trous sont identiques à ceux représentés à la figure 5.The correction to be made on the mask then consists of regularly mixing, over the entire surface of the mask, round holes with oval holes inclined at 45 ° to the right. FIG. 5 shows part of such a corrective mask and representing a set of sixteen holes corresponding to a mesh of the emissive structure. It is noted that this assembly comprises eight round holes 41 and eight oval holes 42 inclined to the right, the round and oval holes being regularly distributed. On the mask, all the sets of holes are identical to those shown in Figure 5.

Lors du report sur la structure émissive, dans les zones correspondant à une optique sans aberration, les trous reproduits sur la structure émissive seront identiques à ceux de la partie correspondante du masque. Dans les zones correspondant à une optique avec aberration, les trous reproduits sur la structure émissive seront déformés par rapport à ceux de la partie correspondante du masque. La figure 6 représente dans ce cas les formes de trous reproduits sur une maille 45 de la structure émissive par les trous du masque 40 de la figure 5. Aux trous circulaires 41 du masque correspondent sur la structure émissive des trous ovales 46 inclinés sur la gauche. Aux trous ovales 42 inclinés sur la droite correspondent sur la structure émissive des trous circulaires 47.When transferring to the emissive structure, in the zones corresponding to an optic without aberration, the holes reproduced on the emissive structure will be identical to those of the corresponding part of the mask. In the zones corresponding to an aberration optic, the holes reproduced on the emissive structure will be deformed compared to those of the corresponding part of the mask. FIG. 6 in this case represents the shapes of holes reproduced on a mesh 45 of the emissive structure by the holes of the mask 40 of FIG. 5. The circular holes 41 of the mask correspond to the emissive structure of the oval holes 46 inclined to the left . The oval holes 42 inclined to the right correspond to the emissive structure of the circular holes 47.

Le bilan des trous sur l'ensemble de la structure émissive révèle autant de trous ovales inclinés que de trous ronds, les trous ovales inclinés à gauche et à droite donnant le même niveau d'émission pour les micro-émetteurs. On comprend bien que le niveau d'émission de la cathode est homogène sur toute la surface émissive.The balance of the holes on the whole of the emissive structure reveals as many inclined oval holes as round holes, the oval holes inclined to the left and on the right giving the same emission level for micro-transmitters. It will be understood that the emission level from the cathode is homogeneous over the entire emissive surface.

Une émission inhomogène d'une cathode à micropointes peut encore être liée à un trop mauvais positionnement des grilles par rapport aux micropointes. Dans certains cas, le désalignement est suffisamment important (supérieur à 2 µm) pour que des trous se trouvent en dehors des zones élargies qui leur sont réservées dans la grille. La figure 7 donne un exemple d'un tel désalignement. La zone élargie et carrée 17 n'est pas centrée dans la maille 21 définie par le conducteur cathodique 3. Sur les seize micro-émetteurs représentés, sept sont en dehors de la zone 17 et n'émettent pas.An inhomogeneous emission from a microtip cathode can also be linked to an incorrect positioning of the grids relative to the microtips. In some cases, the misalignment is large enough (greater than 2 µm) so that holes are outside the enlarged areas reserved for them in the grid. Figure 7 gives an example of such a misalignment. The enlarged and square area 17 is not centered in the mesh 21 defined by the cathode conductor 3. Of the sixteen micro-transmitters shown, seven are outside the area 17 and do not emit.

Pour remédier à ce défaut, on agrandit dans la maille la zone couverte par les trous 18 au delà de la zone carrée 17 de façon que si cette zone 17 est décentrée dans la maille, elle recouvre malgré tout toujours le même nombre de micropointes. Pour cela, il suffit d'augmenter le nombre de trous dans le masque de manière à reporter le nombre de trous voulu. A titre d'exemple pour avoir toujours seize micro-émetteurs en fonctionnement, on peut, pour une maille, prévoir 36 trous disposés en carré sur la partie correspondante du masque. La figure 8 montre le résultat obtenu pour une zone carrée 17 centrée dans la maille 21. La figure 9 montre le résultat obtenu pour une zone carrée 17 décentrée par rapport à la maille 21. Dans les deux cas, il y a toujours seize micro-émetteurs en fonctionnement.To remedy this defect, the area covered by the holes 18 is enlarged in the mesh beyond the square area 17 so that if this area 17 is off-center in the mesh, it still covers the same number of microtips. To do this, simply increase the number of holes in the mask so as to transfer the desired number of holes. By way of example, to always have sixteen micro-transmitters in operation, it is possible, for a mesh, to provide 36 holes arranged in a square on the corresponding part of the mask. Figure 8 shows the result obtained for a square area 17 centered in the mesh 21. Figure 9 shows the result obtained for a square area 17 offset from the mesh 21. In both cases, there are always sixteen micro- transmitters in operation.

Il entre dans le cadre de l'invention de combiner, le cas échéant, sur un même masque les différentes corrections à apporter au masque pour résoudre plusieurs problèmes, par exemple pour corriger des défauts dus à un manque de planéité du substrat, ceux dus à une aberration de l'optique de l'équipement d'insolation et ceux dus à des problèmes d'alignement.It is within the scope of the invention to combine, where appropriate, on the same mask the various corrections to be made to the mask for solve several problems, for example to correct defects due to a lack of flatness of the substrate, those due to an aberration of the optics of the exposure equipment and those due to alignment problems.

Par ailleurs, même si l'invention a été décrite à titre d'exemple avec une source comportant des électrodes en treillis, celle-ci s'applique bien entendu à tous les types de sources d'électrons à micropointes.Furthermore, even if the invention has been described by way of example with a source comprising lattice electrodes, this naturally applies to all types of microtip electron sources.

Claims (5)

  1. Process for the production of a microtip electron source, the microtips (19) being electrically connected to at least one cathode conductor (3) and being located in holes (18) made in at least one electron extraction grid, the process using a masking stage for producing the holes in the grid (13) by means of a mask (30,40) having corresponding holes, the holes in the mask having given dimensions and shapes in order to theoretically lead to the obtaining of holes in the grid having dimensions, shapes and positions within the given tolerances, the apices of the microtips (19) being located in the thickness of the grid (13),characterized in that after producing an electron source according to said process:
    - an evaluation is made to establish whether the source has an emission which is sufficiently homogeneous and/or reproducible and/or reproducible on another source,
    - if the emission of the source is considered to be inhomogeneous and/or non-reproducible, a determination takes place of the defects leading to said inhomogeneous emission and which are due to shapes, dimensions or positions of the holes falling outside the tolerances or because the apices of the microtips are not located in the thickness of the grid,
    - the mask used is then corrected in order to render homogeneous and/or reproducible the future sources produced by said process, the correction consisting of modifying the shapes and/or dimensions of at least certain holes in the mask and/or the number of holes in the mask in order to compensate for the previously determined defects by deliberately creating supplementary defects and/or holes, regularly distributed over the emissive surface in such a way that there is always the same number of micropoints emitting in optimum manner uniformly distributed over the entire source.
  2. Improvement according to claim 1, characterized in that if the defects are due to a variation outside the diameter tolerances of the grid holes, the mask (30) is corrected so as to provide it over its entire surface with holes (31,32,33) having diameters varying in accordance with a distribution making it possible to include these manufacturing defects.
  3. Improvement according to either of the claims 1 and 2,
    characterized in that if the defects are due to the presence of oval grid holes, the mask (40) is corrected so as to provide it over its entire surface with circular holes (41) and oval holes (42), whose major axes are located in the direction of the minor axes of the oval holes of the defective grid, the circular and oval correcting holes being regularly mixed on the mask.
  4. Improvement according to any one of the claims 1 to 3,
    characterized in that if the defects are due to an unsatisfactory positioning of the holes with respect to the grid (17) there is an increase in the number of holes (18) in the mask in such a way that the grid of the future sources will be provided with a number of holes equivalent to a satisfactory positioning of the holes with respect to the grid.
  5. Improvement according to any one of the preceding claims,
    characterized in that the hole production process is a photolithographic process.
EP94401582A 1993-07-12 1994-07-08 Manufacturing method for micropoint electron sources Expired - Lifetime EP0634769B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9308556 1993-07-12
FR9308556A FR2707795B1 (en) 1993-07-12 1993-07-12 Improvement to a manufacturing process of a microtip electron source.

Publications (2)

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EP0634769A1 EP0634769A1 (en) 1995-01-18
EP0634769B1 true EP0634769B1 (en) 1996-09-18

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EP (1) EP0634769B1 (en)
JP (1) JPH0729485A (en)
DE (1) DE69400562T2 (en)
FR (1) FR2707795B1 (en)

Families Citing this family (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5731228A (en) 1994-03-11 1998-03-24 Fujitsu Limited Method for making micro electron beam source
US5542866A (en) * 1994-12-27 1996-08-06 Industrial Technology Research Institute Field emission display provided with repair capability of defects
US5589728A (en) * 1995-05-30 1996-12-31 Texas Instruments Incorporated Field emission device with lattice vacancy post-supported gate
US5686782A (en) * 1995-05-30 1997-11-11 Texas Instruments Incorporated Field emission device with suspended gate
US5621272A (en) * 1995-05-30 1997-04-15 Texas Instruments Incorporated Field emission device with over-etched gate dielectric
FR2736465B1 (en) * 1995-07-03 1997-08-08 Commissariat Energie Atomique DEVICE FOR STARTING AND/OR MAINTAINING A DISCHARGE AND COLD CATHODE VACUUM GAUGE COMPRISING SUCH A DEVICE
FR2737927B1 (en) * 1995-08-17 1997-09-12 Commissariat Energie Atomique METHOD AND DEVICE FOR FORMING HOLES IN A LAYER OF PHOTOSENSITIVE MATERIAL, PARTICULARLY FOR THE MANUFACTURE OF ELECTRON SOURCES
US5746634A (en) * 1996-04-03 1998-05-05 The Regents Of The University Of California Process system and method for fabricating submicron field emission cathodes
US6611093B1 (en) * 2000-09-19 2003-08-26 Display Research Laboratories, Inc. Field emission display with transparent cathode
US6545422B1 (en) * 2000-10-27 2003-04-08 Science Applications International Corporation Socket for use with a micro-component in a light-emitting panel
US6620012B1 (en) * 2000-10-27 2003-09-16 Science Applications International Corporation Method for testing a light-emitting panel and the components therein
US6612889B1 (en) 2000-10-27 2003-09-02 Science Applications International Corporation Method for making a light-emitting panel
US6822626B2 (en) * 2000-10-27 2004-11-23 Science Applications International Corporation Design, fabrication, testing, and conditioning of micro-components for use in a light-emitting panel
US7288014B1 (en) 2000-10-27 2007-10-30 Science Applications International Corporation Design, fabrication, testing, and conditioning of micro-components for use in a light-emitting panel
US9159527B2 (en) * 2003-10-16 2015-10-13 Carl Zeiss Microscopy, Llc Systems and methods for a gas field ionization source
FR2873852B1 (en) * 2004-07-28 2011-06-24 Commissariat Energie Atomique HIGH RESOLUTION CATHODE STRUCTURE
JP6953917B2 (en) * 2017-09-01 2021-10-27 王子ホールディングス株式会社 Anti-reflective structure

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3817592A (en) * 1972-09-29 1974-06-18 Linfield Res Inst Method for reproducibly fabricating and using stable thermal-field emission cathodes
US4324999A (en) * 1980-04-30 1982-04-13 Burroughs Corporation Electron-beam cathode having a uniform emission pattern
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
FR2663462B1 (en) * 1990-06-13 1992-09-11 Commissariat Energie Atomique SOURCE OF ELECTRON WITH EMISSIVE MICROPOINT CATHODES.
FR2687839B1 (en) * 1992-02-26 1994-04-08 Commissariat A Energie Atomique ELECTRON SOURCE WITH MICROPOINT EMISSIVE CATHODES AND FIELD EMISSION-EXCITED CATHODOLUMINESCENCE VISUALIZATION DEVICE USING THE SOURCE.

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Publication number Publication date
FR2707795B1 (en) 1995-08-11
FR2707795A1 (en) 1995-01-20
DE69400562T2 (en) 1997-03-27
DE69400562D1 (en) 1996-10-24
US5482486A (en) 1996-01-09
EP0634769A1 (en) 1995-01-18
JPH0729485A (en) 1995-01-31

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