Classifications

• • 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
  • H01J3/00—Details of electron-optical or ion-optical arrangements common to two or more basic types of discharge tubes or lamps
  • H01J3/02—Electron guns
  • H01J3/021—Electron guns using a field emission, photo emission, or secondary emission electron source
  • H01J3/022—Electron guns using a field emission, photo emission, or secondary emission electron source with microengineered cathode, e.g. Spindt-type
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2329/00—Electron emission display panels, e.g. field emission display panels

Definitions

• the present invention relates to a method for manufacturing a microtip electron source, with a self-aligned focusing grid.
• a source of microtip electrons can in particular be used in a display device by cathodoluminescence excited by field emission.
• the documents FR-A-2 593 953 and FR-A-2 623 013 disclose display devices by cathodoluminescence excited by field emission. These devices include an electron source with microtip emissive cathodes.
• FIG. 1 is a cross-sectional view of such a microtip display screen.
• the screen consists of a cathode 1, which is a planar structure, placed opposite another planar structure forming the anode 2.
• the cathode 1 and the anode 2 are separated by a space in which the empty.
• the cathode 1 comprises a glass substrate 11 on which is deposited the conductive level 12 in contact with the electron emitting tips 13.
• the conductive level 12 is covered with an insulating layer 14, for example made of silica, itself covered of a conductive layer 15.
• the anode 2 comprises a transparent substrate 21 covered with a transparent electrode 22 on which are deposited luminescent phosphors or phosphors 23.
• the anode 2 is brought to a positive voltage of several hundred volts with respect to the tips 13 (typically 200 to 500 V).
• a positive voltage of a few tens of volts (typically 60 to 100 V) is applied relative to the tips 13.
• Electrons are then torn off from the tips 13 and are attracted by the anode 2.
• the trajectories electrons are included in a cone with a half-angle at the apex ⁇ depending on different parameters, among others the shape of the tips 13. This angle causes a defocusing of the electron beam 31 all the more important as the distance between the anode and the cathode is large.
• FIG. 2 illustrates the case where the focusing grid is placed on the cathode.
• Figure 2 shows the example of Figure 1 but limited to a single microtip for clarity in the drawing.
• Simulation calculations show that the centering of the holes 19 of the focusing grid with respect to the holes 18 of the extraction grid is extremely critical.
• This structure is generally produced with the conventional photolithography techniques used in microelectronics.
• a first level of photolithography the holes 19 of the focusing grid are defined, then a second level of photolithography makes it possible to produce the holes 18 in which the points will be placed.
• the second level must be positioned extremely precisely in relation to the first level. This can only be achieved with very efficient and therefore very expensive equipment, which will be all the more disadvantageous when dealing with large areas.
• the holes of the extraction grid are made by photolithography from a network of microbeads, their arrangement is random, which prohibits the use of a photomask to make the openings of the focusing grid.
• the invention makes it possible to remedy the problem of precision of alignment of holes situated at different levels. This is obtained by means of a process which requires only one photolithography step, that making it possible to make the holes in the extraction grid.
• the subject of the invention is therefore a method of manufacturing a source of electrons with microtips, with an extraction grid and with a focusing grid, comprising:
• the cathodic connection means are obtained by depositing cathodic conductors on the support, followed by depositing a resistive layer.
• a first way of etching the second insulating layer is to proceed as follows:
• the etching of the holes in the first insulating layer can first be carried out anisotropically, said housings then being defined by isotropic etching.
• a second way of etching the second insulating layer consists in proceeding as follows.
• the first and second insulating layers being able to be etched simultaneously, the etching of the second insulating layer is first carried out isotropically to obtain blanks of cavities, reach the first conductive layer and reveal there areas allowing the holes to be made. of the extraction grid, the holes of the extraction grid then being etched in the first conductive layer, an isotropic etching is finally continued to simultaneously obtain said housings in the first insulating layer and said cavities to said dimension in the second layer insulating.
• FIG. 3A to 3F illustrate the manufacture of a microtip electron source according to a first way of implementing the method of the present invention
• FIG. 4A to 4D illustrate the manufacture of a source of microtip electrons according to a second way of implementing the method of the present invention
• FIG. 5 is a partial perspective view of a microtip electron source produced by the method according to the present invention and the microtips of which are arranged in lines, the distance between the adjacent microtips of the same line being less the diameter of the holes in the focusing grid;
• FIG. 6 is a partial perspective view of a microtip electron source produced by the method according to the present invention, the distance between two adjacent microtips being greater than the diameter of the holes of the focusing grid.
• FIGS. 3A to 3F are cross-section views of a source of electron microdots during manufacture according to a first embodiment of the method according to the invention.
• a metal layer is deposited (see FIG. 3A) which is etched to form cathode conductors 51 parallel to each other. These cathode conductors 51 will serve, for example, as columns for a matrix display.
• a resistive layer 52 is then deposited uniformly.
• a first insulating layer 53 is successively deposited, a first conductive layer 54 intended to constitute the grid for extracting the microtip electron source, a second insulating layer 55 and a second conductive layer 56 intended to constitute the focus grid.
• the thicknesses of the insulating layers 53 and 55 are chosen as a function of the height provided for the microtips and of the distance which must separate the extraction grid from the focusing grid.
• a layer of photosensitive resin 57 is then uniformly deposited on the second conductive layer 56.
• the layer of photosensitive resin 57 is exposed through a mask and then developed to make holes 58 therein with axes corresponding to the axes of the microtips to be formed (see FIG. 3B where a single hole 58 has been shown). These holes allow the etching of the underlying layers.
• the holes 58 are extended by holes 59 etched in the second conductive layer 56, which in turn are extended by holes 60 etched in the second insulating layer 55.
• the etching of the holes 61 is then continued in the first conductive layer 54 in order to reveal the first insulating layer 53.
• the holes 61 are then extended, by etching, of holes 62 made in the first insulating layer 53 until reaching the resistive layer 52 which is thus revealed.
• the holes 62 made in the first insulating layer 53 are widened by isotropic etching.
• the second conductive layer 56 is etched so as to widen the holes in this layer up to the dimension of the cavities 68 of the second insulating layer 55.
• the openings 64 of the focusing grid are thus obtained.
• each opening 64 of the focusing grid 66 is perfectly aligned with the corresponding hole 61 of the extraction grid 65.
• the last step of the method consists in producing the microtips by a method known to man art. Each microtip 67 is thus perfectly aligned on the axis of the corresponding hole 61 of the extraction grid 65 and on the axis of the corresponding opening 64 of the focusing grid 66.
• the second conductive layer 56 is etched so as to widen the holes in this layer up to the maximum dimension of the cavities 72 of the second insulating layer 55.
• the openings 64 of the focusing grid are thus obtained.
• microtips 67 can be deposited on the resistive layer 52.
• Each microtip 67 is thus perfectly aligned on the axis of the corresponding hole 61 of the extraction grid 65 and on the axis of the corresponding opening 64 of the focusing grid 66.
• FIG. 5 shows an example of a microtip electron source obtained by the first embodiment of the method of the present invention.
• the holes 61 of the extraction grid 65 and the microtips 67 are arranged in parallel lines. The distance separating two successive holes 61 of the same line is less than the opening 64 of the focusing grid 66. The distance between two lines of adjacent microtips is greater than this opening. Widening of holes in layers 55 and 56 to the desired diameter for the focusing grid 66 makes these holes intersect.
• the openings of the focusing grid corresponding to the same line of microtips 67 then constitute slots with scalloped edges, the axes of these slots being coincident with the lines on which the corresponding microtips are arranged.
• the focusing of the electrons is done only in the direction perpendicular to the planes of symmetry of the slits.
• the phosphors placed on the anode which, in the display device, faces the cathode must then be arranged in lines parallel to the lines of emitters.
• FIG. 6 shows another example of microtip electron sources obtained by the first embodiment of the present invention.
• the holes 61 of the extraction grid 65 are located relative to each other at a distance greater than the diameter of the openings 64 of the focusing grid 66.
• the openings 64 of the focusing grid 66 are holes concentric with the holes 61 of the extraction grid 65. The electrons emitted by the microtips 67 are then focused whatever their direction of emission.

Landscapes

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

Applications Claiming Priority (3)

Publications (2)

Family

ID=9526714

Family Applications (1)

Country Status (6)

Families Citing this family (8)

Family Cites Families (7)

• 1998
  • 1998-05-26 FR FR9806607A patent/FR2779271B1/fr not_active Expired - Fee Related
• 1999
  • 1999-05-25 DE DE69909708T patent/DE69909708T2/de not_active Expired - Fee Related
  • 1999-05-25 EP EP99920914A patent/EP1000433B1/de not_active Expired - Lifetime
  • 1999-05-25 JP JP2000551412A patent/JP2002517065A/ja not_active Withdrawn
  • 1999-05-25 WO PCT/FR1999/001218 patent/WO1999062093A1/fr not_active Ceased
  • 1999-05-25 US US09/463,383 patent/US6210246B1/en not_active Expired - Fee Related

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events