JP4851735B2 - Field emission cold cathode device - Google Patents

Description

  The present invention relates to a field emission cold cathode device in which a plurality of emitters are arranged on a substrate surface used for a flat image display device, an electron beam device, an illumination device, and the like.

  As is well known, the field electron emission phenomenon adds a large electric field strength to the tip of an emitter having a sharp shape, and when the potential potential of the tip surface exceeds the work function of the emitter material, electrons are emitted from the tip surface by the tunnel effect. It is a phenomenon. As a device for emitting electrons using this phenomenon, a plurality of emitters are disposed on the substrate, an anode electrode is disposed opposite to the emitter, and a gate electrode is provided between the emitter and the anode electrode as necessary. Field emission type cold cathode devices in which the above are arranged have been developed. Further, in such a field emission type cold cathode device, the radius of curvature of the tip portion is reduced and sharpened so that a large electric field strength can be added to the emitter. The radius of curvature of a (substantially) quadrangular pyramid emitter is about several tens of nanometers, and that using carbon nanotubes is several nanometers.

For example, as a method of providing a plurality of substantially quadrangular pyramidal emitters on the substrate surface, a p-type (100) crystal orientation Si single crystal substrate may be used by using a pattern having a square opening (for example, 1 μm square). By performing isotropic etching to form a substantially quadrangular pyramid-shaped recess and further providing a SiO ₂ layer including the inside of the recess, any one of sputtering, vapor deposition, printing, electroplating, etc. is used. For example, a metal layer is formed by laminating a metal such as Ni so as to fill the recess, and the substrate is bonded to the metal layer, and then the Si substrate is etched away to form a number of sharp convex shapes that form a substantially quadrangular pyramid. A master mold substrate is obtained, and a mold mold substrate is produced using the formed master substrate. Thereafter, the mold mold substrate has a plurality of substantially quadrangular pyramidal emitters used in a field emission cold cathode device. Method of obtaining a plate is shown (for example, see Patent Document 1).

  In addition, an Si substrate having a substantially quadrangular pyramid-shaped recess is used as a master substrate, a metal layer is formed by depositing metal so as to fill the recess by plating, and a master formed of the metal layer and Si by water pressure or the like. There is also a method for producing a mold mold substrate by separating from the substrate. For example, when a plating method is used as the metal material of the mold mold substrate, there are Mo, Ta, W, Cr, Ni, Cu and the like.

  Under such circumstances, in the case where a plurality of emitters are arranged on the substrate, the sharp tip of the emitter is damaged in the process of producing a substantially quadrangular pyramid emitter or the process of aging the produced emitter, for example. Since there are emitters that do not emit electrons due to trapping or damage to the emitter itself, the number of emitters arranged per unit area can be increased to further increase the field emission area and increase the current density per unit area. Increasingly, high integration has been performed. For example, in the device described in Patent Document 1, the arrangement interval of the emitters is approximately equal to the base length of the quadrangular pyramid emitter and is about 1.4 times the height.

  However, when a plurality of emitters are arranged and a locally high emitter exists, a large electric field is applied only to the high emitter, and electrons are emitted from that emitter, but from other emitters. Makes it difficult for electrons to be emitted. For this reason, it has been possible to make the height of the emitter uniform by destroying a locally high emitter by discharge or the like, and to add a large electric field strength to the entire emitter to increase the electron emission area.

  However, when such a measure is taken, it is difficult to limit the portion destroyed by the discharge, and there is a possibility that the emitter material may be scattered by the discharge destruction other than the destroyed portion and the healthy emitter may be damaged. . For example, if the tip of the emitter that is healthy is damaged and a shape change occurs, the uniformity of field emission becomes poor, and the yield of the healthy emitter is deteriorated. When the field emission type cold cathode device is configured such that an emitter portion is formed by a plurality of emitters and a plurality of emitter portions are provided on the same substrate, the characteristics of each emitter portion are uniformed. When trying to make it, there was a risk that it would be very expensive.

In addition, when multiple emitters with different heights are arranged on the substrate and the intervals between adjacent emitters are narrowed for high integration, the sharpened portions of the emitters are too close to concentrate the electric field. Is difficult to occur, and high electric field strength cannot be obtained. For this reason, it is conceivable to reduce the distance between the anode electrode and the emitter so that a high electric field strength can be obtained, but when the anode electrode and the emitter are brought close to each other in this way, electrons (primary electrons) emitted from the emitter are There is a risk that the emitter may be damaged by the influence of electrons (secondary electrons), ions, sputtering, etc. generated by colliding with the anode electrode.
JP 2000-285798 A (pages 3 to 4)

The present invention has been made in view of the situation as described above.
When arranging a plurality of emitters, by making the interval between adjacent emitters appropriate, it is possible to eliminate the difficulty of electric field concentration and to obtain a high electric field strength. The object is to provide a field emission cold cathode device capable of reducing the damage of the emitter due to secondary electrons or the like generated in the anode electrode by obtaining a high electric field strength without reducing the separation distance,
Another object of the present invention is to provide a field emission cold cathode device in which a plurality of emitters can be arranged on the same substrate surface while maintaining an appropriate distance between adjacent emitters so that electric field concentration does not easily occur.

The field emission cold cathode device of the present invention comprises:
While a predetermined vacuum state is maintained, a plurality of emitters having a sharp tip with a predetermined separation distance are disposed opposite to an anode electrode, and a predetermined potential is applied between the plurality of emitters and the anode electrode. A field emission cold cathode device in which electrons are emitted,
Each of the plurality of emitters has a substantially quadrangular pyramid shape with a height H of H = X tan (55 °) / 2 with respect to the length X of the bottom side of the bottom formed in a square shape, and has substantially the same height. Are arranged at equal intervals on the same substrate surface, and the interval between adjacent ones is 3.5 times or more the height H of the emitter,
A plurality of substantially quadrangular pyramid-shaped emitters protruding on the same surface of the substrate at substantially the same predetermined height and at equal intervals; and an anode electrode disposed at a predetermined distance from these emitters; In a field emission cold cathode device comprising:
Each of the plurality of emitters has a height H of H = X tan (55 °) / 2 with respect to the length X of the bottom side of the bottom formed in a square shape, and the interval between adjacent ones is the emitter. It is characterized by being at least 2.5 times the length X of the bottom side of
Further, the plurality of emitters are arranged at positions that are vertices of equilateral triangles on the substrate surface, respectively.

According to the present invention,
When arranging multiple emitters, the distance between adjacent emitters becomes appropriate, electric field concentration is likely to occur, and high electric field strength can be obtained. To obtain higher electric field strength, the separation distance between the anode electrode and the emitter Therefore, it is possible to reduce damage to the emitter due to secondary electrons generated in the anode electrode.
In addition, a large number of emitters can be densely arranged on the same substrate surface while preventing the concentration of the electric field from easily occurring, and the current density can be increased.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, a first embodiment will be described with reference to FIGS. 1 is a cross-sectional view schematically showing a schematic configuration, FIG. 2 is a perspective view of a cathode electrode, and FIG. 3 is a characteristic diagram showing electric field strength characteristics based on analysis results.

1 and 2, the field emission cold cathode device 1 includes a vacuum space 4 in which a cathode electrode 2 and an anode electrode 3 are maintained in a high vacuum state of, for example, about 10 ⁻⁶ Torr. By applying a predetermined potential difference between the cathode electrode 2 and the anode electrode 3, electrons are emitted from the cathode electrode 2 toward the anode electrode 3. In addition, the cathode electrode 2 is provided with an emitter substrate 7 that also serves as a cathode wiring on the surface of the support substrate 6 made of glass, for example, on the anode electrode 3 side. For example, a plurality of emitters 8 having a sharp tip having a radius of curvature of about several tens of nanometers are formed in a protruding manner.

  The plurality of emitters 8 protruding from the emitter substrate 7 are arranged in a plurality of orthogonal row and column directions with a predetermined interval L between adjacent ones. The emitter substrate 7 and the emitter 8 projecting from the emitter substrate 7 are formed so that the surface portion facing the anode electrode 3 becomes a conductive portion. The conductive portion of the emitter substrate 7 and the emitter 8 includes, for example, Mo. A conductive material made of at least one material such as Ta, W, Cr, Ni, Cu or the like, or one of them as a main material is used.

  The plurality of substantially quadrangular pyramid-shaped emitters 8 projecting from the emitter substrate 7 is formed on a p-type (100) crystal orientation Si single crystal substrate as shown in, for example, the above-mentioned Patent Document 1. Then, anisotropic etching is performed to form a substantially quadrangular pyramid-shaped concave portion having an opening of, for example, a 1 μm square, and a master substrate having a number of sharp convex shapes that form a substantially quadrangular pyramid using the formed concave portion is obtained. Further, a mold mold substrate having a substantially quadrangular pyramid-shaped recess is produced using the master substrate, and then the substantially quadrangular pyramid-shaped convex mold is transferred to the resin sheet by the mold mold substrate, and further on the resin sheet. It is carried out by a method such as projecting by forming a conductive layer as a conductive part, or similarly, after obtaining a master substrate having a convex shape of a substantially quadrangular pyramid, this is pressed against a resin material and copied. Take and get It carried out by a method of providing the conductive material so as to fill the recess of the resin material.

  In addition, an Si substrate having a substantially quadrangular pyramid-shaped recess is used as a master substrate, a metal layer is formed by depositing metal so as to fill the recess by plating, and a master formed of the metal layer and Si by water pressure or the like. There is also a method for producing a mold mold substrate by separating from the substrate. For example, when a plating method is used as the metal material of the mold mold substrate, there are Mo, Ta, W, Cr, Ni, Cu and the like.

  In the present embodiment, the second method of the above is used, and sputtering is performed so as to fill the concave portion of the resin material, for example, Ni is deposited thicker than the depth of the concave portion, and the conductive portions of the emitter substrate 7 and the emitter 8 are formed. Formed. Note that a method such as a vapor deposition method, a printing method, or electroplating may be used instead of the sputtering method.

Further, in the case where the plurality of emitters 8 projecting from the emitter substrate 7 are formed by the anisotropic etching method using the crystal plane of the Si single crystal substrate, for example, each of the individual quadrangular pyramids is formed. The shape of the emitter 8 is the length X of the bottom side of the bottom formed in a square,
Height H is
H = Xtan (55 °) / 2
It becomes what becomes.

Here, the term of tan (55 °) is that when an Si single crystal substrate surface with a crystal orientation (100) is anisotropically etched, the inclination angle of the etched inclined surface with respect to the substrate surface is 55 °. Is reflected.

Further, with respect to the cathode electrode 2 in which a plurality of emitters 8 having such a shape are provided at a predetermined interval L, the ratio (L / X) between the interval L between adjacent emitters 8 and the base length X of the emitter 8 is changed. As a result, the analysis result of the electric field strength characteristic as shown in FIG. 3 was obtained. That is, when the ratio of the distance L to the base length X (L / X) is 2.5 or more, the electric field strength is a constant high value, and the ratio of the distance L to the base length X (L / X). In a state where is smaller than 2.5, the value of the electric field strength decreases as the value decreases. The substantially quadrangular pyramid-shaped emitter 8 obtained by the above forming method has the relationship of the above formula ( H = Xtan (55 °) / 2 ), so that the distance L between adjacent emitters 8 and the emitter 8 The electric field strength with respect to the ratio of the height H (L / H) takes a constant high value when the ratio of the distance L to the height H (L / H) is 3.5 or more and is smaller than 3.5. Then, it becomes so low that it becomes small.

  According to this result, when trying to arrange the emitters 8 at a high density, even if the interval L between the adjacent emitters 8 is reduced, a high electric field strength cannot be added to the tip of the sharp emitter 8. become. This is because the adjacent emitters 8 are affected by each other's electric field, so that the electric field concentration is hindered. Therefore, in order to provide a plurality of emitters 8 within the range not affected by each other's electric field, the interval L and the bottom side The length X ratio (L / X) needs to be 2.5 or more, in other words, the distance L to height H ratio (L / H) needs to be 3.5 or more. In order to add the electric field strength, the ratio of the distance L to the base length X (L / X) is 2.5 or more, or the ratio of the distance L to height H (L / H) is 3.5 or more. It will be preferable.

  As described above, by arranging the plurality of emitters 8 at an appropriate interval L, a high electric field strength can be added to the tip of the emitter 8 and electrons can be easily emitted. In addition, since a high electric field strength can be obtained without reducing the distance between the anode electrode 3 and the emitter 8, damage to the emitter 8 due to secondary electrons or the like generated at the anode electrode 3 can be reduced. The electron emission characteristics can be uniform over a wide range, and the drive voltage can be lowered. Further, aging for adding a high electric field strength conventionally takes many days, but a shorter period of time may be required, the number of days for manufacturing the device can be shortened, and the cost of the device can be reduced.

  Next, a second embodiment will be described with reference to FIGS. 4 is a cross-sectional view schematically showing a schematic configuration, FIG. 5 is a perspective view of the cathode electrode, and FIG. 6 is a plan view of the cathode electrode. In addition, the same code | symbol is attached | subjected to the same part as 1st Embodiment, description is abbreviate | omitted, and the structure of this embodiment different from 1st Embodiment is demonstrated.

  4 to 6, the field emission cold cathode device 11 of this embodiment is different from the first embodiment only in the arrangement pattern of the emitters 8 and forms a surface of the cathode electrode 12 facing the anode electrode 3. As shown in FIG. 6, a plurality of emitters 8 having a substantially quadrangular pyramid shape are provided on the emitter substrate 7 with a predetermined distance L between adjacent ones, as shown in FIG. It is arranged at the position that becomes the vertex of the shown equilateral triangle. That is, between adjacent ones of the emitters 8 arranged in the left-right direction, between adjacent ones of the emitters 8 arranged obliquely upward to the right by 60 degrees with respect to the left-right direction, and further to the left-right direction. An equal interval L is provided between adjacent emitters 8 arranged in the diagonally upper left direction of 60 degrees.

  The distance L between adjacent ones is such that the adjacent emitters 8 are not affected by each other's electric field with respect to the base length X and height H of each emitter 8. The ratio of X (L / X) is 2.5 or more, or the ratio of the distance L to the height H (L / H) is 3.5 or more.

  As a result, the same operations and effects as those of the first embodiment can be obtained, and the plurality of emitters 8 can be arranged with higher density, and the current density per unit area can be increased.

  In each of the above embodiments, in order to add a high electric field strength, the ratio of the distance L to the base length X (L / X) is 2.5 or more, or the ratio of the distance L to the height H (L / X). H) is preferably 3.5 or more, more preferably, the ratio of the distance L to the base length X (L / X) is 3.0 or more, and the ratio of the distance L to the height H (L / H), 4.2 or more is sufficient, and in terms of practical use, the ratio (L / X) of the distance L to the base length X is 2.0 or more, or the distance L, depending on the device. In terms of the ratio of the height H (L / H), it may be 2.8 or more. Furthermore, with respect to the interval L between the adjacent emitters 8, the upper limit of the allowable range may be appropriately set based on the equipment to be used, its specifications, performance, etc. in consideration of the space factor.

  In addition, each of the above embodiments is for the cathode electrode 2 provided independently on one support substrate 5, but it may be for the cathode electrode 2 provided independently on the same support substrate 5. Good. Furthermore, in the above-described embodiment, the substantially quadrangular pyramid-shaped emitter 7 has been described. However, the emitter 8 has a sharp tip formed of a conductive material, for example, a carbon nanotube standing on a substrate or the like. The same effect can be obtained even if the ratio of the arrangement interval L to the height H (L / H) is set as described above, such as a conical shape or a polygonal pyramid shape other than a quadrangular pyramid shape. Can do. Furthermore, depending on the application, a multipolar configuration of three or more electrodes in which one or a plurality of gate electrodes are arranged between the emitter 8 and the anode electrode 3, or a phosphor layer is provided on the surface of the anode electrode 3 facing the emitter 8. The same effect can be obtained even with a configuration such as that provided.

It is sectional drawing which shows typically schematic structure of the 1st Embodiment of this invention. It is a perspective view of the cathode electrode in the 1st Embodiment of this invention. It is a characteristic view which shows the electric field strength characteristic which concerns on the 1st Embodiment of this invention based on an analysis result. It is sectional drawing which shows typically schematic structure of the 2nd Embodiment of this invention. It is a perspective view of the cathode electrode in the 2nd Embodiment of this invention. It is a top view of the cathode electrode in the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 ... Field emission type cold cathode apparatus 2,12 ... Cathode electrode 3 ... Anode electrode 4 ... Vacuum space 8 ... Emitter H ... Height L ... Space | interval X ... Base length

Claims (3)

While a predetermined vacuum state is maintained, a plurality of emitters having a sharp tip with a predetermined separation distance are disposed opposite to an anode electrode, and a predetermined potential is applied between the plurality of emitters and the anode electrode. A field emission cold cathode device in which electrons are emitted,
Each of the plurality of emitters has a substantially quadrangular pyramid shape with a height H of H = X tan (55 °) / 2 with respect to the length X of the bottom side of the bottom formed in a square shape, and has substantially the same height. A field emission cold cathode device characterized in that the emitters are arranged at equal intervals on the same substrate surface, and the interval between adjacent ones is 3.5 times or more the height H of the emitter. . A plurality of substantially quadrangular pyramid-shaped emitters projecting at substantially equal predetermined heights on the same surface of the substrate, and an anode electrode disposed at a predetermined distance from the emitters; In the field emission cold cathode device,
Each of the plurality of emitters has a height H of H = X tan (55 °) / 2 with respect to the length X of the bottom side of the bottom formed in a square shape, and the interval between adjacent ones is the emitter. A field emission cold cathode device characterized in that it is 2.5 times or more the length X of the bottom of the cathode.   3. The field emission cold cathode device according to claim 1, wherein the plurality of emitters are arranged at positions corresponding to apexes of an equilateral triangle on the substrate surface. 4.

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