JP3568859B2 - Cold cathode and method of manufacturing the cold cathode - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cold cathode having an electron source whose tip diameter, density, and length are controlled, and particularly relates to a cold cathode that improves reliability and reduces manufacturing cost, and includes a cold cathode lamp and a fluorescent display. It is suitably used for tubes and thin image forming apparatuses.
[0002]
[Prior art]
Research on cold cathodes, which emit cold electrons by applying a strong electric field instead of giving a large amount of thermal energy to emit hot electrons like a cathode ray tube, has been actively conducted in the field of device structure and materials. Researched and developed.
[0003]
In recent years, carbon nanotubes (CNT) having a nested shape of a graphite layer wound in a cylindrical shape have been discovered by Iijima et al. Similarly, application of carbon materials to electronic devices is expected.
[0004]
For example, as an electronic device using CNT, which is one of carbon materials, as disclosed in Japanese Patent Application Laid-Open No. 10-12124, CVD is performed in pores of an oxide film formed by anodizing an aluminum substrate. There is a field emission electron source having a triode structure (FIG. 6) in which CNTs are selectively grown by a method.
[0005]
Here, the electron-emitting device of FIG. 6 will be described below. The electron source is composed of the carbon nanotubes 2, and the carbon nanotubes 2 are formed using the catalyst 5 provided in the pores of the anodic oxide film arranged regularly. The electron source is separated by a gap 6 and is electrically connected to the cathode electrode (aluminum) 3. The electron-emitting device is configured such that an extraction electrode 1 for extracting electrons from the carbon nanotube 2 is provided on the surface of the anodic oxide film, and an anode electrode 4 is provided so as to face the carbon nanotube 2. Such an electron-emitting device makes it possible to improve the temporal stability of the intensity of the emission current.
[0006]
[Problems to be solved by the invention]
However, in the electron source having a triode configuration disclosed in Japanese Patent Application Laid-Open No. 10-12124, the cathode electrode (aluminum) and the extraction electrode are configured in parallel, so that the electron source cannot be addressed by the XY matrix. There was a problem. Further, in the manufacturing method, there is a problem that aluminum is easily damaged by a thermal process (CVD process) in the manufacturing process, so that the reliability of the device is greatly deteriorated. Furthermore, since the electron source is formed by depositing, patterning, or the like of aluminum, there is a problem that the cost is high.
[0007]
Therefore, the present invention has been made to solve the above problems, and has as its object to provide a highly reliable XY matrix-capable electron source and to manufacture such an electron source at low cost. I do.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a cold cathode according to the present invention includes an electron source, a cathode electrode electrically connected to the electron source, a gate electrode, and electrically insulating the electron source from the gate electrode. A gate insulating layer, the gate insulating layer including a first gate insulating layer and a second gate insulating layer, wherein the second gate insulating layer includes a cathode electrode. Forming an insulating layer between the first gate insulating layer and the gate electrode , wherein the first gate insulating layer is formed in the opening and has a mold structure in which the electron source is formed. And Thus, opening the first gate insulating layer, wherein the second gate insulating layer by providing the gap opening, the opening (electron emitting area) of any size, dividable into shape I do.
[0009]
Preferably, the cathode electrode and the gate electrode are orthogonal to each other, and the opening is provided in a region orthogonal to the cathode electrode . Is characterized in that the gate insulating layer has pores, and the pores of the gate insulating layer are molds for controlling the shape of the electron source. With such a template structure, the electron source density and the diameter of the electron emission region can be precisely controlled. More preferably, by configuring the electron source formed in the template structure with carbon nanotubes, it is possible to provide a cold cathode having an electron source that can be driven at a low voltage and has excellent ion impact resistance.
[0010]
Further, the invention is characterized in that the first gate insulating layer is constituted by pores formed by anodizing aluminum and an alumina thin film. With this configuration, it is possible to form a template structure having pores whose arrangement is controlled with high precision.
[0011]
In the cold cathode according to the present invention, a high-resistance layer is provided between an electron source and a cathode electrode, and the electron sources are connected in parallel (in an equivalent circuit) to the high-resistance layer. The sources are electrically isolated from each other. With this configuration, individual electron sources can be connected in parallel to the high-resistance layer, and a highly reliable current limiting mechanism can be provided.
[0012]
In the method for manufacturing a cold cathode according to the present invention, a first step of forming a cathode electrode on a supporting substrate, a second step of forming a high-resistance layer on the cathode electrode, and a first step of forming a first layer on the high-resistance layer A third step of forming a gate insulating layer and forming pores in the first gate insulating layer; and a fourth step of forming an electron source in the pores so as to be electrically connected to the cathode electrode . A step, a fifth step of forming a second gate insulating layer on the high-resistance layer other than a region where the first gate insulating layer is formed, and forming a gate electrode on the second gate insulating layer And a sixth step. By adopting such a manufacturing method, a vacuum device and photolithography can be dispensed with, and the cost of manufacturing a cold cathode can be reduced.
[0013]
More preferably, the third step includes a step of bonding an aluminum thin film to the high-resistance layer , and a step of anodizing the aluminum thin film. By adopting such a manufacturing method, it is possible to further reduce the cost of manufacturing a cold cathode with a template structure having finely controlled pores.
[0014]
Also, preferably, the third step is an aluminum plate, or a step of anodizing the aluminum thin film, a step of removing the anodized film from the aluminum plate or aluminum thin film was the anodizing, the anodized film And a step of bonding to the high resistance layer . By adopting such a manufacturing method, it is possible to further reduce the cost of manufacturing the cold cathode.
[0015]
In addition, the electron source is formed by a gas phase carbonization method using a metal catalyst or a gas phase carbonization method using plasma, thereby lowering the temperature of the cold cathode manufacturing process and forming the first gate insulating layer. Thermal distortion can be reduced.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a device using a cold cathode according to the present embodiment. Here, a field emission display (FED) will be described as a representative example.
[0017]
A cathode electrode wiring 2 is formed on an insulating support substrate 1. As the support substrate 1, a ceramic substrate, a glass substrate, or the like can be used. As the cathode electrode wiring 2, a metal material conventionally used in FEDs can be used. The high-resistance layer 3 is provided so as to cover the cathode electrode wiring 2, and the current limit is applied to the electron source 7. Such a current limiting mechanism improves the reliability of the electron source 7, and in the case of the cold cathode of the present embodiment, has a structure in which a resistance component is added independently in parallel with the electron source 7. In addition, the reliability of the cold cathode is greatly improved.
[0018]
The density and diameter of the electron source 7 are precisely controlled by the first gate insulating layer 5. The pores formed in the first gate insulating layer 5 have a diameter of about 10 to 30 nm and a density of about 10 ¹⁰ / cm ² , which can be precisely controlled. It has an optimal structure as a mold. That is, in the present invention, the first gate insulating layer 5 is provided with pores having an optimal shape for the electron source 7, and the pores are used as a template for the electron source 7 to control the shape of the electron source 7. .
[0019]
In the present invention, the first gate insulating layer 5 serving as the electron emitting region and the second gate insulating layer 8 provided outside the electron emitting region are provided, and conventionally existed as a single gate insulating layer. The gate insulating layer is divided and configured. With this configuration, it is possible to form a template structure limited to the electron emission region, and to prevent formation of an electron source in a region other than the electron emission region. That is, patterning of the electron emission region is enabled. Then, by forming the electron source 7 using the template structure, the electron source density and diameter can be precisely controlled.
[0020]
As the electron source 7, any material may be used as long as it is an electron-emitting material that can be filled in the template structure. However, a carbon material such as a carbon nanotube is preferable in terms of low-voltage driving and ion impact resistance. As the carbon material that can be formed in the mold, diamond, graphite, diamond-like carbon, or the like can be used.
[0021]
Further, as the first gate insulating layer 5 used as the mold structure, alumina formed by anodizing aluminum is preferable. If the purity of such aluminum is 99% or more, it can be easily anodized, and the diameter of pores formed in the anodized film can be controlled to 10 nm or less.
[0022]
The gate electrode wiring 9 is electrically insulated by the cathode electrode wiring 2 and the second gate insulating layer 8, and the gate electrode wiring 9 and the cathode electrode wiring 2 are orthogonal to each other.
[0023]
The pixel 10 serving as an electron emission region is disposed in a region where the cathode electrode wiring 2 and the gate electrode wiring 9 are orthogonal to each other, and is XY-addressed by the driver IC. An anode (transparent) electrode 11 and a phosphor 12 are provided on an anode electrode-side support substrate provided so as to face a cathode electrode-side support substrate provided with a cold cathode. The electron source 7 in the pixel addressed by the cathode electrode wiring 2 and the gate electrode wiring 9 emits electric field in a vacuum, collides with the phosphor 12 on the opposing anode electrode 11, and emits light.
[0024]
For example, when the electron source 7 was formed of carbon nanotubes, an emission having an electric field strength of 10 V / μm and a current density of 10 mA / cm ² was obtained. The light emission luminance was about 500 cd / m ² , which was sufficient for use in an image forming apparatus.
[0025]
Next, a method of manufacturing the cold cathode used in the present embodiment will be described with reference to FIGS. First, as shown in FIG. 2A, a cathode electrode wiring 2 is formed on a support substrate 1, and a high resistance layer 3 is formed on the cathode electrode wiring 2.
[0026]
After that, the first gate insulating layer 5 is formed in the electron emission region on the high resistance layer 3 or, in the case of the image forming apparatus, in the region of the pixel 10, and a large number of pores 6 are provided on the layer. FIGS. 4A and 4B are cross-sectional views illustrating the method in detail. Here, the large number of pores 6 will be described. As an insulating layer having pores, an alumina anodic oxide film obtained by anodizing an aluminum thin film is preferable in consideration of the fact that fine processing is unnecessary, and the diameter of the pores 6 is preferably controlled to 10 nm or less. It is possible.
[0027]
Therefore, FIG. 4A shows a manufacturing method of directly bonding the aluminum anodic oxide film 5 on the high resistance layer 3 by an electrostatic bonding method or the like as a method of manufacturing the alumina anodic oxide film. This anodic oxide film 5 is formed by forming an anodized film 5 by anodizing an aluminum substrate provided separately from the material itself forming the cold cathode, and peeling the anodic oxide film 5 from the aluminum substrate. Is obtained.
[0028]
On the other hand, FIG. 4B shows that the aluminum thin film 4 is formed directly on the high resistance layer 3 (see FIG. 2B), and the aluminum thin film 4 is anodized to form an anodic oxidation on the high resistance layer 3. The manufacturing method for forming the film 5 (see FIG. 2C) is shown. At this time, the aluminum thin film is formed by depositing the aluminum thin film using a vapor deposition method or the like, by combining photolithography and patterning using etching, or by bonding the aluminum foil to the high resistance layer 3 by electrostatic bonding. A method such as bonding directly on the top is preferable.
[0029]
However, as shown in FIG. 4B, pores 6 are formed in the anodic oxide film 5 formed by anodic oxidation of aluminum, and the bottom of the pores 6 is usually provided at the interface with the high-resistance layer 3. A barrier layer made of anhydrous alumina is formed. In the present embodiment, the barrier layer at the bottom of the pores 6 is removed by wet-etching this barrier layer with a phosphoric acid-based mixed acid. This is for electrical connection with the cathode electrode, and unless the barrier layer is removed, a voltage cannot be applied to the electron source and a problem such as floating is likely to occur.
[0030]
However, it is also possible to select a structure in which the barrier layer is positively left depending on the purpose. That is, by leaving the barrier layer, a resistance component is provided, and by providing a role as a resistance layer, a structure in which the formation of the resistance layer is unnecessary can be provided. In this case, it is necessary to design the resistance value of the resistance layer and control the thickness of the barrier layer that fits the design.
[0031]
In the structure in which the barrier layer is removed, an increase in the diameter of the pores 7 may occur when wet etching is performed to remove the barrier layer. This is because the material of the barrier layer and the material of the anodic oxide film constituting the pores are basically the same as alumina. Therefore, there is no etching selectivity between the barrier layer and the anodic oxide film (almost 1), and the pores are etched by the thickness of the barrier layer, the pore diameter is enlarged, the electric field concentration is reduced, and the emission characteristics are reduced. There is a high possibility that the problem of deterioration will occur.
[0032]
Therefore, by inserting titanium (Ti) between the high resistance layer 3 and the aluminum thin film 4, the barrier layer at the bottom of the pores 6 can be made conductive. The conductive path, which is considered to be the diffusion of titanium into the barrier layer, can be formed by continuing the anodic oxidation after the completion of the anodic oxidation of aluminum. FIG. 5B is a structural diagram of a cold cathode in which titanium is inserted. As a reference drawing, FIG. 5A shows a structural diagram of a cold cathode in which titanium is not inserted.
[0033]
4A or 4B, the aluminum 4 or the anodic oxide film 5 in the pixel 10 region is bonded on the high-resistance layer 3 as indicated by an arrow 13, and the cold cathode manufacturing cost is reduced. Enables a significant reduction in In other words, by adopting a manufacturing method of bonding an aluminum foil and an anodized film, a thin film forming process using a vacuum apparatus such as evaporation and sputtering, which has been conventionally used, becomes unnecessary, and a photolithographic process for patterning and etching. There is no need for a process (that is, the number of masks is reduced by one), the manufacturing process is simplified, and an expensive manufacturing apparatus is no longer required, resulting in cost merit.
[0034]
Next, an electron source 7 is formed in the pores 6 of the anodic oxide film 5. As the electron source 7, a carbon nanotube is preferable in terms of low voltage driving and ion impact resistance. The carbon nanotube electron source 7 is formed by a CVD method. The technique of forming carbon nanotubes in the pores of such an anodized film is disclosed in JP-A-10-12124 by electrochemically depositing a catalyst in the pores of the anodized film. This is made possible by growing carbon nanotubes depending on the deposited catalyst.
[0035]
In the present embodiment, carbon nanotubes are formed by a CVD method using a unique reaction field on the inner wall of the pores 7 without using a metal catalyst. That is, in the formation of carbon nanotubes depending on the inner wall of the pore, the reaction gas used in the CVD method penetrates the pore and deposits on the inner wall of the pore to form a tube. Although the tube formed in this manner has lower crystallinity than the tube formed using a catalyst, the tube end is open and has a preferable shape as an electron source. The process temperature of such a CVD method becomes possible at about 800 ° C., and when the plasma assisted CVD method is used, it becomes possible at about 600 ° C.
[0036]
In any case of the CVD method, the melting point temperature of each of the supporting substrate 1, the cathode electrode wiring 2, the high resistance layer 3, and the first gate insulating layer (anodic oxide film) 5 constituting the cold cathode is determined by the CVD method. Materials above the process temperature should be selected accordingly.
[0037]
Further, the electron source 7 preferably has a structure protruding from the first gate insulating layer 5 as shown in FIG. According to theoretical calculations, by projecting a length equal to or longer than the pitch of the electron source 7 from the first gate insulating layer 5, the electric field concentration of the electron source 7 is increased, and the emission characteristics are improved. Make it possible.
[0038]
Finally, the second gate insulating layer 8 is formed at least in a region where the gate electrode wiring 9 is provided. The second gate insulating layer 8 electrically insulates the high resistance layer 3 on the cathode electrode wiring 2 from the gate electrode wiring 9. The gate insulating layer can be formed in a line with respect to the cathode electrode or by a method of forming an opening after forming the entire surface of the device.
[0039]
The former linear gate insulating layer can be formed by using a rib forming process used in a plasma display panel (PDP). In the well-known PDP rib formation, a frit glass-based paste material is printed four to six times using a screen printing method and dried. By the lamination printing of such a paste, a linear wall having a height of 100 μm or more can be formed. In the present embodiment, such a linear wall is used as a gate insulating layer. The gate electrode is formed by laminating and printing a gate electrode material on the top of the linear wall.
[0040]
On the other hand, the latter gate insulating layer having an opening can be formed by forming the gate insulating layer over the entire surface of the device and then patterning the opening (electron emission region). However, when forming a gate electrode, it is preferable to perform patterning for forming an opening after depositing a gate insulating layer and a gate electrode, respectively. In such patterning, for example, after forming a resist mask having an opening in a window, the gate electrode is removed, and the gate insulating layer is further removed.
[0041]
Here, according to the manufacturing method, in the cold cathode structure, the first gate insulating film undergoes a heat treatment at about 800 ° C., and undergoes a phase transition to γ-alumina (having a phase transition temperature of about 500 to 600 ° C.) It is difficult to be etched by hydrofluoric acid or the like. Therefore, for example, when a glass-based insulating material is used for the second gate insulating layer, the gate electrode material is etched using a photoresist having a gate opening, and the second gate insulating layer is etched with hydrofluoric acid. In this case, the etching selectivity with respect to the underlying first gate insulating layer can be increased.
[0042]
The former is a manufacturing method advantageous for large-area devices, while the latter is an advantageous manufacturing method for high-definition devices. The selection of these manufacturing methods should be appropriately selected by those skilled in the art. In either manufacturing method, a triode structure having a gate electrode wiring and a gate insulating layer as shown in FIG. 2B is formed. A cold cathode can be manufactured.
[0043]
As described above, according to the cold cathode manufacturing method shown in FIGS. 2 and 3, an emission current of 10 mA / cm ^{2 and} an electric field strength of 10 V / μm can be obtained. Further, an image forming apparatus having a light emission luminance of about 500 cd / m ² can be obtained.
[0044]
【The invention's effect】
The cold cathode of the present invention is XY-addressable, so that the degree of freedom of pixel division can be improved and the emission current can be improved. Further, by connecting an electron source in parallel with the high resistance layer, the reliability of the cold cathode can be improved.
[0045]
In addition, by forming the electron source formed in the mold structure having pores in the gate insulating layer with carbon nanotubes, it is possible to provide an electron source that can be driven at a low voltage and has excellent ion impact resistance, By constituting the layer with alumina, it is possible to provide a template structure having pores whose arrangement is controlled with high precision.
[0046]
On the other hand, the method for manufacturing a cold cathode according to the present invention makes it possible to reduce the cost and to provide a mold structure having excellent controllability by a simple manufacturing method. Further, by forming an electron source by a gas phase carbonization method using a metal catalyst or a gas phase carbonization method using plasma, it is possible to provide a method for manufacturing a cold cathode with reduced process damage.
[Brief description of the drawings]
FIG. 1 is a perspective view of a thin image forming apparatus using a cold cathode according to the present invention.
FIG. 2 is a process sectional view illustrating a method for manufacturing a cold cathode according to the present invention.
FIG. 3 is a process cross-sectional view illustrating a method for manufacturing a cold cathode of the present invention.
FIG. 4 is a perspective view of a cold cathode using the bonding technique of the present invention.
FIG. 5 is a structural sectional view of a cold cathode of the present invention.
FIG. 6 is a structural sectional view of a conventional cold cathode.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cathode-side support substrate 2 Cathode electrode wiring 3 High resistance layer 4 Metal thin film forming electron emission region 5 Metal anodic oxide film forming electron emission region (first gate insulating layer)
6 pores of metal anodic oxide film 7 electron source 8 second gate insulating layer 9 gate electrode wiring 10 electron emission region (pixel)
11 Anode electrode 12 Phosphor 13 Bonding direction

Claims (8)

An electron source, a cathode electrode electrically connected to the electron source, a gate electrode, and a cold cathode including a gate insulating layer for electrically insulating the electron source and the gate electrode;
The gate insulating layer includes a first gate insulating layer and a second gate insulating layer;
The second gate insulating layer, with an insulating layer between the cathode electrode and the gate electrode has an opening,
The cold cathode, wherein the first gate insulating layer is formed in the opening and has a template structure in which the electron source is formed . 2. The cold cathode according to claim 1, wherein the cathode electrode and the gate electrode are orthogonal to each other, and the opening is provided in a region orthogonal to the cathode electrode. 3. 2. The cold cathode according to claim 1, wherein the first gate insulating layer has pores, and the pores of the gate insulating layer are molds for controlling the shape of the electron source. 2. The cold cathode according to claim 1, wherein said first gate insulating layer is composed of pores formed by anodizing aluminum and an alumina thin film. A high resistance layer is disposed between the electron source and the cathode electrode, and the electron sources are connected in parallel with the high resistance layer, and the electron sources are electrically insulated from each other. claims 1 to 4 cold cathode according. A first step of forming a cathode electrode on a support substrate;
A second step of forming a high resistance layer on the cathode electrode;
A third step of forming a first gate insulating layer on the high resistance layer and providing pores in the first gate insulating layer ;
A fourth step of forming an electron source in the pores so as to be electrically connected to the cathode electrode ;
A fifth step of forming a second gate insulating layer on the high resistance layer other than the region where the first gate insulating layer is formed;
And a sixth step of forming a gate electrode on the second gate insulating layer. The method according to claim 6, wherein the third step includes a step of bonding an aluminum thin film to the high resistance layer and a step of anodizing the aluminum thin film. The third step is a step of anodizing an aluminum plate or an aluminum thin film, a step of removing an anodized film from the anodized aluminum plate or the aluminum thin film, and a step of attaching the anodized film to the high-resistance layer. 7. The method for producing a cold cathode according to claim 6 , comprising a step of combining.

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