JP3558948B2 - Electron source array and method of manufacturing the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electron source array having a low starting voltage and a low driving voltage and a method of manufacturing the same, and is used for an ultra-low power consumption and ultra-high brightness field emission display.
[0002]
[Prior art]
Research on electron sources that emit a field by applying a strong electric field instead of giving a large amount of thermal energy and emitting thermionic electrons like a cathode ray tube has been actively conducted on both the device side and the material side. .
[0003]
Conventional electron sources include C.I. A. A pyramid-shaped metal electron source as disclosed by Spindt et al. (US Pat. No. 3,665,241) is known, and a metal material having a high melting point, such as molybdenum, is used for such a metal electron source. . However, the Spindt-type metal electron source using such a high melting point metal material has a problem that the operating vacuum degree is as high as 10 ⁻⁹ Torr and the ion impact resistance is weak, so that the reliability is low.
[0004]
In recent years, carbon nanotubes (hereinafter abbreviated as CNT) have been discovered by Iijima et al. (S. Iijima, Nature, 354, 56 (1991)) as a by-product of fullerene synthesis by carbon arc discharge. The CNT has a nested structure of a graphite layer wound in a cylindrical shape. A. (WA de Heer, Science, 270, 1179 (1995)), and an emission current of 10 mA / cm ² (voltage: 25 V / μm) has been observed.
[0005]
M. Moskovits et al. (PCT Publication No. WO 99/25652) discloses an electron source structure as shown in FIG. CNTs are formed by anodizing an aluminum substrate, electrodepositing a metal catalyst such as cobalt, iron, or nickel on the pores of the anodic oxide film and carbonizing the gas phase. The CNT electron source is formed by partially removing the anodic oxide film by etching and exposing the CNT to the receded flat anodic oxide film surface.
[0006]
[Problems to be solved by the invention]
However, although the device driving voltage of the conventional CNT electron source is lower than that of the Spindt-type metal electron source, it is about several tens of V / μm, and it is not sufficiently reduced in terms of the withstand voltage of the driving driver. Met. Also, W.S. A. The CNT electron source of De Heer et al. is a CNT formed by arc discharge, and it has been difficult to perform both patterning and orientation control.
[0007]
Further, the CNT electron source disclosed in PCT Publication No. WO99 / 25652 is a CNT formed by a gas phase carbonization method (CVD method), and is used for a catalyst disposition process (electrodeposition) and for improving field emission characteristics. There is a problem that the CNT tip opening process (furnace annealing) is required, and the manufacturing process becomes complicated.
[0008]
The present invention has been made to solve the above-mentioned conventional problems, and provides a structure capable of reducing the emission start voltage of the electron source array and the device driving voltage, and simplifies the manufacturing process of the electron source array. The purpose is to do.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an electron source array according to the present invention comprises a filament-shaped electron source and fine particles provided in a gap between the electron sources, and a structure in which fine particles are provided and fixed in a gap between the electron sources. Thereby, an array in which the electron sources are controlled to be highly oriented is formed, and an electron source array that emits a large current at a low driving voltage is realized.
[0010]
Preferably, the fine particles provided in the gap between the electron sources are made of alumina, so that an electron source array in which electron sources having a small diameter are highly integrated is formed. Implement a source array.
[0011]
Furthermore, by constructing the electron source with carbon nanotubes, an electron source array with excellent ion bombardment resistance and operable at a low vacuum degree is formed, and the reliability of the electron source array that emits a large current at a low driving voltage is improved. Realize.
[0012]
In the method for manufacturing an electron source array according to the present invention, a step of forming a mold of an electron source having a filament shape, a step of filling the mold with an electron source material to form a filament-shaped electron source, and heating the mold The bulk and the etching rate are different from each other in the mold to form phase-transferred fine particles, and the template is removed by etching so that only the fine particles remain, so that the fine particles are interspersed in the gap between the electron sources. The step of fixing the electron source with fine particles makes it possible to easily manufacture an electron source array that emits a large current at a low driving voltage.
Furthermore, by constructing the electron source with carbon nanotubes, an electron source array with excellent ion bombardment resistance and operable at a low vacuum degree is formed, and the reliability of the electron source array that emits a large current at a low driving voltage is improved. Realize.
[0013]
In addition, since the step of forming the mold includes the anodizing step, a fine processing step for manufacturing a semiconductor device is not required, and the electron source array is manufactured at low cost. Furthermore, since the step of forming the electron source in the mold includes a gas-phase carbonization step, the step of disposing a metal catalyst becomes unnecessary, and the electron source array is manufactured in a simplified step.
In addition, preferably, in an anodizing step, an electron source array in which an electron source having a small diameter is highly integrated by anodizing aluminum to form an electron source array that emits a large current at a low driving voltage. Arrays can be manufactured.
[0014]
Further, preferably, the step of fixing the electron source with the fine particles includes an oxygen plasma etching step and an alkaline wet etching step, thereby providing a manufacturing method in which the fine particles can be easily arranged in the gap between the electron sources.
[0015]
Furthermore, preferably, the alkali wet etching step includes a step of ending the point at which the weight ratio of the weight of the first material forming the electron source to the weight of the material forming the mold becomes constant, An electron source array structure having optimized emission characteristics can be manufactured.
Further, it is preferable that the heating in the step of fixing the electron source with the fine particles is performed by a gas phase carbonization step.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
<First embodiment>
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 the electron source array according to the present embodiment. Here, the device to be described has a triode structure. Available for display (FED).
[0017]
As shown in FIG. 1, a cathode electrode 2 is formed on a support substrate 1 made of glass, ceramic, or the like. For the cathode electrode 2, a conventionally used cathode electrode material can be used. An adhesive layer 3 is formed on the cathode electrode 2, and an electron source array formed from an electron source 4 and fine particles 5 is provided on the adhesive layer 3. A resistance layer used in a conventional electron source array may be inserted on the cathode electrode 2. In the case of the electron source array of the present embodiment, the adhesive layer 3 may have a desired resistance value and may be used as a resistance layer.
[0018]
The fine particles 5 provided in the gap between the electron source arrays 4 are preferably an insulating material because the individual electron sources 4 can be electrically insulated and reliability can be improved. Further, such fine particles 5 are preferably fine in that the electron source array 4 can be highly integrated, and the fine particles 5 having a size of about several tens nm are used.
[0019]
The electron source array composed of the electron source 4 and the fine particles 5 surrounds each electron emission region (pixel in the case of FED) with a gate insulating layer 6, and further has a gate electrode 7 on the gate insulating layer 6. Is provided. Gate electrode 7 is provided to be orthogonal to cathode electrode 2. This is a structure for XY addressing the electron emission region (pixel). The gate insulating layer 6 needs to have a film thickness that completely insulates the gate electrode 7 from the cathode electrode 2. A film thickness corresponding to a distance at which emission can be controlled is required.
[0020]
The electron source 4 of the present embodiment is preferably made of a carbon material in terms of emission characteristics (operation drive voltage, operation vacuum degree, etc.). As the electron source material other than the carbon material, a high melting point metal material such as molybdenum can be used. Such a high melting point metal material can be manufactured relatively easily by using an anodic oxide film and electroplating of the metal material described later, and has excellent emission characteristics. As the electron source of the present embodiment, not only carbon nanotubes but also carbon materials such as diamond, diamond-like carbon, graphite, and amorphous carbon can be used. The shape of the electron source 4 can be freely changed by designing a mold described later. The shape of the electron source 4 of the present embodiment has a diameter of about 30 nm and a length of about 75 μm.
[0021]
The shape of the electron source 4 of the present embodiment can be freely changed by designing a mold. It is preferable that such a mold not only determines the shape of the electron source 4 but also contains a material constituting the fine particles 5. As such a mold material, an alumina anodic oxide film obtained by anodizing aluminum is preferable. Alumina anodic oxidation exists such that linear pores of about several nm to several tens nm penetrate both surfaces. The density of the pores is about 10 ¹⁰ / cm ² .
[0022]
Further, by passing through a heating step of about 500 to 800 ° C., the phase-transformed fine particles 5 are formed. Such phase-transformed fine particles 5 have different etching characteristics from alumina forming the bulk. That is, the alumina forming the fine particles 5 and the bulk alumina can secure an etching selectivity with respect to an alkali etchant such as sodium hydroxide, leaving only the fine particles 5 after the etching, as shown in FIG. It is possible to form an electron source array.
[0023]
FIG. 2 is an SEM (electron microscope) photograph of the electron source array of the present embodiment. It can be confirmed that the electron sources 4 made of carbon nanotubes having a diameter of about 30 nm are integrated at a high density and with high orientation control, and fine particles 5 are scattered in the gaps between the carbon nanotubes.
[0024]
The emission characteristics of the carbon nanotube electron source of the present embodiment were experimentally confirmed. FIG. 3 shows the IV characteristics of the carbon nanotube electron source of the present embodiment. Each plot in the figure shows a change in emission characteristics when the alkali treatment time described later is changed. The cause of such a change in the emission characteristics will be described later in detail. According to the IV characteristics of FIG. 3, the carbon nanotube electron source of the present embodiment starts to emit from about 0.3 to 0.5 V / μm, which is about 1/200 of the conventional metal electron source, and This is about 1/20 of that of the conventional carbon nanotube electron source, and the emission start voltage is significantly reduced.
[0025]
Furthermore, using the electron source array of the present embodiment, a phosphor was provided on the opposed anode electrode, and the phosphor was allowed to emit light. As a result, a light emission luminance of 10,000 cd / m ² or more was obtained. A prototype of a 5-inch diagonal, 320 × 240 (QVGA) panel was prototyped, and when a video signal was input, an image could be displayed.
[0026]
Next, a method for manufacturing the carbon nanotube (CNT) of the present embodiment will be described with reference to FIGS. 4 and 5 are process cross-sectional views showing a method for manufacturing a CNT electron source having a diode structure according to the present embodiment. FIG. 6 is an end time of alkaline wet etching of the present embodiment. FIGS. 5 is a SEM photograph of an electron source array after alkaline etching of a form. In the present embodiment, porous alumina is used as a mold for forming CNTs, but porous tantalum oxide, porous silicon, or the like may be used. The electron source array of the present embodiment describes a typical configuration of an electron source array, and uses carbon nanotubes as an electron source 4 and an alumina anodic oxide film as a template.
[0027]
FIG. 4A is a sectional view showing a process in which an aluminum substrate 8 is anodized to form an anodic oxide film 9 and linear pores 10. The anodic oxidation of the aluminum substrate 8 was performed for 2 hours in a sulfuric acid solution at 0 ° C. by applying a voltage of 20V. FIG. 4B is a cross-sectional view showing a process in which the anodic oxide film 9 is separated from the aluminum substrate 8, gas phase carbonized, and carbon nanotubes are formed in the pores 10. When a reverse voltage is applied to the aluminum substrate 8 with the anodic oxide film 9 formed in FIG. 4A in a sulfuric acid solution for 10 minutes, the anodic oxide film 9 peels off. The anodic oxide film 9 thus formed had pores 10 with pore diameters of about 30 nm and a film thickness of about 75 μm. The anodic oxide film 9 having such pores 10 is carbonized in a gas phase, and the pores 10 are filled with the carbon nanotubes 4. The carbon nanotubes 4 are obtained by flowing propylene (2.5% in nitrogen) through a quartz tube at 800 ° C. for 3 hours. At this time, the amorphous carbon 11 is simultaneously deposited on the surface of the anodic oxide film 9.
[0028]
FIG. 4C is a sectional view showing a step in which the amorphous carbon 11 deposited on the surface of the anodic oxide film 9 is removed. The removal of the amorphous carbon 11 was performed by oxygen plasma etching using RIE (reactive ion etching). Wet etching is not preferable in terms of the selectivity of the carbon nanotubes 4. In addition, plasma etching using an inert gas such as argon has a small effect on oxygen plasma etching.
[0029]
FIG. 5A is a process sectional view in which the fine particles 12 are formed by etching the anodic oxide film 9. A part of the anodic oxide film 9 undergoes a phase transition by a heating step (800 ° C.) when forming the carbon nanotube in FIG. 4B. Due to such a phase transition, the phase-transformed fine particles 12 are considered to exist in the bulk of the anodic oxide film 9 in a polycrystalline state. The fine particles 12 formed by the phase transition have different physical properties from the bulk of the anodic oxide film 9, and as a result, the etching rate is different. For example, in the present embodiment, when etching was performed with sodium hydroxide at 150 ° C., the bulk anodic oxide film 9 was removed by etching, and only the fine particles 12 remained. Of course, the carbon nanotubes 4 are not removed at all by etching.
[0030]
FIG. 6 is a diagram showing the weight ratio of sodium hydroxide to the etching time. Here, the weight ratio indicates the ratio of the weight of the carbon nanotube 4 to the total weight of the carbon nanotube 4 and the anodic oxide film 9. It can be seen that the weight ratio decreases and the bulk anodic oxide film 9 serving as a mold is etched away until the alkali treatment time is 2 hours. When the alkali treatment time exceeds 2 hours, the weight becomes constant. In such a state where the weight ratio is constant, the removal of the bulk anodic oxide film is completed, and only the carbon nanotubes 4 and the fine particles 12 which are not removed by etching are present.
[0031]
7 to 10 show SEM photographs in which the anodic oxide film 9 was observed from the upper surface when the alkali treatment time was 0.5 hour, 1 hour, 2 hours, and 3 hours. When the alkali treatment time is 0.5 hour, the anodic oxide film 9 is hardly removed by etching, and when the treatment is performed for 1 hour, a part of the carbon nanotubes 4 starts to be exposed. It can be seen that is exposed. In addition, when the alkali treatment was compared with 2 hours and 3 hours, the orientation of the carbon nanotubes 4 treated for 3 hours was disordered with respect to 2 hours. This supported the results of the emission characteristics of FIG. From the above, it was found that the alkali treatment time was most preferably 2 hours. This result varies depending on the film thickness of the anodic oxide film 9, the temperature of the gas phase carbonization, and the like, as shown in FIG. After confirming the etching characteristics experimentally, the manufacturing conditions of the electron source array should be set. Such a state indicates a characteristic structure of the electron source array of the present invention, as can be seen from the SEM photograph of FIG.
[0032]
FIG. 5B is a process sectional view in which an electron source array including the carbon nanotube electron sources 4 and the fine particles 12 is fixed to the cathode electrode 2 on the support substrate 1 via the adhesive layer 3. It is preferable that the adhesive layer 3 is bonded with a conductive paste such as a silver paste or a carbon paste. Further, a low melting point metal material may be used as the adhesive layer 3.
[0033]
<Second embodiment>
In this embodiment, a manufacturing method different from that of the first embodiment is shown. Specifically, an aluminum film is formed on a cathode electrode, and this is anodized to form a mold. This will be described with reference to FIGS. Although the electron source array of the present embodiment has a three-electrode structure, the electron source array manufactured in the first embodiment may be capable of forming a triode structure as in the present embodiment. .
[0034]
FIG. 11A is a process sectional view in which an aluminum film on the adhesive layer 3 of the structure of the adhesive layer 3 / cathode electrode 2 / support substrate 1 is anodized. The aluminum film on the adhesive layer 3 is formed by bonding aluminum foil with a conductive paste or a low-melting metal. Alternatively, the adhesive layer 3 may be used as a resistance layer, and an aluminum deposit may be formed by a sputtering method, an evaporation method, or the like. When the aluminum film formed on the adhesive layer 3 is anodized, pores 10 are formed in the anodic oxide film 9 as in the first embodiment.
[0035]
FIG. 11B is a process sectional view in which the carbon nanotubes 4 are formed in the pores 10 of the anodic oxide film 9. Amorphous carbon 11 is deposited on the surface of the anodic oxide film 9 simultaneously with the formation of the carbon nanotubes 4. The carbon nanotubes 4 were formed using a gas phase carbonization method. The conditions for gas-phase carbonization of the pores 10 of the anodic oxide film 9 are the same as those in FIG. FIG. 11C is a process sectional view in which the amorphous carbon 11 on the anodic oxide film 9 has been removed. As in FIG. 4C of the first embodiment, the amorphous carbon 11 is removed by oxygen plasma etching using RIE.
[0036]
FIG. 12A exposes fine particles 12 scattered in the anodic oxide film 9. In this case, unlike the first embodiment, a glass substrate is not preferable as the support substrate 1. However, if the etchant is changed to a mixed acid of phosphoric acid / hydrochloric acid, a glass substrate can be used. FIG. 12B is a process sectional view in which the gate insulating layer 13 and the gate electrode 14 are formed. Such a method for manufacturing an electron source array having a triode structure can be applied to the electron source array formed in the first embodiment. The gate insulating layer 13 is formed by multi-layer printing of a frit glass-based paste by a screen printing method. The thickness is about 100 μm, and this thickness should be determined by device design. Next, a gate electrode 14 is formed on the gate insulating layer 13. The gate electrode 14 is formed by printing a metal wiring material generally used in a screen printing method, similarly to the formation of the gate insulating layer 13.
[0037]
When the electron source array of the present application is manufactured as described above, an electron source array that can be driven at a low voltage can be provided, and a high-intensity field emission display (FED) can be realized.
[0038]
【The invention's effect】
According to the electron source array of the present invention, it is possible to form an array in which the electron source is highly oriented and to control the electron source array in which the emission start voltage of the conventional electron source array using a high melting point metal is reduced to about 1/200. Can be provided.
[0039]
Also, by using alumina as the fine particles provided in the gap between the electron sources and carbon nanotubes as the electron source, an electron source array reduced to about 1/20 of the emission start voltage of the conventional electron source array using carbon nanotubes can be obtained. We have made it possible to realize ultra-bright field emission displays with ultra-low power consumption.
[0040]
By using the method of manufacturing an electron source array using a template as the method of manufacturing an electron source array of the present invention, the manufacturing method can be simplified, and the semiconductor device can be manufactured by forming the template by an anodizing method. By eliminating the need for such a fine processing step and filling the mold with an electron source using a gas-phase carbonization method, the step of disposing a metal catalyst is not required, and the manufacturing method is reduced in cost. Furthermore, the emission characteristics are optimized by performing the process of fixing the electron source with fine particles in the oxygen plasma etching process and the alkali wet etching process, and detecting the end point by the change in the weight of the mold containing the electron source in the alkali wet etching process. It is now possible to manufacture a simplified electron source array.
According to the electron source array according to such a manufacturing method, an array in which the electron source is highly oriented can be formed, and the electron source array in which the emission start voltage of a conventional electron source array using a high melting point metal is reduced to about 1/200. It is possible to provide a source array.
Further, the step of forming the template includes a step of anodizing aluminum, and by constituting the electron source with carbon nanotubes, the emission start voltage is reduced to about 1/20 of the emission start voltage of the conventional electron source array using carbon nanotubes. We have made it possible to provide a reduced array of electron sources, and have realized a field emission display with ultra-low power consumption and ultra-high brightness.
[Brief description of the drawings]
FIG. 1 is a perspective view of a triode device using an electron source array of the present invention.
FIG. 2 is an SEM photograph of the electron source array of the present invention.
FIG. 3 is an IV characteristic diagram of the electron source array of the present invention.
FIG. 4 is a cross-sectional view showing a manufacturing process of the electron source array having a diode structure according to the first embodiment.
FIG. 5 is a cross-sectional view illustrating a manufacturing process of the electron source array having a diode structure according to the first embodiment.
FIG. 6 is a diagram illustrating a relationship between alkali treatment time and a weight ratio of the electron source array according to the first embodiment.
FIG. 7 is a top SEM photograph of the electron source array of the first embodiment after being subjected to an alkali treatment for 0.5 hour.
FIG. 8 is a top SEM photograph of the electron source array according to the first embodiment after an alkali treatment for one hour.
FIG. 9 is a top SEM photograph of the electron source array of the first embodiment after being subjected to an alkali treatment for 2 hours.
FIG. 10 is a top SEM photograph of the electron source array according to the first embodiment after alkali treatment for 3 hours.
FIG. 11 is a cross-sectional view illustrating a manufacturing process of an electron source array having a triode structure according to the second embodiment.
FIG. 12 is a cross-sectional view illustrating a manufacturing process of an electron source array having a triode structure according to the second embodiment.
FIG. 13 is a perspective view of a conventional electron source array using carbon nanotubes.
[Explanation of symbols]
1 support substrate 2 cathode electrode (wiring)
3 adhesive layer (resistance layer)
4 Filament-shaped electron source (carbon nanotube)
5 Fine particles (phase-transformed alumina)
6 gate insulating layer 7 gate electrode (wiring)
8 Aluminum substrate 9 Mold (Alumina anodic oxide film)
Reference Signs List 10 pores 11 amorphous carbon 12 fine particles (phase-transformed alumina)
13 gate insulating layer 14 gate electrode (wiring)

Claims (8)

A step of forming a mold of an electron source having a filament shape, a step of filling the mold with an electron source material to form a filament-shaped electron source, and heating the mold to form a bulk and an etching rate different from each other in the mold. Forming phase-transferred fine particles, and removing the template by etching so that only the fine particles remain, so that the fine particles are scattered in the gap between the electron sources and the electron source is fixed with the fine particles. A method for manufacturing an electron source array, comprising: The method according to claim 1, wherein the electron source is formed of carbon nanotubes . 3. The method according to claim 1, wherein the step of forming the template includes an anodic oxidation step . The method according to any one of claims 1 to 3, wherein aluminum is anodized in the anodizing step . The method of manufacturing an electron source array according to any one of claims 1 to 4, wherein the step of forming an electron source in the template includes a gas phase carbonization step . 6. The method according to claim 1, wherein the step of fixing the electron source with fine particles includes an oxygen plasma etching step and an alkaline wet etching step . The alkali wet etching step includes a step of ending the point at which the weight ratio of the weight of the first material forming the electron source to the weight of the material forming the mold becomes constant. A method for manufacturing an electron source array according to claim 1 . 6. The method according to claim 5, wherein the heating in the fine particle forming step is performed by the gas phase carbonization step.

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