JPH0794084A - Method for manufacturing electron-emitting device - Google Patents

Abstract

(57) [Summary] [Object] To provide a method capable of easily manufacturing an electron-emitting device by omitting the step of mask alignment as much as possible. [Structure] An ITO layer 12, a tantalum layer 13b, a tantalum oxide layer 13a, and an aluminum cold cathode 17 are formed on a glass substrate 11, and a resist is applied to the entire surface of the substrate. When back exposure is performed from the back side of the substrate and development is performed, only the resist layer 18a near the opaque cold cathode 17 remains. After forming the insulating layer 19 and the gate electrode layer 20 on the entire surface of the substrate, the resist layer 18a is lifted off, and the insulating layer 19 and the gate electrode layer 20 on the resist layer 18a are removed together. An electron-emitting device in which the gate electrode layer 20 is arranged so as to surround the is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electron-emitting device, and more particularly to a method for manufacturing an electron-emitting device used for vacuum micro devices and the like.

[0002]

2. Description of the Related Art With the spread of semiconductor devices, the vacuum tube technology has been forgotten, but in the last few years, the vacuum tube technology has regained attention. This is the development of so-called vacuum micro devices. This vacuum micro device is one in which fine vacuum tubes are integrated on the same substrate by utilizing the semiconductor fine processing technology cultivated in many years of research on semiconductor devices. That is, this element is provided with a cold cathode, an extraction electrode, and an anode, and an electron is extracted from the cold cathode by the extraction electrode and is emitted to the anode. By controlling the voltage applied to the extraction electrode, the amount of electrons emitted from the cold cathode can be controlled.

In a semiconductor device, since electrons move in a solid, the operating speed is governed by the mobility of electrons in the solid. On the other hand, in the vacuum micro device, since electrons move in the vacuum, it can operate at a very high speed as compared with the semiconductor device, and has attracted attention as a charge transport medium utilizing the advantages of the vacuum. Further, along with the research on this vacuum micro device, a cold cathode has been developed and is expected to be applied to a flat display and the like.

[0004]

A general electronic device is manufactured by a photolithography process using a large number of masks. Therefore, the electron-emitting device used for the vacuum micro device as described above is generally manufactured through a photolithography process. However, although the vacuum micro device is the same in principle as a vacuum tube, its size is so minute that it is incomparable to a vacuum tube. Therefore, it is necessary to perform mask alignment with high accuracy in the case of performing the photolithography process, and a high technology is required for its manufacture, which causes a problem of high cost.

Therefore, an object of the present invention is to provide a method capable of easily manufacturing an electron-emitting device by omitting the step of mask alignment as much as possible.

[0006]

[Means for Solving the Problems]

(1) The first invention of the present application comprises a cold cathode and an extraction electrode,
In a method of manufacturing an electron-emitting device that draws out electrons from a cold cathode by a lead-out electrode and emits the electron, a transparent conductive film is formed on a transparent insulating substrate, and an opaque conductive cold cathode is formed on the conductive film. Then, a resist layer is formed on the entire surface of the substrate, and back exposure is performed by irradiating light from the lower surface side of the insulating substrate. Is formed, a conductive layer is formed on the insulating layer, the non-exposed portion of the resist layer is removed together with the layers formed above the resist layer, and the remaining conductive layer is used as the extraction electrode.

(2) A second invention of the present application is a method of manufacturing an electron-emitting device, which comprises a cold cathode and an extraction electrode, extracts electrons from the cold cathode by the extraction electrode and emits the electrons, and has different etching characteristics. In addition, the first metal material and the second metal material are such that the respective oxides also have different etching characteristics, and at least the second metal material itself is opaque,
Two metal materials are prepared so that the oxide of the first metal material is transparent, a transparent conductive film is formed on a transparent insulating substrate, and a first metal material layer is formed on this conductive film. A second metal material layer is formed on the first metal material layer, and a second metal material layer is formed.
Etching the metal material layer to form a conical electrode made of the second metal material, and oxidizing all the thickness portions of the exposed region of the first metal material layer and the surface portion of the conical electrode. Thereby forming a first metal material oxide film and a second metal material oxide film, and removing the second metal material oxide film by etching to form a cold cathode made of the second metal material, and forming a cold cathode on the entire surface of the substrate. After forming a resist layer and performing backside exposure by irradiating light from the lower surface side of the insulating substrate, the exposed portion of the resist layer is removed to leave the unexposed portion, and the insulating layer is formed on the entire surface of the substrate. A conductive layer is formed on the layer, and the non-exposed portion of the resist layer is removed together with the layers formed thereabove so that the conductive layer serves as the extraction electrode.

(3) A third invention of the present application is a method for manufacturing an electron-emitting device comprising a cold cathode and an extraction electrode, wherein an electron is extracted from the cold cathode by the extraction electrode to emit the electron, on a transparent insulating substrate. , An opaque conductive cold cathode and at least a conductive film having a light-transmitting property necessary for back surface exposure are formed, a resist layer is formed on the entire surface of the substrate, and the back surface is irradiated with light from the lower surface side of the insulating substrate. The exposed portion of the resist layer is removed by exposure, leaving an unexposed portion, an insulating layer is formed on the entire surface of the substrate, a conductive layer is formed on the insulating layer, and the unexposed portion of the resist layer is removed. This is a structure in which each of the layers formed above is removed and the remaining conductive layer is used as an extraction electrode.

(4) A fourth invention of the present application is a method for manufacturing an electron-emitting device, which comprises a cold cathode and an extraction electrode, extracts electrons from the cold cathode by the extraction electrode and emits the electrons, and has different etching characteristics. In addition, the first metal material and the second metal material are such that the respective oxides also have different etching characteristics, and at least the second metal material itself is opaque,
Two metal materials are prepared so that the oxide of the first metal material is transparent, a first metal material layer is formed on a transparent insulating substrate, and a second metal material is formed on the first metal material layer. Forming a conical electrode made of the second metal material by etching the second metal material layer, and forming a cone-shaped electrode made of the second metal material. The first metal material oxide film and the second metal material oxide film are formed by oxidizing the surface portion of the electrode, and the second metal material oxide film is removed by etching to cool the electrode made of the second metal material. A cathode is formed, a resist layer is formed on the entire surface of the substrate, back exposure is performed by irradiating light from the lower surface side of the insulating substrate, the exposed portion of the resist layer is removed and the non-exposed portion is left, and the entire substrate surface is An insulating layer is formed, a conductive layer is formed on this insulating layer, and a resist layer The exposed portion is removed together with the respective layers formed thereabove, the conductive layer is obtained by such a lead electrode.

(5) The fifth invention of the present application is the same as the above-mentioned first to fourth inventions, further including a step of forming a film made of a different material on the surface of the cold cathode.

(6) In the sixth invention of the present application, in addition to the above-mentioned first to fourth inventions, an etching step for the insulating layer is further added to form a cavity in the surface of the insulating layer facing the cold cathode. It was done.

[0012]

[Operation] According to the present invention, a transparent material is used for both the insulating substrate and the conductive film, and an opaque conductive cold cathode is formed on the conductive film. Therefore,
Backside exposure can be performed using this cold cathode as a mask. By this backside exposure, the resist can be left only on the opaque cold cathode forming portion. After that, the insulating layer and the conductive layer are formed on the entire surface of the substrate, but the insulating layer and the conductive layer formed on the cold cathode are removed by removing the resist. Since the back exposure can be used in this manner, it is not necessary to perform mask alignment in the photolithography process for the resist, and the manufacturing process is simplified.

[0013]

The present invention will be described below based on illustrated embodiments. First, the structure of a conventional general vacuum micro device will be described. FIG. 1 is a cross-sectional view showing a general structure of a vacuum micro device for driving a flat panel display. Here, for convenience of description, only the structure for driving one pixel of the display is shown, and the actual dimensional ratio of each part is ignored. The glass substrate 1 has a sufficient thickness to support this element, and the wiring layer 2 is formed thereon. A cold cathode 3 and an insulating layer 4 are formed on the wiring layer 2, and an extraction electrode 5 is formed on the insulating layer 4. The wiring layer 2 is for supplying a voltage to the cold cathode 3, and is made of a transparent conductive film such as ITO, ZnO: Al, Al, Au, W, Mo, Ti, Ta, N.
It is configured by forming a metal thin film of b, Cr or the like to a thickness of about 0.02 to 1.0 μm. The cold cathode 3 formed thereon is a conical electrode made of a high melting point metal such as W, Ta, Mo. The insulating layer 4 is
The extraction electrode 5 is a layer obtained by depositing SiO ₂ , Al ₂ O ₅ or the like to a thickness of about 0.5 to 3.0 μm, and the extraction electrode 5 includes Al, Au, W, Mo, Ti, Ta, Nb, or the like. The metal thin film is formed to a thickness of about 0.02 to 1.0 μm. The extraction electrode 5 is located at almost the same height as the height of the tip of the cold cathode 3. The above structure is an electron-emitting device to which the present invention is applied.

On the other hand, a structure which should be called an electron receiving element is arranged above the electron emitting element. An anode 7 and a phosphor layer 8 are formed on the lower surface of the glass substrate 6 that constitutes this structure. The anode 7 is made of ITO, ZnO:
A transparent conductive film such as Al is formed to a thickness of about 0.3 to 1.0 μm, and the phosphor layer 8 is formed of a phosphor such as ZnO: Zn to a thickness of about 10 μm. As shown in FIG. 1, the electron-emitting device formed on the upper surface of the glass substrate 1 and the electron-receiving device formed on the lower surface of the glass substrate 6 are arranged so as to face each other, and the space between them is in a vacuum state. Kept in.

The vacuum micro device having such a structure operates as a vacuum tube. That is, the cold cathode 3 is a cathode, the anode 7 is an anode, the extraction electrode 5 is a grid,
As a result, if a predetermined voltage is applied to each electrode, electrons can be extracted from the cold cathode 3 and emitted to the anode 7,
The amount of emitted electrons can be controlled by the voltage applied to the extraction electrode 5. The phosphor layer 8 emits light in response to collision of electrons toward the anode 7. This light emission is observed from above the drawing through the anode 7 and the glass substrate 6.

Among the vacuum micro devices having such a structure, the electron emitting device formed on the glass substrate 1 has the cold cathode 3 arranged at the center and the insulating layer 4 surrounding the cold cathode 3. Further, it has a three-dimensional structure in which the extraction electrode 5 is formed on the insulating layer 4. The first technical problem in producing such an electron-emitting device is how accurately the mask alignment for patterning each layer is performed. For example, if the positional relationship between the cold cathode 3 and the extraction electrode 5 deviates even a little, the cold cathode 3 is eccentrically arranged with respect to the extraction electrode 5, and correct electron emission cannot be performed. Therefore, these alignments must be performed with submicron accuracy. The second problem is how to form the cone-shaped cold cathode 3 having a sharp tip. In order to enable the emission of electrons by a relatively low electric field, it is necessary to make the tip of the cold cathode 3 sharp, but such fine processing is very difficult. Moreover, FIG. 1 shows only the structure corresponding to one pixel of the flat panel display, but in reality, a large number of such structures are arranged vertically and horizontally,
It is necessary to make the processing accuracy of each cold cathode 3 substantially the same. If the processing accuracy of the plurality of cold cathodes 3 arranged vertically and horizontally is uneven, the display screen becomes uneven.

The present invention relates to the technical idea for solving the first problem out of the above-mentioned two problems. In the embodiments described below, the first problem is solved. At the same time, the second problem will be solved at the same time. Regarding the technical idea for solving the second problem, a patent application entitled “Title of Invention: Manufacturing Method of Cold Cathode for Electron Emission” submitted together with the present application (reference number A05
063). However, in the examples described below, since the technical idea disclosed in this other application (hereinafter, referred to as a novel cold cathode manufacturing method) is also used,
The principle will be briefly described here.

First, as shown in FIG. 2A, a conical electrode 9 is formed. The cone-shaped electrode 9 is a rough shape of the cold cathode to be finally formed, and has a substantially cone shape, but the tip portion is not sharp. In the illustrated example, the conical electrode 9 has a so-called frustoconical shape, and the tip portion is circular with a diameter D. Thus, the conical electrode 9 having a conical structure with a flat tip can be formed relatively easily. This is because the shape of the tip does not require so high processing accuracy. In the novel method of manufacturing a cold cathode, the pyramidal electrode 9 having such a rough shape is formed and then its surface is oxidized. FIG. 2 (b) is a cross-sectional view of the state in which the surface is thus oxidized. The oxide film 9a is formed in the hatched portion in the figure, and the portion which is not oxidized remains as the internal electrode 9b. The inventor of the present application found out that the internal electrode 9b thus formed has a conical structure having a sharp tip. That is, after the oxidation, only the oxide film 9a is removed and the internal electrode 9b is left, so that the internal electrode 9b can be used as a cold cathode. The cold cathode thus formed has a sharpened tip, and has a shape suitable for emitting electrons. The sharpening of the tip portion by this method is finer than the sharpening by the conventional etching method.

When the cold cathode is manufactured based on such a principle, it becomes possible to easily manufacture the electron emitting cold cathode having a sharp tip structure suitable for electron emission. Even if a large number of cold cathodes are formed on the same substrate, it is possible to form a cold cathode having a substantially uniform tip structure by uniformly oxidizing the substrates. Here, the thickness of the oxide film 9a formed is determined by the conditions of the oxidation process. In particular, when a metal material is used as the conical electrode 9a and an oxidation process using an anodic oxidation method (an oxidation method performed while applying a positive voltage to the conical electrode 9) is performed, the thickness of the oxide film 9a becomes It can be controlled by (voltage applied to the conical electrode 9). Generally, when a certain layer is oxidized to form an oxide film, the thickness of this oxide film becomes larger than the thickness of the original layer. In other words, the oxidation causes the layer to swell in the thickness direction. That is, the oxidation will be performed both inward and outward. In FIG. 2 (b), the original conical electrode 9
The shape is indicated by a broken line, but the portion outside the contour indicated by the broken line is the portion that is oxidized outward, and the inside portion is the portion that is oxidized inward. Oxidation directed inward is responsible for sharpening the tip of the internal electrode 9b. Therefore, here, the thickness portion of the oxide film 9a formed by inward oxidation is
This is called the inward oxide film thickness d (see FIG. 2 (b)).
When the value of the inward oxide film thickness d exceeds a certain level, the tip of the internal electrode 9b is sharpened.
As a general reference, a sufficiently sharpened internal electrode 9b can be obtained by performing oxidation under the condition that the inward oxide film thickness d = (conical electrode tip end diameter D) / 2 or so. it can.

Now, the process of the most preferred embodiment of the present invention incorporating the above-mentioned novel cold cathode manufacturing method will be described in detail with reference to the sectional views. In the following cross-sectional views, for convenience of illustration, the dimensional ratio of each part is neglected.

<Basic Example> First, as shown in FIG. 3, a glass substrate 11 is prepared as a transparent insulating substrate, and an ITO layer 12 is formed thereon as a transparent conductive film. Thus, the fact that the substrate and the conductive film are both transparent is an important feature of the present invention. Subsequently, a tantalum layer 13 as a first metal material layer and an aluminum layer 14 as a second metal material layer are formed thereon (thickness of each layer will be described later). To form each layer,
For example, a sputtering method or a vacuum evaporation method may be used. The first metal material and the second metal material are not limited to tantalum and aluminum as described above, and any combination of metals may be used as long as they satisfy the following conditions. First, it is necessary that the two materials have different etching characteristics from each other and the respective oxides also have different etching characteristics from each other. Moreover, at least the second metal material itself must be opaque and the oxide of the first metal material must be transparent. The combination of tantalum as the first metal material and aluminum as the second metal material satisfies these conditions. That is, tantalum and aluminum have different etching characteristics, and tantalum oxide and aluminum oxide also have different etching characteristics. Moreover, aluminum is itself opaque and tantalum oxide is transparent.

Subsequently, a photoresist is applied on the aluminum layer 14 to perform patterning in a specific shape, as shown in FIG.
A resist layer 15 as shown in is formed. Since this embodiment is an example of forming a conical cold cathode, the resist layer 15 has a circular pattern in plan view, but if a pyramidal cold cathode is formed, a polygonal pattern is formed accordingly. And it is sufficient. Next, using the resist layer 15 as a mask, the aluminum layer 14 is etched. In this example, an etching solution for aluminum (MR-ALE manufactured by Hishie Chemical Co., Ltd.) was heated and maintained at about 40 ° C., and the entire substrate was immersed in this solution for about 4.5 minutes to perform etching. Since tantalum has different etching characteristics, it is not etched by the aluminum etching solution. As a result, as shown in FIG. 5, a part of the aluminum layer 14 remains as the conical electrode 16. This conical electrode 16
Has a so-called frustoconical shape, which is a rough shape of the cold cathode to be manufactured. Then, the resist layer 15 is removed by sufficiently washing with water and then drying.

Subsequently, an oxidation step, which is a feature of the above-mentioned novel cold cathode manufacturing method, is performed. In this embodiment, the oxidization is performed by using the anodic oxidation method which can easily control the oxide film thickness. That is, as an electrolyte solution, 5%
An aqueous solution (% by weight) of ammonium borate is prepared, and the fully dried substrate is immersed in this stirred electrolyte solution. On the other hand, a platinum plate is similarly immersed as a counter electrode, and the conical electrode 16 is provided between the counter electrode and the conical electrode 16.
A voltage was applied so that the side became an anode, and oxidation was performed at room temperature at a constant current density of 0.5 mA / cm ² .
The applied voltage was increased from 0 V to a predetermined formation voltage, and oxidation was performed until an oxide film having a predetermined film thickness described later was obtained. The electrolyte solution used for this anodic oxidation is not limited to the ammonium borate aqueous solution described above, and various other electrolyte solutions can be used. For example, as the solvent used for the electrolyte solution, various organic solvents (ethylene glycol, methanol, glycerin, propionic acid, etc.) can be used in addition to water, and as the solute, citric acid, adipic acid, boric acid, Neutral organic acids such as lactic acid and acrylic acid, borax, ammonium citrate, ammonium tartrate, ammonium dihydrogen phosphate, sodium phosphate, potassium phosphate,
A neutral, weakly acidic, or weakly alkaline salt such as sodium sulfate, potassium sulfate, sodium carbonate, or potassium carbonate can be used. Further, as the counter electrode, aluminum, stainless steel, carbon or the like can be used instead of platinum.

FIG. 6 is a cross-sectional view showing a state when the above-mentioned oxidation step is completed. An oxide film 16a (Al ₂ O ₃ ) is formed on the surface of the conical electrode 16 by oxidation,
The portion that was not oxidized remains as the internal electrode 16b. In addition, in the above-mentioned oxidation process, the conical electrode 16
At the same time, the exposed region of the tantalum layer 13 will also be oxidized. Therefore, the exposed region of the tantalum layer 13 becomes the oxide film 13a (Ta ₂ O ₅ ) and the non-exposed region remains as the tantalum layer 13b. The tantalum layer 13 is formed in order to protect the ITO layer 12 from being damaged by the above-described anodic oxidation process. The point to be noted here is that the exposed region of the tantalum layer 13 is
The point is that all the thickness parts are oxidized. In other words, the exposed area of the tantalum layer 13 is not limited to the surface,
Oxidation is carried out to the deep part, and all are oxide film 1
It has changed to 3a. This is the oxide of tantalum (Ta
₂ O ₅ ) pays attention to the property that ₂ O ₅ has a light-transmitting property, and is a consideration for enabling backside exposure, which is a feature of the present invention, in a later step. That is, since tantalum itself does not have a light-transmitting property, the exposed region of the tantalum layer 13 is oxidized over the entire thickness to be changed to the light-transmitting oxide film 13a in order to perform back exposure. It is necessary.

After the completion of the oxidation step, the entire substrate is thoroughly washed with water and dried to remove the aluminum oxide film 16a. In this example, the stripping solution was 5% phosphoric acid + 2.
% Chromic acid aqueous solution was prepared, the aqueous solution was heated and maintained at about 85 ° C., and the entire substrate was immersed for about 15 minutes to perform peeling. As a result, as shown in FIG. 7, only the aluminum oxide film 16a is peeled and removed, and the exposed internal electrode 16b forms the cold cathode 17. In this peeling process, the tantalum oxide film 13a is not affected at all.

Subsequently, a back surface exposure step for the resist, which is a feature of the present invention, is performed. First, as shown in FIG. 8, a resist layer 18 is formed. The resist layer 18 needs to have a thickness such that at least the cold cathode 17 is completely covered. After resist application, pre-baking is performed, and back exposure, which is a feature of the present invention, is performed here. That is, the resist layer 18 is exposed to light from the bottom of the drawing.
As described above, the glass substrate 11 and the ITO layer 12 are transparent, and the tantalum oxide film 13a also has a light-transmitting property. Therefore, when backside exposure is performed from the backside of the substrate, the tantalum layer 13b and the cold cathode 17 made of aluminum are formed.
By using the mask as a mask, the resist layer 18a can be left only in the formation region of the cold cathode 17, as shown in FIG. Such backside exposure does not require a special mask plate, and thus mask alignment work is unnecessary. Moreover, since so-called self-alignment is performed, no alignment error occurs.

Subsequently, as shown in FIG. 10, an insulating layer 19 is formed on the entire surface of the substrate. As the insulating layer 19, for example, SiO ₂ , Al ₂ O ₃ , shot glass or the like may be formed by a sputtering method or a vacuum evaporation method.
Further thereon, as shown in FIG. 11, the gate electrode layer 20
To form. As the gate electrode layer 20, for example, a metal material such as Al, Au, W, Mo, Ti, Ta, Nb may be formed by a sputtering method or a vacuum evaporation method. Finally, if the resist layer 18a is peeled off (so-called lift-off), and sufficiently washed with water and dried, the structure shown in FIG.
The structure shown in 2 is obtained. This structure is equivalent to the structure of the electron-emitting device shown in the lower part of FIG. For removing the resist layer 18a, for example, a removing liquid such as acetone may be used. Of course, any stripping solution may be used as long as it is capable of stripping the resist layer 18a without affecting other structural parts.

Next, the thickness of each layer and the conditions of anodic oxidation in the above steps will be examined. First, FIG.
Consider the thicknesses of the ITO layer 12, the tantalum layer 13, and the aluminum layer 14 in FIG. Since the ITO layer 12 is a conductive film that functions as a wiring layer for the cold cathode,
There is no particular limitation as long as the wiring layer has an appropriate thickness. In this embodiment, the ITO has a thickness of about 0.1 to 0.5 μm.
Layer 12 was formed. On the other hand, it is preferable that the tantalum layer 13 and the aluminum layer 14 have an optimum thickness determined in consideration of the size of the cold cathode 17 to be formed and the conditions of anodic oxidation. First, the thickness of the aluminum layer 14 is preferably about half the diameter of the cold cathode 17 to be formed. For example, if a conical cold cathode 17 having a diameter of 5 μm is formed (the diameter of the resist layer 15 is 5 μm).
m) and the thickness of the aluminum layer 14 is preferably about 2.5 μm. With such a thickness, the pyramidal electrode 16 having a pointed tip to some extent can be formed by etching as shown in FIG.

On the other hand, the thickness of the tantalum layer 13 needs to be determined based on the conditions of anodic oxidation. This is because, as described above, when the anodic oxidation is completed, the exposed region of the tantalum layer 13 needs to be oxidized for all the thickness portions (the reason is that all the exposed regions of the tantalum layer 13 must be oxidized so that the back surface exposure can be performed later). This is because it is necessary to change the thickness part of the oxide film to a translucent oxide film). By the way, the condition of the anodic oxidation should be determined based on the inward oxide film thickness d shown in FIG. 2 (b), and the value of this inward oxide film thickness d is the conical shape shown in FIG. 2 (a). The diameter D of the head portion of the electrode 9 should be taken into consideration (as described above, if d = D / 2 or so, an internal electrode 9b having a sufficiently sharp tip can be obtained).

Now, more specifically, the optimum condition of anodic oxidation and the optimum value of the thickness of the tantalum layer 13 will be determined taking the case of forming the conical cold cathode 17 having a diameter of 5 μm as an example. In FIG. 5, when etching is performed using the resist layer 15 having a circular pattern with a diameter of 5 μm,
The diameter D of the cutting head of the resulting conical electrode 16 is 0.24 μm.
It has been confirmed by experiments that it is about the same level. Therefore, the value of the inward oxide film thickness d shown in FIG.
It is preferably about 12 μm. Here, when the relationship between the formation voltage (voltage applied at the time of oxidation) and the film thickness of the oxide film to be formed in performing the anodic oxidation is determined, the relationship shown in the table of FIG. 13 is obtained. The formation voltage in this table indicates the voltage value applied to the conical electrode during the oxidation step, and the anodic oxide film thickness is the thickness of the oxide film obtained when each formation voltage is applied. And the inward oxide film thickness d.
Indicates the inward oxide film thickness of the aluminum oxide film obtained by oxidation.

As described above, when the circular pattern having a diameter of 5 μm is used, the value of the inward oxide film thickness d is 0.12 μm.
It is preferably about the same. Therefore, according to this table, it is understood that the anodic oxidation may be performed under the condition that the formation voltage is 150V. In this way, the optimum conditions for anodic oxidation can be determined. On the other hand, under the anodizing condition of the formation voltage of 150 V, the oxide film thickness of the tantalum layer is about 0.25 μm according to the table of FIG. 0.2 for tantalum
When an oxide film with a thickness of 5 μm is formed, this 0.25 μ
0.1 μm of m is the inward oxide film thickness. Therefore, it is understood that the original thickness of the tantalum layer 13 is preferably 0.1 μm.

<Modification 1> Next, some modifications of the present invention will be described. In the modification shown in FIG. 14, a surface coating 21 made of another metal is formed on the surface of the cold cathode produced by the above method by a sputtering method or a vacuum evaporation method. For example, when a cold cathode made of aluminum is formed, aluminum generally has a relatively low melting point and is easily oxidized, so that it is not necessarily a suitable material for a cold cathode for electron emission. Therefore, by forming a metal film such as tantalum on the surface of the aluminum cold cathode and using it as the surface film 21, a cold cathode more suitable for electron emission can be generated. This surface film 21
If the thickness of the cold cathode is suppressed to about 0.05 μm, the sharpness of the tip of the cold cathode is not affected. As the material of the surface film 21, tantalum (Ta), W, Mo, Ti, N
Metals such as b, Hf, Cr, Pt, Au, TiN, Fe
N and other nitrides, WC, NbC and HfC and other carbides,
Etc. can be used.

<Modification 2> In a modification shown in FIG. 15, an etching step is added to the insulating layer 19 to form a cavity 19z in the surface of the insulating layer 19 facing the cold cathode 17. For example, when SiO ₂ is used as the insulating layer 19, a BHF solution (28 ml of HF + 170) is used.
By immersing in 1 ml of H ₂ O + 113 g of NH ₄ F) for 1 minute, the side portion of the insulating layer 19 is removed by etching by about 0.1 μm, and the cavity portion 19z is formed.
In this way, the cavity 19z is formed in the portion surrounding the cold cathode 17.
By forming the above, there is an advantage that the insulating property between the cold cathode 17 and the gate electrode layer 20 is further improved.

<Modification 3> This modification 3 is an example in which the ITO layer 12 is unnecessary in the basic embodiment described above. First, as shown in FIG. 16, a transparent glass substrate 1
1, a tantalum layer 13 as a first metal material layer, and an aluminum layer 1 as a second metal material layer thereon.
4 is formed into a film. This structure is obtained by omitting the ITO layer 12 from the structure of the basic embodiment shown in FIG. As described above, Modification 3 is characterized in that the ITO layer 12 is unnecessary. The reason will be described later. Also, the thickness of the tantalum layer 13 is slightly different from that of the basic embodiment. That is, in the basic example, the thickness of the tantalum layer 13 was set to 0.1 μm, but in the third modification, it is set to about 0.12 to 0.125 μm, which is set to be slightly thicker. The reason for this will be described later.

Subsequently, a photoresist is applied on the aluminum layer 14 to pattern it into a specific shape, and then, as shown in FIG.
7, a resist layer 15 as shown in FIG. 7 is formed, the aluminum layer 14 is etched using the resist layer 15 as a mask, and as shown in FIG.
A structure with 6 is obtained. This step is exactly the same as the step in the basic embodiment described above. After this, the resist layer 15
The point that the anodic oxidation is performed after removing the is also the same as the above-mentioned basic embodiment. The anodizing condition is that the formation voltage is 15
It was set at 0V. However, the difference from the basic embodiment is that the thickness of the tantalum layer 13 is set to be slightly thicker as described above. Therefore, even if the anodic oxidation is performed under the same conditions, in the third modification, the tantalum layer 13 is not completely oxidized with respect to the entire thickness, and a part of the substrate side remains as a layer that has not been oxidized. .
FIG. 19 shows a state after completion of this anodic oxidation. The tantalum layer 1 is formed on the non-exposed portion covered with the internal electrode 16b.
3b remains, which is the same as in the basic example, except that the exposed side is oxidized on the surface side to form the oxide film 13a, but the substrate side is not oxidized. It remains as the remaining tantalum layer 13c. In this embodiment, the residual tantalum layer 13 having a thickness of about 0.025 μm is used.
c remained.

Then, similarly to the basic embodiment, the aluminum oxide film 16a shown in FIG.
As shown in 0, the cold cathode 17 is exposed. Then, as shown in FIG. 21, a resist layer 18 is formed on the entire surface, and a part of the resist layer 18 is exposed by backside exposure. However, the conditions of this backside exposure are slightly different from those of the basic embodiment. In the basic embodiment, the backside exposure is performed in the structure as shown in FIG.
Since both the TO layer 12 and the oxide film 13a are transparent, the portion of the resist layer 18 shaded by the tantalum layer 13b and the cold cathode 17 was the non-exposed portion, and the other portion was the exposed portion. However, in this modified example 3,
In the structure as shown in FIG. 21, backside exposure is performed, and a portion to be originally exposed (of the resist layer 18,
The light irradiated on the portion other than the portion shaded by the tantalum layer 13b and the cold cathode 17 is the remaining tantalum layer 13
The light is shielded by c. Remaining tantalum layer 13
Since c is a metal layer of tantalum, it does not have a light-transmitting property like an oxide layer. However, as mentioned above, the thickness is 0.025
Since it is a very thin film of about μm, it does not have a perfect light shielding property. Therefore, the portion to be originally exposed is irradiated with light by this rear surface exposure although it is weaker than in the basic embodiment. Therefore, in the third modification, the resist layer 18 is sufficiently exposed to light by setting the back exposure time to be long. Specifically, while the backside exposure in the basic example was several seconds, the backside exposure in this modified example 3 could perform sufficient exposure by taking about 3 minutes. .

When the back exposure of the resist layer 18 is completed in this way, it is developed to obtain the structure shown in FIG. The structure of FIG. 22 is equivalent to the structure shown in FIG. 9 in the basic embodiment. That is, the role of the ITO layer 12 in the structure shown in FIG.
The remaining tantalum layer 13c is fulfilled. In the first place, the ITO layer 12 is formed in the basic example in order to function as a wiring layer for the cold cathode 17. However, in this modified example 3, since the residual tantalum layer 13c can function as a wiring layer for the cold cathode 17, it is not necessary to provide the ITO layer 12. After the structure of FIG. 22 is obtained, the insulating layer 19 and the gate electrode layer 20 are formed as in the basic example.

In summary, the feature of the third modification is that the tantalum layer 13 remains on the substrate side without oxidizing a part of the tantalum layer 13.
3c, and the remaining tantalum layer 13c is used as a substitute for the ITO layer 12 in the basic embodiment. At this time, it is important to set the thickness of the remaining tantalum layer 13c. If the remaining tantalum layer 13c becomes too thick, the light transmittance will decrease, and it will be a problem that the resist layer 18 cannot be sufficiently exposed in the step of back exposure. On the contrary, the remaining tantalum layer 1
If 3c is too thin, the resistivity of the conductive layer becomes high, which causes a problem in the function of the cold cathode 17 as a wiring layer. Therefore, when anodizing a tantalum layer having a thickness of 0.12 μm from the surface side, the formation voltage during anodization (this is a condition that affects the thickness of the remaining tantalum layer) and the transmittance of the remaining tantalum layer. I investigated the relationship with FIG. 23 is a graph showing the results of this experiment. The formation voltage is plotted on the horizontal axis and the transmittance is plotted on the vertical axis, and the respective relationships are shown. It can be seen that the higher the formation voltage, the higher the transmittance. This is because the higher the formation voltage is, the more the anodic oxidation progresses and the thickness of the remaining tantalum layer becomes smaller. The formation voltage during anodic oxidation in the present modification is 150 V, and oxidation under these conditions provides a residual tantalum layer 13c having a thickness that can sufficiently function as a wiring layer, and the residual tantalum layer 13c having this thickness has a rear surface. A transmittance that allows sufficient exposure to light is obtained.

<Modification 4> In Modification 1 described above, in the last step, another metal film was formed as the surface film 21 on the surface of the cold cathode 17. In Modification 4 described here, the formation of the surface film 21 is not performed in the last step, but is formed in the process of Modification 3 described above. Therefore, the same steps as those in Modification 3 described above are performed until the stage where the structure shown in FIG. 20 is obtained. And FIG.
After the structure shown in FIG. 24 is obtained, a negative resist layer 22 is formed on the entire surface of the substrate as shown in FIG. In terms of forming a resist layer, it is exactly the same as the next step of Modification 3 described above, but in Modification 3, as shown in FIG. 21, a positive type resist layer 18 is formed. In the next step of Modification 4, as shown in FIG. 24, a negative resist layer 22 is formed. More specifically, as a negative resist, OMR-8510cp manufactured by Tokyo Ohka Co., Ltd. is used, and a spinner is used to rotate at 5 rpm at 5 rpm.
After applying for 2 seconds, the negative resist layer 22 having a thickness of about 0.2 μm was formed by applying at a rotation speed of 2000 rpm for 40 seconds.

Subsequently, in the state shown in FIG. 24, the first back surface exposure is performed from the back surface side of the substrate to form the negative resist layer 2
Part 2 is partially exposed. As described in Modification 3, since the remaining tantalum layer 13c is a very thin film having a thickness of about 0.025 μm, the remaining tantalum layer 13c has some translucency, and the tantalum layer 13b is shaded so that the unexposed portion is not exposed. However, a part of the light passes through the remaining tantalum layer 13c to become an exposed portion. Specifically, the exposure time of about 10 to 20 minutes allowed the negative resist layer 22 to be sufficiently exposed to light. Next, when the negative resist layer 22 is developed, the exposed portion remains and the unexposed portion is removed because it is a negative type. FIG. 25 shows
The state after development is shown, and only the resist layer 22a, which is the exposed portion, remains.

Then, in the state shown in FIG. 25, a metal such as tantalum or tungsten (a metal forming a surface film) is deposited on the entire surface of the substrate by a sputtering method to form a surface having a thickness of about 0.01 to 0.05 μm. A film 23 is formed.
Then, when the resist layer 22a is peeled off by lift-off, as shown in FIG. 27, only the surface film 23 formed on the surface of the cold cathode 17 remains. After this, see Figure 2.
8, a positive type resist layer 18 is formed on the entire surface, and the resist layer 18 is formed by the second back exposure.
Expose a part of. Specifically, in about 3 minutes,
It was possible to perform sufficient exposure.

When the back exposure of the resist layer 18 is completed in this way, it is developed to obtain the structure shown in FIG. The structure of FIG. 29 is obtained by further forming a skin layer 23 on the surface of the cold cathode 17 in the structure shown in FIG. 22 in the modified example 3. After that, the insulating layer 19 and the gate electrode layer 20 are formed as in the basic example.

In Modification 1, another metal film is formed as the surface film 21 on the surface of the cold cathode 17 in the last step. In this case, in the step of forming the surface film 21, the cold cathode 17 and the gate electrode are formed. There is a risk of short circuit with layer 20. The method according to the modification 4 described here does not cause such a problem. Note that this modification 4 incorporates a step of forming a surface film in the middle of the steps of the above-described modification 3, but may incorporate a step of forming a surface film in the middle of the steps of the basic embodiment. It is possible. In this case, I
The TO layer 12 may be formed in advance, and the remaining tantalum layer 13c may be entirely oxidized in the anodic oxidation process.

<Modification 5> In this modification 5, the surface film 21 is used.
Is another method for forming the process in the process of the modified example 3. First, the same steps as those in Modification 3 described above are performed until the stage where the structure shown in FIG. 22 is obtained. Then, when the structure shown in FIG. 22 is obtained, as shown in FIG. 30, a negative resist layer 22 is formed on the entire surface of the substrate. More specifically, as a negative resist, Tokyo Ohka Co., Ltd .: OMR-8
500 rp with a spinner using 5 35 cp
The negative resist layer 22 having a thickness of about 0.6 μm was formed by coating at a rotation speed of m for 5 seconds and then at a rotation speed of 2000 rpm for 40 seconds. Then, in this state, when the second back exposure is performed and development is performed, the non-exposed portion of the negative resist layer 22 is removed, and only the exposed portion remains as the resist layer 22a. By the development on the negative resist, the positive resist layer 18a is also removed. Therefore, after development, the structure shown in FIG. 31 is obtained.

Then, in the state shown in FIG. 31, a metal such as tantalum or tungsten (a metal forming a surface film) is deposited on the entire surface of the substrate by a sputtering method, and then, as shown in FIG.
As shown in, the surface film 23 having a thickness of about 0.01 to 0.05 μm is formed. Then, if the resist layer 22a is peeled off by lift-off, the structure shown in FIG. 27 can be obtained as in the method of Modification 4 described above. That is, the cold cathode 1
Only the surface film 23 formed on the surface of No. 7 remains. After this, as shown in FIG. 28, a positive type resist layer 18 is formed on the entire surface, and by the third back exposure,
A part of the resist layer 18 is exposed to light. In this way, when the back surface exposure to the resist layer 18 is completed, it is developed to obtain the structure shown in FIG. 29, and further, the insulating layer 19 and the gate electrode layer 20 are formed.

This modified example 5 also incorporates the step of forming a surface film in the process of the modified example 3 described above, but the surface film according to the modified example 5 is formed in the process of the basic embodiment. It is also possible to incorporate the step of doing. In this case, the ITO layer 12 may be formed in advance, and the entire tantalum layer 13c may be oxidized without leaving the remaining tantalum layer 13c in the anodic oxidation process.

[0047]

As described above, according to the present invention, the electron-emitting device can be manufactured by utilizing the back exposure.
The electron-emitting device can be easily manufactured by omitting the mask alignment process as much as possible.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure of a conventional general vertical vacuum micro device.

FIG. 2 is a diagram showing a basic principle of a novel method for manufacturing a cold cathode for electron emission according to the present invention.

FIG. 3 is a cross-sectional view showing a state in which a three-layer structure is formed on a substrate in the example of the present invention.

4 is a cross-sectional view showing a state in which a resist layer 15 having a circular pattern is formed in the state shown in FIG.

5 is a cross-sectional view showing a state in which a pyramidal electrode 16 is formed by performing etching with the resist layer 15 as a mask in the state shown in FIG.

6 is a cross-sectional view showing a state where anodic oxidation is performed on the conical electrode 16 shown in FIG.

7 is a cross-sectional view showing a state in which oxide film 16a shown in FIG. 6 is removed.

8 is a cross-sectional view showing a state in which a resist layer 18 has been formed in the state shown in FIG.

9 is a cross-sectional view showing a state where back exposure is performed and a resist layer is patterned in the state shown in FIG.

10 is a cross-sectional view showing a state where an insulating layer 19 is further formed in the state shown in FIG.

11 is a cross-sectional view showing a state where a gate electrode layer 20 is further formed in the state shown in FIG.

FIG. 12 shows a resist layer 18 in the state shown in FIG.
It is sectional drawing which shows the state which peeled a.

FIG. 13 is a table showing various conditions for anodization (relationship between formation voltage and oxide film thickness).

14 is a cross-sectional view showing a structure of Modification 1 in which a surface film 21 is further formed on the surface of the cold cathode 17 in the state shown in FIG.

FIG. 15 further shows an insulating layer 19 in the state shown in FIG.
FIG. 13 is a cross-sectional view showing a structure of Modification 2 in which a cavity 19z is formed by performing etching on the.

FIG. 16 is a cross-sectional view showing a state in which a two-layer structure is formed on a substrate in Modification 3 of the present invention.

17 is a sectional view showing a state in which a resist layer 15 having a circular pattern is formed in the state shown in FIG.

FIG. 18 is a resist layer 15 in the state shown in FIG. 17;
FIG. 6 is a cross-sectional view showing a state in which a conical electrode 16 is formed by performing etching using the as a mask.

19 is a cross-sectional view showing a state where anodic oxidation is performed on the surface portions of the pyramidal electrode 16 and the tantalum layer 13 shown in FIG.

20 is a cross-sectional view showing a state in which oxide film 16a shown in FIG. 19 is removed.

21 is a plan view of the resist layer 18 in the state shown in FIG.
It is sectional drawing which shows the state which formed.

22 is a cross-sectional view showing a state in which back exposure is performed to pattern the resist layer in the state shown in FIG. 21.

FIG. 23 is a graph showing the relationship between the formation voltage of the tantalum layer during anodic oxidation and the transmittance of the remaining tantalum layer that has not been oxidized.

FIG. 24 is a cross-sectional view showing a state in which a negative resist layer 22 is formed in the state shown in FIG. 20 in Modification 4 of the present invention.

FIG. 25 is a cross-sectional view showing a state in which back exposure is performed and the resist layer is patterned in the state shown in FIG. 24.

26 is a cross-sectional view showing a state in which a skin layer 23 is formed in the state shown in FIG.

27 is a plan view of the resist layer 22 in the state shown in FIG.
It is sectional drawing which shows the state which peeled and removed a.

FIG. 28 is a view showing the resist layer 18 in the state shown in FIG.
It is sectional drawing which shows the state which formed.

29 is a cross-sectional view showing a state where back exposure is performed and the resist layer is patterned in the state shown in FIG. 28. FIG.

FIG. 30 is a cross-sectional view showing a state in which a negative resist layer 22 is formed in the state shown in FIG. 22 in Modification 5 of the present invention.

FIG. 31 is a cross-sectional view showing a state where back exposure is performed and the resist layer is patterned in the state shown in FIG. 30.

32 is a cross-sectional view showing a state in which a skin layer 23 is formed in the state shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Glass substrate 2 ... Wiring layer 3 ... Cold cathode 4 ... Insulating layer 5 ... Extraction electrode 6 ... Glass substrate 7 ... Anode 8 ... Phosphor layer 9 ... Conical electrode 9a ... Oxide film 9b ... Internal electrode 11 ... Glass substrate 12 ... ITO layer 13 ... Tantalum layer 13a ... Tantalum oxide film 13b ... Tantalum layer 14 ... Aluminum layer 15 ... Resist layer 16 ... Conical electrode 16a ... Aluminum oxide film 16b ... Internal electrode 17 ... Cold cathode 18, 18a ... Resist layer 19 ... Insulating layer 19z ... Cavity 20 ... Gate electrode layer 21 ... Surface film 22, 22a ... Negative resist layer 23 ... Surface film

Claims (6)

[Claims] 1. A method of manufacturing an electron-emitting device comprising a cold cathode and an extraction electrode, wherein an electron is extracted from the cold cathode by the extraction electrode to emit the electron, wherein a transparent conductive film is formed on a transparent insulating substrate. An opaque conductive cold cathode is formed on the conductive film, a resist layer is formed on the entire surface of the substrate, and back exposure is performed by irradiating light from the lower surface side of the insulating substrate. Part is removed to leave the non-exposed part, an insulating layer is formed on the entire surface of the substrate, a conductive layer is formed on this insulating layer, and the non-exposed part of the resist layer is removed together with the layers formed above it. A method for manufacturing an electron-emitting device, characterized in that the remaining conductive layer is used as an extraction electrode. 2. A method of manufacturing an electron-emitting device comprising a cold cathode and an extraction electrode, wherein electrons are extracted from the cold cathode by the extraction electrode to emit the electrons, the oxides having different etching characteristics from each other. The first metal material and the second metal material have mutually different etching characteristics, and at least the second metal material itself is opaque, and the oxide of the first metal material is transparent. Are prepared, a transparent conductive film is formed on a transparent insulating substrate, a first metal material layer is formed on the conductive film, and a first metal material layer is formed on the transparent conductive film. A second metal material layer is formed on the first metal material layer, and the second metal material layer is etched to form a conical electrode made of the second metal material. All thickness parts and above The first metal material oxide film and the second metal material oxide film are formed by oxidizing the surface portion of the electrode, and the second metal material oxide film is removed by etching from the second metal material. A cold cathode is formed, a resist layer is formed on the entire surface of the substrate, and back exposure is performed by irradiating light from the lower surface side of the insulating substrate, and the exposed portion of the resist layer is removed to leave the non-exposed portion. Forming an insulating layer on the entire surface of the substrate, forming a conductive layer on the insulating layer, removing the non-exposed portion of the resist layer together with the layers formed above it, and using the conductive layer as an extraction electrode. And a method for manufacturing an electron-emitting device. 3. A method of manufacturing an electron-emitting device comprising a cold cathode and an extraction electrode, wherein an electron is drawn from the cold cathode by the extraction electrode to emit the electron, wherein an opaque conductive cooling film is provided on a transparent insulating substrate. A cathode and at least a light-transmitting conductive film necessary for back exposure are formed, a resist layer is formed on the entire surface of the substrate, and back exposure is performed by irradiating light from the lower surface side of the insulating substrate to form the resist layer. The exposed portion is removed to leave the non-exposed portion, an insulating layer is formed on the entire surface of the substrate, and a conductive layer is formed on the insulating layer.
A method for manufacturing an electron-emitting device, characterized in that the non-exposed portion of the resist layer is removed together with the layers formed above it, and the remaining conductive layer is used as an extraction electrode. 4. An electron-emitting device manufacturing method comprising a cold cathode and an extraction electrode, wherein an electron is drawn from the cold cathode by the extraction electrode to emit the electron, the oxide having different etching characteristics from each other. The first metal material and the second metal material have mutually different etching characteristics, and at least the second metal material itself is opaque, and the oxide of the first metal material is transparent. Are prepared, a first metal material layer is formed on a transparent insulating substrate, and a second metal material layer is formed on the first metal material layer. The second metal material layer is etched to form a conical electrode made of the second metal material, and the surface portion of the exposed region of the first metal material layer and the surface portion of the conical electrode are oxidized. By the first A metal material oxide film and a second metal material oxide film are formed, and the second metal material oxide film is removed by etching to form a cold cathode made of the second metal material, and a resist layer is formed on the entire surface of the substrate. Then, back exposure is performed by irradiating light from the lower surface side of the insulating substrate, the exposed portion of the resist layer is removed to leave the non-exposed portion, and the insulating layer is formed on the entire surface of the substrate. A method of manufacturing an electron-emitting device, comprising forming a conductive layer on the substrate, removing the non-exposed portion of the resist layer together with the layers formed above the conductive layer, and using the conductive layer as an extraction electrode. 5. The method of manufacturing an electron-emitting device according to claim 1, further comprising the step of forming a film made of a different material on the surface of the cold cathode. 6. The method according to claim 1, further comprising the step of etching the insulating layer to form a cavity on the surface of the insulating layer facing the cold cathode. Method for manufacturing electron-emitting device.