JPH06203749A - Manufacture of electron emitting element - Google Patents

Abstract

PURPOSE:To provide an electron emitting element wherein stable emission of an electron can be performed. CONSTITUTION:(a) A wiring layer 12, insulating layer 13 and an electrode layer 14 are formed on a glass substrate 11, and etching is performed with a resist layer 15 serving as a mask, to form an insulating layer 13a and a draw out electrode 14a. A conductive material is deposited in the above, to form electrode layers 16a, 16b. (b) The resist layer 15 is separated to remove the electrode layer 16a. (c) A resist layer 17 is formed on the electrode layer 16b, to etching- remove a side part of the electrode layer 16b. (d) A clearance can be ensured between a cold cathode 16c and the draw out electrode 14a, to complete an electron emitting element.

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 for forming a vacuum micro device or 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]

As described above, the vacuum micro device is the same in principle as a vacuum tube, but the size thereof is so minute that it cannot be compared with a vacuum tube. In particular, the portion of the electron-emitting device where the cold cathode and the extraction electrode are formed needs to be processed into a structure that easily emits electrons, but such processing requires a very high technology. I need. In particular, the electron-emitting tip of the cold cathode is processed in the following radii of curvature 1 [mu] m, 10 ⁷
It is necessary to emit electrons so that a strong electric field of about V / cm is concentrated at this tip, and it has been difficult to perform precise processing capable of stable electron emission by the conventional method.
When this element is used for driving a flat panel display, display control of one pixel of the display is performed by each element. Therefore, if there is variation in the processing of the electron emitting portion for each element, there arises a problem that a uniform display cannot be obtained on the display screen.

Therefore, an object of the present invention is to provide a method of manufacturing an electron-emitting device capable of stable electron emission.

[0006]

Means for Solving the Problems (1) A 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 an extraction electrode and emits the electrons to an anode, a first conductive layer for wiring to the cold cathode is formed on a substrate. Forming an insulating layer on the first conductive layer and forming a second conductive layer on the insulating layer to form an extraction electrode; and forming a first resist layer on the second conductive layer. And forming an opening at a position corresponding to the cold cathode formation region of the resist layer, and patterning the first resist layer as a mask to form a second
Of a part of the conductive layer and a part of the insulating layer by etching, a third conductive layer for forming a cold cathode is deposited on the entire surface of the substrate, and the first resist layer is replaced with the second conductive layer. By removing the third conductive layer from a region other than the cold cathode forming region, and the third conductive layer left unremoved.
Forming a second resist layer on the upper surface of the conductive layer in a region smaller than the cold cathode forming region, and using the second resist layer as a mask to etch away the side portion of the third conductive layer. The above steps are performed, and the remaining second conductive layer is used as an extraction electrode, and the remaining third conductive layer is used as a cold cathode to form an electron-emitting device.

(2) The second invention of the present application is the method for manufacturing an electron-emitting device according to the first invention, wherein the third conductive layer is formed of a non-solid solution metal alloy, and a material of this alloy is used. The surface of the third conductive layer is etched by using an etching method in which the etching rate is different between the different metals, and a projection structure suitable for electron emission is formed on the surface of the cold cathode composed of the third conductive layer. The steps are further performed.

(3) A third invention of the present application is the method for manufacturing an electron-emitting device according to the first invention, wherein the third conductive layer is deposited by an oblique vapor deposition method, and the third conductive layer is formed. A projection structure suitable for electron emission is formed on the surface of the constructed cold cathode.

(4) A fourth invention of the present application is the method for manufacturing an electron-emitting device according to the above-mentioned first invention, wherein the third conductive layer has a two-layer structure made of different metals. A step of etching only the upper layer of the two-layer structure in a predetermined pattern by an etching method with a different etching rate and forming a protrusion structure suitable for electron emission by the upper layer portion is further performed. It is a thing.

(5) A fifth invention of the present application is the method for manufacturing an electron-emitting device according to the above-mentioned first invention, wherein the surface of the formed cold cathode is irradiated with an electron beam to perform patterning,
The step of forming a protrusion structure suitable for electron emission is further performed.

(6) A sixth invention of the present application is the method for manufacturing an electron-emitting device according to the first invention, wherein a cold cathode forming region is circular to form a cylindrical cold cathode.
A patterning step of forming a projection structure suitable for electron emission is further performed along the circumference of the upper surface of the cylindrical cold cathode.

[0012]

[Work]

(1) In the manufacturing method according to the first invention of the present application, first, a conductive layer to be a lead electrode is formed on an insulating layer formed on a substrate. Subsequently, a cold cathode forming region is defined, and a hole is dug in a portion of the insulating layer and the conductive layer corresponding to the cold cathode forming region. A conductive layer to be a cold cathode is deposited in this hole. Finally, the side portion of the conductive layer to be the cold cathode is etched so that a predetermined space is provided between the cold cathode and the extraction electrode. In such a manufacturing method,
Difficult microfabrication process can be avoided and stable machining is always possible. Further, although etching for forming a cold cathode is performed at the final stage, this etching can process the cold cathode into a shape suitable for electron emission (for example, a shape having an acute angle portion).

In the electron-emitting device, the shape of the cold cathode is very important. That is, stable electron emission must be performed from this cold cathode. In order to perform such stable electron emission, it is generally considered that a fine protrusion structure is necessary. The second to sixth inventions of the present application relate to a technique for forming a fine projection structure suitable for electron emission on the surface of the cold cathode in the method according to the first invention of the present application.

(2) In the manufacturing method according to the second aspect of the present invention, a fine projection structure suitable for electron emission can be obtained on the surface of the cold cathode by a unique method. That is,
A cold cathode is formed of a non-solid solution metal alloy composed of metal A and metal B, and the surface of this cold cathode is etched by an etching method in which the etching rates of metal A and metal B are different. In the non-solid solution metal alloy, the metal A and the metal B are not completely melted, so that the metal having a higher etching rate is removed by etching first. Thus, very fine protrusions (columnar uneven structure) can be obtained on the surface of the cold cathode.

(3) In the manufacturing method according to the third aspect of the present invention, the conductive layer forming the cold cathode is deposited by the oblique evaporation method. By performing oblique vapor deposition, columnar protrusions inclined with respect to the substrate surface can be formed, and electrons can be effectively emitted from the columnar protrusions.

(4) In the manufacturing method according to the fourth aspect of the present invention, since the cold cathode has a two-layer structure made of different metals, only the upper layer can be etched in a predetermined pattern. Therefore, this upper layer portion can be patterned into a protrusion structure suitable for electron emission.

(5) In the manufacturing method according to the fifth aspect of the present invention, since the surface of the cold cathode is patterned by the electron beam, any protrusion structure suitable for electron emission can be formed.

(6) In the manufacturing method according to the sixth aspect of the present invention, a crown-shaped projection structure suitable for electron emission is formed along the circumference of the upper surface of the cylindrical cold cathode. Since the extraction electrode has a circular opening that surrounds the crown-shaped projection structure from the periphery, uniform electron emission is possible.

[0019]

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.

On the other hand, the anode 7 and the phosphor layer 8 are formed on the lower surface of the other glass substrate 6. Anode 7
Is a transparent conductive film of ITO, ZnO: Al, etc.
The phosphor layer 8 is formed to a thickness of about 1.0 μm, and the phosphor layer 8 is made of a phosphor such as ZnO: Zn to have a thickness of 10 μm.
A layer of about m is formed. The structure formed on the upper surface of the glass substrate 1 is the electron-emitting device 10 to which the present invention is applied. On the other hand, the structure formed on the lower surface of the glass substrate 6 is, so to speak, also an electron accepting element 20, and is arranged so as to face the electron emitting element 10 as shown in FIG. The void is kept in a vacuum.

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.

Now, in manufacturing a vacuum micro device having such a structure, the most difficult process is to form the conical cold cathode 3 on the electron emitting device 10 side. 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, as shown in FIG. 2, a large number of such structures are arranged vertically and horizontally. Cold cathode 3
It is necessary to make the processing accuracy of (1) almost the same. If unevenness occurs in the processing accuracy of the plurality of cold cathodes 3 arranged vertically and horizontally,
The display screen becomes uneven. The present invention has been made in order to solve such a problem, and is a cross-sectional view of FIG. 3 and FIG. 4 (in these cross-sectional views, for convenience of explanation, only a structure for driving one pixel of the display is provided. , The actual dimensional ratio of each part is neglected and shown).
0 is produced.

First, as shown in FIG. 3A, a wiring layer 12 (ITO, Zn, ZnO) for a cold cathode is formed on a glass substrate 11.
O: a transparent conductive film such as Al, Al, Au, W, Mo,
A metal thin film of Ti, Ta, Nb, Cr or the like) is formed.
Then, as shown in FIG. 3 (b), on the wiring layer 12, an insulating layer 13 (SiO ₂ , Al ₂ O _5, etc.) and an electrode layer 14 (Al, Au, W, Mo, Ti, Ta) are formed. , Nb). Then, a resist layer 15 is formed on the electrode layer 14, and the resist layer 15 is formed.
Is patterned by photolithography or the like as shown in FIG. That is, the resist layer 15
The opening 15a is formed in a part of the area, and a part of the electrode layer 14 is exposed. The opening 15a is provided in the region where the cold cathode is to be formed. Therefore, if a columnar cold cathode is formed, the opening 15a becomes a circular window, and if a square column cold cathode is formed, the opening 15a becomes a square window. Then, etching is performed using the patterned resist layer 15 as a mask to form the electrode layer 1
4 and a part of the insulating layer 13 thereunder are removed.
As a result, as shown in FIG. 3 (d), the insulating layer 13a and the extraction electrode 14a are formed. Insulating layer 13a
The extraction electrode 14a and the extraction electrode 14a each have a shape surrounding a cold cathode that will be formed later. When the insulating layer 13 is etched, a little over-etching is performed, and as shown in FIG. 3 (d), the insulating layer 13a
It is preferable that a slight depression be formed on the side surface of the.

Next, on the entire surface of the substrate, a metal (W, Mo, Ti, Ta, Nb, Au, Ag, which is easy to emit electrons, and has excellent heat resistance and corrosion resistance, which later constitutes a cold cathode, is formed. C
A metal such as u is preferable), and electrode layers 16a and 16b are formed as shown in FIG. 4 (a). Here, the electrode layer 16b is a layer deposited in the hole (cold cathode formation region) formed by the etching in the previous stage, and the electrode layer 16a
Is a layer deposited in other regions. The thickness of these electrode layers 16a and 16b is preferably equal to or smaller than the sum of the thickness of the insulating layer 13a and the thickness of the extraction electrode 14a. Then, the resist layer 1
5 is peeled off from the upper surface of the extraction electrode 14a, the unnecessary electrode layer 16 is formed together with the resist layer 15 as shown in FIG. 4 (b).
a can be removed. The remaining electrode layer 16b constitutes a cold cathode, but is in contact with the extraction electrode 14a in this state. Therefore, as shown in FIG. 4C, the resist layer 17 is formed on the upper surface of the remaining electrode layer 16b.
To form. The resist layer 17 is formed in a region slightly smaller than the cold cathode formation region (region corresponding to the upper surface of the electrode layer 16b). In other words, the resist layer 17 may be formed so that only a part of the periphery of the electrode layer 16b can be etched. Then, when the side portions of the electrode layer 16b are removed by etching using the resist layer 17 as a mask, as shown in FIG. 4 (d), the cold cathode 16c is removed.
Can be formed. A predetermined distance is maintained between the cold cathode 16c and the extraction electrode 14a surrounding the cold cathode 16c.

Through the above steps, the electron-emitting device 10 shown in FIG. 1 can be manufactured. This step can be easily performed by using the technique of a general semiconductor device manufacturing process, and it is not necessary to perform particularly difficult fine processing. By the way, the cold cathode 3 in the element shown in FIG. 1 has a conical shape, and has a structure in which electrons are emitted from the protruding portion at the tip. Generally, a protrusion structure is required on the surface in order to efficiently emit electrons. For this reason, it is preferable that the cold cathode 16c manufactured by the above process also has a shape having a protruding structure. Therefore, the cold cathode 16c preferably has a prismatic shape as shown in FIG. 5 (a) rather than a cylindrical shape, and more preferably has a star shape as shown in FIG. 5 (b). As described above, the cold cathode 1
In the step of finally forming 6c, etching using the resist layer 17 is performed as shown in FIG. Therefore, by patterning the resist layer 17 into a desired shape, the cold cathode 16c having a desired shape can be obtained.

In order to obtain a fine projection structure on the cold cathode, it is possible to carry out the following method. That is,
As the material of the cold cathode 16c, a non-solid solution metal alloy material is used instead of the above-mentioned metal. Generally known alloys are obtained by mixing two kinds of metals in a liquid phase state at high temperature and then cooling them. At this time, the two kinds of metals are mixed at an arbitrary or predetermined ratio to form an alloy in the form of a substitutional solid solution in which the atoms on the lattice are exchanged or an interstitial solid solution in which the other atom penetrates into one lattice. To do. However, the mutual solubility of certain metals is extremely low, and even in the liquid phase, they separate like water and oil, and even when they are gradually cooled, the stable phase remains in a two-phase separated state. As it cools, no alloy can be obtained. Such metals are "non-solid solution metal type"
It is called. However, an alloy can be obtained by using a vapor-phase quenching method in which two types of such non-solid-solution metal-based metals are mixed in a vapor phase state and rapidly cooled. Such alloys are called non-solid solution metal alloys.

If the cold cathode 16c is formed of such a non-solid solution metal alloy, the cold cathode is made use of the difference in etching rate between two kinds of metals forming the non-solid solution metal system. By etching the surface of 16c, a large number of columnar protrusions suitable for electron emission can be formed on the surface of the cold cathode. Specifically, 2 called Co-Cr
Cold cathode made of non-solid-solution metal alloy consisting of one kind of metal 1
By forming 6c and etching with a ceric ammonium nitrate solution having different etching rates between Co and Cr, a large number of columnar protrusions suitable for electron emission can be formed. This is because in the alloy, Cr having a high etching rate was first removed by etching and remained C.
This is probably because the atoms of o are columnar. If this method is used, electrons will be emitted from a large number of columnar projections formed on the surface, so that the overall shape of the cold cathode 16c may be cylindrical.

Another method for obtaining a fine projection structure on the cold cathode is to form the cold cathode 16c by using the oblique evaporation method. That is, when the structure shown in FIG. 3 (d) is obtained on the glass substrate 11, this structure is placed in a vacuum chamber and the electrode layers 16a and 16b shown in FIG. 4 (a) are formed by metal deposition. is there. Moreover, at this time, the glass substrate 11 is tilted and fixed in the chamber so that oblique vapor deposition is performed. When such oblique vapor deposition is performed, since the metal atoms are obliquely deposited, a columnar structure that extends obliquely can be obtained. As a result, the electrode layer 1
A fine concavo-convex structure can be obtained on the upper surfaces of 6a and 16b, and as a result, this fine concavo-convex structure remains on the upper surface of the cold cathode 16c. Electrons are effectively emitted from this fine uneven structure.

It is also possible to form a protrusion structure by performing predetermined patterning on the upper surface of the cold cathode 16c. When patterning the upper surface of the cold cathode 16c by etching, as shown in FIG. 6 (a), the cold cathode 16c is formed on the first metal layer 18a.
The second metal layer 18b and the second metal layer 18b have a two-layer structure made of different metals, and only the second metal layer 18b is etched in a predetermined pattern by an etching method having different etching rates between these metals (a photolithography method may be used. ), As shown in FIG. 6B, what is called a ridge-shaped columnar protrusion 18c may be formed. Since the first metal layer 18a is not etched, the etching is performed on the second metal layer 18a.
It stops at the depth of b, and columnar protrusions 18c having a height convenient for electron emission are formed.

When it is desired to form finer projections on the cold cathode 16c, it is possible to perform patterning with an electron beam instead of performing the etching using the photolithography method as described above. That is, FIG. 4 (d)
As described above, after the cold cathode 16c is formed, the upper surface of the cold cathode 16c is irradiated with an electron beam to be partially shaved to form a fine projection structure. The electron beam can be aligned with extremely high precision, and finer patterning is possible as compared with etching.

The structure of a cold cathode capable of more stable electron emission is shown in FIG. This cold cathode 19 has a cylindrical shape,
Moreover, many columnar projections 19a suitable for electron emission are formed along the circumference of the upper surface. Such a structure
It can be obtained by the above-mentioned etching method or a patterning method using an electron beam. The extraction electrode 14a has a shape that surrounds the columnar cold cathode 19 in an annular shape, as shown by the alternate long and short dash line in the figure. The inner peripheral portion has a concentric relationship. In such a structure, since the distance between the columnar protrusion 19a and the extraction electrode 14a is equal at all positions, uniform and stable electron emission from each columnar protrusion 19a becomes possible with a relatively low voltage.

The present invention has been described above based on the illustrated embodiments, but the present invention is not limited to these embodiments, and can be implemented in various modes other than this. In particular, in the above-described embodiment, for convenience, the description has been given based on the cross-sectional view of the case where one set of electron-emitting devices is manufactured on the glass substrate. However, in reality, such electron-emitting devices are formed on the glass substrate. Many will be arranged vertically and horizontally. In this case, the distance between the adjacent electron-emitting devices is 1.0 μm to
The diameter of the extraction electrode portion of each electron-emitting device is preferably about 1.0 μm to 10 μm. Further, these dimensions may be appropriately changed depending on the shape of the electron-emitting device. Further, in the above-mentioned embodiment, the example in which the present invention is applied to the manufacture of the vacuum micro device for driving the flat panel display is shown, but the present invention is also applied to the manufacture of the vacuum micro device used for the switching device, the sensor device, etc. The invention is applicable as well. Furthermore, the present invention can be applied not only to vacuum micro devices but also to cold cathodes used for other devices. For example, SEM
The present invention can be applied to the case of manufacturing an electron gun of (scanning electron microscope).

[0033]

As described above, according to the method for manufacturing an electron-emitting device according to the present invention, the cold cathode is formed by depositing a conductive material in the holes opened in the insulating layer and the extraction electrode layer. Therefore, it becomes possible to manufacture an electron-emitting device capable of stable electron emission.

[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 perspective view showing a state in which vacuum micro devices having the structure shown in FIG. 1 are arranged on a plane.

FIG. 3 is a cross-sectional view showing a step of a pre-stage of a method for manufacturing an electron-emitting device according to the present invention.

FIG. 4 is a cross-sectional view showing a step in a later stage of the method for manufacturing the electron-emitting device according to the present invention.

FIG. 5 is a perspective view showing the shape of a cold cathode of an electron-emitting device manufactured by the method according to the present invention.

FIG. 6 is a diagram showing one method of forming columnar protrusions on the cold cathode in the method of manufacturing the electron-emitting device according to the present invention.

FIG. 7 is a perspective view showing a preferable shape of a cold cathode in an electron-emitting device manufactured by the method according to the present invention.

[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 ... Cold cathode 10 ... Electron emitting element 11 ... Glass substrate 12 ... Wiring layer 13 , 13a ... Insulating layer 14 ... Electrode layer 14a ... Extraction electrode 15 ... Resist layer 15a ... Openings 16a, 16b ... Electrode layer 16c ... Cold cathode 17 ... Resist layer 18a ... First metal layer 18b ... Second metal layer 18c ... Columnar shape Protrusion 19 ... Cold cathode 19a ... Columnar protrusion

Claims (6)

[Claims] 1. A method for 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 to the anode, wherein wiring to the cold cathode is provided on a substrate. Forming a first conductive layer for performing, forming an insulating layer on the first conductive layer, and forming a second conductive layer for forming a lead electrode on the insulating layer; Forming a first resist layer on the second conductive layer and providing an opening at a position corresponding to the cold cathode forming region of the resist layer;
Using the resist layer as a mask to etch away a part of the second conductive layer and a part of the insulating layer, and deposit a third conductive layer for forming a cold cathode on the entire surface of the substrate. Removing the first resist layer from the second conductive layer to remove a portion of the third conductive layer other than the cold cathode forming region, and the third remaining unremoved portion. Forming a second resist layer on a region smaller than the cold cathode forming region on the upper surface of the conductive layer, and using the second resist layer as a mask to remove the side portion of the third conductive layer by etching. And a step of: forming an electron-emitting device by using the remaining second conductive layer as an extraction electrode and the remaining third conductive layer as a cold cathode. . 2. The method according to claim 1, wherein the third conductive layer is formed of a non-solid solution metal-based alloy, and the metal used as the material of the alloy has different etching rates. The step of etching the surface of the third conductive layer to form a projection structure suitable for electron emission on the surface of the cold cathode composed of the third conductive layer. Production method. 3. The method according to claim 1, wherein a third conductive layer is deposited by an oblique evaporation method, and a projection structure suitable for electron emission is formed on the surface of the cold cathode formed of the third conductive layer. A method for manufacturing an electron-emitting device, characterized in that: 4. The method according to claim 1, wherein the third conductive layer has a two-layer structure made of different metals, and an etching method in which the etching rates are different between the metals is used. A method for manufacturing an electron-emitting device, further comprising the step of etching only the upper layer in a predetermined pattern to form a protrusion structure suitable for electron emission by the upper layer portion. 5. The method according to claim 1, further comprising the step of irradiating the surface of the formed cold cathode with an electron beam to perform patterning to form a protrusion structure suitable for electron emission. And a method for manufacturing an electron-emitting device. 6. The method according to claim 1, wherein a cold cathode forming region is formed into a circular shape to form a cylindrical cold cathode, and electron emission is performed along a circumference of an upper surface of the cylindrical cold cathode. A method of manufacturing an electron-emitting device, further comprising a patterning step for forming a suitable protrusion structure.