JPH06203748A - Manufacture of electron emitting cold cathode - Google Patents

Abstract

PURPOSE:To easily manufacture an electron emitting cold cathode having a surface structure suited for emitting an electron. CONSTITUTION:A vacuum microelement for performing action similar to a vacuum tube, by using a cold cathode 9 as the cathode, anode 7 as the anode and a draw out electrode 5 as the grid, is manufactured. The columnar cold cathode 9 is formed by rhombic evaporation of metal. By the rhombic evaporation, many fine columnar protrusions are formed in an upper surface of the cold cathode 9, and an electron is emitted from these columnar protrusions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cold cathode for electron emission, and more particularly to a method for producing a cold cathode for electron emission used in 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]

As described above, the vacuum micro device is, in principle, the same as a vacuum tube, but its size is so small that it is incomparable to that of a vacuum tube, and its manufacture is difficult. Requires advanced microfabrication technology. In particular, the cold cathode needs to be processed into a surface shape that easily emits electrons, and such fine processing is extremely difficult. Conventionally, as materials for this cold cathode, W, Ta, M
A refractory metal such as o is used, and the tip of the electron emitting portion is processed to have a radius of curvature of 1 μm or less, and a strong electric field of about 10 ⁷ V / cm is concentrated on this tip to emit electrons. However, the radius of curvature of this cold cathode tip is 1
In order to process to less than μm, a very advanced fine processing technology is required, and this cold cathode processing failure causes
The operation of the vacuum micro device may become unstable.

Therefore, an object of the present invention is to provide a method for easily producing a cold cathode for electron emission having a surface structure suitable for electron emission.

[0006]

The present invention provides a cold cathode used in an apparatus comprising a cold cathode, an extraction electrode, and an anode, and a device for extracting electrons from the cold cathode by the extraction electrode and discharging the electrons to the anode. In the method, a substrate on which a cold cathode is to be formed is fixed in a chamber in a state of being inclined at a predetermined angle with respect to a horizontal plane, a vapor deposition material is placed at a position deviating from a normal to the main surface of the substrate, and the vapor deposition is performed. The material is obliquely vapor-deposited on the substrate to form the electron emission surface of the cold cathode.

[0007]

[Operation] A substrate and a vapor deposition material are housed in a chamber that is evacuated, and the vapor deposition material is vaporized by heat or an electron beam to deposit the atoms of the vapor deposition material on the substrate. It has been used for a long time as a method for forming a metal layer and the like. At this time, a method of forming a deposition layer having an oblique structure on the substrate by tilting the substrate is also conventionally known as an oblique vapor deposition method.

The inventor of the present application has discovered that when metal is vapor-deposited by such an oblique vapor deposition method, very fine protrusions (columnar uneven structure) are obtained on the surface of the vapor deposition layer.
Moreover, it can be confirmed that the projections thus obtained have a structure suitable for emitting electrons as a cold cathode,
It was also confirmed that this cold cathode can be used for vacuum micro devices and the like.

[0009]

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 have a thickness of about 1.0 μm, and the phosphor layer 8 is formed of a phosphor such as ZnO: Zn to have a thickness of about 10 μm. As shown in FIG. 1, the structure formed on the upper surface of the glass substrate 1 and the structure formed on the lower surface of the glass substrate 6 are arranged so as to face each other.
The gap between the two is kept in a vacuum state.

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. 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 arrayed vertically and horizontally to improve the processing accuracy of each cold cathode 3. It is necessary to have almost the same precision. 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 has been made to solve such a problem, and a cold cathode is manufactured by the following method.

FIG. 2 is a sectional view of a vacuum micro device using a cold cathode to which the manufacturing method according to the present invention is applied. Figure 1
Similarly to the above, a cross section of a vacuum micro-element for driving a flat panel display is shown, and for convenience of explanation, only a structure for driving one pixel of the display is drawn ignoring the actual dimensional ratio of each part. . The structural difference from the device shown in FIG. 1 is the shape of the cold cathode 9. That is, the cold cathode 3 in FIG. 1 has a conical shape, whereas the cold cathode 9 in FIG. 2 has a cylindrical shape. Note that the shape of the insulating layer 4 is slightly changed due to this difference in shape (in the device of FIG. 1, the exposed surface of the insulating layer 4 is incidentally an inclined surface due to the step of forming the conical cold cathode 3). However, in the device of FIG. 2, such a process is unnecessary). The state in which the structures for one pixel shown in FIG. 2 are arranged vertically and horizontally is as shown in the perspective view of FIG. 3 (the wiring pattern of the extraction electrode 5 is not shown). Although it is difficult to form the cold cathode 3 having a conical shape with a sharp tip as shown in FIG. 1, it is easy to form the cylindrical cold cathode 9 shown in FIG. However, if the cold cathode 9 is a mere columnar electrode, the operating gate voltage for emitting electrons becomes considerably high. Therefore, in order to emit electrons from the cold cathode 9 at a low voltage, it is necessary to provide a physical protrusion. In the present invention, the projection for electron emission is formed on the upper surface of the cylindrical cold cathode 9 by the following oblique vapor deposition method.

FIG. 4 is a diagram showing a general method of oblique vapor deposition. When the substrate 11 is housed in the chamber 10 whose pressure is reduced by an exhaust system (for example, a vacuum pump) (not shown) and oblique vapor deposition is performed, the vapor deposition layer 12 is formed on the surface of the substrate 11. The feature of this oblique vapor deposition lies in that the substrate 11 is tilted from the horizontal plane by an angle θ and fixed to the holder 13. The material from which the vapor deposition layer 12 is formed is the crucible 1
4 is prepared as the vapor deposition material 15, but since the substrate 11 is inclined, the vapor deposition material 15 is placed at a position deviated from the normal line n to the main surface of the substrate 11. An electron gun 16 is provided below the crucible 14, and an electron deflection system (electromagnet or the like) (not shown) causes electrons emitted from the electron gun 16 to collide with the vapor deposition material 15 in the crucible 14. Due to this collision, atoms of the vapor deposition material 15 (atoms of iron Fe in this embodiment) jump out into the chamber 10 and deposit on the surface of the substrate 11. Thus, the vapor deposition layer 12 made of iron Fe is gradually formed on the surface of the substrate 11. What should be noted here is that when such oblique vapor deposition is performed, the vapor deposition layer 12 has an oblique structure.
Specifically, as shown in the cross-sectional view of FIG. 5, the vapor deposition layer 12 formed on the surface of the substrate 11 has a columnar structure inclined with respect to the main surface of the substrate 11. It is considered that this is because a shadow area is formed on the substrate 11 by the material previously deposited in the process of oblique deposition.

The inventor of the present application has discovered that if the cold cathode 9 is formed by such oblique vapor deposition, a large number of columnar projections suitable for electron emission are formed on the surface of the cold cathode 9. That is, a columnar cold cathode 9 as shown in FIG.
If the step of forming is carried out by the oblique evaporation method, a large number of fine columnar projections suitable for electron emission can be obtained on the upper surface of the cold cathode 9. Specifically, after the wiring layer 2 is formed on the glass substrate 1, the substrate 1 is tilted and fixed in the chamber as shown in FIG. The inclination angle θ is preferably set to 60 ° or more. Then, metal is obliquely vapor-deposited on the substrate 1 to a thickness of about 2 μm to form a vapor deposition layer. By patterning this vapor deposition layer based on a predetermined pattern, a cylindrical cold cathode 9 as shown in FIG. 2 can be obtained. Since the oblique deposition is performed, the cold cathode 9 has a columnar structure as shown in FIG. 5, and the uneven structure suitable for electron emission is formed on the surface. In addition, as the vapor deposition material forming the cold cathode 9, W, Mo, Ti, which is relatively easy to emit electrons, and has excellent heat resistance and corrosion resistance,
It is preferable to use a metal such as Ta, Nb, Au, Ag, Cu. After that, if the insulating layer 4 and the extraction electrode 5 are formed, the structure on the cathode side is completed. Such oblique deposition is
Since it can be performed uniformly on a plane as shown in FIG. 3, columnar protrusions are formed on the upper surfaces of the plurality of cold cathodes 9 almost uniformly, and the columnar protrusions are used as driving elements for a flat panel display. However, there is no unevenness on the screen.

However, the present invention is not limited to the application to the vacuum micro device having the structure shown in FIG. 2 or 3. FIG. 6 is a perspective view of the electron emission side (cold cathode side) of a vacuum micro device having another structure. The structure shown in FIG. 2 is called a vertical type, while the structure shown in FIG. 6 is called a horizontal type. A flat plate-shaped cold cathode 22 is formed on the substrate 20 via an insulating layer 21, and an extraction electrode 24 is formed via an insulating layer 23. The electrons are extracted from the electron emission end 22a of the cold cathode 22 on the extraction electrode 24 side and emitted to an anode (not shown).
In this horizontal type, the gap between the cold cathode 22 and the extraction electrode 24 can be made quite small, so that there is an advantage that electrons can be emitted at a lower voltage than in the vertical type. The present invention is also applicable to such a horizontal vacuum micro device. That is, the oblique vapor deposition described above may be performed on at least the surface of the electron emitting end 22a of the cold cathode 22 to form a large number of fine columnar projections.

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. For example, in the above-described embodiment, the example in which the oblique evaporation is performed by the EB evaporation in which electrons are made to collide with the evaporation material is shown, but thermal evaporation in which the evaporation material is heated by a heater may be used. Further, the shape of the cold cathode 9 is not limited to a cylindrical shape, and if a fine protrusion structure is formed on the surface,
The overall shape does not matter. For example, it is possible to form the conical cold cathode 9 by performing oblique vapor deposition while rotating the substrate.

[0018]

As described above, according to the method for manufacturing a cold cathode for electron emission according to the present invention, the cold cathode is formed by oblique vapor deposition. Therefore, the electron emission cold cathode having a surface structure suitable for electron emission is used. A cold cathode can be easily manufactured.

[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 cross-sectional view showing the structure of a vertical vacuum micro device manufactured by applying the present invention.

FIG. 3 is a perspective view showing a state in which vacuum micro elements having the structure shown in FIG. 2 are arranged on a plane.

FIG. 4 is a diagram showing a general method of oblique vapor deposition.

FIG. 5 is a diagram showing a structure of a vapor deposition layer formed by oblique vapor deposition.

FIG. 6 is a cross-sectional view showing a structure of a horizontal vacuum micro device manufactured by applying 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 ... Chamber 11 ... Substrate 12 ... Evaporation layer 13 ... Holder 14 ... Crucible 15 ... Vapor deposition material 16 ... Electron gun 20 ... Substrate 21 ... Insulating layer 22 ... Cold cathode 22a ... Electron emission end 23 ... Insulating layer 24 ... Extraction electrode

Claims (1)

[Claims] 1. A method for producing a cold cathode used in a device comprising a cold cathode, an extraction electrode, and an anode, wherein an electron is drawn from the cold cathode by the extraction electrode and emitted to the anode. The substrate to be fixed is fixed in the chamber at a predetermined angle with respect to the horizontal plane, the vapor deposition material is placed at a position deviating from the normal to the main surface of the substrate, and the vapor deposition material is obliquely placed on the substrate. A method of manufacturing a cold cathode for electron emission, comprising forming an electron emission surface of the cold cathode by vapor deposition.