JP2000315453A - Emitter for field emission negative electrode and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the correspondence to large screen and easily manufacture an emitter by forming a negative electrode material mainly made of carbon adhered to a prescribed position on a substrate from isotropic carbon micro powder. SOLUTION: A negative electrode substrate 1 is made of glass or the like, the negative electrode substrate is micro powder 3 mainly made of carbon of isotropic carbon serving as an emitter for emitting electrons, and an adhesive 2 is ITO ink. The emitter can be easily formed in two processes that the adhesive 2 is applied to a position where the emitter is formed on the negative electrode substrate 1 and then the micro powder 3 is applied and adhered onto the adhesive 2. An insulating film such as SiO2 is formed on this structure, a gate electrode film is formed on it, then the tip part of the gate electrode film over the micro powder 3 is removed to expose the insulating film, and a part of the insulating film is removed to expose a part of the tip part of the micro powder 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emitter for a field emission cathode and a method for manufacturing the same, and more particularly, to a micro vacuum tube, a microwave device, an ultra-high speed operation device, a radiation environment (space, nuclear reactor, etc.) and a high temperature environment. The present invention relates to an emitter used as a field emission cathode, which is one of micro cold cathodes applied to a display element or the like, and a method for manufacturing the same.

[0002]

2. Description of the Related Art A device using a field emission cathode has a higher electron mobility than a semiconductor device, and can operate at high speed, at a high temperature,
Resistant to radiation damage. Therefore, they are being used today as display elements that require high luminance and low power consumption.

FIG. 11 is a perspective view showing the structure of a part of a conventionally used field emission cathode. The field emission cathode includes an emitter tip 101 having a sharp tip, an emitter electrode 102 for applying a negative voltage to the emitter tip, and a gate electrode 103 for extracting electrons. FIG.
As shown in the figure, the emitter tip 101 and the gate electrode 1
When a voltage is applied between the emitter tip and the emitter tip 02, a large electric field is applied to the tip of the emitter tip, and electron emission occurs.

FIG. 12 shows a schematic configuration diagram of a display device using a conventional field emission cathode. In the cathode plate 109, a stripe-shaped emitter electrode 102 is formed on a glass substrate 105, and the emitter electrode 102 is formed via an insulating layer 104.
The gate electrode 103 is formed in a direction perpendicular to the direction. A micro cathode array (FEA) including a plurality of field emission cathodes is formed in a pixel 106 at an intersection of the emitter electrode 102 and the gate electrode 103. Three kinds of phosphors 1 of red (R), green (G), and blue (B) are provided on the surface of the upper anode substrate 107.
08 is formed, and the emitted electrons emitted from the field emission cathode strike the phosphor 108 to emit light.

For such a field emission cathode, a manufacturing method developed by Spindt et al. Is generally used. FIG. 13 shows a manufacturing process diagram of a field emission cathode (cathode plate) developed by Spindt et al. First, in 1) of FIG. 13, an emitter feed film 117 is formed on an insulating substrate 116 such as glass.
In 2), patterning is performed to form an emitter electrode 102. Thereafter, in 3), an insulating film 118 and a gate power supply film 119 are formed in this order by plasma CVD or the like. In 4), the gate power supply film 119 and the insulating film 118 are respectively etched by using a circular gate opening resist pattern to form a cylindrical gate opening 120 having a diameter of about 1 μm.

[0006] Next, in 5), a sacrificial layer material such as aluminum is vapor-deposited on the insulating substrate 116 obliquely so as not to adhere to the emitter feed film 117 in the gate opening 120. The layer film 121 is formed. Further, in step 6), an emitter metal material 122 such as molybdenum is vertically deposited on the insulating substrate 116. At this time, as time elapses, the gate opening 120 gradually closes due to the deposition of the metal material for the emitter. 101 are formed.

Next, in step (7), the sacrificial layer film 121 is selectively dissolved with a phosphoric acid aqueous solution or the like to form an emitter tip 10.
The emitter metal material 122 other than 1 is removed. Finally, as shown in FIG. 8), if the gate power supply film 119 is patterned into a desired shape, a minute field emission cathode is completed.

However, when manufacturing a field emission cathode for a large screen, there are problems in the formation of the fine gate opening 120 in step 4) and the deposition of the metal material for the emitter in step 6). There is. First, the gate opening 120
Is a fine circular pattern having a diameter of about 1 μm, so it is very difficult to perform exposure so as to maintain a predetermined positional accuracy when forming a cathode for a large screen.

Further, the metal material for the emitter needs to be deposited almost perpendicularly to the substrate. However, when a cathode for a large screen is formed, a large deposition device is required. In general,
In order to perform this deposition accurately over the entire substrate,
The substrate is limited to a size of about 10 inches. Furthermore, since this vapor deposition step is performed, it is not possible to form a plurality of glass substrates from a large size.

Therefore, in order to form a field emission cathode for a large screen, there is a demand for a simpler manufacturing method and a cathode material which can be easily formed. By the way, carbon-based materials such as diamond and carbon nanotubes have recently attracted attention as cathode materials. Carbon-based materials can be formed at low cost because the main raw material is composed of carbon,
In addition, there is a feature that a gas does not easily adhere to the surface.

The present invention has been made in view of the above circumstances, and provides an emitter using a cathode material mainly composed of isotropic carbon, and is capable of responding to a large screen. Therefore, an object of the present invention is to provide a method of manufacturing an emitter which is easier than before.

[0012]

SUMMARY OF THE INVENTION The present invention comprises a substrate and a cathode material mainly composed of carbon fixed at a predetermined position on the substrate, wherein the cathode material is made of fine particles of isotropic carbon. It is intended to provide a field emission cathode emitter characterized by being powder. Here, the cathode material is
You may make it adhere to a board | substrate via an adhesive layer.
Thus, it is possible to provide a field emission cathode emitter which can be used for a large-screen display device and is easily manufactured.

In the present invention, glass, quartz or the like can be used for the substrate. Isotropic carbon can be used as the fine powder that is the source of the cathode material. The isotropic carbon refers to any fine powder of hardly graphitizable carbon such as hard carbon or glassy carbon, or isotropic high-density graphite. The fine powder as the cathode material preferably has a shape having fine projections, for example, a triangular pyramid shape, in order to obtain good electron emission characteristics. One unit of the fine powder has a size of about 1 to 150 μm. As the adhesive layer, ITO ink, resist, low-melting glass, or the like can be used. Further, the present invention provides a method for manufacturing an emitter of a field emission cathode, wherein a cathode material made of fine powder mainly composed of carbon is fixed at a predetermined position on a substrate via an adhesive layer. Is what you do.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. Note that the present invention is not limited to this. FIG. 1 is a schematic view showing a method of forming one emitter which emits electrons, which is one unit constituting a field emission cathode in the present invention.

In FIG. 1, reference numeral 1 denotes a cathode substrate made of glass or the like, and reference numeral 3 denotes a cathode material, that is, a fine powder mainly composed of carbon of isotropic carbon serving as an emitter for emitting electrons (hereinafter, referred to as a cathode). Reference numeral 2 denotes an adhesive such as ITO ink. Here fine powder 3
Although shown in FIG. 1 as a spherical shape, the shape is not limited to this, and may be any shape that can emit electrons, and can be formed into various shapes such as a triangular pyramid. The case of forming a triangular pyramid will be described later.

By the way, isotropic carbon has an advantage that it is harder to absorb gas because it is denser than graphite. However, it is difficult to form an isotropic carbon material having such characteristics on a cathode substrate. That is, the non-graphitizable material, which is one of the isotropic carbon materials, is usually formed by baking a thermosetting resin such as a phenolic resin. It is necessary to expose to a high temperature of 1000 ° C or more.

For this reason, it is impossible to raise the temperature to 1000 ° C. or higher even after the emitter is formed in a phenol resin state on a glass or other substrate in advance. It is difficult to obtain a predetermined characteristic. Also, when the substrate is formed by the thermosetting resin itself, it is necessary to use a 10
The substrate is deformed due to the high temperature of 00 ° C. or higher, and there is a problem in flat panel formation. The emitter forming method of the present invention described below solves such a problem.

Basically, the emitter is first connected to the cathode substrate 1.
The adhesive 2 is applied to the upper position where the emitter is to be formed (FIG. 1 (1): adhesive application step), and then the fine powder 3 is applied on the adhesive 2 and adhered (FIG. 1 (2) 2)
It can be easily formed by one process. Easy formation,
In order to increase the adhesion of the fine powder to the substrate, for example, a forming method as described in Examples below is used.

FIG. 2 shows a manufacturing process diagram of a field emission type electron source using the emitter shown in FIG. First, a fine powder 3 mainly composed of isotropic carbon is bonded onto a glass substrate 1 via an adhesive 2 by a method similar to the method shown in FIG. 1 (FIG. 2A: emitter). Formation). At this time, a plurality of fine powders 3 are formed in a concentrated manner in a region to be a pixel formed in a matrix on the glass substrate 1.

Next, an insulating film 4 such as SiO ₂ is formed on the above structure by a plasma CVD method or a spin coating method such as SOG (FIG. 2 (2): formation of insulating film). The insulating film 4 may be formed over the entire substrate surface so as to cover the fine powder 3. Further, a gate electrode film 5 is formed on the above structure by a method such as vapor deposition (FIG. 2C).
Formation of gate electrode). Here, for the gate electrode film 5, for example, a material such as copper or nickel is used.

Next, the gate electrode film 5 above the fine powder 3 is etched back by CMP or resist.
2 is removed to partially expose the insulating film 4 (FIG. 2).
(4): Removal of the tip of the gate electrode film). A part of the exposed insulating film 4 is removed by a method such as RIE or hydrofluoric acid etching to expose a part of the tip of the fine powder 3 as shown in FIG. 2 (5) (FIG. 2 (5): insulating film). Removal).

As described above, the tip portion of the fine powder partially exposed is the emitter tip 1 shown in FIG.
As in the case of 01, an emitter for emitting electrons can be obtained, and a field emission type electron source having a triode structure can be manufactured.

Next, a detailed example of a method of bonding fine powder mainly composed of isotropic carbon to a glass substrate will be described. FIG. 3 shows a process chart of the first embodiment of the bonding method. First, a conductive adhesive layer 2 having a thickness of about 500 nm is formed on the entire surface of the glass substrate 1 (FIG. 3).
(1)). For example, the glass substrate 1 is formed by printing or spin-coating ITO ink to be the adhesive layer 2.
And then in a nitrogen atmosphere (90 ° C, 4 minutes)
And dry.

Next, a solution 4 obtained by mixing fine powder 3 mainly composed of carbon of isotropic carbon with an organic solvent such as acetone is prepared.
The entire surface of the adhesive layer 2 is applied by spin coating or the like (FIG. 3B). Thereafter, it is dried and baked in a nitrogen atmosphere at a temperature of about 400 ° C. to blow off the resin component of the adhesive layer 2 and fix the fine powder 3 on the surface of the adhesive layer 2 (FIG. 3C). Next, patterning is performed using a resist so as to leave the adhesive layer 2 in the region to be a pixel and the fine powder 3 fixed thereto, and the ITO film as the adhesive layer 2 is etched with hydrobromic acid or the like ( FIG. 3 (4)). As described above, an emitter for emitting electrons can be formed.

FIG. 4 shows a process chart of a second embodiment of the method for bonding fine powder according to the present invention. First, a fine powder 3 mainly composed of carbon is mixed with a conductive adhesive 2 such as an ITO ink to prepare a paste. Then, this paste is applied onto the glass substrate 1 by a method such as printing or spin coating (FIG. 4A).

Next, after drying the above structure, it is baked at a temperature of about 400 ° C. in a nitrogen atmosphere to remove the resin component contained in the ITO ink, and furthermore, the ITO film is etched back with hydrobromic acid or the like. (FIG. 4B). By this etch back, the tip of the fine powder 3 is exposed from the surface of the adhesive layer 2.

Thereafter, using a resist, patterning is performed so as to leave the fine powder 3 in a region to become a pixel, and the ITO film is etched (FIG. 4C). As a result, FIG.
An emitter having the same structure as in (4) can be formed. According to the second embodiment, it is necessary to prepare a paste in which fine powder is mixed in advance, but the coating process on the glass substrate 1 only needs to be performed once, and the process can be rationalized.

FIG. 5 shows a process chart of a third embodiment of the method for bonding fine powder according to the present invention. First, on a glass substrate 1, C
A metal such as u is formed in a predetermined shape by vapor deposition or the like to form an emitter electrode line (FIG. 5A). Next, a solution in which the fine powder 3 mainly composed of carbon is mixed with a volatile organic solvent such as acetone is applied to the entire surface of the emitter electrode line 6 and the glass substrate 1 by spin coating or the like (FIG. 5).
(2)). Further, the adhesive 2 is applied on the above structure by spin coating or the like, and dried (FIG. 5C).

Further, the adhesive 2 is etched back by wet etching or dry etching until the tip of the fine powder 3 is exposed (FIG. 5).
(4)). Thereafter, through a patterning and etching process in the same manner as in the first embodiment, an emitter having a predetermined shape can be formed (FIG. 5 (5)). According to the third embodiment, the fine powder 3 mainly composed of isotropic carbon is used.
Is bonded directly to the emitter electrode line 6 and the glass substrate 1, and then the bonding layer 2 is formed. Therefore, the bonding agent 2 does not necessarily have to have conductivity. Can be used as

FIG. 6 shows a process chart of a fourth embodiment of the method for bonding fine powder according to the present invention. First, in order to form the power supply emitter electrode line 6 on the glass substrate 1, a metal such as Cu is formed in a predetermined shape by a method such as vapor deposition (FIG. 6).
(1)). Next, a solution in which the fine powder 3 mainly composed of carbon of isotropic carbon is mixed with a volatile organic solvent such as acetone is applied to the entire surface of the substrate including the emitter electrode lines 6 by spin coating or the like. (FIG. 6 (2)). Further, a photosensitive adhesive 7 is applied on the entire structure by a spin coating method or the like, and dried (FIG. 6C). As the photosensitive adhesive 7, for example, a resist is used.

Next, the back surface of the glass substrate 1, that is, FIG.
Exposure is performed from below the paper surface as shown in (4) (FIG.
(4)). Thereafter, when a developing process is performed, the adhesive 7 in the portion to which light is applied is removed, and only the structure of the portion of the emitter electrode line 6 remains (FIG. 6 (5)). During this development process,
The fine powder 3 applied directly on the substrate 1 is also removed. Next, the surface of the adhesive 7 is etched back by wet etching or dry etching to expose the tip of the fine powder 3 (FIG. 6 (6)).

As described above, together with the emitter electrode line,
An emitter composed of the fine powder 3 adhered thereon can be formed. According to the fourth embodiment, the fine powder 3 is exposed at the final stage of the manufacturing process (FIG. 6 (6)), so that the contamination of the surface of the portion emitting electrons is minimized, and more stable. Electron emission characteristics can be realized.

FIG. 7 shows a process chart of a fifth embodiment of the method for bonding fine powder according to the present invention. First, a glass layer 8 having a melting point of 600 ° C. or lower, which is sufficiently lower than that of the glass substrate, is formed on the entire surface of the glass substrate 1 (FIG. 7A). Next, a solution obtained by mixing the fine powder 3 mainly composed of isotropic carbon with a volatile organic solvent such as acetone is applied by spin coating or the like (FIG. 7 (2)). The substrate of the above structure is
Baking at 0 ° C. to melt the low melting point glass layer 8
Is fixed (FIG. 7 (3)). Further, in order to obtain conductivity, a conductive layer 9 serving as an emitter electrode line is formed on the entire upper surface of the above structure by evaporating a metal (such as Cu) (FIG. 7D).

Next, the surface of the conductive layer 9 is etched back by wet etching or dry etching to expose the tip of the fine powder 3 (FIG. 7 (5)).
Thereafter, by performing patterning using a resist so that an electrode pattern of a predetermined shape remains, an emitter of a predetermined shape can be formed (FIG. 7 (6)). According to the fifth embodiment, since the glass is used as the fixing layer instead of using the adhesive as in the other embodiments, the adhesion strength of the fine powder 3 to the substrate is increased, and a more stable electron is provided. Release characteristics are obtained.

FIG. 8 shows a process chart of a sixth embodiment of the method for bonding fine powder according to the present invention. First, a solution in which the fine powder 3 is mixed with a volatile organic solvent such as acetone is applied to the surface of the transfer material 10 by a spin coating method or the like, and dried (FIG. 8A). Silicon rubber or the like can be used as the transfer material 10. Next, a resist 11 is applied to the entire surface on the above structure so as to cover the fine powder 3 (FIG. 8B). Further, etch back is performed using wet etching or dry etching until the tip of the fine powder 3 is exposed (FIG. 8C).

Next, a conductive adhesive 2 such as ITO ink is applied to the entire surface on the above structure (FIG. 8 (4)). Further, the entire surface on the conductive adhesive 2 and the glass substrate 1 are bonded together, and the transfer material 10 is peeled off. That is, the structure including the resist 11, the fine powder 3, and the conductive adhesive 2 is transferred to the glass substrate 1 (FIG. 8 (5)). At this time, even if the size of each fine powder 3 is different, FIG.
On the surface of the resist 11 of (5), the transfer material 10
To the height of the fine powder 3 to the degree of flatness.

Thereafter, the substrate having the above structure is dried to fix the fine powder 3, and then the resist 11 is etched back by wet etching or dry etching so that the tip of the fine powder 3 is exposed. As described above, an emitter in which the height of the fine powder 3 exposed on the surface of the resist 11 is constant can be formed. According to the sixth embodiment, since the transfer process is performed after the application of the fine powder 3, even when the size and shape of each fine powder 3 are different,
The height of the portion of the fine powder 3 exposed from the surface of the resist 11 can be made uniform, and an emitter having more uniform electron emission characteristics can be obtained.

FIG. 9 shows a process chart of an embodiment for forming fine powder of non-graphitizable carbon in the isotropic carbon material of the present invention. 1 to 8 of the above embodiment.
Although the shape of the fine powder mainly composed of carbon of isotropic carbon has been described as a spherical shape for convenience, here, the process of forming the fine powder having a triangular pyramid shape will be described. Since the triangular pyramid-shaped fine powder having four vertices has sharp vertices, the voltage applied to the emitter electrode line can be reduced more stably as in the conventional emitter tip shape. Electrons can be emitted from the top.

The triangular pyramid-shaped fine powder can be formed as follows. First, a metal mold matrix 21 having a triangular pyramid-shaped recess having a predetermined size is prepared (FIG. 9).
(1)). The phenol resin 22 is filled so as to fill the recesses on the surface of the matrix 21 (FIG. 9B). Next, the squeegee is used to remove the resin
And is cured (FIG. 9 (3)). The cured triangular pyramid-shaped resin 22 is peeled off from the matrix 21 (FIG. 9).
(4)).

Further, when the triangular pyramid-shaped resin 22 is fired at a temperature of about 1000 to 3000 ° C., fine powder 23 mainly composed of non-graphitized carbon is formed.
(5)). When the resin component disappears by this baking, FIG.
As shown at 0, each vertex of the triangular pyramid-shaped fine powder 23 is sharpened further. In this way, the triangular pyramid-shaped fine powder 23 is formed, and the triangular pyramid-shaped fine powder 23 is applied to the glass substrate 1 by any of the methods described in FIGS. For example, the emitter of the present invention can be formed.

[0041]

According to the present invention, a fine field emission cathode emitter is formed using fine powder mainly composed of carbon of isotropic carbon, so that the field emission cathode can be formed more easily than before. Emitters can be created. In addition, according to the present invention, since a step of forming a minute opening and a step of depositing an emitter material are not required, a field emission cathode which can be used for a large-screen display device can be easily formed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a method for forming an emitter of the present invention.

FIG. 2 is a manufacturing process diagram of an electron emission type electron source using the emitter of the present invention.

FIG. 3 is a process chart of a first embodiment of a method for bonding fine powder according to the present invention.

FIG. 4 is a process chart of a second embodiment of the method for bonding fine powder according to the present invention.

FIG. 5 is a process chart of a third embodiment of the method for bonding fine powder according to the present invention.

FIG. 6 is a process chart of a fourth embodiment of the method for bonding fine powder according to the present invention.

FIG. 7 is a process chart of a fifth embodiment of the method for bonding fine powder according to the present invention.

FIG. 8 is a process chart of a sixth embodiment of the method for bonding fine powder according to the present invention.

FIG. 9 is a production process diagram of one embodiment of the fine powder mainly composed of isotropic carbon of the present invention.

FIG. 10 is an explanatory view of sharpening the apex of triangular pyramid-shaped fine powder of the present invention.

FIG. 11 is a perspective view of a partial structure of a field emission cathode.

FIG. 12 is a configuration diagram of a display device using a conventional field emission cathode.

FIG. 13 is a manufacturing process diagram of a conventionally used field emission cathode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cathode substrate 2 Adhesive (adhesive layer) 3 Fine powder mainly composed of carbon 4 Insulating film 5 Gate electrode film 6 Emitter electrode line 7 Adhesive 8 Low melting point glass layer 9 Conductive layer 10 Transfer material 11 Resist 21 Master mold 22 Phenol resin 23 Fine powder mainly composed of carbon

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tadashi Nakatani 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Fujitsu Limited

Claims (9)

[Claims] 1. A semiconductor device comprising: a substrate; and a conductive cathode material mainly composed of carbon fixed to a predetermined position on the substrate, wherein the cathode material is a fine powder of isotropic carbon. Characterized field emission cathode emitter. 2. The field emission cathode according to claim 1, wherein the cathode material is a fine powder which is made of a thermosetting resin in a predetermined shape in advance and is hardly graphitized by firing. Emitter. 3. The field emission cathode emitter according to claim 1, wherein the cathode material is fixed to a substrate via an adhesive layer. 4. The emitter of the field emission cathode according to claim 3, wherein the fine powder has a triangular pyramid shape. 5. An adhesive layer is formed on a substrate, a cathode material composed of fine powder of isotropic carbon is applied on the adhesive layer, and after firing at a predetermined temperature, the adhesive layer and the cathode material are removed. A method for manufacturing an emitter of a field emission cathode, wherein the emitter is patterned into a predetermined shape. 6. A method for applying a mixed solvent having a conductive and adhesive property, comprising a cathode material comprising fine powder of isotropic carbon, on a substrate, and drying and firing the mixed solvent,
A method of manufacturing an emitter of a field emission cathode, comprising exposing a part of the surface of the fine powder by etching and patterning a mixed solvent into a predetermined shape. 7. A volatile organic solvent containing a cathode material made of fine powder of isotropic carbon is applied on a substrate, and an adhesive layer is formed on the entire surface of the substrate. A method of manufacturing an emitter of a field emission cathode, comprising exposing a part of the surface and patterning the adhesive layer into a predetermined shape. 8. A low-melting-point glass layer is formed on a substrate, a volatile organic solvent containing a cathode material made of fine powder of isotropic carbon is applied to the entire surface of the low-melting-point glass layer, and baked. The low-melting glass layer is melted and the fine powder is fixed. Thereafter, a conductive layer is formed so as to cover the entirety of the low-melting glass layer, a part of the surface of the fine powder is exposed by etching, and the conductive layer is fixed. A method for manufacturing an emitter of a field emission cathode, which is patterned into a shape. 9. A method of applying a cathode material made of fine powder of isotropic carbon to a transfer matrix, forming a conductive adhesive layer on the entire surface of the structure, and bonding the adhesive layer to a substrate. And a method of manufacturing an emitter of a field emission cathode, wherein the transfer master is peeled off.