JP2003242876A - Cathode part for electron emission and fluorescent display device including the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cathode part for electron emission which can be easily manufactured at a low cost, discharge sufficient amount of electrons per unit area at low electric fields, and favorably used in a fluorescent display device or the like. <P>SOLUTION: The cathode part for electron emission which can emit electrons by applying the electric field includes a group III nitride layer (12) deposited on an electrode (11) by a vapor phase deposition method. This nitride layer reflects an uneven condition of the surface of deposition, and has an uneven surface suitable for electron emission. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode part capable of emitting electrons by applying an electric field. Such a cathode part can be preferably used in, for example, a full-color display panel that illuminates a fluorescent screen.

[0002]

2. Description of the Related Art FIG. 7 is a schematic sectional view showing an example of an electron emission cathode portion used in a fluorescent display device disclosed in Japanese Patent Laid-Open No. 2000-149765. In this electron emission cathode part, a large number of GaN crystal grains 103 are attached to an electrode (conductive plate) 101 with a conductive adhesive 102, and the size of these crystal grains is several tens to several hundreds μ.
Within the range of m. And those GaN crystal grains 10
3 acts as an emitter that emits electrons.

FIG. 8 is a schematic sectional view showing another example of the electron-emitting cathode portion disclosed in Japanese Patent Laid-Open No. 2000-149765 and its manufacturing process. That is, FIG. 8A shows a completed electron emitting cathode portion, and FIGS. 8B to 8D schematically illustrate a part of the manufacturing process thereof.

In manufacturing the cathode portion for electron emission,
As can be seen from FIG. 8A, a gallium nitride film 203 is grown on the sapphire substrate 202 as a buffer layer. Then, on the gallium nitride film 203, as shown in FIG.
As shown in (b), a silicon oxide film 204 including a plurality of regularly arranged openings is formed. Each of the openings has a diameter of, for example, about 5 μm.

As shown in FIG. 8C, a hexagonal pyramidal gallium nitride crystal 205 is grown on the gallium nitride film 203 exposed in the opening by using the silicon oxide film 204 as a selective growth mask. To be And FIG.
As shown in (d), the silicon oxide film 204 is selectively removed.

As shown in FIG. 8A, a sapphire substrate 202 supporting an emitter made of a hexagonal pyramidal gallium nitride crystal 205 is provided on an electrode 201. Since the sapphire substrate 202 is an insulator, Electrode 201
The gallium nitride film 203 and the gallium nitride film 203 are electrically interconnected via a conductive member 206 made of a conductive paste or the like.

Further, in Japanese Patent Laid-Open No. 2000-260299, although the emitter is made of polycrystalline silicon by using etching, it is said that the emitter may be made of polycrystalline gallium nitride.

Further, in Japanese Patent Laid-Open No. 2000-67737,
Disclosed is a technique for coating the surface of a cone-shaped emitter such as Mo or the flat surface of a flat emitter, which is produced by utilizing the rotary oblique deposition, with a specific material. The specific coating material is capable of emitting electrons in a low electric field, such as GaN or A
1N and the like are listed. In this case, after forming an emitter such as Mo and a gate electrode on the substrate, a coating layer capable of emitting electrons in a low electric field is entirely deposited.

Furthermore, Applied Physics Letters, V
ol.78, 2001, p.3229, the electron emission characteristics of the surface of a single-crystal GaN film formed on a sapphire substrate, which is made uneven by plasma treatment, are reported. As an example of 1.2 × 10 ⁴
/ Cm and 6.1 x 10 ³ / cm have been reported.

[0010]

In the cathode part for electron emission as shown in FIG. 7, since the grain size of the GaN crystal grains 103 is several tens to several hundreds μm, which is very large, the tip of the emitter 103 is formed. Cannot have a sharp shape that easily emits electrons. Therefore, in order to obtain sufficient electron emission, it is necessary to apply a high electric field to the tip of the emitter 103, and due to the high voltage used for that purpose, the power consumption for electron emission increases. In addition, the conductive adhesive 1
02 is used, it is difficult to obtain a highly reliable cathode part for electron emission because the adhesive 102 is deteriorated by long-term energization.

On the other hand, in the electron emission cathode portion as shown in FIG. 8, after the SiO ₂ film 204 is once formed on the GaN buffer layer 203, GaN is again formed in the opening region where the film is partially removed. Since the crystal 205 is grown, it is difficult to obtain a good GaN crystal 205. Also,
The allowable range of crystal growth conditions for forming a hexagonal pyramidal GaN crystal only in the opening region of the SiO ₂ film 204 is very narrow. In practice, amorphous GaN particles are formed on the SiO ₂ film or on the side surface of the opening. Often, a film is formed. That is, it is very difficult to obtain the sharp hexagonal GaN crystal 205, and the sharp hexagonal GaN crystal 2 is obtained.
It is impossible to fabricate a large-area cathode portion for electron emission containing 05 evenly.

Further, due to the limitation of lithography when forming the opening of the SiO ₂ film 204, the hexagonal pyramidal GaN crystal 2 is used.
The area density of 05 is limited, and the electron emission amount per unit area of the electron emission region cannot be increased. Further, since the sapphire substrate 202 is expensive and a large-area sapphire substrate cannot be obtained, a large-area display panel cannot be manufactured using the sapphire substrate. Furthermore, since the sapphire substrate 202 is an insulator, the emitter 20
5, the electrical connection between the buffer layer 203 and the electrode 201 must be made through the conductive member 206, and such an electron emitting cathode portion is not suitable for use in a large area display panel.

On the other hand, in Japanese Patent Laid-Open No. 2000-260299,
A cone type emitter is manufactured by etching polycrystalline silicon. As the material of this cone type emitter,
It is said that gallium nitride or the like can be used instead of silicon, and polycrystal is preferable. However, a method for etching a polycrystalline gallium nitride to form a cone-type emitter is not generally known, and JP-A-2000-2000 is used.
Since the method is not taught even in -260299, its practical application is extremely difficult.

In Japanese Patent Laid-Open No. 2000-67737, a GaN coating layer or the like is formed on the surface of a cone type Mo emitter. Therefore, even if the tip of the underlying cone-type Mo emitter can be formed to be sharp to some extent, if the surface is covered with a GaN layer or the like, the tip becomes blunt and not sharp, so that electrons are emitted from the resulting emitter. It requires a high electric field.

When a GaN coating layer or the like is formed on a flat Mo emitter, GaN itself has a property of emitting electrons in a sufficiently low electric field, so that a sharp shape is unnecessary. However, although a flat GaN layer or the like can emit electrons even in a low electric field to some extent, it is not sufficient from the viewpoint of practical use as an emitter for a fluorescent display device or the like.

Furthermore, after the emitter and the gate electrode are formed, a material that emits electrons in a low electric field is entirely deposited, so that a short circuit may occur between the emitter and the gate electrode, resulting in a very low manufacturing yield. Become. In order to prevent such a short circuit, it has been proposed to add some processes, but such an additional process leads to an increase in the cost of the cathode part for electron emission.

In view of the problems of the prior art as described above, the present invention provides an electron emitting cathode portion which can be easily manufactured at low cost and which can emit a sufficient amount of electrons per unit area in a low electric field. It is intended to be provided. Such an electron-emitting cathode portion can be preferably used in, for example, a fluorescent display device.

[0018]

According to the present invention, an electron-emitting cathode portion capable of emitting electrons by applying an electric field has a group III nitride layer formed on an electrode by a vapor deposition method. This nitride layer is characterized in that it has an uneven surface suitable for electron emission, reflecting the deposited surface unevenness.

Examples of the vapor layer deposition method include MBE (Molecular Beam Epitaxy) method, CVD (Chemical Vapor Deposition) method, and HV.
PE (hydride vapor phase epitaxy) method, sputtering method,
Alternatively, an ion plating method or the like can be used.

Incidentally, the uneven surface suitable for electron emission, which reflects the surface unevenness of the vapor-phase deposited surface, means the uneven surface in the as-deposited state or even if the surface is etched. It means an uneven surface that reflects the uneven shape of the formed state.

In such an electron-emitting cathode portion according to the present invention, it is not necessary to form the base itself into a shape suitable for the emitter, unlike the prior art in which the base metal is processed into a cone shape, etc. In addition to the simple manufacturing process, the tip of the emitter is sharper than when the cone-type emitter is covered with a GaN layer or the like, and the applied electric field for electron emission can be reduced.

Further, the manufacturing of the cathode portion for electron emission of the present invention does not require an oxide film mask having a hexagonal opening as in JP-A-2000-149765. That is, due to the characteristics of the III-nitride crystal itself, the surface of the deposited layer naturally becomes uneven during vapor deposition, so the manufacturing process is simple, and a conventional mask is used for the tip of the projection that becomes the emitter. Is sharper than the tip of a GaN crystal grown into a hexagonal pyramid. As described above, in the electron emission cathode portion of the present invention, since the vapor-deposited group III nitride layer has an uneven surface shape suitable for an emitter as it is, it is extremely superior to the prior art. It is possible to inexpensively form an emitter having a sharp tip shape by a simple process.

Furthermore, since the group III nitride layer can be directly vapor-deposited on the metal electrode or the transparent conductor electrode, the process for forming the electrode later is not required, and the cathode for electron emission is further inexpensive. Parts can be provided.

The I of the cathode portion for electron emission according to the present invention is
The Group II nitride layer is preferably polycrystalline. This is because when the group III nitride layer is vapor-deposited as a polycrystalline film, its surface is likely to have an uneven shape and has a shape suitable for an emitter. The polycrystalline state of the vapor deposited III-nitride layer can be determined by a backscattered electron diffraction pattern or an X-ray diffraction pattern.

When a hexagonal pyramidal GaN single crystal is grown in the opening of an oxide film mask as in Japanese Patent Laid-Open No. 2000-149765, a single crystal substrate such as sapphire, which has been conventionally used, is required. Since the group III nitride layer can be directly vapor-deposited on a metal plate or a transparent conductive film without requiring a single crystal substrate, a large area can be easily obtained, and a large area field emission display. Suitable for emitters for.

The electrode of the cathode portion for electron emission according to the present invention is
It is preferably made of a polycrystalline metal or a polycrystalline transparent conductor. This is because, by using a polycrystal for the electrode, a group III nitride emitter layer having a sharper uneven surface can be vapor-deposited thereon. Further, it is needless to say that a polycrystalline material is much cheaper than a single crystal material and that a large area material can be easily obtained.

When the electrode is made of metal, Mo (molybdenum), Nb (niobium), Ta (tantalum), Ti
It is preferable to contain at least one selected from the group consisting of (titanium), Hf (hafnium), Zr (zirconium), and Al (aluminum). Because such an electrode can make good ohmic contact at the interface with the group III-nitride layer.

On the other hand, when the electrode is made of a transparent conductive oxide, zinc (Zn), indium (In), tin (S
It is preferable to include at least one selected from the group consisting of n), magnesium (Mg), cadmium (Cd), gallium (Ga), and lead (Pb). Also in this case, good ohmic contact can occur at the interface between the transparent conductive oxide electrode and the group III nitride layer. When a transparent body is used for the substrate of the transparent conductive oxide film electrode, III
Since the emitter layer of the group nitride is also transparent, it is possible to manufacture a display panel that takes out light from the substrate side.

The electron emission cathode portion may further include a gate electrode for limiting a region where electrons are emitted from the group III nitride layer. The electron-emitting cathode portion in which such a gate electrode is integrated can be more preferably used as an electron-emitting cathode portion for a fluorescent display panel, for example.

The average thickness of the group III nitride layer vapor-deposited is preferably 0.01 μm or more. This is because when the average thickness of the vapor-deposited III-nitride layer is less than 0.01 μm, the III-nitride layer does not sufficiently cover the electrode surface, and the protrusion suitable for the emitter is formed. This is because there is also a region in which is not formed.
In addition, when a commercially available metal substrate is used as the electrode, the surface roughness Ra (center line average roughness) is about 10 nm, so the thickness of the group III nitride layer vapor-deposited is 0.0
If it is less than 1 μm, the nitride layer is not formed on the entire surface of the metal electrode. Therefore, when using a metal substrate having a surface roughness of Ra of about 10 nm as an electrode,
It is necessary to deposit a group III nitride layer with a thickness of 0.01 μm or more, and a thickness of 0.1 μm or more is more preferable in order to form a sufficiently sharp projection suitable for an emitter.

A group III nitride layer having a thickness of several μm was deposited in order to find a preferable upper limit of the layer thickness.
Since there was no great difference as compared with the case of the thickness of about m, it is considered that the upper limit of the preferable layer thickness does not require special limitation. However, from the viewpoint of manufacturing cost, it is not preferable to make the film formation time too long for the deposition of the unnecessarily thick group III nitride layer. Therefore, in the case of the MBE (molecular beam epitaxy) method, the preferable upper limit of the film thickness is about 5 μm in consideration of the film forming time. However, CVD
When the deposition rate is increased by the (chemical vapor deposition) method, the HVPE (hydride vapor phase epitaxy) method, the sputtering method, the ion plating method or the like, a film thickness higher than this is possible.

The group III nitride layer is preferably an n-type semiconductor. Although AlN and the like are similar to insulators among group III nitrides, they have a negative electron affinity, so that electrons can be easily emitted into a vacuum even if they are not n-type. However, in the case of a group III nitride having a positive electron affinity,
It is preferably an n-type semiconductor. because,
In the case of having a positive electron affinity, a process in which an electron is excited into a conduction band and then emitted into a vacuum is considered, so that a sufficient number of electrons exist in a conductor from the beginning.
This is because the mold is preferable.

In order to make the group III nitride layer an n-type semiconductor, it is preferable to dope with Si. For example Ga
In the case of N or the like, a dopant is not always necessary because a considerable concentration of electrons are present in the conduction band even when undoped. However, by doping Si to increase the electron concentration, electrons can be emitted more easily in a low electric field. Further, AlN and the like have a negative electron affinity, but by doping Si at a high concentration, it is possible to easily emit electrons in a lower electric field.

As the group III nitride layer, Al _x Ga _{1-x is used.}
N (0 ≦ x ≦ 1) can be preferably used. By using the group III nitride having this composition, the crystal grains in the group III nitride layer vapor-deposited become small,
It is possible to form a sharp emitter and concentrate the electric field on the tip of the emitter. Therefore, in a device using such an electron emission cathode portion including a group III nitride layer, it is possible to obtain effects such as a reduction in driving voltage and a reduction in power consumption.

That is, the electron emitting cathode portion as described above can be preferably used in, for example, a fluorescent display device.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG. 1 is a schematic sectional view showing a manufacturing process of a cathode portion for electron emission according to Embodiment 1 of the present invention. That is, FIG. 1 (a) shows a process of manufacturing the cathode portion for electron emission, and FIG. 1 (b) shows the completed cathode portion for electron emission together with the anode portion oppositely arranged.

The cathode portion for electron emission of this embodiment is the substrate 1
1 and an emitter 12 provided thereon for emitting electrons. When the substrate 11 also serves as an electrode, it consists of a metal substrate or other conductor substrate, or a metal layer or transparent conductor layer deposited on a non-conductive substrate.

The emitter 12 is made of GaN polycrystal, which has a grain structure or a columnar crystal structure. The surface of the polycrystalline GaN layer 12 had an uneven shape, and the radius of curvature of the tip of the protrusion that could serve as an emitter was about 20 nm. The reflection electron beam diffraction pattern of the polycrystalline GaN layer 12 is usually ring-shaped. From the result of the X-ray diffraction pattern, it was found that the c-axis oriented polycrystalline GaN layer 12 was grown in many cases using the Mo substrate 11.

In the method of manufacturing the cathode portion for electron emission in FIG. 1, first, the Mo substrate 11 is mirror-polished to make the surface unevenness Ra about 10 nm. Then, the Mo substrate 11 is degreased for 5 minutes with acetone and for 5 minutes with ethanol, and then pickled with hydrochloric acid for 20 minutes. An ECR (electron cyclotron resonance) -MBE method is used to deposit the polycrystalline GaN layer 12. The Mo substrate 11 is introduced into the ultrahigh vacuum chamber and then thermally cleaned at 800 ° C. for 10 minutes. Next, the substrate temperature is lowered to 780 ° C., nitrogen atomic plasma is supplied from the ECR plasma cell, and gallium is supplied from the heated cell, so that the polycrystalline GaN layer 12 having an uneven surface is 0.5 μm thick. It is deposited on the Mo substrate 11 with an average thickness.

In-situ observation of backscattered electron beam diffraction during the growth of the polycrystalline GaN film showed a ring-shaped pattern at the initial stage of its growth, but gradually changed into a discontinuous ring-shaped pattern with the growth. This means the growth of polycrystals. The diffraction pattern did not change even when the incident direction of the electron beam was changed.

According to AFM (Atomic Force Microscope) observation, the crystal grains in the polycrystalline GaN film were hexagonal, and the grain size was about 400 nm. These crystal grains caused a protrusion that could serve as an emitter on the surface of the film, and the radius of curvature of the tip was about 20 nm. The average number density of the convex portions that can be the emitters is about 1 per cm ^2.
It was ⁰⁹ .

A state in which the emitter layer 12 is vapor-deposited on the Mo substrate 11 as described above is shown in a schematic sectional view of FIG.

In the case of the crystal growth method using nitrogen atom plasma described above, the substrate temperature is preferably 400 ° C. or higher and 1100 ° C. or lower. Because the substrate temperature is 400 ℃
This is because the polycrystalline group III nitride layer 12 hardly grows when the temperature is below, and the surface of the Mo substrate 11 becomes rough when the substrate temperature is 1100 ° C. or higher.

Although the ECR-MBE method was used in this example, a similar polycrystalline GaN layer could be grown by using the ammonia MBE method. Besides this,
The CVD method, the HVPE method, the sputtering method, and the ion plating method can be used, and when these methods are used, the above substrate temperature is not limited. This also applies to the other embodiments.

Although only the polycrystalline GaN layer is grown as the emitter layer in this embodiment, it may have a multi-layer structure in which the polycrystalline GaN layer and the polycrystalline AlGaN layer are combined. This also applies to the other embodiments.

After that, the thickness to become the insulating film 13 is 0.3.
A μm SiO ₂ film is formed on the entire surface of the polycrystalline GaN layer 12, and a Mo film to be the gate electrode 14 is formed on the entire surface of the SiO ₂ film. Next, a photoresist (not shown) is applied on the Mo film 14 and patterned according to the layout of the region where the polycrystalline GaN layer 12 should act as an emitter, and the Mo film 14 is formed in the region not covered with the photoresist. And the SiO ₂ film 13 are removed by etching to partially expose the polycrystalline GaN layer 12.

Thus, on the Mo substrate 11, the emitter made of the polycrystalline GaN layer 12 having a plurality of convex portions and the gate electrode 14 surrounding the emitter are formed.

As shown in FIG. 1 (b), the obtained cathode portion for electron emission is arranged with the anode portion opposed to each other in vacuum to apply an electric field, so that electrons are emitted from the emitter region 12. Can be released. That is, FIG.
In (b), the positive electrode 1 formed on the anode substrate 15
6 is arranged to face the emitter layer 12.

In the cathode portion for electron emission obtained in this example, the tip of the emitter was sharp and the emission starting electric field (threshold electric field) was 10 V / μm or less. This was the same in the other examples.
Also, under the application of an average electric field of 22 V / μm, 300 μ
A discharge current density of A / cm ² could be obtained.

The electric field enhancement factor at the emitter tip of the obtained cathode was measured and found to be 10-18 V.
2.0 × 1 at a relatively low average electric field in the range of / μm
0 ⁴ / cm and 6.1 × 10 ⁴ / cm at a relatively high average electric field in the range of 18 to 22 V / μm,
A larger coefficient than the concentration coefficient reported previously was obtained.

Further, the emission characteristics of the conventional emitter are deteriorated due to the adsorbed material at the tip of the emitter during long-term use or storage, but the group III nitride layer emitter according to the present invention is measured after being stored for a long time. Even if the emission characteristics are not deteriorated, the emitter is highly reliable. This also applies to the other embodiments.

In this embodiment, the surface roughness of the Mo substrate is Ra1.
Although mirror-polished to about 0 nm, it is not always necessary to form such a mirror surface, and in some cases, a more sharp polycrystalline GaN layer can be formed due to the presence of appropriate irregularities on the surface of the Mo substrate. . This also applies to other examples using the Mo substrate.

Even when another metal substrate is used instead of the Mo substrate, in the same way as when the Mo substrate is used, in the in-situ observation of reflected electron beam diffraction during the growth of the polycrystalline GaN film, the initial growth Showed a ring-shaped pattern, but with the growth of the ring-shaped pattern, a gradually discontinuous ring-shaped pattern was shown. However, the AFM observation results show that the shape and size of the crystal grains differ depending on the type of the substrate. For example, when using a Ta substrate or Nb substrate, the size of the crystal grains in the grown polycrystalline GaN film is large. They were not even, and their particle size was in the range of 100-300 nm.

On the other hand, when the W substrate is used, the crystal grains in the polycrystalline GaN film are hexagonal, and the grain size is about 400 nm, which is the same as when the Mo substrate is used. . These crystal grains also caused a protrusion that could serve as an emitter on the surface of the film, and the radius of curvature of the tip was about 20 nm. The average number density of the protrusions that can serve as emitters was within the range of about 10 ⁹ to 10 ¹⁰ per cm ² .

(Embodiment 2) FIG. 2 is a schematic sectional view showing a manufacturing process of an electron emission cathode portion according to a second embodiment of the present invention. That is, FIGS. 2A and 2B show the process of manufacturing the cathode portion for electron emission, and in FIG. 2C, the completed cathode portion for electron emission is shown together with the anode portion oppositely arranged. .

In the method of manufacturing the cathode portion for electron emission in this embodiment, first, as shown in FIG. 2A, the Mo thin film 2 as a cathode electrode is formed on the glass substrate 21.
2 is deposited to a thickness of 50 nm. The substrate on which the cathode electrode is formed is degreased for 5 minutes with acetone and 5 minutes with ethanol, and then pickled with hydrochloric acid for 20 minutes.

The polycrystalline GaN layer 23 shown in FIG. 2 (b).
The MBE method is used to deposit the emitter layer made of. The glass substrate 21 and the Mo thin film 22 are introduced into the ultrahigh vacuum chamber and then thermally cleaned at 800 ° C. for 10 minutes. Next, the substrate temperature is lowered to 780 ° C., nitrogen atom plasma is supplied from the ECR plasma cell, and gallium is supplied from the heated cell, so that the polycrystalline GaN layer 23 having an uneven surface has a thickness of 0.6 μm. It is deposited on the Mo thin film 22 with an average thickness.

At this time, the Mo thin film 2 serving as the cathode electrode
The thickness of 2 is preferably 5 nm or more and 1 μm or less. This is because if the thickness of the Mo thin film 22 is 5 nm or less, the Mo thin film will not be detached during the thermal cleaning at 800 ° C. before growing the polycrystalline GaN layer 23. On the contrary, if the thickness of the Mo thin film 22 is set to 1 μm or more, in the process of growing the polycrystalline GaN layer 23, the temperature rises from room temperature to 800 ° C., 780
During the process of crystal growth at ℃ and the temperature change to room temperature, the difference in the thermal expansion coefficient between glass and Mo causes M
This is because the thin film 22 is peeled off from the glass substrate 21.

After that, the thickness of the insulating film 24 is 0.3.
A μm SiO ₂ film is formed on the entire surface of the polycrystalline GaN layer 23, and a Mo film to be the gate electrode 25 is formed on the entire surface of the SiO ₂ film. Next, a photoresist (not shown) is applied on the Mo film 25, patterned according to the layout of the region where the polycrystalline GaN layer 23 should act as an emitter, and the Mo film 25 is formed in the region not covered with the photoresist. The SiO ₂ film 24 is removed by etching to partially expose the polycrystalline GaN layer 23.

In this way, the emitter made of the polycrystalline GaN layer 23 having a plurality of convex portions and the gate electrode 25 surrounding the emitter are formed on the Mo negative electrode layer 22.

As shown in FIG. 2 (c), by arranging the anode part in opposition to the obtained electron emitting cathode part in a vacuum and applying an electric field, electrons are emitted from the emitter region 23. Can be released. That is, FIG.
In (c), the positive electrode layer 27 formed on the anode substrate 26 is arranged to face the emitter layer 23.

In this embodiment, the cathode electrode 22 is M
Although it is formed of a single layer of o, it may be formed of a multilayer structure including other metal layers or an alloy layer.

(Embodiment 3) FIG. 3 is a schematic sectional view showing a manufacturing process of an electron emitting cathode portion according to a third embodiment of the present invention. That is, FIGS. 3 (a) and 3 (b) show the process of manufacturing the cathode portion for electron emission, and in FIG. 3 (c), the completed cathode portion for electron emission is shown together with the anode portion oppositely arranged. .

In the method of manufacturing the cathode portion for electron emission in this embodiment, first, as shown in FIG. 3A, an ITO thin film 32 as a cathode electrode is sputtered on a glass substrate 31 to a thickness of 100 nm. To form. The substrate on which the cathode electrode is formed is 5
After 5 minutes of degreasing with ethanol and
Pickled with hydrochloric acid for 20 minutes.

The polycrystalline GaN layer 33 shown in FIG. 3 (b).
The MBE method is used to deposit the emitter layer made of. The glass substrate 31 and the ITO thin film 32 are introduced into the ultrahigh vacuum chamber and then thermally cleaned at 650 ° C. for 10 minutes. Next, the substrate temperature is lowered to 630 ° C., nitrogen atomic plasma is supplied from the ECR plasma cell, and gallium is supplied from the heated cell, so that the polycrystalline GaN layer 3 having an uneven surface is formed.
3 is deposited on the entire surface of the ITO thin film 32 with an average thickness of 0.4 μm.

Next, in order to remove the polycrystalline GaN layer 33 in the region corresponding to the gate electrode formation portion by dry etching, a photoresist (not shown) is applied and patterned according to the layout of the emitter region. The polycrystalline GaN layer 33 is removed by dry etching in the region not covered with the resist. In this example, the polycrystalline GaN layer was partially removed by reactive ion etching using Cl ₂ and SiCl ₄ , and the state is shown in FIG. 3B.

Then, a SiO ₂ film to be the insulating film 34 is formed with a thickness of 0.5 μm so as to cover the ITO thin film 32 and the polycrystalline GaN layer 33, and the gate electrode 35 is formed thereon.
A Mo film to be formed is formed. Then, a photoresist (not shown) is applied on the Mo film 35 to form a polycrystalline Ga film.
Patterning is performed according to the layout of the region where the N layer 33 should act as an emitter, and the Mo film 35 and the SiO ₂ film 34 are removed by etching in the region not covered with the photoresist to partially expose the polycrystalline GaN layer 33. .

In this way, on the ITO thin film 32, the emitter made of the polycrystalline GaN layer 33 having a plurality of protrusions and the gate electrode 35 surrounding the emitter are formed.

As shown in FIG. 3 (c), by arranging the anode part in opposition to the obtained cathode part for electron emission and applying an electric field, electrons are emitted from the emitter region 33. Can be released. That is, FIG.
In (c), the positive electrode layer 37 formed on the anode substrate 36 is arranged so as to face the emitter layer 33.

(Embodiment 4) FIG. 4 is a schematic sectional view showing a manufacturing process of an electron emission cathode portion according to a fourth embodiment of the present invention. That is, FIGS. 4 (a) and 4 (b) show the manufacturing process of the electron emission cathode part, and in FIG. 4 (c), the completed electron emission cathode part is shown together with the anode part which is arranged oppositely. .

In the method of manufacturing the electron emission cathode portion in FIG. 4, the Mo substrate 41 is first mirror-polished, degreased with acetone for 5 minutes and ethanol for 5 minutes, and then pickled with hydrochloric acid for 20 minutes. . Polycrystalline GaN layer 42
The MBE method is used for the deposition. The Mo substrate 41 is
After being introduced into the ultra-high vacuum chamber, thermal cleaning is performed at 800 ° C. for 10 minutes. Next, the substrate temperature is lowered to 780 ° C., nitrogen atomic plasma is supplied from the ECR plasma cell, and gallium is supplied from the heated cell to obtain polycrystalline GaN having an uneven surface.
Layer 42 is deposited on Mo substrate 41 with an average thickness of 0.5 μm.

A state in which the emitter layer 42 is vapor-deposited on the Mo substrate 41 as described above is shown in a schematic sectional view of FIG.

Next, in order to remove the polycrystalline GaN layer 42 in the region corresponding to the gate electrode formation portion by dry etching, a photoresist (not shown) is applied and patterned according to the layout of the emitter region. The polycrystalline GaN layer 42 is removed by dry etching in the region not covered with the resist. In this example, the polycrystalline GaN layer was partially removed by reactive ion etching using Cl ₂ and SiCl ₄ , and the state is shown in FIG. 4 (b).

After that, a SiO ₂ film to be the insulating film 43 is formed so as to cover the Mo substrate 41 and the polycrystalline GaN layer 42.
A Mo film having a thickness of 6 μm is formed on the gate electrode 44. Then, a photoresist (not shown) is applied on the Mo film 44 and patterned according to the layout of the region where the polycrystalline GaN layer 42 should act as an emitter, and the Mo film 44 is formed in the region not covered with the photoresist. The SiO ₂ film 43 is removed by etching to partially expose the polycrystalline GaN layer 42.

Thus, on the Mo substrate 41, the emitter made of the polycrystalline GaN layer 42 having a plurality of convex portions and the gate electrode 44 surrounding the emitter are formed.

As shown in FIG. 4 (c), by arranging the anode portion in vacuum to face the obtained electron emitting cathode portion and applying an electric field, electrons are emitted from the emitter region 42. Can be released. That is, FIG.
In (c), the positive electrode layer 46 formed on the anode substrate 45 is arranged to face the emitter layer 42.

(Embodiment 5) In Embodiment 5, an example of a full-color fluorescent display panel using the cathode portion for electron emission according to the present invention will be described with reference to FIGS. 5 and 6. That is, FIG. 5 is a perspective view schematically showing a full-color fluorescent display panel, and FIG. 6 is a schematic view of a cross section perpendicular to the cathode electrode row and passing through the opening of the gate electrode in the display panel of FIG.

In this display panel, a glass substrate is used as the cathode substrate 51. A cathode electrode 52 made of a Mo thin film having a thickness of 60 nm is formed on the cathode substrate 51, and a polycrystalline GaN layer 53 serving as an emitter is grown thereon to a thickness of 0.6 μm.

Next, a prescribed emitter region is a Mo thin film 52.
A photoresist (not shown) is applied and patterned so as to be arranged above, and the polycrystalline GaN layer 53 in the region not covered with the photoresist is removed by a dry etching method.

After that, the insulating film 54 has a thickness of 0.7 μm.
SiO ₂ film is formed, and a Mo thin film is formed as the gate electrode 55. The row of gate electrodes 55 includes the cathode electrodes 52.
Are formed so as to be orthogonal to the columns of. The emitter 53 is formed at the intersection of the gate electrode 55 and the cathode electrode 52.
The opening 56 is formed in the gate electrode 55 using photolithography so as to be arranged.

A glass substrate is used as the anode substrate 57, and R (red), G (green), and B are formed on the glass substrate.
An anode electrode 58 containing a phosphor for (blue) emission is formed. The full-color fluorescent display panel manufactured in this manner becomes a display panel that reads display information from the anode substrate 57 side.

If a transparent conductor thin film is used as the cathode electrode 52 instead of the Mo thin film, the cathode substrate 51
Since it is also transparent glass and the polycrystalline GaN layer 53 is also transparent, it is possible to manufacture a display panel for reading display information from the cathode substrate 51 side.

Further, although the polycrystalline GaN layer is used as the emitter layer in the above embodiments, the present invention is not limited to this, and Al
Similar effects can be obtained by using other polycrystalline group III nitride layers such as N and AlGaN.

Further, in the above embodiments, specific materials, specific film thicknesses, etc. are exemplified, but the present invention is not limited to these examples.

[0085]

As described above, according to the present invention, a highly reliable cathode for electron emission which can be easily manufactured at low cost and which can emit a sufficient amount of electrons per unit area in a low electric field. The parts can be provided with high yield. Such an electron-emitting cathode portion can be preferably used in, for example, a fluorescent display device, and its area can be easily increased.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a manufacturing process of a cathode portion for electron emission according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing the manufacturing process of the electron emission cathode portion according to the second embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view showing a process of manufacturing an electron emission cathode part according to Example 3 of the present invention.

FIG. 4 is a schematic cross-sectional view showing a process of manufacturing an electron emission cathode part according to Example 4 of the present invention.

FIG. 5 is a schematic perspective view of a full-color fluorescent display panel including an electron emission cathode portion according to the present invention.

6 is a schematic cross-sectional view of the fluorescent display panel of FIG.

FIG. 7 is a schematic cross-sectional view showing an example of a conventional electron emitting cathode portion.

FIG. 8 is a schematic cross-sectional view showing the manufacturing process of another example of the electron emitting cathode portion according to the conventional example.

[Explanation of symbols]

11, 41 Mo substrate, 12, 23, 33, 42 Polycrystalline GaN layer, 13, 24, 34, 43 Insulating film, 14,
25, 35, 44, gate electrode, 21, 31, glass substrate, 15, 26, 36, 45 anode substrate, 1
6, 27, 37, 46 Anode electrode, 22 Mo thin film, 32 ITO thin film, 51 cathode substrate, 52 cathode electrode, 53 emitter, 54 insulating film, 55 gate electrode, 56 opening, 57 anode substrate, 58
Anode electrode.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hajime Asahi             1-4-2-27-141 Nishimidoka, Toyonaka City, Osaka Prefecture

Claims (11)

[Claims] 1. A cathode part capable of emitting electrons by applying an electric field, comprising a group III nitride layer formed on an electrode by a vapor deposition method, the nitride layer being a surface on which the layer is deposited. An electron-emitting cathode part having an uneven surface suitable for electron emission, which reflects the uneven state. 2. The cathode part for electron emission according to claim 1, wherein the group III nitride layer is polycrystalline. 3. The cathode part for electron emission according to claim 1, wherein the electrode is made of a polycrystalline metal or a polycrystalline transparent conductor. 4. The electrode is Mo (molybdenum), Nb
(Niobium), Ta (tantalum), Ti (titanium), Hf
(Hafnium), Zr (zirconium), and Al
4. The electron emitting cathode part according to claim 1, which is made of a metal or an alloy containing at least one selected from the group consisting of (aluminum). 5. The electrode comprises zinc (Zn), indium (In), tin (Sn), magnesium (Mg), cadmium (Cd), gallium (Ga), and lead (Pb).
4. The cathode part for electron emission according to claim 1, comprising a transparent conductive oxide containing at least one selected from the group consisting of: 6. The cathode part for electron emission according to claim 1, further comprising a gate electrode for limiting a region where electrons are emitted from the group III nitride layer. 7. The group III nitride layer has a thickness of 0.01.
7. The cathode portion for electron emission according to claim 1, wherein the cathode portion has a thickness of at least μm. 8. The cathode portion for electron emission according to claim 1, wherein the group III nitride layer is an n-type semiconductor. 9. The cathode portion for electron emission according to claim 1, wherein the group III nitride layer is doped with Si. 10. The group III nitride layer is Al _x Ga _1-x.
10. The cathode portion for electron emission according to claim 1, wherein the cathode portion is made of N (0 ≦ x ≦ 1). 11. A fluorescent display device comprising the electron emission cathode portion according to claim 1. Description: