JPH10302608A - Field emitter element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the whole structure, dispense with the use of a high technique and reduce the manufacturing cost by forming a polycrystalline diamond film rendered conductive on an insulating substrate in strip, and forming an insulating film and a gate electrode in strip so as to cross the diamond film. SOLUTION: A strip conductive diamond film 2 is formed on an insulating substrate 1. A voltage is applied between the conductive diamond film 2 acting as an emitter electrode and a strip gate electrode 4 formed thereon through an insulating film 3 so as to cross the diamond film. Tunnel electrons by field emission are emitted from the emitter electrode by the strong electric field added between the edge part of the gate electrode 4 and the crystal sharp part of the diamond film 2. A spot electron source in which the emitter electrode and the gate electrode are formed in strip, respectively, to emit electrons in their crossing position can be provided with a simple structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a field emitter element having higher image quality than a liquid crystal display and usable for a field emission display (FED), a light emitting device and the like.

[0002]

2. Description of the Related Art To manufacture a field emitter element,
C. A. The method proposed by Spindt (Journal
of Applied Physics, Vol. 4
7, No. 12, December 1976);
F. The method proposed by Gray et al. (3rd IVMC, 1
990). Recently, it has been reported that a diamond film has a negative electronegativity, and there has been published a report of applying the diamond film to a field emitter display. For example, a method of coating diamond on a needle-like emitter surface (Japanese Patent Laid-Open No.
05617), and a method of producing a needle-shaped diamond emitter by plasma etching or the like (Japanese Patent Application Laid-Open No. 7-29483) has been reported, but high processing technology and film forming technology are required, and productivity is low. In addition, examples are disclosed in which a polycrystalline diamond film is used as it is as an emitter (Japanese Patent Application Laid-Open Nos. 5-152640 and 7-272618).

[0003]

It is said that the field emitter element according to the method of Spindt et al. Requires a high level of fine processing technology and it is difficult to realize a manufacturing cost comparable to that of a liquid crystal panel. Further, the current field emitter display has a short lifetime because the emitter surface is easily contaminated by an adsorbed gas or the like, and has not been put to practical use for general use. Further, in the conventional manufacturing method, the shapes of the individual emitters are apt to vary, resulting in uneven coloring. In addition, ordinary polycrystalline diamond has problems that the emission current is insufficient and that it is difficult to produce an emitter having structurally stable characteristics.

[0004]

According to the present invention, a polycrystalline diamond film having conductivity is formed in a strip shape on an insulating substrate, and the insulating film and the gate electrode are formed in a strip shape so as to cross the diamond film. A field emitter element, wherein at least one of the width of the band of the polycrystalline diamond film and the gate electrode is 0.01
A field emitter element characterized in that it is not more than 0.3 mm and a field emitter element characterized in that at least 60% of the surface of the polycrystalline diamond film is formed by a (111) plane. Compared to
The overall structure is simpler, and there is no need to use advanced photolithographic and precision processing techniques, thereby reducing manufacturing costs.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The insulating substrate used in the present invention is:
For example, Si, SiC, SiO ₂ , Si ₃ N ₄ , alumina, AlN, sapphire and the like can be mentioned. Among them, Si, Si ₃ N ₄ , and AlN are particularly preferable because a high adhesion to the diamond film can be obtained. It is preferable that the insulating substrate has an insulating property of 1 × 10 ⁶ Ω · cm or more and has a high resistance as much as possible, in order to prevent a current flowing through the strip-shaped diamond electrode from leaking to another diamond electrode through the insulating substrate. is there. A strip-shaped conductive diamond is formed on the insulating substrate. As a method for forming a diamond film, a known gas phase synthesis method or the like can be used. For example, there are a hot filament CVD method, an EACVD method, a microwave plasma CVD method, an ECR plasma CVD method, a DC plasma CVD method, a combustion flame method and the like. Generally, a mixed gas of hydrogen and a carbon-containing material is used as a source gas. Generally, methane, ethane, ethanol,
Methanol, acetone, benzene, carbon dioxide, carbon monoxide and the like are used.

As a method of imparting conductivity to a diamond film, there is a method of forming a p-type or n-type semiconductor by doping or a method of adding a conductive impurity to the diamond film. Examples of the dopant for forming a p-type semiconductor include boron, and examples of the dopant for forming an n-type semiconductor include phosphorus and sodium. The conductive impurities include, for example, graphite, W, T
a, Mo and the like. The addition amount of these dopants and impurities is an amount sufficient to realize a resistivity of 1 × 10 ³ Ω · cm or less of a diamond film necessary for manufacturing a field emitter, and is usually preferably in a range of 10 to 10,000 ppm. 10,000ppm of dope to diamond film
If it exceeds, the resistivity of the diamond decreases, but the crystallinity also decreases, the sputtering resistance of the diamond film decreases, and the life of the emitter decreases. The resistivity of the diamond film is preferably set to 1 × 10 ³ Ω · cm or less, because the current flowing through the band-shaped diamond electrode is restricted, or the diamond film generates heat, and the emission current becomes unstable. This is to prevent Dopants,
The amount of the impurity added is an amount sufficient to realize a resistivity of 1 × 10 ³ Ω · cm or less of the diamond film required for manufacturing the field emitter, and is usually in a range of 10 to 10,000 ppm. The addition of dopants and impurities to the diamond film is affected by the additives, but the addition of 10 ppm results in a resistivity of the diamond film of about 1 × 10 ³ Ω · cm. When the addition amount is 10 ppm or more, the resistivity of diamond gradually decreases, and when it is 10,000 ppm, the resistivity becomes about 1
At about 0 Ω · cm, the crystallinity of the diamond starts to deteriorate from around this point, and the sputtering resistance of the diamond film decreases, and the life as an emitter decreases.
Therefore, the resistivity of the diamond film in a practical sense is 10
The range is preferably 1 to 10 ³ Ω · cm.

According to the present invention, the conductive diamond film (which acts as an emitter electrode) is formed in a band shape, and a voltage is applied between the emitter electrode and a crossed band-shaped gate electrode to be formed later on the film. Tunnel electrons are emitted from the emitter electrode by field emission due to the strong electric field applied between the edge of the gate electrode and the sharp part of the crystal of the diamond film in the vicinity thereof. Since the emitter electrode and the gate electrode are respectively strip-shaped and electrons are emitted at intersections, a point-shaped electron source can be obtained with a simple structure. That is, the field emitter element according to the conventional method is
A very small needle-shaped electrode with an emitter element size of 1 μm is used, millions of these are arranged at a high density in order to provide a stable electron source, and a gate electrode having an opening of about 1 μmφ is provided for each emitter electrode. Needed. On the other hand, in the field emitter element according to the present invention, it is preferable to use a polycrystalline diamond having many (111) planes and many sharp portions for the emitter. The gate electrode has a band-like structure with a cross, and a strong electric field is generated at the end of the gate electrode to cause field emission at the sharp part of diamond, so the element structure is simpler and easier to manufacture than the conventional method. Become.

The intersection angle between the band-shaped diamond film and the gate electrode is preferably 60 degrees or more and 120 degrees or less, more preferably 80 degrees or more and 100 degrees or less, and further preferably a right angle. If the crossing angle is less than 60 degrees or exceeds 120 degrees, the electron beam shape of the point electron source becomes oblong and the electron density decreases,
The field emission feature that a high-density point electron source can be obtained cannot be utilized, which is not preferable. Band width of polycrystalline diamond film and gate electrode is 0.01 mm
Not less than 0.3 mm and more preferably not more than 0.0 mm.
5 mm or more and 0.2 mm or less. If the width of the diamond film and the gate electrode exceeds 0.3 mm, the electron beam obtained at the crossing portion also spreads to 0.3 mm square or more, and the field emission feature that a stable point electron source can be obtained is not utilized. On the other hand, if the width of the gate electrode exceeds 0.3 mm, the electron beam emitted by the electric field generated at both ends of the gate electrode is separated into two, and the characteristics as a point electron source are undesirably reduced. The width of the electrode is 0.
When the diameter is smaller than 01 mm, the resistance of the electrode increases and heat is generated due to the emission current. In addition, the sharp portion of the diamond film where the field emission occurs is reduced, the emission current is reduced, and the feature as an excellent point electron source is utilized. It is not preferable because it is not performed. As a method of forming a diamond film in a band shape, after the diamond film is coated on the entire surface, the diamond film can be processed into a band shape using a dicing saw or a laser. As a method for selectively growing a diamond film in a band shape, a method using a band-shaped SiO ₂ mask manufactured by photolithography (T.
Inoue, H .; Tachibana, K .; Kumag
ai, K .; Miyata, K .; Nishimura,
K. Kobayashi and A.K. Nakane,
Journal of Applied Physi
cs, Vol. 67, 7329 (1990)) and metals (for example, Fe, Y, Pt, T
a, Nb, Ti, W, Mo) or the like in advance in a strip shape on an insulating substrate.

The thickness of the conductive polycrystalline diamond film serving as the emitter electrode is preferably 0.1 μm or more and 0.5 mm or less, more preferably 1 μm or more and 0.1 mm or less. In general, as the CVD diamond film becomes thicker, the constituent diamond particle diameter on the surface becomes larger. For example, film thickness 1
When the thickness is 0 μm, the diameter of the diamond constituting the surface is about 6 μm, and when the thickness is 0.1 mm, the diameter is about 50 μm. Therefore, when the diamond film thickness is increased, the amount of the sharp portion such as the ridge line of the crystal on the surface per unit area is reduced, the portion where the electric field by the gate voltage acts is reduced, and the field emission current density tends to decrease. Further, as the diamond film becomes thinner, the density of the sharp part increases and the emission current density increases, but the resistance value of the diamond film increases and the emission current is limited. Materials that can be used as the gate electrode of the present invention include, for example, Al, Au, Pt, M
o, W and the like. As a film forming method, a vacuum evaporation method,
There are a sputtering method, an ion plating method and the like.
The thickness of the gate electrode is preferably about 0.1 to 50 μm.
If the gate electrode is too thin, the resistance value increases and heat is generated, which may cause melting. If the gate electrode is too thick, the cost is increased for the effect improvement, which is not preferable. The diamond film of the present invention to be formed is more preferably 60% or more of the surface.
% Or more is preferably formed on the (111) plane. The (111) plane of the diamond film is said to have a negative electronegativity, and electrons can be easily taken out into a vacuum. (1)
When the ratio of the 11) plane exceeds 60%, a large number of quadrangular pyramid crystals formed on the (111) plane can be formed, and the tip portion thereof is sharp and a strong electric field is easily generated, which is preferable. Therefore, it is easy to obtain a current density sufficient to illuminate a phosphor such as a display even at a low gate voltage.

The (111) plane of the diamond film is assumed to have a negative electronegativity. By increasing the ratio, electrons can be easily taken out into a vacuum. If the ratio of the (111) plane is lower than 60%, the value of the gate voltage sharply increases, and the possibility that the element is destroyed by a discharge between the diamond film and the gate electrode or the like increases, which is not preferable. In CVD diamond synthesis (11
1) As a method of increasing the surface ratio, the substrate temperature during film formation is set lower than usual to 700 ° C. or less. For example, there is a method in which the ratio of the carbon raw material to hydrogen is made higher than usual to make the atomic ratio C / H 0.015 or more. Also, a method of obtaining a highly oriented diamond film by performing an electric field treatment on a Si or β-SiC substrate has been reported (S. Yugo, T. Kanai, T. Kimu).
ra and T.R. Muto, Appl. Phys. L
ett. , 58 (1991) 1036). An insulating film and a gate electrode are formed in a band shape in this order so as to cross the band of the diamond film. When a negative voltage is applied to the diamond film between the diamond film and the gate electrode sandwiching the insulating film and a voltage is applied, a strong electric field is generated at the end of the gate electrode and the sharp portion of the diamond crystal, and an emission current is generated from the diamond film. FIG. 1 shows an example of a specific structure. Further, it is more preferable that the band-shaped gate electrode has a slit-like or round hole at the intersection in the range of 0.01 to 0.3 mm as shown in FIG. This makes it possible to increase the sharpness of the diamond crystal on which the electric field acts and increase the emission current.
In this case, since the emitter electrode uses a diamond film having sharp portions at random positions, unlike a Spindt-type field emitter, it is not necessary to make the sharp portion of the emitter correspond to the opening of the gate electrode, and the structure is simple and high. A point electron source with a current density can be obtained.

As a method of laminating the insulating film and the gate electrode, a usual photolithography process can be used. For example, after forming an insulating film, a belt-like pattern of a resist is formed thereon, and a gate electrode layer is formed thereon, and then the resist is peeled off to form a belt-like gate electrode. Further, by dissolving the portion of the insulating film that appears on the surface of the substrate, a strip-shaped electrode in which the insulating film and the gate electrode are stacked can be obtained. As another manufacturing method, after forming an insulating film, a gate electrode layer is formed thereon, and a belt-like pattern of a resist is formed thereon. After that, the same structure can be formed by removing the electrode layer appearing on the surface, removing the insulating layer appearing on the surface, and finally removing the resist. Examples of the insulating layer include, for example, SiO ₂ , Si ₃ N ₄ , ZrO ₂ , alumina, and polyimide. As a forming method, there are a coating method, a vapor deposition method and the like. The thickness of the insulating layer is 0.1
-10 μm is preferred. If the thickness of the insulating layer is 0.1 μm or less, it cannot withstand the applied gate voltage, which may cause dielectric breakdown, which is not preferable. On the other hand, if it exceeds 10 μm, the electric field applied to the diamond crystal surface becomes low, and it becomes difficult for field emission to occur.

[0012]

EXAMPLES Examples of the present invention will be specifically described below, but the present invention is not limited to these examples.

(Example 1) An insulating (specific resistance: 1 × 10 ¹⁴ Ω · cm) alumina plate (density is 98% of the theoretical density) 20 × 20 × 3 mm was used as a substrate. Using a hot filament CVD method with a tantalum filament, the input power is 1 kWh, the reaction pressure is 100 Torr, the raw material gas is hydrogen 1 liter / min, methane 50 cc / min (C / H atomic ratio = 0.025), B ₂ H ₆ The composition was synthesized for 2 hours under the conditions of 0.02 cc / min, the substrate temperature of 600 ° C., and the distance between the substrate and the filament of 10 mm to form a diamond film having a thickness of 5 μm. The (111) plane occupied 85% of the whole crystal orientation of the diamond film, and the others were composed of (100) and (110) planes. When the resistivity of the diamond surface was measured, it was 78 Ω · cm.

The plate on which the conductive diamond was formed was coated with an excimer laser (ArF, average output 30 W, pulse width 15
The surface of the diamond film was scanned at a speed of 3 mm / S using nS), and the diamond film was processed into a band shape having a width of 300 μm and a length of 20 mm by removing only the diamond film while leaving the alumina substrate at the laser-irradiated portion. The surface of this plate is coated with SiO ₂ paint (OCD Ty, Tokyo Ohka Co., Ltd.).
pe-7) was spin-coated (at 500 rpm) for 20 seconds, and heated and dried in a nitrogen gas at 200 ° C. for 1 minute to form a 1 μm thick SiO ₂ insulating film.
On top of this, a synthetic rubber-based resist (Tokyo Ohka Co., Ltd. EPP)
R) by dip coating to a thickness of about 10 μm,
After drying in warm air of 00 ° C. for 20 minutes, the central part of the strip-shaped diamond film is exposed to light by crossing the central part of a metal mask having a width of 300 μm and a length of 15 mm at 90 ° (wavelength 436n).
m, an exposure amount of 150 mJ / cm ² ), developed, and formed a slit-shaped pattern in the resist crossing a diamond band having a width of 300 μm and a length of 15 mm. After drying with air at 120 ° C. for 20 minutes to remove the residual solvent, the tungsten gate electrode layer was formed to a thickness of 0.6 by RF sputtering.
A film was formed with a thickness of μm. Then remove the resist and remove
After forming a tungsten electrode with a width and length of 15 mm,
The exposed insulating layer of SiO ₂ was removed with hydrofluoric acid (10% aqueous solution). This device was sealed in a glass container, and the inside was baked at 500 ° C. for 5 hours after decompression to 1 × 10 ⁻⁷ Torr to clean the surface. When a negative voltage was applied to the diamond film (cathode electrode) and a positive voltage of 84 V was applied to the gate electrode, a current of 3 μA flowed between the cathode and the gate.

(Embodiment 2) A band-shaped gate electrode having the same width as that of Embodiment 1 and having a width of 10
One opening of 0 μm square was provided. This device was manufactured under the same conditions as in Example 1 and the same voltage (84 V) was applied. As a result, a current of 5 μA flowed between the cathode and the gate.

(Examples 3 to 7) In Example 1, a comparison was made by changing the ratio of the (111) plane to the whole crystal surface of the diamond film. Other conditions were the same as in Example 1, and the voltage between the cathode and the gate at which the same current as in Example 1 was obtained was measured. As a result, the results shown in Table 1 were obtained.

[0017]

[Table 1]

[0018]

According to the present invention, a point electron source having excellent characteristics can be manufactured by a simple process and structure, and when applied to a flat panel display or the like, the cost and cost can be greatly reduced as compared with conventional ones. .

[Brief description of the drawings]

FIG. 1 is a perspective view showing one structure of the present invention.

FIG. 2 is a top view showing one structure of the present invention.

[Explanation of symbols]

 Reference Signs List 1 insulating substrate 2 conductive diamond film 3 insulating film 4 gate electrode

Claims (3)

[Claims] 1. A field, wherein a polycrystalline diamond film provided with conductivity is formed in a band shape on an insulating substrate, and the insulating film and the gate electrode are formed in a band shape so as to intersect with the diamond film. Emitter element. 2. The field emitter element according to claim 1, wherein at least one of the widths of the band of the polycrystalline diamond film and the gate electrode is 0.01 to 0.3 mm. 3. The field emitter element according to claim 1, wherein 60% or more of the surface of the polycrystalline diamond film is formed by the (111) plane.