KR100701750B1 - Field Emission Array and method for fabricating same - Google Patents

Abstract

The present invention relates to the structure of the emitter, which is an important element of the field emission display, and a manufacturing method thereof. In particular, it is possible to apply various emitter materials having a long lifetime and high efficiency of electron emission characteristics, and to provide a low cost such as glass. It is an object of the present invention to provide a new type of emitter structure and a manufacturing process thereof, in which a substrate can be used and the manufacturing process is simple and the uniformity of the emitter can be easily secured so that it can be easily enlarged. In order to achieve the above object, an ultra-fine particle for emitting electrons is formed on a fine metal pillar film formed on a substrate by using a low-cost glass substrate, and a thin insulating film is coated on the surface of the ultra-fine particle.

Field emission, electron emission, ultra fine particles, insulation coating

Description

Emitter structure of field emission device and its manufacturing method {Field Emission Array and method for fabricating same}

Figure 1. Structure of the conventional electron emitting device

Figure 2. Structure of the electron emitting device of the present invention

Figure 3. Process Drawing of Electron Emission Device of the Present Invention

Figure 4. Process diagram of manufacturing an electron-emitting device according to another embodiment of the present invention

Recently, the interest and importance of displays, which play an important role with the development of multimedia, have increased. In response to this, various flat display devices such as liquid crystal display (LCD) and plasma display (PDP) have been developed and put into practical use. However, they are still satisfactory in view of viewing angle, high-speed response, high brightness, high power consumption, and thinness. CRT is closest to the ideal at present, except for problems such as thinness, weight and power consumption.

Among these, field emission display (FED), which is attracting attention as a next-generation display, uses phosphor emission by the same electron beam as CRT, without distorting the image while maintaining excellent characteristics of the CRT. It has the advantage of being able to realize a flat display of low power consumption.

The basic structure of the field emission display device is a three-pole tube like a conventional vacuum tube. However, the electric field is concentrated on an emitter, a sharp cathode, without using a hot cathode. Cold Cathode, which emits electrons by quantum mechanical tunneling effect, is used. The electrons are accelerated by the applied voltage between the anode and the cathode and collide with the phosphor film formed on the anode to emit light. That is, the same principle as the CRT in that the phosphor emits light due to electron collision.

Representative conventional field emission type devices are shown in FIG. 1 in the form of a tip type. An electrode 12, an emitter 13 in the form of a tip from which electrons are emitted, an insulating film 14, and a gate 15 for controlling the amount of electrons emitted from the emitter are formed on the substrate 11. According to the manufacturing method for making this type of device, a spint type emitter and Si (silicon) wafer or Si thin film that form Mo metal by electron beam (e-Beam) deposition are tip dry or wet. There is a Si-type emitter that forms a thermal oxide film by oxidizing the surface of the Si tip at a high temperature (1000 ° C.) after forming a shape, and removing the thermal oxide film with an SiO ₂ etchant.

In case of Si type, a high temperature thermal oxidation process is required in the process of sharpening the tip, which makes it impossible to use a large sized substrate such as glass, which limits the size of the display. As a result, the thermal stress is concentrated at the tip end during electron emission, and the tip is easily broken and the Si surface is easily changed by the residual gas, thereby deteriorating the electron emission characteristic of the tip.

On the other hand, in the case of a spin type emitter in which a high melting point Mo is formed by electron beam deposition, the tip has a longer life than the Si tip. However, the manufacturing process is complicated and the angle of the beam when the Mo film is deposited When the device is implemented on a large substrate because adjustment is required, there is a limitation in manufacturing a large display because the tip shape is uneven and electron emission is concentrated only on a specific tip, thereby easily breaking the tip.

In the case of the tip emitter type, when the device is operated, the tip is easily broken due to the uneven tip shape. Therefore, the tip size is reduced as much as possible to reduce the tip shape uniformity and the driving voltage. It is confined to the sub-micron region.

Therefore, it is possible to use a low-cost substrate such as glass, and a new type of structure and a process for manufacturing the same that require a simple manufacturing process and easily secure the uniformity of the emitter are required to be easily enlarged.

The present invention, in the emitter used in the field emission display device, unlike the tip-type emitter using a conventional Si, etc., it is possible to apply a variety of emitter materials having a long life, high efficiency electron emission characteristics It is an object of the present invention to provide a new type of emitter structure and its manufacturing process, which enables the use of a low-cost substrate such as glass and can be easily enlarged, thereby simplifying the manufacturing process and ensuring the uniformity of the emitter.

The first feature of the present invention is that nanoparticles having a particle diameter of 200 to 500 microns are formed on the fine metal pillar film formed on the substrate by the electron emitting device using a low-cost glass substrate, and ultrafine particles of nanoparticles are formed. A thin insulating film is coated on the surface.

A second feature of the present invention is to use a sputtering method at a high pressure of 60 to 700 mTorr or more, unlike the conventional spin coating method, as a method of forming discontinuous ultrafine particles. By using nanoparticles as a hard mask to form particles attached to micrometallic columns through plasma etching of the underlying metal plate, it is possible to improve electric emission from nanoparticles by applying electric field concentration to nanoparticles when voltage is applied. The driving voltage is reduced.

The third aspect of the present invention is to coat an insulating film made of a thin film such as SiO ₂ or Al ₂ O ₃ on the surface of the particles to increase the electron emission from the particles by the field-induced hot electron emission effect and the residual It is to implement a field emission device that improves the life and stability of the emitter by preventing particle breakage due to the collision of the sun and ionized gas.

Hereinafter, the features of the present invention will be described in detail with reference to the drawings. First, Fig. 2 shows the configuration of a two-pole type electron-emitting device as the basic structure of the field-emitting device implemented in the present invention. An electrode 22 is formed on the substrate 21, a metal film 23 is formed on the electrode in the form of a column, and ultrafine particles 24 are formed on the ends of the metal film to emit electrons. The insulating film 25 is formed on the entire surface of the substrate 21 including the metal film 23 and the ultrafine particles 24, and is formed by an electric field between the electrode 22 formed on the substrate and the anode formed on the opposite substrate. It is a bipolar structure in which electron emission is controlled.

In conventional tip type emitters, the lower diameter of the tip is formed to be around 1μm, which is the limit of the pattern size by the photolithography technique up to now, so that the tip of the tip sharpens the tip for effective electron emission. The radius of curvature of the tip tip should be 300 Å or less.

In addition, the present invention further comprises a thin insulating film 25 on the surface of the particle, which is coated with a SiO ₂ or Al ₂ O ₃ film of about several tens of GHz to increase the electron emission from the particles and residual gas or ionization during operation of the device. To prevent particle damage caused by collision of the gas. When a thin insulating film is coated on the emission region where electrons are emitted, a path through which an electric field is concentrated to allow electrons to pass through, ie, a conducting channel, is formed between the insulating film and the particles, thereby emitting electrons by conventional tunneling. In addition, the field induced hot electron emission (Electromagnetic Emission) acts to bring the effect of increasing the amount of electron emission.

The manufacturing method of the device as described above is as follows. In the present invention, since an ultra-fine particle (Nanoparticle) of about 200 직경 in diameter is used as an electron emission source, a separate tip sharpening process like the conventional tip type is unnecessary, and the coating is performed in the spin coating method, which is a conventional particle dispersion coating method. Although the particles used in the manufacturing process are difficult to produce particles with a size of several μm or less, and the particle size distribution is very uneven, on the other hand, the sputtering method at a high pressure of 60 to 700 mTorr or more is used, thereby uniformly obtaining ultrafine particles. It is possible to apply.

At relatively low pressures of several tens of mTorr or less, the probability of sputtered particles colliding with the gas in the plasma is relatively small, resulting in nucleation on the substrate and forming a uniform continuous film through continuous film growth. However, when sputtering is performed at a high pressure of several hundred mTorr or more, the sputtered particles have a high probability of colliding with gas, so the particles are aggregated into a plasma (cluster) in the plasma, and when the temperature of the substrate is low, the substrate reaches the substrate. Clusters stop growing and form into discontinuous nanoparticles.

3 is a step-by-step manufacturing process diagram of the bipolar electron-emitting device.

First, as shown in FIG. 3A, a lower electrode 32 made of a metal such as Al, Cr, Cu, or the like is formed on a substrate 31 such as glass, which is advantageous in producing a large-capacity device, and the base metal film is used as a support layer for particles. Tabernacle (33). The metal film selects a material having a high etching selectivity with ultra-fine particles during etching in a later process.

In the step (b), ultrafine particles 34 are discontinuously deposited on the base metal film 33 by using the high pressure sputtering method. At this time, the pressure of the sputtering is in the range of 60 ~ 700 mTorr, the material of the particles can be applied to various metal materials such as Mo, Cr, Ta, Cu. At the time of sputtering, ultrafine particles such as nitride or carbide may be applied by forming nitrogen or CH ₄ atmosphere. At this time, the substrate temperature is kept as low as possible to quickly condense the particles reached to the substrate, thereby suppressing the continuous growth of the particles. In order to lower the substrate temperature, a method of cooling the substrate with liquid nitrogen or the like is used.

In step (c), the base metal film 33 is etched using the nanoparticles 34 as a hard mask. At this time, the etching method used is to etch the base metal film 33 by selecting a gas having a selectivity with the ultra-fine particles (34) by the RIE method. After etching, the base metal layer 33 is formed in the shape of a metal pillar, and has a form in which ultraparticles 34 are attached to the micropillars. When a voltage is applied, an electric field is concentrated to ultrafine particles, and electrons in the particles are concentrated. Improves emissions.

In the step (d), the insulating film 35 is finally coated. The lifetime and stability of the emitter by coating an insulating film 35 such as SiO ₂ or Al ₂ O ₃ on the entire substrate on which the ultra-fine particles 34 are attached on the metal pillar-shaped metal film 33. And improve the electron emission effect.

4 is a method of manufacturing an electron-emitting device in which the emitter structure of the present invention is applied to a three-pole structure. The three-pole structure is a structure in which the amount of electron emission in the emitter is controlled by the gate electrode, and the gate electrode is added as compared to the two-pole structure. Step-by-step manufacturing process is as follows.

In the step (a), the lower electrode 42, the base metal film 43, the first insulating film 44, and the gate film 45 are successively formed on the glass substrate 41, and the photoresist 46 is coated. And pattern to have a predetermined shape. In this case, the first insulating film is SiO ₂ or the like for electrical insulation between the base metal film 43 and the gate film 45. The gate film 45 is formed of Mo, Cr, Nb, or the like.

In step (b), the gate layer 45 and the first insulating layer 44 are etched by the patterned photoresist 46 to form an emission region.

In step (c), superfine particles (Nanoparticle) 47 are sputtered discontinuously.

In step (d), the base metal film 43 is RIE-etched using the ultra-fine particles 47 as a mask to form metal pillars.

In step (e), the second insulating film 48 is thinly coated on the resultant of step (d). At this time, in order to prevent the insulating film is coated on the side of the gate film 45 is coated by the electron beam method.

(f) Finally, the photoresist 46 is removed to complete the electron-emitting device having a three-pole structure.

In the case of ultra-particle field-emitting devices manufactured by the above method, it is possible to overcome the limitation of shortening of the lifespan and enlargement due to the nonuniformity of the tip, which is a problem in tip type emitters, and complicated photo etching process is unnecessary. It is also very advantageous in terms of cost reduction.

Since the extremely uniformly distributed nanoparticles are used as emitters, the electron emission area per unit area is increased compared to the tip type, and the electron emission amount is increased. It is possible to drive to low voltage.

In addition, when a high quality insulating film is coated on the particle surface, the electron emission is effectively increased even by low voltage due to the field induced thermal electron emission effect. It is also advantageous in terms of the lifetime of the device.

Claims (4)

An electrode layer formed on the substrate, a pillar-shaped metal film formed on the electrode layer, ultrafine particles (particle diameter ≤ 500 μs) formed at the tip of the metal film and emitting electrons, and a metal film formed with the electrode layer and ultrafine particles (Nanoparticle) Emitter structure of a field emission device including an insulating film formed on the front surface The emitter structure of claim 1, wherein an insulating layer and a gate electrode are further formed on the electrode layer to surround the metal film on which the nanoparticles are formed. The emitter structure of a field emission device according to claim 1, wherein the ultrafine particles are a metal material selected from Mo, Cr, Ta, and Cu. Forming an electrode layer on the substrate, forming a metal film on the electrode layer, forming nanoparticles (particle diameter ≤ 500 μs) by sputtering on the metal film, and plasma plasma the metal film using the ultrafine particles (Nanoparticle). A method of manufacturing an emitter of a field emission device comprising etching, and coating an insulating film on the entire surface of the substrate including the etched metal film and ultrafine particles.

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