KR20010049451A - Field emission display device using vertically aligned carbon nanotube and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A field emission display using vertically oriented carbon nano tube and a manufacturing method thereof are provided to increase emitter tip density per unit and enable a large size and to simplify the manufacturing process. CONSTITUTION: In the field emission display using vertically oriented carbon nano tube, a metal coat for the cathode electrode(32) is formed on the bottom board(30). The bottom board(30) uses glass, quartz, silicon or Al2O3. A vertically oriented carbon nano tube(34) is formed on the metal coat(32). The carbon nano tube is used as an emitter tip. The carbon nano tube can gain large emitted current at below low operating voltage. As the carbon nano tube(34) has a high tip density per unit, emitting efficiency is also high. A spacer(36) is formed on the metal coat(32). An upper board(50) having a transparent electrode(52) for anode and phosphors(54) is formed on the spacer(36).

Description

Field emission display device using vertically aligned carbon nanotube and manufacturing method

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a field emission display (FED) device and a method of manufacturing the same, and more particularly, to a field emission display using vertically aligned carbon nanotubes and a method of manufacturing the same.

In general, a field emission display device emits electrons at the tip of an emitter tip affected by a strong electric field when a positive voltage is applied to the conical emitter tip by a few hundred volts from the external gate electrode. Hundreds to several kilos of voltage is applied to the transparent conductive film and the phosphor coated anode electrode to serve as a display device. However, the conventional field emission display device using a silicon tip made by etching a silicon substrate for an emitter has a difficulty in separating the anode electrode and the cathode electrode at minute intervals of about 1.0 to 1.5 nm. In addition, the conventional field emission display device has a problem in that the operating voltage is very high, the leakage current is high due to deterioration of the silicon tip due to high current emission, device reliability and performance deterioration, and manufacturing yield is low. In order to improve the problem of the field emission display device using the silicon tip, a field emission display device using carbon nanotubes has been proposed.

Conventional carbon nanotubes are synthesized by an electric discharge method or a laser deposition method, and then put in a cleaning solution and shaken and purified by an ultrasonic cleaner. In order to apply the purified carbon nanotubes to the field emission display device, the purified carbon nanotubes are injected into the pores of the porous ceramic filter. Subsequently, the emitter tip is formed by dipping carbon nanotubes in the pores of the porous ceramic filter onto the conductive polymer on the lower substrate for the field emission display device.

However, the field emission display device using the conventional carbon nanotubes for the emitter tip is more stable than the field emission display device using the silicon tip, but it is difficult to efficiently build the carbon nanotubes on the conductive polymer and the manufacturing process is difficult. Due to the complexity, the manufacturing yield is low and there is a problem that it cannot be manufactured in large areas. In addition, there is a problem that the electrical connection is not made completely between the conductive polymer on the substrate and the carbon nanotubes.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and to provide a field emission display device using carbon nanotubes having a large area and a high emitter tip density per unit area.

In addition, another technical problem to be achieved by the present invention is to provide a method for manufacturing a field emission display device capable of large area in a simple manufacturing process.

1 is a cross-sectional view showing a field emission display device using vertically oriented carbon nanotubes according to the present invention.

2 and 3 are cross-sectional views illustrating a method of manufacturing the field emission display device of FIG. 1.

4A to 4C are diagrams for describing the carbon nanotube growth method of FIG. 3.

5 is a schematic diagram of a thermal chemical vapor deposition apparatus used to grow the carbon nanotubes of FIG. 3 as an example.

FIG. 6 is a diagram illustrating a mechanism in which carbon nanotubes are grown on catalytic metal particles separated by the present invention.

In order to achieve the above technical problem, in the field emission display device of the present invention, a metal film for a cathode electrode is formed on a lower substrate, and carbon nanotubes for emitter tips oriented vertically are formed on the metal film. The carbon nanotubes are obtained by forming catalyst metal particles on the first metal film and vertically growing them on the catalyst metal particles by chemical vapor deposition. A spacer is provided on the metal film, and an upper substrate on which the transparent electrode and the phosphor are attached is attached to the spacer.

In order to achieve the above technical problem, the method of manufacturing a field emission display device according to the present invention includes forming a cathode electrode metal film on a lower substrate, and then growing by vertically aligning carbon nanotubes on the metal film. do. The vertically grown carbon nanotubes form a catalyst metal film on the metal film, and then, the surface of the catalyst metal film is etched to form separated nano-sized catalyst metal particles, and chemical vapor deposition using carbon source gas. It is obtained by growing the carbon nanotubes in the vertical direction for each of the separated catalyst metal particles. When the catalyst metal particles are formed and the carbon nanotubes are grown, thermal chemical vapor deposition or plasma chemical vapor deposition may be used. The carbon source gas may be acetylene, ethylene, propylene, propane or methane gas. When etching the surface of the catalyst metal film, ammonia gas, hydrogen gas, or hydride gas may be used, or a hydrogen fluoride solution may be used. The catalytic metal film may be formed of cobalt, nickel, iron, yttrium, or an alloy thereof. Subsequently, after the spacer is formed on the metal film, an upper substrate on which the transparent electrode and the phosphor are attached is attached to the spacer to complete the field emission display device.

The field emission display device using the vertically oriented carbon nanotubes according to the present invention has a two-electrode structure, which is simple in structure, thereby increasing production yield and making it large in area. In addition, the use of well-oriented carbon nanotubes as the tip for the emitter allows for a large emission current even at low operating voltages.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, embodiments of the present invention illustrated below may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. In the drawings, the size or thickness of films or regions is exaggerated for clarity. In addition, when a film is described as "on" another film or substrate, the film may be directly on top of the other film, and a third other film may be interposed therebetween.

1 is a cross-sectional view showing a field emission display device using vertically oriented carbon nanotubes according to the present invention.

Specifically, in the field emission display device of the present invention, the cathode electrode metal film 32 is formed on the lower substrate 30. The lower substrate 30 is made of glass, quartz, silicon, or alumina (Al ₂ O ₃ ) substrate. The metal film 32 is composed of a chromium film, a titanium film, a tungsten film, an aluminum film, or the like. The vertical carbon nanotubes 34 are formed on the metal layer 32. The carbon nanotubes 34 are used as emitter tips. This vertically oriented carbon nanotube 34 can achieve a large emission current at low operating voltages, for example 3V / μm or less. In addition, since the vertically aligned carbon nanotubes 34 have a high tip density per unit area, the luminous efficiency may be improved. The spacer 36 is formed on the metal film 32. On the spacer 36, an upper substrate 50 having an anodized transparent electrode 52 and a phosphor 54 attached to the surface is provided.

In the field emission display device configured as described above, an electric field is applied between the first metal film 32 for the cathode electrode and the transparent electrode 52 for the anode to emit electrons from the carbon nanotubes 34 oriented in the vertical direction. The electrons collide with the phosphor 54 to emit red, green and blue light. As a result, the field emission display device of the present invention is a two-electrode field emission display device having two electrodes.

2 and 3 are cross-sectional views illustrating a method of manufacturing the field emission display device of FIG. 1.

Referring to FIG. 2, the cathode electrode metal film 32 is formed to a thickness of 0.2 μm to 0.5 μm on the lower substrate 30 having a large area. The lower substrate 30 may be a glass, quartz, silicon, or alumina (Al ₂ O ₃ ) substrate. The metal film 32 is formed using a chromium film, a titanium film, a tungsten film, an aluminum film, or the like.

Referring to FIG. 3, the carbon nanotubes 34 are grown vertically on the metal layer 32. The carbon nanotubes 34 are vertically grown to form a catalyst metal film (not shown) on the metal film 32, and the surface of the catalyst metal film is etched by a dry or wet method to separate nanoparticles. After formation of independently isolated nano-sized catalytic metal particles (not shown), the carbon nanotubes 34 are vertically oriented by thermal chemical vapor deposition or plasma chemical vapor deposition on the catalytic metal particles. Grow a plurality. If necessary, the metal film 32 and the catalyst metal film may be patterned in a fine line pattern, and then the surface of the patterned catalyst metal film may be etched to grow the carbon nanotubes 34. The carbon nanotubes 34 are used as emitter tips, and the carbon nanotubes 34 may form multiple emitter tips per pixel, thereby obtaining a large emission current at a low operating voltage. The vertical growth method of the catalyst metal particles and the carbon nanotubes 34 will be described later in more detail.

Subsequently, referring to FIG. 1, a spacer 36 is provided on the metal film 32 with a thickness of 100 to 700 μm. Subsequently, an anode transparent electrode 52 is formed on the upper substrate 50 prepared in advance, and then a phosphor 54 that emits light is attached onto the transparent electrode 52. The upper substrate 50 may be a glass substrate, and the transparent electrode may be an indium tin oxide (ITO) electrode. The phosphor 54 is composed of three kinds of phosphors, each of which emits red, green, and blue light. Next, the field emission display device is completed by inverting the upper substrate 50 to which the transparent electrode 52 and the phosphor 54 are attached, placing the upper substrate 50 on the spacer 36, and then sealing and mounting the same by vacuum.

Here, the method of growing the carbon nanotubes in the vertical direction will be described in detail with reference to FIGS. 4 to 6. Figures 4a to 4c is a view for explaining the carbon nanotube growth method of Figure 3, Figure 5 is a schematic diagram of a thermal chemical vapor deposition apparatus used to grow the carbon nanotubes of Figure 3 as an example, Figure 6 A diagram illustrating a mechanism in which carbon nanotubes grow on catalytic metal particles separated by the invention. 4A to 4C show enlarged drawings for convenience.

The carbon nanotubes 34 grown in the vertical direction of FIG. 3 are formed in three steps as shown in FIGS. 4A to 4C. First, a catalyst metal film 33 is formed on the metal film 32 as shown in FIG. 4A. The catalytic metal film is formed using cobalt, nickel, iron, yttrium or alloys thereof (cobalt-nickel, cobalt-iron, cobalt-yttrium, nickel-iron, cobalt-nickel-iron or cobalt-nickel-yttrium). The catalyst metal film 33 is formed on the substrate by a thickness of several nm to several hundred nm, preferably 20 nm to 200 nm, by thermal evaporation, electron beam deposition, or sputtering. Subsequently, as illustrated in FIG. 4B, the surface of the catalyst metal film 33 is etched to form isolated nano-sized catalytic metal particles 33a.

Specifically, after the substrates on which the catalyst metal film 33 is formed are installed side by side to be spaced apart from the boat 310 of the thermal chemical vapor deposition apparatus by a predetermined distance, the boat 310 is a reactor 300 of the thermal chemical vapor deposition apparatus. ) Into the. When the boat 310 is loaded, the surface of the catalyst metal film 33 formed on the substrate 30 is loaded while facing downward while being opposite to the injection direction 315 of the etching gas. After the boat 310 is loaded, the pressure in the reactor 330 is several hundred mTorr to several Torr, and then the temperature in the reactor 300 using the resistance coil 330 installed on the outer wall of the reactor 300. Is raised to 700 ° C to 1000 ° C. When the temperature in the reactor 300 reaches the process temperature, the first valve 410 is opened and the etching gas is supplied from the etching gas supply source 400 into the reactor 300 through the gas supply pipe 320. The etching gas may be ammonia gas, hydrogen gas, or hydride gas. Of these, ammonia gas is preferable as an etching gas. When ammonia gas is used, it is supplied for 10 to 30 minutes at a flow rate of 80 to 400 sccm.

The etching gas supplied into the reactor 300 etches the catalyst metal film 33 along the grain boundary to uniformly and densely the nano-sized catalyst metal particles 33a separated from each other on the surface. Form. Nano size herein refers to a size of several nm to several hundred nm. Depending on the etching conditions, the size and shape of the separated nano-sized catalytic metal particles 33a are different. Depending on the shape of the catalytic metal particles 33a, the shape of the carbon nanotubes 34 formed in a subsequent process is also affected. In the present embodiment, the catalyst metal particles 33a are formed to have a size of 200 nm or less.

Next, a carbon source gas is supplied into the thermal chemical vapor deposition apparatus to grow the carbon nanotubes 34. The growth of the carbon nanotubes 34 and the formation of nano-sized catalytic metal particles 33a may be performed in-situ. Specifically, the first valve 410 of FIG. 6 is closed and the second valve 460 is opened to block the supply of ammonia gas, and react the carbon source gas from the carbon source gas source 450 through the gas supply pipe 320. Supply into furnace 300. The temperature in the reactor 300 is maintained at 700 to 1000 ° C., which is the same temperature range as the temperature at which the nano-sized catalyst metal particles are formed. The carbon source gas is supplied for 10 to 60 minutes at a flow rate of 20 to 200 sccm. The carbon source gas can be used as long as it can decompose at low temperature as it can provide carbon atoms. Preferably used as the carbon source gas, the use of hydrocarbon gas of C ₁ ~ C _20. Preferably, acetylene, ethylene, propylene, propane or methane gas may be used.

To control the growth rate and time of the carbon nanotubes, the third valve 490 is opened and the carrier gas (inert gas such as hydrogen or argon) and / or dilution gas (hydride gas), etc., are opened from the other gas source 480. It may be supplied simultaneously with the carbon source gas. In addition, the etching gas (eg, ammonia gas, hydrogen gas, or hydride gas) may be simultaneously supplied in an appropriate ratio together with the carbon sorbate gas to control the density and growth pattern of the carbon nanotubes. The volume ratio of the carbon source gas and the etching gas is preferably 2: 1 to 3: 1.

As shown in FIG. 6, the carbon source gas (eg, acetylene gas (C ₂ H ₂ )) supplied into the reactor 300 of the thermal chemical vapor deposition apparatus is pyrolyzed in the gas phase to form carbon units ( When C = C or C) and free hydrogen (H ₂ ) are formed, the carbon units are adsorbed on the surface of the catalyst metal particles 33a and then diffused into the inside to dissolve. Subsequently, when the carbon units diffuse and accumulate inside the catalyst metal particles 33a, the carbon nanotubes 34 start to grow. When the carbon units are continuously supplied, the carbon nanotubes 34 grow in the form of bamboo by the catalytic action of the catalytic metal particles 33a. When the catalyst metal particles 33a are round or blunt, the ends of the carbon nanotubes 34 are also rounded or blunt. On the other hand, although not shown in the figure, when the ends of the nano-sized catalyst metal particles 33a are sharp, the ends of the carbon nanotubes are also sharply formed.

In the present invention, amorphous carbon agglomerates are not formed when forming carbon nanotubes because catalyst metal particles suitable for growth of carbon nanotubes are formed independently of each other without being agglomerated with surrounding particles. Thus, high purity carbon nanotubes can be formed and the carbon nanotubes can be aligned perpendicular to the substrate. In addition, the diameter of the carbon nanotubes can be easily adjusted because the size of the catalyst metal particles can be adjusted by changing the etching conditions, ie, the etching conditions by the ammonia gas, for example, the gas flow rate, the etching temperature, and the etching time. The length of the carbon nanotubes can also be easily adjusted by changing the supply conditions of the carbon source gas, such as the gas flow rate, the reaction temperature, and the reaction time.

In this embodiment, the isolated nano-sized catalytic metal particles are formed by dry etching using the thermal chemical vapor deposition apparatus of FIG. 5, but may be formed by wet etching. That is, the substrate on which the catalyst metal film is formed is immersed in a wet etching solution such as hydrogen fluoride (HF) solution to form separated nano-sized catalyst metal particles. Even when wet etching is used, it can be carried out at low temperatures.

In the present embodiment, the catalytic metal particles and the growth of the carbon nanotubes have been described as an example of a horizontal thermal chemical vapor deposition apparatus, but a vertical, in-line or conveyor thermal chemical vapor deposition apparatus may be used as well. to be. In addition, the above-described thermal thermal chemical vapor deposition apparatus is described as an example in the growth of the catalytic metal particles and carbon nanotubes, but a plasma chemical vapor deposition apparatus may also be used. When using the plasma chemical vapor deposition apparatus can be carried out at a low temperature, there is an advantage that the reaction control is easy.

As described above, the field emission display device using the vertically oriented carbon nanotubes according to the present invention has a simple structure with two electrodes, thereby increasing production yield and making it possible to make a large area.

In addition, since the field emission display device according to the present invention uses carbon nanotubes oriented in the vertical direction as the emitter tip, a large emission current can be obtained even at a low operating voltage, for example, 3V / µm or less, and a high tip per unit area. Since it has a density, it is excellent in luminous efficiency and high in reliability.

Claims (12)

A metal film for the cathode electrode formed on the lower substrate; Carbon nanotubes for emitter tips oriented vertically on the metal film; A spacer provided on the metal film; And And an upper substrate provided on the spacer and having a transparent electrode and a phosphor attached on the surface thereof. The field emission display device of claim 1, wherein the lower substrate is a glass, quartz, silicon, or alumina (Al ₂ O ₃ ) substrate. The field emission display device of claim 1, wherein the metal film is a chromium film, a titanium film, a tungsten film, or an aluminum film. The field emission display device according to claim 1, wherein the emitter tip carbon nanotubes are obtained by forming catalyst metal particles on the metal film and growing them on the catalyst metal particles by chemical vapor deposition. Forming a metal film for the cathode electrode on the lower substrate; Growing carbon nanotubes vertically on the metal film; Installing a spacer on the metal film; And And attaching an upper substrate on which the transparent electrode and the phosphor are attached on the spacer. The method of claim 5, wherein the lower substrate is a glass, quartz, silicon, or alumina (Al ₂ O ₃ ) substrate. The method of manufacturing a field emission display device according to claim 5, wherein the metal film is formed of a chromium film, a titanium film, a tungsten film or an aluminum film. The method of claim 5, wherein the growing of the carbon nanotubes by vertical alignment comprises forming a catalyst metal film on the metal film, and etching the surface of the catalyst metal film to form separated nano-sized catalyst metal particles. And growing the emitter tip carbon nanotubes vertically for each of the separated catalytic metal particles by chemical vapor deposition using a carbon source gas. 2. The method of claim 8, wherein a thermal chemical vapor deposition method or a plasma chemical vapor deposition method is used to form the catalyst metal particles and grow carbon nanotubes. The method of claim 8, wherein the carbon source gas is made of acetylene, ethylene, propylene, propane, or methane gas. The method of claim 8, wherein ammonia gas, hydrogen gas, hydride gas, or hydrogen fluoride solution is used to etch the catalyst metal film. The method of claim 8, wherein the catalyst metal film is formed of cobalt, nickel, iron, yttrium, or an alloy thereof.