KR20060098225A - Method for forming electron emitter tip by copper-carbon nanotube composite electroplating - Google Patents

Abstract

 Disclosed is a method of forming an electron-emitting tip used in a field emission device using a composite plating of carbon nanotubes and copper. In the method of forming an electron-emitting tip of the present invention, a cathode substrate having a copper seed layer defined on a surface thereof is immersed in a plating bath filled with a plating solution containing a carbon nanotube and a copper electrolyte together with an anode substrate, and then applied power to the cathode substrate and the anode substrate. Carbon nanotubes and copper are plated on the negative electrode substrate to form an electron emission tip. Electron emitting tips can be formed using composite plating of carbon nanotubes and copper to form field emission devices with excellent adhesion between carbon nanotubes and substrates, and field emission devices with high brightness, low power consumption, and long lifetime are formed. can do.

Carbon nanotube, electron emission, display device, light source, composite plating

Description

Method for forming electron emitter tip by copper-carbon nanotube composite electroplating}

1 is a schematic view showing a plating bath for composite plating of carbon nanotubes and copper according to the present invention.

Figure 2 is a photograph showing a composite plating structure of carbon nanotubes and copper according to the first embodiment of the present invention.

3 and 4 are photographs showing a composite plating structure of carbon nanotubes and copper according to a second embodiment of the present invention.

5 is a photograph showing a composite plating structure of carbon nanotubes and copper according to a third embodiment of the present invention.

6 is a photograph showing a composite plating structure of carbon nanotubes and copper according to a fourth embodiment of the present invention.

7 and 8 are photographs showing the degree of light emission according to the frequency characteristics of the composite plating of carbon nanotubes and copper according to an embodiment of the present invention.

9 to 12 are diagrams for explaining an embodiment of manufacturing an FED having a general gate structure using an electron emission tip made of carbon nanotubes and copper according to the present invention.

13 to 15 are cross-sectional views illustrating a second embodiment of fabricating an FED having a general gate structure using an electron emission tip according to the present invention.

16 to 19 are cross-sectional views for explaining an embodiment of manufacturing the FED of the lower gate structure using the electron-emitting tip according to the present invention.

20 and 21 are cross-sectional views illustrating a first embodiment of manufacturing a white light source using a composite plating of an electron emission tip according to the present invention.

22 to 24 are cross-sectional views illustrating a second embodiment of manufacturing a white light source using an electron emission tip according to the present invention.

The present invention relates to a method of forming an electron emitting tip, and more particularly to a method of forming an electron emitting tip using a composite plating of carbon nanotubes and copper.

Display devices such as FED (Field Emission Display), VFD (Vacuum Fluorescent Display), CRT (Cathod Ray Tube), or light sources such as white light source and backlight lamp of LCD (Liquid Crystal Display), There is a need for an emitter tip that emits.

A field emission device using an electron emission tip is mainly composed of an upper substrate having an anode coated with an indium tin oxide (ITO) phosphor and a lower substrate having an anode having an electron emitting tip.

Recently, carbon nanotubes having electron emission voltages of several tens of times lower than electron emission currents of several tens to several tens of times have been spotlighted as new electron emission tips. In order to form carbon nanotubes with electron emitting tips, high purity and high density should be formed at low temperature, and the tip shape of electron emitting tips should be as sharp as possible in order for electron emission to occur easily.

Currently, a method of using carbon nanotubes as an electron emission tip is a method of forming a carbon nanotube film by printing a paste composed mainly of metal, an organic polymer and carbon nanotubes on a lower substrate, and then patterning them by selective etching and carbon nanotubes. Is dispersed in a solvent together with a charging agent to form an electron emitting tip by electrophoresis.

However, the method using the paste shortens the life of the device due to the outgassing of the paste, not the carbon nanotubes, and the number distribution of the effective nanotubes for the electron emission is poor, especially between the electrode substrate and the nanotubes. Since the adhesive force is poor, there is a disadvantage in that light emission of uniform brightness cannot be generated and it cannot be used for a long time. In the case of the method using the electrophoresis method, a phenomenon in which carbon nanotubes fall in the high electric field due to the weak adhesion to the substrate is required, and there is a need for a method for improving the adhesion.

 The present invention has been made to solve the above problems, to provide a method of forming an electron-emitting tip that can be used for a long time by forming a carbon nanotube film that is excellent in adhesion with the electrode substrate and arranged in a high density The purpose is to.

In addition, it is an object of the present invention to provide a method for forming an electron emitting tip capable of forming the electron emitting tip at a high density at a temperature lower than the deformation temperature of the substrate.

In order to achieve the above object, the method of forming an electron-emitting tip of the present invention is a negative electrode substrate and after dipping a negative electrode substrate with a copper seed layer defined on the surface in a plating bath filled with a carbon nanotube and a copper electrolyte solution together with the positive electrode substrate and Power is applied to the cathode substrate to form an electron emission tip by complex plating of carbon nanotubes and copper on the anode substrate.

In the present invention, the copper electrolyte is composed of copper sulfate, sulfuric acid, hydrochloric acid, the power source is a pulse voltage, the current density can proceed to 20mA / cm ² or more, the frequency 10Hz ~ 5,000Hz, the source of copper plating is copper electrolyte It is a copper ion in the.

In the present invention, the electron emission tip may be an electron emission tip of a field emission display or an electron emission tip of a backlight of a field emission method.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Shapes and thicknesses of the layers and materials in the drawings are exaggerated or outlined for convenience of description. Like reference numerals refer to like elements throughout.

1 is a schematic view showing a plating bath for composite plating of carbon nanotubes and copper according to the present invention.

Referring to FIG. 1, the plating bath 1 is filled with a plating liquid 15 at a predetermined level, and a cathode substrate 25 in which a positive electrode substrate 20 and an electron emission tip are formed is contained in the plating solution 15. An electric field may be applied between the positive electrode substrate 20 and the negative electrode substrate 25 by the power supply device 30. For the positive electrode substrate 20, a copper substrate can be used as a source of copper, or a metal other than copper (for example, tungsten or the like) was used. As the negative electrode substrate 25, all currently used substrates such as soda-lime glass and silicon wafer can be used, and the size of the substrate is not limited. A seed layer for plating may be formed on the negative electrode substrate 25 using a sputtering method, a thermal evaporation method, or an electroplating method.

The plating solution 15 consists of copper sulfate (90 g / L), sulfuric acid (197 g / L), hydrochloric acid (0.1 g / L), or a mixture of copper cyanide, sodium cyanide and loxel salt. 35) is added. The carbon nanotubes 35 have a pointed shape having a diameter of a nanometer thickness in which thermal, chemical, and mechanical properties are stable.

Hereinafter, a composite plating method of carbon nanotubes and copper will be described using such a plating bath.

DC plating and pulse plating were used as the plating method. In particular, in the case of pulse plating, the duty ratio, on / off ratio, and on 20% are on. The time is 20%), 1-100%, and the frequency progressed from low to high frequency in the range of 10 Hz to 5,000 Hz. Current density was tested by a ^{20 mA / cm 2 ~ 100mA /} cm 2.

In practice, there are various variables in the plating method, and in this experiment, the plating characteristics depend on agitation strength, time, temperature, concentration of copper sulfate solution, current density, duty ratio during pulse plating, frequency, and presence or absence of copper source on the anode substrate. This change was confirmed.

Example 1

At a current density of 53 mA / cm ² and the plating solution was not stirred, plating was performed on the positive electrode substrate using a copper source. The duty ratio was 33% and the frequency was used at 100 Hz.

 Figure 2 is a photograph showing a composite plating structure of carbon nanotubes and copper according to the first embodiment of the present invention.

Referring to FIG. 2, when the current density is 50 mA / cm ² or more, composite plating of carbon nanotubes is well performed. In high current density plating, when a copper source is present on the anode (+) substrate, it is formed in the same manner as a general copper plated thin film, but the sharp shape of the carbon nanotubes does not appear.

Example 2

The current density was 53 mA / cm ² and plating was performed on the positive electrode substrate without using a copper source while the plating solution was not stirred. The duty ratio was 33% and the frequency was used at 100 Hz. In contrast to the first embodiment, copper is not used for the positive electrode substrate.

3 and 4 are photographs showing a composite plating structure of carbon nanotubes and copper formed according to the second embodiment of the present invention.

Referring to FIGS. 3 and 4, when the current density is 50 mA / cm ² or more, the composite plating of carbon nanotubes and copper is well performed, and a first embodiment in which the copper source is present on the anode (+) substrate in high current density plating is performed. Compared with the example, in the absence of copper source, the composite plating structure was different from that of the first embodiment, and it was found that the composite plating of carbon nanotubes and copper was well performed. In particular, when the frequency was increased in the pulse plating, it was confirmed that the uniformity (uniformity) of the plating thin film was increased and the moving speed of the carbon nanotubes in the copper sulfate solution was further increased.

Example 3

The current density was 40 mA / cm ² and plating was performed using a copper source for the positive electrode substrate while the plating solution was not stirred. The duty ratio was 33% and the frequency was used at 100 Hz. In the third embodiment, the current density is reduced while copper is used for the anode substrate.

5 is a photograph showing a composite plating structure of carbon nanotubes and copper according to a third embodiment of the present invention.

Referring to FIG. 5, when the current density is 40 mA / cm ² , when a copper source is used for an anode (+) substrate, a structure having the same shape as a general copper plating thin film is formed, and a composite plating of carbon nanotubes and copper is formed. Could not confirm. That is, in the case where the copper source is present in the anode substrate, it was confirmed that the composite plating of carbon nanotubes and copper does not occur well at low current density.

Example 4

The current density was 40 mA / cm ² , and plating was performed without using a copper source for the anode electrode while the plating solution was not stirred. The duty ratio was 33% and the frequency was used at 100 Hz. That is, in the fourth embodiment, the current density is lowered without using copper as the anode electrode.

6 is a photograph showing a composite plating structure of carbon nanotubes and copper according to a fourth embodiment of the present invention.

Referring to FIG. 6, when the current density is 40 mA / cm ² , when a copper source is not used for the anode (+) substrate, a structure having a shape different from that of a general copper plating is formed. Multiple plating was found in part. However, if enough time passed, it was possible to check the composite plating of carbon nanotubes and copper as a whole rather than a part of them.

Example 5

The other process conditions were kept the same, and composite plating of carbon nanotubes and copper was performed when only the frequency characteristics were changed.

 7 and 8 are photographs showing the degree of emission according to the frequency characteristics of the composite plating of carbon nanotubes and copper according to an embodiment of the present invention, Figure 7 is a light emission at a low frequency (about 100Hz), Figure 8 It is a photograph showing light emission at a high frequency (about 1,000 Hz).

Referring to FIGS. 7 and 8, the uniformity of the composite plating of carbon nanotubes and copper was inferior at low frequencies. When carbon nanotubes and copper were plated together, it was found that the edges of the substrate were plated relatively more than the other regions due to the strong electric field at the edges of the substrate. On the other hand, the uniformity of the composite plating of carbon nanotubes and copper was high at high frequency conditions. That is, the electron-emitting device plated with the electron-emitting tip under high frequency condition showed uniform light emission.

Hereinafter, embodiments of manufacturing a display device or a light source using an electron emission tip formed of a composite plating of carbon nanotubes and copper according to the present invention will be described. Although the display device is described with an FED as a light source and a white light source as an example, it is apparent to those skilled in the art that it is applicable to other display devices or light sources.

The FED is usually manufactured in a triode structure to easily control electron emission. The triode structure includes an under gate structure in which a gate electrode is disposed below a cathode electrode with an insulating layer interposed therebetween, and a gate electrode. The insulating layer may be divided into a normal gate structure positioned above the cathode electrode.

9 to 12 are cross-sectional views illustrating an embodiment of manufacturing an FED having a general gate structure using an electron emission tip made of carbon nanotubes and copper according to the present invention.

Referring to FIG. 9, the first insulating layer 110 is formed on the lower substrate 100 having a large area. As the lower substrate 100, a glass, quartz, silicon, or alumina (Al ₂ O ₃ ) substrate is used. The first insulating layer 110 is formed to prevent the cathode electrode 200 and the lower substrate 100 formed in a subsequent process from reacting with each other. If necessary, the formation of the first insulating layer 110 may be omitted. The cathode electrode 200 is formed using a chromium film, a titanium film, or a tungsten film.

Subsequently, a copper film 300 is formed on the cathode electrode 200. The copper film 300 is formed to be several nm to several hundred nm thick, preferably 400 nm to 500 nm thick by thermal evaporation, electron beam deposition, or sputtering. Subsequently, a second insulating film 310 is formed on the copper film 300, and then a metal film 320 for a gate electrode is formed on the second insulating film 310. The gate electrode metal film 320 is made of chromium, titanium, or palladium. The gate electrode metal film 320 is formed by an electron beam deposition method, a thermal deposition method, or a sputtering method. Preferably, the process of forming the first insulating film 110, the cathode electrode 200, the copper film 300, the second insulating film 310, and the metal film 320 for the gate electrode is modified in the lower substrate 100. Proceed below temperature.

Referring to FIG. 10, a photoresist film is coated on the gate electrode metal film 320 and then photographed to form a photoresist pattern PR. Subsequently, the gate electrode metal layer 320 is etched using the photoresist pattern PR as a mask to form the gate electrode 320a. The gate electrode 320a defines a hole H exposing the surface of the second insulating layer 310. The holes H are preferably formed to have a diameter of about 0.8 to 5.0 μm and the spacing between the holes H to be about 3.0 to 15.0 μm.

Referring to FIG. 11, after removing the photoresist pattern PR, the second insulating layer 310 is etched using the gate electrode 320a as an etch mask to form a second insulating layer pattern 310a. The surface of the copper film 300 is exposed by the second insulating film pattern 310a. In some cases, the second insulating layer pattern 310a is formed by using the photoresist pattern PR and the gate electrode 320a together as an etching mask without removing the photoresist pattern PR, and then the photoresist pattern PR Can be removed.

Subsequently, the electron emission tips 400 may be formed on the resultant in which the second insulating layer pattern 310a is formed by using the above-described composite plating of carbon nanotubes and copper.

Referring to FIG. 12, a spacer 500 is installed on the gate electrode 320a.

Subsequently, after the anode electrode 700 is formed on the upper substrate 600 prepared in advance, a phosphor 800 that emits light is attached to the anode electrode 700. The phosphor 800 may be a red phosphor such as Y ₂ O ₂ S: Eu, Gd ₂ O ₃ : Eu, Y ₂ O ₃ : Eu, Gd ₂ O ₂ S: Tb, SrGaS ₄ : Eu, ZnS: Cu, Cl, Green phosphors such as Y ₃ Al ₅ O ₁₂ : Tb, Y ₂ SiO ₅ : Tb, and blue phosphors such as ZnS: Ag, Me, and Y ₂ SiO ₅ : Ce. The upper substrate 600 is made of a transparent material, for example, glass, to emit light emitted from the phosphor 800 to the outside. The anode electrode 700 is formed of a transparent material such as indium tin oxide (ITO).

Subsequently, the FED is completed by inverting the upper substrate 600 to which the anode electrode 700 and the phosphor 800 are attached, placing the upper substrate 600 on the spacer 500, and then sealing and mounting the same by vacuum. As a result, the phosphor 800 and the vacuum discharge tip 400 formed on the upper substrate 600 are disposed to be spaced apart by a predetermined distance from the spacer 500.

When a constant voltage (tens V) is applied between the FED gate electrode 320a and the cathode electrode 200, electrons are emitted through quantum mechanical tunneling from the electron emission tip 400 made of carbon nanotubes. . The emitted electrons collide with the phosphor 800 by a larger voltage (hundreds of thousands to thousands of volts) applied to the anode electrode 700 and the electrons in the phosphor 800 are excited by the energy of the collided electrons. Generates light as it falls. The FED shown in FIG. 12 is a three-pole FED having three electrodes 200, 320a and 700. Of course, the manufacturing method according to the present invention can also be applied to a bipolar FED having two electrodes.

13 to 15 are cross-sectional views illustrating a second embodiment of fabricating an FED having a general gate structure using an electron emission tip according to the present invention. Forming methods, thicknesses, shapes, sizes, materials, and the like of the same components as those in the first embodiment are omitted to avoid duplication of description.

Referring to FIG. 13, unlike the first exemplary embodiment, the cathode electrode 200, the insulating layer 310, the gate electrode metal layer 320, and the photo are not formed on the lower substrate 100 having a large area without forming a copper layer. After the resist pattern PR is formed in order, the gate electrode metal film 320 and the insulating film 310 are sequentially etched using the photoresist pattern PR as an etching mask to sequentially form the gate electrode 320a and the insulating film pattern 310a. ). As a result, the surface of the cathode electrode 200 is exposed.

Referring to FIG. 14, a copper film 300 is formed on the entire surface of the resultant product of FIG. 13. As a result, the copper film 300 is formed on the surface of the photoresist pattern PR and the cathode electrode 200.

Referring to FIG. 15, the copper film 300 is disposed only on the surface of the cathode electrode 200 by removing the photoresist pattern PR and the copper film 300 deposited on the surface thereof by using a lift-off process. Leaves. Subsequently, the electron emission tip 400 is completed by using the above-described composite plating of carbon nanotubes and copper. Subsequently, as described in the first embodiment, the spacer is formed, and the FED is completed by mounting the upper substrate on which the anode electrode and the phosphor are stacked on the spacer, and sealing the same by vacuum.

16 to 19 are cross-sectional views for explaining an embodiment of manufacturing the FED of the lower gate structure using the electron-emitting tip according to the present invention. The lower gate structure is a structure in which a cathode electrode is disposed between the gate electrode and the fluorescent film.

Referring to FIG. 16, a gate electrode 325, an insulating film 315, and a cathode electrode 305 are sequentially stacked on the lower substrate 100 having a large area.

Referring to FIG. 17, after the photoresist pattern PR is formed on the cathode electrode 305, the cathode electrode 305a is patterned using the photoresist pattern PR as an etching mask.

Referring to FIG. 18, after the photoresist pattern PR is removed, the insulating layer is selectively etched using the patterned cathode electrode 305a as an etching mask until the gate electrode 325 is exposed. Although not shown in the drawing, the photoresist pattern used for patterning the cathode electrode described above may be used as an etching mask for patterning the insulating film 315a.

Referring to FIG. 19, the electron emission tip 405 is completed by using the above-described composite plating of carbon nanotubes and copper on the patterned cathode electrode 305a.

Subsequently, the FED is completed by forming a spacer, placing the upper substrate on which the anode electrode and the phosphor are stacked on the spacer, and then sealing and mounting the same by vacuum.

20 and 21 are cross-sectional views illustrating a first embodiment of manufacturing a white light source using a composite plating of an electron emission tip according to the present invention.

Referring to FIG. 20, the cathode electrode 200 and the copper film 300 are sequentially formed on the lower substrate 100. Subsequently, the electron emission tip 400 is formed using a composite plating of carbon nanotubes and copper. Subsequently, a spacer 500 is formed on the copper film 300 on which the electron emission tip 400 is formed.

Referring to FIG. 21, after forming the transparent electrode 700 and the phosphor 800 on the upper substrate 600, the upper substrate 600 is placed so that the surface of the phosphor 800 faces the electron emission tip 400. Place it on the spacer 500. The phosphor 800 is formed using a fluorescent material that generates white light emission, for example, a fluorescent material that generates short wavelength white light emission such as 3Ca ₃ (PO ₄ ) CaFCl / Sb, Mn. Subsequently, it is sealed and mounted in vacuum to complete a white light source.

When a predetermined voltage is applied between the cathode electrode 200 and the anode electrode 700 of the white light source manufactured as described above, electrons are emitted from the electron emission tip 400.

22 to 24 are cross-sectional views illustrating a second embodiment of manufacturing a white light source using an electron emission tip according to the present invention. The second embodiment differs from the first embodiment in that the electron emission tips 400 are grouped to form one cell for each group.

Referring to FIG. 22, the first insulating layer 110, the cathode electrode 200, the copper layer 300, and the second insulating layer 310 are sequentially formed on the lower substrate 100, and then a conventional photolithography process is performed. The second insulating film pattern 310a defining a plurality of holes H exposing the lower copper film 300 is selectively patterned by using a method. In this case, each of the holes H forms the second insulating layer pattern 310a to have a diameter and an interval suitable for defining one cell.

Referring to FIG. 23, an electron emission tip 400 is formed on the copper film 300 exposed by the hole H of the insulating film pattern 350 by using a carbon nanotube and copper composite plating. The spacer 500 is formed on the second insulating layer pattern 310a on which the electron emission tip 400 is formed.

Referring to FIG. 24, the upper substrate 600 on which the anode electrode 700 and the phosphor 800 are stacked is mounted on the spacer 500 so that the phosphor 800 faces the electron emission tip 400, and then vacuum-sealed and mounted. To complete the white light source. At this time, it is preferable that the phosphor 800 is also patterned to expose a portion of the transparent electrode 700 at a position to be supported by the spacer 500.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible in the art without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

The present invention made as described above, by using the composite plating of carbon nanotubes and copper to form an electron emission tip can form a field emission device excellent in adhesion between the carbon nanotubes and the substrate.

In addition, since the plating method is used, it is possible to solve the gas release problem caused by the organic binder generated in the conventional paste method.

In addition, it is possible to form a field emission device having high brightness, low power consumption, and long life.

Claims (7)

Providing a cathode substrate having a copper seed layer defined on a surface thereof; Dipping the anode substrate in a plating bath filled with a plating solution including a carbon nanotube and a copper electrolyte together with the cathode substrate; And And applying a power to the cathode substrate and the anode substrate to complex plating carbon nanotubes and copper on the anode substrate. The method of claim 1, The copper electrolyte is a method of forming an electron-emitting tip, characterized in that consisting of copper sulfate, sulfuric acid, hydrochloric acid. The method of claim 1, In the composite plating of the carbon nanotubes and copper, A source of copper plating is a method for forming an electron-emitting tip, characterized in that the copper ion in the copper electrolyte. The method of claim 1, The power source is a pulse voltage, the current density is 20mA / cm ² or more, the frequency is 10Hz to 5,000Hz, the method of forming an electron emitting tip characterized in that proceeding. The method of claim 4, wherein Wherein the power source is a pulse voltage, when the current density is 20mA / cm ² or more, the composite plating of carbon nanotubes and copper increases with time elapsed. The method of claim 1, The electron emitting tip is a method of forming an electron emitting tip, characterized in that the electron emitting tip of the field emission display. The method of claim 1, The electron emission tip is a method of forming an electron emission tip, characterized in that the electron emission tip of the backlight of the field emission (field emission) method.

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