KR20050073733A - Field emission device and manufacturing method thereof - Google Patents

Abstract

According to the present invention, an inner region of a cathode line where a cell is formed is etched in an undergate structure using carbon nanotubes as a field emission emitter, and a carbon nanotube having a closed curve is formed on the side of the etched inner region to form carbon. The present invention relates to a field emission device capable of improving adhesion of nanotubes and reducing electron beam spreading, and to a method of manufacturing the same, comprising a gate electrode and an insulating layer sequentially formed on a lower substrate (glass substrate), and an upper portion of the insulating layer. And an undercut cathode electrode in which a predetermined region inside is etched to expose a portion of the insulating layer, and carbon nanotubes formed in a closed curve on the side of the etched inner region of the cathode electrode. By improving the adhesion of the carbon nanotubes, a uniform emission current can be obtained, and also the carbon nanotubes are symmetrical. By formation of a closed curve shape, it is capable of improving image quality by reducing the electron beam spreading effect.

Description

FIELD EMISSION DEVICE AND MANUFACTURING METHOD THEREOF

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a field emission device and a method of manufacturing the same, in particular, in an undergate structure using carbon nanotubes as a field emission emitter, an inner region of a cathode line where a cell is formed is etched, The present invention relates to a field emission device and a method of manufacturing the same, which form a closed curved carbon nanotube on the side to improve adhesion of the carbon nanotube and reduce electron beam spreading.

With the rapid development of information and communication technology and the demand for the visualization of diversified information, the demand for electronic displays is increasing and the required display forms are also diversified. For example, in an environment where mobility is emphasized such as a portable information device, a display having a small weight, volume, and power consumption is required, and when used as an information transmission medium for the public, display characteristics of a large viewing angle are required.

In addition, in order to satisfy such demands, electronic displays require conditions such as large size, low price, high performance, high definition, thinness, and light weight, so that light and thin that can replace the existing CRT are required to satisfy these requirements. There is an urgent need for the development of flat panel display devices.

Recently, as the needs of various display devices have been applied to display fields, devices using field emission have been actively developed for thin film displays that can provide high resolution while reducing size and power consumption.

The field emission device is attracting attention as a next-generation information communication flat panel display that overcomes all the disadvantages of flat panel displays (LCD, PDP, VFD, etc.) currently being developed or produced. The field emission device has a simple electrode structure, high-speed operation using the same principle as the CRT, and has the advantages of display such as infinite color, infinite gray scale, high brightness, and high video rate. .

Field emission devices utilize quantum mechanical tunneling which causes electrons to exit the vacuum from the metal or conductor when a high field is applied on the metal or conductor surface (emitter) in the vacuum. At this time, the device exhibits the current-voltage characteristic according to the Fowler-Nordheim law. The field emission device is composed of an anode portion which emits an electron emission source and the emitted electrons collide with each other to emit light, a spacer supporting the upper and lower plates, and a sealing portion for maintaining a vacuum tightness.

Recently, the importance of the field emission device using the carbon nanotubes (CNT) because of the mechanically strong, chemically stable and excellent electron emission characteristics at a relatively low vacuum degree has been recognized. Since such carbon nanotubes have a small diameter (about 1.0 to several tens of nanometers), the field enhancement factor is considerably superior to the conventional microtip type spin emission field emission tips, and thus the emission threshold is low. Since it can be made in a turn-on field (about 1 to 5 [V / μm]), there is an advantage of reducing power loss and production cost.

1 is a cross-sectional view showing an example of the bottom plate structure of a three-electrode field emission device using a conventional carbon nanotube. As shown, the resistive layer 12, the insulating layer 14, and the gate electrode 15 are sequentially formed on the silicon substrate 11, and the gate electrode 15 and the insulating layer 14 are formed by photolithography. After etching a portion to form a hole, the catalyst transition metal layer 13 is formed on the resistive layer 12 at the bottom of the hole through evaporation, and the entire silicon substrate 11 is about 600-900 [deg.] C. The carbon nanotubes 16 are selectively formed only on the catalyst transition metal layer 13 through a thermal chemical vapor deposition method using a hydrocarbon gas or a plasma chemical vapor deposition method by heating to a temperature range. .

In this case, since the carbon nanotubes 16 are selectively formed only on the catalyst transition metal layer 13, the larger the area of the catalyst transition metal layer 13, the larger the area of the carbon nanotubes 16. As such, when the area of the carbon nanotubes 16 increases, the electric field applied through the gate electrode 15 is not concentrated, so that the beam of the emitted electrons is spread and the electron emission region is not even. Only the electron emission is likely to occur locally, and due to an asymmetric electric field distribution, the leakage current to the gate electrode 15 has many problems.

In order to solve the above problems, the structure of the carbon nanotube field emission device having the gate electrode positioned at a lower position than the cathode electrode has been proposed.

FIG. 2 shows a plan view and a cross-sectional view (A-A 'of the plan view) of an example of a bottom plate structure in a field emission device having an under gate structure using a conventional carbon nanotube. As shown, the gate electrode 21 and the cathode electrode 23 on the glass substrate 20 have a matrix structure that is orthogonal to each other with the insulating layer 22 interposed therebetween. The method is applied to the gate electrode 21 under the tube 24.

Referring to the manufacturing process of the bottom plate structure for the field emission device of the undergate structure as follows.

First, an Indium-Tin-Oxide (ITO) transparent electrode is deposited on the glass substrate 20 to a thickness of about 120 nm, and the gate electrode 21 is formed by using a photolithography method. (21) The dielectric powder in the form of a paste is coated on the top by screen printing, and fired at about 580 [deg.] C to form the insulating layer 22.

A conductive metal such as aluminum (Al) or chromium (Cr) is deposited on the insulating layer 22 to a predetermined thickness, and then vertically intersects with the gate electrode 21 using a photolithography method to form the cathode electrode 23. The carbon nanotubes 24 are formed at the edges of the cathode electrode 23.

However, the field emission device having such a structure is difficult to process because the carbon nanotubes need to be positioned at the edges of the cathode electrode, and there is a problem in that image quality is degraded due to large beam spreading.

In addition, due to the paste characteristics of the carbon nanotubes, the adhesive force is deteriorated due to the difference in thermal expansion coefficient between the insulating layer and the cathode electrode during the printing and firing process.

As described above, the field emission device of the undergate structure using the conventional carbon nanotubes has a large electron beam spread and thus degrades the image quality, and the adhesion force of the carbon nanotubes due to the difference in thermal expansion coefficient between the insulating layer and the cathode electrode during the printing and firing process. There was a problem of this deterioration.

Therefore, in view of the above problems, the present invention forms an undercut shape by etching an inner predetermined region of the cathode in the undergate electrode structure, and forms carbon nanotubes having a closed curve on the side of the inner region of the etched cathode electrode. It is an object of the present invention to provide a field emission device and a method of manufacturing the same, which can obtain uniform emission current by improving adhesion of nanotubes.

In addition, an object of the present invention is to provide a field emission device capable of improving the image quality by reducing the electron beam spreading by forming the carbon nanotubes in the form of symmetrical closed curves, and a method of manufacturing the same.

The field emission device of the present invention for achieving the above object comprises a gate electrode and an insulating layer sequentially formed on the lower substrate (glass substrate); An undercut cathode electrode formed on the insulating layer and having a predetermined region etched therein to expose a portion of the insulating layer; It characterized in that it comprises a carbon nanotube formed in a closed curve on the side of the etched inner region of the cathode electrode.

In addition, the etched inner region of the cathode electrode is rectangular or circular, characterized in that formed of a different metal double layer consisting of Al and Cr or Nb and Al or Nb and Cr.

The field emission device manufacturing method of the present invention for achieving the above object comprises the steps of forming a gate electrode by depositing and patterning a metal on the upper substrate (glass substrate), and forming an insulating layer on the gate electrode; Sequentially depositing two different metal layers on the structure, and sequentially etching a predetermined region therein to form an undercut cathode electrode; Depositing and patterning a light blocking metal on the structure to form a light emitting region in an etched inner region of the cathode electrode; Depositing carbon nanotube paste on the structure to form carbon nanotubes in the form of closed curves using a backside photolithography method; And removing a light shielding metal formed on the structure.

In addition, the etching time of the metal layer formed on the lower of the two metal layers is characterized in that the longer than the etching time of the metal layer formed on the upper.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the field emission device of the present invention having the above characteristics and a manufacturing method thereof will be described with reference to the accompanying drawings.

3 is a plan view and a cross-sectional view (B-B 'of the plan view) of the bottom plate structure for the field emission device of the undergate structure using the carbon nanotube of the present invention. As shown, the cathode line 33 of the portion where the cell is formed is etched in a quadrangular form to form an undercut in which a portion of the insulating layer 32 is exposed, and the cathode line 33 of the etched cathode line 33 is formed. Carbon nanotubes 34 are formed on the inner side in a closed curve shape, the gate electrode 31 formed on the glass substrate 30, the insulating layer 32 formed on the gate electrode 31, and the insulation. A cathode electrode 33 having an undercut shape formed on the layer 32 and having a predetermined area therein, and a carbon nanotube 44 formed in a closed curve shape on an etched inner side surface of the cathode electrode 33. ).

The cathode electrode 33 is formed of two layers of different metals, and a metal layer formed on the lower portion is etched more than the metal layer formed on the upper portion to form an undercut, and includes Al and Cr or Nb and Al or Nb and Cr. It can be formed using, the etched shape may be round or oval as well as square.

Since the carbon nanotubes 34 are formed on the etched inner side surface of the cathode electrode 33 formed in the undercut form, adhesion to the insulating layer 32 is improved, and since the carbon nanotubes 34 are formed in a closed curve shape, the electron beam spreading is reduced. To improve picture quality.

Then, the manufacturing process for the field emission device of the present invention having such a structure will be described with reference to the procedure cross section shown in FIG.

As shown in FIG. 4A, an ITO (Indium-Tin-Oxide) transparent electrode is deposited on the glass substrate 30 to a thickness of about 120 [nm], and then a gate electrode 31 is formed using a photolithography method. Then, the paste-type dielectric powder is coated on the gate electrode 31 by screen printing, and then fired at about 580 [deg.] C to form an insulating layer 32 having a thickness of 3 to 20 [micro] m.

Then, as shown in Figure 4b, two different metals (Al / Cr or Nb / Al or Nb / Cr) are sequentially deposited on the structure to form a metal double layer of 0.1 ~ 0.5 [㎛], By using a photolithography method, an internal predetermined region of the metal double layer is sequentially etched by wet etching or dry etching to form an undercut cathode electrode 33. In this case, the metal double layer is deposited by vacuum deposition, sputtering, or the like, and in order to form the cathode electrode 33 undercut (undercut), it is preferable to make the etching time of the metal layer formed on the lower than the etching time of the metal layer formed on the upper side. Do.

Next, as shown in FIG. 4C, the light-shielding metal 35 is deposited on the structure, and as shown in FIG. 4D, the light-shielding metal 35 is etched by using a photolithography method. The tube 34 forms a pattern of light emitting regions to be formed.

Then, as shown in Figure 4e, the negative photosensitive carbon nanotube paste is applied to the upper portion of the structure by the screen printing method, and then irradiated with ultraviolet rays by a photolithography method from the rear of the glass substrate 30, the carbon nanotube developer Is developed by the spray method to form the carbon nanotubes 34.

Finally, as shown in FIG. 4F, when the light shielding metal 35 formed on the structure is removed, and then fired at about 400 [deg.] C, the bottom plate of the field emission device according to the present invention is manufactured.

As described in detail above, the present invention forms an undercut shape by etching an inner predetermined region of the cathode in the undergate electrode structure, and forms a closed curved carbon nanotube on the side of the inner region of the etched cathode electrode. By improving the adhesiveness of the tube has the effect of obtaining a uniform emission current.

In addition, the present invention has the effect of improving the image quality by reducing the electron beam spread by forming the carbon nanotubes in the form of symmetrical closed curve.

1 is a cross-sectional view showing an example of the bottom plate structure of a three-electrode field emission device using a conventional carbon nanotube.

Figure 2 is a plan view and a cross-sectional view showing a bottom plate structure for the field emission device of the undergate structure using a conventional carbon nanotube.

Figure 3 is a plan view and a cross-sectional view showing a bottom plate structure for the field emission device of the undergate structure according to the present invention.

Figures 4a to 4f is a cross-sectional view showing the bottom plate manufacturing process for the field emission device according to the present invention.

** Description of the symbols for the main parts of the drawings **

30: glass substrate 31: gate electrode

32: insulating layer 33: cathode electrode

34: carbon nanotube 35: shading metal

Claims (8)

A gate electrode and an insulating layer sequentially formed on the lower substrate (glass substrate); An undercut cathode electrode formed on the insulating layer and having a predetermined region etched therein to expose a portion of the insulating layer; And a carbon nanotube formed in a closed curve on an etched inner region side of the cathode electrode. 2. The field emission device as claimed in claim 1, wherein the etched inner region of the cathode electrode is rectangular or circular. The field emission device of claim 1, wherein the cathode is formed of a different metal double layer. 4. The field emission device as claimed in claim 3, wherein the cathode is formed of Al and Cr or Nb and Al or Nb and Cr. Depositing a metal on the lower substrate (glass substrate) and patterning the gate electrode to form a gate electrode, and forming an insulating layer on the gate electrode; Sequentially depositing two different metal layers on the structure, and sequentially etching a predetermined region therein to form an undercut cathode electrode; Depositing and patterning a light blocking metal on the structure to form a light emitting region in an etched inner region of the cathode electrode; Depositing carbon nanotube paste on the structure to form carbon nanotubes in the form of closed curves using a backside photolithography method; And removing a light shielding metal formed on the structure. The method of claim 5, wherein the etching time of the metal layer formed at the bottom of the two metal layers is longer than the etching time of the metal layer formed at the top. The method of claim 5, wherein the carbon nanotubes are formed along side surfaces of the cathode electrode. The method of claim 5, wherein the closed carbon nanotubes are formed in a symmetrical shape.