KR20050006926A - Field emission device and fabricating method thereof - Google Patents

Abstract

PURPOSE: A field emission device and a method are provided to reduce costs and improve yield rate by forming the field emission device even without performing a through hole forming process. CONSTITUTION: A field emission device comprises a gate electrode(41) and a cathode electrode(42) formed in the same layer on a glass substrate(40), and a bus electrode formed for one of the gate electrode and the cathode electrode; an insulation layer(43) selectively formed in a portion where the gate electrode and the cathode electrode cross with each other; a conductive bus electrode passing over the insulation layer such that the conductive bus electrode is electrically connected to a part of the gate electrode or the cathode electrode where the bus electrode is not formed; and a carbon nanotube(45) formed on the cathode electrode.

Description

Field emission device and manufacturing method thereof {FIELD EMISSION DEVICE AND FABRICATING METHOD THEREOF}

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a field emission device and a method for manufacturing the same. In particular, a carbon planar device using carbon nanotubes as a field emission emitter and having a gate and a cathode positioned on the same plane does not form a through hole. The present invention relates to a field emission device and a method of manufacturing the same, which can reduce a process time and increase a yield by using a simplified manufacturing process.

Due to 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 appearance is 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 flat panel display for overcoming all the disadvantages of flat panel displays (LCD, PDP, VFD, etc.) currently being developed or produced. The field emitter display has a simple electrode structure, high-speed operation based on the same principle as the CRT, and has the advantages that the display must have such as infinite color, infinite gray scale, high brightness, and high video rate. have.

The field emission display device uses a quantum mechanical tunneling phenomenon in which electrons come out of the vacuum from the metal or conductor when a high field is applied to 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 display 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 seal.

Recently, the importance of field emission devices using carbon nanotubes has been recognized because of their strong mechanical and chemical stability and excellent electron emission characteristics at relatively low vacuum. Since such carbon nanotubes have a small diameter (about 1.0 to several tens of nm), the field enhancement factor is considerably superior to conventional microtip type spin-emitting field emission tips, resulting in low electron emission. Since it can be made in a critical field (turn-on field, about 1 to 5 [V / μm]), there is an advantage that can reduce the power loss and production cost. Referring to the conventional field emission device and a method of manufacturing the same in detail with reference to the accompanying drawings as follows.

FIG. 1 shows a three-electrode structure of a field emission device using a conventional carbon nanotube. As shown in FIG. 1, a resistive layer 2, an insulating layer 4, and a gate electrode 5 are sequentially formed on a silicon substrate 1. ), A portion of the gate electrode 5 and the insulating layer 4 are etched through photolithography to form a hole, and then a catalyst transition metal layer 3 is formed on the resistive layer 2 at the bottom of the hole through evaporation. ), The entire silicon substrate 1 is heated to a temperature range of about 600 to 900 [deg.] C., and thermal thermal vapor deposition or plasma chemical vapor deposition using a hydrocarbon gas. Carbon nanotubes 6 are selectively formed only on the catalyst transition metal layer 3.

In this case, since the carbon nanotubes 6 are selectively formed only on the catalyst transition metal layer 3, the area of the carbon nanotubes 6 also increases as the area of the catalyst transition metal layer 3 increases. As such, when the area of the carbon nanotubes 6 becomes large, the electric field applied through the gate electrode 5 is not concentrated, so that the beam of the emitted electrons is spread and the electron emission region is not even, so only in the vicinity of the hole having the strongest electric field. Local emission of electrons is likely to occur, and the leakage current to the gate electrode 5 is problematic due to an asymmetric electric field distribution.

The structure to have a more mechanical structure while solving the above problems is shown in FIG.

FIG. 2 is a cross-sectional view showing another example of a three-electrode field emission device using conventional carbon nanotubes. As shown in FIG. 2, a screen printing or a thin film pattern on a first substrate 10 may be used. After forming the cathode electrode 11 spaced apart from each other, the carbon nanotube powder is mixed with a binder, a conductive filler, and the like to form a slurry, applied by a method such as screen printing, and a series of binders are removed. Through the process, the carbon nanotubes 12 are exposed on the cathode electrode 11.

A metal grid is formed on the upper part of the resultant product in which the cathode electrode 11 and the carbon nanotube 12 are formed, and a metal grid is formed to be applied to the gate electrode 13, where it is applied to the gate electrode 13. The metal grid to be aligned should be spaced apart from the area where the carbon nanotubes 12 are formed.

Meanwhile, the indium tin oxide (ITO) anode electrode 15 and the light emitting layer 16 are sequentially stacked on the second substrate 14 so as to be uniformly spaced apart, and then the gate electrode 13 is formed on the top of the resultant product. Space is spaced apart, and the light emitting layer 16 is aligned to face the carbon nanotubes 12.

Another example of the three-electrode field emission device using the conventional carbon nanotube as described above is difficult to align the spaced area of the metal grid applied to the gate electrode 13 and the patterned cathode electrode 11. That is, since the gate 13 formed of the metal grid as described above must be formed to be driven independently for each pixel, a small piece of metal structure must be positioned so as to be electrically spaced from adjacent pixels so that the assembly process is very complicated and accurate. Will be difficult to achieve. In addition, since a large amount of electrons emitted from the carbon nanotubes 12 leaks through the gate electrode 13 of the metal grid, there is a problem in that the efficiency of emitted electrons is low.

In order to improve the manufacturing difficulties of the field emission devices using the classical carbon nanotubes as described above, structures of the carbon nanotube field emission devices having gate positions positioned at the same or lower positions of the cathodes have been proposed.

3 is a cross-sectional view of an under-gate structure field emission device using conventional carbon nanotubes, and as shown, an electric field causing electron emission to the gate electrode 21 below the nanotubes 24. It is a way to apply. The gate electrode 21 is formed on the glass substrate 20, and the insulating layer 22 and the cathode electrode 23 are sequentially formed on the glass substrate 20, and then the carbon nanotube mixed slurry is formed on the cathode electrode 23. Is applied by screen printing or the like to form carbon nanotubes 24 through a series of binder removal processes. This is easy to apply to the large-area display portion compared to other conventional methods because the manufacturing process is very simple.

However, in this case, since the gate electrode 21 is positioned below the cathode electrode 24, there is a disadvantage in that the turn-on voltage is relatively high, and abnormal light emission may be caused by the upper anode electrode (not shown). .

4 is a cross-sectional view of a coplanar structure field emission device using a conventional carbon nanotube, in which a gate electrode 33 and a cathode electrode 34 are formed on the same layer. By such a structural arrangement, the turn-on voltage at which the electron emission occurs in the nanotubes 35 is low, and thus the driving voltage may be lowered. However, in order for the gate wiring 31 passing below the cathode electrode 34 to be coplanar with the cathode electrode 34, an insulating layer (eg, an exposure and etching process) may be added to expose a portion of the gate wiring 31. 32, a through hole must be formed and the part must be filled with metal 33.

5A to 5D are cross-sectional views showing a conventional method of manufacturing a coplanar field emission device, and a complicated through hole forming process is required as shown.

First, as illustrated in FIG. 5A, a conductive layer is formed and patterned on the glass substrate 30 to form a gate wiring layer 31. The gate wiring layer 31 serves as a common line connecting the gate electrode.

Next, as shown in FIG. 5B, after forming the insulating layer 32 on the entire upper surface of the formed structure, the insulating layer 32 is etched to expose a portion of the gate wiring layer 31 to form a through hole. .

Next, as shown in FIG. 5C, a conductive layer is formed on the structure to fill the through hole, and a conductive layer is formed on the upper portion of the structure to be patterned to be connected to the gate wiring layer 31 through the through hole. The gate electrode 33, the cathode electrode and the wiring 34 are formed.

Finally, as shown in FIG. 5D, carbon nanotubes are formed on the cathode electrode 34 using screen printing.

As described above, in the conventional method of manufacturing a carbon nanotube field emission device having a coplanar structure, a gate electrode connected to the gate electrode wiring is formed on the same layer as the cathode electrode by using a through hole. However, the formation of the through hole is one of high process difficulty processes, which greatly affects the overall yield.

In the coplanar field emission device using the conventional carbon nanotubes as described above, a process difficulty is required because a through hole is required to form a gate electrode in the same plane as the cathode electrode and then filled with metal. There was a problem that the yield is lowered by a high through-hole forming process.

The present invention has been made to solve the above-mentioned problems, and the present invention provides an insulating film only at a portion where the gate wiring and the electrode and the cathode electrode are formed on the same plane, and where the gate wiring and the cathode wiring to be formed later intersect. It is an object of the present invention to provide a field emission device that simplifies the process by forming a cathode wiring so as to be electrically connected to a part of the cathode electrode while passing through an upper portion of the insulating film after applying the above.

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

Figure 2 is a cross-sectional view showing another example of a three-electrode field emission device using a conventional carbon nanotube.

3 is a cross-sectional view of an undergate structure field emission device using a conventional carbon nanotube.

4 is a cross-sectional view of a coplanar structure field emission device using a conventional carbon nanotube.

5A to 5D are cross-sectional views showing a method of manufacturing a conventional coplanar structure field emission device.

Figure 6a to 6d is a cross-sectional view showing a manufacturing method of an embodiment of the present invention.

Figure 7 is a side view as seen in the cross section of an embodiment of the present invention.

*** Explanation of symbols for main parts of drawing ***

40: glass substrate 41: gate wiring and electrode

42 cathode electrode 43 insulating layer

44: cathode wiring 45: carbon nanotubes

First, the field emission device for achieving the object of the present invention as described above comprises a gate electrode formed on the same layer on the glass substrate, a cathode electrode and a bus electrode formed for one of them; An insulating layer selectively formed at a portion where the gate electrode and the cathode electrode cross each other; A conductive bus electrode electrically connected to a portion of a gate electrode or a cathode of which no bus is formed while passing over the insulating layer; It characterized in that it comprises a carbon nanotube formed on the cathode electrode.

In addition, the present invention includes forming a gate electrode and a cathode electrode simultaneously by forming a conductive material on a glass substrate while forming a bus electrode for one of them on the same layer; Forming an insulating layer on a portion of the formed bus to which another kind of bus to be formed subsequently intersects; Forming a conductive bus electrode which is electrically connected at least partially with the electrode where the bus is not formed and passes over the formed insulating layer; And forming carbon nanotubes on the cathode electrode.

The field emission device and the method of manufacturing the same according to the present invention as described above will be described in detail with reference to an embodiment as follows.

6A to 6D are cross-sectional views showing a method of manufacturing a field emission device according to the present invention, as shown in the steps of simultaneously forming a gate wiring and an electrode 41 and a cathode electrode 42 on the glass substrate 40. Wow; Forming an insulating layer (43) to expose a portion of the cathode electrode (42) while crossing the formed gate wiring in accordance with the positions of the formed cathode electrodes (42); Forming a cathode wiring (44) on the insulating layer (43) so as to be electrically connected to the exposed cathode electrode (42) in part; The carbon nanotubes 45 are formed on a portion of the upper portion of the cathode electrode 42.

The above steps are described in more detail as follows.

First, as shown in FIG. 6A, the gate line, the electrode 41, and the cathode electrode 42 are simultaneously formed by depositing a metal film on the glass substrate 40 and patterning the same by a photolithography process. Note that although the gate wiring is formed on the same plane in this embodiment, the cathode wiring may be formed. That is, in the present invention, the process starts by basically forming a bus electrode for one of these types on the same plane on which the gate electrode 41 and the cathode electrode 42 are formed. Conventionally, although the gate wiring is formed in advance under the layer where the gate electrode and the cathode electrode are formed, and is electrically connected through the through hole, the present invention does not pre-form an electrode that is intersected under the plane where the electrodes are formed at the same time. It is characteristic to form later-wiring wiring later.

Next, as shown in FIG. 6B, the insulating layer 43 intersects with the gate wiring 41 at a position where the cathode electrode 42 is formed for the cathode wiring to be formed to intersect the formed gate wiring 41. ). It is easy to form the insulating layer 43 by a screen printing method, and in this case, a portion of the cathode electrode 42 through which the insulating layer 43 passes is exposed. Of course, the insulating layer 43 may be formed to have a sufficient width only on the upper portion of the gate wiring 41 in the region where the cathode wiring passes. Although it has already been described with reference to FIG. 6A, when the cathode wiring is formed, the insulating layer 43 may be formed in a portion of the cathode wiring to form the gate wiring.

Next, as shown in FIG. 6C, the conductive bus electrode is formed on the formed insulating layer 43 by screen printing to place the cathode wiring 44. The cathode wiring 44 crosses the gate wiring 41. ) Is insulated by the insulating layer 43 and electrically connected to a portion of the cathode electrode 42 to perform a bus function.

As shown in FIG. 6D, carbon nanotubes 45 are formed on the cathode electrode 42.

FIG. 7 is a side view illustrating a cross section taken along the line A-A 'of FIG. 6D, and shows a structure showing the features of the present invention. That is, the gate wiring and the electrode 41 and the cathode electrode 42 are positioned on the same plane on the glass substrate 40, and the cathode wiring 44 connected to the cathode electrode 42 to form a bus structure is The insulating layer 43 formed on the gate wiring 41 is electrically insulated from the gate wiring and the electrode 41. The insulating layer 43 is formed to expose a portion of the cathode electrode 42 so that the cathode wiring 44 is electrically connected to the cathode electrode 42. Alternatively, the insulating layer 43 may be formed only in an area where the gate wiring 41 and the cathode wiring 44 intersect.

As described above, the present invention enables to manufacture a field-emitting device having a coplanar structure through a screen printing method which is relatively easy to process without forming a through hole, thereby increasing the yield in mass production.

As described above, the field emission device and the method of manufacturing the same according to the present invention form a gate electrode and a cathode electrode on the same plane, and selectively form an insulating layer on the portion where the gate electrode and the cathode electrode intersect by screen printing. Through forming a conductive bus electrode on the insulating layer formed on the intersection portion, it is possible to electrically separate the bus structure of the gate electrode and the cathode electrode which cross each other without forming the through hole, thereby penetrating through the complicated photolithography process. It is possible to form the field emission device of the coplanar structure by an easy process without going through the hole forming process, thereby increasing the process cost and yield.

Claims (5)

A gate electrode formed on the same layer on the glass substrate, a cathode electrode and a bus electrode formed on one of them; An insulating layer selectively formed at a portion where the gate electrode and the cathode electrode cross each other; A conductive bus electrode electrically connected to a portion of a gate electrode or a cathode of which no bus is formed while passing over the insulating layer; A field emission device comprising carbon nanotubes formed on the cathode electrode. The gate electrode of claim 1, wherein the gate electrode formed on the same layer is connected on the same plane through a bus electrode, and the cathode electrode is connected to a cathode bus electrode passing over the insulating layer formed on a portion of the gate electrode bus. A field emission device. Forming a gate electrode and a cathode electrode at the same time by forming a conductive material on a glass substrate while forming a bus electrode for one of them on the same layer; Forming an insulating layer on a portion of the formed bus to which another kind of bus to be formed subsequently intersects; Forming a conductive bus electrode which is electrically connected at least partially with the electrode where the bus is not formed and passes over the formed insulating layer; And forming carbon nanotubes on the cathode electrode. The method of claim 3, wherein the insulating layer and the conductive bus electrode are formed by a screen printing method. The method of claim 3, wherein the forming of the gate electrode and the cathode electrode simultaneously comprises forming a gate electrode and a gate bus electrode connecting the gate electrode in common, and a cathode electrode spaced apart from the gate electrode for electroluminescence. And forming the insulating layer by insulating a portion of the gate bus electrode in accordance with a position where the cathode electrode is formed, and forming an insulating material by screen printing to expose the cathode electrode. And forming a cathode bus electrode by a screen printing method on the formed insulating layer and electrically connected to the exposed cathode electrode.