KR100372168B1 - A method for manufacturing gated carbon-nanotube field emission displays - Google Patents

Abstract

The present invention relates to a method of manufacturing a tripolar field emission display device that can control the flow of electrons by using carbon nanotubes grown directly on a lower substrate having a fine hole of several micrometers in size or less as a field emission source. The method of manufacturing a field emission display device including a transparent electrode and a lower substrate formed to correspond to an upper substrate on which a light emitting layer is formed, the method comprising: forming a gate insulating film and a gate electrode on a lower substrate in order and exposing a predetermined portion of the gate insulating film. Selectively etching the gate electrode, forming a hole by wet etching the gate insulating layer with a dry etching so as to expose a predetermined portion of the surface of the substrate, and conducting a predetermined inclination using an electron beam evaporator on the gate electrode. Forming a layer, and the ultra-thin catalyst gold on the conductive layer and the substrate of the hole After depositing the inner layer, using a chemical vapor deposition method to selectively form a carbon nanotube in the center of the hole, and the lift-off process to remove the conductive layer by a tripolar type having a carbon nanotube directly grown on the substrate A field emission display device is formed.

Description

A method for manufacturing a field emission display device of tripolar carbon nanotubes {A METHOD FOR MANUFACTURING GATED CARBON-NANOTUBE FIELD EMISSION DISPLAYS}

The present invention relates to a method for manufacturing a field emission device (FED), in particular using carbon nanotubes grown directly at a selective position on a substrate on which a fine hole having a diameter of several micrometers is formed, as an electron emission source, A method of manufacturing a field emission display device of tripolar carbon nanotubes having a gate for controlling the flow of electrons.

In general, carbon nanotubes are the next-generation new material materials that have received great attention since their unusual electrical and mechanical properties have been known since the discovery by Professor Ijima Japan in 1991.

Carbon nanotubes are characterized by high aspect ratios ranging from several nm to several tens of nanometers in diameter and from several to tens of micrometers in length, with high electron emission efficiencies, good heat release properties, better electrical conductivity than copper, and complete mechanical In addition to structural features, many studies have been conducted on the durability of ion collision in high vacuum.

In addition, carbon nanotubes exhibit high coherence and narrow field emission energy distribution, and thus may be used as electron emission sources with higher resolution than conventional electron emission sources.

Recently, Saito et al. Manufactured cathode-ray tubes using multiwall carbon nanotubes (MWNTs) as electron sources, which are more than 100 times higher than those of conventional hot electron tubes. The operating life of about 8000 hours has proved that carbon nanotubes are very good electron emission sources.

Meanwhile, Zhou Group demonstrated a microwave generator that can operate in the current density of 0.1A / cm ² and frequency band 0.5 ~ 3GHz using 5mm diameter single wall carbon nanotubes (SWNT). have.

The application of carbon nanotubes as field emission displays was presented by Wang et al., 32 × 32 matrix-addressable display devices, and SAIT et al. Mix carbon nanotubes with conductive epoxy and use screen printing. The company announced a 4.5-inch and 9-inch color field emission display.

In these prior arts, the carbon nanotube electron-emitting cathode is a mixture of organic binder and metal powder, pressed and pushed into a patterned metal network by heating the purified carbon nanotube, heating and removing the organic binder, and then mixed with a binder. Carbon nanotube electron emission sources were prepared by subjecting the carbon nanotubes to be exposed on the surface. Here, the density of the exposed carbon nanotubes in the matrix mixed with the binder is 3 to 7 / ㎛ ² , a current of several pA (pico ampere) per carbon nanotube is emitted.

On the other hand, in order to maximize the field emission effect in the electron emission source using a conventional metal and silicon-tip (Si-tip) to produce a tip of 1 ~ 1.5㎛ height, the tip (apex) of the processed tip (tenx ~ 10nm) There is a need for highly difficult MEMS techniques, such as controlling to have a 30 nm diameter. In addition, the uniformity control of the tips manufactured in this way is not only very low in the process, but also deterioration characteristics such as oxidation and mechanical agglomeration of the tip tip due to prolonged operation under high electric field, and the increase in product cost resulting from the commercialization of the field emission display device. Has become a big stumbling block.

Hereinafter, a conventional field emission display device will be described with reference to the accompanying drawings.

1 is a cross-sectional view showing a conventional field emission display device, and FIG. 2 is a cross-sectional view showing a conventional bipolar (diode type) field emission display device.

First, as shown in FIG. 1, a three-pole triode composed of a cathode-gate-anode forms a cathode 2 on a lower substrate 1 and the cathode 2 on the cathode 2. And the insulating film 3 is formed so as to be insulated from the semiconductor tip 5 to be formed in a later step, and then a hole is formed.

Subsequently, a sharp shape semiconductor (metal) tip 5 is formed on the cathode 2 so as to be spaced apart at a predetermined interval. In this case, the lower substrate 1 uses a glass or semiconductor substrate.

The gate electrode 4 is formed on the insulating film 3.

Meanwhile, the transparent electrode 7 and the light emitting layer 8, which are anodes, are formed inside the upper substrate 6 at the corresponding position, and the two substrates are separated at regular intervals between the lower and upper substrates 1 and 6. A space 9 which serves to maintain the vacuum gap is formed.

Therefore, when a voltage is applied between the cathode 2 and the gate electrode 4 with the insulating film 3 interposed with respect to the cathode 2 of the device, electrons are generated from the sharp end of the semiconductor tip 5. These emitted electrons are accelerated by a stronger constant voltage (anode voltage) across the vacuum and impinge on the screen of the light emitting layer 8 to excite the light emitter to generate visible light.

At this time, the brightness of the light is adjusted by changing the voltage applied to the gate electrode 4 by changing the density of emission electrons reaching the light emitting layer 8 and the like.

As shown in FIG. 2, the diode-type field emission device forms a cathode 2 on the lower substrate 1, and an emitter portion in the form of a thin film or a thick film on the cathode 2. To form (10).

Meanwhile, the transparent electrode 7 and the light emitting layer 8, which are anodes, are formed inside the upper substrate 6 at a position corresponding thereto, and the two substrates are separated at regular intervals between the lower and upper substrates 1,6. The spacer 9 is formed.

On the other hand, display applications using carbon nanotubes (CNT) use a diode structure that is easy to implement without the development of selective growth technology within a specific location. That is, the carbon nanotubes are grown in a thin film form on a planar substrate, or more simply, are mixed with CNT and a conductive epoxy and coated on the substrate, and then light is applied by applying a voltage between the cathode and the upper anode.

However, the former can not be used as a driveable display for useful structures or image and information processing in terms of academic aspects such as CNT material itself, growth condition studies, emission characteristics studies, and the like.

In addition, even if the CNT powder system mixed with epoxy is used, the display device can be manufactured by a low-cost process, but the lifetime is deteriorated due to the gas discharge over the operating time in the FED operating while maintaining a high vacuum in a narrow gap. And non-uniformity of display quality and low resolution due to thick film process are pointed out as problems for the possibility of next generation high resolution display products.

The present invention has been made to solve the above problems to provide a method of manufacturing a tripolar field emission display device having a gate while forming a new electron emission source excellent in electron emission characteristics and mechanical strength in a narrow hole on the substrate. The purpose is.

In addition, a field emission display device is fabricated so that an electron emission source having a high aspect ratio can be directly grown at a specific position inside a hole having a diameter of 1 μm without using a high-etch etching process to develop a high-performance, low-cost, high performance next-generation flat panel display The purpose is to provide a method.

1 is a cross-sectional view showing a conventional field emission display device

2 is a cross-sectional view showing a conventional diode type field emission display device.

3A to 3F are cross-sectional views illustrating a method of manufacturing a field emission display device according to an exemplary embodiment of the present invention.

4a to 4c are views showing the structure of the completed device according to an embodiment of the present invention

<Explanation of symbols for the main parts of the drawings>

100: lower substrate 101: gate insulating film

102 gate electrode 103 hole

104: aluminum layer 105: catalytic metal

106: carbon nanotube

In the method of manufacturing a tripolar carbon nanotube field emission display device of the present invention for achieving the above object, in the method of manufacturing a field emission display device comprising a transparent electrode, a lower substrate formed to correspond to the upper substrate on which the light emitting layer is formed, Forming a gate insulating film and a gate electrode sequentially on a lower substrate, and selectively etching the gate electrode to expose a predetermined portion of the gate insulating layer, and wet etching and dry the gate insulating layer to expose a predetermined portion of the substrate surface. Forming a conductive layer on the gate electrode by using an electron-ray deposition method, and depositing an ultra-thin catalyst metal on the conductive layer and the substrate of the hole, followed by thermochemical vapor deposition. Selectively depositing / growing carbon nanotubes in the center of the hole by vapor deposition; The conductive layer may be removed through a FT-off process to form a tripolar field emission display device having carbon nanotubes grown directly on a substrate.

Hereinafter, a method of manufacturing a tripolar carbon nanotube field emission display device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3A to 3F are cross-sectional views illustrating a method of manufacturing a field emission display device according to an exemplary embodiment of the present invention.

As shown in FIG. 3A, a gate insulating film 101 and a gate electrode 102 are sequentially formed on the lower substrate 100, and a photoresist (not shown) is deposited on the gate electrode 102. do. In this case, the gate insulating film 101 is formed to a thickness of 1 μm by a wet oxidation method in an ionization furnace of about 1100 ° C., and the gate electrode 102 is formed to be 100 to 350 nm using Nb, W, Cr, Ti, or the like. do. The gate electrode 102 is formed at room temperature using the DC sputtering method.

Subsequently, as shown in FIG. 3B, the gate electrode 102 is selectively removed to expose a portion of the surface of the gate insulating film 101 through a reactive etching process using the photoresist as a mask using a photo process.

Next, as shown in FIG. 3C, the gate insulating layer 101 is selectively removed to expose the surface of the substrate 100 using the gate electrode 102 as a mask to form a hole 103.

Here, the gate insulating film 101 is wet etched for about 4 minutes using BOE (Buffered Oxide Etchant) and then dry etched. At this time, the gas atmosphere in the chamber during the dry etching is Ar: CHF ₃ = 2: 1, the power is about 200W.

As described above, in the case of performing the wet etching and the dry etching during the etching of the gate insulating layer 101, the distance between the gate electrode 102 and the cathode electrode may be increased, and the magnitude and distribution of the electric field applied to the gate insulating layer 101 may be increased. Can be reduced. Therefore, as a result of using the mixed etching process, the electric field applied to the end of the electron emission source (for example, the tip) is increased as compared with the case of using only the wet etching, thereby stabilizing the leakage current characteristic.

Next, as shown in FIG. 3D, an aluminum layer 104 to be used as a sacrificial layer is formed on the gate electrode 102 to a thickness of about 200 nm. At this time, the substrate 100 is mounted to the substrate holder to rotate in a state inclined about 15 degrees.

As shown in FIG. 3E, the catalyst metal 105 for CNT growth is selectively deposited in the hole 103 by using an e-beam deposition method. At this time, when depositing the catalytic metal 105, 4N purity Ni was deposited on a specimen mounted on a rotating substrate holder in an inclined state at about 15 degrees, and a source was mounted thereon, and then about 5 to 70 nm at room temperature. Preferably, the catalyst metal layer 105 having a thickness of 15 to 30 nm is formed.

Here, the substrate 100 is charged in a quartz tube for CNT growth and heat-treated for 10-30 minutes at a temperature of about 650 ~ 700 ℃ in N ₂ / H ₂ atmosphere. At this time, the catalyst metal 105 is Ni, Co, Fe, (Ni / Co) n, (Co / Ni) n (n = 1, 2, 3,) and (Co / Ni / Co) n, ( Ni / Co / Ni) n (n = 1, 2, 3,) is used.

Subsequently, as shown in FIG. 3F, the CNTs on the catalyst metal 105 may be C ₂ H ₂ (or CH ₄ ) / N ₂ (or H ₂ , NH ₃ ) using a chemical vapor deposition process (CVD). After growth for 10 to 1000 seconds, preferably 100 seconds under conditions of a gas pressure of 10 to 200 Torr and a temperature of about 600 to 850 ° C., a lift-off process is performed on the substrate 100. A tripolar FED device with a directly grown CNT 106 is completed.

In this case, the growth of the CNT 106 is selectively performed only in the hole 103 having a diameter of several μm on which the catalyst metal 105 is deposited, and the height of the CNT 106 is increased by the thickness of the gate insulating film 101 and the gate electrode 102. Do not exceed the combined thickness. If the CNT 106 is excessively grown out of the hole 103, the CNT 106 becomes conductive and the device does not operate.

4A to 4C are views showing the structure of the completed device according to an embodiment of the present invention.

4A is a cross-sectional view of a device having a CNT selectively grown only at the center of the hole, and FIG. 4B is a pixel having about 900 holes in an area of 300 μm × 300 μm, and FIG. 4C is shown in FIG. 4B. It shows well-defined light emission of the device.

As described above, the method of manufacturing the tripolar carbon nanotube field emission display device according to the present invention requires the use of a highly difficult tip machining technique as in the prior art, and uses a low-cost CVD process only for a specific area within the three-dimensional ultrafine structure. By selectively growing CNTs directly, it is possible to manufacture field emission display devices having high mechanical strength, high field emission current, and low voltage turn-on characteristics.

Claims (11)

In the method of manufacturing a field emission display device comprising a transparent electrode, a lower substrate formed to correspond to the upper substrate on which the light emitting layer is formed, Forming a gate insulating film and a gate electrode sequentially on a lower substrate, and selectively etching the gate electrode to expose a predetermined portion of the gate insulating film; Forming a hole by wet etching and dry etching the gate insulating layer to expose a predetermined portion of the surface of the substrate; Forming a sacrificial layer on the gate electrode to have a predetermined slope using an electron-ray deposition method; After selectively depositing a catalyst metal of an ultra-thin film formed at 15 to 30 nm using a substrate having an inclination and a rotational movement on the substrate of the hole , C ₂ H ₂ (or CH ₄ ) / N ₂ (or H ₂ , NH ₃ ) optionally forming carbon nanotubes in the center of the hole using a chemical vapor deposition method under a gas pressure of 10 to 200 Torr, a growth time of 100 seconds and a temperature of 600 to 850 ° C . ; And And removing the sacrificial layer through a lift-off process to form a tripolar field emission display device having carbon nanotubes grown directly on a substrate. The method of claim 1, wherein the gate insulating layer is formed to have a thickness of about 1 μm by a wet oxidation method in an electric furnace at about 1100 ° C. 3. The method of claim 1, wherein the gate electrode is formed to have a thickness of 100 to 350 nm using Nb, W, Cr, and Ti. The method of claim 1, wherein the gate electrode is formed at room temperature using a DC sputtering method. The tripolar carbon of claim 1, wherein the gate insulating layer is etched for 4 minutes using BOE (Buffered Oxide Etchant), and dry etching is performed at 200W using Ar: CHF ₃ = 2: 1. Method of manufacturing a nanotube field emission display device. The method of claim 1, wherein the sacrificial layer is formed to have an inclination of about 15 degrees by using an aluminum layer. (delete) The method of claim 1, wherein the catalyst metal is Ni, Co, Fe, (Ni / Co) _n , (Co / Ni) _n and (Co / Ni / Co) _n , (Ni / Co / Ni) _n to use A method of manufacturing a field emission display device. The method of claim 1, wherein the catalytic metal is charged into a quartz tube and heat-treated at 650 to 700 ° C. for 10 to 30 minutes in an N ₂ / H ₂ atmosphere. The method of claim 1, wherein the sacrificial layer is formed to a thickness of 200 nm. (delete)