KR100484886B1 - Evaporation System of MgO Layer Using Inductively Coupled Plasma on PDP And Method Thereof - Google Patents

Abstract

The present invention relates to a method of forming an MgO protective film of a PDP substrate using an inductively coupled plasma, and more particularly, to an MgO of a PDP substrate using an inductively coupled plasma for forming an MgO protective film serving as a protective film of a dielectric and an electrode in an AC-PDP. A protective film formation method is related.

The present invention is a chamber for receiving an inert gas and oxygen; A boat installed in the chamber to evaporate Mg; Forming an MgO protective film of a PDP substrate using an inductively coupled plasma, characterized in that it comprises an inductively coupled plasma generating device for converting the inert gas and oxygen and Mg into a plasma state to form an MgO protective film on one surface of the substrate installed in the chamber Provide a system.

Description

Evaporation System of MgO Layer Using Inductively Coupled Plasma on PDP And Method Thereof}

The present invention relates to an MgO protective film deposition system and method thereof of a PDP substrate using an inductively coupled plasma, and more particularly, to a PDP using an inductively coupled plasma for forming an MgO protective film serving as a protective film of a dielectric and an electrode in an AC-PDP. An MgO protective film deposition system of a substrate and a method thereof.

In general, AC-PDP is a flat panel display that generates a visible light by generating a plasma between two electrodes and then stimulating the phosphor with ultraviolet light emitted from the plasma.

However, since the plasma seriously damages the electrode and the dielectric covering the electrode, reducing the lifetime of the AC-PDP, a method of depositing a MgO protective film having a good sputtering rate and a good transmittance in order to compensate for this problem. This was designed. MgO is an oxide-based, the protective film is maximized when the crystallinity is high.

In addition, there is a characteristic that emits secondary electrons when exposed to plasma, which lowers the power required to maintain the plasma generated inside the AC-PDP.

Therefore, MgO having excellent characteristics plays an important role in prolonging the lifetime of AC-PDP and lowering driving power. A condition required for the production of such a MgO protective film is that a thin film having high crystallinity and high transmittance must be achieved through a method capable of low-cost and large-area deposition.

In order to explain in more detail the role of the MgO protective film in AC-PDP and the conditions to be described with reference to FIG. 1 as follows.

One cell of the AC-PDP, in which various structures are disposed between the front and rear glass substrates 10 and 20, is located directly below the front glass 10 and above the rear glass 20 (bus electrode 14). , ITO electrode 16 and address electrode 26. The bus electrode 14 and the ITO electrode 16 located below the windshield 10 are transparent electrodes, and for the insulation of the electrodes, a transparent dielectric 12 also surrounds the electrodes. The transparent electrodes 14 and 16 and the dielectric 12 positioned as described above have a problem of being corroded and damaged when exposed to plasma. Thus, an MgO protective film 11 is deposited below the dielectric 12. On the other hand, the barrier ribs 22 are stacked on the rear glass 20, the electrodes 26 are provided between the barrier ribs 22, and then red, green, and blue phosphors 24 are applied thereon.

The light emission principle of the PDP thus made is as shown in FIG. 2.

Light emission procedure: AC voltage is applied to the bus electrode 14 → plasma is generated between the electrodes 14 → ultraviolet light is generated from the plasma → ultraviolet light stimulates the phosphor 24 to generate visible light of red, blue, and green color → visible light is applied to the front glass Pass 10.

In contrast to the light emission procedure above, the role of the MgO passivation layer is to first protect the electrodes 14, 16 located below the windshield 10 and the dielectric 12 surrounding the electrodes.

Since the generated plasma of the AC-PDP seriously damages the electrode and the dielectric, the direct exposure to the plasma environment cannot apply a voltage for emitting the AC-PDP, and thus the life of the AC-PDP is extremely shortened. For this reason, the MgO protective film 11 having a very small sputtering rate is required to protect the etching against the plasma. Another advantage obtained by making the MgO protective film 11 is that the secondary electron emission rate is high due to the characteristics of the oxide film when the MgO protective film 11 is exposed to the plasma.

High secondary electron emission rates are a direct variable to the supply of electrons needed to keep the plasma constant. In other words, the high secondary electron emission rate means that the voltage required to drive and maintain the plasma is low enough, which may be a fundamental advantage in reducing power consumption or heating of the circuit due to driving.

On the other hand, visible light produced through the light emission procedure should pass through the front glass 10 in a clear state. If the light transmittance of the MgO protective film 11 is low, there is no reason to make the MgO protective film 11.

For the above reason, the MgO protective film 11 should have a small sputtering rate, a large secondary electron emission coefficient, and a high transmittance. Since these properties are inherent in the MgO material itself, if the stoichiometric ratio of the MgO protective film to be manufactured is well matched and the crystallinity is high, the MgO protective film 11 satisfies the properties required.

The MgO deposition method currently used mainly uses MgO itself as a source. That is, there is a method of melting the MgO source by E-Beam method to evaporate (E-Beam Evaporation) or sputtering MgO and depositing it on a substrate (Sputtering method).

These methods basically use MgO sources, which makes the raw material itself expensive and in both cases inefficiencies in which only a few percent of the source material is deposited. In addition to such inefficiency, low crystallinity of the deposited MgO protective film, difficulty in large-area deposition, and low deposition rate have been problematic. E-beam evaporation can secure relatively high crystallinity by heating or heat-treating the substrate, but it has difficulty in low deposition rate and large area deposition.

This is because the substrate on which the MgO protective film is deposited is amorphous glass, which causes a problem of deformation in heat of 300 to 400 ° C. On the other hand, the production of MgO protective film by sputtering method is advantageous in that large area deposition is possible because the substrate can be deposited vertically, but the crystallinity of the thin film is inferior, and the manufacturing method that is disregarded in the actual process due to the slow deposition rate to be. When manufacturing MgO protective film by sputtering method, there is also a method of obtaining MgO protective film by reacting with oxygen using Mg target, but the yield is low due to the general characteristics of sputtering method, and discharge characteristics in AC-PDP of manufactured MgO protective film This is reported to be poor.

In addition, screen printing, spray pyrolysis, and the like have been developed as non-vacuum deposition methods for manufacturing MgO protective films.

The screen printing method is a method of obtaining MgO crystals by applying MgO to an adhesive and then applying a heat treatment at around 600 ° C. The process is complicated and poor in crystallinity, and contains a large amount of impurities in the thin film to discharge the AC-PDP. It is known to adversely affect the properties.

Spray pyrolysis is a method of dissolving MgO in a solvent and then removing the solvent through heat treatment to obtain crystals.

Accordingly, the present invention has been made in view of the problems of the prior art, and an object thereof is to provide an inductively coupled plasma capable of forming an MgO protective film having excellent crystallinity and light transmittance using an inductively coupled plasma to protect a dielectric and an electrode in a PDP. To provide a MgO protective film deposition system and a method of a PDP substrate using.

In order to achieve the above object, the present invention comprises a chamber for receiving an inert gas and oxygen; A boat installed in the chamber to evaporate Mg; MgO protective film deposition of a PDP substrate using an inductively coupled plasma, comprising an inductively coupled plasma generating device for converting the inert gas and oxygen and Mg into a plasma state to form an MgO protective film on one surface of the substrate installed in the chamber Provide a system.

The boat vaporizes the Mg by using resistance heat, and the inductively coupled plasma generator includes an inductively coupled plasma coil installed vertically between the substrate and the boat, and the substrate is next to the inductively coupled plasma coil. It is installed vertically.

In addition, the present invention comprises the steps of vaporizing Mg by heating a boat installed in the chamber; Supplying an inert gas and oxygen into the chamber; Converting the Mg and oxygen into a plasma state by applying an RF signal to an inductively coupled plasma coil installed next to the boat; And forming an MgO protective film on one surface of the substrate installed next to the inductively coupled plasma coil.

As described above, in the present invention, instead of using an expensive MgO compound as a protective film for protecting the dielectric and the electrode of the AC-PDP substrate, by converting Mg and oxygen into a plasma state and depositing it on a vertically installed substrate, crystallinity and translucency It provides an excellent vapor deposition film.

(Example)

Hereinafter, with reference to the accompanying drawings showing a preferred embodiment of the present invention described above in more detail.

1 is a schematic diagram for explaining the structure of the AC-PDP, Figure 2 is an exemplary view for explaining the light emission principle of the AC-PDP, Figure 3 is a schematic diagram for explaining the structure of the inductively coupled plasma sublimation apparatus, 4 is a graph showing an XRD result, FIG. 5 is a graph showing an XRD result, FIG. 6 is a graph showing a measurement result of transmittance, and FIG. 7 is a graph comparing a RBS measurement result and a simulation.

The present invention is a method of obtaining MgO by reacting Mg with oxygen, unlike the conventional MgO deposition method, while excluding the explosive reaction of Mg, which is a highly reactive metal, with oxygen, it has excellent stoichiometric ratio and high crystallinity. It is possible to achieve a low-cost, high-speed deposition of a high-performance MgO protective film.

In order to keep the reaction of Mg and oxygen in a stable and active state, the deposition was performed in a high density plasma atmosphere. In other words, we developed an evaporation device equipped with an inductively coupled plasma generating coil that provides high ion density, controls the reaction of Mg and oxygen through high density plasma, increases the reaction speed, To improve the crystallinity has been developed a technology that can prevent the distortion of the substrate by the heat.

On the other hand, by replacing the source with Mg in the expensive MgO compound, not only the use of inexpensive source raw materials, but also a revolutionary conversion in the method of heating the source was made. The only way to vaporize MgO, which has a melting temperature of 2827 (± 30) ℃, is to use an electron beam or laser.

However, since the melting temperature of Mg is 650 ℃, the resistance heating method is sufficient to make it vapor. In addition, since Mg is a sublimable material, the sublimation is actively active at about 300 ° C., so the method of obtaining Mg vapor required for the process is simple.

Using inductively coupled plasma generating coils to use high density plasma and replacing Mg with a source eliminates the need for heating the substrate and allows the glass substrate to stand vertically.

Inductively coupled plasmas, together with high ionic densities, maximize the effect of particle collisions on the substrate, activating the movement of particles that reach the surface of the membrane, which enhances the crystallinity of the membrane without additional substrate heating.

Meanwhile, the method of evaporating the MgO source with an e-beam gun at the bottom of the substrate after laying the glass substrate horizontally is presently applied, but there is a problem of deformation of the substrate when a large-area glass substrate is used. In case of heating the substrate, the problem becomes more serious.

If the glass serving as the substrate is placed vertically, deformation of the substrate can be prevented, but MgO, which is locally melted by the electron beam, flows down, which is not a correct solution. However, in the case of the present invention, since the source is Mg having sublimation, even if the source is sublimated to the side, the source does not have any problem because Mg vapor is required for the process while maintaining the solid state.

As such, the present invention enables the verticalization of the substrate in the deposition process by using an Mg source and an inductively coupled plasma. In other words, Mg particles that start to sublime from a vertically oriented Mg source are activated by a high density inductively coupled plasma to effectively react with oxygen and impinge on the substrate. At this time, the colliding particles have a high mobility as described above, so no separate heating of the substrate is required.

By using this method, the MgO protective film having excellent characteristics can be produced at low cost while preventing the deformation of the glass substrate.

The present invention introduces oxygen, which is a reaction gas, and argon gas for generating high-density plasma together in a resistive heating Mg evaporation system, and inductively coupled plasma generator (coil), that is, RFI (Radio Frequency Inductively coupled) The coil is provided inside to deposit a desired MgO protective film on a vertically oriented glass substrate, and has a structure as shown in FIG.

The chamber 30 is connected to a gas line 31 which supplies argon gas and oxygen gas while maintaining a proper pressure.

In addition, a substrate 38 on which an MgO protective film is deposited is provided at one inner side thereof, and a boat 34 for evaporating Mg 36 serving as a source is provided at the other side, and the substrate 38 and the boat 34 have a substrate 38. In the middle, an inductively coupled plasma coil 32 is formed which forms a magnetic field for activating the internal gas in a plasma state.

The boat 34 includes a heater for heating and vaporizing the source Mg 36, and the heater generates heat by receiving current from the resistance heater 35.

In addition, the resistance heating unit 35 senses the temperature of the boat 34 through the heat sensor 37 attached to the boat 34 to control the amount of current supplied according to the elevation of the temperature to maintain an appropriate temperature. .

The RF power supply 33 supplying RF power to the inductively coupled plasma coil 32 generates an RF pulse of 13.56 MHz.

When oxygen and argon flow into the chamber 31 through the gas line 31 and stabilize at an appropriate pressure, an RF pulse of 13.56 MHz is applied from the RF power supply 33 to the inductively coupled plasma coil 32.

In the inductively coupled plasma coil 32, the electrons around it are accelerated by the electromagnetic induction phenomenon to generate plasma. In this case, in order to increase the efficiency and stability of the plasma, the impedance matching unit is connected between the RF power supply 33 and the inductively coupled plasma coil 32.

In order to obtain a vapor pressure of the magnesium 36 after the plasma generation, the resistance is heated by supplying a current to the boat 34 using the resistance heating part 35.

The characteristic difference from the horizontally arranged structure, such as the existing "ion plating system using inductively coupled plasma (filed by the applicant No. 10-2002-0021014 on April 17, 2002), generates a plasma. The inductively coupled plasma coil 32 is installed vertically. In addition, the boat 34 for heating the substrate 38 and the source 36 was all installed vertically. The distance between the boat 34 and the substrate 38 is about 11 cm, with the inductively coupled plasma coil 32 in between. Cooling water flows inside the inductively coupled plasma coil 32, and the outside of the coil is wrapped with an insulating material to lower the plasma potential V _P.

Meanwhile, in order to prevent the generated plasma and the current flowing through the resistance heating unit 35 from interacting with each other, the wiring between the heater exposed to the plasma and the resistance heating unit 35 is insulated. In addition, the vapor pressure of the Mg source must be kept constant for the deposition to be even. Therefore, the temperature sensor 37 made of a thermocouple capable of measuring the temperature on the side of the boat 34 was installed to be insulated from the boat 34, thereby measuring the temperature of the boat 34. To control the amount of current.

Referring to the characteristics of the MgO protective film according to the present invention.

Item Experimental conditions Process pressure 10-25 mTorr Flow rate ratio of reaction gas Oxygen: Argon = 6: 4 ICP power 300 W Substrate temperature Room temperature Mg source heating temperature  330 ℃

1) Crystallinity

A. XRD Results A (see Figure 4)

Process pressure: 10mTor

(111) plane: 2θ = 36.937 degrees

(222) plane: 2θ = 78.630 degrees

B. XRD Results B (see Figure 5)

Process pressure: 25mTorr

(200) plane: 2θ = 42.917 degrees

The crystallinity is comparable to that of the electron beam deposition method which shows the best crystallinity among the existing MgO protective film manufacturing methods. It also has the property of controlling the preferred orientation of the crystal in response to changes in process pressure. Reported results indicate that the secondary electron emission coefficients differ depending on the different crystal planes, but it remains controversial.

On the other hand, in the electron beam deposition method, which is a manufacturing method of MgO protective film currently used in the actual process, when the substrate temperature is 300 ° C. or less, the (200) plane is usually oriented first, and the (111) plane is changed by plasma or substrate bias during the process. This may be a preferred orientation.

Another advantage of the method of manufacturing the MgO protective film according to the present invention is that the direction can be controlled first without the aid of a separate substrate heating apparatus or a substrate biasing apparatus.

In addition, when the MgO protective film is manufactured by the apparatus according to the present invention, this process is performed without heating the substrate. The required thickness of the MgO protective film used as the protective film of AC-PDP is about 3000Å. In order to achieve this thickness, the equipment according to the present invention takes about four minutes, and the average deposition rate is 800 mW / min. The resistive heating of the Mg boat takes about seven minutes to sublimate the Mg source before the actual thin film is produced. Plasma is formed while reaching the required temperature. Due to the ion bombardment effect of the plasma, the total time that the portion exposed to the plasma can be heated is about 10 to 12 minutes. During this time, the substrate is not cooled separately. After the process is started at room temperature, the temperature is measured through the thermocouple to check the temperature rise of the substrate due to the ion collision effect of plasma. The temperature rising result of was confirmed.

2) transmittance

Considering that the visible light region is 380 to 770 nm, it can be seen that the MgO protective film prepared in this experiment shows a high transmittance of 90% or more in the entire visible light region (see FIG. 6).

This transmittance characteristic is almost similar to that of the MgO protective film produced by the conventional method.

3) stoichiometric ratio

In case of E-beam evaporation using MgO as a source of the conventional MgO protective film manufacturing method, there is no problem about the stoichiometric ratio of the manufactured thin film. However, in the case of the sputtering method, it is necessary to confirm the stoichiometric ratio because there is a difference in sputtering for each material. If the production of the MgO protective film by the reaction method of Mg and O ₂ will have a good stoichiometric ratio. The stoichiometric ratio of the MgO protective film obtained by the present invention was confirmed by RBS (backscattered electron) analysis, and the results showed an excellent stoichiometric ratio of Mg: O = 1: 1 to Mg: O = 1: 1. (See FIG. 7).

The above characteristics are obtained by changing the process pressure, and studies are underway to find better process conditions than the above results. That is, vapor deposition is carried out with a mixing ratio of the reaction gas of 50 to 70% O ₂ + Ar, ICP power of 0 to 700 W, and Mg heating temperature of 330 to 390 ° C. Accordingly, higher deposition rates and higher crystallinity can be expected.

The present invention made as described above enables the production of an MgO protective film which plays an important role as a protective film in the AC-PDP by a vertical method without using separate heating of the substrate by using an evaporation method equipped with an inductively coupled plasma. As a result, it is possible to deposit a large area of MgO having superior characteristics while significantly lowering the production cost compared to the existing process.

In the above, the present invention has been illustrated and described with reference to specific preferred embodiments, but the present invention is not limited to the above-described embodiments, and the general knowledge in the technical field to which the present invention belongs does not depart from the spirit of the present invention. Various changes and modifications will be made by those who possess.

1 is a schematic diagram for explaining the structure of an AC-PDP.

2 is an exemplary diagram for explaining a light emission principle of an AC-PDP.

Figure 3 is a schematic diagram for explaining the structure of the inductively coupled plasma sublimation device.

4 is a graph showing the XRD results.

5 is a graph showing the XRD results.

6 is a graph showing the results of transmittance measurement.

7 is a graph comparing the results of RBS measurement and simulation.

Explanation of symbols on the main parts of the drawings

30 chamber 31 gas line

32: inductively coupled plasma coil 33: RF power supply

34: boat 35: resistance heating unit

36 source 37 temperature sensor

38: substrate

Claims (6)

A chamber in which an inert gas and oxygen are supplied and a substrate having an MgO protective film formed on one surface thereof is installed vertically on one side thereof; A boat installed at an opposite position of the substrate in the chamber to evaporate Mg; An inductively coupled plasma coil installed vertically between the substrate and the boat to convert the inert gas, oxygen, and Mg into a plasma state by inductive coupling to form an MgO protective film on one surface of the substrate; And An RF power supply unit supplying RF power to the inductively coupled plasma coil; MgO protective film deposition system of a PDP substrate using an inductively coupled plasma comprising a. According to claim 1, The boat is a heater built into the boat to vaporize the Mg using the resistance heat, a resistance heating unit for supplying a current to the heater, and attached to one side of the boat to measure the temperature And a temperature sensor configured to control the amount of current supplied to the heater such that the temperature measured through the temperature sensor is maintained at a predetermined constant temperature in order to maintain a constant vapor pressure of the Mg source. MgO protective film deposition system of a PDP substrate using an inductively coupled plasma. The MgO protective film deposition system of claim 1, wherein the inductively coupled plasma coil has a cooling water for cooling therein, and an outer surface thereof is electrically insulated by an insulating material. . The MgO protective film deposition system of claim 1, wherein the substrate is maintained at room temperature. Vaporizing Mg by heating a substrate to form an MgO protective film on one surface thereof in a chamber vertically, and heating a boat provided at an opposite position of the substrate to vaporize Mg; Supplying inert gas and oxygen into the chamber; And Applying an RF power to an inductively coupled plasma coil installed vertically between the boat and the substrate to convert the Mg and oxygen into a plasma state to form an MgO protective film on one surface of the substrate MgO protective film deposition method of a PDP substrate using an inductively coupled plasma comprising a. The method of claim 5, wherein the substrate is maintained at room temperature. 7.