KR100625966B1 - Method of vacuum evaporation for EL and appratus the same - Google Patents

Abstract

According to the present invention, the thin film deposition of the organic EL device is prepared by depositing a deposition material, at least a first heating to a holding temperature below a set temperature for evaporating the deposition material in a vacuum atmosphere, It is characterized by controlling the evaporation temperature and the evaporation amount of the evaporation material by heating to a set temperature starting from the temperature.

Description

Method for depositing thin film of organic EL element and apparatus therefor {Method of vacuum evaporation for EL and appratus the same}

1 is a view showing the relationship between the temperature and the evaporation rate of the thin film material,

2 is a view showing the relationship between the time and the evaporation control temperature of the thin film material,

3 is a view showing a deposition apparatus for performing a thin film deposition method according to the present invention,

4 is a perspective view showing a heating means,

5 is a perspective view showing another embodiment of the heating means,

6 is a cross-sectional view schematically showing a thin film deposition apparatus according to the present invention;

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an organic EL device, and a method and apparatus for thin film deposition of an organic EL device for depositing an electrode material and an organic material on a substrate to form an organic thin film and an electrode layer.

EL devices are attracting attention as next-generation display devices because they have the advantages of wide viewing angle, excellent contrast, and fast response speed.

EL devices are classified into inorganic EL devices and organic EL devices according to materials for forming an emitter layer. Herein, the organic EL device has an advantage of excellent luminance, driving voltage, and response speed, and multicoloring, compared to the inorganic EL device.

In the structure of a general organic EL element, a positive electrode layer having a predetermined pattern is formed on a substrate. The hole transport layer, the light emitting layer, and the electron transport layer are sequentially formed on the positive electrode layer, and a negative electrode layer having a predetermined pattern is formed on the upper surface of the electron transport layer in a direction orthogonal to the positive electrode layer. Here, the hole transport layer, the light emitting layer and the electron transport layer are organic thin films made of an organic compound.

The organic EL element having the structure as described above is driven as follows. When a voltage is applied between the selected positive electrode layer and the negative electrode layer, holes injected from the selected positive electrode layer are moved to the light emitting layer via the hole transport layer. On the other hand, electrons are injected into the light emitting layer from the negative electrode layer via the electron transport layer, and carriers are recombined in the light emitting layer to generate excitons. This exciton is changed from an excited state to a ground state, whereby an image is formed by the fluorescent molecules of the light emitting layer emitting light.

In fabricating the organic EL device constructed and operated as described above, vapor deposition is performed by sequentially heating and evaporating a buffer material, a hole transporting layer, an electron transporting layer and a positive electrode layer, and a material forming a negative electrode layer as organic materials on a substrate, respectively. To produce a thin film. By depositing a thin film in the same manner as above to configure a device that performs a predetermined function.

The organic material forming the thin film of the organic EL device is evaporated in a temperature range of 250 to 450 degrees in vacuum. On the other hand, the electrode material is generally evaporated at a high temperature compared with the organic material, the evaporation temperature varies greatly depending on the type of material. The most commonly used Mg evaporates at 500 to 600 degrees and simultaneously used Ag evaporates at more than 1000 degrees. In addition, Al used as an electrode material evaporates around 1000 degrees, and Li evaporates at 300 degrees.

Since the organic material evaporates at a low temperature, evaporation is simple, but impurities also easily evaporate to contaminate the deposited thin film. Meanwhile, since the amount of evaporated material varies depending on the heating temperature in the process of heating the organic material, precise temperature control is required to make the evaporation amount of the material constant. Furthermore, certain organic materials are evaporated by sublimation, which changes directly from solid to gas. In this case, organic materials are generally poor in thermal conductivity, so organic materials evaporate from the contact with the container and the remaining part is separated from the container. In order to continue evaporation at a constant rate, control such as gradually raising the temperature of the heating vessel is required. There are also metal materials that evaporate after melting and materials that change directly from solid to gas, but the rate of evaporation changes rapidly with temperature rise is the same as organic materials. It is difficult to control a sublimation material that converts from a solid into a gas at a constant speed like organic materials.

The organic EL device must deposit at least two organic materials and two or more kinds of organic materials and two kinds of metal materials by one deposition operation in an element for implementing at least two types of color images of organic materials. In addition, when so-called doping in which two kinds of materials are evaporated at the same time, precise control of the evaporation rate is required because two materials are deposited at the same time and the ratio of the evaporation rates is kept constant.

Typically, temperature control of the material is performed to control the evaporation rate (temperature control means temperature control of the material, not temperature control of the container.) Such temperature control may be performed as a current or voltage control applied to the heater. In the case of organic EL device fabrication, a uniform evaporation rate must be maintained within a short time, and overshoot of temperature is not allowed. These conditions are not so difficult to carefully control and deposit each material at the laboratory stage. However, in the case of industrially producing devices continuously, it is necessary to perform thin film deposition in the shortest time possible.

1 shows an example of the relationship between temperature and evaporation rate. FIG. 1 is an experimental example showing the relationship between the temperature and deposition rate of alumininolin, which is a light emitting material which is most used in the manufacture of organic EL devices, and constitutes an electron transport layer. In general, the deposition rate is several angstroms per second. However, in the case of doping, a speed control of about 30 s per second and a precision of two or more digits is obtained as a minimum example.

In FIG. 1, the speed control of 0.1 Hz is shown to require temperature control of 0.1 degrees or more in terms of temperature. Temperature control on the order of 0.1 degrees in a short time is generally very difficult.

2 shows the relationship between time and control temperature for thin film deposition.

Even if optimal control is carried out to obtain a constant heating temperature at a constant evaporation rate, the controllability is inferior when the temperature difference between the starting point and the temperature to be controlled is large or when the disturbance such as the escape of heat to other parts is large. The time required is increased. In the experimental example shown in FIG. 2, it can be seen that even under optimum control conditions (graph B of FIG. 2), it takes more than 10 minutes to reach the set temperature. Of course, if the power supply for heating the material is increased to increase the rate of increase of the heating temperature (graph A of FIG. 2), an overshoot occurs and a large amount of the deposition material evaporates at once. The 10 minute waiting time to reach the set temperature means that 60 minutes of waiting time is required when six materials are deposited successively. And when considering the stability, the time to reach the set temperature is further lengthened (graph C of Figure 2).

SUMMARY OF THE INVENTION The present invention provides a thin film deposition method and apparatus for an organic EL device capable of precisely controlling the heating temperature and evaporation rate of a material for forming a thin film in order to solve the above problems.

Another object of the present invention is to maintain the heating temperature of the thin film forming material at a high temperature other than the evaporation temperature, and by using this holding temperature as a starting point for temperature control, the time for reaching the control temperature can be shortened. The present invention provides a vapor deposition method and apparatus.

In order to achieve the above object, a thin film deposition method of the organic EL device of the present invention,

A first step of preparing a deposition material for forming a thin film,

A second step of heating at least a first temperature to a holding temperature below a set temperature for evaporating the deposition material in a vacuum atmosphere;

And a third step of controlling the evaporation temperature and the evaporation amount of the deposition material by heating to the set temperature starting from the temperature of the deposition material heated in the second step.

In the present invention, it is preferable that the difference between the maintenance temperature and the control temperature of the deposition material is kept low by a temperature difference of 1/3 or less of the difference between the room temperature and the evaporation temperature.

A thin film deposition apparatus for achieving the above object includes a vacuum chamber, a mounting portion installed inside the vacuum chamber to fix a substrate on which a thin film is to be formed, and a temperature control of at least two stages provided at a portion corresponding to the substrate. It is characterized by including a possible heating means.

In the present invention, the heating means is provided between the boat containing the deposition material, the first heating means for wrapping the port and heating the deposition material to a maintenance temperature, the first heating means and the boat is provided between the And a second heating heater for heating the deposition material heated by the first heating heater to the holding temperature to the set temperature.

The boat is made of tungsten, molybdenum, pretium (Pt), titanium, nickel, iron or alloys of these materials, which have a relatively high coefficient of heat transfer and low reactivity.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

A thin film deposition method of an organic EL device according to the present invention is to form an electrode layer, a hole transport layer and an electron transport layer by depositing an organic material or an electrode material on a substrate of an organic EL device, and to prepare a deposition material for forming a thin film. And a second step of at least primary heating to a holding temperature below a control temperature for evaporating the deposition material in a vacuum atmosphere. The holding temperature is preferably maintained at a temperature close to the control temperature to be described later, and may vary depending on a material to be deposited, that is, an organic material or an electrode material, but it is not necessary to control the temperature.

As described above, when the deposition material is heated to the holding temperature, a third step of heating to the control temperature is performed based on the holding temperature. In this third step, the set temperature is determined in consideration of the amount of evaporation over time of the heated thin film forming material. The difference between the control temperature and the holding temperature is preferably kept low by a temperature difference of 1/3 or less of the difference between the room temperature and the evaporation temperature.

3 schematically shows a deposition apparatus for forming a thin film.

The thin film deposition apparatus 10 for this deposition apparatus includes a vacuum chamber 11, a mounting portion 12 mounted inside the vacuum chamber to fix the substrate 100 on which the thin film is to be formed, and the substrate. It is installed on the site to include a heating means 20 capable of temperature control of at least two stages. Although not shown in the drawings, the vacuum chamber 11 has a vacuum pump for evacuating its interior.

One embodiment of the heating means 20 is combined with the boat 21 and the boat 21 having a groove 21a containing the deposition material using tungsten having 0.5mm as shown in FIG. And a cover 22 having a discharge port 22a through which the evaporated material is discharged to seal the groove 21a. Here, although the boat is not shown in the drawing, a predetermined power is supplied from both ends to form a single heating source. The power applied to the boat 21 is controlled at a control temperature for evaporation and a holding temperature lower than the control temperature. It is supplied in at least two stages to heat the evaporated material contained in the groove. The boat 21 preferably has as little heat capacity as possible, good thermal conductivity and fast response speed.

5 shows another embodiment of a heating means for heating the thin film deposition material.

As shown in the drawing, the heating means 30 includes a boat 31 containing a deposition material, a first heating heater 32 surrounding the boat 31 and heating the deposition material to a maintenance temperature, and the first heating heater. And a second heating heater 33 disposed between the 32 and the boat 31 to heat the deposition material heated to the holding temperature by the first heating heater to the control temperature.

The boat is relatively low in heat capacity, high in heat transfer coefficient and low in reactivity, and is made of high melting point metal materials such as tungsten, molybdenum, pretium (Pt), titanium, nickel, iron or alloys of these materials. On the other hand, since the metal material cannot be used when the deposition material is Al, BN (boron nitride) ceramic pots or alumina, cobalt, tungsten boats are used.

In addition, the first and second heating heaters 32 and 33 are attached to a separate controller using a resistor so as to adjust the applied voltage to enable separate control. The metal material constituting the boat is most suitable as long as it has a good thermal conductivity and a heating electrode.

In order to form a thin film on the substrate 100 using the thin film deposition apparatus configured as described above, the substrate is fixed to the mounting portion 12 and the thin film deposition material 200 is placed in the boat 31. In this state, as shown in FIG. 6, the thin film deposition material 200 contained in the boat is heated to the maintenance temperature using the first heating heater 32. When the boat 21 also serves as a heater as shown in FIG. 4, the voltage is adjusted so that the thin film deposition material is heated to a holding temperature. The holding temperature is preferably controlled to a temperature of 5 to 15 degrees lower than the temperature at which the thin film deposition material is melted and evaporated.

As described above, when the thin film deposition material 200 is heated to a maintenance temperature, the thin film deposition material 200 is heated to a control temperature for deposition using the second heating heater 33. Since the holding temperature is set to the base temperature to increase the control temperature from the holding temperature, the time can be shortened to about 25 seconds as shown in FIG. In particular, since the heating means as shown in FIG. 5 is constituted by two thermometers, the temperature control passed by the first heating heater, that is, the holding temperature is controlled, and the second heating heater close to the boat 31 is controlled. As a result, precise temperature control is performed only when the deposition is performed on the thin film deposition material.

As described above, the thin film deposition method of the organic EL device and the device of the present invention can precisely control the temperature of the thin film deposition material, so that it is possible to control the amount of evaporation for precise deposition and to shorten the time to reach the evaporation temperature. Applicable to mass production.                     

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (6)

A first step of preparing a deposition material for forming a thin film, A second step of heating at least a first temperature to a holding temperature below a set temperature for evaporating the deposition material in a vacuum atmosphere; And a third step of controlling the evaporation temperature and the evaporation amount of the deposition material by heating to a control temperature based on the temperature of the deposition material heated in the second step in a vacuum atmosphere. And the temperature difference between the holding temperature and the control temperature of the deposition material is kept low by a temperature difference of 1/3 or less of the difference between the room temperature and the evaporation temperature. delete A vacuum chamber, a mounting part installed inside the vacuum chamber to fix a substrate on which a thin film is to be formed, and heating means installed at a portion corresponding to the substrate to enable temperature control of at least two stages, The heating means includes a boat containing the deposition material, a first heating heater surrounding the boat and heating the deposition material to a maintenance temperature, and installed between the first heating heater and the boat to the first heating heater. And a second heating heater for heating the deposition material heated to the maintenance temperature by the set temperature. delete The method of claim 3, The metal material forming the boat is made of tungsten, molybdenum, pretium (Pt), titanium, nickel, iron, or an alloy of these materials, which is a highly reactive high melting point metal. The method of claim 1, And the holding temperature is controlled to be 5 to 15 degrees lower than the evaporation temperature of the deposition material.

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