KR20070068961A - Method of manufacturing for light emitting diodes - Google Patents

Abstract

A method of manufacturing a light emitting display device is provided to prevent a dark spot from being formed on a display by reducing the operation heat generated in the light emitting display device. A first electrode(54) is formed on a substrate(52). An oxide or a pollutant is removed from the first electrode by using an H2 plasma treatment. A light emitting unit is formed by laminating a first charge injection/transport layer, a light emitting layer, and a second charge injection/transport layer on the first electrode. A transparent or a semi-transparent second electrode is formed on the light emitting unit. The first electrode is made of an opaque or a semi-opaque material and reflects the light from the light emitting unit toward the substrate.

Description

Method of Manufacturing for Light Emitting Diodes

1 is a cross-sectional view of an electroluminescent device according to a first embodiment of the prior art.

2 is an enlarged view of a portion A of FIG. 1;

3 is a cross-sectional view of an electroluminescent device according to a second embodiment of the prior art.

4 is a cross-sectional view of an electroluminescent device according to a first embodiment of the prior art.

5 is a cross-sectional view of an electroluminescent device according to a second embodiment of the prior art.

6a to 6b are H2 plasma treatment process diagram of the electroluminescent device according to the present invention.

7 is a cross-sectional view of an electroluminescent device according to a first embodiment of the present invention.

8 is a cross-sectional view of an electroluminescent device according to a second embodiment of the present invention.

Explanation of the main symbols in the drawings

10 electroluminescent element 12 substrate

14 anode electrode 16 hole injection / transport layer

18: light emitting layer 20: electron injection / transport layer

22 cathode electrode 24 protection

24a: protective substrate 24b: getter

32 substrate 34 cathode electrode

36: electron injection / transport layer 38: light emitting layer

40: hole injection / transport layer 42: anode electrode

52 substrate 54 first electrode

D: oxide and foreign material layer F1: first light emission

F2: second light emitting L: light emitting

S: Sealant

The present invention relates to a method of manufacturing an electroluminescent device that improves the stability and luminous efficiency of the device through H ₂ plasma treatment.

In the following description of the prior art and the present invention, the light emitting layer of the electroluminescent device is formed of an organic material.

The electroluminescent device injects electrons and holes into the light emitting layer from an electron injection electrode and a hole injection electrode, respectively, and excitons of the injected electrons and holes combine from the excited state. It is a self-luminous device that emits light when it falls to the ground state.

In addition, the electroluminescent device can be driven at a low voltage and has advantages such as thinness. The electroluminescent device is attracting attention as a next-generation display that can solve the disadvantages pointed out as a problem in the conventional liquid crystal display, such as wide viewing angle and fast response speed.

Electroluminescent devices are classified into top-emission LEDs emitting light in a direction opposite to the substrate and bottom-emission LEDs emitting in the direction of the substrate according to the light emitting method.

1 is a cross-sectional view of an electroluminescent device according to a first embodiment of the prior art.

Referring to FIG. 1, in the electroluminescent device 10 according to the first exemplary embodiment of the related art, the light emitting part L is formed on the substrate 12 on which the driving part is patterned as the top emission type, and the light emitting part L The cathode electrode 24 was formed on (). In addition, in order to prevent oxidation and deterioration due to moisture, air, and the like of the light emitting portion L and the cathode electrode 24, the protecting portion 24 formed of the protective substrate 24a and the getters 24b and getters is provided with a sealant ( It was sealed on the board | substrate 12 by S).

FIG. 2 is a partially enlarged view of region A on FIG. 1.

Referring to FIG. 2, an anode electrode 14 providing holes is formed on the substrate 12, and the hole injection / transport layer 16, the light emitting layer 18, and the electron injection / transport layer 20 are sequentially formed thereon. Stacked to form the light emitting portion (L). On the light emitting portion L described above, a cathode electrode 22 for supplying electrons to the light emitting portion was formed.

At this time, the above-described anode electrode 14 serves as a reflective film for reflecting the light emission of the above-described light emitting portion (L) in the opposite direction of the substrate 12, the light emission of the device is directly emitted from the light emitting portion (L) to the outside The first light emission F1 and the second light emission F2 emitted from the light emitting part L to the substrate 12 and reflected from the aforementioned anode electrode 14 are emitted to the outside.

3 is a cross-sectional view of an electroluminescent device according to a second exemplary embodiment of the prior art, and has the same scale as FIG. 2.

Referring to FIG. 3, the electroluminescent device according to the second embodiment of the prior art has a cathode electrode which serves as a reflective film for electron injection and self-emission on the substrate 32 in an inverted top emission type. 34), the electron injection / transport layer 36, the light emitting layer 38, and the hole injection / transport layer 40 were sequentially stacked on the light emitting portion L. On the light emitting portion L described above, an anode electrode 42 was formed in contact with the light emitting portion L to supply holes.

The above-described cathode electrode 34 functions as a reflecting film on the same principle as the anode electrode 14 of the first embodiment described above.

In fabricating a conventional electroluminescent device having the above structure, since the electrode formed relatively close to the substrate side should also serve as a reflective film, for example, in the case of the anode electrode, a high work function and a high reflectance are very important characteristics. In addition, it further required properties such as low surface roughness, excellent bonding to the substrate, easy etching, environmental resistance and the like.

For example, Ag alloy or Al alloy is suitable as a material that satisfies these characteristics. However, Al alloy has been mainly used since Ag alloy has poor environmental resistance. However, in the case of Al alloys, high reactivity with oxygen, moisture, and the like has become a problem. In particular, when an alloy electrode containing 50% or more of Al is used, an oxide and a foreign material layer are formed on the electrode surface, and thus it is not easy to inject holes or electrons into the light emitting part.

Accordingly, since the leakage current increases, the driving voltage increases, thereby causing a serious problem of greatly deteriorating the stability of the device.

In addition, since the increased driving voltage increases the driving heat and deteriorates the organic material in the device, dark spots occur on the display, thereby degrading the lifetime and reliability.

In order to solve this problem, the present invention removes the oxide and foreign material layer formed on the surface of the electrode that acts as a reflective film in the electroluminescent device in the process, thereby facilitating the injection of holes or electrons to the light emitting part from the electrode described above. It is an object of the present invention to provide a method of manufacturing an electroluminescent device capable of realizing an electroluminescent device having improved stability, lifetime and reliability by lowering driving voltage and driving heat.

In order to achieve the above object, the present invention provides a first electrode forming step of forming a first electrode on a substrate and the oxide or foreign matter formed on the first electrode described above H ₂ An emission post-processing step of forming an emission part by stacking a first charge injection / transport layer, a light emitting layer, and a second charge injection / transport layer on the first electrode after the electrode post-treatment step removed by plasma treatment and the aforementioned electrode post-treatment step It provides a method of manufacturing an electroluminescent device comprising a forming step and a second electrode forming step of forming a transparent or semi-transparent second electrode on the above-described light emitting portion.

The method of manufacturing the electroluminescent device described above is characterized in that in the above-described first electrode forming step, the above-described first electrode is formed of an opaque or translucent material and reflects the light emission of the above-mentioned light emitting part in a direction opposite to the above-described substrate. do.

In addition, in the above-described light emitting part forming step, the aforementioned first charge injection / transport layer receives holes from the above-described first electrode and transports the same to the above-mentioned light emitting layer, and the above-mentioned second charge injection / transport layer is formed from the above-mentioned second electrode. The electrons are injected and transported to the light emitting layer described above.

In addition, the above-mentioned first electrode in the above-described first electrode forming step is characterized in that the Al or Al alloy.

On the other hand, in the electrode post-treatment step described above H ₂ Plasma treatment is characterized in that the progress in the atmosphere composed of 100% H ₂ .

In another aspect, H ₂ in the electrode post-treatment step described above Plasma treatment is characterized in that at least 10% of H ₂ and Ar, N ₂ , Ne, He, Kr, Xe or in one or more mixed gas atmosphere.

The plasma power source in the above electrode post-treatment step is characterized in that any one of Capacitively Coupled Plasma (CCP), Transfer coupled Plasma (TCP), Inductive coupled Plasma (ICP), Electron Cyclotron Resonance Plasma (ECRP).

In addition, the above-described pressure conditions of the first electrode forming step, the electrode post-treatment step, the light emitting part forming step and the second electrode forming step may be 10 ⁻³ to 10 Torr.

In the above-described light emitting portion forming step, the light emitting layer is formed of an organic material.

4 and 5 are cross-sectional views of the electroluminescent devices according to the first and second embodiments of the prior art, where the oxide and foreign material layer (D) formed on the electrode serving as the reflective film, which is a problem of the prior art described above, can be seen. .

As such, the electroluminescent device of the present invention undergoes an H ₂ plasma treatment step to remove unwanted oxide and foreign material layers (D).

6A to 6B are H ₂ plasma treatment process diagrams of an electroluminescent device according to the present invention, focusing on a substrate and a reactant which are a process target in a chamber.

Accordingly, FIGS. 6A to 6B show the substrate 52 in the manufacturing process of the EL device.

The process of removing the oxide and the foreign material layer (D) formed on the surface of the electrode patterned on it shows the before and after state of the H ₂ plasma treatment process.

The process and principle of the H ₂ plasma treatment process described above are as follows.

For example, the first electrode 54 is patterned on the substrate 52 by any one of thermal evaporation, E-beam evaporation, sputter, and CVD.

At this time, the first electrode 54 described above is formed of a material having high conductivity and reflectance, for example, of Al alloy.

As described above, since the Al alloy has good reactivity with moisture or oxygen, a natural oxide film D is formed on the first electrode 54 as shown.

In order to remove the above-described natural oxide film (D), the present invention is subjected to the H ₂ plasma treatment, in which the inside of the process chamber, for example, 100% H ₂ or, for the high efficiency of the H ₂ plasma treatment, N ₂ , Ne, He, Kr, Xe any one or more of the composition of the gas and H ₂ gas composition. The mixed gas atmosphere described above uses a composition ratio containing at least 10% of H ₂ .

In addition, the power source for forming the H ₂ plasma, for example, Capacitively Coupled Plasma (CCP), Transfer coupled Plasma (TCP), Inductive coupled Plasma (ICP), ECRP (Electron Cyclotron Resonance Plasma) One can be used, preferably using a high plasma density method.

At this time, the power source to be used should be selected differently according to the area of the electrode, it is preferable to select in the power range of 0.01W / cm ² to 100W / cm ² .

In addition, while biasing the substrate side for effective reactivity of the H ₂ plasma treatment, it is preferable to apply a bias within the range of -10 to -1000V by applying RF power (Radio Frequency Power).

In addition, all the processes described above is preferably carried out under pressure conditions of 10 ^-3 ~ 10 Torr.

In the reaction relationship between materials in the H ₂ plasma treatment process, H ₂ injected into the plasma is decomposed into H ⁺ ions, reacted with an oxide on the surface of the Al alloy electrode, and released to the outside in the form of H ₂ O or OH ⁻ ions. Oxides and foreign substances on the surface of the alloy electrode are removed.

Through the H ₂ plasma treatment as described above, the present invention can achieve the intended purpose, and the structure of the electroluminescent device of the present invention is illustrated in FIGS. 7 and 8 as a result of the process.

7 and 8 are cross-sectional roads of the electroluminescent device according to the first and second embodiments of the present invention, FIG. 7 is a state diagram after the H ₂ plasma treatment of FIG. 4, and FIG. 8 is a view after the H ₂ plasma treatment of FIG. 5. Shows a state diagram.

The present invention is applicable not only to the active matrix type but also to the passive matrix type.

As described above, the present invention has been described with reference to, for example, a unidirectional light emitting type, but the present invention is not limited thereto and may be applied to a double sided light emitting type.

In the above description of the prior art and the present invention, the organic light emitting layer is adopted by applying the organic light emitting layer to the light emitting unit. However, the present invention is not limited thereto. LED's category should be understood.

While the present invention has been described with reference to various embodiments, the scope of the present invention is indicated by the following claims rather than the foregoing description, and all changes derived from the meaning and scope of the claims and their equivalent concepts. Or variations should be construed as being included in the scope of the invention.

As described above, the present invention removes the oxide and foreign material layer formed on the surface of the electrode that acts as a reflective film in the electroluminescent device in the process, thereby facilitating the injection of holes or electrons from the electrode described above to the light emitting part. Can lower the voltage. In addition, the present invention can lower the driving heat to suppress deterioration of organic matter in the device and generation of dark spots on the display.

Ultimately, the present invention can improve the stability, lifetime and reliability of the device.

Claims (9)

Forming a first electrode on the substrate; Oxide or foreign matter formed on the first electrode H ₂ An electrode post-treatment step of removing by plasma treatment; A light emitting part forming step of forming a light emitting part by stacking a first charge injection / transport layer, a light emitting layer, and a second charge injection / transport layer on the first electrode after the electrode post-processing step; And a second electrode forming step of forming a transparent or semi-transparent second electrode on the light emitting part. The method of claim 1, In the first electrode forming step, the first electrode is formed of an opaque or semi-transparent material and the method of manufacturing an electroluminescent device, characterized in that for reflecting the light emission of the light emitting portion in a direction opposite to the substrate. The method of claim 1, In the forming of the light emitting unit, the first charge injection / transport layer receives holes from the first electrode and transports the light to the light emitting layer, and the second charge injection / transport layer transports electrons from the second electrode to the light emitting layer. Method of manufacturing an electroluminescent device, characterized in that. The method of claim 1, In the first electrode forming step, the first electrode is Al or Al alloy manufacturing method of the electroluminescent device, characterized in that. The method of claim 1, H ₂ in the electrode post-treatment step Plasma treatment is a method of manufacturing an electroluminescent device, characterized in that the progress in the atmosphere composed of 100% H ₂ . The method of claim 1, H ₂ in the electrode post-treatment step Plasma treatment is 10% or more H ₂ and Ar, N ₂ , Ne, He, Kr, Xe any one or one or more of the mixed gas atmosphere of the manufacturing method of the electroluminescent device characterized in that. The method according to any one of claims 1 to 6, In the post-treatment of the electrode, the plasma power source may be any one of capacitively coupled plasma (CCP), transfer coupled plasma (TCP), inductive coupled plasma (ICP), and electro cyclone resonance plasma (ECRP). Manufacturing method. The method of claim 7, wherein The pressure condition of the first electrode forming step, the electrode post-processing step, the light emitting portion forming step and the second electrode forming step is 10 ^-3 ~ 10 Torr, the manufacturing method of the electroluminescent device. The method of claim 7, wherein The method of manufacturing an electroluminescent device according to claim 1, wherein the light emitting layer is formed of an organic material.

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