KR20020078535A - Method for fabricating OELD device - Google Patents

Abstract

PURPOSE: A method for fabricating an organic field emission display device is provided to prevent diffusion of a cathode electrode metal to a TFT(Thin Film Transistor) by forming a cathode electrode as a metal material of a low work function and a low diffusion ratio. CONSTITUTION: A TFT device is formed on a substrate(110) by a semiconductor layer(130), a gate electrode(150), and a source/drain electrode(170,175). The third interlayer dielectric(180) is formed on a whole surface of the substrate(110). A contact hole is formed on a predetermined position of the third interlayer dielectric(180). An ITO layer is formed on the third interlayer dielectric(180). An anode electrode(200) is formed by etching the ITO layer. A protective layer(210) is formed thereon. A contact hole for pixel is formed on an upper face of the protective layer(210). A light emission device layer(220) is formed by coating an organic material on the contact hole for pixel. A cathode electrode portion is formed by depositing a cathode metal on an upper face of the light emission device layer(220).

Description

Method for manufacturing organic electroluminescent display {Method for fabricating OELD device}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an organic light emitting display device, and more particularly, an electrical property of a product by depositing a metal having a lower work function and lower diffusion than an anode electrode on an upper surface of a light emitting device layer that emits light itself The present invention relates to a method of manufacturing an organic light emitting display device for improving the quality.

Cathode ray tube (CRT), which is one of the commonly used display devices, is mainly used for monitors such as televisions, measuring devices, information terminal devices, etc., but due to the weight and size of the CRT itself, miniaturization of electronic products It cannot actively respond to the demand for weight reduction.

In order to replace such a CRT, a flat panel display device having the advantages of small size and light weight has been attracting attention. Among flat panel displays, a liquid crystal display that displays information by using the electro-optical properties of liquid crystals injected into the LCD panel, and an organic electroluminescent display in which organic materials emit light by current flow are active. In recent years, as the information society is socialized, the importance of the liquid crystal display and the organic light emitting display is gradually increasing.

Recently, an organic electroluminescent display (LCD), which emits light by a current flow, has attracted attention as a next-generation flat panel display succeeding a liquid crystal display. This is because the organic electroluminescent device emits light by itself, which does not require a backlight assembly required in the liquid crystal display device, which makes the organic electroluminescent display device lighter and thinner than the liquid crystal display device, and there is no limitation in the viewing angle.

Recently, the development of an organic light emitting display device in which an organic light emitting diode having such an advantage and a thin film transistor for driving the organic light emitting diode has been developed has been actively developed.

As described above, the organic light emitting display device including the organic light emitting device and the thin film transistor (hereinafter, referred to as TFT) that is a switching device includes first and second signal lines arranged in a matrix and intersecting regions of the signal lines. It consists of a TFT, a charging capacitor, and an organic electroluminescent element which emits light by itself.

Here, the signal lines are composed of data lines, power supply lines formed in parallel to the data lines, and gate lines formed to cross the data lines and the power supply line.

The first and second TFTs are largely composed of a semiconductor layer, a gate electrode, and a source / drain electrode, and the charging capacitor is composed of a first electrode, a dielectric, and a second electrode.

In addition, the organic electroluminescent device includes an anode electrode, a light emitting device layer, and a cathode electrode, and recently, an auxiliary cathode electrode layer is formed between the light emitting device layer and the cathode electrode in order to lower the work function of the cathode electrode than the anode electrode.

Here, the cathode electrode is formed using pure aluminum, and the auxiliary cathode electrode layer is formed using LiF, which is a light alkali metal having a low work function.

However, when the auxiliary cathode electrode layer is formed of LiF metal, Li included in the LiF metal has a very high diffusivity and reactivity, so that when the organic electroluminescent display is driven for a predetermined time, the Li metal component becomes the anode electrode over time. And diffused into the TFT device formed under the organic electroluminescent device, thereby degrading the characteristics of the TFT device.

In other words, when the Li metal forming the auxiliary cathode electrode layer is diffused into the TFT element, the voltage at which the TFT is turned on becomes uneven and the degree of change is changed when used for a long time, thereby reducing the reliability of the product.

Accordingly, it is an object of the present invention to form a cathode electrode from a metal material having a low work function and a low diffusivity, thereby preventing the cathode electrode metal from diffusing to the TFT formed below and simplifying the manufacturing process.

Another object of the present invention is to improve the reliability of the product by forming the auxiliary cathode electrode of a metal having a low work function and low diffusion between the light emitting device layer and the cathode electrode.

Still other objects of the present invention will become more apparent from the following detailed description and the accompanying drawings.

1 is a cross-sectional view showing a state in which a TFT of an organic light emitting display device according to the present invention is formed.

2 is a cross-sectional view illustrating a state in which contact holes are formed in an interlayer insulating film and an interlayer insulating film insulating the TFT and the organic EL device according to the present invention;

3 is a cross-sectional view showing a state in which an anode electrode according to the present invention is formed.

4 is a cross-sectional view illustrating a state in which contact holes for pixels are formed in the planarization protective layer and the planarization protective layer according to the present invention.

5 is a cross-sectional view showing a state in which a light emitting device layer according to the present invention is formed.

6 is a cross-sectional view of a cathode electrode part according to a first embodiment of the present invention;

7 is a cross-sectional view showing a cathode electrode according to a second embodiment of the present invention.

In order to achieve the above object, the present invention forms anode electrodes by depositing a transparent metal that transmits light on the upper surface of the substrate, applying a predetermined insulating material to the upper surface of the anode electrode and applying a predetermined portion of the insulating material. After forming a useful contact hole and exposing the anode to the outside, an organic material having a predetermined color is applied to the pixel contact hole to form a light emitting device layer that emits light by the flow of current. A metal having a low work function and for which the metal component does not diffuse into the lower layer is deposited on the light emitting device layer to form a cathode electrode part.

For example, the cathode electrode part is formed as a single layer using a metal having a lower work function than the anode electrode and the metal component does not diffuse into the lower layer.

As another example, the cathode electrode part includes an auxiliary cathode electrode layer formed of a metal having a low work function and non-diffusion on the upper surface of the light emitting device layer, and a cathode electrode formed of pure aluminum on the upper surface of the auxiliary cathode electrode layer.

Preferably, the metal having a low work function and no diffusion is a metal containing Nd.

Hereinafter, an example of a method of manufacturing an organic electroluminescent display including an organic electroluminescent device for emitting light and a TFT for driving the organic electroluminescent device according to the present invention will be described with reference to the accompanying drawings. The following description will be made with reference to FIG. 7.

In the organic electroluminescent display device according to the present invention, the organic electroluminescent display device 100 according to the present invention includes a substrate 110 through which light is largely transmitted, and a plurality of signal lines arranged in a matrix form on an upper surface of the substrate 110. (Not shown) and pixel areas (not shown) formed at intersection regions of the signal lines 120, 130, and 135, respectively.

In each pixel area 140, two TFTs 150 and 200, a charging capacitor 190, and an organic EL device 300 that emits light by itself are formed.

The first TFT of the two TFTs serves to charge the charging capacitor so that the organic electroluminescent display 100 can maintain its image for one frame, and the second TFT is electrically connected to the charging capacitor and the organic electroluminescent element. The driving current is supplied to the organic electroluminescent device.

Since only the second TFT and the organic EL device directly related to the present invention are shown here, the following description will focus on the second TFT and the organic EL device.

As described above, the TFT includes a semiconductor layer 130, a first interlayer insulating layer 140 formed on an upper surface of the semiconductor layer 130 to insulate the semiconductor layer 130 and the upper electrode, A gate electrode 150 formed on a portion of the upper surface of the first interlayer insulating layer 140 corresponding to the center portion of the semiconductor layer 130, and formed on the entire surface of the substrate to cover the upper surface of the gate electrode 150. A second interlayer insulating layer 160 that insulates the gate electrode 150 and the upper electrode, and has contact holes formed in a predetermined portion, and is formed in a predetermined portion of an upper surface of the second interlayer insulating layer 160, and has one end of the semiconductor layer through the contact hole. And source / drain electrodes 170 and 175 respectively connected to the part and the other end.

Although not shown, the source electrode of the first TFT extends from the signal lines to one end of the semiconductor layer, and the drain electrode of the first TFT extends from the other end of the semiconductor layer to the charging capacitor.

6 and 7, the source electrode 170 of the second TFT extends from signal lines to one end of the semiconductor layer 130, and the drain electrode 175 of the second TFT is formed of a semiconductor layer ( It extends from the other end of 130 to the organic electroluminescent element.

Although not shown, the charging capacitor is formed together with the gate electrode 150 and connects the first electrode and the upper surface of the first electrode to be connected to the drain electrode of the first TFT through a contact hole formed in the second interlayer insulating layer 160. And a second electrode formed on the covering dielectric layer and the top surface of the dielectric layer together with the source / drain electrodes 170 and 175 and connected to the signal line.

Preferably, the dielectric layer is a second interlayer insulating film located at the first electrode portion.

Finally, the organic electroluminescent device according to the present invention is a part which displays predetermined image information by dissipating red, green, and blue light by the flow of electric current, as shown in FIG. 6 and FIG. The anode electrode 200 is connected to the drain electrode 175 of the contact hole and receives positive power from the second TFT, and is formed of a metal having a lower work function than the anode electrode and does not diffuse, and is supplied with negative power. The light emitting device layer 220 is formed between the portions 230 and 235 and the anode electrode 200 and the cathode electrode portions 230 and 235 to emit light of a predetermined color by the flow of current.

Here, a third interlayer insulating layer 180 having a contact hole 185 is formed between the source / drain electrodes 170 and 175 and the anode electrode 200, and a TFT is formed between the anode electrode 200 and the cathode electrode portions 230 and 235. The planarization protective film 210 is formed to protect the external environment.

On the other hand, the cathode electrode 230 of the present invention according to the first embodiment is a single film using a metal having a lower work function than the anode electrode and the metal component does not diffuse to the lower layer, that is, the TFT as shown in FIG. Form.

The cathode electrode portions 230 and 235 of the present invention according to the second embodiment of the present invention have a work function lower than the anode electrode 200 and the auxiliary cathode electrode layer 235 formed of the non-diffusion metal as shown in FIG. The upper surface of the auxiliary cathode electrode layer 235 is composed of a cathode electrode 230 made of pure aluminum.

A method of manufacturing the organic light emitting display device configured as described above will be described with reference to FIGS. 1 to 7.

First, as shown in FIG. 1, a TFT device including a semiconductor layer 130, a gate electrode 150, and source / drain electrodes 170 and 175 is formed.

Hereinafter, the process of forming the TFT device will be described in detail.

A buffer layer 120 is formed on the entire upper surface of the substrate 110 to prevent influx of impurities formed in the substrate 110. After the amorphous silicon is applied to the upper surface of the buffer layer 152, the polysilicon is heated by applying heat to the amorphous silicon. Silicon (poly-Si) is formed. Subsequently, polysilicon coated on the entire surface of the substrate 110 is patterned to form the semiconductor layer 130 in a predetermined portion where the TFT is to be formed.

Thereafter, an insulating material is coated on the upper surface of the semiconductor layer 130 to cover the semiconductor layer 130 and the buffer layer 120 to form a first interlayer insulating layer 140 electrically insulating the semiconductor layer 130 and the upper layer. do.

The gate metal 150 is formed on the upper surface of the first interlayer insulating layer 140 and the gate metal is patterned to form the gate electrode 150 in a portion of the first interlayer insulating layer 140 that corresponds to the center of the semiconductor layer 130. do. At this time, the first electrode of the charging capacitor is also formed.

When the gate electrode 150 is formed, an insulating material is coated on the entire surface of the substrate 110 to insulate the gate electrode 150 and the upper electrode, and the second interlayer insulating layer 160 used as a dielectric for the charging capacitor is formed. A contact hole is formed in a predetermined portion of the second interlayer insulating layer 160, that is, a portion corresponding to both end portions of the semiconductor layer 130 and a portion corresponding to the first electrode of the charging capacitor.

Subsequently, the source / drain metal is deposited on the upper surface of the second insulating layer 154 on the upper surface of the second interlayer insulating layer 160, and the source / drain metal is etched to form a gate based on the gate electrode 150. Source / drain electrodes 170 and 175 are formed on both sides of the electrode 150 to be connected to both ends of the semiconductor layer 130 through contact holes. At this time, the second electrode of the charging capacitor is formed together.

When the TFT is formed as described above, organic electroluminescent elements are formed as shown in FIGS. 2 and 7. This will be described in detail as follows.

When the source / drain electrodes are formed, a predetermined insulating material is coated on the entire surface of the substrate 110 to cover the source / drain electrodes 170 and 175 as shown in FIG. 2, so that the source / drain electrodes 170 and 175 and the organic electroluminescence are formed. A third interlayer insulating film 180 is formed to insulate the device. Thereafter, a contact hole 185 is formed in a predetermined portion of the third interlayer insulating layer 180 corresponding to the drain electrode 175 of the second TFT.

Subsequently, a transparent metal that transmits light, for example, ITO metal, is deposited on the upper surface of the third interlayer insulating layer 180, and the organic light emitting diode is formed as shown in FIG. 3 by photolithography of the deposited ITO metal. The anode electrode 200 is formed on the portion to be formed. Here, the anode electrode 200 is electrically connected to the drain electrode 175 of the second TFT through the contact hole 185 to receive positive power.

As described above, an anode electrode is formed, and the source / drain electrodes 170 and 175, the second electrode, and the anode electrode are planarized as shown in FIG. 4 to protect the first and second TFTs and the charging capacitor from the external environment. The planarization protective layer 210 is formed by thickly applying an insulating material to cover the 200. Subsequently, a pixel contact hole 215 having a predetermined size is formed in a portion of the upper surface of the planarization protective layer 210 that corresponds to the anode electrode 200.

As shown in FIG. 5, the organic material having a predetermined color is applied to the peripheral contact portion of the pixel contact hole 215, including the pixel contact hole 215, so that light of a predetermined color is generated by the flow of current. The light emitting device layer 220 that emits itself is formed.

Subsequently, as shown in FIGS. 6 and 7, the cathode metal is deposited on the light emitting device layer 220 so as to cover the light emitting device layer 220 and the planarization protective film 210. Cathode electrode portions 330 and 335 which supply electrons to the 220 are formed.

As shown in FIG. 6, the cathode electrode part 330 according to the first embodiment has a lower work function than the anode electrode 200 and does not diffuse metal into the TFT when the organic electroluminescent display 100 is driven. Is formed on the entire surface of the planarization protective film 210 including the light emitting device layer 220.

When the cathode electrode portion is formed in this manner, the auxiliary cathode electrode, which is conventionally formed to lower the work function of the cathode electrode than the anode electrode, can be simplified because the formation process is omitted.

On the other hand, the cathode electrode unit according to the second embodiment is composed of a cathode electrode and an auxiliary cathode electrode layer which lowers the work function of the cathode electrode than the work function of the anode electrode and stabilizes the cathode electrode.

Hereinafter, the process of forming the cathode electrode unit configured as described above will be described in detail. First, as shown in FIG. 7, the auxiliary cathode electrode layer is formed by depositing a metal having a low work function on the front surface of the substrate including the light emitting device layer and the planarization protective layer and not diffusing to the TFT when the organic light emitting display device is driven. Form.

Thereafter, pure aluminum is vacuum deposited to form a cathode electrode on the upper surface of the auxiliary cathode electrode layer.

Preferably, in the first embodiment and the second embodiment, when the work function of the cathode is lower than the work function of the anode electrode and the organic electroluminescent display is driven, the metal of the system which does not diffuse into the TFT is Nd metal.

That is, in the first embodiment, the cathode electrode part is formed using an aluminum alloy containing Nd metal. Further, the auxiliary cathode electrode portion according to the second embodiment is formed of pure Nd metal or is formed using an aluminum alloy containing Nd metal.

As described above, when the cathode electrode portion is formed using a metal having a lower work function than the anode electrode and which does not diffuse, the metal component can be prevented from entering the lower layer (anode electrode or TFT) formed under the cathode electrode. Therefore, even after a certain time has elapsed, the electrical characteristics of the product is maintained to have a constant effect of improving the reliability of the product.

In addition, since the cathode electrode portion of the single layer can be formed by using a metal having a lower work function than the anode and not diffusing, the manufacturing process of the product is simplified.

In the above-described embodiment, the organic electroluminescent display device in which the TFT and the organic electroluminescent element coexist has been described. However, the present invention may be applied to an organic electroluminescent display device comprising an anode electrode, a light emitting element layer, and a cathode electrode portion on a substrate. It's okay.

Claims (5)

In the manufacturing method of an organic light emitting display device comprising an organic electroluminescent element that emits light itself by the flow of current, Depositing a transparent metal that transmits light onto the upper surface of the substrate to form anode electrodes; Coating a predetermined insulating material on an upper surface of the anode electrode and forming a contact hole for a pixel in a predetermined portion of the insulating material to expose the anode electrode to the outside; Coating an organic material having a predetermined color in the pixel contact hole to form a light emitting device layer that emits light by current flow; And depositing a metal having a work function lower than that of the anode and in which a metal component is not diffused into a lower layer on the light emitting device layer, thereby forming a cathode electrode part. The method of claim 1, wherein the cathode electrode part is formed of a single layer using a metal having a work function lower than that of the anode and the metal component does not diffuse into the lower layer. The method of claim 1, wherein the cathode electrode portion An auxiliary cathode electrode layer formed by depositing a metal having a work function lower than the anode electrode and having no metal component diffused to the lower layer on the light emitting device layer; And a cathode electrode formed by depositing a predetermined metal on an upper surface of the auxiliary cathode electrode layer. The method of claim 3, wherein the predetermined metal forming the cathode is pure aluminum. The metal according to any one of claims 1 to 3, wherein the metal having a work function lower than that of the anode electrode and the metal component does not diffuse into the lower layer is Nd or an aluminum alloy containing Nd. A method of manufacturing an organic electroluminescent display.