KR100782025B1 - active matrix organic electroluminescence display and manufacturing method of the same - Google Patents

Abstract

The present invention relates to an active matrix organic electroluminescent device using a thin film transistor and a method of manufacturing the same.

In an active matrix organic electroluminescent device using a conventional amorphous silicon thin film transistor, a light leakage current is generated by external light, thereby deteriorating the light emitting diode and the thin film transistor and deteriorating image quality.

In the active matrix organic electroluminescent device according to the present invention, a light shielding film is formed of an opaque conductive material such as a cathode electrode on the thin film transistor while having a uniform image quality by using an amorphous silicon thin film transistor to block the light leakage current without additional process. Can be. Accordingly, deterioration of the active matrix organic electroluminescent device can be prevented and a highly reliable display device can be provided.

Organic electroluminescent device, thin film transistor, photo leakage current

Description

Active matrix organic electroluminescence display and manufacturing method of the same

1 is a diagram illustrating a circuit structure of one pixel of a general organic electroluminescent device.

2 is a cross-sectional view showing a part of a conventional organic electroluminescent device.

3 is a cross-sectional view showing a part of an organic electroluminescent device according to the present invention.

4A to 4F illustrate a process of manufacturing an organic electroluminescent device according to the present invention.

<Description of reference numerals for main parts of the drawings>

100 substrate 111 gate electrode

120: gate insulating film 131: active layer

141 and 142 ohmic contact layer 151 source electrode

152: drain electrode 160: protective film

161: contact hole 171: cathode electrode

172: Light shielding film 180: Organic layer                 

190: anode electrode T2: thin film transistor

The present invention relates to an organic electroluminescent device, and more particularly, to an active matrix organic electroluminescent device using a thin film transistor and a method of manufacturing the same.

Currently, a cathode ray tube (CRT) is used as a main device in a display device such as a television or a monitor, but this has a problem of weight and volume and high driving voltage. Accordingly, there is a need for a flat panel display having excellent characteristics such as thinness, light weight, and low power consumption, and has emerged, such as a liquid crystal display, a plasma display panel, and an electric field emission. Various flat panel display devices such as a field emission display and an electroluminescent display (or electroluminescence display (ELD)) have been researched and developed.

The dual electroluminescent device is a display device using an electroluminescence (EL) phenomenon in which light is generated when a certain electric field is applied to a phosphor, and an inorganic electroluminescent device and an organic electroluminescent device depending on a source causing excitation of carriers. (organic electroluminescence display: OELD or organic ELD).                         

Among them, the organic electroluminescent device is attracting attention as a natural color display device because it emits light in all regions of visible light including blue, and has high luminance and low operating voltage characteristics. In addition, because of self-luminous, the contrast ratio is high, the ultra-thin display can be realized, and the process is simple, so that environmental pollution is relatively low. On the other hand, the response time is easy to implement a moving picture of a few microseconds, there is no restriction on the viewing angle, stable at low temperatures, and driven at a low voltage of DC 5 to 15V, it is easy to manufacture and design a drive circuit.

The organic electroluminescent device has a structure similar to that of an inorganic electroluminescent device, but the light emitting principle is called organic light emitting diode (OLED) because the light emission is achieved by recombination of electrons and holes. Therefore, hereinafter, referred to as organic LED.

An active matrix type in which a plurality of pixels are arranged in a matrix and a thin film transistor is connected to each pixel is widely used in a flat panel display, and an active matrix organic LED applying the same to an organic electroluminescent device: AMOLED) will be described with reference to the accompanying drawings.

1 illustrates a circuit structure of one pixel of an active matrix organic LED, and as illustrated, one pixel of the active matrix organic LED includes a switching thin film transistor 14 and a driving thin film transistor 15. , A storage capacitor 16, and a light emitting diode 17.

Here, the gate electrode of the switching thin film transistor 14 is connected to the gate wiring 11, and the source electrode is connected to the data wiring 12. The drain electrode of the switching thin film transistor 14 is connected with the gate electrode of the driving thin film transistor 15, and the drain electrode of the driving thin film transistor 15 is connected with the cathode electrode of the light emitting diode 17. The source electrode of the thin film transistor 15 is grounded. Meanwhile, an anode electrode of the light emitting diode 17 is connected to a power line 13, and a storage capacitor 16 is connected to a gate electrode and a source electrode of the driving thin film transistor 15. .

Therefore, when a signal is applied through the gate line 11, the switching thin film transistor 14 is turned on, and the signal of the data line 12 is transferred to the gate electrode of the driving thin film transistor 15 to provide a driving thin film transistor ( Since 15 is turned on, light is output through the light emitting diode 17. In this case, the storage capacitor 16 maintains the gate voltage of the driving thin film transistor 15 when the switching thin film transistor 14 is turned off.

In general, a polycrystalline silicon thin film transistor is used as the switching thin film transistor 14 and the driving thin film transistor 15 of the active matrix organic LED. However, the polycrystalline silicon thin film transistor has a disadvantage in that a large area is difficult due to the complicated manufacturing process and the degree of crystallization of the silicon film is not uniform, and the stability of the device is poor, resulting in low uniformity of image quality. An example used for a driving thin film transistor is shown in Korean Patent Application No. 1999-39695.                         

As shown in FIG. 2, a part of a conventional active matrix organic LED using an amorphous silicon thin film transistor is illustrated in FIG. 2, which is a sectional view of a driving thin film transistor and a light emitting diode.

As illustrated, a gate electrode 21 made of a conductive material such as a metal is formed on the transparent substrate 20, and a gate insulating film 22 is formed thereon to cover the gate electrode 21. An active layer 23 made of amorphous silicon is formed on the gate insulating layer 22 on the gate electrode 21, and ohmic contact layers 24a and 24b made of amorphous silicon doped with impurities are formed thereon.

Source and drain electrodes 25a and 25b made of a conductive material such as a metal are formed on the ohmic contact layers 24a and 24b, and the source and drain electrodes 25a and 25b are formed together with the gate electrode 21. (T1).

Next, a passivation layer 26 is formed on the source and drain electrodes 25a and 25b, and the passivation layer 26 has a contact hole 26c exposing the drain electrode 25b.

The cathode electrode 27 of the light emitting diode is formed in the pixel area above the passivation layer 26, and the cathode electrode 27 is connected to the drain electrode 25b through the contact hole 26c.

Next, an organic layer 28 is formed on the cathode electrode 27 so as to correspond to the cathode electrode 27, and an anode electrode 29 made of a transparent conductive material is formed on the entire surface thereof. Here, the organic layer 28 receives electrons from the cathode electrode 27 and receives holes from the anode electrode 29, and emits light by generating energy when the electrons and holes combine.

However, since the amorphous silicon thin film transistor is very sensitive to light, it is incident on the active layer between the source and the drain to generate a light leakage current. The light that causes the light leakage current includes internal light generated when the light emitting diode emits light and external light such as external sunlight or indoor fluorescent light or incandescent light. Most light leakage current is mainly generated by external light.

This light leakage current changes depending on the amount of light to be irradiated, but in severe cases, it leaks to several nano ampere (nA: nano ampere), and light does not emit light when a few milliseconds have elapsed after emitting light. Will be created.

In addition, since light is emitted from the light emitting diode even when it is not desired by the light leakage current, the thin film transistor and the light emitting diode are deteriorated.

The present invention has been made to solve the above problems, an object of the present invention is to form a light-shielding film on the top of the thin film transistor to prevent the light leakage current of the thin film transistor, the active matrix organic LED having excellent image quality without additional process and The manufacturing method is provided.

In the active matrix organic LED according to the present invention for achieving the above object, a thin film transistor including a gate electrode, a source, and a drain electrode is formed on a substrate, and a protective film having a contact hole covering the thin film transistor and exposing the drain electrode is formed. It is. Next, a light shielding film corresponding to the cathode electrode and the thin film transistor that contacts the drain electrode through the contact hole is formed on the passivation layer. Subsequently, an organic layer is formed on the cathode electrode, and an anode electrode formed of a transparent conductive material is formed on the organic layer.

Here, the light blocking film may be made of the same material as the cathode electrode.

In addition, the thin film transistor may include an active layer, and the active layer may be made of amorphous silicon.

In the method of manufacturing an active matrix organic LED according to the present invention, a substrate is provided and a gate electrode is formed thereon. Next, a gate insulating film covering the gate electrode is formed, and an active layer is formed of amorphous silicon on the gate insulating film over the gate electrode. Next, an ohmic contact layer is formed on the active layer, and then source and drain electrodes are formed thereon. Next, a passivation layer covering the source and drain electrodes and having a contact hole exposing the drain electrode is formed, and a light blocking film corresponding to the cathode electrode and the active layer connected to the drain electrode through the contact hole is formed on the passivation layer. Next, an organic layer is formed on the cathode electrode, and an anode electrode is formed thereon with a transparent conductive material.

Here, the cathode electrode and the light shielding film may be formed through a photolithography process or by an evaporation method using a shadow mask.

As described above, in the active matrix organic LED according to the present invention, in using an amorphous silicon thin film transistor, by forming a light shielding film made of a material such as a cathode on the thin film transistor, it is possible to prevent the light leakage current without adding a process. .

Hereinafter, an active matrix organic LED and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.

First, FIG. 3 is a cross-sectional view of a driving thin film transistor and a light emitting diode as a partial view of an active matrix organic LED according to the present invention.

As shown in FIG. 3, a gate electrode 111 made of a conductive material such as a metal is formed on the transparent insulating substrate 100, and a gate made of silicon nitride film (SiN _x ) or silicon oxide film (SiO ₂ ) is formed thereon. An insulating film 120 is formed to cover the gate electrode 111. Next, an active layer 131 made of amorphous silicon is formed on the gate insulating layer 120 on the gate electrode 111, and ohmic contact layers 141 and 142 made of amorphous silicon doped with impurities are formed thereon. have.

Source and drain electrodes 151 and 152 formed of a conductive material such as a metal are formed on the ohmic contact layers 141 and 142. The source and drain electrodes 151 and 152 are formed together with the gate electrode 111. (T2).

Next, a passivation layer 160 made of an organic material is formed on the source and drain electrodes 151 and 152, and the passivation layer 160 has a contact hole 161 exposing the drain electrode 152.

The cathode electrode 171 and the light blocking film 172 of the light emitting diode are formed on the passivation layer 160. The light blocking film 172 enters the active layer 131 in which the channel is formed corresponding to the thin film transistor T2. To prevent them. Meanwhile, the cathode electrode 171 is connected to the drain electrode 152 through the contact hole 161.

Next, an organic layer 180 for generating light is formed on the cathode electrode 171 so as to correspond to the cathode electrode 171, and an anode electrode 190 made of a transparent conductive material is formed on the entire surface of the substrate. Here, the organic layer 28 may be formed to represent red, green, and blue colors, respectively, so that one color is displayed in one pixel.

Meanwhile, in the present invention, the thin film transistor T2 is preferably an n-type having electrons as a carrier, and in the case of a p-type having holes as a carrier, the positions of the cathode electrode 171 and the anode electrode 190 should be changed. That is, in the case of the p-type thin film transistor T2, the anode electrode is formed at the bottom to be connected to the thin film transistor T2 and the cathode electrode is formed at the top.

Next, a process of manufacturing an active matrix organic LED according to the present invention corresponding to FIG. 3 is illustrated in FIGS. 4A to 4F.

As shown in FIG. 4A, a gate electrode 111 is formed by depositing and patterning a conductive material such as a metal on the insulating substrate 100. In this case, the insulating substrate 100 may be a transparent substrate such as glass or plastic, and the gate electrode 111 may be formed of a material having a relatively low resistance.

Subsequently, as shown in FIG. 4B, the gate insulating layer 120 is deposited, and amorphous silicon and the doped amorphous silicon are sequentially deposited and then patterned to form the active layer 131 and the impurities on the gate electrode 111. The semiconductor layer 143 is formed.

Next, as illustrated in FIG. 4C, a conductive material such as a metal is deposited and patterned to form source and drain electrodes 151 and 152 on the impurity semiconductor layer 143 of FIG. 4B, and then the exposed impurity semiconductor layer (FIG. The ohmic contact layers 141 and 142 are completed by removing 143 of 4b. In this case, the source and drain electrodes 151 and 152 form the thin film transistor T2 together with the gate electrode 111.

Next, as shown in FIG. 4D, the passivation layer 160 is formed of an organic material, and then patterned to form a contact hole 161 exposing the drain electrode 152.

Next, as shown in FIG. 4E, the cathode electrode 171 and the light shielding film 172 are formed. The cathode electrode 171 and the light shielding film 172 are formed by depositing a conductive material such as a metal, and then applying a photosensitive film to the photomask. It may be formed by a photolithography process that is exposed and developed to be etched, or by placing a shadow mask on the surface of the substrate on which the pattern is to be formed, and applying a high current to the source material instantaneously to coat it by evaporating the source material. It may be formed by an evaporation method. In this case, the cathode electrode 171 is connected to the drain electrode 152 through the contact hole 161, and the light blocking film 172 is positioned on the thin film transistor T2 and is an active layer of the thin film transistor T2 made of amorphous silicon. 131 prevents light from entering. Here, the cathode electrode 171 has a low work function and is preferably made of an opaque material capable of blocking light, and the material may be made of an alloy material including aluminum, an aluminum alloy material, or magnesium.

Subsequently, as illustrated in FIG. 4F, the organic layer 180, which is a light emitting layer, is formed on the cathode electrode 171, and the anode electrode 190 is formed thereon. In this case, the anode electrode 190 is preferably made of a transparent conductive material, it may be formed on the entire surface of the substrate. Indium-tin-oxide (ITO) may be used as the transparent conductive material. Since ITO is formed by a method such as sputtering, since the organic layer 180 may be damaged, a metal thin film is disposed on the lower portion. It is better to form a thin and form ITO. In this case, since light must be emitted through the anode electrode 180, the metal thin film is preferably formed to be thin so that the transmittance of the anode electrode 180 is at least 80% or more. As a material of the metal thin film, a material having a relatively large work function is used, for example, silver (Au) or platinum (Pt), and when using silver or platinum, the thickness of the thin film may be 50 Å or less.

As described above, in the active matrix organic LED and a method of manufacturing the same according to the present invention, a light shielding film may be formed on the thin film transistor to prevent photo leakage current, but the process is not added since the light shielding film is formed of a cathode electrode material.

The present invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit of the present invention.

In the active matrix organic LED according to the present invention and a method of manufacturing the same, a display device having excellent image quality can be obtained using an amorphous silicon thin film transistor, and a light shielding film is formed on the thin film transistor using a material such as a cathode electrode, thereby eliminating the need for additional light Leakage current can be prevented. In addition, it is possible to prevent deterioration of the thin film transistor and the light emitting diode by blocking the light leakage current.

Claims (6)

A substrate; A thin film transistor formed on the substrate and comprising a gate electrode, a source and a drain electrode; A passivation layer covering the thin film transistor and having a contact hole exposing the drain electrode; A cathode electrode formed on the passivation layer and in contact with the drain electrode through the contact hole; A light blocking film formed over the passivation film and corresponding to the thin film transistor; An organic layer on the cathode electrode; An anode covering the organic layer and made of a transparent conductive material Active matrix organic LED comprising a. The method of claim 1, The light blocking film is an active matrix organic LED made of the same material as the cathode electrode. The method of claim 1, The thin film transistor includes an active layer, and the active layer is formed of amorphous silicon. Providing a substrate; Forming a gate electrode on the substrate; Forming a gate insulating film covering the gate electrode; Forming an active layer of amorphous silicon on the gate insulating layer on the gate electrode; Forming an ohmic contact layer on the active layer; Forming a source and a drain electrode on the ohmic contact layer; Forming a passivation layer covering the source and drain electrodes and having a contact hole exposing the drain electrode; Forming a cathode electrode connected to the drain electrode through the contact hole on the passivation layer and a light shielding film corresponding to the active layer; Forming an organic layer on the cathode electrode; Forming an anode electrode on the organic layer with a transparent conductive material Method for manufacturing an active matrix organic LED comprising a. The method of claim 4, wherein The cathode electrode and the light shielding film are formed by a photolithography process. The method of claim 4, wherein The cathode electrode and the light shielding film are formed by an evaporation method using a shadow mask.

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