KR20050121425A - A plat panel display unit with high light coupling efficiency and low contact resistance - Google Patents

Abstract

Disclosed is a flat panel display device which increases the light transmittance (light efficiency) and at the same time reduces the influence of contact resistance values between members having a large work function difference. The flat panel display device forms an active layer and a pixel electrode in contact with a substrate, and directly connects the active layer and the pixel electrode to each other. In addition, the active layer and the pixel electrode are connected by using a conductive layer. The light transmittance of the pixel is improved by directly connecting the active layer and the pixel electrode. By using the conductive layer to connect the active layer and the pixel electrode once again, the influence of the Schottky contact resistance existing between the active layer and the electrode is reduced.

Description

A plate panel display unit with high light coupling efficiency and low contact resistance

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat panel display device, and more particularly, to a flat panel display device for extending the aperture ratio and transmittance.

In general, flat display devices can be classified into light emitting type and light receiving type. The light emitting type includes a flat cathode ray tube, a plasma display panel, an electroluminescent device, a light emitting diode, and the like. A light receiving type includes a liquid crystal display.

Among them, the electroluminescent display device has attracted attention as a next generation display device because of its advantages of having a wide viewing angle, excellent contrast, and fast response speed. The electroluminescent display may be classified into an inorganic electroluminescent display and an organic electroluminescent display according to a material forming the light emitting layer.

Inorganic electroluminescent displays have been commercialized as green light emitting displays initially, but they are alternating current bias drives, similar to plasma displays, and require several hundred volts to drive. In addition, since the material for emitting light is an inorganic material, it is difficult to control the light emission wavelength due to the molecular design and colorize the image.

In contrast, the organic electroluminescent display device is a self-luminous display device that electrically excites fluorescent organic compounds to emit light, and is capable of driving at low voltage, is easy to thin, and has a wide viewing angle and quick response. It is attracting attention as a next-generation flat panel display that can solve the problem pointed out.

The organic electroluminescent display includes an organic light emitting film made of an organic material between an anode electrode and a cathode electrode, and holes are injected from the anode into the hole transport layer as voltage is applied to the anode electrode and the cathode electrode, respectively. The electrons are moved to the organic light emitting film via the electrons, and the electrons are moved from the cathode to the organic light emitting film via the electron transport layer, whereby electrons and holes recombine in the organic light emitting film to generate excitons.

As the excitons change from the excited state to the ground state, the fluorescent molecules in the light emitting layer emit light to form an image. In the case of a full color organic electroluminescent display, a full color is realized by providing pixels emitting three colors of red, green, and blue.

The anode, organic material and cathode form a light emitting device, which is present on top of a constant layer where a thin film transistor for driving the light emitting device is produced. The thin film transistor is formed on the substrate and described in terms of structure from the substrate to the upper portion, and constitutes an active layer, a gate insulating layer, an interlayer insulating film, and a conductive layer. Finally, after the formation of the conductive layer, the light emitting device is formed after coating the flattening layer. In the case of the bottom light emitting device, the light emitted must pass through the thick planarization region generated to distinguish the thin film transistor from the light emitting device, thereby reducing the light transmittance (light efficiency).

An object of the present invention is to provide a flat panel display unit which improves light transmittance (or light efficiency) and at the same time reduces the influence of contact resistance between members having a large work function difference.

In another aspect, a light emitting display device includes an active layer, a pixel electrode, and a conductive layer.

The active layer is provided in a pixel and becomes a channel, a drain, and a source region of the thin film transistor. The pixel electrode is provided in the pixel and contacts the active layer. The conductive layer is in contact with the active layer and the pixel electrode.

DETAILED DESCRIPTION In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings that illustrate preferred embodiments of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals in the drawings denote like elements.

1 is a cross-sectional view of a light emitting display device according to an embodiment of the present invention.

Referring to FIG. 1, the flat panel display device 100 is formed on a substrate 10.

If the components of the flat panel display 100 formed on the substrate 10 are arranged in the order in which they are formed as follows.

1. The active layer 101 is formed on the substrate 10.

2. The first electrode 102 serving as one electrode of the light emitting element is formed.

3. A gate insulator 103 is formed.

4. The gate electrode 104 is formed.

5. The interlayer 105 is formed.

6. A conductive layer 106 is formed.

7. The planarization layer 107 is formed.

8. The light emitting layer 108 is formed.

9. A second electrode 109 serving as the other electrode of the light emitting element is formed.

The first electrode 102, the light emitting layer 108, and the second electrode 109 are combined to form a light emitting device among the layers formed through the above process.

The light emitting device is controlled by a driving transistor. The driving transistor includes a drain region, a source region, and a channel region, and the regions exist in the active layer 101. That is, the channel region is located under the gate electrode 104, and the drain region and the source region are positioned on the left side and the right side of the gate electrode 104, respectively.

Since light generated in the light emitting layer 108 only needs to pass through the region of the first electrode 102, it can be easily seen that the light efficiency of the light emitting layer 108 is improved compared to the light efficiency when passing through the thick planarization layer 107 as in the conventional case.

In this case, however, the contact characteristic between the first electrode 102 and the active layer 101 becomes a schottky contact. In general, the electrical connection characteristics generated when the two members having different work functions are divided into schottky contacts and ohmic contacts. The Schottky contact occurs when the work function difference is quite large, and the contact resistance value is large. A significant voltage drop occurs at this contact portion, resulting in poor electrical connection between the two members. If the work function difference is not large or the same two members are in contact, the contact between them is called an ohmic contact, and has a relatively low contact resistance value compared to a Schottky contact.

Therefore, in order for the two members to be connected without any adverse electrical effects such as excessive voltage drop, the work function difference of the two members should generally be small. However, in the process of making a product, it is inevitable that a material having a large work function difference must be electrically connected.

The flat panel display device according to the present invention further proposes an ohmic contact resistance connector 110.

FIG. 2 is an enlarged view of the ohmic contact resistance connecting unit 110 shown in FIG. 1.

Referring to FIG. 2, in the ohmic contact resistance connecting unit 110, an active layer 101 and a first electrode 102 are positioned on the substrate 10.

In the drawing, a portion of the active layer 101 is positioned below the portion of the first electrode 102, but vice versa.

3 is an enlarged view of another example of the ohmic contact resistance connection unit 110 shown in FIG. 1.

Referring to FIG. 3, in the ohmic contact resistance connector 110 shown in FIG. 1, the spatial positions of the active layer 101 and the first electrode 102 are opposite to those shown in FIG. 2. In order to form such a structure, it is possible to change a certain order of the processes used when forming the structure shown in FIG.

Hereinafter, the structure shown in FIG. 2 will be described. However, since it is natural to extend and apply the structure shown in FIG. 3, the description of FIG. 3 will be omitted.

An insulating layer 103 is formed on the active layer 101 and the first electrode 102. The insulating layer 103 forms a transistor together with the gate electrode 104 and the active layer 101. The intermediate layer 105 for step coverage of the conductive layer 106 is formed on the active layer 101, the first electrode 102, the insulating layer 103, and the gate electrode 104.

The flat panel display and the ohmic contact connection structure according to the present invention have an idea of electrically connecting the active layer 101 and the first electrode 102 using a via contact, which does not exist in the conventional flat panel display. There is a key point.

In this way, the Schottky contact resistance generated when the two members having a large work function difference are contacted in parallel using a conductive layer as well as the contact of the two members. Can almost eliminate the effect. This has the same effect as the addition of a new electrical connection path having ohmic characteristics in the region other than the direct contact portion where the Schottky contact resistance is generated. In addition, instead of directly contacting two members having a large work function difference, the effect is almost the same even if they are connected using a conductive layer. In order to realize the present invention in an actual product, a new mask is not required or a process is not added. However, when the masking work is required to add a blank contact in the area, the work is nothing compared to the resulting electrical characteristics.

In order for the electrical characteristics to be good, the following conditions must be satisfied instead of the structure shown in FIG. That is, the contact length L2 of the active layer 101 and the first electrode 102 is at least 0.5. Should be at least In addition, the contact length L3 of the conductive layer 106 and the active layer 101 and the contact length L1 of the conductive layer 106 and the first electrode 102 are also at least 0.5. It should have a contact length longer than that.

The conductive layer 106 is generally used to electrically connect the source and / or drain, which is preferably a metal material.

A cross-sectional view of a flat panel display and an ohmic contact connection structure according to an exemplary embodiment of the present disclosure illustrated in FIG. 1 illustrates a part of a pixel.

As described above, the optimum embodiment has been disclosed in the drawings and the specification. Although specific terms have been used herein, they are used only for the purpose of describing the present invention and are not intended to limit the scope of the invention as defined in the claims or the claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, the flat panel display device according to the present invention increases the light efficiency by reducing the thickness of the layer through which the light generated in the light emitting layer passes. In addition, by providing an ohmic contact connecting structure between the active layer and the electrode, there is an advantage that the contact resistance of the active layer and the electrode is considerably reduced.

1 is a cross-sectional view of a light emitting display device according to an embodiment of the present invention.

FIG. 2 is an enlarged view of the ohmic contact resistance connecting unit 110 shown in FIG. 1.

3 is an enlarged view of another example of the ohmic contact resistance connection unit 110 shown in FIG. 1.

<Explanation of symbols for the main parts of the drawings>

10 ... substrate 105 ... Inter Layer 101 ... Active Layer 106 ... Conductive layer

102 first electrode (Anode)

103 Insulator 108 Light emitting layer

104 ... gate electrode (G) 109 ... second electrode (Cathode)

110 ... Ohmic Contact Area

Claims (10)

A thin film transistor provided in a pixel and having an active layer; A pixel electrode provided in the pixel and in contact with the active layer; And Having a conducting layer, And the conductive layer is in contact with the active layer and the pixel electrode. The method of claim 1, And the contact between the active layer and the pixel electrode includes a structure overlapping each other. The method of claim 2, The overlapping structure of claim 1, wherein the active layer is positioned above the pixel electrode. The method of claim 2, The overlapping structure of the flat panel display device, wherein the pixel electrode is located above the active layer. The method of claim 2, The overlapping structure has a contact length of at least 0.5 mu m or more. The method of claim 2, And the conductive layer is positioned above the conductive layer and the pixel electrode. The method of claim 6, The conductive layer and the active layer is at least 0.5 A flat panel display device having the above contact length. The method of claim 6, The conductive layer and the pixel electrode is at least 0.5 A flat panel display device having the above contact length. The method according to any one of claims 1 to 8, Each pixel includes an organic electroluminescent element, And the pixel electrode is any one electrode of the organic electroluminescent element. The method according to any one of claims 1 to 8, And said conductive layer is made of metal.