KR100453633B1 - an active matrix organic electroluminescence display and a manufacturing method of the same - Google Patents

Abstract

The present invention relates to an active matrix organic electroluminescent device.

Since the active matrix organic electroluminescent device includes a plurality of thin film transistors in one pixel, the area of the pixel electrode is reduced and the aperture ratio is decreased. In order to prevent this, if the area of the storage capacitor is made small, the capacity of the capacitor is lowered, which causes problems such as leakage of the signal.

In the active matrix organic electroluminescent device according to the present invention, another capacitor electrode is further formed between two electrodes of a general storage capacitor and connected to the upper electrode to reduce the thickness of the storage capacitor, so that the capacitor is reduced even if the area of the storage capacitor is reduced. The capacity can be prevented from being lowered and the aperture ratio can be improved.

Description

Active matrix organic electroluminescence display and a manufacturing method of the same

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

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 with a few microseconds, there is no restriction on the viewing angle, it is stable even at low temperatures, it is easy to manufacture and design a drive circuit because it is driven at a low voltage of DC 5V to 15V.

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 shows a circuit structure of one pixel of an active matrix organic LED, and as shown, one pixel of an active matrix organic LED includes a switching thin film transistor 4 and a driving thin film transistor 5. , Storage capacitor 6, and light emitting diode 7.

Here, the gate electrode of the switching thin film transistor 4 is connected to the gate wiring 1, and the source electrode is connected to the data wiring 2. The drain electrode of the switching thin film transistor 4 is connected to the gate electrode of the driving thin film transistor 5, and the drain electrode of the driving thin film transistor 5 is connected to the anode electrode of the light emitting diode 7. The source electrode of the driving thin film transistor 5 is connected to the power line 3, and the cathode electrode of the light emitting diode 7 is grounded. Next, the storage capacitor 6 is connected to the gate electrode and the source electrode of the driving thin film transistor 5.

Therefore, when a signal is applied through the gate wiring 1, the switching thin film transistor 4 is turned on, and the signal of the data wiring 2 is transferred to the gate electrode of the driving thin film transistor 5, thereby driving the driving thin film transistor ( Since 5) is turned on, light is output through the light emitting diode 7. In this case, when the switching thin film transistor 4 is turned off, the storage capacitor 6 maintains the gate voltage of the driving thin film transistor 5 constantly.

A plan view of one pixel in such a conventional active matrix organic LED is shown in FIG. 2.

As shown in FIG. 2, the gate line 41 and the data line 61 intersect to define one pixel region P, and the power line 67 is formed to be parallel to the data line 61. .

A switching thin film transistor Ts is formed at a portion where the gate wiring 41 and the data wiring 61 intersect to be connected to the gate wiring 41 and the data wiring 61, and the switching thin film is in the pixel region P. A driving thin film transistor Td connected to the transistor Ts is formed.

As mentioned above, the gate electrode 42 of the driving thin film transistor Td is connected to the drain electrode of the switching thin film transistor Ts and is connected to the first capacitor electrode 45. Next, the source electrode 62 of the driving thin film transistor Td contacts the source region 22 through the first contact hole 50a and is connected to the second capacitor electrode 65, and the second capacitor electrode 65. ) Is an extension of the power line 67. The second capacitor electrode 65 overlaps the first capacitor electrode 45 to form a storage capacitor. In addition, the drain region 23 of the driving thin film transistor Td is connected to the pixel electrode 81 through the second contact hole 50b.

3 is a cross-sectional view taken along the line III-III of FIG. 2 in the active matrix organic LED having such a structure.

As illustrated, polycrystalline silicon layers 21, 22, and 23 having an island shape are formed on the substrate 10, which is doped with impurities of the active layer 21 of the thin film transistor. It is divided into source and drain regions 22 and 23.

Subsequently, a gate insulating layer 30 is formed on the polycrystalline silicon layers 21, 22, and 23, and a gate electrode 42 is formed on the gate insulating layer 30 on the active layer 21. In addition, the first capacitor electrode 45 is formed of the same material as the gate electrode 42.

Next, an interlayer insulating film 50 is formed on and covers the gate electrode 42 and the first capacitor electrode 45, and the interlayer insulating film 50 may include a first portion exposing portions of the source and drain regions 22 and 23, respectively. And second contact holes 50a and 50b.

Next, the source electrode 62 and the second capacitor electrode 65 connected to the source electrode 62 are formed of a conductive material such as a metal on the interlayer insulating layer 50. Here, the source electrode 62 is connected to the lower source region 22 through the first contact hole 50a, and the second capacitor electrode 65 overlaps the first capacitor electrode 45 to form a storage capacitor. Achieve.

Subsequently, a protective layer 70 is formed over the entire surface of the substrate 10 to cover the source electrode 62 and the second capacitor electrode 65, and the protective layer 70 is formed on the second contact hole 50b. It has three contact holes 71.

Next, a pixel electrode 81 formed of a transparent conductive material is formed on the passivation layer 70 through the third contact hole 71 and the second contact hole 50b. This pixel electrode 81 becomes an anode electrode of a light emitting diode.

However, in the active matrix organic LED, since a plurality of thin film transistors exist in one pixel, the area of the pixel electrode, which is the anode electrode which forms the actual image, is reduced and the aperture ratio is lowered. Therefore, in order to increase the aperture ratio, the area of the storage capacitor in the pixel needs to be reduced. However, when the area of the storage capacitor is reduced, the capacity of the capacitor decreases, thereby preventing the leakage of the signal.

Accordingly, an example in which the opening ratio is prevented from being lowered by forming the first electrode of the storage capacitor using a material such as an active layer and overlapping the power line to form the storage capacitor is provided. In this case, the interlayer insulating film may be formed as a double layer of the first and second interlayer insulating films, and a power line may be formed between the first and second interlayer insulating films. In this case, the thickness of the storage capacitor may be the thickness of the gate insulating film and the first interlayer insulating film. Is equal to the sum.

However, as is known recently, when four or more thin film transistors are formed in one pixel to improve the image quality, the area of the pixel electrode becomes smaller and the aperture ratio is lowered.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to improve the aperture ratio by reducing the area of the storage capacitor to increase the area of the pixel electrode, thereby increasing the capacitance of the capacitor. To provide an LED.

1 is a circuit diagram of one pixel of a conventional active matrix organic LED.

2 and 3 are cross-sectional views of a conventional active matrix organic LED.

4 is a circuit diagram of one pixel structure of an active matrix organic LED according to the present invention;

5 and 6 are cross-sectional views of an active matrix organic LED according to the present invention.

7A to 7E are cross-sectional views illustrating a manufacturing process of an active matrix organic LED according to the present invention.

<Description of Symbols for Main Parts of Drawings>

210: substrate 225: first capacitor electrode

230: gate insulating film 245: second capacitor electrode

251 first interlayer insulating film 251a contact hole

252: second interlayer insulating film 270: protective layer

291: third capacitor electrode

The present invention for achieving the above object includes a plurality of pixels arranged in a matrix form on the substrate, the pixel includes a light emitting diode and a storage capacitor, a power line connected to the storage capacitor and at least one thin film transistor. In an active matrix organic electroluminescent device, a first capacitor electrode is formed on a substrate, a first insulating film is formed thereon to cover the first capacitor electrode, and a second capacitor electrode is formed on the first insulating film. have. Next, a second insulating film is formed on the second capacitor electrode, the second insulating film having a contact hole exposing the second capacitor electrode. Next, a power line extension part contacting the second capacitor electrode through the contact hole and connected to the power line is formed on the second insulating film, and the third insulating film covers the power line extension part.

Here, the first capacitor electrode may be made of polycrystalline silicon containing impurities.

The thin film transistor may include a gate electrode and a source electrode, the second capacitor electrode may be formed of the same material as the gate electrode, and the second insulating layer and the third insulating layer may be positioned between the gate electrode and the source electrode.

In the present invention, the pixel may include four thin film transistors, each of which may be a first and second switching thin film transistor and a first and second driving thin film transistor.

In the method of manufacturing an active matrix organic electroluminescent device according to the present invention, the substrate includes a plurality of pixels arranged in a matrix form on the substrate, and the pixels include an active matrix organic light-emitting diode, a storage capacitor, and at least one thin film transistor. In an electroluminescent device, a first capacitor electrode is formed on a substrate, and a first insulating film is formed thereon. Next, after forming the second capacitor electrode on the gate insulating film, a second insulating film is formed thereon, and the second insulating film is patterned to form a contact hole exposing the second capacitor electrode. Next, a power line extension is formed on the second insulating layer to contact the second capacitor electrode through the contact hole and to be connected to the power line. Next, a third insulating film is formed on the power line extension.

The forming of the first capacitor electrode may include forming a polycrystalline silicon layer on the substrate and implanting impurities.

The thin film transistor includes a gate electrode and a source electrode, and the gate electrode may be formed in the same process as forming the second capacitor electrode.

Further, the source electrode is formed in the process following the step of forming the third insulating film.

As described above, in the active matrix organic LED according to the present invention, another capacitor electrode is further formed between two electrodes of a general storage capacitor and connected to the upper electrode to reduce the thickness of the storage capacitor, thereby reducing the area of the storage capacitor. It is possible to prevent the capacitor capacity from falling and to improve the aperture ratio.

Hereinafter, an active matrix organic LED according to the present invention will be described in detail with reference to the accompanying drawings.

4 illustrates one pixel structure of an active matrix organic LED according to the present invention. In the present invention, four thin film transistors may be included in one pixel, thereby increasing the uniformity of image quality.

As illustrated, one pixel P1 of the active matrix organic LED according to the present invention is formed by the intersection of the gate wiring 111 and the data wiring 112, and the pixel P1 includes the first and second switching thin film transistors ( 114 and 115, first and second driving thin film transistors 116 and 117, and a storage capacitor 118 and a light emitting diode 119.

Here, the gate electrodes of the first and second switching thin film transistors 114 and 115 are connected to the gate wiring 111, and the source electrode of the first switching thin film transistor 114 is connected to the data wiring 112. The drain electrode of the first switching thin film transistor 114 is connected to the source electrode of the second switching thin film transistor 115.

Next, the source electrode of the first driving thin film transistor 116 is connected to the drain electrode of the first switching thin film transistor 114 and the source electrode of the second switching thin film transistor 115, and the first driving thin film transistor 116 is provided. The gate electrode of is connected to the drain electrode of the second switching thin film transistor 115 and the gate electrode of the second driving thin film transistor 117.

Next, the source electrode of the second driving thin film transistor 117 is connected to the drain electrode and the power line 113 of the first driving thin film transistor 116, and the drain electrode of the second driving thin film transistor 117 is a light emitting diode. 119 is connected to the anode electrode.

Meanwhile, the cathode of the light emitting diode 119 is grounded, and the storage capacitor 118 is connected to the first and second driving thin film transistors 116 and 117. One electrode of the storage capacitor 118 is connected to the drain electrode of the first driving thin film transistor 116 and the source electrode of the second driving thin film transistor 117, and the other electrode is connected to the first and second driving thin film transistor 116. 117 is connected to the gate electrode.

Accordingly, the first and second switching thin film transistors 114 and 115 operate by the signal of the gate wiring 111, and thus the signal of the data wiring 112 is transmitted to the first and second driving thin film transistors 116 and 117. When the second driving thin film transistor 117 is operated by this signal, the image signal Vdd of the power line 113 is transmitted to the light emitting diode 119 to emit light from the light emitting diode 119.

5 and 6 are cross-sectional views of an active matrix organic LED using a thin film transistor according to the present invention. FIG. 5 is a cross-sectional view of a second driving thin film transistor and a light emitting diode, and FIG. 6 is a cross-sectional view of a storage capacitor. .

First, as shown in FIG. 5, polycrystalline silicon layers 221, 222, and 223 having an island shape are formed on the insulating substrate 210. The polycrystalline silicon layer includes an active layer 221 and impurities of the thin film transistor. It is divided into doped source and drain regions 222 and 223. The buffer layer may further include a buffer layer made of a material such as a silicon oxide layer between the substrate 210 and the polycrystalline silicon layers 221, 222, and 223.

Subsequently, a gate insulating film 230 is formed on the polycrystalline silicon layers 221, 222, and 223 using a material such as a silicon nitride film or a silicon oxide film, and a metal-like conductive film is formed on the gate insulating film 230 on the active layer 221. The gate electrode 242 is formed of a material.

Next, an interlayer insulating film 250 is formed on and covers the gate electrode 242, and the interlayer insulating film 250 includes first and second contact holes 250a, which expose portions of the source and drain regions 222 and 223, respectively. 250b). Here, the interlayer insulating layer 250 may be formed of a double layer of the first and second interlayer insulating layers 251 and 252, and may be formed of a silicon oxide film.

Next, a source electrode 262 is formed of a conductive material such as a metal on the interlayer insulating layer 250, and the source electrode 262 is connected to the lower source region 222 through the first contact hole 250a. have.

Subsequently, a passivation layer 270 is formed over the entire surface of the substrate 210 to cover the source electrode 262, and the passivation layer 270 has a third contact hole 271 on the second contact hole 250b. . Although the drain electrode is omitted herein, a drain electrode made of the same material as the source electrode 262 may be further formed between the second contact hole 250b and the third contact hole 271.

Next, a pixel electrode 281 made of a transparent conductive material is formed on the passivation layer 270 through the third contact hole 271, and the pixel electrode 281 emits light. It becomes the anode electrode of a diode.

6, the first capacitor electrode 225 formed of polycrystalline silicon and doped with impurities is formed on the insulating substrate 210 in the portion where the storage capacitor is formed. Here, the first capacitor electrode 225 is formed in a process such as source and drain regions 222 and 223 of FIG. 5.

Subsequently, a gate insulating film 230 is formed on the first capacitor electrode 225 to cover the first capacitor electrode 225, and a second material including the same material as the gate electrode 242 of FIG. 5 is formed on the gate insulating film 230. The capacitor electrode 245 is formed.

Next, the second capacitor electrode 245 is covered with the first interlayer insulating film 251, and the first interlayer insulating film 251 has a contact hole 251a partially exposing the second capacitor electrode 245. Next, a power line extension 291 made of a material such as a metal is formed on the first interlayer insulating layer 251, and the power line extension 291 is connected to the lower second capacitor electrode through the contact hole 251a. (245). Next, a second interlayer insulating layer 252 and a protective layer 270 are sequentially formed on the power line extension 291.

Here, the first capacitor electrode 225 is connected to the gate electrode 242 of FIG. 5, and the second capacitor electrode 225 and the power line extension 291 are connected to the source electrode 262 of FIG. 5. have.

The capacitance of the capacitor is proportional to the area of the electrode and inversely proportional to the distance between the electrodes. In the active matrix organic LED according to the present invention, since the second capacitor electrode 245 and the power line extension 291 are connected, the storage capacitor The thickness of the gate insulating layer 230 between the first capacitor electrode 225 and the second capacitor electrode 245 becomes the thickness. Therefore, since the storage capacitor thickness (gate insulating film thickness) of the present invention is smaller than the thickness of the conventional storage capacitor (sum of the gate insulating film thickness and the interlayer insulating film thickness), since the capacitor capacity is larger than the conventional storage capacitor, the capacitor electrode Reducing the area does not reduce the capacitor's capacity.

The manufacturing process of the active matrix organic LED according to the present invention is illustrated in FIGS. 7A to 7E. Here, only the manufacturing process of the storage capacitor part will be described.

As shown in FIG. 7A, a polycrystalline silicon layer is formed on the insulating substrate 210 to a thickness of about 500 GPa and then patterned to form a first capacitor electrode 225. Herein, the first capacitor electrode 225 is preferably doped with impurities, and the active layer 221 of FIG. 5 and the source and drain regions 222 and 223 of FIG. 5 are also formed. In this case, a buffer layer may be further formed between the substrate 210 and the first capacitor electrode 225 by depositing a material such as a silicon oxide film. When the amorphous silicon layer is crystallized into a polycrystalline silicon layer, the substrate may be heated by heat. Since the alkali ions, for example, potassium ions (K +), sodium ions (Na +), and the like present in the 210 may be generated, the alkali ions serve to prevent degradation of the film quality of the polycrystalline silicon layer.

Subsequently, as illustrated in FIG. 7B, a gate insulating film 230 is formed by depositing a material such as a silicon nitride film or a silicon oxide film on the first capacitor electrode 225 to a thickness of about 1,500 mW, and then forming a metal on the first capacitor electrode 225. A second capacitor electrode 245 is formed by depositing and patterning the same material about 2,000 mW. In this case, the gate electrode 242 of FIG. 5 is also formed, and the second capacitor electrode 245 may be formed of a double layer of molybdenum and an aluminum alloy. Here, the first capacitor electrode 225 is connected to the gate electrode 242 of FIG. 5.

Next, as illustrated in FIG. 7C, a material such as a silicon oxide film is deposited by about 3,000 Å to form a first interlayer insulating film 251, and patterned to form a contact hole 251a exposing the second capacitor electrode 245. Form.

Next, as illustrated in FIG. 7D, a conductive material such as a metal is deposited and patterned at about 2,000 Å to form a power line extension 291 connected to the second capacitor electrode 245 through the contact hole 251a. . Here, the power line extension 291 may be formed as part of a power line (not shown).

Subsequently, as shown in FIG. 7E, a material such as a silicon oxide film is deposited on the power line extension 291 to about 3,000 GPa to form a second interlayer insulating film 252, and a silicon nitride film, a silicon oxide film, or an organic layer is formed thereon. The protective layer 270 is formed of an insulating film.

As described above, in the active matrix organic LED according to the present invention, the second capacitor electrode 245 connected to the power line extension 291 is formed below the power line extension 291 to reduce the thickness of the storage capacitor, thereby storing the storage capacitor. Reducing the area of the capacitor can also prevent a decrease in capacitor capacity.

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, in order to reduce the area of the storage capacitor in order to improve the aperture ratio, an additional electrode connected to the upper electrode is formed below the upper electrode of the storage capacitor to reduce the thickness of the capacitor. The capacity | capacitance can be prevented from falling.

Claims (10)

In the active matrix organic electroluminescent device comprising a plurality of pixels arranged in a matrix form on the substrate, the pixel comprising a light emitting diode and a storage capacitor, a power line connected to the storage capacitor and at least one thin film transistor, A first capacitor electrode formed on the substrate; A first insulating film covering the first capacitor electrode; A second capacitor electrode on the first insulating film; A second insulating layer formed on the second capacitor electrode and having a contact hole exposing the second capacitor electrode; A power line extension formed on the second insulating layer and in contact with the second capacitor electrode through the contact hole and connected to the power line; A third insulating film covering the power line extension Active matrix organic electroluminescent device comprising a. The method of claim 1, The first capacitor electrode is an active matrix organic electroluminescent device made of polycrystalline silicon containing impurities. The method of claim 2, The thin film transistor includes a gate electrode and a source electrode, and the second capacitor electrode is an active matrix organic electroluminescent device made of the same material as the gate electrode. The method of claim 3, wherein And the second insulating film and the third insulating film are positioned between the gate electrode and the source electrode. The method according to any one of claims 1 to 4, The pixel is an active matrix organic electroluminescent device comprising four thin film transistors. The method of claim 5, wherein The pixel is an active matrix organic electroluminescent device comprising first and second switching thin film transistors and first and second driving thin film transistors. In the active matrix organic electroluminescent device comprising a plurality of pixels arranged in a matrix form on the substrate, the pixel comprising a light emitting diode and a storage capacitor, a power line connected to the storage capacitor and at least one thin film transistor, Forming a first capacitor electrode on the substrate; Forming a first insulating film on the first capacitor electrode; Forming a second capacitor electrode on the gate insulating film; Forming and patterning a second insulating layer on the second capacitor electrode to form a contact hole exposing the second capacitor electrode; Forming a power line extension on the second insulating layer and in contact with the second capacitor electrode through the contact hole and connected to the power line; Forming a third insulating film on the power line extension Method for manufacturing an active matrix organic electroluminescent device comprising a. The method of claim 7, wherein The forming of the first capacitor electrode may include forming a polycrystalline silicon layer on the substrate and injecting impurities into the active matrix organic electroluminescent device. The method of claim 8, The thin film transistor includes a gate electrode and a source electrode, wherein the gate electrode is formed in the same process as the step of forming the second capacitor electrode. The method of claim 9, And the source electrode is formed in a process following forming the third insulating film.