KR100637252B1 - Organic light emitting display device - Google Patents

Abstract

An organic light emitting display device is provided to obtain a uniform image by preventing a moire phenomenon from being generated by portions which are protruded from activation layers of driving and switching TFTs. An organic light emitting display device includes a substrate, plural pixels, TFTs(M1,M2), and an organic light emitting element. The pixels are arranged on the substrate. The TFTs are formed on the substrate within the respective pixels and include activation layers(102,202), which are made of a polycrystalline semiconductor material. The organic light emitting element is electrically connected to the TFT(Thin Film Transistor) within the respective pixels. The polycrystalline semiconductor has plural protruded portions(13) on a surface thereof. The respective pixels have the same number of the protruded portions within the respective activation layers.

Description

Organic light emitting display device

1 is a photograph of a polysilicon crystal structure produced by the SLS method,

2 is a view schematically showing the crystal structure of FIG.

FIG. 3 is a circuit diagram schematically illustrating a pixel circuit of one unit pixel of an organic light emitting diode display according to an exemplary embodiment of the flat panel display of the present invention; FIG.

4 is a circuit diagram illustrating a more specific example of FIG. 3;

5 is a plan view showing the layout of the pixel circuit of FIG.

6 is a cross-sectional view illustrating a driving TFT, a capacitor, and an organic light emitting device in FIG. 4;

7 is a plan view schematically showing the active layers of the pixels of the present invention;

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting display device and a method of manufacturing the same, and more particularly, to an organic light emitting display device and a method of manufacturing the same, which can prevent moiré phenomenon caused by the crystallization pattern of an active layer.

An active matrix type (AM) organic light emitting display device includes a pixel driving circuit for each pixel, and the pixel driving circuit includes a thin film transistor using silicon. As the silicon constituting the thin film transistor, amorphous silicon or polycrystalline silicon is used.

The amorphous silicon TFT (a-Si TFT) used in the pixel driving circuit has a low electron mobility of 1 cm 2 / Vs or less because the semiconductor active layer constituting the source, drain, and channel is amorphous silicon. Accordingly, in recent years, there is a tendency to replace the amorphous silicon thin film transistor with a polycrystalline silicon TFT (poly-Si TFT). The polycrystalline silicon thin film transistor has a higher electron mobility and superior stability to light irradiation than an amorphous silicon thin film transistor. Accordingly, this polycrystalline silicon thin film transistor is well suited for use as an active layer for driving and / or switching thin film transistors in AM organic light emitting displays.

The polycrystalline silicon as described above may be manufactured by various methods, which may be classified into two types: a method of directly depositing polycrystalline silicon and a method of depositing amorphous silicon and then crystallizing it.

Direct deposition of polycrystalline silicon includes chemical vapor deposition (CVD), photo CVD, hydrogen radical (HR) CVD, electron cyclotron resonance (ECR) CVD, plasma enhanced (CVD) CVD, low pressure (LP) There is a method such as CVD.

Meanwhile, the method of crystallizing amorphous silicon after deposition includes solid phase crystallization (SPC), excimer laser crystallization (ELC), metal induced crystallization (MIC), and metal induced lateral crystallization. (Metal Induced Lateral Crystallization (MILC)) and Sequential Lateral Solidification (SLS).

However, since the solid phase crystallization method has to be maintained for a long time at a high temperature of 600 ° C or more, its practicality is remarkably decreased, and the excimer laser method has an advantage of achieving low temperature crystallization, but has a disadvantage of inferior uniformity by widening the laser beam using an optical system. .

The metal-induced crystallization method has the advantage of lowering the crystallization temperature by depositing a metal thin film on the surface of amorphous silicon and using it as a crystallization catalyst to proceed with crystallization of the silicon film. However, this metal-induced crystallization method also causes the polycrystalline silicon film to be contaminated by metal, resulting in poor characteristics of the thin film transistor element formed from this silicon film, and the crystals formed also have small size and disordered problems.

The continuous lateral solidification method (hereinafter referred to as SLS method) takes advantage of the fact that the grain of silicon grows in the direction perpendicular to the interface at the interface between the liquid and the solid phase. By permeation, a part of the amorphous silicon is melted, and crystallization is achieved by allowing crystal growth to occur from the boundary between the part of the molten silicon and the part of the unmelted silicon to the part of the molten silicon. This SLS method has attracted attention as a method for producing low temperature polycrystalline silicon (Low Temperature Poly-Si).

The polysilicon crystal structure manufactured by the SLS method shows the structure shown in FIGS. 1 and 2.

FIG. 1 is a photograph of a polysilicon crystal structure manufactured by the SLS method, and FIG. 2 is a view schematically showing the crystal structure of FIG. 1. The crystal structure of FIG. 1 is a photograph in the case where an amorphous silicon film formed on a glass substrate is crystallized while moving an energy density of 1 J / cm 2, a frequency of 100 Hz, and a laser beam of 20 mm x 20 mm size at a speed of 15 cm / sec.

As shown in FIG. 2, the crystal structure formed by the SLS method is formed between a plurality of first grain boundaries 11 spaced apart from each other by a predetermined interval and the first grain boundaries 11. The first grain boundary 11 is provided with a second grain boundary 12 extending in a direction substantially perpendicular to the grain boundary 11. As described above, according to the SLS method, amorphous silicon is locally melted by a mask, and crystal grains grow toward the melting center from the boundary between the molten portion and the unmelted portion. The second grain boundary 12 refers to grain boundaries between grains that grow toward the melting center, and the first grain boundary 11 refers to grain boundaries where grains that have grown toward the melting center meet each other at the melting center.

This first grain boundary 11 is shown in the form of protrusions having a constant interval, as shown in FIG. However, in the case where the active layer of the TFT is formed of the polycrystalline silicon film having the first grain boundaries 11 present in the form of protrusions, the protrusions may provide a cause of moiré when viewed from the outside of the display device. . That is, the protrusion of the first grain boundary 11 interferes with various patterns such as the wiring and the electrode of the pixel circuit, and appears as moiré when the display is implemented, which causes unevenness of the image.

The present invention has been made to solve the above problems, and an object thereof is to provide an organic light emitting display device capable of preventing the moiré phenomenon caused by the polycrystalline silicon active layer.

In order to achieve the above object, the present invention provides a substrate comprising a substrate, a plurality of pixels partitioned on the substrate, and an active layer formed on the substrate, located in each of the pixels, and provided with a polycrystalline semiconductor. And a thin film transistor and an organic light emitting element positioned in each pixel and electrically connected to the thin film transistor, wherein the polycrystalline semiconductor of the active layer has a plurality of protrusions on its surface, and the number of protrusions present in each of the active layers. The same provides an organic light emitting display device in each of the pixels.

The present invention also provides a substrate, a plurality of pixels partitioned on the substrate, and an active layer formed on the substrate, located in each of the pixels, and provided with a polycrystalline semiconductor. And a thin film transistor and an organic light emitting element positioned in each pixel and electrically connected to the thin film transistor, wherein the polycrystalline semiconductor of the active layer has a plurality of protrusions on its surface, and the protrusions present in each of the active layers occupy. The sum of the areas provides the same organic light emitting display device in each of the pixels.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 schematically illustrates a pixel circuit PC of one unit pixel of the organic light emitting diode display of the present invention.

As shown in FIG. 3, each pixel includes a Vdd power line Vdd in which a data line Data and a scan line serve as one driving power of an organic light emitting diode (OLED).

The pixel circuit PC of each pixel is electrically connected to the data line Data, the scan line, and the Vdd power line Vdd, and controls the light emission of the OLED.

FIG. 4 illustrates a more specific example of FIG. 3, wherein the pixel circuit PC of each pixel includes two thin film transistors M1 and M2 and one capacitor unit Cst.

Referring to FIG. 4, each pixel of the organic light emitting diode market value according to an exemplary embodiment of the present invention includes a switching TFT M2, at least two thin film transistors of the driving TFT M1, and a capacitor unit Cst. And an organic electroluminescent element (OLED).

The switching TFT M2 is turned on / off by a scan signal applied to the scan line Scan to transfer a data signal applied to the data line Data to the storage capacitor Cst and the driving TFT M1. The switching element is not necessarily limited to the switching TFT M2 as shown in FIG. 4, and may include a switching circuit including a plurality of thin film transistors and capacitors, and a circuit that compensates for the Vth value of the driving TFT M1. Alternatively, a circuit for compensating for the voltage drop of the driving power source Vdd may be further provided.

The driving TFT M1 determines the amount of current flowing into the organic light emitting element OLED according to the data signal transmitted through the switching TFT M2.

The capacitor unit Cst stores a data signal transmitted through the switching TFT M2 for one frame.

In the circuit diagram according to FIG. 4, the driving TFT M1 and the switching TFT M2 are illustrated as PMOS TFTs, but the present invention is not necessarily limited thereto, and at least one of the driving TFT M1 and the switching TFT M2 is provided. Can be formed of an NMOS TFT, of course. In addition, the number of the thin film transistors and capacitors as described above is not necessarily limited thereto, and of course, a larger number of thin film transistors and capacitors may be provided.

Meanwhile, in the present invention, the pixel circuit as described above may be embodied in a layout as shown in FIG. 5 and a cross section as shown in FIG. FIG. 6 shows only the driving TFT M1 and the capacitor Cst in the pixel circuit PC of FIGS. 4 and 5.

As illustrated, the transparent substrate 100 includes a pixel circuit PC and an organic light emitting diode OLED. According to the embodiment according to FIG. 6, a pixel circuit PC is provided on the substrate 100, and a passivation film 108 is formed to cover the pixel circuit PC, and on the passivation film 108. An organic light emitting diode OLED is formed.

The substrate 100 may use a transparent glass material, but is not limited thereto, and may use a transparent plastic material.

A buffer layer 101 made of SiOx (x ≧ 1) or SiNx (x ≧ 1) is further formed on the top surface of the substrate 100.

After the semiconductor active layer 102 of the polycrystalline silicon thin film arranged in a predetermined pattern on the buffer layer 101 is formed, the semiconductor active layer 102 is embedded by the gate insulating layer 103. The semiconductor active layer 102 has a source region 102b and a drain region 102c, and further includes a channel region 102a therebetween. The active layer 102 may be formed by forming an amorphous silicon film on the buffer layer 101 and then crystallizing it to form a polycrystalline silicon film, and then patterning the polycrystalline silicon film. In the active layer 102, the source and drain regions 102b and 102c are doped with impurities in accordance with the type of TFT such as the driving TFT M1, the switching TFT M2, and the like. In the present invention, crystallization of the amorphous silicon film into the polycrystalline silicon film can be performed by the continuous side-solidification (SLS) method, and in this case, the crystal structure can be shown in the form as shown in Figs.

A gate electrode 104 corresponding to the semiconductor active layer 102 and an interlayer insulating layer 105 embedded therein are formed on the top surface of the gate insulating layer 103.

After contact holes are formed in the interlayer insulating layer 105 and the gate insulating layer 103, the source electrode 106 and the drain electrode 107 are respectively formed on the interlayer insulating layer 105 and the source region 102b. And the drain region 102c.

Meanwhile, at the same time as the gate electrode 104 is formed, the lower electrode 111 of the capacitor Cst is formed, and at the same time as the source electrode 106 is formed, the upper electrode 110 of the capacitor Cst is formed. do. The upper electrode 110 of the capacitor Cst may be connected to the source electrode 106.

The passivation film 108 is formed on the formed thin film transistor and the capacitor, and the pixel electrode 112 of the organic light emitting diode OLED is formed on the passivation film 108. The pixel electrode 112 is contacted with the drain electrode 107 of the driving TFT M1 by a via hole formed in the passivation film 108. The passivation film 108 may be formed of an inorganic material and / or an organic material. As shown in FIG. 6, the passivation film 108 may be formed to be curved along the curvature of the lower film, whereas the upper surface is flat regardless of the curvature of the lower film. It may be formed as a planarization film to make.

After the pixel electrode 112 is formed on the passivation film 108, the pixel defining layer 109 is formed of an organic material and / or an inorganic material so as to cover the pixel electrode 112 and the passivation film 108. The electrode 112 is open to expose.

The organic layer 113 and the counter electrode 114 are formed on at least the pixel electrode 112.

The pixel electrode 112 functions as an anode electrode, and the counter electrode 114 functions as a cathode electrode. Of course, the polarities of the pixel electrode 112 and the counter electrode 114 may be reversed. It's okay.

In the bottom emission type shown in FIG. 6, the pixel electrode 112 may be provided as a transparent electrode, and the opposite electrode 114 may be provided as a reflective electrode. In this case, the transparent electrode may be formed using ITO, IZO, In2O3, ZnO, or the like having a high work function, and the reflective electrode, which is the counter electrode 114, may have Ag, Mg, Al, Pt, It may be provided with a metal material such as Pd, Au, Ni, Nd, Ir, Cr, Li, Ca and compounds thereof.

The pixel electrode 112 and the counter electrode 114 are insulated from each other by the organic layer 113, and light is emitted from the organic layer 113 by applying voltages having different polarities to the organic layer 113.

The organic layer 113 may be a low molecular or high molecular organic film. When using a low molecular organic film, a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), an electron injection layer (EIL) : Electron Injection Layer) can be formed by stacking single or complex structure, and usable organic materials are copper phthalocyanine (CuPc), N, N-di (naphthalen-1-yl) -N, N '-Diphenyl-benzidine (N, N'-Di (naphthalene-1-yl) -N, N'-diphenyl-benzidine: NPB), tris-8-hydroxyquinoline aluminum ( Alq3) can be used in various ways. These low molecular weight organic films are formed by the vacuum deposition method. In this case, the hole injection layer, the hole transport layer, the electron transport layer, the electron injection layer and the like can be commonly applied to red, green, and blue pixels as a common layer. Thus, unlike FIG. 6, these common layers may be formed to cover the entire pixels, such as the counter electrode 114.

In the case of the polymer organic film, the structure may include a hole transporting layer (HTL) and a light emitting layer (EML). In this case, PEDOT is used as the hole transporting layer, and polyvinylvinylene (PPV) and polyfluorene are used as the light emitting layer. Polymer organic materials such as (Polyfluorene) are used and can be formed by screen printing or inkjet printing.

The organic layer as described above is not necessarily limited thereto, and various embodiments may be applied.

After the organic light emitting diode OLED is formed, the organic light emitting diode OLED is sealed and shielded from outside air.

Meanwhile, in the present invention, as described above, the active layer 102 is formed by crystallizing an amorphous silicon film into a polycrystalline silicon film by a continuous side-solidification method. Accordingly, each active layer 102 is formed in FIGS. It has the same crystal structure as 2.

In this case, as shown in FIG. 7, the protrusions 13 forming the first grain boundaries included in the active layer 102 of the driving TFT M1 and the active layer 202 of the switching TFT M2 are applied to all pixels. The number is approximately equal. As a result, the crystal structure of the active layers 102 and 202 is uniform in all pixels, and the protrusions 13, which may cause optical moiré, have a uniform pattern, thereby preventing moiré.

The uniformity of the protrusions 13 in each of these pixels may be obtained by making the sum of the areas occupied by the protrusions 13 in each active layer equal in all pixels.

In FIG. 7, the active layer 202 of the switching TFT M2 and the active layer 102 of the driving TFT M1 have the same number, or the same area total projections 13 in all the pixels. The present invention is not limited thereto, and at least the protrusions 13 of the active layer 102 of the driving TFT M1 are the same in all pixels, or the protrusions 13 of the active layer 202 of the switching TFT M2 are the same in all the pixels. It may also achieve its intended purpose.

Although the above embodiments have been described with respect to an organic light emitting display, the present invention can be applied to various kinds of flat panel displays such as a liquid crystal display in addition to the organic light emitting display.

According to the present invention as described above, it is possible to prevent the moiré phenomenon according to the crystal structure of the active layer, thereby preventing the image unevenness.

Although the present invention has been described with reference to one embodiment shown in the accompanying drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Could be. Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

Claims (10)

Board; A plurality of pixels partitioned on the substrate; A thin film transistor formed on the substrate and positioned in each pixel, the thin film transistor having an active layer formed of a polycrystalline semiconductor; And An organic light emitting element positioned in each pixel and electrically connected to the thin film transistor; The polycrystalline semiconductor of the active layer has a plurality of protrusions on its surface, respectively The number of protrusions in each of the active layers is the same in each of the pixels. The method of claim 1, The substrate is a transparent substrate, and the organic light emitting diode display implements an image in the direction of the substrate. The method of claim 1, And the polycrystalline semiconductor is polycrystalline silicon. The method of claim 3, The polycrystalline silicon is formed by crystallizing amorphous silicon by a laser. The method of claim 4, wherein And the crystallization by the laser is continuous side solidification. Board; A plurality of pixels partitioned on the substrate; A thin film transistor formed on the substrate and positioned in each pixel, the thin film transistor having an active layer formed of a polycrystalline semiconductor; And An organic light emitting element positioned in each pixel and electrically connected to the thin film transistor; The polycrystalline semiconductor of the active layer has a plurality of protrusions on its surface, respectively The sum of the areas occupied by the protrusions existing in each of the active layers is the same in each of the pixels. The method of claim 6, The substrate is a transparent substrate, and the organic light emitting diode display implements an image in the direction of the substrate. The method of claim 6, And the polycrystalline semiconductor is polycrystalline silicon. The method of claim 8, The polycrystalline silicon is formed by crystallizing amorphous silicon by a laser. The method of claim 9, And the crystallization by the laser is continuous side solidification.

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