KR100977229B1 - Organic Thin Film Transistor And Method For Fabricating The Same, And Liguid Crystal Display Device By The Same - Google Patents

Abstract

The present invention provides an organic TFT comprising a source / drain electrode as a component, which is formed using an easy-to-process and inexpensive conductive material, and has excellent bonding characteristics with an organic semiconductor layer, and a manufacturing method thereof, and a liquid crystal display device using the same. In particular, the organic TFT according to the present invention comprises a gate electrode formed on the lower substrate; A gate insulating film formed on an entire surface of the lower substrate including the gate electrode and formed of an organic insulating material; Source and drain electrodes overlapping both edges of the gate electrode on the gate insulating layer; And an organic semiconductor layer formed on a portion of the gate insulating film including the source electrode and the drain electrode, wherein each of the source electrode and the drain electrode includes copper (Cu), molybdenum (Mo), and chromium on the gate insulating film. A first layer formed of one of (Cr), titanium (Ti), tantalum (Ta), and molybdenum-tungsten (MoW) metal, and a conductive material doped with impurities between the organic semiconductor layer and the first layer. It characterized in that it comprises a second layer formed of.

Organic TFT, off-current improvement, lift prevention

Description

Organic TFT and its manufacturing method, and liquid crystal display device using the same {Organic Thin Film Transistor And Method For Fabricating The Same, And Liguid Crystal Display Device By The Same}

1 is a cross-sectional view of a TFT according to the prior art.

2 is a cross-sectional view of a liquid crystal display device including a TFT according to the prior art.

3 is a cross-sectional view of an organic TFT according to the prior art.

4A to 4C are cross-sectional views of an organic TFT according to a first embodiment of the present invention.

5 is a cross-sectional view of a liquid crystal display device including an organic TFT according to a first embodiment of the present invention.

6A to 6C are cross-sectional views of organic TFTs according to a second embodiment of the present invention.

7 is a cross-sectional view of a liquid crystal display device including an organic TFT according to a second embodiment of the present invention.

* Explanation of symbols on the main parts of the drawings

111: lower substrate 112a: gate electrode

113: gate insulating film 114: p-type organic semiconductor layer

115a: source electrode 115b: drain electrode

121, 521: metal layer 122: transparent conductive layer                 

123: p-type doping layer 522: n + a-Si layer

514 n-type organic semiconductor layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor (TFT), and more particularly, an organic TFT including a source / drain electrode having low cost, easy processing, and excellent contact characteristics, and a method of manufacturing the same; and a liquid crystal display device using the same; Liquid Crystal Display Device).

In general, the thin film transistor is used as a switch element in an image display display, and the most common application field is an active matrix liquid crystal display (AMLCD) which is a display of a laptop computer.

In the case of an active matrix display, the thin film transistor is vertically intersected and formed at the intersection of the gate wiring and the data wiring defining the unit pixel region, and serves to switch current on or off for the unit pixel region. More specifically, in the on state, current flows to charge a capacitor associated with a specific unit pixel region to a desired voltage, and in the off state, until the unit pixel region is addressed next. Keep it charged.

At this time, the voltage level determines the gray level by determining the amount of light transmitted through the liquid crystal corresponding to the unit pixel region.                         

Hereinafter, an organic TFT according to the related art, a method of manufacturing the same, and a liquid crystal display device using the same will be described with reference to the accompanying drawings.

1 is a sectional view of a TFT according to the prior art, and FIG. 2 is a sectional view of a liquid crystal display device including a TFT according to the prior art.

3 is a sectional view of an organic TFT according to the prior art.

First, referring to a TFT formed using amorphous silicon, as shown in FIG. 1, a gate insulating film formed on the entire surface including the gate electrode 12a formed on the lower substrate 11 and the gate electrode 12a ( 13 and the semiconductor layer 14 of amorphous silicon (a-Si: H) formed on the gate insulating layer 13 on the gate electrode 12a and the edges of the semiconductor layer 14, respectively. It consists of the source electrode 15a and the drain electrode 15b.

At this time, an n + a-Si ohmic contact layer (not shown) is further deposited between the semiconductor layer 14 and the source / drain electrodes 15a and 15b to improve contact resistance characteristics.

The manufacturing process of the TFT is as follows.

First, the gate electrode 12a is formed on the lower substrate 11 using photolithography.

The photo etching technique proceeds as follows.

That is, by depositing a low-resistance metal at a high temperature on a transparent glass substrate with excellent heat resistance and applying a photoresist thereon, by placing a photomask on the photoresist and selectively irradiating light to the photomask The same pattern as that of is imprinted on the photoresist.

Next, the photoresist of the lighted portion is removed and patterned using a developer, and the metal of the portion without the photoresist is etched to obtain a desired pattern.

Subsequently, an inorganic material such as silicon nitride (SiNx) or silicon oxide (SiOx) is deposited on the entire surface including the gate electrode 12a at a high temperature to form a gate insulating layer 13.

Subsequently, amorphous silicon (a-Si: H) is deposited on the gate insulating layer 13 at a high temperature and then patterned to form an island-shaped semiconductor layer 14 overlapping the gate electrode 12a. .

Subsequently, a metal is deposited on the entire surface including the semiconductor layer 14 and patterned by photolithography to form a source electrode 15a and a drain electrode 15b overlapping the edges of the semiconductor layer 14 to form a TFT. Complete

In this case, the gate electrode 12a and the source / drain electrodes 15a and 15b are formed using low resistance metal materials such as aluminum (Al), aluminum alloy (AlNd), molybdenum (Mo), and chromium (Cr). do.

Meanwhile, as shown in FIG. 2, the lower substrate 11 of the liquid crystal display device including the TFT includes the gate electrode 12a, the gate insulating layer 13, the semiconductor layer 14, and the source / drain electrode. In addition to forming a thin film transistor (TFT) including the thin film transistors 15a and 15b, the drain electrode 15b is formed through a passivation layer 16 formed on the entire surface including the thin film transistor and a contact hole formed by removing a portion of the passivation layer 16. ) Is further provided with a pixel electrode 17.

In this case, the thin film transistor is formed at the intersection of the gate line formed simultaneously with the gate electrode 12a and the data line formed at the same time as the source / drain electrodes 15a and 15b and perpendicularly cross the gate line.

The lower substrate 11 on which the thin film transistor TFT is formed is opposed to the upper substrate 21 with an affection layer 31 therebetween, and the upper substrate 21 has respective pixel regions for color implementation. A color filter layer 23 of R, G, and B formed therein, a black matrix layer 22 for blocking light leakage at a portion defining the pixel region, and a common electrode 24 facing the pixel electrode are provided.

However, in order to form such a TFT and liquid crystal display device, a process temperature between about 250-400 ° C. is required.

For example, the gate insulating film 13 and the semiconductor layer 14 are typically deposited by a plasma enhanced chemical vapor depostion (PECVD) method, where the deposition temperature exceeds about 250 ° C. In order to withstand such a high temperature process, glass having excellent heat resistance is used as a substrate, which is heavy and brittle, and has a disadvantage in that the process is difficult and the mobility is low.

In order to overcome these problems, studies on flexible substrates to make a display that is light in weight, resistant to shock, and have a large flexibility are being actively conducted, and recently, plastic substrates are being replaced instead of glass substrates.                         

However, since plastic substrates usually have a coefficient of thermal expansion (CTE) that is 10 times that of glass, the process should only be performed at low temperatures of about 150 ° C or less.

For this purpose, it is essential that the wiring layer, the semiconductor layer, and various insulating films be formed of an organic material suitable for a low temperature process. Such a TFT is called an organic TFT.

As shown in FIG. 3, the organic TFT is formed in a bottom gate structure, and includes a gate electrode 52a formed using a metal such as nickel (Ni) on the lower substrate 51, and A gate insulating film 53 such as SiO ₂ covering the gate electrode 52a on the gate electrode 52a, and a source electrode 55a and a drain electrode formed on both edges of the gate electrode 52a, respectively; 55b) and an organic semiconductor layer 54 such as Liquid Crystalline Polyfluorene Block Copolymer (LCPBC), Pentacene, and Polythiophene formed on the source / drain electrodes 55a and 55b.

In this case, the source / drain electrodes 55a and 55b are formed using a metal such as lead (Pd), silver (Au), and the like, whose work function is similar to that of the organic semiconductor 54.

However, the organic TFT according to the related art, a manufacturing method thereof, and a liquid crystal display device using the same have the following problems.

That is, in the organic TFT, an expensive metal such as Au or Pd is mainly used as a source / drain electrode, but the pattern lift phenomenon occurs because the processability is not easy and the adhesion is poor due to poor adhesion. Therefore, there is a need for an electrode that is easy to process and inexpensive.

 In addition, since the source / drain electrodes, which are metals, and the organic semiconductor are directly bonded to each other, the contact resistance increases, resulting in a current crowding phenomenon of low voltage in the output characteristics of the TFT, and blocking the carrier in the TFT-off state. I can't get the problem

In order to solve the above problems, the present invention provides an organic TFT and a method of manufacturing the same, forming a source / drain electrode using a conductive material which is easy and inexpensive, and improves bonding characteristics with an organic semiconductor layer. Its purpose is to provide an applied liquid crystal display device.

The organic TFT according to the present invention for achieving the above object is a gate electrode formed on the lower substrate; A gate insulating film formed on an entire surface of the lower substrate including the gate electrode and formed of an organic insulating material; Source and drain electrodes overlapping both edges of the gate electrode on the gate insulating layer; And an organic semiconductor layer formed on a portion of the gate insulating film including the source electrode and the drain electrode, wherein each of the source electrode and the drain electrode includes copper (Cu), molybdenum (Mo), and chromium on the gate insulating film. A first layer formed of one of (Cr), titanium (Ti), tantalum (Ta), and molybdenum-tungsten (MoW) metal, and a conductive material doped with impurities between the organic semiconductor layer and the first layer. It characterized in that it comprises a second layer formed of.
In addition, the method of manufacturing an organic TFT according to the present invention includes forming a gate electrode on a lower substrate; Forming a gate insulating film on an entire surface including the gate electrode with an organic insulating material; Forming a first layer of any one of copper (Cu), molybdenum (Mo), chromium (Cr), titanium (Ti), tantalum (Ta), and molybdenum-tungsten (MoW) on the gate insulating layer ; Forming a second layer on the first layer of a conductive material doped with impurities; Patterning the first layer and the second layer to form source and drain electrodes overlapping both edges of the gate electrode; And forming an organic semiconductor layer on a portion of the gate insulating film including the source electrode and the drain electrode.
On the other hand, the liquid crystal display device according to the present invention to which the organic TFT is applied includes a gate wiring and a gate electrode formed on the lower substrate; A gate insulating film formed of an organic insulating material on the entire surface including the gate wiring and the gate electrode; A data line perpendicular to the gate line on the gate insulating film; A source electrode extending from the data line on the gate insulating layer and overlapping one edge of the gate electrode; A drain electrode overlapping the other edge of the gate electrode on the gate insulating film; An organic semiconductor layer formed on a portion of the gate insulating layer including the source electrode and the drain electrode; A protective film formed on an entire surface of the gate insulating film including the organic semiconductor layer; A pixel electrode penetrating the protective film and the organic semiconductor layer and contacting the drain electrode; And an upper substrate facing the lower substrate and having a liquid crystal layer interposed therebetween, wherein each of the source electrode and the drain electrode is formed of copper (Cu), molybdenum (Mo), and chromium (Cr) on the gate insulating layer. ), A first layer formed of any one of titanium (Ti), tantalum (Ta), and molybdenum-tungsten (MoW), and a first material formed of a conductive material doped with impurities between the organic semiconductor layer and the first layer. It is characterized by including two layers.
The present invention uses ITO, n + a-Si, Cr, and the like, which are generally used in liquid crystal display devices, instead of expensive metals such as Au and Pd, which are used as conventional source / drain electrodes. The forming process can be facilitated.
That is, the source / drain electrodes are formed in a structure in which a metal such as chromium and a conductive material doped with impurities are stacked to improve adhesion to a gate insulating film formed of an organic insulating material, thereby preventing a pattern from being broken. In addition, the off-current characteristics are improved by improving the contact characteristics of the organic semiconductor layer and the conductive material doped with impurities. In this case, the conductive material doped with impurities may use the doped ITO or n + a-Si.

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Hereinafter, an organic TFT according to the present invention, a method for manufacturing the same, and a liquid crystal display device to which the same is applied will be described with reference to the accompanying drawings and examples.

First embodiment

4A to 4C are cross-sectional views of an organic TFT according to a first embodiment of the present invention, and FIG. 5 is a cross-sectional view of a liquid crystal display device including an organic TFT according to a first embodiment of the present invention.
The organic TFT according to the first embodiment of the present invention is a p-type organic TFT, as shown in FIG. 4C, a gate electrode 112 formed on the lower substrate 111 and a gate covering the gate electrode 112. A source electrode 115a and a drain electrode 115b overlapping both edges of the gate electrode 112 on the insulating layer 113 and the gate insulating layer 113, and the source electrode 115a and the drain electrode 115b. It is composed of a p-type organic semiconductor layer 114 formed on a portion of the gate insulating film 113 including.
Each of the source electrode 115a and the drain electrode 115b may include a first layer 121 formed of a metal such as chromium (Cr), or a second layer formed of a transparent conductive material such as indium tin oxide (ITO). 122) and a third layer 123 formed of a p-type doped conductive material by doping the transparent conductive material provided in the second layer 122 with p-type impurities. In this case, the third layer 123 is implanted with impurity ions such as boron (B) ions or BF ₂ ions into the transparent conductive material provided as the second layer 122 to the p-type doping layer 123. By providing, the contact characteristic with the p-type organic-semiconductor layer 114 improves.

The first layer 121 is formed of any one metal selected from copper (Cu), molybdenum (Mo), chromium (Cr), titanium (Ti), tantalum (Ta), and molybdenum-tungsten (MoW). do. In particular, when the first layer 121 is formed of chromium (Cr), the resistance is lowered and the adhesion to the organic layer is increased, so that the source / drain electrodes 115a and 115b are formed even if the gate insulating layer 113 is formed of an organic material. ) Is not lifted from the gate insulating film 113.

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Looking at the manufacturing process of the organic TFT as follows.

First, as shown in Figure 4a, on the lower substrate 111 made of glass or transparent plastic (Cu), aluminum (Al), aluminum alloy (AlNd: Aluminum Neodymium), molybdenum (Mo), chromium (Cr) ), Metals having low resistivity, such as titanium (Ti), tantalum (Ta), and molybdenum-tungsten (MoW), are deposited by high-temperature sputtering and then patterned by photolithography to form the gate electrode 112.

In this case, the gate electrode 112 may be formed by coating PEDOT (Polyethylene-dioxythiophene), which is a conductive organic polymer, in addition to a metal having low resistivity, or by printing by injecting or printing.

Thereafter, an inorganic insulating material is deposited on the entire surface including the gate electrode 112 or an organic insulating material is applied to form the gate insulating layer 113.

That is, an inorganic insulating material such as silicon oxide (SiOx) or silicon nitride (SiNx) is usually formed by depositing by plasma enhanced chemical vapor deposition (PECVD), or BCB (Benzocyclobutene), acrylic material It is formed by applying an organic insulating material such as polyimide at low temperature. However, it may be desirable to form the gate insulating layer 113 using an organic insulating material rather than an inorganic insulating material for contact characteristics with the organic semiconductor layer 114.
Subsequently, on the upper surface of the gate insulating layer 113, a first metal may be formed of any one of copper (Cu), molybdenum (Mo), chromium (Cr), titanium (Ti), tantalum (Ta), and molybdenum-tungsten (MoW). The layer 121 is formed, and the second layer 122 is formed on the upper surface of the first layer 121 with a transparent conductive material such as ITO. In this case, the first layer 121 and the second layer 122 may be formed by a sputtering technique. In particular, the first layer 121 may be most preferably formed of chromium (Cr) having low resistance and excellent adhesion to organic materials. However, since aluminum (Al) has a problem in that the contact portion is oxidized by oxygen in ITO and the electrical resistance value is increased, it is preferable to use a metal having poor contact characteristics with ITO.
On the other hand, the second layer 122 may be made of ITO, which is easy to inject holes because the ITO is similar in work function to the organic semiconductor. Therefore, when manufacturing a p-type organic TFT, it will be most preferable to use ITO which is easy to inject p-type impurities.
Then, a photoresist (not shown) is applied on the second layer 122, and a photomask having a predetermined pattern formed on the photoresist is covered to light rays, generally UV or x-ray wavelengths. After exposing to light, it is developed and patterned a photoresist.
Subsequently, the patterned photoresist is used as a mask and the exposed second layer 122 is selectively etched using a FeCl ₃ -based or HNO ₃ + HCl-based etching solution, thereby respectively disposing the source electrode 115a and the drain electrode 115b. Patterned to the shape of.
Next, after removing the photoresist, the third layer 123 of the p-type doped conductive material is formed by doping p + ions such as boron (B) ions or BF ₂ ions to the second layer 122. .
Subsequently, as shown in FIG. 4B, the source layer 115a and the drain are wet-etched by wet etching the exposed first layer 121 with a mixed solution of dichromic acid, nitric acid, etc., using the patterned second layer 122 as a mask. The electrode 115b is completed.
On the other hand, the second layer 122 and the first layer 121 may be etched in one batch at a time by the proper use of etchant, in addition to being etched in a separate wet etching process.
Finally, as illustrated in FIG. 4C, an organic material such as pentacene is applied to a portion of the gate insulating layer 113 including the source electrode 115a and the drain electrode 115b to form a p-type organic semiconductor layer. The p-type organic TFT is completed by forming 114.

In this case, when the gate electrode 112, the gate insulating layer 113, the source / drain electrodes 115a and 115b and the organic semiconductor layer 114 of the organic TFT are all formed of an organic material, a low temperature process is possible. The upper substrate 111 may be replaced with a plastic substrate or a film having a flexible property.

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Meanwhile, in the liquid crystal display device including the organic TFT according to the first embodiment, as shown in FIG. 5, the organic insulation such as BCB, acrylic material, and polyimide is formed on the lower substrate 111 on which the organic TFT is formed. A passivation layer 116 formed by depositing a material at a low temperature, and an indium tin oxide (ITO) or indium zinc oxide (IZO), are formed through the passivation layer 116 and the organic semiconductor layer 114 to pass through the drain electrode 115b. The pixel electrode 117 is further provided.
That is, the liquid crystal display device may include the gate insulating layer 113 and the gate insulating layer 113 formed on the entire surface of the lower substrate 111 including the gate wiring (not shown) and the gate wiring (not shown) formed on the lower substrate 111. ) A data line (not shown) formed to vertically cross a gate line (not shown), an organic TFT (TFT), and an organic TFT disposed in a region where the gate line (not shown) and the data line (not shown) intersect. A passivation layer 116 is formed on the entire surface of the gate insulating layer 113 including the TFT and a pixel electrode 117 is formed on the passivation layer 116 to correspond to the pixel region. Here, the organic TFT (TFT) is formed on the gate electrode 112 and the gate insulating film 113 formed on the lower substrate 111 extending from a gate wiring (not shown). A source electrode 115a that extends from one edge of the gate electrode 112 and overlaps with another edge of the gate electrode 112 on the gate insulating layer 113. And an organic semiconductor layer 114 formed on a portion of the gate insulating film 113 including the 115b and the source electrode 115a and the drain electrode 115b. In this case, each of the source electrode 115a and the drain electrode 115b is formed of a first layer 121 formed of a metal, a second layer 122 formed of a conductive material, and a conductive material doped with p-type impurities. It comprises a third layer 123 to be made. The pixel electrode 117 is in contact with the drain electrode 115b through a contact hole penetrating through the passivation layer 116 and the organic semiconductor layer 114.

Also, in the liquid crystal display device according to the first embodiment, the black substrate 142 and the color filter layer 143 are attached to the upper substrate 141 which is bonded to the lower substrate 111 with the liquid crystal layer 131 therebetween. The common electrode 144 is further provided.

Second embodiment

6A to 6C are cross-sectional views of an organic TFT according to a second embodiment of the present invention, and FIG. 7 is a cross-sectional view of a liquid crystal display device including an organic TFT according to a second embodiment of the present invention.

The organic TFT according to the second embodiment of the present invention is an n-type organic TFT, in which the first layer 521 and n + a where the source electrode 515a and the drain electrode 515b are formed of a metal such as chromium (Cr) or the like. And a fourth layer 523 formed of an n-type doped conductive material such as -Si. However, other components are the same as or similar to those of the organic TFT of the first embodiment described above, and therefore the same description is omitted or simplified.
That is, as shown in FIG. 6C, the gate electrode 512a formed on the lower substrate 511, the gate insulating film 513 covering the gate electrode 512a, and the gate electrode on the gate insulating film 513. Part of the gate insulating film 513 including the source electrode 515a, the drain electrode 515b, and silicon, and the like, respectively overlapped at both edges of the 512a, and including the source electrode 515a and the drain electrode 515b. The n-type organic semiconductor layer 514 is formed. At this time, each of the source electrode 515a and the drain electrode 515b is formed of a first layer 521 made of a metal such as chromium, and a fourth layer made of an n-type doped conductive material such as n + a-Si. 523.
At this time, the fourth layer 523 is provided with n + a-Si impurity ion implanted in amorphous silicon by n + ions such as phosphorus (P) ions or arsenic (As) ions, thereby providing an n-type organic semiconductor layer ( The contact characteristics with 514 are improved.

The first layer 521 is formed of any one metal selected from copper (Cu), molybdenum (Mo), chromium (Cr), titanium (Ti), tantalum (Ta), and molybdenum-tungsten (MoW). do. In particular, when the first layer 521 is formed of chromium (Cr), the resistance is lowered and the adhesion to the organic film is increased, so that the source / drain electrodes 515a, even if the gate insulating film 513 is formed of an organic material. There is no fear that 515b will be lifted from the gate insulating film 513.

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Looking at the manufacturing process of the n-type organic TFT is as follows.

First, as shown in FIG. 6A, the gate electrode 512a is formed by depositing a low resistance metal layer on the lower substrate 511 made of glass or transparent plastic or applying a conductive organic polymer material and patterning the same. .

Thereafter, an inorganic insulating material is deposited on the entire surface including the gate electrode 512a or an organic insulating material is coated to form a gate insulating film 513.
Subsequently, on the upper surface of the gate insulating layer 513, a first metal may be formed of any one of copper (Cu), molybdenum (Mo), chromium (Cr), titanium (Ti), tantalum (Ta), and molybdenum-tungsten (MoW). The fourth layer 523 of n + a-Si is formed by forming a layer 521 and selectively depositing SiH ₄ , H ₂ , n-type impurity ion gases (ex, PH ₃ ) on the top surface of the first layer 521. ). In this case, the first layer 521 may be most preferably made of chromium (Cr) having low resistance and excellent adhesion to organic materials.
Thereafter, as shown in FIG. 6B, the fourth layer 523 is patterned in the shape of a source / drain electrode by a photoetching technique using dry etching, and the patterned fourth layer 523 is lowered as a mask. By wet etching and patterning the first layer 521, the source electrode 515a and the drain electrode 515b including the fourth layer 523 of n + a-Si and the first layer 521 of metal are completed. do.

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Finally, as shown in FIG. 6C, an n-type organic semiconductor layer 514 is coated by applying an organic material including silicon to a portion of the gate insulating film 513 including the source electrode 515a and the drain electrode 515b. ), An n-type organic TFT is completed.

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Meanwhile, in the liquid crystal display device including the organic TFT according to the second embodiment, as shown in FIG. 7, a protective film formed by depositing an organic insulating material at a low temperature on the lower substrate 511 on which the organic TFT is formed. 516 and a pixel electrode 517 formed of ITO or IZO and penetrating through the passivation layer 516 and the n-type organic semiconductor layer 514 and contacting the drain electrode 515b.
That is, the liquid crystal display device includes a gate insulating film 513 and a gate insulating film 513 formed on the entire surface of the lower substrate 511 including the gate wiring (not shown) and the gate wiring (not shown) formed on the lower substrate 511. ) A data line (not shown) formed to vertically cross a gate line (not shown), an organic TFT (TFT), and an organic TFT disposed in a region where the gate line (not shown) and the data line (not shown) intersect. A passivation layer 516 is formed on the entire surface of the gate insulating layer 513 including the TFT and a pixel electrode 517 is formed on the passivation layer 516 corresponding to the pixel region. Here, the organic TFT (TFT) is formed on the lower substrate 511 by extending from a gate wiring (not shown) on the gate electrode 512a and the gate insulating film 513. A source electrode 515a which extends from an edge of the gate electrode 512a and overlaps with the other edge of the gate electrode 512a on the gate insulating layer 513. 515b and an organic semiconductor layer 514 formed on a portion of the gate insulating film 513 including the source electrode 515a and the drain electrode 515b. In this case, each of the source electrode 515a and the drain electrode 515b includes a first layer 521 formed of a metal and a fourth layer 523 formed of a conductive material doped with n-type impurities. The pixel electrode 517 is in contact with the drain electrode 515b through a contact hole penetrating through the passivation layer 516 and the organic semiconductor layer 514.

Further, in the liquid crystal display device according to the second embodiment, the black substrate 542 and the color filter layer 543 are attached to the upper substrate 541 which is bonded to the lower substrate 511 with the liquid crystal layer 531 therebetween. The common electrode 544 is further provided.

On the other hand, the present invention described above is not limited to the above-described embodiment and the accompanying drawings, it is possible that various substitutions, modifications and changes within the scope without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill in Esau.

The organic TFT of the present invention as described above, a method of manufacturing the same, and a liquid crystal display device using the same have the following effects.

First, instead of the expensive metals such as Au and Pd, which are used as the source / drain electrodes, the process cost is reduced by forming conductive materials such as ITO, n + a-Si, and Cr, which are generally used in liquid crystal display devices. The process can be performed easily.

Second, the source / drain electrodes are formed of a double layer of chromium layer and n + a-Si layer or a double layer of chromium layer and ITO doped with impurities, thereby improving contact characteristics with the organic layer, thereby preventing the pattern from being lifted. In addition, the off-current characteristics can be improved by improving the contact characteristics by bonding with the organic semiconductor layer.                     

Therefore, in the liquid crystal display device, the reliability of the device is improved.

Claims (22)

A gate electrode formed on the lower substrate; A gate insulating film formed on an entire surface of the lower substrate including the gate electrode and formed of an organic insulating material; Source and drain electrodes overlapping both edges of the gate electrode on the gate insulating layer; And An organic semiconductor layer formed on a portion of the gate insulating film including the source electrode and the drain electrode, Each of the source electrode and the drain electrode may include at least one metal of copper (Cu), molybdenum (Mo), chromium (Cr), titanium (Ti), tantalum (Ta), and molybdenum-tungsten (MoW). And a second layer formed of a conductive material doped with impurities between the organic semiconductor layer and the first layer. The organic TFT according to claim 1, wherein the first layer is formed of chromium (Cr). delete The organic TFT according to claim 1, wherein the second layer is formed of ITO doped with p-type impurities. The organic TFT according to claim 4, wherein the organic semiconductor layer is a p-type organic semiconductor layer. The organic TFT according to claim 1, wherein the second layer is formed of n + a-Si. The organic TFT according to claim 6, wherein the organic semiconductor layer is an n-type organic semiconductor layer. Forming a gate electrode on the lower substrate; Forming a gate insulating film on an entire surface including the gate electrode with an organic insulating material; On the gate insulating film, a first layer is formed of any one of copper (Cu), molybdenum (Mo), chromium (Cr), titanium (Ti), tantalum (Ta), and molybdenum-tungsten (MoW). step; Forming a second layer on the first layer of a conductive material doped with impurities; Patterning the first layer and the second layer to form source and drain electrodes overlapping both edges of the gate electrode; And And forming an organic semiconductor layer on a part of the gate insulating film including the source electrode and the drain electrode. The method of claim 8, Forming the second layer, Depositing ITO on the first layer; And And ion implanting p-type impurities into the ITO. delete The method of claim 8, Forming the second layer comprises depositing n + a-Si. The method of claim 8, wherein the forming of the source electrode and the drain electrode, Patterning the second layer; And And patterning the first layer by using the patterned second layer as a mask. 10. The method of claim 8, wherein the forming of the source electrode and the drain electrode includes simultaneously patterning the first layer and the second layer. The method of claim 8, wherein in the forming of the gate electrode, the gate electrode is copper (Cu), aluminum (Al), aluminum alloy (AlNd), molybdenum (Mo), chromium (Cr), titanium (Ti), Tantalum (Ta), molybdenum-tungsten (MoW) of any one of the metal material or organic material manufacturing method of the organic TFT characterized in that formed. delete A gate wiring and a gate electrode formed on the lower substrate; A gate insulating film formed of an organic insulating material on the entire surface including the gate wiring and the gate electrode; A data line perpendicular to the gate line on the gate insulating film; A source electrode extending from the data line on the gate insulating layer and overlapping one edge of the gate electrode; A drain electrode overlapping the other edge of the gate electrode on the gate insulating film; An organic semiconductor layer formed on a portion of the gate insulating layer including the source electrode and the drain electrode; A protective film formed on an entire surface of the gate insulating film including the organic semiconductor layer; A pixel electrode penetrating the protective film and the organic semiconductor layer and contacting the drain electrode; And And an upper substrate provided with a liquid crystal layer therebetween facing the lower substrate. Each of the source and drain electrodes may be formed of any one of copper (Cu), molybdenum (Mo), chromium (Cr), titanium (Ti), tantalum (Ta), and molybdenum-tungsten (MoW) on the gate insulating layer. And a second layer formed of a conductive material doped with impurities between the organic semiconductor layer and the first layer. 17. The liquid crystal display device according to claim 16, wherein the gate electrode, the gate insulating film, the source / drain electrode, and the semiconductor layer are formed at the intersection of the gate wiring and the data wiring to form an organic TFT. delete 17. The liquid crystal display device according to claim 16, wherein the second layer is ITO doped with p-type impurities. 20. The liquid crystal display device according to claim 19, wherein the organic semiconductor layer is a p-type organic semiconductor layer. 17. The liquid crystal display device according to claim 16, wherein the second layer is n + a-Si. 22. The liquid crystal display device according to claim 21, wherein the organic semiconductor layer is an n-type organic semiconductor layer.

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