KR100787453B1 - A thin film transistor, a method for preparing the same and a flat panel display device comprising the same - Google Patents

Abstract

A thin film transistor, a method for preparing the same, and a flat panel display device comprising the same are provided to enhance electrical characteristics by improving a crystal growing state of a crystal in an organic semiconductor of an organic semiconductor layer. A source electrode(12a) and a drain electrode(12b) are isolated from a gate electrode(19). An organic semiconductor layer(17) is isolated from the gate electrode and is electrically connected to the source electrode and the drain electrode. An insulating layer is isolated from the gate electrodes and is electrically connected to the source electrode and the drain electrode. An insulating layer is formed to isolate the gate electrode from the source and drain electrodes or the organic semiconductor layer. An intermediate layer includes a first region(15a) for promoting growth of an organic semiconductor layer crystal of the organic semiconductor layer, and a second region(15b) for improving a contact resistance between the organic semiconductor layer and the source and drain electrodes. A contact angle of the first region of the intermediate layer to the water is larger than a contact angle of the source and drain electrodes to the water. Further, the second region of the intermediate layer covers the source electrode and the drain electrode.

Description

A thin film transistor, a method for preparing the same and a flat panel display device comprising the same}

1 and 2 are cross-sectional views schematically showing the structure of one embodiment of a thin film transistor according to the present invention,

3A to 3C schematically illustrate a process of forming an intermediate layer among thin film transistors according to the present invention.

4 is a schematic cross-sectional view of an organic light emitting display device having an embodiment of a thin film transistor according to the present invention;

5 is a graph showing current-voltage characteristics of an embodiment of a thin film transistor according to the present invention.

<Brief description of the main parts of the drawing>

11, 21: substrate

12a, 12b, 22a, 22b: source and drain electrodes

15, 25: middle layer

15a, 25a: first region

15b, 25b: second area

17, 27: organic semiconductor layer

19, 29: gate electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor, a method for manufacturing the same, and a flat panel display device having the same. More specifically, the present invention relates to a first display device for promoting growth of an organic semiconductor crystal in an organic semiconductor layer between an organic semiconductor layer and a source and drain electrode. A thin film transistor having an intermediate layer including a region and a second region for improving contact resistance between the organic semiconductor layer and the source and drain electrodes, a manufacturing method thereof, and a flat panel display device having the same. The thin film transistor may have low contact resistance between the organic semiconductor layer and the source and drain electrodes, have a good organic semiconductor crystal growth state, and may have excellent electrical characteristics.

Thin Film Transistors (hereinafter referred to as TFTs) used in various flat panel display devices such as liquid crystal display devices, organic light emitting display devices, or inorganic light emitting display devices (hereinafter referred to as TFTs) are driving devices for driving pixels and switching elements for controlling the operation of each pixel. Used as an element.

Such a TFT has a semiconductor layer having a source / drain region and a channel region formed between the source / drain regions, a gate electrode insulated from the semiconductor layer and positioned in a region corresponding to the channel region, and the source / drain region. It has source / drain electrodes that respectively contact the drain regions.

The organic thin film transistor is provided with an organic semiconductor layer made of an organic semiconductor material, which can be formed by a low temperature process and is currently being actively researched due to the advantage of using a plastic substrate. For example, the organic thin film transistor is disclosed in Korean Patent Publication No. 2004-0012212.

However, in the case of the organic thin film transistor, ohmic contact between them is not easy due to the difference in work function between the material forming the source and drain electrodes and the material forming the organic semiconductor layer. Therefore, the contact resistance between the organic semiconductor layer and the source and drain electrodes can be increased, thereby deteriorating the electrical characteristics of the thin film transistor. Meanwhile, in the case of the organic semiconductor layer formed on the source and drain electrodes, an organic semiconductor crystal having a satisfactory grain size may not be formed, which may also be a cause of deterioration of electrical characteristics of the thin film transistor.

The present invention is designed to solve the above problems, the contact resistance between the organic semiconductor layer and the source and drain electrodes is improved, the thin film transistor having an interfacial property that can promote the growth of the organic semiconductor crystals, a method of manufacturing the same and It is an object of the present invention to provide a flat panel display device having the same.

In order to achieve the above object of the present invention, the first aspect of the present invention,

A gate electrode, a source and drain electrode insulated from the gate electrode, an organic semiconductor layer insulated from the gate electrode and electrically connected to the source and drain electrodes, and the gate electrode is a source and drain electrode or an organic semiconductor layer And an intermediate layer including an insulating layer insulated from the organic semiconductor layer and a second region in the organic semiconductor layer for promoting growth of an organic semiconductor crystal and a second region for improving contact resistance between the organic semiconductor layer and the source and drain electrodes. One thin film transistor is provided.

In order to achieve the another object of the present invention, the second aspect of the present invention,

Forming a source and drain electrode over the substrate, and covering the source and drain electrode to improve contact resistance between the organic semiconductor layer and the source and drain electrode and the first region to promote growth of the organic semiconductor crystal; Forming an intermediate layer including a second region, forming an organic semiconductor layer on the intermediate layer, forming an insulating layer to cover the organic semiconductor layer, and forming a gate to correspond to the source and drain electrodes It provides a method for manufacturing a thin film transistor comprising the step of forming an electrode.

In order to achieve another object of the present invention, the third aspect of the present invention,

Forming a gate electrode over the substrate, forming an insulating layer to cover the gate electrode, forming a source and drain electrode over the insulating layer, and covering the source and drain electrode, Forming an intermediate layer including a first region for promoting growth of semiconductor crystals and a second region for improving contact resistance between the organic semiconductor layer and the source and drain electrodes, and forming an organic semiconductor layer on the intermediate layer. It provides a method for manufacturing a thin film transistor comprising the step.

In accordance with still another aspect of the present invention, a fourth aspect of the present invention provides a flat panel display device having a thin film transistor as described above in each pixel and having a pixel electrode connected to a source electrode or a drain electrode of the thin film transistor. to provide.

The thin film transistor according to the present invention not only improves the contact resistance between the source and drain electrodes and the organic semiconductor layer, but also has a good crystal growth state of the organic semiconductor layer, thereby having excellent electrical characteristics.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention in more detail.

1 is a thin film transistor 10 according to an exemplary embodiment of the present invention, wherein a substrate 11, source and drain electrodes 12a and 12b, and a first region for promoting growth of an organic semiconductor crystal among the organic semiconductor layers are illustrated in FIG. An intermediate layer 15, an organic semiconductor layer 17, an insulating layer 18, and a gate electrode including a 15a and a second region 15b for improving contact resistance between the organic semiconductor layer and the source and drain electrodes. 19 is a cross-sectional view of the thin film transistors 10 stacked in this order.

In FIG. 1, a conventional thin film transistor substrate such as a glass substrate, a plastic substrate, or a metal substrate may be used as the substrate 11.

The glass substrate may be made of silicon oxide, silicon nitride, or the like. The plastic substrate may be made of an insulating organic material, for example, polyethersulphone (PES), polyacrylate (PAR, polyacrylate), polyetherimide (PEI, polyetherimide), polyethylene naphthalate (PEN, polyethyelenen) napthalate, polyethylene terephthalate (PET, polyethyeleneterepthalate), polyphenylene sulfide (PPS), polyallylate, polyimide, polycarbonate (PC), cellulose triacetate (TAC), cellulose It may be composed of an organic material selected from the group consisting of cellulose acetate propinonate (CAP), but is not limited thereto. The metal substrate may include one or more selected from the group consisting of carbon, iron, chromium, manganese, nickel, titanium, molybdenum, stainless steel (SUS), Invar alloy, ZInconel alloy, and Kovar alloy, but is not limited thereto. . The metal substrate may be a metal foil. Among these, a plastic substrate or a metal substrate can be used in order to acquire a flexible characteristic.

A buffer layer, a barrier layer, a diffusion barrier layer of impurity elements, or the like may be formed on one or both surfaces of the substrate 11. In particular, when the substrate 11 includes a metal substrate, an insulating layer (not shown for convenience) may be further provided on the substrate.

Source and drain electrodes 12a and 12b are formed on the substrate 11, respectively. As a non-limiting example of the material forming the source and drain electrodes 12a, 12b, in addition to Au, Pd, Pt, Ni, Rh, Ru, Ir, Os, such as Al, Mo, Al: Nd alloy, MoW alloy, etc. Alloys composed of two or more metals can be used, and oxides of metals include ITO, IZO, NiO, Ag ₂ O, In ₂ O ₃ -Ag ₂ O, CuAlO ₂ , SrCu ₂ O _2, and ZnO doped with Zr. Can be used, but is not limited thereto. It goes without saying that two or more of the metals or metal oxides described above can be used in combination.

The organic semiconductor layer 17 is formed thereon to be electrically connected to the source and drain electrodes 12a and 12b. At this time, between the organic semiconductor layer 17 and the source and drain electrodes 12a and 12b, the first region 15a for promoting the growth of organic semiconductor crystals among the organic semiconductor layers, the organic semiconductor layer, the source and An intermediate layer 15 including a second region 15b for improving contact resistance between the drain electrodes is provided.

1, the second region 15b of the intermediate layer 15 may be provided to cover the source and drain electrodes 12a and 12b as illustrated in FIG. 1, but is not limited thereto. It is not.

The intermediate layer 15 may have a thickness of 10 to 100Å. When the thickness of the intermediate layer 15 is less than 10 GPa, organic semiconductor crystals may not be grown to a satisfactory level. When the thickness of the intermediate layer 15 exceeds 100 GPa, the organic semiconductor layer 17 and the source and drain electrodes may not be grown. 12a and 12b may be insulated from each other.

As described above, the first region 15a of the intermediate layer 15 serves to promote growth of organic semiconductor crystals in the organic semiconductor layer 17. An organic semiconductor layer 17 is provided over the intermediate layer 15. When the organic semiconductor crystal size of the organic semiconductor layer 17 is small, the crystalline grain boundary is increased to increase the trap site. Resistance can increase. However, when the organic semiconductor layer 17 is formed on the intermediate layer 15 including the first region 15a as in the present invention, the organic semiconductor crystal can grow to a satisfactory level, thereby improving the electrical characteristics of the thin film transistor. Can be.

The contact angle of water of the first region 15a of the intermediate layer 15 is greater than the contact angle of water of the source and drain electrodes 12a and 12b. As a result, the organic semiconductor crystals on the first region 15a can be grown to a satisfactory level by the principle of the difference in the surface energy of the metal and the organic material.

The contact angle means that the liquid is on the solid surface in the air, and when the air and the liquid are in contact with the solid surface, respectively, the cut line and the solid surface at the contact contact of each phase of the solid, liquid, and air The angle of the side containing a liquid is pointed out of this angle | corner. At this time, it can be considered that the solid surface has absorbed liquid vapor.

The contact angle can be used as a measure of wetting by the liquid on the solid side, where a low contact angle exhibits high wetting, ie hydrophilicity and high surface energy, while a high contact angle shows low wettability, ie hydrophobicity and low surface energy. Indicates.

The contact angle is measured by directly projecting the shape of the small liquid droplets raised on the solid surface onto the screen, and in the measurement of the volume, height of the liquid droplets, the radius of the base circle, and the like. The method, the measurement of the inclination angle when the solid surface is inclined at the vertical position such that the curved portion of the liquid surface in contact with the solid becomes the horizontal plane, the measurement of the attachment tension and the like. Such a definition of a contact angle and a measuring method can be easily recognized by those skilled in the art.

In the present specification, the contact angle of the first region or the source and drain electrodes with respect to water refers to the contact angle between them when the solid surface is the first region or the source and drain electrodes and the liquid is water. The contact angle of the first region 15a and the source and drain electrodes 12a and 12b according to the present invention with respect to water may be measured using, for example, a contact angle method using water. . The contact angle method using water is to evaluate the formation angle of the surface and the water droplet through the CCD while dropping the water in the unit of μl, and can be measured under normal temperature conditions.

The contact angle with respect to the water of the first region 15a of the intermediate layer 15 is greater than the contact angle with respect to the water of the source and drain electrodes 12a and 12b. More specifically, the contact angle of the first region 15a with respect to water may be 10 ° to 15 ° greater than the contact angles of the source and drain electrodes 12a and 12b with respect to water. When the contact angle with respect to water of the first region 15a is less than 10 ° than the contact angle with respect to water of the source and drain electrodes 12a and 12b, a satisfactory degree of organic semiconductor crystal growth effect cannot be obtained. This is because when the contact angle of the first region 15a with respect to water is greater than 15 ° than the contact angles of the source and drain electrodes 12a and 12b, it may be electrically insulated and deteriorated.

More specifically, the first region 15a of the intermediate layer 15 may be formed of one or more selected from the group consisting of polymethyl methacrylate (PMMA) and polystyrene (PS), but is not limited thereto.

On the other hand, the second region 15b of the intermediate layer 15 serves to improve the contact resistance between the organic semiconductor layer 17 and the source and drain electrodes 12a and 12b. The second region 15b of the intermediate layer 15 may include a material forming the first region 15a as described above in addition to the contact resistance-improving material.

The contact resistance-improving material, which is one of the materials forming the second region 15b of the intermediate layer 15, may improve contact resistance between the organic semiconductor layer 17 and the source and drain electrodes 12a and 12b. It may be a known material. For example, the contact resistance-improving material may be a material forming a self assembly monolayer (SAM). More specifically, the contact resistance-improving material is 2-mercapto 5-nitrobenzimidazole (MNB) or 2-mercapto-5-methoxy-benzimidazole (2-mercapto -5-methoxy-benzimidazole: MMB), but is not limited thereto.

According to an embodiment of the thin film transistor according to the present invention, the first region 15a of the intermediate layer 15 that promotes the growth of the organic semiconductor crystal is made of PMMA, and the organic semiconductor layer 17 and the source and drain electrodes The second region 15b for improving contact resistance between the 12a and 12b may be formed of PMMA and MNB, but is not limited thereto.

According to another embodiment of the thin film transistor according to the present invention, the first region 15a of the intermediate layer 15 that promotes the growth of the organic semiconductor crystal is made of PMMA, and the organic semiconductor layer 17 and the source and the drain. The second region 15b for improving contact resistance between the electrodes 12a and 12b may be formed of PMMA and MMB, but is not limited thereto.

For example, when the source and drain electrodes 12a and 12b are formed using Au, the contact angle of the Au source and drain electrodes with respect to water is 60 ° to 80 °, and among the intermediate layers 15 according to the present invention. When the first region 15a is formed using polymethyl methacrylate (PMMA), the contact angle of the first region 15a with respect to water may be 70 ° to 90 °.

The organic semiconductor layer 17 is provided on the intermediate layer 15 including the first region 15a and the second region 15b to be electrically connected to the source and drain electrodes 12a and 12b.

Examples of the organic semiconductor material for forming the organic semiconductor layer 17 include pentacene, tetracene, anthracene, naphthalene, alpha-6-thiophene and alpha-4-ti. Offene, perylene and its derivatives, rubrene and its derivatives, coronene and its derivatives, perylene tetracarboxylic diimide and its derivatives, perylenetetracarb Perylene tetracarboxylic dianhydride and its derivatives, polythiophene and its derivatives, polyparaphenylenevinylene and its derivatives, polyparaphenylene and its derivatives, polyfluorene and its derivatives, polythiophenevinyl Enes and derivatives thereof, polythiophene-heterocyclic aromatic copolymers and derivatives thereof, oligoacenes and derivatives thereof of naphthalene, oligothiophenes and derivatives thereof of alpha-5-thiophene, with or without metals Rossi not and the like and derivatives thereof, Pyro mellitic dianhydride and its derivatives, pyromellitic Pyro tick diimide and derivatives thereof may be used. It is of course also possible to use two or more of these.

Then, the insulating layer 18 is provided to cover the organic semiconductor layer 17. The insulating layer 18 may be made of an inorganic material, such as a metal oxide or metal nitride, or may be made of an organic material, such as an insulating organic polymer, but is not limited thereto.

A gate electrode 19 having a predetermined pattern is provided on the insulating layer 18 so as to correspond to the source and drain electrodes 12a and 12b. The gate electrode 19 may be formed to overlap at least a portion with the source and drain electrodes 12a and 12b, but is not limited thereto. For example, the gate electrode 19 may be formed of a metal or an alloy of a metal such as Au, Ag, Cu, Ni, Pt, Pd, Al, Mo, or Al: Nd, Mo: W alloy, but is not limited thereto. It doesn't happen.

FIG. 2 shows another embodiment of a thin film transistor according to the present invention, which includes an organic semiconductor crystal in a substrate 11, a gate electrode 19, an insulating layer 18, source and drain electrodes 12a and 12b, and an organic semiconductor layer. An intermediate layer 15 and an organic semiconductor layer 17 are sequentially provided, including a first region 15a for promoting growth and a second region 15b for improving contact resistance between the organic semiconductor layer and the source and drain electrodes. Of the thin film transistor.

For a detailed description of each layer constituting the thin film transistor illustrated in FIG. 2, refer to the description of the thin film transistor illustrated in FIG. 1 as described above.

The thin film transistor according to the present invention can be formed in various ways. An embodiment of the method of manufacturing a thin film transistor according to the present invention may include forming a source and a drain electrode on a substrate, and covering the source and drain electrode, and a first region and an organic semiconductor to promote growth of an organic semiconductor crystal. Forming an intermediate layer including a second region to improve contact resistance between the layer and the source and drain electrodes, forming an organic semiconductor layer on the intermediate layer, and covering the organic semiconductor layer. And forming a gate electrode to correspond to the source and drain electrodes. Thus, for example, a thin film transistor as shown in FIG. 1 can be manufactured.

Another embodiment of the method of manufacturing a thin film transistor according to the present invention includes forming a gate electrode on a substrate, forming an insulating layer to cover the gate electrode, and forming a source and a drain electrode on the insulating layer. And an intermediate layer including a first region for promoting growth of an organic semiconductor crystal and a second region for improving contact resistance between the organic semiconductor layer and the source and drain electrodes so as to cover the source and drain electrodes. And forming an organic semiconductor layer on the intermediate layer. Thus, for example, a thin film transistor as shown in FIG. 2 can be manufactured.

Detailed description of each layer in the method of manufacturing the thin film transistor is described above.

The forming of the source and drain electrodes may further include oxidizing the source and drain electrode surfaces when the source and drain electrodes are formed of an oxidizable metal. This is to increase the bonding force with the second region of the intermediate layer to be formed later.

Surface oxidation of the source and drain electrodes can be performed in a variety of ways. For example, a method of annealing the surfaces of the source and drain electrodes under an atmospheric atmosphere, preferably an oxygen atmosphere, a method of treating the surfaces of the source and drain electrodes with a gas, preferably an oxygen plasma, or hydrogen peroxide on the surfaces of the source and drain electrodes Chemical treatment with an oxidizing agent such as water may be used, but is not limited thereto.

The forming of the intermediate layer may be performed by coating and heat treating a first mixture including the organic semiconductor crystal-growth promoting material and then coating and heat treating a second mixture including a material for improving contact resistance. The organic semiconductor crystal-growth promoting materials are materials capable of satisfying the contact angle range as described above, for example, PMMA, PS, and the like, and the contact resistance improving material may be, for example, MNB, MMB, or the like. .

An embodiment of the intermediate layer forming step of the thin film transistor according to the present invention will be described with reference to FIGS. 3A to 3C.

First, as shown in FIG. 3A, a substrate 21 having source and drain electrodes 22a and 22b is prepared.

Then, the first mixture including the organic semiconductor crystal-growth promoting material is coated to cover the source and drain electrodes 22a and 22b, and then heat-treated to thereby form the first mixture layer (as shown in FIG. 3B). 25a '). In this case, the first mixture layer 25a 'includes a first region 25a for promoting the growth of the organic semiconductor crystal and a region 25b' for which the density of the organic semiconductor crystal-growth promoting material is low. As can be seen from the partial enlarged view of the low-density region 25b 'of the organic semiconductor crystal growth promoting material, the organic semiconductor crystal-growth promoting material on the surfaces of the source and drain electrodes 22a and 22b is a source and a drain. The surface of the electrodes 22a and 22b is not well coated, so its density is not dense, and a continuous film cannot be formed. Thus, some or more of the surfaces of the source and drain electrodes 22a and 22b may be exposed.

Then, the second mixture including the contact resistance-improving material is coated on the low-density region 25b 'of the organic semiconductor crystal-growth promoting material of the first mixture layer 25a', and then heat-treated. This completes the intermediate layer 25 including the first region 25a for promoting the growth of the organic semiconductor crystal and the second region 25b for improving the contact resistance. When the second mixture including the organic semiconductor crystal-growth promoting material is coated on the low density region 25b 'of the organic semiconductor crystal-growth promoting material in the first mixture layer 25a', the source and drain electrodes An exposed portion of the surface of 22a, 22b may be coated with an organic semiconductor-crystal growth promoting material as in the partial enlarged view of FIG. 3c. Accordingly, the second region 25b may be formed including both the organic semiconductor crystal-growth promoting material and the contact resistance improving material.

The first mixture including the organic semiconductor crystal-growth promoting material may further include a solvent. The solvent may be a known polar solvent, for example, alcohols such as methanol and ethanol, water, acetic acid and the like, but is not limited thereto.

The concentration of the first mixture may be 0.1wt% to 1wt%. When the concentration of the first mixture is less than 0.1 wt%, organic semiconductor crystals may not grow to a satisfactory level, and when the concentration of the first mixture exceeds 1 wt%, as described above, the organic semiconductor crystal may have a very thin thickness. It may not be possible to form an intermediate layer.

After coating the first mixture, the heat treatment temperature should be a temperature capable of volatilizing the solvent contained in the first mixture, the temperature range is different depending on the solvent used, for example, may be 100 ℃ to 120 ℃ .

The second mixture may include, for example, a known self-assembled monolayer film forming material, for example, MNB and / or MMB, and the heat treatment temperature after coating the second mixture may be selected for forming the selected self-assembled monolayer film. It is easily selectable by those skilled in the art depending on the material.

The thin film transistor having a structure as described above may be provided in a flat panel display such as an LCD or an organic light emitting display.

FIG. 4 illustrates that the TFT is applied to an organic light emitting diode display that is an embodiment of a flat panel display.

FIG. 4 illustrates one subpixel of an organic light emitting display device. Each subpixel includes an organic light emitting device as a self-luminous element, and includes at least one thin film transistor.

The organic light emitting diode display has various pixel patterns according to the color of light emitted by the OLED, and preferably includes red, green, and blue pixels.

As shown in FIG. 4, source and drain electrodes 32a and 32b having a predetermined pattern are formed on the substrate 31 to promote organic semiconductor crystal growth to cover the source and drain electrodes 32a and 32b. An intermediate layer 35 is provided that includes a first region 35a and an improved contact resistance 35b. An organic semiconductor layer 37 is provided on the intermediate layer 35, and an insulating layer 38 is provided to cover the organic semiconductor layer 37. On the other hand, the gate electrode 39 is provided so as to correspond to the source and drain electrodes 32a and 32b. Detailed description of each layer of the thin film transistor 20 is referred to above.

After the gate electrode 39 is formed, the passivation layer 41 is formed to cover the thin film transistor 30. The passivation layer 41 may be formed of a single layer or a plurality of layers, and may be formed of an organic material, an inorganic material, or an organic / inorganic composite.

The organic light emitting layer 46 of the organic light emitting diode 40 is formed on the passivation layer 41 along the pixel definition layer 43.

The organic light emitting diode 40 emits red, green, and blue light according to the flow of current to display predetermined image information. The organic light emitting diode 40 may include any one of the source and drain electrodes 32a and 32b of the thin film transistor 30. A pixel electrode 45 connected to the electrode, a counter electrode 38 provided to cover all the pixels, and an organic light emitting film 46 disposed between the pixel electrodes 45 and the counter electrode 48 to emit light. It is composed. The present invention is not necessarily limited to the above structure, and the structure of various organic light emitting display devices may be applied as it is.

The organic light emitting layer 36 may be a low molecular or high molecular organic film. When a low molecular organic film is used, a hole injection layer (HIL), a hole transport layer (HTL), and an emission layer (EML) are emitted. ), An electron transport layer (ETL), an electron injection layer (EIL), or the like, may be formed by stacking a single or a complex structure, and the usable organic material may be copper phthalocyanine (CuPc). , N, N-di (naphthalen-1-yl) -N, N'-diphenyl-benzidine (N, N'-Di (naphthalene-1-yl) -N, N'-diphenyl-benzidine: NPB), Various applications are possible, including tris-8-hydroxyquinoline aluminum (Alq3). These low molecular weight organic films are formed by the vacuum deposition method.

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.

The pixel electrode 45 functions as an anode electrode, and the counter electrode 48 functions as a cathode electrode. Of course, the polarities of these pixel electrodes 45 and the counter electrode 48 may be reversed. .

In the case of the liquid crystal display, unlike this, a lower alignment layer (not shown) covering the pixel electrode 45 is formed, thereby completing the manufacture of the lower substrate of the liquid crystal display.

As described above, the thin film transistor according to the present invention may be mounted in each subpixel as shown in FIG. 4, or may be mounted in a driver circuit (not shown) in which an image is not implemented.

Hereinafter, the present invention will be described in more detail using examples.

Example

Example  One

A glass substrate having a source and a drain electrode made of Au was prepared. Spin coating a 0.5 wt% PMMA solution on the Au source and drain electrodes (PMMA weight average molecular weight is 750000 g / mol, solvent is methanol, trade name is PMMA, manufacturer is Aldrich) at 2000 rpm, and then 100 Heat treatment at 0.degree. C., followed by dipping in 0.02 wt% MNB solution (solvent is ethanol), followed by heat treatment at 100.degree. C., with a first region for promoting growth of organic semiconductor crystals and a second region for improving contact resistance. The intermediate layer was formed to a thickness of 1 nm. Then, an organic semiconductor layer is formed by depositing pentacene on an intermediate layer to be electrically connected to the Au source and drain electrodes, and then an organic insulating layer is formed to cover the pentacene organic semiconductor layer, and the upper portion of the insulating layer An organic thin film transistor according to the present invention was prepared by forming a gate electrode made of MoW (100 nm thick). This is called sample 1.

Example 2

An organic thin film transistor was manufactured in the same manner as in Example 1, except that the intermediate layer was formed to a thickness of 100 GPa. This is called sample 2.

Comparative example

An organic thin film transistor was manufactured in the same manner as in Example 1, except that an intermediate layer was not formed. This is called sample A.

Evaluation example

Samples 1, 2 and A were evaluated for current-voltage characteristics. An I-V measuring device (trade name is 4156C, manufactured by Agilent) was used to evaluate the current-voltage characteristics. The current-voltage characteristic of Sample 1 is shown in FIG. 5. Referring to FIG. 5, it can be seen that the thin film transistor according to the present invention has excellent electrical characteristics as compared with the conventional thin film transistor.

According to the present invention as described above, not only the contact resistance is lowered between the organic semiconductor layer and the source and drain electrodes, but also the crystal growth state of the organic semiconductor in the organic semiconductor layer is also good, thereby obtaining a thin film transistor having excellent electrical characteristics. Can be. By using the thin film transistor, a flat panel display device having high reliability can be manufactured.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

Claims (18)

A gate electrode; Source and drain electrodes insulated from the gate electrode; An organic semiconductor layer insulated from the gate electrode and electrically connected to the source and drain electrodes; An insulating layer insulating the gate electrode from a source and drain electrode or an organic semiconductor layer; And An intermediate layer including a first region of the organic semiconductor layer for promoting growth of an organic semiconductor crystal and a second region for improving contact resistance between the organic semiconductor layer and the source and drain electrodes; And And a contact angle of water of the first region of the intermediate layer with respect to water of the source and drain electrodes. The method of claim 1, And a second region of the intermediate layer to cover the source and drain electrodes. The method of claim 1, The thickness of the intermediate layer is a thin film transistor, characterized in that 10 to 100Å. delete The method of claim 1, And a contact angle with respect to water in the first region of the intermediate layer is 10 ° to 15 ° greater than the contact angle with respect to water of the source and drain electrodes. The method of claim 1, And a first region of the intermediate layer is formed of at least one selected from the group consisting of polymethyl methacrylate (PMMA) and polystyrene (PS). The method of claim 1, And a second region of the intermediate layer includes a material for forming a contact resistance-improving material and a first region of the intermediate layer. The method of claim 7, wherein And the contact resistance-improving material is a material forming a self assembly monolayer (SAM). The method of claim 1, A second region of the intermediate layer covers the source and drain electrodes, a first region of the intermediate layer is made of polymethyl methacrylate (PMMA), and a second region of the intermediate layer is polymethyl methacrylate (PMMA) and A thin film transistor comprising 2-mercapto 5-nitrobenzimidazole (MNB). The method of claim 1, The second region of the intermediate layer covers the source and drain electrodes, the first region of the intermediate layer is made of polymethyl methacrylate (PMMA), and the second region of the intermediate layer is polymethyl methacrylate (PMMA) and 2-mercapto-5-methoxy-benzimidazole (MMB). The method of claim 1, The source and drain electrodes are Au, Pd, Pt, Ni, Rh, Ru, Ir, Os, Al, Mo, Al: Nd alloy, MoW alloy, ITO, IZO, NiO, Ag ₂ O, In ₂ O ₃ -Ag A thin film transistor comprising at least one selected from the group consisting of ₂ O, CuAlO ₂ , SrCu ₂ O _2, and ZnO doped with Zr. The method of claim 1, The organic semiconductor layer may include pentacene, tetracene, anthracene, naphthalene, alpha-6-thiophene, alpha-4-thiophene, perylene, and derivatives thereof. , Rubrene and its derivatives, coronene and its derivatives, perylene tetracarboxylic diimide and its derivatives, perylene tetracarboxylic dianhydride And derivatives thereof, polythiophene and derivatives thereof, polyparaphenylenevinylene and derivatives thereof, polyparaphenylene and derivatives thereof, polyfluorene and derivatives thereof, polythiophenvinylene and derivatives thereof, polythiophene-hetero Cycloaromatic copolymers and derivatives thereof, oligoacenes and derivatives thereof of naphthalene, oligothiophenes and derivatives thereof of alpha-5-thiophene, phthalocyanine and derivatives thereof, with or without metal, pi Pyromellitic dianhydride and a derivative thereof, and pi pyromellitic diimide ticks and the thin film transistor characterized in that it comprises one or more of the derivatives thereof. Forming a source and a drain electrode over the substrate; A first region for promoting growth of an organic semiconductor crystal and a second region for improving contact resistance between the organic semiconductor layer and the source and drain electrodes so as to cover the source and drain electrodes; Forming an intermediate layer having a contact angle with respect to that of the source and drain electrodes greater than the contact angle with respect to water; Forming an organic semiconductor layer on the intermediate layer; Forming an insulating layer to cover the organic semiconductor layer; And Forming a gate electrode to correspond to the source and drain electrodes; Thin film transistor manufacturing method comprising a. Forming a gate electrode on the substrate; Forming an insulating layer to cover the gate electrode; Forming a source and a drain electrode on the insulating layer; A first region for promoting growth of an organic semiconductor crystal and a second region for improving contact resistance between the organic semiconductor layer and the source and drain electrodes so as to cover the source and drain electrodes; Forming an intermediate layer having a contact angle with respect to that of the source and drain electrodes greater than the contact angle with respect to water; And Forming an organic semiconductor layer on the intermediate layer; Thin film transistor manufacturing method comprising a. The method according to claim 13 or 14, The thickness of the intermediate layer is a thin film transistor manufacturing method, characterized in that 10 to 100Å. The method according to claim 13 or 14, The step of forming the intermediate layer is performed by coating and heat-treating the first mixture including the organic semiconductor crystal-growth promoting material and then coating and heat-treating the second mixture including the contact resistance-improving material. Thin film transistor manufacturing method. The method of claim 16, Thin film transistor manufacturing method characterized in that the concentration of the first mixture is 0.1wt% to 1wt%. A flat panel display device comprising the thin film transistor according to any one of claims 1 to 3 and 5 to 12, and a pixel electrode connected to a source electrode or a drain electrode of the thin film transistor. .

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