KR20080000988A - Method of organic thin film transistor - Google Patents

Abstract

A method for manufacturing an organic thin film transistor is provided to form a conductive wire using noble metal particles, thereby improving the coating characteristic with an organic layer and simplifying the manufacturing process. A gate electrode is formed on a substrate. A gate insulating layer is formed on the resultant including the gate electrode. An active pattern is formed on the gate insulating layer by using an organic material. Source and drain electrodes are formed on the active pattern by using noble metal particles(190). A passivation layer having a contact hole is formed on the resultant substrate. A pixel electrode is formed on the passivation layer, wherein the pixel electrode is connected to the drain electrode through the contact hole.

Description

Manufacturing method of organic thin film transistor {METHOD OF ORGANIC THIN FILM TRANSISTOR}

1A to 1C are exemplary views sequentially illustrating a process of forming a noble metal conductive film using noble metal nanoparticles according to an embodiment of the present invention.

2 is a scanning electron micrograph of the precious metal conductive film shown in FIG. 1C.

3A to 3E are cross-sectional views sequentially illustrating a method of manufacturing an organic thin film transistor according to an exemplary embodiment of the present invention.

** Description of symbols for the main parts of the drawing **

110 substrate 180 self-assembled monolayer

190 ~ 190 ": Precious Metal Nanoparticles

The present invention relates to a method for manufacturing an organic thin film transistor, and more particularly, to a method for manufacturing an organic thin film transistor in which a source electrode and a drain electrode of an organic thin film transistor are formed using noble metal nanoparticles.

Organic thin film transistors (OTFTs) are of increasing interest because they can be used as core devices in applications such as flexible displays and smart cards that cannot be realized as conventional silicon thin film transistors.

Amorphous silicon thin film transistors, which are active devices used in conventional AMLCDs (Active Matrix Liquid Crystal Display), have a high temperature of about 360 ° C. Due to the nature of the inorganic device has a disadvantage that can be broken.

On the contrary, when the device is manufactured using organic materials, the process can be performed at room temperature, and thus, the flexible and light plastic substrate can be used, and the device can be manufactured by a simple process, which is advantageous in terms of productivity. Therefore, the need for an organic thin film transistor capable of depositing at a temperature near room temperature and ensuring flexibility is increasing.

However, it has been pointed out that the organic thin film transistors have a large number of devices showing poor characteristics of less than 1 cm ² / Vsec in terms of characteristics, and that the stability in air is deteriorated.

In order to solve this problem, studies are being actively conducted to apply pentacene, an organic semiconductor material, to a semiconductor layer of an organic thin film transistor. The reason is that the pentacene-based organic thin film transistor not only shows excellent mobility characteristics comparable to that of an amorphous silicon thin film transistor, but also shows a fairly stable characteristic in air.

In the case of applying pentacene as a semiconductor layer of the organic thin film transistor, precious metal materials such as gold (Au) and silver (Ag) are mainly used as the source electrode and the drain electrode. This is because the work function of gold is 5.1 eV, which is the most similar to 6.02 eV of Pentacene's Highest Occupied Molecular Orbital (HOMO). For reference, the HOMO represents the valence band peak energy of the semiconductor.

That is, since pentacene is a p-type semiconductor, holes move from the electrode to the HOMO level of pentacene and current flows. In this case, the lower the energy barrier between the pentacene and the electrode, the easier the holes move. Therefore, it is preferable to use a material having a high work function similar to pentacene as the source electrode and the drain electrode, whereby gold having the most similar work function to 5.1 eV is used as the preferred material.

However, when gold is used as a material of the source electrode and the drain electrode, the price of gold is high, so productivity is low, and in addition, process control is difficult due to the characteristics of gold.

In addition, in order to form a conductive film using gold, a vacuum deposition apparatus such as an evaporator is generally used. Since the vacuum deposition apparatus requires a high vacuum state of about 10 ^-7 Torr, the deposition time and the equipment price are high. There is a very high disadvantage.

In addition, since the deposition material gold is a very expensive material and is deposited to an unwanted portion in the deposition equipment, it is very inefficient and consumes a high amount of material. It adversely affects the subsequent processes of exposure, etching and stripping.

In addition, the gold conductive film deposited by the vacuum deposition equipment is poor in coating (soluble) with a soluble organic semiconductor and the organic insulating film, there is a problem that the penetration of the solvent (peeling) due to the penetration of the solvent.

An object of the present invention is to provide a method of manufacturing an organic thin film transistor which simplifies a conductive film forming process using noble metal nanoparticles and improves coating characteristics with an organic film.

Other features and objects of the present invention will be described in detail in the configuration and claims of the invention below.

In order to achieve the above object, a method of manufacturing an organic thin film transistor of the present invention comprising the steps of forming a gate electrode on a substrate; Forming a gate insulating film on the substrate; Forming an active pattern of an organic material on the substrate; Forming a source electrode and a drain electrode with noble metal nanoparticles on the active pattern; Forming a protective film having contact holes formed on the substrate; And forming a pixel electrode electrically connected to the drain electrode through the contact hole.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of a method for manufacturing an organic thin film transistor of the present invention in detail.

1A to 1C are exemplary views sequentially illustrating a process of forming a noble metal conductive film according to an embodiment of the present invention, and illustrating a process of forming a noble metal conductive film using noble metal nanoparticles.

As shown in FIG. 1A, a self-assembled monolayer 180 having a predetermined thickness is formed on a substrate 110 such as an array substrate of an organic thin film transistor.

At this time, after the acid-base surface treatment and cleaning and drying process on the substrate 110, and APMDES, APTMS, CPTES, CPDMMS that can chemically bond to the surface of the substrate 110 in the atmosphere (ambient) Self-assembled monolayer 180 is formed using the same molecules.

Subsequently, as shown in FIG. 1B, the colloidal solution 195 in which noble metal nanoparticles, for example, gold nanoparticles 190, is dissolved is formed on a substrate 180 on which the self-assembled monolayer 180 is formed. ) Soak for about 0.1 to 10 hours, for example, 1 hour.

In this case, the gold nanoparticles 190 dissolved in the colloidal solution 195 are attached to the self-assembled monolayer 180 on the surface of the substrate 110, and the substrate 110 to which the gold nanoparticles 190 are attached. The colloidal solution 195 is removed, washed with tertiary distilled water, and then dried with nitrogen gas.

In addition, as shown in FIG. 1C, in order to compensate for the roughness due to the surface curvature of the gold nanoparticles 190, the substrate 110 to which the gold nanoparticles 190 are attached is Au ³⁺ + NH. Soak in ₂ OH solution for about 0.1-100 seconds, for example 5 seconds, take out, wash with tertiary distilled water, and then dry with nitrogen gas. At this time, the gold nanoparticles 190 are grown in a state in which the Au ³ + + NH ₂ OH solution itself acts as a seed (seed) radius so that the surface of the substrate 110 is covered on the substrate 110 The gold conductive film 170 formed of the enlarged gold nanoparticles 190 ′ and 190 ″ is formed.

FIG. 2 is a scanning electron microscope (SEM) photograph of the noble metal conductive film shown in FIG. 1C. As shown in FIG. 2, the radius of the gold nanoparticles 190 ′ grows to cover the substrate surface. It can be seen that the conductive film 170 is formed.

The organic thin film transistor is formed by patterning the conductive film 170 including the gold nanoparticles 190 ′ and 190 ″ grown in this manner into a predetermined shape through photolithography or non-photolithography. An electrode and a drain electrode can be manufactured.

The non-photolithography technique replaces the photolithography technique, for example, microcontact printing (μCP), replica molding (REM), microtransfer molding (μTM), MIMIC (micromolding in capillaries), solvent-assisted micromolding (SAMIM) or ink-jet printing.

These non-photolithography techniques have a high resolution of 30 nm to 1 탆 in such a manner as to transfer a desired pattern onto a substrate by using an elastic rubber stamp or mold for printing. The stamp or mold is composed of an elastomer which is an elastomer such as natural rubber or synthetic rubber. In particular, these techniques have the advantage of easily forming a large area pattern at low cost compared to the conventional photolithography technique.

Thus, the gold conductive film wiring formed using the gold nanoparticles has the following advantages.

First, gold nanoparticles are colloidal solutions that can be manufactured in large quantities using a small amount of gold solid salts.The gold nanoparticles are less expensive than vacuum evaporators such as evaporators. There is an advantage that can be used several times for forming the gold conductive film surface at a concentration of 1 nM.

Secondly, the gold nanoparticles can be manufactured simply by a capping agent, a gold powder, and a hot plate without pretreatment, and can be manufactured in a radius range of about 50 to 1000 μs. There is an advantage that the height of the conductive film can be adjusted.

Third, compared with the gold conductive film manufactured by the evaporator, it has a nano-sized surface roughness, and the coating property of the organic semiconductor and the organic insulator is good through the capping agent on the surface of the nanoparticles.

Fourth, the process can be carried out in a normal atmosphere and room temperature without using a vacuum equipment, the gold nano-particle conductive film formed as described above is characterized by good electrical and optical properties.

3A through 3E are cross-sectional views sequentially illustrating a method of manufacturing an organic thin film transistor according to an exemplary embodiment of the present invention.

As shown in FIG. 3A, the first metal material is formed by depositing a first metal material on the transparent substrate 110, and then patterned to form the gate electrode 121. In this case, the patterning process of the gate electrode 121 is performed through a photolithography process.

In this case, the substrate 110 may be glass or plastic, but the present invention is not limited thereto. The plastic is polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polycarbonate, polyvinyl alcohol, polyacrylate, polyimide, polyimide, polynorbornene (Polynorbornene), polyethersulfone (PES) and the like can be used.

In addition, the first metal material may include an opaque conductive material such as gold, silver, copper and aluminum, or a transparent conductive material such as indium tin oxide (ITO).

Subsequently, as illustrated in FIG. 3B, a gate insulating film 115a is formed by depositing a silicon nitride film SiNx or a silicon oxide film SiOx on the entire surface of the substrate 110 including the gate electrode 121.

The gate insulating film 115a may include ferroelectric insulators such as Al ₂ O ₃ , Ta ₂ O ₅ , La ₂ O ₅ , TiO ₂ and Y ₂ O ₃ , inorganic insulators such as SiO, SiN, AlON, polyimide, Organic insulators such as benzocyclobutene (BCB), polyvinylalcohol, and polyacrylate are formed by conventional methods, but are not limited thereto.

After depositing a low molecular organic material such as pentacene on the gate insulating layer 115a, the active pattern 124 is selectively formed on the gate insulating layer 115a corresponding to the gate electrode 121 by selectively patterning the organic molecules. Form.

At this time, since the electrical property of the pentacene is changed by the photosensitive film, a general photolithography process cannot be used. Accordingly, the active pattern 124 may be formed by using a shadow mask, and the shadow mask has an open area for forming a pattern, and is generally different from a mask used in an exposure process. Has a concept. That is, the mask used in the exposure process is divided into an area that blocks or transmits light, whereas the shadow mask is divided into an open area and a blocked area, so that the material to form the pattern is only through the open area. Deposition can form a pattern having the same shape as the open area.

Next, as illustrated in FIG. 3C, a precious metal conductive film is formed on the active pattern 124 using precious metal nanoparticles, and then the pattern is selectively patterned on the active pattern 124. The electrode 122 and the drain electrode 123 are formed. The noble metal nanoparticles include gold and silver, and the noble metal conductive film is immersed in a noble metal nanoparticle solution in a substrate 110 having a self-assembled monolayer on a surface thereof, and the substrate 110 having the noble metal nanoparticles attached thereon is Au ^3+. It is formed by growing precious metal nanoparticles soaked in + NH ₂ OH solution for a predetermined time so that the surface of the substrate 110 is covered.

In addition, the patterning of the noble metal conductive film may be formed through a photolithography process or a non-photolithography process as described above.

Subsequently, as illustrated in FIG. 3D, an organic insulating film or an inorganic insulating film is deposited on the entire surface of the substrate 110 including the source electrode 122 and the drain electrode 123 to form a protective film 115b, and then the protective film ( A partial region of 115b is removed to form a contact hole 140 exposing a portion of the drain electrode 123.

Next, as illustrated in FIG. 3E, a transparent conductive material such as ITO is deposited on the entire surface of the substrate 110 including the contact hole 140, and then selectively patterned through the contact hole 140. The pixel electrode 118 electrically connected to the drain electrode 123 is formed.

Many details are set forth in the foregoing description but should be construed as illustrative of preferred embodiments rather than to limit the scope of the invention. Therefore, the invention should not be defined by the described embodiments, but should be defined by the claims and their equivalents.

As described above, in the method of manufacturing the organic thin film transistor according to the present invention, the noble metal conductive layer wiring is formed by using the noble metal nanoparticles on the surface of the self-assembled monolayer film, thereby improving coating characteristics with the organic film and simplifying the process. Provide effect.

In addition, the manufacturing method of the organic thin film transistor according to the present invention is less expensive gold material consumption, it can be produced simply at normal room temperature without the use of vacuum deposition equipment.

In addition, the manufacturing method of the organic thin film transistor according to the present invention has the advantage that it is easy to apply not only a general photolithography process but also various printing techniques, which are new technologies for forming fine patterns.

Claims (12)

Forming a gate electrode on the substrate; Forming a gate insulating film on the substrate; Forming an active pattern of an organic material on the substrate; Forming a source electrode and a drain electrode with noble metal nanoparticles on the active pattern; Forming a protective film having contact holes formed on the substrate; And And forming a pixel electrode electrically connected to the drain electrode through the contact hole. The method of claim 1, wherein the gate insulating film is a ferroelectric insulator such as Al ₂ O ₃ , Ta ₂ O ₅ , La ₂ O ₅ , TiO ₂ , dY ₂ O ₃ , inorganic insulators such as SiO, SiN, AlON or polyimide ( A method for manufacturing an organic thin film transistor, comprising an organic insulator such as polyimide, BCB (benzocyclobutene), polyvinylalcohol, polyacrylate, and the like. The method of claim 1, wherein the organic material comprises a low molecular weight organic material such as pentacene. The method of claim 1, wherein the noble metal comprises gold or silver. The method of claim 1, wherein the forming of the source electrode and the drain electrode is performed. Forming a self-assembled monolayer on the surface of the substrate; Dipping the substrate on which the self-assembled monolayer is formed in a noble metal nanoparticle solution; ^Immersing the substrate in an Au ³⁺ + NH ₂ OH solution for a predetermined time to grow a noble metal nanoparticle on the surface of the substrate to form a noble metal conductive film; And And selectively patterning the noble metal conductive film to form a source electrode and a drain electrode. The method of claim 5, further comprising performing an acid-base surface treatment, a cleaning, and a drying process on the substrate on which the self-assembled monolayer is formed. The method of claim 5, wherein the noble metal nanoparticle solution is a colloidal noble metal nanoparticle solution. 6. The method of claim 5, wherein the substrate on which the self-assembled monolayer is formed is immersed in a noble metal nanoparticle solution for about 0.1 to 10 hours. The method of claim 5, wherein the substrate is immersed in an Au ³⁺ + NH ₂ OH solution for about 0.1 to 100 seconds. 6. The method of claim 5, wherein the patterning of the noble metal conductive film is performed through a photolithography process. 6. The method of claim 5, wherein the patterning of the noble metal conductive film is performed through a non-photolithography process. The method of claim 5, further comprising removing the substrate contained in the Au ^{3 +} + NH ₂ OH solution, washing with tertiary distilled water, and drying with nitrogen gas.

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