KR101200582B1 - Manufacturing method for OTFT using corona discharge - Google Patents

Abstract

The present invention relates to a method of manufacturing an organic semiconductor / polymer composite thin film and a method of manufacturing an organic thin film transistor by applying the method of manufacturing the composite thin film. In the present invention, the organic semiconductor and the polymer are subjected to vertical phase separation using corona discharge, and in this process, desirable crystal growth of the organic semiconductor is achieved, and the surface of the thin film is uniformly grown to improve device performance as a semiconductor layer of the organic thin film transistor. Can be. As a representative example of the organic semiconductor, TIPS-PEN, oligothiophene, or the like may be applied.

Description

 Manufacturing method of organic thin film transistor using corona discharge {Manufacturing method for OTFT using corona discharge}

The present invention relates to a method for manufacturing an organic thin film transistor, and more particularly, an organic semiconductor dissolved in an organic solvent such as TIPS-PEN and oligothiophene used as a semiconductor layer of an organic thin film transistor, and a polymer serving as a binder. In the method for producing a composite thin film containing, it is a technique of a method that can be produced so that the surface of the thin film is uniform, and excellent electrical properties.

The present invention is used as a semiconductor layer of an organic thin film transistor, a technique related to a thin film further comprising a binder polymer, such as an organic semiconductor, in particular, crystalline organic semiconductor, for example, TIPS-PEN, oligothiophene, soluble in an organic solvent to be.

Organic thin film transistors (OTFTs) are in the spotlight as driving devices of next generation display devices. The organic thin film transistor uses an organic film instead of a conventional silicon film as a semiconductor active layer, and the material of the organic film is a low molecular organic thin film transistor such as oligothiophene, penttacene, or polythiophene. It is classified as a polymer organic thin film transistor.

Pentacene in the low-molecular organic semiconductor active layer has a π-conjugated planar structure in its entirety, so that its solubility in organic solvents is remarkably low, and is formed using vacuum deposition. Solubilization is possible by introducing a soluble moiety such as an alkyl group into pentacene, but the transistor performance is lower than that of a low molecular crystalline thin film because it is likely to be a liquid crystalline molecule. In order to compensate for the above drawbacks, many thin film transistors having excellent characteristics have been found in a method of controlling the arrangement of molecules in a thin film by selecting a position and a type of a soluble group introduced into a low molecular semiconductor. For example, in the case of pentacene, TIPS-PEN (triisopropylsilylethynyl pentacene, hereinafter abbreviated as "TIPS-PEN") solubilized by introducing isopropylsilyl group has been reported to increase solubility and field effect mobility. In addition, the oligothiophene is dissolved in an organic solvent can be formed into a film through a solution process. Organic semiconductors soluble in organic solvents such as TIPS-PEN and oligothiophene have mainly crystallinity.

TIPS-PEN and oligothiophene, which are soluble in organic solvents, can be manufactured by thin film production by evaporation of solvent at relatively low temperature after solution process such as spin casting, inkjet printing, drop coating or strip casting. It can be applied as a semiconductor active layer of an organic thin film transistor. However, as the solvent evaporates, at some concentration of the solution, TIPS-PEN crystallizes strongly, forming large crystal domains of varying sizes, with rough surfaces that cannot be used stably in transistors. However, considering that the performance of the organic thin film transistor is largely dependent on the conductive channel formed in the first few molecular layers of the semiconductor in contact with the gate insulator, it is desirable to have a uniform contact interface between the organic thin film semiconductor and the gate insulator.

In order to solve this problem, in the prior art, a method of controlling crystal growth of TIPS-PEN during thin film manufacturing by adjusting a solvent or modifying a substrate surface was used, but satisfactory results were not obtained. In addition, when the TIPS-PEN thin film is exposed to the external environment, the electrical properties of the surrounding environment (humidity, oxygen, etc.) are changed, so a protective layer that can play a protective role is required separately.

In order to solve the problem of deterioration of performance due to uneven growth of the crystal in the solution process, a technique using a polymer binder that can be mixed with a solvent with TIPS-PEN has been proposed and stable over a large area through this method. In addition to producing uniform TIPS-PEN / polymer thin film to show uniform device performance, the use of polymers can reduce TIPS-PEN, thereby reducing manufacturing costs. The polymer blended with TIPS-PEN significantly reduces the direct contact of oxygen and water vapor to the TIPS-PEN semiconductor layer, improving the stability of the device's operating environment.

For example, in a recent study by TD Anthopoulos et al., An organic thin film transistor was manufactured using a composite thin film prepared by spin coating of TIPS-PEN / PαMS as a semiconductor layer. When the TIPS-PEN / PαMS solution is thermally annealed at about 100 ° C. for 15 minutes after being cast on the substrate through the above method, the field effect mobility is 0.1 cm ^{2 in the} bottom gate organic thin film transistor and the top gate organic thin film transistor, respectively. / Vs and 0.5 cm ² / Vs. However, in most studies, TIPS-PEN / polymer composite thin films with thicknesses of several hundred nanometers or less are not used in organic thin film transistors as semiconductor layers showing stable device performance.

In addition, research results have been published in which a mixed solution of the organic semiconductor material P3HT and the polymer PMMA is formed into a film, whereby P3HT and PMMA are phase-separated perpendicularly to the substrate, so that PMMA is a protective layer on the semiconductor P3HT layer. Meanwhile, Korean Patent Publication No. 10-2010-70749 discloses polymers dispersed to interconnect organic semiconductors by reducing solubility of a solution in which organic semiconductors (P3HT, PQT-12, etc.) and insulating polymers (PS, PMMA, etc.) are dissolved. A method of forming a thin film from a semiconductor layer of an organic thin film transistor is disclosed.

As described above, when the binder polymer is mixed with the organic semiconductor material to form a mixed thin film, phase separation occurs vertically between the organic semiconductor material and the insulating polymer material, and the organic semiconductor material is preferably used for the insulating layer during the vertical phase separation. It maintains a path through which crystals can move due to crystal growth, and increases electrical properties such as mobility and flashing ratio, as well as the effect of a protective layer from external environmental factors due to an insulator polymer layer that rises above the organic semiconductor layer. Can also be obtained. Therefore, several research groups are using a mixed solution of an organic semiconductor material and an appropriate binder polymer to conduct vertical phase separation during thinning. However, there are many limitations to the phase separation in the vertical direction to the substrate because the solvent evaporation rate, the interfacial energy of the substrate affects the vertical phase separation. In addition, in the polymer composite solution, in addition to the force in which the phase separation occurs in the vertical direction at the same time, it is difficult to cause the vertical phase separation uniformly in a large area because there is a force that occurs in the horizontal direction.

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel method for producing an organic semiconductor / polymer composite thin film in which a method for thinning a mixed solution of an organic semiconductor and a polymer that can be dissolved in an organic solvent enables control of desirable crystal growth of an organic semiconductor. There is. In particular, the vertical phase separation of the organic semiconductor and the polymer acting as a binder occurs during the film forming, and to provide a technology for forming a uniform surface of the thin film.

In addition, another object of the present invention is to improve the performance of an organic thin film transistor in an organic thin film transistor using an organic semiconductor, preferably by controlling the crystal growth of the organic semiconductor to form a very uniform interface with the insulating layer. To provide a way.

Another object of the present invention is to provide an organic thin film transistor using the organic semiconductor / polymer composite thin film in which the crystal growth is controlled as a semiconductor layer.

The present invention is a moving stage capable of moving at a constant speed and direction; A substrate placed on the moving stage and moving in the same speed and direction as the moving stage; A tip-shaped corona upper electrode which is fixedly installed on the moving stage and does not move, and is a positive electrode or a negative electrode, which causes corona discharge by imputation of voltage; And a corona lower electrode positioned between the moving stage and the substrate and having a plate-shaped corona lower electrode opposite to the tip-shaped corona electrode.

In particular, without the corona lower electrode in the form of a plate, the moving stage is preferably in the form of a plate, corona lower electrode in the form of a plate at the same time.

In addition, the present invention comprises the steps of (I) preparing a substrate; Applying a complex solution of an organic semiconductor and a polymer soluble in an organic solvent on the substrate (II); And a thin film is formed by moving the substrate at a constant speed under a tip-shaped upper electrode where a corona discharge occurs so that the coated organic semiconductor / polymer composite solution is sequentially exposed to corona discharge and the solvent evaporates. It provides a method for producing an organic semiconductor / polymer composite thin film comprising the step (III).

In particular, it is preferable that the organic semiconductor is a crystalline organic semiconductor.

In particular, the organic semiconductor is preferably TIPS-PEN or oligothiophene.

In particular, in order to move the substrate at a constant speed, it is preferable to place the substrate on a moving stage.

In particular, it is preferable that the moving stage is a plate-shaped lower electrode for causing corona discharge.

In particular, the polymer is preferably PS, PMMA or PαMS.

In particular, the organic semiconductor is preferably 1 to 9 parts by weight based on 1 part by weight of the polymer.

In addition, the present invention is a method of manufacturing an organic thin film transistor formed by laminating a gate electrode, an insulating layer, an organic thin film semiconductor layer, a source and a drain electrode formed on a substrate, the organic semiconductor and a polymer that can be dissolved in an organic solvent on the insulating layer After applying the composite solution, a method of manufacturing an organic thin film transistor, characterized in that the organic semiconductor / polymer composite thin film is formed as a semiconductor layer by moving the substrate at a constant speed under a tip-shaped upper electrode where corona discharge occurs. To provide.

In particular, it is preferable that the organic semiconductor is a crystalline organic semiconductor.

In particular, the organic semiconductor is preferably TIPS-PEN or oligothiophene.

In particular, in order to move the substrate at a constant speed, it is preferable to place the substrate on a moving stage.

In particular, the moving stage is preferably a plate-shaped lower electrode for causing corona discharge.

In particular, the polymer is preferably PS, PMMA or PαMS.

In particular, the organic semiconductor is preferably 1 to 9 parts by weight based on 1 part by weight of the polymer.

The present invention also provides an organic thin film transistor prepared by the above method.

The TIPS-PEN composite thin film manufactured by SCDC, which is the method of the present invention, has a uniform surface and forms a vertically separated layer of TIPS-PEN and a polymer, and when used as a semiconductor layer of an organic thin film transistor, conventional spin coating Compared to the organic thin film transistor using the TIPS-PEN thin film manufactured by the semiconductor layer, the device performance is excellent. For example, an organic thin film transistor having a TIPS-PEN / PS (90/10 wt.%) Composite thin film as a semiconductor layer by SCDC has a field effect mobility and a 10 ⁴ flashing ratio of 0.23 cm ² / Vs. Is about 100 times larger than that in the spin-coated blend film.

Figure 1a is a diagram illustrating the SCDC of the present invention, Figure 1b is a photograph of the experimental apparatus actually used to implement the SCDC of the present invention, Figure 1c is a direction of crystal growth according to the scan direction in the SCDC process of the present invention 1D is a photograph of a sample of fabricating a TIPS-PEN / PS composite thin film by SCDC on various substrates.
FIG. 2A is a cross-polarized OM image of an organic thin film transistor using a TIPS-PEN / PS (70/30 wt%) thin film manufactured by SCDC as a semiconductor layer, and FIG. 2B is a transfer characteristic curve of the sample of FIG. 2c is an output characteristic curve of the sample of FIG. 2a.
FIG. 3A is a cross-polarized OM image of a TIPS-PEN / PS (70/30 wt%) composite thin film made by SCDC on a SiO ₂ substrate, FIG. 3B is an AFM image for the FIG. 3A sample, and FIG. 3C is FIG. 3A SEM image of the cut surface of the sample, Figure 3d is a cross-polarized OM image of a thin film prepared by spin coating a TIPS-PEN / PS (70/30% by weight) composite solution as a comparative example, Figure 3e is a 3d sample 3F is an SEM image of the cut surface of the sample of FIG. 3D.
4A is a cross-polarized OM image of a TIPS-PEN / PMMA (70/30 wt.%) Thin film, FIG. 4B is an enlarged image of the OM image of FIG. 4A, FIG. 4C is an SEM image of the sample of FIG. 4A, and FIG. 4D is a TIPS Cross-polarized OM image of the PEN / PαMS (70/30 wt.%) Thin film, FIG. 4E is an enlarged image of the OM image of FIG. 4D, and FIG. 4F is an SEM image of the sample of FIG. 4D.

In the present invention, under the corona discharge, the thinning process of the organic semiconductor / polymer composite solution applied to the substrate is referred to as "Scanning Corona Discharge Coating", hereinafter abbreviated as "SCDC".

The present invention is a technique for causing vertical phase separation using an organic semiconductor material and a binder polymer soluble in an organic solvent, if the organic solvent is soluble in organic solvent, can be prepared using the corona discharge of the present invention without limitation to the organic semiconductor. have. For example, TIPS-PEN, oligothiophene, etc. are typical, and the organic semiconductor soluble in such an organic solvent mainly corresponds to a crystalline organic semiconductor.

In the following description, the contents of the present invention will be described by taking a representative TIPS-PEN among organic semiconductor materials as an example.

The In manufacturing a composite thin film of several hundred nanometers or less from the TIPS-PEN / polymer mixed solution through the method, the upper layer of the composite thin film is vertically separated so that the TIPS-PEN layer is formed as a lower layer of the polymer layer It can be produced to form a microstructure. In particular, the TIPS-PEN layer grows crystals to be uniformly manufactured in the process of vertical phase separation, and thus improves interfacial characteristics with the insulator layer. Therefore, the TIPS-PEN layer is used as a semiconductor layer of an organic thin film transistor, so that electrical and physical element Can be improved.

In the following description of the present invention, "complex solution" used without special reference means a solution in which TIPS-PEN and a polymer are dissolved in a solvent, and "composite thin film" refers to a composite of TIPS-PEN and a polymer according to the method of the present invention. It refers to a vertically separated TIPS-PEN / polymer thin film prepared by applying a solution to a substrate, and then exposed to corona discharge while moving at a constant speed.

In addition, in the following description of the present invention, a bottom gate type organic thin film transistor is described as an embodiment, which is for convenience of description, and the method of the present invention can be applied to a top gate type organic thin film transistor, and therefore, the right of the present invention. The range is not limited to the position of the gate electrode but includes all.

SCDC ( Scanning Corona Discharge Coating ) Way

The present invention is characterized by producing a TIPS-PEN / polymer composite thin film using a corona discharge. In addition, in the present invention, the electrokinetic flow of charged gas molecules generated in the tip-shaped corona electrode sequentially from the end of the TIPS-PEN / polymer composite solution applied to the substrate while moving the substrate at a constant speed under corona discharge collision is caused by electrodynamic flow so that the internal crystals of the TIPS-PEN grow in parallel along the scanning direction.

The TIPS-PEN layer prepared by the method of the present invention is expressed almost in a single crystal structure, and the TIPS-PEN composite solution on the lower electrode is generated at a sharp metal tip, and then the electromotive force of the gas molecules charged toward the lower electrode under a high electric field is obtained. Scanned by a scientific flow. In the experimental apparatus of the present invention, corona discharge occurred when a voltage of at least about 4 kV was transferred between the pointed needle-shaped anode and the plate-shaped cathode. The positively ionized gas molecules reacted with the anode and eventually moved to the lower electrode (anode). Momentum transfer of the ionized gas by corona discharge to uncharged ambient gas molecules results in a so-called electric wind, which is induced by the directional electrodynamic flow of charged gas molecules in the electric wind. PEN / polymer blend films can be made. The polymer solution collided with the charged gas molecules forms a thin film with evaporation of the solvent. Of course, it is natural that a corona discharge can be caused by using a needle-shaped cathode and a plate-shaped anode as necessary.

Figure 1a is a diagram illustrating the SCDC of the present invention, Figure 1b is a photograph of the experimental apparatus actually used to implement the SCDC of the present invention, Figure 1c is a direction of crystal growth according to the scan direction in the SCDC process of the present invention It is a figure explaining and FIG. 1D is a photograph of the sample which produced TIPS-PEN / PS composite thin film by SCDC on various board | substrates.

As shown in Fig. 1A, a moving stage is adopted. The moving stage can move from side to side while maintaining a desired constant speed by using a step motor. Although the moving stage itself may simultaneously serve as a lower electrode for corona discharge, the moving stage may further include a flat electrode that serves as a lower electrode for corona discharge separately from the moving stage. A voltage of 10 kV was applied between the sharp tungsten needle (anode) and the planar bottom electrode (cathode), which produced the corona discharge. SCDC began by dropping the TIPS-PEN / polymer solution onto the substrate above the bottom electrode, with the tungsten needle (anode) initially positioned far from the edge of the solution. Next, corona discharge occurs under high voltage, and the solution-coated substrate moves slowly and is placed close to the corona discharge gas flow by a step motor. When moving to the corona discharge gas flow, the TIPS-PEN / polymer composite solution withdrawal certainly from the edge of the substrate, which is the difference between the flow of charged gas molecules generated by the corona discharge and the polymer solution. It means that interaction is taking place. 1B is a photograph of an SCDC device actually manufactured and used in an experiment. In the experiment of the present invention, all organic thin film transistors produced a composite thin film at a distance from the cathode tip to the sample of 1.5 cm, a voltage of 10 kV, and a moving stage of 0.5 mm / sec.

The initial thin film formed from the edge of the substrate as shown in Figure 1c grows along the moving direction of the moving stage as the solvent evaporates. When corona discharge occurs under high voltage, the solution gradually becomes flat and thin in the area close to the needle in the initial stage. After a few seconds, the film is formed from evaporation of the solvent at the edges and develops at a constant rate as shown in FIG. 1C.

The charged polar properties of directional electron winds are effective for wetting composite films on solid substrates, and are called electro wetting. FIG. 1D shows that a thin, uniform TIPS-PEN / polymer thin film of 50-200 nm thickness can be prepared by the method of the present invention on various substrates of Au, SiO ₂ , Si, Al.

Experimental Example  One : Of organic thin film transistor  Manufacture and property test

In the present invention, a bottom gate top contact organic thin film transistor (bottom gate-top contact OTFT) was manufactured by the method of the present invention, and was prepared by a conventional spin coating method as a comparative example. For fabrication of the organic thin film transistor, a heavily doped p-type silicon wafer having 200 nm thick SiO ₂ as an insulating layer was used as a gate electrode. TIPS-PEN / polymer solution is the same for each mixing ratio by the spin coating (comparative example) or the SCDC method by the SiO ₂ Coated on insulating layer. Spin coating as a comparative example was carried out at 1000 rpm for 60 seconds, and then dried at 100 ° C. for 2 hours. Au source and drain electrodes (thickness 100 nm, width 1 mm, length 200 μm) were thermally deposited through a shadow mask on the TIPS-PEN / polymer film. 18 organic thin film transistors were prepared per thin film of each mixing ratio. The electrical properties of the device were measured using semiconductor systems (E5270B, HP4284A, Agilent Technologies). All measurements were made in a metallic shielded box at room temperature in the atmosphere.

The polymer used in the experiment can be used in a wide variety, but because it can not be tested on all polymers, in the present invention PMMA (poly (methyl methacrylate), Mw = 47,600 g / mol) and PS (polystyrene, Mw = 48,000 g / mol), PαMS (poly (α-methyl styrene), Mw = 48,000 g / mol) was purchased from Polymer Source Inc. and used as it is without further processing. TIPS-PEN / polymer blend solution was used by dissolving in solvent toluene, the solvent for preparing the composite solution of TIPS-PEN and the polymer in the present invention can be used without limitation by conventional methods, the scope of the present invention is It does not limit a solvent. The content ratio of TIPS-PEN and the polymer solution was tested by changing the TIPS-PEN from 1 to 9 parts by weight with respect to 1 part by weight of the polymer. In particular, in the experiment of Table 1, the polymer to TIPS-PEN content was tested at three mixing ratios of 10/90, 30/70, and 50/50. In addition, the content of TIPS-PEN / polymer to the solvent was used for SCDC or spin coating in the range of 0.5 to 2% by weight. The solution was heated at 50 ° C. for 1 hour for complete dissolution.

For 18 samples in total, 18 organic thin film transistors were prepared for each sample, and the averaged results are shown in Table 1 below. In Table 1, "SCDC" means an organic thin film transistor to which a composite thin film manufactured using the corona discharge of the present invention is applied, and "as cast" is a comparative example, after spincasting of the composite solution. An organic thin film transistor to which a composite thin film prepared by annealing at 100 ° C. for 2 hours is applied.

As shown in Table 1, the composite films having three content ratios of 90/10, 70/30 and 50/50 of TIPS-PEN / PS showed very stable device performance. As shown in Table 1, the field effect mobility was the highest when the TIPS-PEN / PS (90/10 wt%) was about 0.23 cm ² / V · s. On the other hand, the subthreshold swing calculated in the linear range was very low, about 0.9 V / dec, in the organic thin film transistor using TIPS-PEN / PS (90/10 wt.%) Composite film.

As shown in Table 1, the organic thin film transistor using the TIPS-PEN / PS (70/30 wt%) composite thin film manufactured by spin coating by conventional method for each composition and polymer is an additional thermal annealing after spin casting. Treatment did not give satisfactory performance. For example, an organic thin film transistor applied with spin-coated TIPS-PEN / PS (70/30 wt%), despite being annealed at 100 ° C. for 2 hours as shown in Table 1, has a value of 0.0006 cm ² / V · s. It showed low field effect mobility and low flashing ratio of 4.7 x 10 ² .

In addition, as shown in Table 1, as the PS content increased, the field effect mobility and the flashing ratio decreased. The sub-threshold swing value increases with increasing PS in the blend film. Sub-threshold swings in TIPS-PEN / PS (70/30 wt%) and TIPS-PEN / PS (50/50 wt%) blend films were 2.52 V / dec and 2.72 V / dec, respectively. SCDC did not show reliable device performance with TIPS-PEN / PS blend films containing more than 50 wt.% PS. This is because when the PS content increases, the TIPS-PEN, which acts as a semiconductor active layer, becomes relatively small, but TIPS-PEN is not connected to the semiconductor channel layer even though it has desirable crystal growth.

Overall, the same content ratio, when the TIPS-PEN / PS composite thin film manufactured by the SCDC of the present invention is applied, both the flashing ratio and the field effect mobility is superior to the TIPS-PEN / PMMA or TIPS-PEN / PαMS composite thin film It was. However, the TIPS-PEN / PMMA and TIPS-PEN / PαMS thin films produced by the method of the present invention still show superior results in flashing ratio and field effect mobility at all composition ratios than those applied by conventional spin coating. Showed the effectiveness of the present invention.

FIG. 2A is a cross-polarized OM image of an organic thin film transistor using a TIPS-PEN / PS (70/30 wt%) thin film manufactured by SCDC as a semiconductor layer, and FIG. 2B is a transfer characteristic curve of the sample of FIG. 2c is an output characteristic curve of the sample of FIG. 2a.

2A to 2C, the present invention will be described in more detail by taking an organic thin film transistor to which a TIPS-PEN / PS (70/30 wt%) composite thin film is applied among the 18 composite thin films of Table 1 as an example. . As shown in FIG. 2A, cross-polarized OM images showed that a thin, uniform TIPS-PEN / PS semiconductor channel was formed with a characteristic crystal structure between the source and drain electrodes. 2B and 2C are representative transfer curves and output curves from a meat thin film transistor having a TIPS-PEN / PS (70/30 wt.%) Semiconductor active layer, respectively, with a flashing ratio of about 10 ⁴ typical. p-type current modulation was shown. It is a surprising result that by the simple electrodynamic casting of TIPS-PEN / polymer composite solution as shown in the present invention, such a good device performance.

Experimental Example  2 : SCDC Microstructure analysis of composite thin films prepared by

In order to understand the excellent performance of the thin film manufactured by the method of the present invention in the organic thin film transistor, the microstructure of the composite thin film of the present invention was investigated. The results are shown in FIGS. 3A-3F, where FIG. 3A is a cross-polarized OM image of a TIPS-PEN / PS (70/30 wt%) composite thin film made by SCDC on a SiO ₂ substrate, and FIG. 3B is FIG. 3A. AFM image of the sample, Figure 3c is a SEM image of the cut surface of the sample of Figure 3a, Figure 3d is a cross-section of the thin film prepared by spin coating a TIPS-PEN / PS (70/30% by weight) composite solution as a comparative example 3E is an AFM image of the sample of FIG. 3D, and FIG. 3F is an SEM image of the cut plane of the sample of FIG. 3D.

Cross-polarized OM images of TIPS-PEN / PS (70/30 wt.%) Made by the SCDC of the present invention on SiO ₂ substrates are crystalline TIPS- along the scanning direction (see arrow) over a large area as shown in FIG. 3A. PEN domains show directional growth.

In contrast, as shown in 3d, the spherulitic texture was typical when spin-cast at the content ratio (TIPS-PEN / PS 70/30 wt%) as shown in FIG. 3A and then annealed at 100 ° C. for 2 hours. Directional scanning of electrodynamic flow by corona discharge caused desirable growth of TIPS-PEN crystals upon solvent evaporation and caused vertical phase separation from PS. This vertical phase separation is the reason why the semiconductor thin film manufactured by the method of the present invention exhibits good device performance when applied to transistors, as the results of other research groups.

More detailed microstructure of the TIPS-PEN / PS composite thin film by SCDC was confirmed by AFM. Ribbon-shaped single crystal TIPS-PEN crystals were grown parallel to the scanning direction as shown in FIG. 3B. The ribbon crystals vary, but on average have a width of about a few microns. The film of the present invention was formed by micro phase separation of TIPS-PEN and PS, but the surface of the film was very flat with RMS roughness of about 5 nm. On the other hand, in the spin-coated composite thin film, amorphous PS is uniformly distributed between TIPS-PENs as shown in FIG. 3E, and shows a TIPS-PEN crystal having a size of about 200 nm during nuclear growth and freezing. Naturally, a thin film having a uniform surface having a flat and flexible TIPS-PEN crystal using the SCDC of the present invention is an organic thin film transistor semiconductor active layer, compared to a thin film in which TIPS-PEN and PS are mixed with each other unevenly by spin coating. As a result, it was found to be very effective.

The cross-sectional view of the TIPS-PEN / PS (70/30 wt%) composite thin film manufactured by SCDC as shown in FIG. 3C demonstrates the effectiveness of the composite thin film produced by the SCDC of the present invention as a semiconductor active layer. The bilayer stacked structure is clearly visible on the SiO ₂ substrate. This means that vertical phase separation occurred in the composite solution with the help of the electric wind of charged gas molecules during corona discharge during solvent evaporation. That is, in solution, a thin PS film was formed on the TIPS-PEN over the SiO ₂ gate insulator. In contrast, the spin-coated TIPS-PEN / PS (70/30 wt%) blend film shows a random phase separation layer in which the TIPS-PEN domains are randomly mixed with the PS domains as shown in FIG. 3F. The bilayer structure obtained by SCDC shows high device performance even for 100 nm thick TIPS-PEN / PS films.

4A is a cross-polarized OM image of TIPS-PEN / PMMA (70/30 wt%) thin film, FIG. 4B is an enlarged image of the OM image of FIG. 4A, FIG. 4C is an SEM image of the sample of FIG. 4A, and FIG. 4D is Cross-polarized OM image of TIPS-PEN / PαMS (70/30 wt.%) Thin film, FIG. 4E is an enlarged image of the OM image of FIG. 4D, and FIG. 4F is an SEM image of the sample of FIG. 4D.

As shown in FIG. 4, even when PMMA or PαMS were used as the polymer, TIPS-PEN was grown in parallel along the scanning direction as in PS, and phase separation was performed vertically with TIPS-PEN and PMMA or PαMS. there was.

Claims (17)

delete delete delete delete delete delete delete delete delete In a method of manufacturing an organic thin film transistor, in which a gate electrode, an insulating layer, an organic thin film semiconductor layer, a source and a drain electrode are formed on a substrate, a composite solution of an organic semiconductor and a polymer, which is soluble in an organic solvent, is coated on the insulating layer. And then moving the substrate at a constant speed under a non-moving corona upper electrode in the form of a tip in which corona discharge occurs to form an organic semiconductor / polymer composite thin film as a semiconductor layer.
11. The method of claim 10,
The organic semiconductor is a method of manufacturing an organic thin film transistor, characterized in that the crystalline organic semiconductor.
11. The method of claim 10,
The organic semiconductor is a method of manufacturing an organic thin film transistor, characterized in that the TIPS-PEN or oligothiophene.
11. The method of claim 10,
The method of manufacturing an organic thin film transistor, characterized in that the substrate is placed on a moving stage (moving stage) in order to move the substrate at a constant speed.
In claim 13,
The moving stage is a method of manufacturing an organic thin film transistor, characterized in that at the same time serves as a lower electrode of the plate (plate) shape having the opposite polarity corresponding to the upper electrode of the tip shape.
11. The method of claim 10,
The polymer is a method of manufacturing an organic thin film transistor, characterized in that the PS, PMMA or PαMS.
11. The method of claim 10,
The organic semiconductor is a manufacturing method of the organic thin film transistor, characterized in that 1 to 9 parts by weight based on 1 part by weight of the polymer.
delete

Images