WO2011139006A1 - Organic thin-film transistor having improved charge injectability, and method for manufacturing same - Google Patents

Abstract

The present invention relates to an organic thin-film transistor in which a solution of CS2CO3 is applied to only one of the source/drain electrodes on a substrate to thereby improve electron injectability, and to a complementary metal oxide semiconductor (CMOS) digital circuit using same. The organic thin-film transistor comprises: a substrate; a gate electrode disposed on the substrate; a gate dielectric disposed over the substrate that includes the gate electrode; source/drain electrodes disposed separately on portions of the gate dielectric; an electron-injection layer applied to one of the source/drain electrodes; and an organic semiconductor layer disposed on the substrate that includes the electron-injection layer.

Description

Organic thin film transistor with improved charge injection property and manufacturing method thereof

The present invention relates to a method for manufacturing an organic thin film transistor, a bipolar organic thin film transistor, an organic light emitting transistor, and a digital circuit including the same.

Recently, a flexible display has received much attention. People want to have a bigger screen that they can carry anywhere, so they need to develop displays that can be folded, bent or rolled. The roll-to-roll process also enables mass production of these displays at lower prices. However, this requires the use of warp substrates such as plastic or stainless steel, which requires lowering the process temperature to below 300 ° C.

On the other hand, high-resolution and low-power driving requires an active matrix (AM matrix) driving method. Inorganic thin film transistors such as silicon, which are currently used, have a high manufacturing temperature and are easily broken when bent or bent, so there is a limitation in applying them to flexible displays. Therefore, research on organic thin film transistors (OTFTs), which can be easily manufactured at low temperatures and can withstand bending or bending, is being actively conducted.

The organic thin film transistor is not only actively researched as a driving device of the next generation display device, but also can be applied to the production of RFID (Radio Frequency Identification Tag) tags that can be applied to the recognition of individual item units. It is expected. The organic thin film transistor (OTFT) uses an organic semiconductor film instead of a silicon film as a semiconductor layer. The organic thin film transistor (OTFT) is a low molecular organic thin film transistor such as oligothiophene or pentacene, depending on the material of the organic film. It is classified into a polymer organic thin film transistor such as polythiophene series.

When the RFID tag is manufactured using the organic thin film transistor as described above, the RFID tag can be manufactured at a lower manufacturing cost, and thus, it can be applied to all individual consumer goods. However, in order to manufacture the printing and flexible RFID tag, a metal oxide semiconductor (CMOS) type digital circuit consisting of N-type semiconductor and P-type semiconductor must be implemented. For this purpose, high electron and hole injection with one electrode material (mostly gold) is used. Efficiency must be obtained. However, due to the difference in the work function of gold and the energy level (HOMO or LUMO level) of N-type and P-type organic semiconductor materials, the contact resistance generated between the electrode and the organic semiconductor is inevitable. Typically, P-type organic semiconductors and gold electrodes have a low contact resistance, and N-type organic semiconductors and gold electrodes have a high contact resistance. Therefore, the CMOS type organic digital devices (inverters and ring oscillators) manufactured using gold electrodes have a very low performance due to the high contact resistance between the gold electrodes and the N type organic semiconductors.

In order to solve the problem of the high contact resistance of the organic thin film transistor using the N-type organic semiconductor and the gold electrode as described above, the method mainly used until the metal salt is inserted between the gold (Au) electrode and the N-type organic semiconductor between the two It is characterized by effectively lowering the contact resistance. As a representative example, there is a prior art for solving the above problems, which is a patent comprising a mixture consisting of a mixture of an organic material and a metal salt of the same component as the N-type organic semiconductor on the top of the source / drain electrode The present invention relates to a technique for reducing contact resistance by coating. Specific configurations for achieving this include a substrate; A gate electrode located on the substrate; A gate insulating film disposed over the entire surface of the substrate including the gate electrode; Source and drain electrodes spaced apart from each other on a portion of the gate insulating layer; A mixed layer disposed on the source / drain electrode and including an organic material and a metal salt; And an N-type organic semiconductor layer located on the substrate including the mixed layer.

The application of the above technique produces an effect of effectively lowering the contact resistance by inserting a very thin layer of a metal salt intermediate layer of several nanometers. However, since the above technique manufactures a mixture of organic salts and metal salts having the same composition as the N-type organic semiconductors to reduce the contact resistance between the source / drain electrodes and the organic semiconductor by vacuum deposition, the metal salt is selectively applied to only one of the charge injection electrodes. It is very difficult or impossible to do, and all the processes are done in a high vacuum deposition chamber, which makes the work process cumbersome and expensive, which is uneconomical. Therefore, as described above, when the metal salt layer is present at both the source / drain electrodes, and the CMOS digital circuit including both the N-type semiconductor and the P-type semiconductor is implemented, the contact resistance of the N-type transistor can be improved to improve performance. However, the P-type transistor has a fatal disadvantage of causing a decrease in performance by increasing the contact resistance. This is because only one direction change is possible to increase or decrease the work function of the Au electrode depending on the type of metal salt used. For this reason, if one type of metal salt layer is applied to the entire surface of the source / drain electrodes of all the transistors in the electronic circuit, the contact resistance of the N-type transistor can be improved to effectively increase the performance, but the contact resistance of the P-type transistor is increased. It is inevitable to reduce the device performance. On the contrary, when the metal salt suitable for the hole injection is completely coated by vacuum deposition, the hole injection property can be effectively improved, but the electron injection property is deteriorated. In addition, when the metal salt charge transfer layer is formed through the deposition method, the electron and hole injection characteristics are improved simultaneously when the bipolar transistor or the organic light emitting transistor using the same can be transported in one transistor. It is impossible to bet.

In addition, the prior art method requires a relatively high temperature and high pressure process by depositing a metal salt in a high vacuum chamber to improve electron injection, which is not suitable for processing on a plastic substrate for implementing a flexible device.

Therefore, in order for organic thin film transistors to be widely used in various digital circuits, organic light emitting transistors, and organic light emitting lasers, a metal salt layer may be selectively applied to only one electrode among source / drain charge injection electrodes to improve contact resistance of N-type and P-type transistors simultaneously. There is an urgent need for research on the method that can be easily applied through a solution process or a printing process rather than a vacuum or high temperature thermal evaporation.

According to the present invention, ink using an organic salt solution such as CS ₂ CO ₃ selectively on one of the source / drain electrodes is selectively applied to only one electrode through various printing methods, thereby effectively lowering the contact resistance of the N-type organic semiconductor. The main object of the present invention is to provide a method of simultaneously improving the performance of N-type and P-type organic transistors by maintaining the contact resistance of P-type organic semiconductors.

In addition, the present invention is to provide a method for effectively improving the performance of the CMOS digital circuit consisting of N-type and P-type organic transistor through the selective application of the organic salt solution as described above.

Furthermore, in the present invention, the amphipathic organic thin film improves the N-type and P-type charge injection by effectively improving the contact resistance of the N-type and P-type in an ambipolar OTFT using an amphiphilic polymer semiconductor. Another object of the present invention is to provide a method of manufacturing a transistor.

In addition, the present invention provides a method of manufacturing an organic light emitting transistor that can emit light using an amphiphilic organic thin film transistor with improved performance.

The above problems are presented in the present invention

Board;

A gate electrode located on the substrate;

A gate insulating film disposed over the entire surface of the substrate including the gate electrode;

Source / drain electrodes spaced apart from each other in a portion of the gate insulating layer;

An electron and hole injection layer applied to only one of the source / drain electrodes;

It can be solved through an organic thin film transistor comprising a; organic semiconductor layer located on the substrate including the electron and hole injection layer.

By using the organic thin film transistor of the present invention, the contact resistance between the source / drain electrode made of gold and the N-type can be greatly reduced, and the contact resistance between the source / drain electrode and the P-type organic semiconductor having low contact resistance is It can be kept in a low state, thereby providing a high performance amphiphilic organic thin film transistor and organic light emitting transistor having high electron and hole injection characteristics.

In addition, it is possible to effectively reduce the contact resistance of N-type organic thin film transistor by applying ink solution composed of metal salt to only one of the source / drain electrodes through various printing processes, thus simplifying the manufacturing process and reducing the manufacturing cost. The effect is also expected.

1 is a cross-sectional view showing a conventional organic thin film transistor.

2 is a flowchart illustrating a step of manufacturing the organic thin film transistor of the present invention in the form of a bottom gate.

3 is a flowchart illustrating a step of manufacturing the organic thin film transistor of the present invention in the form of a top gate.

4 is a cross-sectional view illustrating an organic thin film transistor having a bottom gate type according to an embodiment of the present invention.

5 is a cross-sectional view illustrating an organic thin film transistor having a top gate type according to another embodiment of the present invention.

FIG. 6 is a diagram illustrating a hole curve according to a gate curve and a transition curve of a P-Channel of an organic thin film transistor of a bipolar top gate type in a state not treated with Cs ₂ CO ₃ .

FIG. 7 is a diagram illustrating a hole curve according to a gate curve and a transition curve of an N-channel of an organic thin film transistor of a bipolar top gate type in a state not treated with Cs ₂ CO ₃ .

FIG. 8 is a diagram illustrating a hole curve according to a gate curve and a transition curve of a P-Channel of an organic thin film transistor of a bipolar top gate type in a state in which Cs ₂ CO ₃ is applied to only one electrode.

FIG. 9 is a diagram illustrating a hole curve according to a gate curve and a transition curve of an N-channel of an organic thin film transistor of a bipolar top gate type in which Cs ₂ CO ₃ is applied to only one electrode.

FIG. 10 is a schematic diagram illustrating a step of selectively applying a metal salt solution to only P-type and N-type one organic transistor electrodes using spray coating.

FIG. 11 is a diagram illustrating a circuit diagram of an organic CMOS inverter fabricated after applying Cs ₂ CO ₃ to only an N-type organic thin film transistor source / drain electrode and a gain value according to an output curve and a gate voltage.

Source / drain electrodes of Au were formed through the printing process of inkjet printing using gold nanoparticles on a silicon substrate. The spacing between the two electrodes was spaced at 50 nm. In order to selectively apply metal salts only to the source electrode, a shadow mask, which has already been patterned, was placed on the substrate on which the source / drain electrodes were formed. Then, the ink prepared by dissolving Cs ₂ CO ₃ in a 2-ethoxyethanol solvent at a concentration of 1 mg / ml was applied using a spray coating machine at a distance of 8 cm from the sample for 10 seconds. Thereafter, the resultant was heated at 100 ° C. for 15 minutes using a hotplate to evaporate the remaining metal salt solvent.

In order to deposit the organic semiconductor, pentacene, a P-type organic semiconductor, was placed in a vacuum chamber, and then sublimed by applying a heat of 200 ° C. at 10 ⁻⁶ torr and then applied to a thickness of 30 to 70 nm. After applying PMMA to the thickness of 200 nm by spin coating, an organic thin film transistor was manufactured by depositing a gate electrode having a thickness of 60 nm using Al only in the channel region of the transistor using a shadow mask.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. Terms used throughout the specification of the present invention are merely illustrated to explain the present invention in more detail, it is obvious that the present invention is not limited thereto.

1 is a cross-sectional view showing a conventional organic thin film transistor. As illustrated, a gate electrode 110 is formed on the substrate 100, and a gate insulating layer 120 is formed over the entire surface of the substrate including the gate electrode 110. Source / drain electrodes 130 are formed on the gate insulating layer 120 to be spaced apart from each other, and the organic semiconductor layer 150 formed on the source / drain electrodes 130 and the gate insulating layer 120 is formed.

The conventional organic thin film transistor having such a structure has a problem that the contact resistance between the source / drain electrodes and the organic semiconductor layer is large. Since the source and drain electrodes serve to inject charge into the organic thin film, it is important to reduce the energy barrier between the electrode and the organic thin film which interferes with this. For example, when pentacene is used as an organic semiconductor, a lot of gold is used as an electrode. The work function of gold is 5.1 eV, and the charge injection is consistent with 5.1 eV, which is the highest Occupied Molecular Orbital (HOMO) value of pentacene. This is because the energy barrier for them is low.

However, unlike the silicon semiconductor layer provided in the conventional silicon thin film transistor, the organic semiconductor layer provided in the organic thin film transistor cannot be doped with high concentration. Accordingly, the contact resistance between the source / drain electrode and the organic semiconductor layer is increased. The problem arises that an ohmic contact cannot be formed.

This problem of contact resistance is more important when an n-type OTFT and a p-type OTFT are used at the same time. As described above, gold is used as the electron or hole injection source / drain electrode of the OTFT, and due to the work function (5.1 eV) of gold, it is possible to simultaneously obtain an ohmic contact that satisfies both N-type and P-type organic semiconductors. There is no number. This includes both N-type and P-type transistors, which are very serious when implementing CMOS type digital circuits, and most organic CMOS type digital circuits induce very high contact resistance in the N type transistors, resulting in N type organic. The transistor performance is very low compared to the P type. In order to solve this problem, in general, silicon materials are doped with N-type and P-type, respectively, to overcome these problems. However, in the case of organic semiconductors, such selective doping is very difficult and many techniques for patterning the same. Not developed.

2 is a flowchart illustrating a step of manufacturing the organic thin film transistor of the present invention in the form of a bottom gate. The bottom gate type organic thin film transistor provides a substrate, forms a gate electrode on the substrate, forms a gate insulating film to cover the gate electrode, and source / drain electrodes spaced apart from each other on a portion of the gate insulating film. After forming a metal salt, the organic semiconductor layer may be formed by selectively applying a metal salt to only one of the source / drain electrodes.

3 is a flowchart illustrating a step of manufacturing the organic thin film transistor of the present invention in the form of a top gate. An organic thin film transistor in the form of a top gate provides a substrate, and forms a source / drain electrode thereon so as to be spaced apart from each other, and then selectively applies a metal salt to only one of the source / drain electrodes and spreads the organic material over the entire surface thereon. After forming the semiconductor layer, a gate insulating film is applied over the entire surface, and finally a gate electrode is formed between the source / drain electrodes of the transistor.

The substrate may be formed of a transparent substrate such as glass, a silicon substrate, or plastic. The plastic substrate material is polyethersulphone (PES), polyacrylate (PAR, polyacrylate), polyetherimide (PET, polyetherimide), polyethylene naphthalate (PEN, polyethyelenen napthalate), polyethylene terephthalate (PET, polyethyeleneterepthalate (PPS) polyphenylene sulfide (PPS), polyallylate (polyallylate), polyimide (polyimide), polycarbonate (PC), cellulose tri acetate (TAC), cellulose acetate propinoate Use any one selected from). Preferably, a transparent substrate such as glass capable of UV transmission is used.

The gate electrode is made of gold (Au), nickel (Ni), copper (Cu), silver (Ag), aluminum (Al), aluminum alloy (Al-alloy), molybdenum (Mo), and molybdenum alloy (Mo-alloy). It may be formed of any one selected from, it is more preferable to form a molybdenum-tungsten (MoW) alloy. In addition, the gate electrode may be formed through various printing processes. In general, the gate electrode may be manufactured using a printing process such as inkjet printing using a metal nanoparticle solution or a PEDOT: PSS conductive polymer as an ink. Through the printing process, the gate electrode can be formed and the vacuum process can be excluded, thereby reducing the manufacturing cost.

A gate insulating film is formed over the entire surface of the substrate including the gate electrode.

The gate insulating film is composed of a single film or a multilayer film of an organic insulating film or an inorganic insulating film, or an organic-inorganic hybrid film. As the inorganic insulating film, any one or more selected from silicon oxide film, silicon nitride film, Al2O3, Ta2O5, BST, and PZT is used. The organic insulating film may include polymethacrylate (PMMA, polymethylmethacrylate), polystyrene (PS, polystyrene), phenolic polymer, acrylic polymer, imide polymer such as polyimide, arylether polymer, amide polymer, fluorine polymer, p -Use any one or more selected from xyrene-based polymer, vinyl alcohol-based polymer, parylene (parylene).

Source / drain electrodes are formed on the gate insulating layer to be spaced apart from each other. The source / drain electrode may be formed of a single layer selected from Au, Al, Ag, Mg, Ca, Yb, Cs-ITO, or an alloy thereof, and may improve adhesion to the gate insulating layer and prevent undercut phenomenon. In order to further include an adhesive metal layer such as Ti, Cr or Al may be formed in a multi-layer.

One of the electrodes on the source / drain electrodes includes Cs ₂ CO ₃ , CsF, Rb ₂ CO ₃ , K ₂ CO ₃ , Na to reduce contact resistance between the organic semiconductor layer and the source / drain electrodes and improve electron injection properties. _An ink solution for forming a metal salt electron injection layer selected from metal salts such as ₂ CO ₃ , LiF, CaF ₂ , MgF ₂ , NaCl, MgO, or a mixture thereof is prepared. In addition, to improve the hole injection characteristics, an ink solution for forming a metal salt hole injection layer selected from metal salts or organic substances such as V ₂ O ₅ , MoO ₃ , F ₄ TCNQ, or a mixture thereof is prepared. Since the ink concentration plays a very important role in controlling the thickness of the metal salt layer of the metal salt, it is necessary to use a metal concentration ink of a constant concentration to obtain the effect of improving the electron or hole injection property. The concentration of the ink used may vary slightly depending on the printing method used. However, if the metal salt layer having a thickness of 0.1-2 nm is applied using a concentration of 0.1 mg / ml-10 mg / ml, the expected effect can be obtained. Can be.

The metal salt electron injection layer or hole injection layer is achieved by applying the above-described metal salt ink solution using ink jet printing, screen printing, spray coating, gravure printing, gravure offset printing, reverse gravure offset printing, nozzle printing, pad printing method. .

The metal salt electron and hole injection layer has a thickness of less than 2 nm, preferably 0.1 to 2 nm. When the thickness of the metal salt solution layer is formed to be 0.1 nm or more, the electron or hole injection efficiency may be improved. When the metal salt solution layer is formed to be more than 2 nm, the electron and hole injection effects may be reduced. do.

In addition, when the metal salt charge injection layer is to be applied to a CMOS electronic circuit or a bipolar organic thin film transistor, it is preferable to apply the metal salt charge injection layer to only one of a source or a drain electrode. As described above, when implementing a CMOS digital circuit including both an N-type semiconductor and a P-type semiconductor, the contact resistance of the N-type transistor is reduced and the contact resistance of the P-type transistor is maintained as it is.

An organic semiconductor layer is formed over the entire surface of the substrate including the metal salt solution layer. The organic semiconductor layer may be an N-type organic semiconductor or a P-type organic semiconductor. The N-type organic semiconductor is an acene-based material, a fully fluorinated acene-based material, a partially fluorinated acene-based material, a partially fluorinated oligothiophene-based material, a fullerene-based material, a fullerene-based material having a substituent, Fully fluorinated phthalocyanine materials, partially fluorinated phthalocyanine materials, perylene tetracarboxylic diimide materials, perylene tetracarboxylic dianhydride materials, naphthalene It is preferable to include either tetracarboxylic diimide (naphthalene tetracarboxylic diimide) material or naphthalene tetracarboxylic dianhydride (material). Here, the acene-based material may be selected from anthracene, tetracene, pentacene, perylene or conorene.

In addition, the P-type organic semiconductor is acene (acene), poly-thienylenevinylene (poly-thienylenevinylene), poly-3-hexylthiophene (poly-3-hexylthiophen), alpha-hexathienylene (α-hexathienylene), Naphthalene, alpha-6-thiophene, alpha-4-thiophene, alpha-4-thiophene, rubrene, polythiophene, polyparaphenylene Polyparaphenylenevinylene, polyparaphenylene, polyfluorene, polythiophenevinylene, polythiophene-heterocyclicaromatic copolymer, triarylamine ( triarylamine) or a derivative thereof, wherein the acene group is any one of pentacene, perylene, tetratracene or anthracene.

This completes the organic thin film transistor according to an embodiment of the present invention.

4 is a cross-sectional view illustrating an organic thin film transistor having a bottom gate type according to an embodiment of the present invention.

5 is a cross-sectional view illustrating an organic thin film transistor having a top gate type according to another embodiment of the present invention.

FIG. 6 is a diagram showing a hole curve according to a gate curve and a transition curve of a P-Channel of an organic thin film transistor of a bipolar top gate type in a state not treated with Cs 2 CO 3. The organic polymer semiconductor used is ActivInk P2100 material purchased from Polyera, USA. It is a conjugated polymer based on thiophene and is a material with high hole mobility. 6 shows that P2100 is coated on a glass substrate on which Au source / drain electrodes are pre-patterned by spin coating, and then PMMA insulator is applied by spin coating, and an Al electrode is formed as a gate. The result obtained by measurement. As shown in FIG. 6, the P2100 OTFT showed the performance of a typical p-type OTFT and obtained a hole mobility of 0.16 to 0.54 cm2 / Vs when a drain voltage of -40 to -100 V was applied.

FIG. 7 is a diagram illustrating a hole curve according to a gate curve and a transition curve of an N-channel of an organic thin film transistor of a bipolar top gate type in a state not treated with Cs ₂ CO ₃ .

As described above, since the Polyera P2100 organic polymer semiconductor material is a hole transport polymer, electron mobility was relatively low. As shown in FIG. 7, when a positive voltage is applied to the source / drain electrodes and the gate electrode of the P2100 OTFT, the characteristics of the n-type OTFT are shown in FIG. 7, but the performance is 10 compared to the p-type characteristics of FIG. 6. When the drain voltage of 40 to 100 V was applied, the electron mobility of 0.016 to 0.022 cm2 / Vs was obtained. Due to the imbalance in mobility of p-type and n-type, when a CMOS circuit is constructed using P2100 material or the speed of the circuit is reduced and a bipolar organic light emitting transistor is fabricated, light emission does not occur.

FIG. 8 is a diagram illustrating a hole curve according to a gate curve and a transition curve of a P-Channel of an organic thin film transistor of a bipolar top gate type in a state in which Cs ₂ CO ₃ is applied to only one electrode.

The result of FIG. 8 is to apply the technique proposed in the present invention when fabricating the P2100 OTFT of the top gate structure by applying Cs2CO3 to one electrode by spray coating method to improve the electron injection characteristics and at the same time to minimize the effect on the hole injection It was. As shown in the results of FIG. 8, the P2100 OTFT showed the performance of a typical p-type OTFT, and showed a hole mobility of 0.13 to 0.40 cm2 / Vs when a drain voltage of -40 to -100 V was applied. The Cs ₂ CO ₃ was applied to Cs ₂ CO ₃ , but the Cs ₂ CO ₃ was applied to only one electrode of the source / drain to reduce the hole injection efficiency. Spray application conditions were prepared by dissolving Cs ₂ CO ₃ in 2-ethoxyethanol solvent at a concentration of 1 mg / ml. The prepared ink was applied at a distance of 8 cm from the sample for 10 seconds using a spray coating machine. In general, if you apply a time between 6-20 seconds, high electron or hole injection properties can be obtained, and too thin or too thick thickness is formed to apply a time shorter than 6 seconds or longer than 20 seconds. It is difficult to obtain an improvement in the injection characteristics of holes.

FIG. 9 is a diagram illustrating a hole curve according to a gate curve and a transition curve of an N-channel of an organic thin film transistor of a bipolar top gate type in which Cs ₂ CO ₃ is applied to only one electrode.

The results of FIG. 9 were measured through the same transistors from which the results of FIG. 8 were obtained, and the characteristics of n-type OTFT were improved by applying Cs ₂ CO ₃ by applying a positive voltage to the source / drain electrodes and the gate electrode. Observed. As shown in FIG. 9, when a drain voltage of 40 to 100 V was applied, an electron mobility of 0.14 to 0.24 cm 2 / Vs was obtained. This will also improve the electromigration obtained more than 10 times compared to devices that are not coated with Cs ₂ CO ₃ because the electron injecting capability increased by the Cs ₂ CO ₃ treatment.

10 is a schematic diagram showing a step of selectively applying a metal salt solution to only one electrode using a spray coating. A source / drain electrode of Au is formed through the photolithography process on the glass, Si wafer, or plastic substrate. Typically, when manufacturing an OTFT, the spacing between Au source / drain electrodes is on the order of several um-several hundred um. On top of that, spray coating or other printing equipment described above may be used to selectively apply metal salt ink to the electrodes. In the case of spray coating, in order to selectively apply metal salt to one electrode, a metal salt solution to be applied is injected into the equipment, and a shadow mask, which is already patterned, is placed on the substrate on which the source / drain electrodes are formed. In this case, when the mask is open to only one of the source or drain electrodes and applied through the spray coating machine, the metal salt solution is applied to only one electrode of the source / drain and the other electrode is not applied. However, printing equipment such as inkjet printing capable of tens of um high-resolution patterns by the equipment itself does not require such a shadow mask process and can be applied only to desired electrodes directly through the printing equipment. After the application of the metal salt, the solvent is evaporated by applying heat to the substrate above the evaporation temperature of the used solvent to evaporate the used solvent and leave only the solid metal salt layer. Since the evaporation temperature of a conventional organic solvent is between 50 and 250 degrees Celsius, the temperature is added to the sample for 10 minutes through a hotplate to evaporate the solvent of the metal salt. Thereafter, various monomolecular or polymeric organic semiconductors described above are applied by a solution or vacuum deposition method to fabricate OTFT. The various polymers or insulators, such as SiO 2, are applied thereon by a solution or vacuum deposition method. Finally, the application of metals, such as Al, completes the manufacture of the top gate type OTFT.

FIG. 11 is a diagram illustrating a circuit diagram of an organic CMOS inverter fabricated after applying Cs ₂ CO ₃ to only an N-type electrode, and a gain value according to an output curve and a gate voltage. The CMOS inverter is a circuit in which a P-type OTFT and an N-type OTFT are 1: 1 coupled, and a detailed circuit diagram thereof is shown in FIG. 11. The semiconductor used is P2100 manufactured by Polyera, which is the same as the above result. In general, P2100 is a hole-transfer polymer, and thus, if Cs ₂ CO ₃ is not selectively applied to only one electrode, the P TYPE OTFT shows 10 times or more performance as shown in FIGS. The fabricated CMOS inverter shows a very low voltage gain of about 10-30, as shown in FIG. However, when one electrode of the organic CMOS inverter is selectively coated with a metal salt by the proposed technique, a high voltage gain of about 70 may be obtained as shown in FIG. 11. This corresponds to the highest voltage gain of organic CMOS inverters reported to date.

[Example 1: Fabrication of organic thin film transistor with improved electron and hole injection performance]

Source / drain electrodes of Au were formed through a printing process of inkjet printing using gold nanoparticles on a silicon substrate. The spacing between the two electrodes was spaced at 50 nm. In order to selectively apply metal salts only to the source electrode, a shadow mask, which has already been patterned, was placed on the substrate on which the source / drain electrodes were formed. Then, the ink prepared by dissolving Cs ₂ CO ₃ in a 2-ethoxyethanol solvent at a concentration of 1 mg / ml was applied using a spray coating machine at a distance of 8 cm from the sample for 10 seconds. Thereafter, the resultant was heated at 100 ° C. for 15 minutes using a hotplate to evaporate the remaining metal salt solvent.

In order to deposit the organic semiconductor, pentacene, a P-type organic semiconductor, was placed in a vacuum chamber, and then sublimed by applying a heat of 200 ° C. at 10 ⁻⁶ torr and then applied to a thickness of 30 to 70 nm. After applying PMMA to the thickness of 200 nm by spin coating, an organic thin film transistor was manufactured by depositing a gate electrode having a thickness of 60 nm using Al only in the channel region of the transistor using a shadow mask.

Example 2 Fabrication of Metal Oxide Semiconductor (CMOS) Digital Circuit with Improved Electron and Hole Injection Performance

In the same manner as in Example 1, a metal oxide semiconductor (CMOS) digital circuit was manufactured by forming a pattern corresponding to FIG. 11 through a photolithography process on a substrate.

[Example 3; Fabrication of Bipolar Transistors with Improved Electron and Hole Injection Performance]

In the same manner as in Example 1, OTFT was prepared by applying poly (9,9-dioctylfluorene-co-benzothiadiazole) (F8BT), an organic semiconductor material having bipolarity.

Example 4 Fabrication of Organic Light Emitting Diode Improved in Electron and Hole Injection Performance

OTFT was prepared in the same manner as in Example 1 by applying poly (9,9-dioctylfluorene-co-benzothiadiazole) (F8BT), a bipolar organic semiconductor material having excellent luminescence properties.

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Claims (20)

1. Board;

   A gate electrode located on the substrate;

   A gate insulating film disposed over the entire surface of the substrate including the gate electrode;

   Source / drain electrodes spaced apart from each other in a portion of the gate insulating layer;

   An electron or hole injection layer applied locally only on the source / drain electrodes through a printing process;

   An organic thin film transistor comprising: an organic semiconductor layer positioned on a substrate including the electron or hole injection layer.
2.  Board;

   A gate electrode located on the substrate;

   A gate insulating film disposed over the entire surface of the substrate including the gate electrode;

   Source / drain electrodes spaced apart from each other in a portion of the gate insulating layer;

   An electron injection layer applied to only one of the source / drain electrodes;

   An organic thin film transistor comprising: an organic semiconductor layer positioned on a substrate including the electron injection layer.
3.  Board;

   A gate electrode located on the substrate;

   A gate insulating film disposed over the entire surface of the substrate including the gate electrode;

   Source / drain electrodes spaced apart from each other in a portion of the gate insulating layer;

   A hole injection layer applied only to one of the source / drain electrodes;

   An organic thin film transistor comprising: an organic semiconductor layer positioned on a substrate including the electron injection layer.
4. The method according to any one of claims 1 to 3

   The electron injection layer or the hole injection layer is an organic thin film transistor, characterized in that the metal salt prepared by the solution process.
5.  The method of claim 4, wherein

   The electron injection layer or the hole injection layer is an organic thin film transistor, characterized in that the thickness of 0.1 ~ 5nm.
6.  The method of claim 4, wherein

   The electron injection layer is a metal salt selected from Cs ₂ CO ₃ , CsF, Rb ₂ CO ₃ , K ₂ CO ₃ , Na ₂ CO ₃ , LiF, CaF ₂ , MgF ₂ , NaCl, MgO,

   The organic semiconductor is an organic thin film transistor, characterized in that the N-type organic semiconductor
7.  The method of claim 4, wherein

   The hole injection layer is a metal salt selected from V ₂ O 5, MoO ₃ , F4TCNQ,

   The organic semiconductor is an organic thin film transistor, characterized in that the P- type organic semiconductor.
8.  Providing a substrate;

   Forming a gate electrode on the substrate;

   Forming a gate insulating film to cover the gate electrode;

   Forming a source / drain electrode on a portion of the gate insulating layer to be spaced apart from each other;

   Selectively applying an electron injection layer to only one of the source / drain electrodes;

   A method of manufacturing an organic thin film transistor, characterized in that to form an organic semiconductor layer over the entire substrate coated with the electron injection layer.
9.  Providing a substrate;

   Forming a gate electrode on the substrate;

   Forming a gate insulating film to cover the gate electrode;

   Forming a source / drain electrode on a portion of the gate insulating layer to be spaced apart from each other;

   Selectively applying a hole injection layer to only one of the source / drain electrodes;

   A method of manufacturing an organic thin film transistor, characterized in that to form an organic semiconductor layer over the entire surface of the substrate is coated with the hole injection layer
10.  The method of claim 8.

    The electron injection layer is an organic thin film, characterized in that the metal salt solution selected from Cs ₂ CO ₃ , CsF, Rb ₂ CO ₃ , K ₂ CO ₃ , Na ₂ CO ₃ , LiF, CaF ₂ , MgF ₂ , NaCl, MgO Method for manufacturing a transistor.
11.  The method of claim 9,

    The hole injection layer is a method of manufacturing an organic thin film transistor, characterized in that the metal salt solution selected from V ₂ O 5, MoO ₃ , F4TCNQ.
12.  The method according to any one of claims 8 to 9,

    Coating of the electron injection layer or the hole injection layer is a method of manufacturing an organic thin film transistor, characterized in that made through a patterning process
13.  The method of claim 12,

    The patterning process is a method of manufacturing an organic thin film transistor, characterized in that for printing a metal salt solution.
14.  The method of claim 13,

    The printing method of manufacturing an organic thin film transistor, characterized in that selected from inkjet printing, screen printing, spray coating, gravure printing, gravure offset printing, reverse gravure offset printing, nozzle printing, pad printing.
15.  Board;

    A gate electrode located on the substrate;

    A gate insulating film disposed over the entire surface of the substrate including the gate electrode;

    Source / drain electrodes spaced apart from each other in a portion of the gate insulating layer;

    A coated electron injection layer applied to any one of the source / drain electrodes;

    A hole injection layer applied to the remaining electrodes of the source / drain electrodes;

    N-type organic semiconductor layer located on the substrate of the electron injection layer

    A P-type organic semiconductor layer positioned on the substrate of the hole injection layer;

    Metal Oxide Semiconductor (CMOS) digital circuit composed of digital circuit including N-type and P-type organic semiconductor
16.  The method of claim 15,

    The electron injection layer is a metal salt solution selected from the electron injection layer,

    The hole injection layer is a metal oxide semiconductor (CMOS) digital circuit, characterized in that the metal salt solution selected from V ₂ O 5, MoO ₃ , F4TCNQ
17.  Board;

    A gate electrode located on the substrate;

    A gate insulating film disposed over the entire surface of the substrate including the gate electrode;

    Source / drain electrodes spaced apart from each other in a portion of the gate insulating layer;

    A coated electron injection layer applied to any one of the source / drain electrodes;

    A hole injection layer applied to the remaining electrodes of the source / drain electrodes;

    N-type organic semiconductor layer located on the substrate of the electron injection layer

    A bipolar organic thin film transistor having improved electron and hole injection performance, comprising: a P-type organic semiconductor layer positioned on a substrate of the hole injection layer
18.  The method of claim 17,

    The electron injection layer is a metal salt solution selected from Cs ₂ CO ₃ , CsF, Rb ₂ CO ₃ , K ₂ CO ₃ , Na ₂ CO ₃ , LiF, CaF ₂ , MgF ₂ , NaCl, MgO,

    The hole injection layer is a bipolar organic thin film transistor with improved electron and hole injection performance, characterized in that the metal salt solution selected from V ₂ O 5, MoO ₃ , F4TCNQ.
19.  Board;

    A gate electrode located on the substrate;

    A gate insulating film disposed over the entire surface of the substrate including the gate electrode;

    Source / drain electrodes spaced apart from each other in a portion of the gate insulating layer;

    A coated electron injection layer applied to any one of the source / drain electrodes;

    A hole injection layer applied to the remaining electrodes of the source / drain electrodes;

    N-type organic semiconductor layer located on the substrate of the electron injection layer

    P-type organic semiconductor layer positioned on the substrate of the hole injection layer; characterized in that the organic light emitting transistor with improved electron and hole injection performance
20.  The method of claim 19,

    The electron injection layer is a metal salt solution selected from Cs ₂ CO ₃ , CsF, Rb ₂ CO ₃ , K ₂ CO ₃ , Na ₂ CO ₃ , LiF, CaF ₂ , MgF ₂ , NaCl, MgO,

    The hole injection layer is an organic light emitting transistor with improved electron and hole injection performance, characterized in that the metal salt solution selected from V ₂ O 5, MoO ₃ , F4TCNQ

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