JP2007158002A - Organic electronic device and method for forming the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electronic device structure in which a mapping of a surface free energy is performed on a substrate surface by a very simple structure and means; and which materializes a large angle from the substrate surface and a sufficient azimuth anchor ring in an alignment of an organic semiconductor molecule, and has such a high and good adhesion that an electrode material forming a channel does not separate therefrom in a rubbing step also. <P>SOLUTION: By use of a laminate of an insulating layer containing insulating particulates and an insulating layer not containing the insulating particulates to be an alignment film; a micro-channel formation, a high adherence of electrodes, and a high angle alignment of organic semiconductor molecules are materialized, and the organic electronic device which has a good characteristic, such as an organic transistor of a high mobility, or the like is obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic electronic device including an organic semiconductor material, and more particularly to an organic thin film electronic device using an ink jet drawing process.

  In recent years, research on electronic devices using organic materials has been active. By making organic materials into thin films and applying them to devices, it is expected to realize electronic devices that are excellent in low-temperature process and portability and are inexpensive.

  For example, research on electronic devices such as organic EL, organic ID tags, and organic FETs is active. Among them, organic FETs are semiconductor materials themselves that are the heart of their functions. Since it is a relatively weakly bonded body that is covalently bonded, it can be expected to lower the temperature of the process, and since it is flexible and can be reduced in weight, it is excellent in portability. For this reason, there is a possibility of application to liquid crystal displays as well as paper-like displays, and in recent years, research has become active rapidly. One method for realizing the application of organic electronic devices in the field of electronic devices is to create an organic electronic device using an ink jet drawing process, which can be applied to next-generation low-temperature processes and highly portable electronic devices. Expected.

  There are various methods for manufacturing an organic electronic device. For example, Non-Patent Document 1 and Non-Patent Document 2 describe a method for manufacturing an organic TFT using a piezoelectric inkjet drawing process and surface mapping by surface free energy control. ing.

As another conventional example, Patent Document 1 can be cited.
Science 280, 2123 (2000) Tech Digest of IEDM, p.623 (2000) JP 2003-324202 A

  There are several methods for the ink jet drawing process. The main methods are a method using a piezoelectric actuator (piezo method), a thermal method, an electrostatic attraction method, etc. Especially, the piezo method and the thermal method have made remarkable progress in recent years as printers for consumer use. Increasing droplet speed and speed. In addition, high precision landing elasticity has greatly advanced, but due to the principle of ink jet drawing method, the more accurate the droplets are, the more difficult it is to land due to external factors. Currently, the region of 3σ <10 μm is considered to be almost impossible. However, electronic devices such as FETs are required to have a high accuracy of 1 μm or less in channel length, which is a major barrier that hinders the application of inkjet drawing methods with various advantages.

  In order to solve such problems, it is effective to map the substrate surface with surface free energy and induce fine droplets to form fine channels. As a method of forming a channel by mapping the surface of the substrate with surface free energy, a liquid repellent material with a low surface free energy is formed as a separator on the part where the channel on the material with a relatively high surface free energy is to be formed. A material that separates a high-energy solution-like electrode material is typical. In this case, an organic semiconductor layer is formed on a material having a low surface free energy, but an alignment treatment that improves the mobility of the organic semiconductor layer that affects the characteristics of the organic FET is difficult. On the other hand, as a method for solving such a problem, a method has been proposed in which a polyimide material is formed as a separator, and electrodes are separated and then rubbed to impart an alignment regulating force. In order to control the orientation of organic semiconductors, especially materials with a low molecular weight mainly composed of hopping conduction, it is considered important to have a large angle from the substrate surface and to increase the alignment regulating force (azimuth anchoring) in the planar direction. However, when the polyimide-based alignment film is rubbed as it is, the azimuth angle anchoring increases, but the angle from the substrate surface greatly decreases. In addition, when rubbing is performed after electrode firing and alignment regulation force is applied, both the source and drain electrodes are rubbed together, and when using a low-temperature firing type conductive paste or the like, there is a problem that it is easy to peel off from the substrate. appear. The present invention provides surface free energy mapping on the surface of the substrate with a very simple structure and means, realizes a large angle from the substrate surface and sufficient azimuth anchoring in the orientation of organic semiconductor molecules, and further provides a channel. The object is to realize an excellent organic electronic device structure having high adhesion that the electrode material to be formed does not peel even in the rubbing process.

  The configuration of the present invention for achieving the above object is as follows.

  According to a first aspect of the present invention, an organic electronic device including an organic semiconductor material, an insulating layer, and a plurality of electrodes has a laminate of an insulating layer containing insulating fine particles and an insulating layer not containing insulating fine particles as the insulating layer. The surface of the laminate on the insulating layer side that does not contain insulating fine particles has an uneven shape of 100 nm or less.

  A second aspect of the present invention is the organic electronic device according to the first aspect of the present invention, wherein the organic electronic device is a transistor.

  A third aspect of the present invention is the organic electronic device according to the second aspect of the present invention, wherein the transistor using the organic material is a field effect transistor (FET).

  A fourth aspect of the present invention is the organic electronic device according to any one of the first to third aspects of the present invention, wherein the insulating layer not containing the insulating fine particles is disposed between two different electrodes. .

  A fifth aspect of the present invention is the organic electronic device according to the fourth aspect of the present invention, wherein the insulating fine particles have a density of 10 / μm 2 to 100 / μm 2.

  A sixth aspect of the present invention is the organic electronic device according to the fourth to fifth aspects of the present invention, wherein the insulating fine particles have a diameter of 10 nm to 100 nm.

  A seventh aspect of the present invention is the organic electronic device according to the fourth to sixth aspects of the present invention, wherein the material of the insulating fine particles is an inorganic material.

  An eighth aspect of the present invention is the organic electronic device according to the fourth to seventh aspects of the present invention, wherein the material of the insulating layer containing the insulating fine particles is an inorganic material.

  A ninth aspect of the present invention is the organic electronic device according to the fourth to eighth aspects of the present invention, wherein the material of the insulating layer that does not contain the insulating fine particles is an organic material.

  A tenth aspect of the present invention is the organic electronic device according to any one of the fourth to ninth aspects of the present invention, wherein the material of the insulating layer not including the insulating fine particles is a polymer material.

  An eleventh aspect of the present invention is the organic electronic device according to any one of the fourth to tenth aspects of the present invention, wherein the material of the insulating layer not containing the insulating fine particles is a polymer material containing fluorine, It is in.

  A twelfth aspect of the present invention is the organic electronic device according to any one of the fourth to eleventh aspects of the present invention, wherein the material of the insulating layer not containing the insulating fine particles is a polyimide-based material containing fluorine. ,It is in.

  The thirteenth aspect of the present invention is the organic electron according to any one of the fourth to twelfth aspects of the present invention, wherein a thickness of the insulating layer not including the insulating fine particles is smaller than an average diameter of the insulating fine particles. On the device.

  According to a fourteenth aspect of the present invention, in the method for producing an organic electronic device using an organic semiconductor material, an electrode material constituting the organic electronic device is ejected by an inkjet method, and the inorganic insulating layer containing the insulating fine particles and the insulating material are insulated. An organic electronic device forming method is characterized in that an electrode material is separated by a laminate of insulating layers not containing fine particles.

(Function)
As a means for forming a channel of an organic FET, the present inventor has paid attention to a polymer alignment film having a concavo-convex shape and a low surface free energy. Typical examples of low surface free energy polymer alignment films include polyimide-based materials having fluorine groups in the side chain. By using an insulating layer containing insulating fine particles as the base of this material, surface irregularities can be formed. It is possible to form a low surface free energy alignment film having Since the surface of the alignment film has a fine concavo-convex shape, it is possible to control the alignment while maintaining a large angle from the substrate surface while realizing high azimuth anchoring with strong rubbing. On the other hand, a low-temperature firing type conductive paste or ink used for an electrode such as a source or a drain has only a metal component remaining after firing, so that adhesion to the substrate becomes a big problem. In particular, the adhesion with the flat polymer was not high, and the possibility of peeling off by rubbing treatment was high. However, by using an insulating film with insulating fine particles, the substrate has a shape anchoring effect between the insulating film and the electrode. It becomes possible to improve adhesiveness. Therefore, a low-surface free energy polymer alignment film having a concavo-convex shape is used as a separator, and a portion other than the separator is covered with an insulating layer containing insulating fine particles, so that a channel can be formed with high accuracy and also by rubbing. A highly adhesive electrode that does not peel off can be formed, and furthermore, the organic semiconductor layer can be controlled to a high orientation while maintaining a high orientation angle by rubbing to realize a high mobility.

  As described above, according to the present invention, in the configuration of the organic FET, an insulating layer containing insulating fine particles is formed on the substrate, and a polymer alignment layer having a high liquid emitting property is formed on the channel portion on the insulating layer. By forming it, the source / drain electrodes can be accurately separated by using the surface energy difference at the channel portion, and even when the rubbing treatment is performed, the adhesiveness with the base of the source / drain electrodes is high and does not peel off. Furthermore, by forming a low-molecular organic semiconductor layer on the alignment film in the channel part after rubbing, the orientation angle of the organic semiconductor molecules is high and aligned in one direction, which can realize very high mobility in hopping conduction. A structure can be realized. Further, an excellent organic FET can be realized by utilizing this structure. In addition to organic FETs, organic semiconductors between electrodes can be arranged at high orientation angles in various organic devices, and various devices using organic functional thin films, organic FETs, organic ID tags, organic EL, etc. Application to various devices can be expected.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  Hereinafter, the present invention will be described in detail. The present invention has various functions including an organic semiconductor layer, an insulating layer, and a plurality of electrodes, and the insulating layer includes an insulating layer including insulating fine particles and an insulating layer not including insulating fine particles. In this example and a comparative example, an example in which an organic FET is manufactured as an organic electronic device is shown.

  For the insulating fine particles in the present invention, any material showing insulating properties can be used regardless of organic or inorganic, but in particular, an inorganic material having high hardness such as SiO2, Al2O3, particularly a composite oxide material should be used. Is desirable. In addition, any material that exhibits insulating properties can be used for the inorganic insulating film containing insulating fine particles, but in particular, inorganic materials such as SiO2, Al2O3, Ta2O5, Ti-Si oxides, especially complex oxides. It is desirable to use an insulating material. Furthermore, any material that exhibits insulating properties can be used for the insulating layer that does not contain the insulating fine particles, and the organic semiconductor molecules are highly oriented due to the uneven shape formed by the lamination with the inorganic insulating layer containing the insulating fine particles. An organic insulating film such as polyimide or PVP (polyvinylphenol) that can provide an angle but generates uniaxial orientation regulation force by rubbing is desirable, especially surface free energy such as polyimide containing fluorine It is desirable to use a fluorine-containing polymer organic material that has a low surface roughness and can generate an alignment regulating force due to rubbing or the like. The insulating film in the present invention can be easily formed by various methods such as spin coating, ink jet drawing, offset printing, and screen printing. The gate electrode and the source / drain electrode can also be formed by various methods such as an ink jet drawing method and a screen printing method. Any film formation method can produce a thin film that functions sufficiently in the organic electronic device of the present invention.

  The laminated body of the insulating layer containing the insulating fine particles and the insulating layer not containing the insulating fine particles in the present invention may have any thickness, but it is desirable that the laminated body be formed as thin as possible from the knowledge of device characteristics. In particular, the insulating layer that does not contain the insulating fine particles is preferably about 10 to 20 nm which forms a film without forming an island shape.

  The organic semiconductor layer in the present invention includes various materials such as low molecular weight and high molecular weight materials, and any known material can be used, but high mobility is achieved especially when molecules are aligned vertically mainly with hopping conduction. A low molecular material such as pentacene, which has a high possibility of exhibiting a degree, is preferable. Low molecular organic semiconductors such as pentacene can be formed by vapor deposition. However, in the present invention, it is desirable to dissolve the precursor solution and form it by a coating method, and then baked to crystallize. .

  An organic FET provided with a laminate of an insulating layer containing insulating fine particles and an insulating layer not containing insulating fine particles according to the present invention will be briefly described with reference to FIGS. FIG. 1 shows an embodiment of a top gate type organic FET structure that best represents the present invention. As shown in FIG. 1, an insulating layer 12 containing insulating fine particles is formed on a sufficiently thick substrate 11, and an alignment film 13 which is an insulating layer not containing fine particles is formed only in part. Both side source / drain electrodes 15 are formed, and a semiconductor layer 14 for forming a channel is formed on the alignment film. An insulating film 16 is laminated on the source / drain electrodes and the semiconductor layer, and a gate electrode 17 is further formed. FIG. 2 shows a bottom gate type structure. As shown in FIG. 2, a gate electrode 17 is formed on a sufficiently thick substrate 11, and an insulating layer 16 is formed thereon. Further, an insulating layer containing insulating fine particles is formed thereon, and an alignment film, which is an insulating layer not containing insulating fine particles, is formed on a part of the insulating layer. Both side source / drain electrodes 15 are formed, and a semiconductor layer 14 for forming a channel is formed on the alignment film. FIG. 3 is a conceptual diagram of a rubbing process for imparting orientation regulating force. Detailed specific examples are shown below.

  An example in which a top gate type organic FET provided with a laminate of an insulating layer containing insulating fine particles and an insulating layer not containing insulating fine particles was produced using an ink jet drawing method as a method of forming a source / drain and a gate is given. . As an insulating layer containing insulating fine particles on a liquid crystalline polymer substrate, a SiO2 oxide containing SiO2 fine particles with a diameter of 50 nm is applied to the liquid crystal polymer substrate by offset printing so that the portion other than the fine particles has a thickness of about 20 nm. After irradiating with UV, baking was performed in an oven at 250 ° C. for 60 minutes. The unevenness of the SiO2 fine particle portion was exposed to about 40 nm on the average with respect to the SiO2 oxide layer. The density of SiO2 fine particles was about 50 particles / μm2. On top of this, 10 nm of low surface energy polyimide having fluorine side chains as an insulating layer containing no insulating fine particles was formed by offset printing and baked in an oven at 200 ° C. for 60 minutes. The polyimide surface was masked with a resist, and the polyimide was removed by chemical dry etching, leaving a portion where the channel was to be formed with a width of 5 μm. The insulating layer containing the insulating fine particles is an inorganic material and functions as an etch stop layer, and all remains. After the resist was removed, source / drain electrodes were formed using an ink jet drawing method. The electrode material used was a colloidal gold colloid dispersed in an aqueous solution, and this solution was applied by ink-jet drawing onto a low surface energy polyimide that would become the channel. The surface energy was very low at 30 mN / m, so gold The colloidal solution separated into two on the polyimide, and it moved and stabilized spontaneously on both sides of the channel part. In this state, baking was performed in an oven at 250 ° C. for 60 minutes, and the gold colloid to be the source and drain was fused to each other and completely metallized to form an electrode. After forming the source / drain electrodes, a rubbing treatment was performed at 1000 rpm using a cotton rubbing roller to perform an orientation treatment. Even when the rubbing treatment was performed, the adhesion between the source / drain electrodes and the insulating layer containing the insulating fine particles was high, and defects such as peeling did not occur. After the rubbing is completed, the substrate is cleaned, and then a pentacene precursor chloroform solution is formed as a semiconductor layer on a low surface energy polyimide that becomes a channel by 100 nm by an ink jet drawing method and baked in an oven at 200 ° C. for 60 minutes. Crystallized. When the crystal state was measured by XRD, it was oriented in one rubbed direction while maintaining a high orientation angle. The channel length was 5 μm. Further, a high pressure-resistant polyimide layer serving as an insulating film was formed thereon by spin coating and baked in an oven at 200 ° C. for 60 minutes. A gate electrode layer was formed on the portion directly above the channel length by an ink jet drawing method. Similar to the source / drain electrodes, a gold colloid dispersion was used as the electrode material, and the droplet diameter was 20 μm. Firing was performed in an oven at 250 ° C. for 60 minutes.

  In this embodiment, both the insulating fine particles and the insulating layer containing the insulating fine particles use SiO2, but other inorganic insulating materials such as Al2O3 and Ta2O5 can also be used. In addition, organic insulating materials such as polyimide, polyamide, and polyamideimide can be used together.

  In this embodiment, insulating fine particles having a diameter of 50 nm are used. However, as a result of intensive studies by the present inventors, an effect can be expected at any diameter in the range of 10 nm to 100 nm. When the diameter of the insulating fine particles is less than 10 nm, the effect of increasing the orientation angle of the organic semiconductor molecules after rubbing is low, and when the diameter of the insulating fine particles exceeds 100 nm, the organic semiconductor molecules are aligned in one direction after rubbing. The effect becomes weak and the effect of the present invention cannot be expected. Further, by controlling the thickness of the insulating layer containing the insulating fine particles in each diameter within a range equal to or smaller than the diameter of the insulating fine particles, unevenness (heading) due to the fine particles can be controlled.

  Further, in this example, the density of the insulating fine particles was about 50 particles / μm 2, but as a result of intensive studies by the present inventors, the density of the insulating fine particles was in the range of 10 particles / μm 2 to 100 particles / μm 2. An effect can be expected in density. When the density of insulating fine particles is less than 10 particles / μm2, the effect of increasing the orientation angle of organic semiconductor molecules after rubbing is low, and when the density of insulating fine particles exceeds 100 particles / μm2, organic semiconductor molecules are The uniaxial alignment effect arranged in one direction becomes weak, and the effect of the present invention cannot be expected.

  In this embodiment, pentacene is used for the semiconductor layer, but it is also possible to use a soluble precursor of another low molecular semiconductor material or a low molecular semiconductor material in which the material itself is soluble. It is also possible to form a polymer organic semiconductor material using a material in which hopping conduction is more dominant than main chain conduction.

  In this embodiment, a solution in which colloidal gold is dispersed in the conductive materials of the source, drain, and gate is used. However, any highly conductive metal colloid solution that can be fired at a low temperature by forming nanoparticles such as Pt is used. It is also possible to use it. Organic conductive materials such as PEDOT / PSS solutions that can be applied by ink jet drawing can also be used.

  Furthermore, in this embodiment, an example in which a top gate type organic FET is fabricated is shown, but it is also possible to fabricate a bottom gate type organic TFT as shown in FIG. 2 by forming each layer by the same manufacturing method. is there.

  Wiring was performed on the gate, source and drain on the formed top gate type organic FET. When the characteristics of the organic FET formed using a semiconductor parameter analyzer were measured, it had high mobility of about 1 cm2 / V · s and showed good FET characteristics.

(Comparative example)
A top gate type organic FET was fabricated in the same manner as in Example 1 except that an insulating layer containing insulating fine particles was not provided on the substrate. On the liquid crystal polymer substrate, a low surface energy polyimide having a fluorine-based side chain was formed as an alignment film to a thickness of 10 nm by offset printing, and baked at 200 ° C. The polyimide surface was masked with a resist, and the polyimide was removed by chemical dry etching, leaving a portion where the channel was to be formed with a width of 5 μm. After the resist was removed, source / drain electrodes were formed using an ink jet drawing method. The electrode material used was a colloidal gold colloid dispersed in an aqueous solution, and this solution was applied by ink-jet drawing onto a low surface energy polyimide that would become the channel. The surface energy was very low at 30 mN / m, so gold The colloidal solution separated into two on the polyimide, and it moved and stabilized spontaneously on both sides of the channel part. In this state, firing was performed at 250 ° C. to completely metallize the gold electrode serving as the source / drain. After forming the source / drain electrodes, a rubbing process was performed at 1000 rpm using a cotton rubbing roller, and an alignment process was performed. Due to poor adhesion between the source / drain electrodes and the substrate, some peeling defects occurred. . After completion of the rubbing, the substrate was washed, and then a pentacene precursor solution was formed as a semiconductor layer to 100 nm on the low surface energy polyimide serving as a channel by an ink jet drawing method, followed by drying to crystallize. When the crystal state was measured by XRD, it was oriented in one direction of rubbing, but the orientation angle was almost 0 degrees with respect to the substrate surface and the axis was completely oriented in the rubbing direction. The state was not preferable. The channel length was 5 μm. Further, a high pressure-resistant polyimide layer serving as an insulating film was formed thereon by spin coating and baked at 200 ° C. A gate electrode layer was formed on the portion directly above the channel length by an ink jet drawing method. Similar to the source / drain electrodes, a gold colloid dispersion was used as the electrode material, and the droplet diameter was 20 μm. Firing was performed at 250 ° C.

  Wiring was performed on the gate, source and drain on the formed organic FET. Using a semiconductor parameter analyzer, we measured the characteristics of the organic FET that did not peel off when the electrode was rubbed. As a result, the mobility was about 0.01 cm2 / V · s, which was about two orders of magnitude lower than when the orientation angle of pentacene was high. FET characteristics could not be obtained.

It is sectional drawing of the top gate type organic FET at the time of providing the laminated body of the insulating layer containing fine particle and the insulating layer which does not contain fine particle applied to description of the Example of this invention. It is sectional drawing of the bottom gate type organic FET at the time of providing the laminated body of the insulating layer containing a fine particle and the insulating layer which does not contain a fine particle applied to description of the Example of this invention. It is a rubbing conceptual diagram at the time of providing the laminated body of the insulating layer containing fine particles and the insulating layer which does not contain fine particles applied to description of the Example of this invention.

Explanation of symbols

11 Substrate on which organic FETs are formed
12 Insulating film containing fine particles
13 Alignment film
14 Semiconductor layer
15 Source and drain electrodes
16 Insulating film
17 Gate electrode
18 Rubbing roller

Claims (14)

  In an organic electronic device including an organic semiconductor material, an insulating layer, and a plurality of electrodes, the insulating layer has a laminate of an insulating layer containing insulating fine particles and an insulating layer not containing insulating fine particles, and the insulating fine particles An organic electronic device characterized in that the surface of the laminate on the insulating layer side not containing has an uneven shape of 100 nm or less.   2. The organic electronic device according to claim 1, wherein the organic electronic device is a transistor.   3. The organic electronic device according to claim 2, wherein the transistor using the organic material is a field effect transistor (FET).   4. The organic electronic device according to claim 1, wherein the insulating layer containing no insulating fine particles is disposed between two different electrodes.   5. The organic electronic device according to claim 4, wherein the density of the insulating fine particles is 10 / μm 2 or more and 100 / μm 2 or less.   6. The organic electronic device according to claim 4, wherein the insulating fine particles have a diameter of 10 nm or more and 100 nm or less.   7. The organic electronic device according to claim 4, wherein the material of the insulating fine particles is an inorganic material.   The organic electronic device according to any one of claims 4 to 7, wherein a material of the insulating layer containing the insulating fine particles is an inorganic material.   9. The organic electronic device according to claim 4, wherein a material of the insulating layer not including the insulating fine particles is an organic material.   10. The organic electronic device according to claim 4, wherein the material of the insulating layer not including the insulating fine particles is a polymer material.   11. The organic electronic device according to claim 4, wherein the material of the insulating layer not including the insulating fine particles is a polymer material containing fluorine.   12. The organic electronic device according to claim 4, wherein the material of the insulating layer not including the insulating fine particles is a polyimide-based material containing fluorine.   13. The organic electronic device according to claim 4, wherein a thickness of the insulating layer not including the insulating fine particles is smaller than an average diameter of the insulating fine particles.   In a method for producing an organic electronic device using an organic semiconductor material, an electrode material constituting the organic electronic device is ejected by an inkjet method, and the insulating layer including the insulating fine particles and the insulating layer not including the insulating fine particles are stacked. A method for producing an organic electronic device, wherein the electrode material is separated and the molecules of the organic semiconductor layer are oriented.

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