JP2011187750A - Method of manufacturing organic thin film transistor, method of manufacturing organic thin film transistor array, and method of manufacturing display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an organic thin film transistor with a high yield. <P>SOLUTION: The method of manufacturing the organic thinfilm transistor includes: an electrode forming process of forming a source electrode and a drain electrode on a substrate or an insulating film on the substrate; an electrode processing process of increasing the angle of contact of a semiconductor ink to the source electrode and the drain electrode to be greater than that to the substrate or the insulating film during the supply of the organic semiconductor ink; and a semiconductor layer forming process of forming an organic semiconductor layer by supplying the organic semiconductor ink between the formed source electrode and drain electrode, wherein an equation, W>ϕ+X, is satisfied, when W is a channel width of the channel formed by the source electrode and the drain electrode, ϕ is the droplet diameter of a droplet during the supply of the organic semiconductor ink, and X is a range of error of landing positions, the error of a position to which the droplet is supplied. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an organic thin film transistor manufacturing method, an organic thin film transistor array manufacturing method, and a display device manufacturing method.

  Organic thin-film transistors (TFTs) using organic materials are highly flexible due to the variety of material structures, manufacturing methods, product forms, etc., can be easily increased in area, and can have a simple layer structure. It has been studied energetically because it has advantages such as the ability to simplify the process and the ability to manufacture using inexpensive manufacturing equipment. Examples of film formation methods for electrodes, insulating films, and semiconductor layers that constitute the organic TFT include a printing method, a spin coating method, and a dipping method. The organic TFT is more digit than a TFT using a conventional Si semiconductor material. Can be manufactured cheaply in the difference.

  Further, if an organic TFT array in which the organic TFTs are integrated is manufactured and the display element is driven, a display device can be obtained. This display device has an unprecedented added value with the characteristics of the organic TFT. For example, in Non-Patent Document 1, an organic TFT array produced in a printing process is combined with an electrophoretic element to produce a flexible display device. Such characteristics are directly linked to advantages such as applicability to a display panel on a curved wall, convenience as a portable display, and resistance to damage when dropped (impact resistance). Furthermore, the cost merit by producing in a printing process is reflected.

  When integrating organic TFTs, it is essential to form electrodes. In the pattern formation of the electrodes, if the pattern accuracy of the printing process is low, the organic TFT malfunctions due to a short circuit between the electrodes. On the other hand, Patent Document 1 discloses a process of forming a wettability changing layer including a material whose critical surface tension is changed by applying energy, and more critical surface tension by applying energy to a part of the wettability changing layer. Forming a pattern with different critical surface tensions consisting of a low surface energy part with a small surface area and a high surface energy part with a higher critical surface tension, and a change in wettability with a pattern formed from a liquid containing a conductive material A method for producing a laminated structure comprising: forming a conductive layer on a high surface energy portion by applying to a surface of a layer; and forming a semiconductor layer on a wettability changing layer. It is disclosed.

  Moreover, when producing an organic TFT, it is essential to form a pattern of an organic semiconductor material. When organic TFTs are integrated without patterning the organic semiconductor layer, an off-current is generated during the operation of the transistor due to the influence of the organic semiconductor layer formed outside the channel region, resulting in an increase in power consumption. In addition, when displaying pixels, it also causes crosstalk. Note that when a TFT using a Si semiconductor material is manufactured, the Si semiconductor material is patterned by photolithography and etching.

  Focusing only on pattern formation of the organic semiconductor layer, a photoresist is applied, a desired pattern is exposed and developed, a resist pattern is formed, etching is performed using this as an etching mask, and the resist is peeled to form a pattern. It is possible. However, when a polymer material is used as the organic semiconductor material, transistor characteristics may be deteriorated if a pattern is formed by applying a photoresist on the polymer material. As the photoresist, a novolac resin having naphthoquinonediazide as a photosensitive group dissolved in an organic solvent such as xylene or cellosolve solvent is used, and the polymer material is an organic solvent contained in the photoresist. Often dissolves in In addition, when a crystalline molecule such as pentacene is used as the organic semiconductor material, the transistor characteristics may be similarly deteriorated although there is a difference in degree. Furthermore, it may be damaged by a stripping solution such as ethylene glycol monobutyl ether or monoethanolamine used when stripping the resist, or may be damaged by pure water rinsing after stripping the resist. From the above, it can be seen that it is difficult to form a pattern of an organic semiconductor layer by conventional photolithography and etching.

  Patent Document 2 discloses a method of applying a charge to a predetermined position on a surface to be coated and applying a charge having a polarity opposite to that of the charge to the coating material to guide the material to which the charge is applied by a Coulomb force to the predetermined position. Appropriate combination of a method in which a recess is formed in a predetermined position and a coating material is applied and deposited in the recess, or a pattern is formed by evaporating the solvent after applying the material and then irradiating the pattern with a laser. A method for manufacturing an organic thin film transistor is disclosed.

  In Patent Document 3, a conductive layer is provided over a substrate, a mask having at least one window is provided over the conductive layer, the conductive layer is etched through the window, and an opening is formed in the conductive layer. Partially defining the source and drain of the transistor, depositing a conductive material through the window to form the gate of the metal transistor in the opening, and forming a metal oxide dielectric layer over the gate And a method of manufacturing a transistor comprising introducing a semiconductor material between the source and drain, on the gate, and in a space between the source or drain and the gate to form a semiconductor body of the transistor. ing. Etching is performed so as to cause an undercut at the peripheral edge of the window so that the opening has a larger extent than the window in a direction parallel to the surface of the substrate, and the conductive material is deposited at the peripheral edge of the gate. Further, the metal gate deposition is performed so that the peripheral edge of the gate of the transistor is closely aligned with the peripheral edge of the opening so as to be separated from the drain.

  However, these methods have problems such as a decrease in throughput due to an increase in process steps and an increase in manufacturing cost.

  On the other hand, an inkjet method is known as a pattern forming method. Since the ink jet method can directly draw a pattern, the material usage rate can be significantly improved. When the organic semiconductor layer is patterned by such an ink jet method, there is a possibility that the manufacturing process can be simplified and the cost can be reduced. At this time, when a material soluble in an organic solvent is used as the organic semiconductor material, a solution of the organic semiconductor material (organic semiconductor ink) can be prepared. Therefore, the organic semiconductor layer can be patterned by an inkjet method. .

  In order to stably form an organic semiconductor layer in a channel portion composed of a gate insulating film, a source electrode, and a drain electrode of a transistor by such a printing method, it is necessary to control the behavior after ink landing. . Generally, the surface of the source and drain electrodes made of metal has a high surface energy, so that the contact angle of the organic semiconductor ink is small and the surface is easily wetted. In comparison, the surface of the gate insulating film composed of organic polymer or the like has a surface energy relatively lower than that of the electrode, and the contact angle of the organic semiconductor ink is often high. For this reason, the organic semiconductor ink dropped on the channel portion moves onto the electrode that is more likely to get wet after landing, and is formed only on the electrode, so that the channel may not be formed. This tendency becomes more remarkable when the surface energy of the gate insulating film is smaller than the surface tension of the ink. If the organic semiconductor layer is not formed in the channel portion, the organic thin film transistor does not operate. In a display device in which a display element is combined with an organic thin film transistor array in which a plurality of organic thin film transistors are arranged, if there is an organic thin film transistor that does not operate due to the above problem, the pixel becomes defective. Therefore, it is necessary to reduce pixel defects as much as possible in the display device.

  As a technique for solving this problem, Patent Document 4 discloses a technique in which a gate insulating film and a channel formed of a source electrode and a drain electrode have an opening and a barrier formed of a fluorine-based polymer substance is installed. Are listed. This makes it possible to control the ink landing position and the spread after landing, but there are problems such as a decrease in throughput and an increase in manufacturing cost due to an increase in process steps.

  Another method is to adjust the physical properties of the ink. First, by reducing the surface tension of the solvent, it is possible to make the surface of the gate insulating film with a low surface energy easy to get wet, but on the other hand, reducing the surface tension means that the droplet spreads after landing. Therefore, an organic semiconductor layer is formed in addition to the channel portion, and problems such as an increase in off-leakage and crosstalk may occur.

  Or, secondly, by lowering the boiling point of the solvent and drying the ink as soon as possible after landing, it is possible to prevent the ink from moving onto the electrode after landing. In terms of stability, the boiling point of the ink decreases and it becomes easy to dry, so that the ink is dried on the nozzle surface, leading to unstable ejection and non-ejection due to clogging.

  Furthermore, as another solution, the surface energy of the electrode is adjusted by treating the surface of the electrode with a self-assembled monolayer (SAM) typified by a silane coupling agent or alkanethiol. However, there is a method for controlling the contact angle of ink.

  For example, Non-Patent Document 2 reports that by treating the surface of the Au electrode with alkanethiol, the contact angle of the organic solvent can be changed as the surface energy of the electrode changes without impairing the transistor characteristics. ing.

  In this way, the ink contact angle on the electrode surface can be controlled by contacting the molecule having a site that binds to the electrode surface. The ink contact angle of the electrode after monomolecular film adsorption can be controlled by the molecular design of adsorbed molecules. As a result, the ink wettability between the electrode surface and the gate insulating film surface can be adjusted to be equal, and the ink can be held in the channel portion after the droplets have been deposited to form a film.

  However, in practice, it is very difficult to adjust the ink wettability of the electrode surface and the gate insulating film surface equally. This is because the reproducibility and uniformity of the SAM treatment process that changes the ink wettability of the electrode is important, but in order to ensure these, treatment time such as immersion for 10 hours or more is required. In short-time processing, the reproducibility and uniformity of the electrode processing effect deteriorates. As a result, the balance between the wettability of the electrode surface and the gate insulating film surface is lost, and the organic semiconductor layer is stably used as the channel portion. It becomes difficult to form. For this reason, it is difficult to perform stable patterning by controlling the wettability of the organic semiconductor ink to the electrode surface and the insulating film surface to be the same by the SAM treatment.

  From the above, when the organic semiconductor layer is formed by an inkjet method or the like on the channel portion composed of the electrode having a lower organic semiconductor ink contact angle and the gate insulating film having a higher organic semiconductor ink contact angle, A method of stably patterning has not been obtained so far.

  In view of the above prior art, the present invention provides an organic thin film transistor manufacturing method capable of improving the yield of organic semiconductor layer pattern formation by an inkjet method, an organic thin film transistor array manufacturing method having a plurality of the organic thin film transistors, and the organic thin film transistor array. It aims at providing the manufacturing method of the display apparatus which has this.

  The present invention provides an electrode forming step of forming a source electrode and a drain electrode on a substrate or an insulating film on the substrate, and the organic semiconductor ink on the source electrode and the drain electrode when the organic semiconductor ink is supplied. An electrode processing step for making the contact angle higher than the contact angle on the substrate or the insulating film, and forming the organic semiconductor layer by supplying the organic semiconductor ink between the formed source electrode and the drain electrode A semiconductor layer forming step, wherein a channel width of a channel formed by the source electrode and the drain electrode is W, a droplet diameter of the droplet when the organic semiconductor ink is supplied is φ, When the landing position error width, which is an error in the position where the droplet is supplied, is X, W> φ + X is satisfied.

  Further, the present invention is characterized in that W> φ + X + Y is satisfied, where Y is an error due to expansion / contraction of the substrate.

  In the semiconductor layer forming step, the organic semiconductor ink may be supplied by an ink jet method.

  In addition, the present invention is characterized in that the source electrode and the drain electrode are modified with a self-assembled monolayer.

  Moreover, the present invention is characterized in that the self-assembled monolayer includes alkanethiol.

  In addition, the present invention includes a gate electrode forming step of forming a gate electrode on the substrate and a gate insulating film forming step of forming a gate insulating film on the gate electrode before the electrode forming step. The source electrode and the drain electrode in the electrode forming step are formed on the gate insulating film.

  Moreover, this invention is a manufacturing method of the organic thin-film transistor array which has multiple organic thin-film transistors, Comprising: The said organic thin-film transistor is an organic thin-film transistor manufactured by the manufacturing method of the said organic thin-film transistor, It is characterized by the above-mentioned.

  In addition, the present invention is characterized by having a step of forming a display element on the organic thin film transistor array manufactured by the method for manufacturing an organic thin film transistor array described above.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of an organic thin-film transistor with a high yield, the manufacturing method of an organic thin-film transistor array, and the manufacturing method of a display apparatus can be provided.

Structure diagram of organic thin-film transistor in the first embodiment Explanatory drawing of the organic thin-film transistor in 1st Embodiment When organic semiconductor ink is supplied (contact angle: electrode <gate insulating film) (1) When organic semiconductor ink is supplied (contact angle: electrode <gate insulating film) (2) Explanatory drawing of when organic semiconductor ink is supplied (contact angle: electrode> gate insulating film) (1) Explanatory drawing of supplying organic semiconductor ink (contact angle: electrode> gate insulating film) (2) Enlarged view in Fig. 6 (b) Explanatory drawing (1) of the manufacturing method of the organic thin-film transistor in 1st Embodiment Explanatory drawing (2) of the manufacturing method of the organic thin-film transistor in 1st Embodiment Explanatory drawing (3) of the manufacturing method of the organic thin-film transistor in 1st Embodiment Flowchart of manufacturing method of organic thin film transistor in first embodiment The block diagram of the organic thin-film transistor array in 2nd Embodiment Flowchart of manufacturing method of organic thin film transistor array and display device in second embodiment The block diagram of the display apparatus in 2nd Embodiment The block diagram of the other display apparatus in 2nd Embodiment Explanatory drawing of the comparative example 1 Explanatory drawing of the comparative example 2 Explanatory drawing of Example 1 Correlation diagram between channel width W and yield in Comparative Example 3 and Example 2 Correlation diagram between organic semiconductor ink supply conditions and yield

  An embodiment of the present invention will be described.

[First Embodiment]
The organic thin film transistor in the first embodiment will be described.

  FIG. 1 shows the structure of the organic thin film transistor in this embodiment. FIG. 1A is a top view of the organic thin film transistor according to the present embodiment, and FIG. 1B is a cross-sectional view taken along a broken line 1A-1B in FIG.

  In the organic thin film transistor according to this embodiment, a gate electrode 12 is formed on a substrate 11, a gate insulating film 13 is formed on the gate electrode 12, and a source electrode 14 and a drain electrode 15 are formed on the gate insulating film 13. An organic semiconductor film 16 is formed between the source electrode 14 and the drain electrode 15 on the gate insulating film 13. In the source electrode 14, the drain electrode 15, and the organic semiconductor film 16, a channel is formed in the organic semiconductor film 16 when a voltage is applied to the gate electrode 12, so that a current flows between the source electrode 14 and the drain electrode 15. In addition, it is formed at a predetermined position. The organic semiconductor film 16 is formed by a printing method such as an ink jet method.

  Next, a channel in the organic thin film transistor in the present embodiment will be described with reference to FIG. FIG. 2 shows a state before the organic semiconductor film 16 is formed. 2A is a top view of this state, and FIG. 2B is a cross-sectional view taken along the broken line 2A-2B in FIG. 2A. As described above, the organic semiconductor film 16 forms a channel. At this time, the channel is formed on the gate electrode 12 with the gate insulating film 13 interposed therebetween, and the drain electrode 15 and the source electrode 14 are opposed to each other. The channel width W is a channel length L, and the distance between the drain electrode 15 and the source electrode 14 in this region is the channel length L.

  Next, based on FIG.3 and FIG.4, the process at the time of forming the organic-semiconductor layer 16 by dripping an organic-semiconductor ink by the inkjet method is demonstrated. The organic semiconductor layer 16 is dropped on a predetermined position on the gate electrode 12 through the gate insulating film 13 to form a channel between the drain electrode 15 and the source electrode 14. Therefore, the organic semiconductor layer 16 is formed in contact with the gate insulating film 13, the source electrode 14 and the drain electrode 15. In general, the surface of the metal material forming the source electrode 14 and the drain electrode 15 has a high surface energy, and the contact angle of the dropped organic semiconductor ink is small on the surface of the source electrode 14 and the drain electrode 15, resulting in wetting. Easy to spread. In contrast, the surface of the gate insulating film 13 formed of an organic polymer material or the like generally has a relatively low surface energy as compared with a metal material, and the contact angle of the dropped organic semiconductor ink is high. It gets wet and spreads lower.

  This will be described with reference to FIGS. FIG. 3 is a side view, and FIG. 4 is a top view.

  First, as shown in FIGS. 3A and 4A, an organic semiconductor ink 16 a for forming the organic semiconductor film 16 is dropped on the gate insulating film 13, the source electrode 14, and the drain electrode 15. In this state, the organic semiconductor ink 16a has not landed.

  Next, as shown in FIG. 3B and FIG. 4B, the organic semiconductor ink 16a lands on the gate insulating film 13 between the source electrode 14 and the drain electrode 15 to be a region where a channel is formed. .

  Next, as shown in FIG. 3C and FIG. 4C, the dropped organic semiconductor ink 16a spreads in a wet manner, and in particular, wets and spreads well on the source electrode 14 and the drain electrode 15 having a high surface energy.

  Next, as shown in FIG. 3D and FIG. 4D, the dropped organic semiconductor ink 16a moves to the source electrode 14 and the drain electrode 15 having a high surface energy that tends to wet and spread, and the source electrode On the gate insulating film 13 between 14 and the drain electrode 15, the organic semiconductor ink 16a does not exist. In such a state, the organic semiconductor layer 16 for forming a channel is not formed between the source electrode 14 and the drain electrode 15, so that an organic semiconductor transistor cannot be formed, resulting in a decrease in yield. End up. Such a phenomenon occurs more remarkably particularly when the surface energy of the gate insulating film 13 is smaller than the surface tension of the organic semiconductor ink.

  For this reason, in this embodiment, the surfaces of the source electrode 14 and the drain electrode 15 are treated with a self-assembled monolayer, and the contact angle of the organic semiconductor ink 16a on the surfaces of the source electrode 14 and the drain electrode 15 is controlled. , Control wet spread. Specifically, various alkanethiols are adjusted to a molar concentration of 0.1 to 100 mM in a soluble solvent such as ethanol, and the substrate 11 on which the source electrode 14 and the drain electrode 15 are formed is immersed for about 10 minutes. Thus, surface treatment is performed by chemical reaction on the surfaces of the thiol and the source electrode 14 and the drain electrode 15. Thereby, the contact angle of the organic semiconductor ink 16a on the surface of the source electrode 14 and the drain electrode 15 can be controlled. The surface treatment may be a surface treatment using a thiol solution vapor, and the treatment time is adjusted to obtain a desired surface state.

  By such surface treatment, the surfaces of the source electrode 14 and the drain electrode 15 are decorated with various alkyl groups, the contact angle with the organic semiconductor ink 16a can be increased, and the wetting and spreading property of the organic semiconductor ink 16a is controlled. can do.

  On the other hand, if the contact angle of the organic semiconductor ink 16a on the source electrode 14 and the drain electrode 15 becomes too high due to the surface treatment of the source electrode 14 and the drain electrode 15, the yield of the organic thin film transistor formed in the same manner is reduced. I will.

  This will be described with reference to FIGS. FIG. 5 is a side view, and FIG. 6 is a top view.

  First, as shown in FIGS. 5A and 6A, an organic semiconductor ink 16 a for forming the organic semiconductor film 16 is dropped on the gate insulating film 13, the source electrode 14, and the drain electrode 15. In this state, the organic semiconductor ink 16a has not landed.

  Next, as shown in FIGS. 5A and 6B, the organic semiconductor ink 16a lands on the gate insulating film 13 between the source electrode 14 and the drain electrode 15 which are regions where channels are formed. .

  Next, as shown in FIGS. 5 (c) and 6 (c), the dropped organic semiconductor ink 16a spreads out and avoids especially on the source electrode 14 and the drain electrode 15 having relatively low surface energy, It spreads well on the gate insulating film 13 having a relatively high surface energy.

  Next, as shown in FIGS. 5 (d) and 6 (d), the dropped organic semiconductor ink 16a is on the gate insulating film 13 having a relatively high surface energy, which easily spreads, and forms a channel. Thus, the organic semiconductor ink 16a does not exist on the gate insulating film 13 between the source electrode 14 and the drain electrode 15. In such a state, the organic semiconductor layer 16 for forming a channel is not formed between the source electrode 14 and the drain electrode 15, so that an organic semiconductor transistor cannot be formed, resulting in a decrease in yield. End up.

  The above will be described with reference to FIG. FIG. 7 is an enlarged view of FIG. As shown in FIG. 7, when the surface energy on the surface of the source electrode 14 and the drain electrode 15 is lower than the surface energy on the surface of the gate insulating film 13, the dropped organic semiconductor ink 16 a It moves from the surface of the source electrode 14 and the drain electrode 15 and moves toward the surface of the wide gate insulating film 13 having a relatively high surface energy. That is, the organic semiconductor ink 16a moves because a force that the droplets at the edge portion of the channel wets and spreads on the gate insulating film 13 having a lower contact angle. This is called an edge effect. For this reason, the organic semiconductor ink 16a does not exist in the region where the channel region is to be formed, leading to a decrease in the yield of the formed organic semiconductor transistor.

Therefore, the organic semiconductor transistor manufacturing method according to the present embodiment treats the surfaces of the source electrode 14 and the drain electrode 15 with a self-assembled monolayer so that the organic semiconductor ink on the surfaces of the source electrode 14 and the drain electrode 15 is treated. The contact angle of the organic semiconductor ink in the gate insulating film 13 is higher than the contact angle of the organic semiconductor ink. Further, the channel width W is the droplet diameter φ of the organic semiconductor ink 16a supplied by the inkjet method and the inkjet landing position error width X. Is larger than the sum of errors Y due to expansion and contraction of the substrate 11, that is, the following equation (1) is satisfied.

W> φ + X + Y (1)

Note that the equation shown in (1) above assumes that the substrate 11 is stretched and the error Y does not need to be considered when the substrate 11 is hardly stretched. Therefore, in such a case, it suffices if the following equation (2) is satisfied.

W> φ + X (2)

Here, as shown in FIG. 8, the droplet diameter φ of the organic semiconductor ink 16a by the ink jet method is a diameter when the ink droplet is assumed to be an ideal spherical shape, and the ink droplet weight measurement and The diameter φ of the ink droplet of the organic semiconductor ink 16a is calculated from the volume of the droplet obtained from the specific gravity of the solvent. In general, the droplet diameter φ in the ink jet method has a correlation with the droplet discharge speed, and tends to increase as the discharge speed increases. The ejection speed correlates with the driving voltage of the piezo in the inkjet head, and the ejection speed tends to increase as the driving voltage increases.

  Further, the ink jet landing position error width X is obtained by subtracting the landing diameter b of one ink droplet from the line width a when a line perpendicular to the scanning direction of the ink jet head is drawn as shown in FIG. Value. That is, as shown in FIG. 9A, if the landing position error is ideally zero (the landing position error is 0), the line width a is equal to the landing diameter b of one ink droplet. However, in reality, since the discharge angle of the liquid droplets varies depending on the nozzle, a landing position error occurs as shown in FIG. For such landing position error X, a value indicated in the apparatus specification or the like may be used. The landing position error X is influenced by the mechanical accuracy inherent to the head and the ink physical properties, but depends on the distance between the ejection surface of the inkjet head and the substrate 11 and becomes larger as the head is moved away from the printing surface. This is because the influence of the deviation of the ejection angle increases as the distance from the ejection surface increases. Ideally, the closer the distance is, the smaller the variation is. However, since there is a risk that the substrate 11 and the ejection surface of the head come into contact, about 0.3 to 1 mm is preferable.

  The expansion and contraction of the substrate 11 is caused by the influence of temperature, humidity, and the like, and the influence of annealing in the process of forming the source electrode 14 and the drain electrode 15. The error Y due to the expansion and contraction of the substrate 11 is calculated by the following procedure as shown in FIG. When the source electrode 14 and the drain electrode 15 are formed, marks 21 are provided around the organic semiconductor layer forming region 20 on the substrate 11 in the scanning direction and the vertical direction of the inkjet head, and the lengths C1 and D1 are perpendicular to each other. Measure. C1 and D1 are longer than the length in the head scanning direction and the vertical direction of the region where the organic semiconductor layer is printed. Next, when the organic semiconductor layer is formed, the lengths C2 and D2 between the marks 21 are measured and calculated by taking the difference between the respective amounts of change. That is, the difference ΔC = C1−C2 and the difference ΔD = D1−D2 are calculated. Of the differences ΔC and ΔD calculated in this way, a value obtained by dividing the larger absolute value by 2 is defined as an error Y due to substrate expansion / contraction.

  According to the present embodiment, when the ink droplet is ejected aiming at the center of the channel region, the ink droplets always land inside the edge of the channel width W, so that the edge effect as shown in FIG. 7 does not occur. . Therefore, the organic semiconductor ink 16a can be held in the channel region with a high yield, and the organic semiconductor layer 16 can be stably formed in the channel portion. One ink droplet may be used, and when it is insufficient, a plurality of channel portions may be dropped near the center. In addition, the contact effect of the organic semiconductor ink in the source electrode 14 and drain electrode 15 and the gate insulating film 13 is not adjusted to be equal, but the source electrode 14 and the drain electrode 15 are made higher so that the processing effect by the SAM treatment is achieved. In this respect, the organic semiconductor layer 16 can be stably formed in the channel portion. At this time, the difference in contact angle between the surface of the source electrode 14 and the drain electrode 15 and the surface of the gate insulating film 13 is preferably larger than 5 degrees, and more preferably larger than 10 degrees. If the difference in contact angle is less than 5 degrees, the influence of variations in the SAM process cannot be ignored, and it becomes difficult to perform stable patterning.

  Based on the above, a method for manufacturing an organic thin film transistor according to the present embodiment will be described with reference to FIGS.

  First, in step 102 (S102), the gate electrode 12 is formed in a predetermined region on the substrate 11.

  Next, in step 104 (S104), the gate insulating film 13 is formed on the gate electrode 12.

  Next, in step 106 (S106), the source electrode 14 and the drain electrode 15 are formed in a predetermined region on the gate insulating film 13.

  Next, in step 108 (S108), electrode processing is performed on the surfaces of the formed source electrode 14 and drain electrode 15. Specifically, as described above, the contact angle of the organic semiconductor ink on the surfaces of the source electrode 14 and the drain electrode 15 is gated by treating the surfaces of the source electrode 14 and the drain electrode 15 with a self-assembled monolayer. The contact angle of the organic semiconductor ink in the insulating film 13 is set higher.

  Next, in step 110 (S110), the organic semiconductor layer 16 is formed in a predetermined region between the source electrode 14 and the drain electrode 15. Specifically, using the organic semiconductor ink 16a, as described above, the organic semiconductor ink 16a is supplied under the condition satisfying the expression shown in (1) and the condition satisfying the expression shown in (2), and the organic semiconductor layer 16 Form.

  Thereby, the organic thin-film transistor in this Embodiment can be produced.

In the present embodiment, the organic semiconductor layer 16 is formed by using an organic semiconductor ink obtained by dissolving an organic semiconductor material in an organic solvent and dropping and printing the organic semiconductor ink by an inkjet method. As the organic semiconductor material, all organic semiconductor materials and organic semiconductor precursor materials that are soluble in an organic solvent can be used, and although not particularly limited, a polymer material, an oligomer material, a low molecular material, or the like is used. Organic precursors such as pentacene, anthracene, tetracene, phthalocyanine, or one or more hydrocarbon aromatic rings and aromatic heterocycles, compounds in which these are condensed, and porphyrin and pentacene precursors Body material; polyacetylene conductive polymer; polyphenylene conductive polymer such as polyparaphenylene and derivatives thereof, polyphenylene vinylene and derivatives thereof; heterocyclic systems such as polypyrrole and derivatives thereof, polythiophene and derivatives thereof, polyfuran and derivatives thereof, etc. Conductive polymer; polyaniline and its derivatives And ionic conductive polymers such as body. As a polymer material having a triarylamine skeleton, a material represented by the following chemical formula 1 can be used. This material is a non-orientated polymer material, and its characteristic variation is very small regardless of the film formation shape and method.

If the surface tension or viscosity of the organic semiconductor ink is not suitable, ejection may be impossible or ejection may be difficult, and it may be difficult to form round droplets, and the ligament may be long. For this reason, the organic semiconductor ink preferably has a surface tension of 20 to 40 mN / m, and more preferably 25 to 35 mN / m. The viscosity is preferably 1 to 20 mPa · sec, and more preferably 2 to 15 mPa · sec. Further, when the organic semiconductor ink is ejected, it is necessary to have a drying property that does not cause the solvent to evaporate and the organic semiconductor material is solidified.

  Moreover, as a material which comprises the gate insulating film 13, a silicon oxide film etc. are mentioned with an inorganic material. Examples of the organic material include polyimide; polyvinylphenol; polyester; acrylic resins such as polyacrylonitrile and polymethyl methacrylate; epoxy resins; and polymer materials such as thermosetting resins.

  The source electrode 14, the drain electrode 15 and the gate electrode 12 can be formed in a predetermined shape by patterning a photoresist by a photolithography process and vacuum deposition of an electrode material. Although it does not specifically limit as electrode material, Au, Ag, Cu, Pt, Pd, Ni, Cr etc. which are metal materials are mentioned, What mixed 2 or more types of metal materials or an alloy may be used. In particular, Au, Ag, Cu, and Ni are particularly preferable because they have low electrical resistance, high thermal conductivity, and low corrosivity.

  In addition, at least one of the source electrode 14 and the drain electrode 15 or the gate electrode 12 can be formed by a printing method such as an inkjet method or a dispenser method. At this time, it is preferable to use a metal ink containing metal particles or a metal complex. Examples of the metal particles include, but are not limited to, Au, Ag, Cu, Pt, Pd, Ni, Ir, Rh, Co, Fe, Mn, Cr, Zn, Mo, W, Ru, In, and Sn. An alloy obtained by mixing two or more materials may be used. In particular, Au, Ag, Cu, and Ni are particularly preferable because they have low electrical resistance, high thermal conductivity, and low corrosivity. In this case, it is known that the metal particles have an average particle diameter of about several nanometers to several tens of nanometers and are sintered at a significantly lower temperature when uniformly dispersed in the solvent. This is because the influence of highly active surface atoms increases as the particle size of the metal particles decreases. Although it does not specifically limit as a metal complex, The complex etc. which have Au, Pt, Ag, Cu, Pd, In, Cr, Ni etc. as a center metal are mentioned. The gate electrode 12, the source electrode 14, and the drain electrode 15 can be formed by sintering after forming a pattern using such a metal ink.

  In addition, when the surface tension and viscosity of the metal ink are not suitable, ejection becomes impossible or ejection failure occurs, it is difficult to form round droplets, and ligaments may be lengthened. For this reason, the metal ink has a surface tension of about 30 mN / m and a viscosity of preferably 2 to 13 mPa · sec, more preferably 7 to 10 mPa · sec. In addition, when discharging the metal ink, it is necessary to have a drying property that does not cause the solvent to volatilize and the metal particles or the metal complex to solidify.

[Second Embodiment]
Next, a second embodiment will be described. The present embodiment is an organic thin film transistor array (organic thin film transistor substrate) and a display device using the organic thin film transistor array.

  FIG. 12 shows an organic thin film transistor array 100 in the present embodiment. In the organic thin film transistor array 100 according to the present embodiment, a plurality of organic thin film transistor elements are formed on a substrate.

  A method for manufacturing the organic thin film transistor array 100 will be described with reference to FIGS.

  First, in step 202 (S202), a photoresist is applied to a substrate 111 such as a glass substrate or a film substrate, and a resist pattern is formed by performing pattern exposure and development using a shadow mask. Thereafter, an adhesion layer (not shown) made of Cr having a thickness of 3 nm and Au having a thickness of 50 nm are formed by vacuum deposition. Thereafter, the gate electrode 112 serving as a scanning wiring is formed by immersing in a solvent that dissolves the photoresist and selectively removing the resist pattern, the adhesion layer formed on the resist pattern, and Au.

  Next, in step 204 (S204), a gate insulating film 113 and a polyimide insulating film serving as an interlayer insulating film of the scanning wiring / signal wiring are formed on the gate electrode 112 by spin coating.

  Next, in step 206 (S206), the source electrode 114 and the drain electrode 115 are formed. Specifically, an adhesion layer (not shown) made of Cr with a thickness of 3 nm and a source electrode 114 and a drain electrode 115 made of Au with a thickness of 50 nm are formed on the gate insulating film 113 in the same procedure as the gate electrode 112. To do.

  Next, in step 208 (S208), electrode processing is performed on the surfaces of the source electrode 114 and the drain electrode 115. Specifically, the substrate 111 is immersed for about 10 minutes in ink in which alkanethiol, which is a SAM material, is dissolved in ethanol, and the surface of the source electrode 114 and the drain electrode 115 is treated.

  Next, in Step 210 (S210), an organic semiconductor ink obtained by dissolving the material shown in Chemical Formula 1 in an organic solvent is formed on the gate insulating film 113 on which the source electrode 114 and the drain electrode 115 are formed by an inkjet method. Printing is performed to form the organic semiconductor layer 116 in the channel region. Further, a paraxylylene film having a thickness of 2000 nm was formed on the uppermost layer by a CVD method to form a protective layer (not shown). Through the above steps, the organic thin film transistor array 100 in the present embodiment can be manufactured.

  Thereafter, in step 212 (S212), a display device can be formed by forming a display element on the organic thin film transistor array 100 as described later.

  Note that the gate electrode 112, the source electrode 114, and the drain electrode 115 may be formed by patterning using an Ag ink or the like by an inkjet method or the like.

  The organic thin film transistor array 100 manufactured as described above can be used for various display devices by combining with various display elements.

  For example, as shown in FIG. 14, an interlayer insulating film 117 is formed on the organic thin film transistor array 100 shown in FIG. 12, and the interlayer insulating film 117 is opened until the surface of the drain electrode 115 in each organic semiconductor transistor is exposed. The pixel electrode 118 connected to the drain electrode 115 is formed through the formed opening. On the other hand, an ITO (Indium Tin Oxide) film 122 having a thickness of about 100 nm is formed on a counter substrate 121 made of glass or the like by sputtering, a polyimide resin is applied thereon by a spin coating method, and rubbed to align the alignment film 123. Is formed with a thickness of about 200 nm. After the alignment treatment, the organic thin film transistor array 100 and the counter substrate 121 are joined via a silica spacer (not shown). Specifically, in the organic thin film transistor array 100, the surface on which the pixel electrode 118 is formed and the surface on which the alignment film 123 of the counter substrate 121 is formed are bonded via a silica spacer (not shown). . A gap is formed by the organic thin film transistor array 100 and the counter substrate 121 bonded in this manner, and a liquid crystal layer 130 is formed by enclosing a liquid crystalline material between the gap, and the liquid crystal to be the display device in this embodiment mode. Panel 140 can be fabricated.

  Furthermore, as a display device having another configuration in the present embodiment, as shown in FIG. 15, an ITO film 152 is formed on the counter substrate 151, and the surface on which the drain electrode 115 of the organic thin film transistor array 100 is formed. It is made to oppose and it joins through a silica spacer. A gap is formed by the organic thin film transistor array 100 and the counter substrate 151 bonded in this way, and a microcapsule type electrophoretic element is sealed between the caps to form an electrophoretic layer 160. Thus, an electrophoretic display panel which is a display element can be manufactured. Note that the microcapsule type electrophoretic element forming the electrophoretic layer 160 is formed of titanium oxide 161, carbon black 162, and urethane resin 163.

  Further, an organic EL panel can be manufactured by forming an organic EL element as a display pixel in this embodiment and disposing an air shielding shield.

(Comparative Example 1)
A photoresist was applied to a glass substrate, and after pattern exposure using a shadow mask and development, an adhesion layer (not shown) made of Cr with a thickness of 3 nm and Au with a thickness of 50 nm were formed by vacuum deposition. Then, the gate electrode was patterned by immersing in a solvent for dissolving the resist and selectively removing the resist and the electrode on the resist. Next, Rika Coat SN-20 (manufactured by Shin Nippon Rika Co., Ltd.) of a polyimide solution was applied by a spin coating method, pre-baked, and then baked at 200 ° C. to form a gate insulating film having a thickness of 500 nm. Next, the source and drain electrodes were patterned in the same procedure as the gate electrode. The channel width W was 50 μm and the channel length L was 5 μm.

  Next, on the gate insulating film on which the source electrode and the drain electrode are formed, printing is performed by an ink jet method using an ink in which the material shown in Chemical Formula 1 is dissolved in tetralin which is a high boiling point solvent, and the ink droplets are deposited. The behavior of the drops was observed.

  Further, the piezo driving conditions of the ink jet head at this time are piezo driving conditions 1 shown in FIG. 20 described later, the droplet volume is about 7.2 pL, and the droplet diameter φ is about 25.8 μm. .

  Further, when the distance between the inkjet head and the substrate at this time was set to about 0.5 mm and the landing position error X was measured from the printing line width and the ink landing diameter by the method shown in FIG. 9, it was about 30 μm. It was.

  Further, when the error Y due to the contraction of the substrate at this time was evaluated by the method shown in FIG. 10, it was almost zero.

  Moreover, the contact angle of the organic semiconductor ink with respect to the Au electrode surface used as a source electrode and a drain electrode at this time was evaluated. As a result, the ink spread completely and could not be evaluated.

  Moreover, the contact angle of the organic semiconductor ink with respect to the polyimide insulating film surface at this time was about 10 degrees.

  In Comparative Example 1, the result of observing the temporal change when supplying ink is shown in FIG. That is, as shown in the order of FIGS. 16A, 16B, 16C, and 16D, the ink moves onto the electrode after the droplet is deposited, and cannot be formed on the channel. This is because the contact angle of the organic semiconductor on the electrode surface is lower and the ink spreads toward the electrode.

(Comparative Example 2)
After forming the source and drain electrodes in the same manner as in Comparative Example 1, the substrate was immersed in a liquid in which perfluorodecanethiol was dissolved in EtOH at 10 mM for about 10 minutes, then washed with EtOH and blown with a nitrogen gun. A SAM treatment process was performed on the electrode surface. Next, the organic semiconductor layer was printed by the inkjet method under the same conditions as in Comparative Example 1, and the behavior of ink droplet landing was directly observed.

  Moreover, as a result of evaluating the contact angle of the organic semiconductor ink with respect to the surface of the Au electrode serving as the source electrode and the drain electrode subjected to the SAM treatment at this time, it was about 80 degrees.

  Moreover, the contact angle of the organic semiconductor ink with respect to the polyimide insulating film surface at this time was about 10 degrees.

  In Comparative Example 2, the result of observing the temporal change when ink is supplied is shown in FIG. That is, as shown in the order of FIGS. 17A, 17B, 17C, and 17D, the ink moves onto the gate insulating film outside the channel region after being deposited, and is formed on the channel. I couldn't. Since the contact angle of the organic semiconductor ink with respect to the electrode surface is higher than the contact angle with respect to the surface of the gate insulating film due to the SAM treatment, and since the liquid droplets protruded at the edge portion at the time of landing, the ink spreads onto the gate insulating film. This is because it has stopped.

Example 1
A transistor was fabricated in the same manner as in Comparative Example 2 except that the channel width W was 100 μm. FIG. 18 shows a result of observing a temporal change when ink is supplied in Example 1. That is, as shown in the order of FIGS. 18A and 18B, the ink was stably held in the channel, and an organic semiconductor layer could be formed in the channel portion. This is because the droplet is stably held in the channel region by setting the channel width W larger than the droplet diameter φ, the landing position variation X, and the total Y of the substrate expansion and contraction.

(Comparative Example 3)
A transistor array in which a plurality of organic thin film transistors are arranged was produced in the same manner as in Comparative Example 2. A channel width W = 50 μm was prepared. After the organic semiconductor layer was printed by the inkjet method, the formation of the organic semiconductor layer on the channel portion was observed at 500 or more locations in the surface, and the printing result of the channel region was evaluated. Here, it was judged that the organic semiconductor layer was formed in the channel region, and the organic semiconductor layer was not formed in the channel region was impossible.

  As a result, when the channel width W = 50 μm, there are many cases where a channel cannot be formed, and the yield is 70% or less.

(Example 2)
A transistor array in which a plurality of organic thin film transistors are arranged was produced in the same manner as in Comparative Example 3. However, channel widths of W = 60, 70, 80, 90, and 100 μm were prepared. After the organic semiconductor layer was printed by the inkjet method, the formation of the organic semiconductor layer on the channel portion was observed at 500 or more locations in the surface, and the possibility of channel formation was evaluated. As a result, the channel formation yield was greatly improved to about 95% when the channel width W was 60 μm or more.

  A graph summarizing the results of Comparative Example 3 and Example 2 is shown in FIG. It can be seen that the yield is greatly improved with W = 60 μm as a threshold. The sum of the inkjet droplet φ, the landing position error X, and the error Y due to substrate shrinkage is about 55.8 μm, and by setting the channel width to 60 μm or more, the organic semiconductor layer can be stably formed in the channel region. all right.

(Comparative Example 4)
A transistor array in which a plurality of organic thin film transistors are arranged was produced in the same manner as in Comparative Example 2. However, the distance between the inkjet head and the substrate during printing of the organic semiconductor layer was set to 0.8 mm. At this time, when the landing position error X was measured by the method shown in FIG. 7, it was about 46 μm. As a result, the sum of the droplet diameter φ, the landing position error X, and the error Y due to substrate contraction was about 71.8 μm. Those having channel widths W = 50, 60, and 70 μm were prepared.

  After the organic semiconductor layer was printed by the inkjet method, the formation of the organic semiconductor layer on the channel portion was observed at 500 or more locations in the surface, and the possibility of channel formation was evaluated. As a result, the channel formation yield was 75% or less.

(Example 3)
A transistor array in which a plurality of organic thin film transistors are arranged was manufactured in the same manner as in Comparative Example 4. However, those with channel widths W = 80, 90, and 100 μm were prepared.

  After the organic semiconductor layer was printed by the inkjet method, the formation of the organic semiconductor layer on the channel portion was observed at 500 or more locations in the surface, and the possibility of channel formation was evaluated. As a result, the channel formation yield was 95% or more.

(Comparative Example 5)
A transistor array in which a plurality of organic thin film transistors are arranged was produced in the same manner as in Comparative Example 2. However, the piezo drive conditions of the inkjet head at this time are piezo drive conditions 2 shown in FIG. 20 described later, the droplet volume is about 15.8 pL, and the droplet diameter φ is about 33.5 μm. . As a result, the sum of the droplet diameter φ, the landing position error X, and the error Y due to substrate contraction was about 63.5 μm. Those having channel widths W = 50 and 60 μm were prepared.

  After the organic semiconductor layer was printed by the inkjet method, the formation of the organic semiconductor layer on the channel portion was observed at 500 or more locations in the surface, and the possibility of channel formation was evaluated. As a result, the channel formation yield was 75% or less.

(Example 4)
A transistor array in which a plurality of organic thin film transistors are arranged was manufactured in the same manner as in Comparative Example 5. However, those with channel widths W = 70, 80, 90, and 100 μm were prepared.

  After the organic semiconductor layer was printed by the inkjet method, the formation of the organic semiconductor layer on the channel portion was observed at 500 or more locations in the surface, and the possibility of channel formation was evaluated. As a result, the channel formation yield was 95% or more.

(Comparative Example 6)
An adhesion layer (not shown) made of Cr with a thickness of 3 nm and a gate electrode made of Al with a thickness of 100 nm were formed on the film substrate by a vacuum deposition method using a shadow mask. Next, Rika Coat SN-20 (manufactured by Shin Nippon Rika Co., Ltd.), which is a polyimide solution, was applied by spin coating, prebaked, and then baked at 200 ° C. to form a gate insulating film having a thickness of 500 nm. After the gate insulating film was formed, a transistor array in which a plurality of organic thin film transistors were arranged was manufactured by the same method as in Comparative Example 2. The error Y due to the substrate contraction at this time was evaluated by the method shown in FIG. 10 and found to be 20.7 μm. As a result, the sum of the droplet diameter φ, the landing position error X, and the error Y due to substrate contraction was about 76.5 μm. Those having channel widths W = 50, 60, and 70 μm were prepared.

  After the organic semiconductor layer was printed by the inkjet method, the formation of the organic semiconductor layer on the channel portion was observed at 500 or more locations in the surface, and the possibility of channel formation was evaluated. As a result, the channel formation yield was 70% or less.

(Example 5)
A transistor array in which a plurality of organic thin film transistors are arranged was manufactured in the same manner as in Comparative Example 6. However, the ones with channel widths W = 80, 90, and 100 μm were prepared.

  After the organic semiconductor layer was printed by the inkjet method, the formation of the organic semiconductor layer on the channel portion was observed at 500 or more locations in the surface, and the possibility of channel formation was evaluated. As a result, the channel formation yield was 95% or more.

  Including the results of Comparative Examples 3-6 and Examples 2-5, droplet diameter φ = 25.8 μm or 33.5 μm, landing position error X = 30 μm or 46 μm, error Y = 0 or 20.7 μm due to substrate shrinkage FIG. 20 shows a list of results obtained by evaluating the yield of whether or not the organic semiconductor layer can be formed when the channel width W is 50, 60, 70, 80, 90, and 100 μm under the conditions. In the channel formation yield, 95% or more was judged as ◯, and less than 95% was judged as ×.

  Accordingly, when the contact angle of the organic semiconductor ink is higher on the electrode surface than on the insulating film surface, the channel width W is larger than the sum of the inkjet droplet φ, the landing position error X, and the error Y due to substrate contraction. It was found that the organic semiconductor layer can be stably formed in the channel region.

(Example 6)
The active matrix display device shown in FIG. 15 was manufactured using the organic thin film transistor array having a channel width W = 60 μm manufactured in Example 2. Specifically, a microcapsule containing isopar colored with titanium oxide particles and oil blue and a coating solution in which a polyvinyl alcohol aqueous solution is mixed are applied on a transparent electrode made of ITO provided on a polycarbonate substrate, A layer composed of microcapsules and a binder was formed. The obtained substrate and the organic thin film transistor array of Example 2 were bonded via a binder so that the glass substrate and the polycarbonate substrate were the outermost surfaces.

  The driver IC for scanning signal is connected to the bus line connected to the gate electrode of the obtained active matrix display device, and the driver IC for data signal is connected to the bus line connected to the source electrode, and the image is switched every 0.5 seconds. As a result, it was possible to display a good still image.

  As mentioned above, although the form which concerns on implementation of this invention was demonstrated, the said content does not limit the content of invention.

11 substrate 12 gate electrode 13 gate insulating film 14 source electrode 15 drain electrode 16 organic semiconductor layer 16a organic semiconductor ink 100 organic thin film transistor array 111 substrate 112 gate electrode 113 gate insulating film 114 source electrode 115 drain electrode 116 organic semiconductor layer 117 interlayer insulating film 118 Pixel electrode 121 Counter substrate 122 ITO film 123 Alignment film 130 Liquid crystal layer 140 Liquid crystal panel

JP-A-2005-310962 JP 2004-297011 A Special table 2003-536260 gazette JP 2007-36259 A

K. Suzuki, IDW08 FLX2-3L D. Boudinet, Journal of Applied Physics, 105, 084510, (2009)

Claims (8)

An electrode forming step of forming a source electrode and a drain electrode on a substrate or an insulating film on the substrate;
An electrode processing step of making a contact angle of the organic semiconductor ink on the source electrode and the drain electrode higher than a contact angle on the substrate or the insulating film when the organic semiconductor ink is supplied;
A semiconductor layer forming step of forming an organic semiconductor layer by supplying the organic semiconductor ink between the formed source electrode and the drain electrode;
Have
The channel width of the channel formed by the source electrode and the drain electrode is W, the droplet diameter of the droplet when the organic semiconductor ink is supplied is φ, and the error of the position where the droplet is supplied If the landing position error width is X,
W> φ + X
The organic thin-film transistor manufacturing method characterized by satisfy | filling. When the error due to the expansion and contraction of the substrate is Y,
W> φ + X + Y
The organic thin film transistor manufacturing method according to claim 1, wherein:   3. The method of manufacturing an organic thin film transistor according to claim 1, wherein in the semiconductor layer forming step, the organic semiconductor ink is supplied by an inkjet method.   4. The method of manufacturing an organic thin film transistor according to claim 1, wherein the source electrode and the drain electrode are modified with a self-assembled monolayer.   5. The method of manufacturing an organic thin film transistor according to claim 4, wherein the self-assembled monolayer includes alkanethiol. Before the electrode forming step,
Forming a gate electrode on the substrate; and
A gate insulating film forming step of forming a gate insulating film on the gate electrode;
6. The method of manufacturing an organic thin film transistor according to claim 1, wherein the source electrode and the drain electrode in the electrode forming step are formed on the gate insulating film. A method for producing an organic thin film transistor array having a plurality of organic thin film transistors,
The method for manufacturing an organic thin film transistor array, wherein the organic thin film transistor is an organic thin film transistor manufactured by the method for manufacturing an organic thin film transistor according to any one of claims 1 to 6.   A method for manufacturing a display device, comprising a step of forming a display element on an organic thin film transistor array manufactured by the method for manufacturing an organic thin film transistor array according to claim 7.