JP2008066439A - Method of manufacturing organic thin film transistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an organic thin film transistor which has a sufficient carrier mobility and is easily manufactured with less variations. <P>SOLUTION: This method comprises a step of preparing a second member where a first member includes a photothermal conversion layer having a thermal bonding strength to an organic semiconductor layer is smaller than a thermal bonding strength to the first substrate, and an amorphous-state organic semiconductor having a property of being crystallized when heated and melted or sublimated and a second member includes an organic semiconductor layer which connects at least source and drain electrodes provided to a second substrate and which is crystallized and formed when melted or sublimated and which has a bonding strength larger than the bonding strength between the organic semiconductor layer and the photothermal conversion layer; a step of stacking the first and second members; a step of irradiating light to the photothermal conversion layer; a step of separating the first member from the second member. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an organic thin film transistor.

  In recent years, research and development of organic TFT elements using organic semiconductor materials has been actively promoted as a technique for compensating for the disadvantages of conventional Si-based thin film transistor (TFT) elements (see Patent Document 1 and Non-Patent Document 1). The disadvantage of the Si-based thin film transistor (TFT) element is that it requires a large-scale apparatus and complicated processes such as vacuum film formation, high-temperature processing, and a photolithography process.

  In addition, the organic TFT element can be manufactured by a low-temperature process such as coating / printing of an organic semiconductor layer, so that a light, hard-to-break resin substrate can be used, and a flexible display using a resin film as a support. It is said that it is realizable (refer nonpatent literature 2).

As a method for manufacturing an organic light emitting display device by transfer, which is one of low temperature processes, there is the following method (see Patent Document 2). An arrayed first electrode is provided on a display substrate, and a non-patterned donor transfer substrate, a laser light absorbing layer on the donor transfer substrate, and an organic light emitting layer thereon are prepared. Next, the donor transfer substrate is disposed so as to have a transfer relationship with respect to the display substrate having the arrayed first electrode pattern. Next, a specific portion of the organic light emitting layer from the donor substrate is electrically connected to the first electrode by focusing and scanning the laser beam on the laser light absorbing layer on the donor substrate. Transfer to the designated area corresponding to the pixel. A second electrode is provided on the transferred organic light emitting portion on the display substrate.
Japanese Patent Laid-Open No. 10-190001 JP 2002-110350 A Advanced Material 2002 2002 No. 2 page 99 (Review) SID'02 Digest p57

  However, according to Patent Document 1 and Non-Patent Documents 1 and 2, a thin film transistor is formed by disposing an organic semiconductor material on a substrate using a wet process such as printing or coating. There is.

  For example, various materials are used for the gate insulating film and the source / drain electrodes constituting the thin film transistor. It is necessary to form an organic semiconductor layer on these various dissimilar materials. For this reason, the arrangement of semiconductor materials is disturbed due to the difference in the surface state and shape such as the interface between different materials, steps, and surface roughness. When the arrangement is disturbed, there is a problem that sufficient carrier mobility cannot be obtained, or the characteristics of the thin film transistors arranged in an array are varied, so that a device cannot be manufactured stably.

  The method for producing an organic light emitting display device described in Patent Document 2 sublimates the organic light emitting layer formed on the donor transfer substrate and transfers it to the display substrate. From the material and the production method of the organic light emitting layer, It is assumed that the semiconductor material of the organic light emitting layer on the donor transfer substrate in an amorphous state is also in an amorphous state on the transferred display substrate. In this case, the transfer process is not sufficiently transferred to a desired position, and the material of the organic light-emitting layer that is the transfer material remains on the donor transfer substrate side, so that a good organic light-emitting layer cannot be formed. There is.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method for manufacturing an organic thin film transistor that has sufficient carrier mobility, has little variation, and is easy to manufacture. is there.

  Said subject is solved by the following structures.

1. Production of an organic thin film transistor having an insulating film between at least a source electrode, a drain electrode, an organic semiconductor layer connecting the source electrode and the drain electrode, a gate electrode, and the organic semiconductor layer and the gate electrode on a substrate In the method
It has the property of being melted or sublimated and crystallized by being heated with a photothermal conversion layer that is heated on the first substrate so that the adhesive force to the organic semiconductor layer becomes smaller than the adhesive force to the first substrate. A first member having a layer containing an amorphous organic semiconductor in this order, and at least the source electrode and the drain electrode as the uppermost layer of the second substrate, and the source electrode and the drain electrode The adhesive force between the surface on which the organic semiconductor layer to be connected is formed and the organic semiconductor layer formed by melting or sublimation and crystallization is larger than the adhesive force between the organic semiconductor layer and the photothermal conversion layer to be heated. Preparing a second member having the following properties:
Stacking the first member and the second member in a direction in which the layer containing the organic semiconductor of the first member and the source electrode and the drain electrode of the second member face each other;
In order to form the organic semiconductor layer that connects the source electrode and the drain electrode, the photothermal conversion layer is irradiated with light from the first substrate side so that the organic semiconductor is heated until it melts or sublimates. And a process of
The method of manufacturing an organic thin film transistor, wherein the step of separating the first member and the second member is performed in this order.

  2. After the step of irradiating the light between the light-to-heat conversion layer and the layer containing the organic semiconductor, the first member has an adhesive force with respect to the organic semiconductor layer and an adhesive force with respect to the light-to-heat conversion layer. 2. The method for producing an organic thin film transistor according to 1, wherein the organic thin film transistor has a separation layer smaller than the adhesive force between the substrate and the photothermal conversion layer.

  3. 3. The method of manufacturing an organic thin film transistor according to 1 or 2, wherein the light irradiation step exposes the photothermal conversion layer by mask exposure.

  4). 3. The step of irradiating the light comprises concentrating laser light on the photothermal conversion layer to form a light spot, and scanning the light spot to expose the photothermal conversion layer. Manufacturing method of organic thin film transistor.

  5. 5. The method for producing an organic thin film transistor according to claim 1, wherein the organic semiconductor layer is a π-conjugated polymer or an oligomer in which an alkyl group possessed forms an array structure.

  6). The method for producing an organic thin film transistor according to any one of claims 1 to 4, wherein the organic semiconductor layer is an acene compound.

  7). The method of manufacturing an organic thin film transistor according to any one of claims 1 to 6, wherein the first substrate is smaller than the second substrate.

  8). An alignment mark is provided on the second substrate, and the first substrate and the second substrate do not overlap at the position of the alignment mark when the first substrate and the second substrate are overlapped. The method for producing an organic thin film transistor according to any one of 1 to 7, which is characterized in that

  9. The organic thin film transistor according to any one of claims 1 to 8, further comprising a step of detaching the remaining layer containing the organic semiconductor by immersing the first member in a solvent after the separating step. Manufacturing method.

  According to the present invention, a first member having a photothermal conversion layer and a layer containing an organic semiconductor in an amorphous state and a second member having at least the source electrode and the drain electrode provided on the uppermost layer are prepared. In order to form an organic semiconductor layer that connects the source electrode and the drain electrode by overlapping the first member and the second member in a direction in which the source electrode and the drain electrode of the second member are opposed to each other, After irradiating the photothermal conversion layer with light from the first substrate side so that the semiconductor is heated until it is melted or sublimated, the first member and the second member are separated.

  The adhesive force to the organic semiconductor layer of the photothermal conversion layer irradiated with light from the side of the first substrate so as to be heated until the organic semiconductor is melted or sublimated is smaller than the adhesive force to the first substrate. Also, the adhesive force between the melted or sublimated crystallized organic semiconductor layer and the surface on which the organic semiconductor layer that connects the source electrode and the drain electrode of the second substrate is formed is the difference between the organic semiconductor layer and the photothermal conversion layer. Greater than adhesive strength. Further, the layer containing an amorphous organic semiconductor is heated and melted or sublimated to crystallize to form an organic semiconductor layer.

  Thus, when the first member and the second member are separated, the layer containing the amorphous organic semiconductor of the first member is crystallized to form a crystallized organic semiconductor layer that connects the source electrode and the drain electrode of the second member. The organic semiconductor layer can be separated from the photothermal conversion layer of the first member. An organic semiconductor layer crystallized from a layer containing an amorphous organic semiconductor on the first substrate has characteristics that have no carrier variation and good carrier mobility.

  Therefore, it is possible to provide a method for manufacturing an organic thin film transistor that has sufficient carrier mobility, has little variation, and is easy to manufacture.

  Although the present invention will be described based on the illustrated embodiment, the present invention is not limited to the embodiment.

  FIG. 1 shows an example of the structure of a bottom gate type organic thin film transistor (organic TFT). The second substrate 30 is composed of a gate electrode 2, an insulating film 3, a source electrode 4s, a drain electrode 4d, and an organic semiconductor film 5a. In the organic TFT 10, the gate electrode 2 is provided on the second substrate 30, and the insulating film 3 is provided so as to cover the gate electrode 2. On the insulating film 3, a source electrode 4 s and a drain electrode 4 d are provided by providing a space serving as a channel formation portion made of an organic semiconductor. These are connected by providing an organic semiconductor film 5a in a region that sufficiently fills a channel forming portion, which is a space between the source electrode 4s and the drain electrode 4d. For example, a transparent pixel electrode made of ITO or the like is provided on the drain electrode 4d of the organic TFT 10, and a display device (not shown) including an organic TFT array in which the pixel electrode is arranged in a matrix can be obtained.

  A manufacturing process flow for manufacturing the organic TFT of FIG. 1 is shown in FIG. Moreover, the example of the manufacturing process of organic TFT is shown to FIG. The same reference numerals in the drawings denote the same components and those having the same functions. Hereinafter, the manufacturing of the organic TFT will be described with reference to FIGS.

(First substrate and second substrate)
As shown in FIG. 3 or 4, a light-to-heat conversion layer 22 described later and a layer containing an organic semiconductor in an amorphous state (hereinafter also referred to as a layer containing an organic semiconductor) 5 are provided on the first substrate 20. Moreover, it is preferable to provide the below-mentioned isolation | separation layer (not shown) between the photothermal conversion layer 22 and the layer 5 containing an organic semiconductor. On the second substrate 30, there are a gate electrode 2, source and drain electrodes 4 s and 4 d, which will be described later, and an insulating film 3.

  The material of the 1st board | substrate 20 and the 2nd board | substrate 30 is comprised with glass or a flexible resin sheet, for example, a plastic film can be used as a sheet | seat. Examples of plastic films include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), and cellulose. Examples include films made of triacetate (TAC), cellulose acetate propionate (CAP), and the like.

  By using the flexible plastic film as described above as the material of the first substrate 20, it is possible to store it in a roll shape and to input a process, thereby improving the production efficiency. In addition, by using a flexible plastic substrate as the first substrate 20 and making the organic semiconductor disposed on the first substrate 20 amorphous, it is possible to store and process in a roll shape, thereby improving production efficiency. It can be improved. This is because the organic semiconductor in a crystalline state generally has low resistance to bending stress, whereas the organic semiconductor in an amorphous state is strong against bending stress.

  Further, by using the plastic film as described above as the second substrate 30, the weight can be reduced as compared with the case of using a glass substrate, the portability can be improved, and the resistance to impact can be improved. . However, it is desirable for the stability of the substrate material that the glass transition point of the substrate material is equal to or higher than the melting point of the organic semiconductor material described later.

  The first substrate 20 is preferably smaller than the second substrate 30. Generally, when configuring a TFT array, the wiring part other than the TFT array part often has a mounting part with an external circuit in the peripheral part of the TFT array part, and it is not necessary to form an organic semiconductor layer in this part. There are many. Therefore, the first substrate including the layer containing the organic semiconductor can be made smaller than the second substrate 30. By making the first substrate 20 small, the amount of organic semiconductor that is an expensive material can be reduced, so that the cost can be reduced.

  The second substrate 30 is preferably provided with an alignment mark. This is because in the step of irradiating light, which will be described later, this is effective for determining the position where the second substrate 30 is irradiated with light. In order to confirm the alignment mark, when the first substrate 20 is overlaid on the second substrate 30, it is preferable that the first substrate does not overlap the alignment mark. For this reason, the first substrate is preferably smaller than the second substrate 30.

(Photothermal conversion layer)
The photothermal conversion layer 22 provided on the first substrate 20 will be described. The photothermal change layer 22 is provided to efficiently heat the layer 5 containing an organic semiconductor in an amorphous state, which will be described later, on the photothermal conversion layer 22. The heated layer 5 containing an organic semiconductor is melted or sublimated to form an organic semiconductor layer 5a that connects the source electrode 4s and the drain electrode 4d included in the second substrate 30. The region where the semiconductor layer 5a is actually formed is preferably wider than the channel portion so that the organic semiconductor layer is sufficiently embedded in the channel portion. Moreover, you may have the function of the separation layer mentioned later by selecting the material used for the photothermal conversion layer 22 suitably.

  As a material used for the photothermal conversion layer 22, a well-known near-infrared light absorber can be used. Near infrared light absorbers include, for example, organic compounds such as cyanine, polymethine, azurenium, squalium, thiopyrylium, naphthoquinone, anthraquinone dyes, phthalocyanine, azo, and thioamide organometallic complexes. Preferably used. These materials can be used alone or in combination of two or more. Carbon black and the like are also preferable materials.

  These photothermal conversion agents can be dispersed or dissolved in a resin solution, applied onto the first substrate 20, and dried to form the photothermal conversion layer 22. Or the 1st board | substrate 20 itself provided with the photothermal conversion function can be made by knead | mixing and extending | stretching a photothermal conversion agent in resin, and making it a film.

  Further, the photothermal conversion layer 22 heated until the layer 5 containing an amorphous organic semiconductor is melted or sublimated needs to have an adhesive force with the crystallized organic semiconductor layer 5a smaller than an adhesive force with the first substrate 20. There is. By selecting the materials of the first substrate 20, the layer 5 containing the amorphous organic semiconductor to be crystallized, and the photothermal conversion layer 22 so as to have such an adhesive force relationship, the crystallized organic semiconductor layer 5 a It can be separated from the photothermal conversion layer 22.

  Examples of the method for providing the photothermal conversion layer 22 on the first substrate 20 include dipping, spin coating, knife coating, bar coating, blade coating, squeeze coating, reverse roll coating, gravure roll coating, curtain coating, spray coating, and die coating. A known coating method can be used. Furthermore, a coating method capable of continuous coating or thin film coating is preferably used.

  The light source for irradiating the photothermal conversion layer 22 to generate heat is not particularly limited as long as high illuminance light can be obtained. Examples of the exposure method include a mask exposure method and a scanning exposure method. The mask exposure method is a method in which exposure is performed with a lamp using a mask having an opening, and since a wide area can be exposed at a time, the exposure time can be shortened, which is preferable. Examples of the high-intensity lamp that can perform mask exposure include a xenon lamp, a halogen lamp, and a mercury lamp. The scanning exposure method is a method in which laser light is condensed to form a light spot, and this light spot is scanned for exposure. A laser beam capable of performing scanning exposure is preferable because an exposure apparatus can be configured at low cost because it can easily increase the luminance by reducing the irradiation area to a very small size.

In order to obtain high resolution in exposure with laser light, electromagnetic waves that can narrow the energy application area (that can form a laser spot), particularly ultraviolet rays having a wavelength of 1 nm to 1 mm, visible rays, and infrared rays are preferable. Such laser light sources are generally well-known solid lasers such as ruby laser, YAG laser, and glass laser; He—Ne laser, Ar ion laser, Kr ion laser, CO 2 laser, CO laser, He—Cd. Examples thereof include gas lasers such as lasers, N2 lasers, and excimer lasers; semiconductor lasers such as InGaP lasers, AlGaAs lasers, GaAsP lasers, InGaAs lasers, InAsP lasers, CdSnP2 lasers, and GaSb lasers; chemical lasers and dye lasers. Among these lasers, a semiconductor laser having a wavelength of 700 to 1200 nm is preferable. An infrared laser having an output per laser beam of 20 to 200 mW is most preferably used. The energy density is preferably 50 to 500 mJ / cm ^2, more preferably a 100~200mJ / cm ^2.

(Separation layer)
The separation layer (not shown) provided between the photothermal conversion layer 22 and the layer 5 containing an organic semiconductor on the first substrate 20 of the first member will be described. It is preferable to provide a separation layer between the photothermal conversion layer 22 and the layer 5 containing an organic semiconductor. This separation layer has a property that the adhesive force to the crystallized organic semiconductor layer 5a is smaller than both the adhesive force to the heated photothermal conversion layer 22 and the adhesive force between the first substrate and the heated photothermal conversion layer 22. I have. Therefore, the crystallized organic semiconductor layer 5a can be easily peeled off from the separation layer of the first member A. Therefore, the crystallized organic semiconductor layer 5a can be easily formed so as to connect the source electrode 4s and the drain electrode 4d of the second member.

  The separation layer has a property that the adhesive force to the crystallized organic semiconductor layer 5a is smaller than both the adhesive force to the heated photothermal conversion layer 22 and the adhesive force between the first substrate and the heated photothermal conversion layer 22. Any material can be used regardless of whether it is an organic material or an inorganic material. Examples of organic materials are silicone polymers, polyimide resins, polyvinyl alcohol, polyparaxylylene, and the like. Moreover, when using the resin layer by which the photothermal conversion agent was kneaded as the photothermal conversion layer 22, it can be set as the photothermal conversion layer 22 which has a function of a separation layer. An example is polyvinyl alcohol in which carbon black is dispersed.

(Organic semiconductor layer)
The layer 5 containing the organic semiconductor in the amorphous state of the first substrate 20 will be described. A layer 5 containing an organic semiconductor in an amorphous state is on the photothermal conversion layer 22 or the separation layer described above. The layer 5 containing an organic semiconductor is heated by irradiating the photothermal conversion layer 22 with light. The layer 5 containing the heated organic semiconductor is melted or sublimated and crystallized. Since the crystallized organic semiconductor layer 5a has a higher carrier mobility than the amorphous state, an organic TFT having good characteristics can be formed.

The layer 5 containing an amorphous organic semiconductor is heated to melt and crystallize. The π-conjugated polymer and oligomer in which the alkyl group possessed by the layer 5 containing such an organic semiconductor forms an array structure is preferable. Specific examples of the π-conjugated polymer and oligomer include thiophene, vinylene, chelenylene vinylene, phenylene vinylene, p-phenylene, a substituted product thereof, or two or more of these repeating units, and the number of repeating units ( Preferred is at least one selected from the group consisting of an oligomer wherein n) is 2 to 15, a polymer wherein the number (n) of repeating units is 20 or more, and a condensed polycyclic aromatic compound such as pentacene. A material having a three-dimensional regular structure by adding a substituent such as a C _{4 to} C ₁₅ alkyl group to at least one of the repeating units is preferable.

  By making the alkyl group possessed by the layer 5 containing the organic semiconductor a π-conjugated polymer or oligomer that forms an array structure, the solubility of the organic semiconductor material in the organic solvent is enhanced, In the course of cooling and crystallization, the higher order structure of the polymer or oligomer has an effect of imparting regularity, and is preferable because it has an effect of further improving the carrier mobility.

  The layer 5 containing an amorphous organic semiconductor is sublimated by heating and the deposited molecules are crystallized. The layer 5 containing such an organic semiconductor is formed of an organic solvent such as a silyl group, a ferrocenyl group, a silylalkyl group, a silylalkoxy group, a silylalkenyl group, a ferrocenylalkyl group, a ferrocenylalkoxy group, or a ferrocenylalkenyl group. An acene-based compound to which a substituent for improving the solubility in is added is preferable. As the acene compound material, pentacene, tetracene, anthracene, anthradithiophene and the like are preferable. It is preferable to use an acene compound because the stacking state between molecules is improved during crystallization and the carrier mobility is further increased.

  As a method for producing the layer 5 containing an organic semiconductor on the light-to-heat conversion layer 22 on the first substrate 20 or the separation layer provided on the light-to-heat conversion layer 22, a vacuum deposition method, a molecular beam epitaxial growth method, an ion cluster can be used. Beam method, low energy ion beam method, ion plating method, CVD method, sputtering method, plasma polymerization method, electrolytic polymerization method, chemical polymerization method, spray coating method, spin coating method, blade coating method, dip coating method, casting method , Roll coating method, bar coating method, die coating method, ink jet method, LB method and the like, and can be used depending on the material. However, from the viewpoint of improving productivity in the above, a spin coating method, a blade coating method, a dip coating method in which an organic semiconductor material is dissolved in a suitable organic solvent and a thin film can be easily and precisely formed using the prepared solution. A roll coating method, a bar coating method, a die coating method, an ink jet method and the like are preferable as a method for producing the layer 5 containing an organic semiconductor.

  Although there is no restriction | limiting in particular as the film thickness of the layer 5 containing these organic semiconductors, The characteristic of the obtained organic TFT is largely dependent on the film thickness of the active layer which consists of organic semiconductors, The film thickness is Although it varies depending on the organic semiconductor, it is generally preferably 1 μm or less, particularly preferably in the range of 10 nm to 300 nm. By setting the thickness range of the organic semiconductor layer 5 to 10 nm to 300 nm, the stability is good and the off characteristics of the thin film transistor are not significantly deteriorated.

  As described above, the layer 5 containing an organic semiconductor in an amorphous state formed on the first substrate 20 having a flat and uniform base is preferable because it can have a uniform arrangement.

(electrode)
The electrode formed on the second substrate 30 will be described. On the second substrate 30, there are a gate electrode 2, a source electrode 4s, a drain electrode 4d, and the like as electrodes constituting the organic TFT. Between the gate electrode 2 and the source and drain electrodes 4s and 4d, there is an insulating film 3 described later.

  As a method for forming the gate electrode 2, first, a conductive thin film to be the gate electrode 2 is formed on the second substrate 30. The conductive thin film is not particularly limited as long as it is a conductive material, and a metal material that can sufficiently secure conductivity is preferable. For example, Au, Al, Cr, Ag, Mo, a material obtained by adding doping to these, and the like can be given.

  As a method for forming the above-described conductive thin film, a known method such as vapor deposition or sputtering can be used using the above-described materials as raw materials. Thereafter, the gate electrode 2 can be formed by patterning the conductive thin film using a known photolithography process (resist application, exposure, development) and an etching process. For the source electrode 4s and the drain electrode 4d, the same material and formation method as the gate electrode can be used.

  In addition to the formation of the source electrode 4s and the drain electrode 4d, a pixel electrode using tin-doped indium oxide (ITO) or the like is provided, and a display device in which organic TFT elements are arranged in an array can be configured. In this case, a gate bus electrode, a source bus electrode, and the like are provided to drive a plurality of organic TFTs arranged in an array. A method of providing a gate bus electrode, a source bus electrode, and the like may be the same as the method of providing the above electrodes.

(Insulating film)
The insulating film 3 that covers the gate electrode 2 will be described. The insulating film 3 is not particularly limited, and various insulating films 3 can be used. In particular, an inorganic oxide film having a high relative dielectric constant is preferable. Examples of the inorganic oxide include silicon oxide, aluminum oxide, tantalum oxide, and titanium oxide. Inorganic nitrides such as silicon nitride and aluminum nitride can also be suitably used.

  As a method for forming the insulating film 3, there are a dry process and a wet process. Examples of the dry process include a vacuum deposition method, a CVD method, a sputtering method, an atmospheric pressure plasma method, and the like. Examples of the wet process include a method by coating, a method by patterning such as printing and inkjet, and the like.

(Overlay process)
The superposition of the first member A and the second member B will be described. The first member A includes the first substrate 20, the photothermal conversion layer 22 described above, and the layer 5 containing an organic semiconductor. The second member B includes the second substrate 30, the electrode pattern (gate electrode 2, source electrode 4s, drain electrode 4d, etc.) and the insulating film 3.

  It is preferable to overlap the first member A on the second member B. This is easy to handle when the first substrate of the first member A is made smaller than the second substrate of the second member B.

  When the first member A and the second member B are overlapped, high-precision alignment between the first substrate and the second substrate is not required. A layer 5 containing an organic semiconductor is formed on almost the entire surface of the first substrate 20. The layer 5 including the semiconductor may be in a state of covering the region where the organic semiconductor layer 5a of the second substrate 30 is formed. Therefore, the two substrates need not be positioned with high precision when the first substrate 20 and the second substrate 30 are overlapped.

  When the layer 5 containing an organic semiconductor is melted by heating, the first member A and the second member B are preferably in close contact with each other. The organic semiconductor layer 5a that connects the source electrode 4s and the drain electrode 4d is easily formed when the layer 5 containing the organic semiconductor is crystallized by being in close contact. In addition, when the layer 5 containing an organic semiconductor is sublimated by heating, the first member A and the second member B have an organic semiconductor layer 5a that connects the source electrode 4s and the drain electrode 4d even if they are not in close contact with each other. Can be formed.

  The second substrate 30 is preferably provided with an alignment mark. The exposure method in the process of irradiating light described later includes mask exposure and scanning exposure using laser light. In the case of mask exposure, it is necessary to adjust the positional relationship between the exposure mask 40 and the second substrate 30. This is because it is necessary to match the position where the crystallized organic semiconductor layer 5 is formed so as to connect the source electrode 4s and the drain electrode 4d with the opening of the exposure mask. According to this alignment mark, the position of the exposure mask can be easily adjusted to the desired position of the second substrate 30. Further, in the case of scanning exposure using laser light, it is necessary to control the scanning exposure position, so that the second substrate 30 is positioned on, for example, a moving table 65 that performs scanning exposure in the scanning exposure apparatus 70 shown in FIG. There is a need to. The scanning exposure apparatus 70 has a function of irradiating an arbitrary position of the moving table 65 with laser spot light. Therefore, by aligning the second substrate 30 with a desired position on the moving table 65 easily and accurately according to the alignment marks 66a and 66b, the exposure area 68 can be scanned and exposed with laser spot light with high accuracy. it can.

  The scanning exposure apparatus 70 includes 60 laser light sources, 62 collimator lenses, 63 galvanometer mirrors, 64 f-θ lenses, 65 moving tables, and a control unit (not shown) for controlling them. The collimator lens 62 and the f-θ lens 64 condense the laser light from the laser light source to form a light spot on the surface of the moving table 65. Further, the light spot can be scanned in the X direction at high speed by the galvanometer mirror 63. By appropriately combining the operations of the galvanometer mirror 63 and the moving table 65, the first substrate 20 placed on the second substrate 30 on the moving table 65 can be arbitrarily scanned.

(Process of irradiating light)
After the first member A and the second member B are overlapped in the overlapping step, the photothermal conversion layer 22 is formed from the first substrate 20 side of the first member A by the mask exposure described above or the scanning exposure by laser light. Irradiate light L. The exposed photothermal conversion layer 22 heats the layer 5 containing an amorphous organic semiconductor provided on the photothermal conversion layer 22 by generating heat. Depending on the material, the layer 5 containing the heated organic semiconductor is melted and crystallized, or sublimated and deposited and crystallized. In either case of melting or sublimation, the state of the layer 5 containing an organic semiconductor is crystallized from an amorphous state.

(Separation process and peeling process)
After the step of irradiating light, the first member A and the second member B are separated from the overlapped state. The first member includes a light-to-heat conversion layer 22 whose adhesion to the organic semiconductor layer 5 a crystallized by heating is smaller than the adhesion to the first substrate 20. Further, the second member B has an adhesive force between the surface on which the organic semiconductor layer 5a that connects the source electrode 4s and the drain electrode 4d is formed and the organic semiconductor layer 5a that has been melted or sublimated and crystallized to form the organic semiconductor layer 5a. And the photothermal conversion layer 22 have a property of becoming larger than the adhesive force. Therefore, the photothermal conversion layer 22 and the organic semiconductor layer 5a are separated. Moreover, when there is a separation layer between the photothermal conversion layer 22 and the organic semiconductor layer 5a, the separation can be performed more easily.

  Therefore, when the first member A and the second member B are separated, the crystallized organic semiconductor layer 5a that connects the source electrode 4s and the drain electrode 4d of the second member is formed. When this separation step is completed, an organic TFT is completed on the second substrate 30 of the second member B.

  After the separation step, the first member A is preferably immersed in a solvent to peel off the layer 5 containing the organic semiconductor remaining in the first member A. By separating the layer 5 containing an organic semiconductor and recovering and reusing an expensive organic semiconductor material, resources can be effectively used, and manufacturing costs can be reduced.

  Since the organic semiconductor in the amorphous state has the property of being more soluble in the solvent than in the crystalline state, the organic semiconductor remaining in the first member A after the separation step can be easily dissolved in the solvent. Can be recovered.

  The bottom gate type organic TFT 10 of FIG. 1 has been described with reference to FIG. 3 and FIG. 4 along the manufacturing process flow shown in FIG. 2, but the top gate type organic TFT 80 shown in FIG. 2 can be manufactured in the same manner as the bottom gate type organic TFT 10 shown in FIG. 1 by rearranging the steps of the manufacturing process flow shown in FIG. The first member may be the same as described above. In addition, a second member having a source electrode and a drain electrode on the surface of the second substrate 30 is prepared. Thereafter, the first member and the second member are overlapped and exposed as described above, and then the first member and the second member are separated. Thus, a crystallized organic semiconductor layer 5a that connects the source electrode 4s and the drain electrode 4d to the second substrate 30 of the second member is formed. Furthermore, an organic TFT 80 can be completed by providing an insulating film and the gate electrode 2 on the organic semiconductor layer 5a.

(Example 1)
This will be described with reference to FIG. On a polyethylene terephthalate (PET) substrate having a thickness of 125 μm, which is the first substrate 20, a 10% by mass aqueous solution in which polyvinyl alcohol and carbon black are mixed at a mass ratio of 6: 4 is applied by a wire bar coating method. A photothermal conversion layer 22 having a thickness of about 0.5 μm was formed. This photothermal conversion layer 22 also serves as a separation layer.

  A well-purified regioregular poly-type (3-hexylthiophene) chloroform solution is applied onto the light-to-heat conversion layer 22 using a slit coating method, and then naturally dried to form an amorphous organic semiconductor having a thickness of 50 nm. A containing layer 5 was formed. Then, the organic solvent was dried by performing a heat treatment at 50 ° C. for 30 minutes in a nitrogen atmosphere (FIG. 3B). This was designated as first member A.

  Next, Al having a thickness of 130 nm was formed on a polyethersulfone (PES) substrate made by Sumitomo Bakelite, which is the second substrate 30, by sputtering. After the formation, patterning processing was performed in a normal photolithography process to form the gate electrode 2.

Next, a 300 nm SiO ₂ film was formed as an insulating film 3 using tetraethoxysilane (TEOS) as a liquid source on the second substrate 20 provided with the gate electrode 2 by an atmospheric pressure plasma CVD method.

  Next, a tin-doped indium oxide (ITO) film having a thickness of 100 nm is formed on the entire surface of the second substrate 30 on which the insulating film 3 is formed by sputtering, and then subjected to patterning processing in a normal photolithography process. A source electrode 4s, a drain electrode 4d, and a source bus line (not shown) were formed (FIG. 3A). The gate length of the channel portion constituting the transistor was 10 μm, and the gate width was 100 μm. This was designated as second member B.

  Next, the first member A and the second member were superposed on FIG. 3C (FIG. 3C). The alignment of the exposure mask 40 is performed using alignment marks provided on the second substrate 30. After alignment, the photothermal conversion layer 22 is exposed by irradiating the light L of the xenon discharge lamp from the first substrate 20 side (FIG. 3D). As a result, the layer 5 containing the organic semiconductor of the first member A melts and crystallizes upon exposure.

  Thereafter, the first member A and the second member B are separated. As a result, an organic semiconductor layer 5a that connects the source electrode 4s and the drain electrode 4d of the second member is formed (FIG. 3E). The thickness of the formed organic semiconductor layer 5a was 50 nm.

Immediately after fabrication, the mobility of the organic TFT was 0.032 m ² / V · sec on average, and the on-off ratio was 6500, which was a favorable characteristic.

(Example 2)
This will be described with reference to FIG. The process was the same as in Example 1 except for the transfer process.

The first member A and the second member B are overlapped as shown in FIG. As shown in FIG. 5, the alignment marks 66 a and 66 b provided on the second substrate 30 are used to fix the movable table 65 of the scanning exposure apparatus 70 at a predetermined position. Thereafter, as shown in FIG. 4D, scanning exposure was performed with the light L from the first substrate 20 side using the laser 60 (FIG. 4D). The laser 60 used at this time has a wavelength of 830 nm and 10 mW, and the focused light spot has an energy density of 200 mJ / cm ² . As a result, the layer 5 containing the organic semiconductor of the first member A melts and crystallizes upon exposure.

  Thereafter, the first member A and the second member B are separated. As a result, an organic semiconductor layer 5a that connects the source electrode 4s and the drain electrode 4d of the second member is formed (FIG. 4E). The thickness of the formed organic semiconductor layer 5a was 50 nm.

Immediately after fabrication, the mobility of the organic TFT was 0.032 m ² / V · sec on average, and the on-off ratio was 11300, which was a favorable characteristic. The reason why the on-off ratio is better than that in Example 1 is presumed to be that the edge shape of the region exposed by using the light spot on which the laser beam is condensed becomes sharper and the Off characteristic is improved. .

(Example 3)
This will be described with reference to FIG.

  A 10% by mass aqueous solution in which polyvinyl alcohol and carbon black are mixed at a mass ratio of 5: 1 is applied on a PET substrate having a thickness of 125 μm, which is the first substrate 20, by a wire bar coating method, and is about 0.5 μm. A photothermal conversion layer 22 having a thickness was formed. This photothermal conversion layer 22 also serves as a separation layer.

  Next, a 0.5 mass% toluene solution of triisopropylsilylpentacene shown in Compound 1 is applied onto the photothermal conversion layer 22 by a die coating method, and then naturally dried to form an amorphous organic film having a thickness of 50 nm. A layer 5 containing a semiconductor was formed. Thereafter, a heat treatment was performed at 50 ° C. for 30 minutes in a nitrogen-substituted atmosphere to dry the organic solvent (FIG. 4A). Compound 1 is shown below.

  The second substrate 30 was the same as in Example 1.

Next, the first member A and the second member were overlapped as shown in FIG. As shown in FIG. 5, the alignment marks 66 a and 66 b provided on the second substrate 30 are used to fix the movable table 65 of the scanning exposure apparatus 70 at a predetermined position. Thereafter, as shown in FIG. 4D, scanning exposure was performed with the light L from the first substrate 20 side using the laser 60 (FIG. 4D). The laser 60 used at this time has a wavelength of 830 nm and 10 mW, and the focused light spot has an energy density of 200 mJ / cm ² . As a result, the layer 5 containing the organic semiconductor of the first member A is sublimated and crystallized by exposure. Thereafter, the first member A and the second member B are separated. As a result, an organic semiconductor layer 5a that connects the source electrode 4s and the drain electrode 4d of the second member is formed (FIG. 4E). The thickness of the formed organic semiconductor layer 5a was 50 nm.

Immediately after the production, the mobility of the organic TFT was 0.15 m ² / V · sec on average, and the on-off ratio was 85000, which was a favorable characteristic.

It is a figure which shows an example of a structure of an organic thin-film transistor. It is a flowchart which shows the example of the manufacturing process of an organic thin-film transistor. It is a figure which shows the example of the manufacturing process of the organic thin-film transistor which uses mask exposure. It is a figure which shows the example of the manufacturing process of the organic thin-film transistor which uses a laser scanning light. It is a figure which shows the example of a laser scanning exposure apparatus. It is a figure which shows an example of a structure of an organic thin-film transistor.

Explanation of symbols

2 Gate electrode 3 Insulating film 4s Source electrode 4d Drain electrode 5 Layer containing organic semiconductor 5a Organic semiconductor layer 10, 80 Organic TFT
DESCRIPTION OF SYMBOLS 20 1st board | substrate 22 Photothermal conversion layer 30 2nd board | substrate 40 Exposure mask 60 Laser light source 66a, 66b Alignment mark 68 Exposure area 70 Scanning exposure apparatus A 1st member B 2nd member L Light

Claims (9)

Production of an organic thin film transistor having an insulating film between at least a source electrode, a drain electrode, an organic semiconductor layer connecting the source electrode and the drain electrode, a gate electrode, and the organic semiconductor layer and the gate electrode on a substrate In the method
It has the property of being melted or sublimated and crystallized by being heated with a photothermal conversion layer that is heated on the first substrate so that the adhesive force to the organic semiconductor layer becomes smaller than the adhesive force to the first substrate. A first member having a layer containing an amorphous organic semiconductor in this order, and at least the source electrode and the drain electrode as the uppermost layer of the second substrate, and the source electrode and the drain electrode The adhesive force between the surface on which the organic semiconductor layer to be connected is formed and the organic semiconductor layer formed by melting or sublimation and crystallization is larger than the adhesive force between the organic semiconductor layer and the photothermal conversion layer to be heated. Preparing a second member having the following properties:
Stacking the first member and the second member in a direction in which the layer containing the organic semiconductor of the first member and the source electrode and the drain electrode of the second member face each other;
In order to form the organic semiconductor layer that connects the source electrode and the drain electrode, the photothermal conversion layer is irradiated with light from the first substrate side so that the organic semiconductor is heated until it melts or sublimates. And a process of
The method of manufacturing an organic thin film transistor, wherein the step of separating the first member and the second member is performed in this order. After the step of irradiating the light between the light-to-heat conversion layer and the layer containing the organic semiconductor, the first member has an adhesive force with respect to the organic semiconductor layer and an adhesive force with respect to the light-to-heat conversion layer. 2. The method for producing an organic thin film transistor according to claim 1, further comprising a separation layer smaller than any of the adhesive strength between the substrate and the photothermal conversion layer. 3. The method of manufacturing an organic thin film transistor according to claim 1, wherein in the step of irradiating the light, the photothermal conversion layer is exposed by mask exposure. The step of irradiating the light comprises concentrating laser light on the photothermal conversion layer to form a light spot, and scanning the light spot to expose the photothermal conversion layer. The manufacturing method of the organic thin-film transistor of description. 5. The method of manufacturing an organic thin film transistor according to claim 1, wherein the organic semiconductor layer is a π-conjugated polymer or an oligomer in which an alkyl group possessed forms an array structure. The method of manufacturing an organic thin film transistor according to any one of claims 1 to 4, wherein the organic semiconductor layer is an acene-based compound. The method for manufacturing an organic thin film transistor according to claim 1, wherein the first substrate is smaller than the second substrate. An alignment mark is provided on the second substrate, and the first substrate and the second substrate do not overlap at the position of the alignment mark when the first substrate and the second substrate are overlapped. The method for producing an organic thin film transistor according to claim 1, wherein the method is characterized in that: 9. The method according to claim 1, further comprising a step of detaching the remaining layer containing the organic semiconductor by immersing the first member in a solvent after the separating step. Manufacturing method of organic thin-film transistor.

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