JP4231248B2 - Organic transistor and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic transistor having an insulating film and an organic semiconductor film, and a manufacturing method thereof .
[0002]
[Prior art]
In recent years, organic transistors have attracted attention as drive elements for various electronic devices. An organic transistor uses an organic material for a semiconductor film. For this reason, it can be manufactured at a low temperature by using a printing method that can easily form a uniform film as compared with an inorganic transistor that often uses a vacuum device, and the area can be easily increased. . Further, since an organic material capable of producing a semiconductor layer film at a low temperature is used, a soft plastic substrate can be used, and a flexible element can be produced.
[0003]
A general organic transistor includes a substrate, a gate electrode, a gate insulating film, a source / drain electrode, and an organic semiconductor film. In organic transistors, the voltage applied to the gate electrode (gate voltage) is changed to control the amount of charge at the interface between the gate insulating film and the organic semiconductor, and the current value between the source electrode and the drain electrode is changed to perform switching. To do.
[0004]
[Problems to be solved by the invention]
Here, the characteristics of the organic transistor largely depend on the insulating property of the gate insulating film and the orientation of the organic semiconductor film. In the assembly using plastic as the material of the substrate, it is necessary to perform all the manufacturing processes at a low temperature, and the temperature for forming the gate insulating film is also required to be low. However, when the gate insulating film is formed at a low temperature, pinholes and irregularities (porous) may occur in the gate insulating film. Thus, if there are pinholes or irregularities in the gate insulating film, the insulating property of the gate insulating film is lowered, and there is a concern about the occurrence of gate leakage current.
[0005]
On the other hand, YY. Lin, D.D. J. et al. Gundlach, S.M. F. Nelson, and T.M. N. Jackson, IEEE Electron Devices Letters vol. 8 No. 12 P.M. P. 606-P. P. 608 (1997) reduces the surface energy of the surface on which the organic semiconductor film is formed by forming a hydrophobic material on the surface of the gate insulating film, grows organic semiconductor crystal grains, and increases the number of carriers. It has been reported that mobility has been obtained.
[0006]
In addition, some reports have been made on the formation method and surface treatment method of the gate insulating film. M.M. L. Swiggers, G.M. Xia, J .; D. Slinker, A .; A. Gorodetsky, and G.G. G. Mallarias, Applied Physics Letters, vol. 79, no. 9 p. P. In 1300-130 (2001), a thin film of polyvinyl alcohol (PVA) is formed on the surface of the gate insulating film SiO _2, that the 0.02 cm / Vs was obtained as a carrier mobility of pentacene is the material of the organic semiconductor Reporting.
[0007]
However, in this method, since PVA is a highly paintable material, it is suitable for planarizing a gate insulating film that fills pinholes and irregularities in the gate insulating film. However, an organic semiconductor such as pentacene is used as an organic semiconductor. When a film is formed, the growth of crystal grains is not promoted and high mobility cannot be expected.
[0008]
Japanese Patent Laid-Open No. 13-94107 discloses a method for forming a thin fluoropolymer layer on a gate insulating film. However, in this method, the growth of crystal grains of the organic semiconductor is promoted by utilizing the hydrophobic group arranged on the surface of the fluoropolymer layer. However, since the fluoropolymer has low wettability, Fine irregularities and pinholes cannot be sufficiently filled, and the insulating properties of the gate insulating film cannot be improved.
[0009]
The present invention has been made in view of the above problems, and an object thereof is to provide an insulating film having excellent insulating properties, an organic transistor in which crystal growth of organic molecules is promoted, and a method for manufacturing the same.
[0012]
[Means for Solving the Problems]
According to the first aspect of the present invention, in the organic transistor, the gate electrode formed on the substrate , the gate insulating film formed on the gate electrode, and the wettability formed by coating on the gate insulating film. A first organic film containing a high organic material, a second organic film formed on the first organic film, and containing an organic material composed of a plurality of organic molecules having a hydrophobic group, on the second organic film And an organic semiconductor film containing an organic semiconductor material, and a source electrode and a drain electrode formed on the organic semiconductor film.
[0013]
According to the first aspect of the present invention, the gate electrode formed on the substrate , the gate insulating film formed on the gate electrode, and the organic material having high wettability formed by applying on the gate insulating film. a first organic layer containing the material, formed on said first organic film, a second organic film containing an organic material comprising a plurality of organic molecules having a hydrophobic group, formed on said second organic film The organic semiconductor film containing the organic semiconductor material, and the source electrode and the drain electrode formed on the organic semiconductor film, the insulating film having excellent insulating properties, and crystal growth of organic molecules were promoted. An organic transistor having an organic semiconductor film can be provided.
[0014]
According to a second aspect of the invention, in the organic transistor according to claim 1, wherein the hydrophobic group of the plurality of organic molecules, characterized in that it is oriented in a certain direction.
[0015]
According to the second aspect of the present invention, since the hydrophobic groups of the plurality of organic molecules are oriented in a certain direction, the insulating film having excellent insulating properties and the organic semiconductor in which the crystal growth of the organic molecules is promoted An organic transistor having a film and an organic semiconductor film in which the orientation of organic molecules is arbitrarily controlled can be provided.
[0016]
According to a third aspect of the present invention, in the organic transistor according to the first or second aspect , the gate insulating film is composed of one or a plurality of layers, and the material of the one or a plurality of layers is oxide, nitride, oxidation nitrides, characterized in that it is selected fluorinated compound, and from the group consisting of diamond-like carbon independently.
[0017]
According to the invention of claim 3, wherein said gate insulating film is made of one or more layers, the material of the one or more layers, oxides, nitrides, oxynitrides, fluoride compounds, and diamond Since it is independently selected from the group consisting of like carbon, it has an insulating film with excellent insulating properties, and an organic semiconductor film in which crystal growth of organic molecules is promoted, and a gate insulating film that can be formed by various methods An organic transistor having the following can be provided.
[0018]
Invention of claim 4, wherein, in the method of manufacturing the organic transistor, by applying step, the step of forming a gate insulating film on the gate electrode, on the gate insulating film forming the gate electrode on a substrate, wettability forming a first organic film containing a high organic material step, on said first organic film, forming a second organic film containing an organic material having a hydrophobic group, said second organic film A step of forming an organic semiconductor film containing an organic semiconductor material; and a step of forming a source electrode and a drain electrode on the organic semiconductor film .
[0019]
According to the invention of claim 4, wherein the step of forming a gate electrode on a substrate, forming a gate insulating film on the gate electrode, by applying on the gate insulating film, a high wettability organic material Forming a first organic film including: forming a second organic film including an organic material having a hydrophobic group on the first organic film ; forming an organic semiconductor material on the second organic film And forming a source electrode and a drain electrode on the organic semiconductor film, so that an insulating film having excellent insulating properties and an organic film in which crystal growth of organic molecules is promoted A method for manufacturing an organic transistor having a semiconductor film can be provided.
[0020]
According to a fifth aspect of the present invention, in the method of manufacturing an organic transistor according to the fourth aspect , the second organic film is rubbed so that the hydrophobic group of a plurality of organic molecules constituting the organic material having the hydrophobic group is obtained. The method further includes the step of aligning in a certain direction.
[0021]
According to the fifth aspect of the present invention, the method further includes the step of rubbing the second organic film and orienting the hydrophobic groups of the plurality of organic molecules constituting the organic material having the hydrophobic group in a certain direction. An organic transistor manufacturing method having an insulating film having excellent insulating properties and an organic semiconductor film in which crystal growth of organic molecules is promoted and an organic semiconductor film in which the orientation of organic molecules is arbitrarily controlled is provided be able to.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0023]
The organic electronic device of the present invention is, for example, an organic transistor. Below, the organic electronic device of this invention is demonstrated as an organic transistor.
[0024]
The present invention includes a first organic thin film and a second organic thin film in an organic transistor including a substrate, a gate electrode, a gate insulating film, a source electrode, a drain electrode, and an organic semiconductor film. Here, the first organic thin film is formed on the surface of the gate insulating film, and the second organic thin film is formed on the surface of the first organic thin film. These first and second organic thin films are formed by sequentially applying organic materials corresponding to these two organic thin films to the surface of the gate insulating film, and the gate insulating film, the first and second organic thin films are formed. It becomes a (laminated) insulating film including a thin film.
[0025]
On the substrate, the gate electrode, the source electrode, and the drain electrode can be manufactured using a known metal material and method. As the material of the organic semiconductor film, organic molecules such as pentacene can be used, and the organic semiconductor film may be formed by a printing method.
[0026]
The gate insulating film is made of oxide such as SiO ₂ , Ta ₂ O ₅ , Al ₂ O ₃ , ZrO ₂ , La ₂ O ₃ , TiO ₂ , Y ₂ O ₃ , CeO ₂ , nitride such as Si ₂ N ₃ , It consists of one or a plurality of layers containing an oxynitride such as SiO _x N _y , a fluoride such as CaF, and an inorganic material such as diamond-like carbon (DLC). When the gate insulating film is composed of a plurality of layers, the material of each layer is independently selected from the above inorganic materials.
[0027]
In the case where the gate insulating film is made of a metal oxide of the gate electrode, the oxide gate insulating film can be formed by oxidizing the surface of the gate electrode by an anodic oxidation method. When plastic is used as the material of the organic transistor substrate, the gate insulating film can be formed at a low temperature by using an anodic oxidation method. However, as long as the gate insulating film can be formed on the plastic substrate at a low temperature, a sputtering method, a vacuum evaporation method, an ion beam sputtering method, a CVD method, or the like may be used in addition to the anodic oxidation method.
[0028]
When the gate insulating film is other than an oxide, the gate insulating film can be formed on the plastic substrate at a low temperature by using a sputtering method such as a magnetron sputtering method, a vacuum deposition method, an ion beam sputtering method, or a CVD method. it can.
[0029]
The first organic material is an organic material with high wettability. Here, the organic material having high wettability means an organic material having a contact angle with respect to the surface of the gate insulating film smaller than 90 degrees. _{Specifically,} CH ₂ CHOCOCH _3, compounds such as _{CH 3 CHO, (- CH 2} CHOH-) n, (- CH 2 CHCl-) n, (- CH 2 CHOCOCH 3 -) n polymer compound such as, the _-CH 2 CHCl- or _-CH 2 CCl ₂ in the repeating unit - a polymer compound having the like. These highly wettable organic materials are dissolved in solvents such as methanol, acetone, toluene, and ethyl acetate, and uniformly applied to the surface of the gate insulating film using a dipping method, spin coating method, etc. An organic thin film is formed.
[0030]
Here, when the gate insulating film is formed at a low temperature as described above, pinholes and irregularities may be formed on the surface of the gate insulating film. Such pinholes and irregularities cause a decrease in the insulating properties of the gate insulating film.
[0031]
Such a first organic material has high wettability, so that pinholes and irregularities formed on the surface of the gate insulating film can be filled to make the insulating film dense and flattened. Therefore, the insulating property of the gate insulating film can be maintained by applying the first organic material to the gate insulating film.
[0032]
The second organic material is an organic material having hydrophobicity. In particular,
_{C 8 F 17 SO 2 N (} C 2 H 5) (CH 2) 2 OH, C 8 F 17 SO 2 N (C 2 H 5) SO 4 Na, H (CF 2) 8 PO (OH) 2, CF Hydrophobic surfactants represented by molecular formulas such as ₃ (CF ₂ ) ₆ (CH ₂ ) ₅ COONa, and hydrophobic surfactants such as silicone surfactants represented by Si [O (CH ₂ ) _n OR] ₄ High organic materials are mentioned. Further, a surfactant having a fluorocarbon hydrophobic group such as C _n F _{2n + 1} − or H (CF ₂ ) _n CH ₂ —, such as CH ₃ [Si (CH ₃ ) ₂ O] _n C ₃ H ₇ A surfactant having a silicone-based hydrophobic group may also be used. In addition, a composition combining the above surfactants may be used. These hydrophobic organic materials are uniformly applied to the surface of the first organic thin film using a dip method, a spin coating method, or the like to form a second organic thin film.
[0033]
By forming the second organic thin film exhibiting hydrophobicity in this way, the surface energy of the surface on which the organic semiconductor film is formed can be reduced, and the growth of crystal grains of the organic semiconductor film can be promoted. In other words, the carrier mobility of the organic semiconductor film can be improved by regularly arranging the organic molecules constituting the organic semiconductor film.
[0034]
Alternatively, the surface of the second organic thin film may be rubbed using a rubbing apparatus, and the hydrophobic groups of the molecules constituting the second organic thin film may be oriented in a certain direction. In this way, by rubbing the surface of the second organic thin film, the orientation of the organic molecules constituting the organic semiconductor film laminated on the second organic thin film can be arbitrarily controlled by controlling the orientation of the hydrophobic groups. can do.
[0035]
Therefore, according to the present invention, the organic material having high wettability and the organic material having a hydrophobic group are sequentially applied to the surface of the gate insulating film formed at a low temperature, and the first organic thin film and the second organic thin film are formed. By forming the (laminated) insulating film, the film quality of the gate insulating film can be densified and the surface energy of the second organic thin film can be reduced. Thus, an organic transistor having a semiconductor film having a (laminate) insulating film with high insulating properties and high carrier mobility can be manufactured. Therefore, when the (laminated) insulating film of the present invention is applied to a flexible organic transistor using a plastic substrate, an organic transistor that has excellent responsiveness and can be driven efficiently can be manufactured.
[0036]
[Example 1]
Next, a first embodiment of the organic transistor according to the present invention will be described with reference to FIG.
1A to 1D are cross-sectional views of an organic transistor schematically showing a method for manufacturing an organic transistor in a first embodiment of the present invention.
[0037]
As shown in FIG. 1A, in the organic transistor of this example, a gate electrode 2 made of a gate metal (tantalum: Ta) was first formed on the surface of a plastic substrate 1 made of polycarbonate. Next, the surface of the gate electrode 2 was anodized to form a gate insulating film 3 made of a gate metal oxide (ditantalum pentoxide: Ta ₂ O ₅ ) on the surface of the gate electrode 2.
[0038]
Next, as shown in FIG. 1B, a first organic material is uniformly applied on the surface of the gate insulating film 3 on the gate insulating film 3 by using a spin coat method or the like. The organic thin film 4 was formed. The film thickness of the first organic thin film 4 is 10 nm or less. Polyvinyl acetate (—CH ₂ CHOCOCH ₃ —) _n was used as the first organic material applied to the gate insulating film 3. This organic material has high wettability with respect to the substrate and exhibits hydrophilicity, so that pinholes and irregularities on the surface of the underlying gate insulating film 3 can be filled and made dense. After this first organic material was applied to the gate insulating film 3, the substrate was baked at a temperature of 120 ° C. or lower to form the first organic thin film 4. The time required for baking was 1-2 hours.
[0039]
Next, as shown in FIG.1 (c), the 2nd organic material was apply | coated uniformly by the spin coat method on the surface of the 1st organic thin film 4, and the 2nd organic thin film 5 was formed. As the second organic material applied to the first organic thin film 4, a fluorosurfactant was used.
[0040]
Next, as shown in FIG. 1D, an organic semiconductor film 6 was formed by applying pentacene, which is an organic molecule, on the surface of the second organic thin film 5 by a printing method. Here, since a highly hydrophobic fluorine-based surfactant was used as the second organic material, growth of crystal grains of the organic semiconductor film 6 made of pentacene could be promoted. Further, two conductive strips spaced apart in the horizontal direction were formed on the surface of the organic semiconductor film 6 as the source electrode 7 and the drain electrode 8 made of gold.
[0041]
As described above, the first organic thin film 4 having high wettability and the second organic thin film 5 having high hydrophobicity are sequentially stacked on the gate insulating film 3, thereby densifying the film quality of the gate insulating film. The growth of crystal grains of the organic semiconductor film 6 can be promoted.
[0042]
[Example 2]
Next, a second embodiment of the organic transistor according to the present invention will be described with reference to FIG.
2A to 2D are cross-sectional views of an organic transistor schematically showing a method for manufacturing an organic transistor in a second embodiment of the present invention.
[0043]
As shown in FIG. 2A, in the organic transistor in this example, a gate electrode 12 made of a gate metal (tantalum: Ta) was first formed on the surface of a plastic substrate 11 made of polycarbonate. Next, the surface of the gate electrode 12 was anodized to form a gate insulating film 13 made of a gate metal oxide (ditantalum pentoxide: Ta ₂ O ₅ ) on the surface of the gate electrode 2.
[0044]
Next, as shown in FIG. 2B, a first organic material is uniformly applied on the surface of the gate insulating film 13 on the gate insulating film 13 by using a spin coat method or the like. The organic thin film 14 was formed. Polyvinyl acetate (—CH ₂ CHOCOCH ₃ —) _n was used as the first organic material applied to the gate insulating film 3. This organic material has high wettability with respect to the substrate and exhibits hydrophilicity, so that pinholes and irregularities on the surface of the underlying gate insulating film 3 can be filled and made dense. After this first organic material was applied to the gate insulating film 13, the substrate was baked at a temperature of 120 ° C. or lower for 1 to 2 hours to form the first organic thin film 14.
[0045]
Next, as shown in FIG. 2C, a second organic thin film 15 was formed by uniformly applying a second organic material on the surface of the first organic thin film 14 by spin coating. As the second organic material applied to the first organic thin film 14, a fluorosurfactant was used. Here, the surface of the second organic thin film 15 was rubbed using a rubbing apparatus. Thereby, the hydrophobic group of the fluorosurfactant constituting the second organic thin film 15 could be oriented in a certain direction with respect to the substrate.
[0046]
Next, as shown in FIG. 2D, an organic semiconductor film 16 was formed by applying pentacene, which is an organic molecule, on the surface of the second organic thin film 15 by a printing method. Here, since a highly hydrophobic fluorine-based surfactant is used as the second organic material, the growth of crystal grains of the organic semiconductor film 16 made of pentacene is promoted and the surface of the second organic thin film 15 is rubbed. As a result, the molecular plane of pentacene could be uniformly oriented perpendicularly to the surface of the second organic thin film 15. Further, two conductive strips spaced apart in the horizontal direction were formed on the surface of the organic semiconductor film 6 as the source electrode 17 and the drain electrode 18 made of gold.
[0047]
[Example 3]
Next, a third embodiment of the organic transistor according to the present invention will be described with reference to FIG.
FIG. 3 is a cross-sectional view of an organic transistor according to a third embodiment of the present invention.
[0048]
As in the first and second embodiments, the organic transistor of this embodiment has a gate electrode 22 on the surface of the plastic substrate 21, a gate insulating film 23 on the surface of the gate electrode 22, and a first electrode on the gate insulating film 23. One organic thin film 24, a second organic thin film 25 on the first organic thin film 24, an organic semiconductor film 26 on the second organic thin film 25, and two conductive strips horizontally spaced on the organic semiconductor film 26 (Source and drain electrodes) 27 and 28 are provided.
[0049]
In the present embodiment, the material of the gate insulating film 23 is silicon nitride (Si ₂ N ₃ ), and the gate insulating film 23 is formed by magnetron sputtering. The temperature of the plastic substrate was 100 ° C. or less, and the thickness of the gate insulating film was 1000 mm. Next, the same first organic material and second organic material as described above are sequentially and uniformly applied on the surface of the gate insulating film 23 using a spin coating method, and the first organic thin film 24 and the second organic thin film are then applied. 25 was formed.
[0050]
As the gate insulating film 23, oxides such as SiO ₂ , Ta ₂ O ₅ , Al ₂ O ₃ , ZrO ₂ , La ₂ O ₃ , TiO ₂ , Y ₂ O ₃ , and CeO ₂ , CaF (fluoride film), An organic transistor using SiO _x N _y (oxynitride film) or DLC (diamond-like carbon film) was similarly produced. In this way, an organic field effect transistor (FET) having high current ON / OFF characteristics and high carrier mobility was obtained.
[0051]
Although the present invention has been described above as embodiments and examples of the present invention, the present invention is not limited to these embodiments and examples, and these implementations can be made without departing from the scope of the present invention. Various modifications, applications, and combinations of the embodiments and examples can be made. For example, the first organic material and / or the second organic material may be appropriately selected from the materials described above as necessary to form a (laminated) insulating film made up of a plurality of thin films. In the embodiments of the invention, the present invention has been described as an organic transistor. However, the present invention is not limited to an organic transistor, and an insulating film having a high insulating property is formed at a particularly low temperature. The present invention can be applied to an organic electronic device that forms an organic semiconductor film whose crystal growth is promoted on an insulating film and a method for manufacturing the organic electronic device. Here, the organic electronic device has on the substrate at least two electrodes, at least one insulating film formed on the at least one electrode, and at least one organic semiconductor film containing an organic semiconductor material, for example, an organic transistor In addition to this, organic diodes are included.
[0052]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the organic transistor which has the insulating film excellent in insulation, the organic-semiconductor film by which the crystal growth of the organic molecule was accelerated | stimulated, and the manufacturing method of this organic transistor can be provided.
[0053]
[Brief description of the drawings]
FIGS. 1A to 1D are cross-sectional views of an organic transistor schematically showing a method for manufacturing an organic transistor according to a first embodiment of the present invention.
FIGS. 2A to 2D are cross-sectional views of an organic transistor schematically showing a method for manufacturing an organic transistor in a second embodiment of the present invention.
FIG. 3 is a cross-sectional view of an organic transistor according to a third embodiment of the present invention.
[Explanation of symbols]
1, 11, 21 Plastic substrate 2, 12, 22 Gate electrode 3, 13, 23 Gate insulating film 4, 14, 24 First organic thin film 5, 15, 25 Second organic thin film 6, 16, 26 Organic semiconductor film 7, 17, 27 Source electrode 8, 18, 28 Drain electrode

Claims (5)

A gate electrode formed on the substrate , a gate insulating film formed on the gate electrode, a first organic film containing an organic material having high wettability formed by applying on the gate insulating film, A second organic film including an organic material composed of a plurality of organic molecules having a hydrophobic group, formed on the first organic film, and an organic semiconductor including an organic semiconductor material formed on the second organic film An organic transistor comprising: a film ; and a source electrode and a drain electrode formed on the organic semiconductor film. The organic transistor according to claim 1, wherein the hydrophobic groups of the plurality of organic molecules are oriented in a certain direction. The gate insulating film is composed of one or more layers,
Material of the one or more layers, oxides, nitrides, oxynitrides, according to claim 1 or 2, characterized in that it is selected fluorinated compound, and from the group consisting of diamond-like carbon independently Organic transistor. Forming a gate electrode on the substrate;
Forming a gate insulating film on the gate electrode;
Applying the gate insulating film to form a first organic film containing an organic material having high wettability;
Forming a second organic film containing an organic material having a hydrophobic group on the first organic film ;
Forming an organic semiconductor film containing an organic semiconductor material on the second organic film ; and
A method for producing an organic transistor , comprising: forming a source electrode and a drain electrode on the organic semiconductor film . The method of claim 4 , further comprising: rubbing the second organic film to orient the hydrophobic groups of a plurality of organic molecules constituting the organic material having the hydrophobic group in a certain direction. Manufacturing method of organic transistor .

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