JP2010278227A - Thin-film transistor, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic thin-film transistor having small anisotropy of electrical characteristicss, even while maintaining large mobility of charges. <P>SOLUTION: The thin-film transistor (10) has a source electrode (S), a drain electrode (D), a gate electrode (G), a gate insulating film (Ins) and an organic semiconductor film (Semi) which are formed on one surface of a substrate (Sub), wherein the gate insulating film insulates the source and drain electrodes from the gate electrode, and a voltage applied to the gate insulating film controls a current flowing from the source electrode to the drain electrode through the organic semiconductor. In the thin-film transistor, the substrate or the gate insulating film has a hydroxyl group on the surface, the thin-film transistor further has an amorphous organosilane thin film (Amr), the amorphous organosilane thin film is formed directly on the substrate or gate insulating film having the hydroxyl group on the surface, and the organic semiconductor film is formed directly on the amorphous organosilane thin film. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a thin film transistor, in particular, a thin film transistor having an organic semiconductor film, and a method for manufacturing the same.

  In recent years, a semiconductor element typified by a thin film transistor (TFT) has been used for various applications such as a liquid crystal display device, a solar battery panel, and the like. A semiconductor element mainly used at present, particularly a semiconductor element using silicon as a semiconductor material, has a high manufacturing cost because a vacuum process such as CVD or sputtering is used at the time of manufacture. Moreover, it is difficult for such a semiconductor element to be a flexible element formed on a polymer film or the like from the viewpoint of process temperature.

  Applying organic semiconductor elements that can be fabricated by simple methods to active elements in fields that require low cost, such as lightweight and flexible elements that are expected to be put to practical use in the future, and RF-ID (Radio Frequency IDentification) Is being considered. The vacuum vapor deposition apparatus and coating apparatus used in the manufacture of such an organic semiconductor element are less expensive than the CVD apparatus and sputtering apparatus used in the manufacture of inorganic semiconductors. In the production of an organic semiconductor element, since the process temperature is low, the organic semiconductor element can be formed on a polymer film or paper.

  A thin film transistor using an organic semiconductor has a source electrode, a drain electrode, a gate electrode, a gate insulating film, and an organic semiconductor film on a substrate. In such a thin film transistor, a source electrode, a drain electrode, and a gate electrode are insulated from each other by a gate insulating film, and a current flowing through the organic semiconductor from the source electrode to the drain electrode is controlled by a voltage applied to the gate electrode.

  Here, the organic semiconductor film is an aggregate of a low molecular compound or a high molecular compound. As low molecular organic semiconductor materials, acene compounds (condensed polycyclic compounds condensed linearly) such as pentacene and thiophene oligomers are known. Further, regioregular polyalkylthiophene (P3AT), poly (fluorenebithiophene) (F8T2) and the like are known as polymer organic semiconductor materials.

  In order to obtain high switching characteristics in an organic thin film transistor, it is necessary to increase the charge mobility of the organic semiconductor film. As a method for improving the charge mobility of the organic semiconductor film, organic semiconductor molecules forming the organic semiconductor film have been highly oriented. As a method of forming an organic semiconductor film having such a high orientation, the surface of the substrate or the gate insulating film on which the organic semiconductor film is deposited is surface-treated, in particular, the surface of the gate insulating film on which the organic semiconductor film is deposited is self-organized. It is known to coat with a monomolecular film (SAM: Self-Assembled Monolayer) (Patent Documents 1 and 2, and Non-Patent Documents 1 to 3).

  Here, a silicon oxide thin film can be used as the substrate or gate insulating film on which the organic semiconductor film is deposited, and an organosilane monomolecular film is used as the SAM covering the substrate or gate insulating film. It has been broken.

  Thus, when an organic semiconductor film is formed on a substrate or a gate insulating film that has been surface-modified by SAM in advance, the charge mobility of the organic semiconductor film is improved, and thereby the charge mobility that exceeds the current TFT made of amorphous silicon. An organic TFT having the above has also been reported.

  On the other hand, in terms of actual application, when a plurality of elements are integrated, there is a problem that characteristic variation occurs between the elements. In this regard, for example, attempts have been made to stabilize the crystal domain and morphology of TIPS-pentacene by spin-coating a blend of TIPS-pentacene and poly (α-methylstyrene), thereby stabilizing the output current. (Non-Patent Document 4).

  Various techniques for modifying the surface of a substrate having an OH group such as silica by SAM such as organosilane (silane coupling agent) are known (Non-Patent Document 5), and the substrate is mainly in solution. A solution method in which a silane coupling reaction with an OH group is promoted and a gas phase method in which a reaction is carried out in a gas phase using an organosilane vapor are known as typical forming methods. In these methods, it is possible to form a substantially monomolecular thin film having an ordered structure (crystal structure) by strictly controlling the moisture in the reaction system.

  In addition, a method of forming an organosilane thin film using a microcontact printing method is also known (Non-Patent Document 6). In this case, it is possible to form an organosilane thin film by applying organosilane to a stamp having a pattern and transferring the organosilane to a substrate.

JP 2005-79560 A JP 2009-59751 A

H. Sirringhaus et al., Nature, 40, pp 4509-4521, 1999 A. Salleo et al., Applied Physics Letters, Vol. 81, No. 23, pp 4383-4385, 2002. Y. Y. Lin et al., IEEE Trans Electron Devices, 44, pp 1325-1331, 1997 T.A. Ohe et al., Applied Physics Letters, 93, pp053303, 2008 S. Onclin et al., Angelwandte Chemie International Edition, 44, p6282-6304, 2005 N. L. Jeon et al., Langmuir, 13, p3382-3391, 1997

  As described above, the organic semiconductor molecules are formed on the SAM to highly align the organic semiconductor molecules, thereby improving the charge mobility and improving the switching speed and the on / off ratio of the current. I came. However, in this case, the anisotropy of the electrical characteristics of the organic semiconductor molecules increases, thereby increasing the variation in the characteristics of the organic thin film transistors, and when there are a plurality of organic thin film transistors on the substrate surface, There is a problem that the variation of the characteristics increases.

  Accordingly, an object of the present invention is to provide an organic thin film transistor having a small anisotropy in electrical characteristics while maintaining a large charge mobility.

  The present inventor has found that the above-mentioned problems can be solved by laminating organic semiconductor molecules on a specific surface in the production of an organic thin film transistor, and has arrived at the following present invention.

<1> A source electrode, a drain electrode, a gate electrode, a gate insulating film, and an organic semiconductor film are provided on one surface of the substrate, and the gate insulating film insulates the source electrode, the drain electrode, and the gate electrode. And a thin film transistor that controls a current flowing through the organic semiconductor from the source electrode to the drain electrode by a voltage applied to the gate electrode,
The substrate or gate insulating film has a hydroxyl group on the surface, the thin film transistor further has an amorphous organosilane thin film, and the amorphous organosilane thin film has a hydroxyl group on the surface A thin film transistor which is directly formed on the organic semiconductor film and is formed directly on the amorphous organosilane thin film.
<2> The thin film transistor according to <1>, wherein the amorphous organosilane thin film has an average thickness of 10 nm or less.
<3> The thin film transistor according to <1> or <2>, wherein the amorphous organosilane thin film has a roughness Ra of 3 nm or less.
<4> The thin film transistor according to any one of <1> to <3>, wherein the amorphous organosilane thin film does not have a protrusion having a height of 30 nm or more.
<5> The thin film transistor according to any one of <1> to <4>, wherein the amorphous organosilane thin film contains a siloxane oligomer.
<6> The thin film transistor according to any one of <1> to <5>, wherein the amorphous organosilane thin film has a critical interface energy value of 10 to 30 mN / m.
<7> The thin film transistor according to any one of <1> to <6>, wherein the amorphous organosilane thin film is a trichloroorganosilane thin film or a trialkoxyorganosilane thin film.
<8> The thin film transistor according to any one of <1> to <7>, wherein a surface of the substrate or the gate insulating film having a hydroxyl group is provided by silica.
<9> The thin film transistor according to any one of <1> to <8>, wherein the surface of the substrate or the gate insulating film having a hydroxyl group is provided by a silica layer laminated on a polymer substrate.
<10> The thin film transistor according to any one of <1> to <9>, wherein a protective film is laminated on the organic semiconductor film.
<11> The above <1> to <10>, comprising forming the organosilane thin film on the substrate or the gate insulating film having a hydroxyl group on the surface by a contact printing method in an atmosphere of 10% or less of humidity. A method for producing the thin film transistor according to any one of the above.

  According to the organic thin film transistor of the present invention, since the organic semiconductor film is formed on the amorphous organosilane thin film, that is, the organosilane thin film with low orientation, the organic semiconductor film also becomes a film with low orientation. . In general, a low-orientation organic semiconductor film was considered to have low semiconductor properties, but a semiconductor film formed on an amorphous organosilane thin film was unexpectedly close to or highly equivalent to a highly-oriented organic semiconductor film. It has semiconductor characteristics. In addition, since the semiconductor film formed on the amorphous organosilane thin film has a low orientation, variations in semiconductor characteristics due to the in-plane orientation direction can be reduced.

FIG. 1 is a diagram showing a first example of a thin film transistor of the present invention. FIG. 2 is a diagram showing a second example of the thin film transistor of the present invention. FIG. 3 is a diagram showing a third example of the thin film transistor of the present invention. FIG. 4 is a diagram showing a fourth example of the thin film transistor of the present invention. FIG. 5 is a diagram showing a fifth example of the thin film transistor of the present invention. FIG. 6 is a diagram showing the results of in-plane X-ray diffraction of the organosilane thin films of Example 1 and Comparative Examples 1 and 2. FIG. 7 is a diagram showing rocking curves of the organic semiconductor films of Example 1 and Comparative Example 1.

  Hereinafter, the present invention will be described in detail.

<< Thin Film Transistor >>
The thin film transistor of the present invention has a source electrode, a drain electrode, a gate electrode, a gate insulating film and an organic semiconductor film on one surface of the substrate, and the gate insulating film insulates the source electrode, the drain electrode and the gate electrode, The current flowing through the organic semiconductor film from the source electrode to the drain electrode is controlled by the voltage applied to the gate electrode.

  The thin film transistor of the present invention has an arbitrary structure capable of controlling the current flowing through the organic semiconductor from the source electrode to the drain electrode by the voltage applied to the gate electrode. Therefore, for example, the thin film transistor of the present invention can have the structure shown in FIGS.

  Here, in the embodiment shown in FIG. 1, an amorphous organosilane thin film (Amr) is formed on a substrate (Sub), on which a source electrode (S), a gate electrode (G), and an organic semiconductor film ( Semi) is formed, a gate insulating film (Ins) is formed on the organic semiconductor film (Semi), and a gate electrode (G) is further formed on the gate insulating film (Ins). As shown in FIG. 5, the substrate (Sub) can also serve as the gate electrode (G).

  In the thin film transistor of the present invention, the substrate or gate insulating film has a hydroxyl group on the surface, the thin film transistor further has an amorphous organosilane thin film, and the amorphous organosilane thin film has a hydroxyl group on the surface. The organic semiconductor film is formed directly on the amorphous organosilane thin film, and is formed directly on the film.

  Patent Documents 1 and 2 can be referred to for the general configuration of the thin film transistor of the present invention, but each part of the thin film transistor of the present invention will be described in more detail below.

<Thin film transistor substrate>
The substrate of the thin film transistor of the present invention is made of any material capable of forming a thin film transistor by laminating a source electrode, a drain electrode, a gate electrode, a gate insulating film, an organic semiconductor film, and an amorphous organosilane thin film on one surface. Can be made. Accordingly, examples of the substrate include metal substrates, silica substrates, glass substrates, quartz substrates, alumina substrates, titania substrates, inorganic material substrates such as silicon substrates, and organic material substrates such as resin substrates. In addition, when this board | substrate is made from an electroconductive material, a board | substrate can also serve as a gate electrode.

  In the thin film transistor of the present invention, the substrate or gate insulating film has a hydroxyl group on the surface, and the substrate or gate insulating film having a hydroxyl group on the surface is used as an underlayer for the amorphous organosilane thin film. Therefore, when the thin film transistor substrate is used as an underlayer for the amorphous organosilane thin film, the substrate needs to have a hydroxyl group on the surface when the amorphous organosilane thin film is laminated. In this case, examples of the substrate include a silica substrate, a glass substrate, a quartz substrate, an alumina substrate, a titania substrate, a silicon substrate with a thermal oxide film or a natural oxide film, and a resin substrate having a silica surface layer. Further, as the substrate in this case, a resin substrate coated with a resin layer having a hydroxyl group on the surface, a resin substrate having a hydroxyl group on the surface in advance, or the like can be used.

  Note that the substrate of the thin film transistor can have any thickness depending on the application.

<Thin film transistor-insulating film>
The gate insulating film of the thin film transistor of the present invention can be manufactured using any material having sufficient insulation to insulate the source electrode and the drain electrode from the gate electrode. Therefore, the gate insulating film can be made of, for example, resin, metal oxide, particularly silica, glass, alumina, titania or the like.

  As described above, in the thin film transistor of the present invention, the substrate or gate insulating film has a hydroxyl group on the surface, and the substrate or gate insulating film having a hydroxyl group on the surface serves as an underlayer for the amorphous organosilane thin film. It is used. Therefore, when the gate insulating film is used as an underlayer for the amorphous organosilane thin film, the gate insulating film needs to have a hydroxyl group on the surface when the amorphous organosilane thin film is laminated. In this case, a metal oxide, particularly a film of silica, glass, alumina, titania, or the like can be used as the gate insulating film.

  Note that the thickness of the gate insulating film can be any thickness necessary to obtain a thin film transistor.

<Thin film transistor-amorphous organosilane thin film>
The thin film transistor of the present invention has an amorphous organosilane thin film formed on a substrate or a gate insulating film as a base layer having a hydroxyl group on the surface. Here, the amorphous organosilane thin film is bonded to the hydroxyl group of the underlayer through a silane coupling reaction. Note that “amorphous” in the organosilane thin film means that no peak due to the crystal structure is observed when in-plane X-ray diffraction is performed.

  The average thickness of the amorphous organosilane thin film can be 10 nm or less, 7 nm or less, 5 nm or less, or 3 nm or less. In particular, the amorphous organosilane thin film can have a uniform thickness.

  Here, regarding the present invention, the average thickness of the thin film is an optically measured thin film thickness, and in particular, an ellipsometer that irradiates the sample with light and measures the change in the polarization state of the light reflected from the sample is used. Measured.

  The roughness Ra of the amorphous organosilane thin film can be 3.0 nm or less, 2.0 nm or less, or 1.5 nm or less. This is because if the roughness is too large, the semiconductor characteristics of the organic semiconductor film formed on the amorphous organosilane thin film may deteriorate.

  Here, regarding the present invention, the average arithmetic roughness (centerline average roughness) (Ra) is defined in accordance with JIS B0601-1994. Specifically, the arithmetic average roughness (Ra) is determined by extracting a portion of the reference length l from the roughness curve in the direction of the center line, the center line of the extracted portion being the X axis, and the direction of the vertical magnification being the Y axis. And when the roughness curve is represented by y = f (x), it is represented by the following formula:

  The amorphous organosilane thin film can have no protrusion having a height of 30 nm or more, 20 nm or more, or 10 nm or more. This is because when the amorphous organosilane thin film has projections that are too large, the semiconductor characteristics of the organic semiconductor film formed on the amorphous organosilane thin film may deteriorate.

  The amorphous organosilane thin film may contain a siloxane oligomer, for example, 1 to 20% by volume of a siloxane oligomer resulting from the production of the amorphous organosilane thin film by a contact printing method using a siloxane polymer stamp. .

  The amorphous organosilane thin film may have a critical interface energy value of 10 to 30 mN / m, preferably 10 to 25 mN / m, more preferably 13 to 25 mN / m.

  In the present invention, the value of the critical interface energy is a value obtained by measuring the contact angle using several kinds of wetting index standard solutions (JIS K 6768) and using a Zisman plot.

  The organosilane for obtaining the amorphous organosilane thin film is not particularly limited, and examples thereof include alkylsilane, aromatic silane, perfluorosilane, and aminosilane, particularly trichloroorganosilane, and trialkoxyorganosilane.

  An amorphous organosilane thin film is formed on a substrate or gate insulating film as a base layer having a hydroxyl group on the surface by a contact printing method in an atmosphere with a humidity of 10% or less, preferably 7% or less, more preferably 5% or less. can do. If the humidity of the atmosphere in which the contact printing method is performed is too high, expression of the crystal structure of the organosilane thin film and generation of surface protrusions may occur. The stamp material used in this contact printing method is not particularly limited, and examples thereof include siloxane polymers such as polydimethylsiloxane. Further, the atmosphere in which the contact printing method is performed can be an inert atmosphere, particularly a nitrogen atmosphere.

  In the contact printing method for obtaining an amorphous organosilane thin film, a stamp coated with organosilane itself or a solution containing organosilane is brought into contact with a substrate or a gate insulating film as a foundation layer, whereby the foundation layer is removed from the stamp. Transfer the organosilane thin film. In this case, the contact time for keeping the stamp and the underlayer in contact varies depending on the conditions, but is generally preferably 5 minutes or longer.

  As shown in Patent Document 1, the organosilane thin film conventionally used for improving the orientation of organic semiconductor molecules in a thin film transistor is a crystalline organosilane thin film. On the other hand, the organosilane thin film used in the thin film transistor of the present invention is an amorphous organosilane thin film.

  Therefore, the orientation and crystallinity of the organic semiconductor film formed on this amorphous organosilane thin film is different from the organic semiconductor film formed on the conventional crystalline organosilane film. According to this, it is possible to develop characteristics that could not be obtained with conventional organic semiconductor films. More specifically, as described above, an organic semiconductor film formed on an amorphous organosilane thin film unexpectedly has a semiconductor property close to or corresponding to a highly oriented organic semiconductor film, particularly charge mobility. And variation in semiconductor characteristics due to the in-plane orientation direction is small.

<Thin film transistor-organic semiconductor film>
The organic semiconductor film of the thin film transistor of the present invention means a semiconductor film composed of an aggregate of organic semiconductor molecules. For example, Patent Documents 1 and 2 and Non-Patent Documents 1 to 4 such as regioregular polyalkylthiophene (P3AT). An organic semiconductor film as shown in FIG.

  Accordingly, organic semiconductor molecules that can be used in the thin film transistor of the present invention include, for example, low molecular organic semiconductor molecules such as pentacene and acene compounds including thiophene oligomers (condensed polycyclic compounds condensed linearly), regio And high molecular organic semiconductor molecules such as regular polyalkylthiophene (P3AT) and poly (fluorenebithiophene) (F8T2).

  The organic semiconductor film of the thin film transistor of the present invention can have any thickness that can form a thin film transistor, and can have a thickness of, for example, 0.5 nm to 1 μm, or 2 nm to 250 nm. The organic semiconductor film can be obtained by an arbitrary method such as a molecular beam deposition method (MBE method), a vacuum deposition method, a chemical vapor deposition method, or a solution method. Among these, a solution method, for example, a dipping method, a spin coating method, an ink jet printing method, etc. may be preferable in terms of productivity.

<Thin film transistor electrode>
The source electrode, the drain electrode, and the gate electrode of the thin film transistor of the present invention can be manufactured using any material having sufficient conductivity to be used as an electrode. Therefore, the electrode can be made of a metal such as gold, silver, copper, nickel, chromium, and aluminum, a conductive resin, a conductive metal oxide, or the like. The thickness of the electrode can be determined based on required conductivity, flexibility, and the like.

<Thin film transistor-other layers>
The thin film transistor of the present invention can have, for example, a protective layer, particularly a protective film formed on the organic semiconductor film, even if it has any other layer other than the above structure. Such a protective layer can be formed of, for example, polyparaxylylene.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example and a comparative example, this invention is not limited to this. In addition, the material and evaluation method which were used by the Example and the comparative example are as follows.

Silicon substrate:
An n-type silicon wafer with a 300 nm thermal oxide film (plane orientation <100>, specific resistance 1 to 10Ω) was treated with hot concentrated sulfuric acid for 30 minutes, and then several times using pure water, acetone, toluene, and hexane. Ultrasonic cleaning was performed twice. Furthermore, what was cleaned for 30 minutes with a UV ozone cleaning apparatus was used as a substrate.

Stamp material:
A Sylgard 184 made by Toray Dow Corning was cured into a flat plate shape to obtain a stamp material made of polydimethylsiloxane, which was used.

Organic thin film thickness:
Measurement was performed at an incident angle of 70 degrees using a M-150 ellipsometer manufactured by JASCO Corporation. The refractive index of the organic thin film was calculated as n = 1.45.

Contact angle:
Using a contact angle meter CA-X manufactured by Kyowa Interface Science, measurement was performed with pure water.

Critical surface energy:
The contact angle was measured using a wetting index standard solution (JIS K 6768) having a critical surface energy of 30 mN / m, 35 mN / m, 40 mN / m, and 50 mN / m, and obtained by a zisman plot.

In-plane X-ray diffraction:
A RTX ATX-G multifunction X-ray diffractometer was used. Using CuKα rays, the measurement was performed at an incident angle of 0.2 degrees and a measurement interval of 0.02 degrees under the condition of 50 kV-300 mA.

Surface roughness and protrusions:
The surface roughness was measured in a 20 μm square visual field using a SPA400-DMF apparatus (atomic force microscope: AFM) manufactured by SII Nanotechnology.

Charge mobility:
The charge mobility of the organic semiconductor film was evaluated using a 4200-SCS type semiconductor evaluation apparatus manufactured by Keithley. The standard deviation of charge mobility was calculated by evaluating the characteristics of 10 or more elements.

Rocking curve measurement:
A RINT TTR III sample horizontal type strong X-ray diffraction measurement device manufactured by Rigaku was used, and Cu-Kα and rotating counter cathode 50 kV-300 mA were used as an X-ray source. It was fixed at 2θ = 5.2 ° and measured in increments of 0.01 °.

<Example 1>
(Preparation of organosilane thin film (contact printing method in nitrogen))
A 20 mM hexane solution of octadecyltrichlorosilane was prepared. The stamp material was immersed in the obtained octadecyltrichlorosilane solution and dried in nitrogen for 10 minutes.

  The dried stamp was brought into contact with the silicon substrate and held for 30 minutes. After removing the stamp, the substrate was washed with hexane and ethanol, and ultrasonically washed in ethanol for 30 minutes. All the steps so far were performed in a nitrogen atmosphere in a glove box whose humidity was controlled to 3% or less.

  Thereafter, the substrate was washed with pure water and heat-treated at 100 ° C. for 5 minutes to produce a substrate having an octadecylsilane thin film (ie, organosilane thin film).

  Table 1 shows the film thickness, contact angle, and surface roughness of the resulting organosilane thin film. Moreover, the result of the in-plane X-ray diffraction of the obtained organosilane thin film is shown in FIG.

(Preparation of organic semiconductor film)
A solution for spin coating by dissolving 1 part by mass of regioregular poly (3-hexylthiophene) ("P3HT") (sold by Aldrich, manufactured by Prectronics, MW = 25000-35000, electronics grade) in 99 parts by mass of toluene Got. Using this spin coating solution, a P3HT film (that is, an organic semiconductor film) was spin coated (1800 rpm, 20 seconds) on the substrate having the organosilane thin film.

  The rocking curve of this organic semiconductor film is shown in FIG.

(Production of thin film transistor)
Gold was vacuum-deposited on the obtained organic semiconductor film by a mask vapor deposition method to form a source electrode and a drain electrode (L / w = 50 μm / 1.5 mm), and a thin film transistor was obtained using a silicon substrate as a gate electrode. . That is, a thin film transistor having a structure as shown in FIG. 5 was obtained.

  Table 1 shows the charge mobility and the standard deviation of the obtained thin film transistor.

<Comparative example 1>
(Preparation of organosilane thin film (liquid phase method))
A 20 mM toluene solution of octadecyltrichlorosilane was prepared. The silicon substrate was immersed in the obtained octadecyltrichlorosilane solution and held for 72 hours. After immersion, the substrate was washed with toluene and ethanol, and ultrasonically washed in ethanol for 30 minutes. All the steps so far were performed in a glove box in which the humidity was controlled to 3% or less.

  Thereafter, the substrate was washed with pure water and heat-treated at 100 ° C. for 5 minutes to produce an organosilane thin film.

  Table 1 shows the film thickness, contact angle, and surface roughness of the resulting organosilane thin film. Moreover, the result of the in-plane X-ray diffraction of the obtained organosilane thin film is shown in FIG.

(Production of organic semiconductor film and thin film transistor)
In the same manner as in Example 1, an organic semiconductor film and a thin film transistor were produced and evaluated.

  The rocking curve of this organic semiconductor film is shown in FIG. In addition, Table 1 shows the charge mobility and the standard deviation of the obtained thin film transistor.

<Comparative example 2>
(Preparation of organosilane thin film (contact printing method in air))
In the same manner as in Example 1, the stamp immersed in the octadecyltrichlorosilane solution was dried in nitrogen for 10 minutes.

  The dried stamp was brought into contact with the silicon substrate and held for 1 minute. After removing the stamp, the substrate was washed with hexane and ethanol, and ultrasonically washed in ethanol for 30 minutes. Here, the step of bringing the stamp into contact with the silicon substrate and the subsequent cleaning step were performed in the atmosphere (humidity of about 60%).

  Thereafter, the substrate was washed with pure water and heat-treated at 100 ° C. for 5 minutes to produce a substrate having an octadecylsilane thin film (ie, organosilane thin film).

  Table 1 shows the film thickness, contact angle, and surface roughness of the resulting organosilane thin film. Moreover, the result of the in-plane X-ray diffraction of the obtained organosilane thin film is shown in FIG.

  As shown in FIG. 6, the X-ray diffraction results of the organosilane thin films of Comparative Examples 1 and 2 show peaks due to the crystal structure, both of which are crystalline, whereas In the X-ray diffraction result of the organosilane thin film, the peak due to the crystal structure does not appear and is controlled to be amorphous. As shown in FIG. 7, the rocking curve peak for the organic semiconductor film of the example is small as compared with the peak of the rocking curve for the organic semiconductor film of the comparative example 1. Therefore, in the organic semiconductor film of the example, as shown in FIG. The orientation of the organic semiconductor film is low.

  As shown in Table 1, the organosilane thin film of the example was compared with the organosilane thin film of Comparative Examples 1 and 2 formed by the liquid phase method and the contact printing method using the same raw materials, respectively. It is a film having low roughness and thus excellent flatness. Moreover, the organosilane thin film of an Example has a small critical surface energy compared with the organosilane thin film of the comparative example 1 formed into a film by the liquid phase method using the same raw material. Furthermore, the organic semiconductor film of the example has charge mobility corresponding to that of the organic semiconductor film of Comparative Example 1 although the orientation is low.

  That is, in the thin film transistor of the example, excellent charge mobility is achieved while controlling the orientation of the organic semiconductor film low. Further, in the thin film transistor of the example, since the orientation of the organic semiconductor film is small, variation in device characteristics due to the variation in the orientation direction is small. Therefore, as shown in Table 1, the standard deviation of the charge mobility is Comparative Example 1. About half of that.

10, 20, 30, 40, 50, 60 Thin film transistor Arm Amorphous organosilane thin film G Gate electrode Ins Gate insulating film S Source electrode Semi Organic semiconductor film Sub substrate

Claims (11)

A source electrode, a drain electrode, a gate electrode, a gate insulating film, and an organic semiconductor film on one surface of the substrate; the source electrode, the drain electrode, and the gate electrode are insulated by the gate insulating film; and A thin film transistor that controls a current flowing through the organic semiconductor from the source electrode to the drain electrode by a voltage applied to a gate electrode;
The substrate or gate insulating film has a hydroxyl group on the surface, the thin film transistor further has an amorphous organosilane thin film, and the amorphous organosilane thin film has a hydroxyl group on the surface A thin film transistor which is directly formed on the organic semiconductor film and is formed directly on the amorphous organosilane thin film.   The thin film transistor according to claim 1, wherein an average thickness of the amorphous organosilane thin film is 10 nm or less.   The thin film transistor according to claim 1 or 2, wherein a roughness Ra of the amorphous organosilane thin film is 3 nm or less.   4. The thin film transistor according to claim 1, wherein the amorphous organosilane thin film does not have a protrusion having a height of 30 nm or more.   The thin film transistor according to claim 1, wherein the amorphous organosilane thin film contains a siloxane oligomer.   The thin film transistor according to claim 1, wherein the amorphous organosilane thin film has a critical interface energy value of 10 to 30 mN / m.   The thin film transistor according to claim 1, wherein the amorphous organosilane thin film is a trichloroorganosilane thin film or a trialkoxyorganosilane thin film.   The thin film transistor according to claim 1, wherein a surface having a hydroxyl group of the substrate or the gate insulating film is provided by silica.   The thin film transistor according to claim 1, wherein a surface of the substrate or the gate insulating film having a hydroxyl group is provided by a silica layer laminated on a polymer substrate.   The thin film transistor according to claim 1, wherein a protective film is laminated on the organic semiconductor film.   The thin film transistor according to any one of claims 1 to 10, comprising forming the organosilane thin film on the substrate having a hydroxyl group on the surface or the gate insulating film by a contact printing method in an atmosphere having a humidity of 10% or less. How to manufacture.

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