JP2008171978A - Organic thin film transistor - Google Patents

Abstract

【選択図】なしAn organic thin film transistor having high mobility and good transistor characteristics that can be manufactured by a solution process with high production efficiency using a self-assembled monomolecular film, and a method for manufacturing the same.
An organic thin film transistor having a gate electrode, a gate insulating film, a semiconductor layer made of an organic semiconductor material, a source electrode, and a drain electrode, wherein the first functional group is decomposable to light or acid on the gate insulating film. Forming a first self-assembled monolayer made of a compound having a chemical reaction, exposing the monolayer to actinic rays, decomposing the monolayer and exposing a second functional group to the exposed portion A monomolecule having a third functional group formed by a step of reacting a compound of the following general formula (1) with the second functional group to form a third functional group on the monomolecular film. An organic thin film transistor comprising a film on a gate insulating film.
[Chemical 1]

[Selection figure] None

Description

  The present invention relates to an organic thin film transistor using an organic semiconductor film and a manufacturing method thereof.

  With the widespread use of information terminals, there is an increasing need for flat panel displays as computer displays. In addition, with the progress of computerization, the information that has been provided in paper media has been increasingly digitized. As a mobile display medium that is thin, light, and easy to carry, it has become electronic paper or digital paper. Needs are growing.

  In general, in a flat panel display device, a display medium is formed using elements utilizing liquid crystal, organic EL (organic electroluminescence), electrophoresis, or the like. In such a display medium, an active driving method using a thin film transistor element (TFT element) has become mainstream as an image driving method in order to ensure uniformity of screen luminance, screen rewriting speed, and the like. For example, in a normal computer display, these TFT elements are formed on a glass substrate, and liquid crystal, organic EL elements, etc. are sealed.

  Here, a semiconductor such as a-Si (amorphous silicon), p-Si (polysilicon) or the like is mainly used for the TFT element, and these Si semiconductors (and metal films as necessary) are multilayered, and the source, The TFT element is manufactured by sequentially forming the drain and gate electrodes on the substrate. The manufacture of such TFT elements usually requires sputtering or other vacuum manufacturing processes.

  However, in these Si-based TFT elements, it is necessary to form a large number of layers so that a plurality of semiconductor layers such as p-type and n-type are stacked only on the semiconductor layer that is necessary for the switching operation. Since a vacuum manufacturing process including a vacuum chamber is required to form the film, the apparatus cost and running cost are extremely enormous. Furthermore, it is necessary to pattern the layer formed by these vacuum manufacturing processes by means such as photolithography, and in this patterning process, it is necessary to perform a number of steps such as exposure, development, and washing, and as a result In order to form the element on the substrate, dozens of processes are required. In such a conventional manufacturing method using a Si semiconductor, it is not easy to change the equipment, for example, a design change of a manufacturing apparatus such as a vacuum chamber is required in response to the need for a large display screen.

  Further, since the formation of such a conventional TFT element using a Si material includes a high temperature process, the base material is restricted to be a material that can withstand the process temperature. Therefore, in practice, glass must be used, and when the above-described thin display such as electronic paper or digital paper is configured using such a conventionally known TFT element, the display is heavy and flexible. Products that may break due to chipping or dropping impact. These characteristics resulting from the formation of Si-based TFT elements on a glass substrate are undesirable in satisfying the need for an easy-to-carry-type thin display with the progress of computerization.

  On the other hand, in recent years, organic semiconductor materials have been energetically studied as organic compounds having high charge transport properties. In addition to charge transport materials for organic EL devices, these compounds are expected to be applied to, for example, organic laser oscillation devices and organic thin film transistor devices (organic TFT devices) reported in many papers.

  Materials that have been studied as semiconductor layers so far include acenes such as pentacene and tetracene, compounds having substituents introduced thereto, phthalocyanines and porphyrins, and precursors thereof, perylene and its tetracarboxylic acid derivatives, etc. Low molecular weight compounds, aromatic oligomers such as thiophene hexamers called α-thienyl or sexithiophene, compounds obtained by symmetrically condensing 5-membered aromatic heterocycles with naphthalene and anthracene, mono, oligo and polydithienopyridines Furthermore, conjugated polymers such as polythiophene, polythienylene vinylene, and poly-p-phenylene vinylene can be used.

  If a device in which such an organic material is a semiconductor layer can be realized, it may be possible to manufacture by vacuum or low pressure deposition at a low temperature. Manufacturing by such a low temperature process makes it possible to form TFT elements on a transparent resin substrate, making the display lighter and more flexible than conventional ones, and not broken (or very difficult to break) when dropped. It is thought that it can be.

  Furthermore, if it can be solubilized in a solvent by appropriately improving the molecular structure of these organic semiconductor materials, patterning is possible by a simple solution process such as an ink jet method or a printing method, and exposure and development associated with photolithography -It is expected that a number of processes such as washing can be reduced and a display can be manufactured by a simple process.

  By the way, in these TFT elements, it is said that carriers pass through the interface between the insulating film and the organic semiconductor layer, and if there is a carrier trap at the interface of the insulating film through which the carrier passes, there is a problem that the carrier mobility is lowered. In order to avoid this, many attempts have been made to improve the carrier mobility by coating the surface of the gate insulating film with a silane coupling agent or the like.

  However, this method has a problem that the organic semiconductor solution is repelled when the source / drain electrodes and the organic semiconductor layer are formed by a coating method, and the desired region (between the source electrode and the drain electrode) is generated. ) Has a problem that the organic semiconductor layer cannot be formed successfully.

In Patent Document 1 and Non-Patent Document 1, a self-assembled monomolecular film made of a silane coupling agent is formed only on the gate electrode (on the channel formation region) using the backside exposure method, and the source / drain electrodes are formed. Although a method of forming by an application method is disclosed, the organic semiconductor layer is formed by vapor deposition of pentacene having no solvent solubility, and there is no mention of forming the organic semiconductor layer by application. In such a method, octadecyltrichlorosilane, which has a low surface energy and is difficult to wet, is formed between the source and drain electrodes, and a silicon oxide surface that has a high surface energy and is easily wetted except between the source and drain electrodes. Forming an organic semiconductor layer between electrodes by a coating method has been a difficult structure.
JP 2005-79560 A The 67th JSAP Proceedings No. 3, p1210, 29a-ZH-5

  An object of the present invention is to provide an organic thin film transistor having high mobility and good transistor characteristics that can be produced by a solution process with high production efficiency using a self-assembled monolayer (SAM film), and a method for producing the same. There is to do.

  The above object of the present invention can be achieved by the following configuration.

1. An organic thin film transistor having a gate electrode, a gate insulating film, a semiconductor layer made of an organic semiconductor material, a source electrode, and a drain electrode,
Forming a first self-assembled monolayer made of a compound having a first functional group decomposable by light or acid on the gate insulating film;
Pattern exposure of actinic rays on the self-assembled monolayer, decomposing the self-assembled monolayer, and exposing a second functional group on the self-assembled monolayer at the exposed site;
A step of reacting the second functional group with a compound represented by the following general formula (1) to form a third functional group on the self-assembled monolayer;
An organic thin film transistor comprising a self-assembled monomolecular film having a patterned third functional group, formed by the above, on a gate insulating film.

(In the formula, Q represents a tetravalent atom selected from C, Si, Ge, Sn, and Pb, A represents a group that can be bonded to the second functional group, L ₁ represents a single bond, an alkylene group, cyclo A divalent linking group selected from an alkylene group, an alkene-1,2-diyl group, an alkyne-1,2-diyl group, and an arylene group, or an ether group, a thio group, a carbonyl group, or a carbonyloxy group. Represents a divalent linking group selected from a divalent linking group linked to Z. R _{1 to} R ₃ are an alkyl group, a halogenated alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, and an aryl group. Represents a substituent selected from a heteroaryl group and an alkylsilyl group, which may be linked to each other to form a ring.
2. 2. The organic thin film transistor according to 1 above, wherein a semiconductor layer made of the organic semiconductor material is formed on a self-assembled monomolecular film having the third functional group.

  3. 1 or 2, wherein the surface energy E3 of the self-assembled monolayer having the third functional group is larger than the surface energy E1 of the self-assembled monolayer having the first functional group. The organic thin-film transistor as described.

  4). 4. The organic thin film transistor according to any one of 1 to 3, wherein the atom represented by Q in the general formula (1) is a silicon atom.

  5. 5. The organic thin film transistor according to any one of 1 to 4, wherein the functional group capable of binding to the second functional group represented by A is an amino group.

  6). The first self-assembled monolayer that is decomposed by the actinic ray is a self-assembled monolayer formed by a silane coupling agent represented by the following general formula (2): 6. The organic thin film transistor according to any one of 1 to 5 above.

(Wherein, Z is oxygen, sulfur, selenium, represents a chalcogen atom selected from tellurium, L ₂ is a single bond, an alkylene group, a cycloalkylene group, an alkene-1,2-diyl group, alkyne diyl A divalent linking group selected from a group, an arylene group, or a divalent linking group selected from these groups, and a divalent linking group linked to Z via an ether group, a thio group, a carbonyl group, or a carbonyloxy group. R ₄ and R ₅ are selected from a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group, a halogenated aryl group, a heteroaryl group, and an alkylsilyl group. X represents a hydrolyzable substituent selected from a halogen atom, an alkoxy group, and an isocyanate group, and m and n represent an integer of 1 to 3).
7). 7. The organic thin film transistor according to 6 above, wherein the substituent represented by R ₅ in the general formula (2) is a halogenated alkyl group.

  8). 8. The organic thin film transistor according to any one of 1 to 7, wherein the semiconductor layer is formed by coating.

  9. 9. The organic thin film transistor according to any one of 1 to 8, wherein the semiconductor layer is a pentacene derivative.

  According to the present invention, an organic thin film transistor with high mobility and good transistor characteristics can be manufactured by a solution process with high production efficiency using a self-assembled monolayer.

  The present invention will be described in more detail.

  The organic thin film transistor of the present invention is an organic thin film transistor having a gate electrode, a gate insulating film, a semiconductor layer made of an organic semiconductor material, a source electrode, and a drain electrode, and is produced by the following steps.

That is, the organic thin film transistor of the present invention is
1. 1. forming a first self-assembled monolayer made of a compound having a first functional group decomposable with respect to actinic rays (or acid) on a gate insulating film; A step of pattern-exposing active light on the formed self-assembled monolayer, decomposing the self-assembled monolayer, and exposing a second functional group on the self-assembled monolayer at the exposed site 3. The second functional group is formed by a step of reacting a compound represented by the following general formula (1) to form a third functional group on the self-assembled monolayer, and is patterned. A self-assembled monomolecular film having a third functional group is provided over the gate insulating film.

  Here, the self-assembled film refers to a compound having a functional group capable of binding to constituent atoms on the film forming surface (for example, a compound in which the functional group is bonded to a trichlorosilyl group) in a gas or liquid state. By coexisting with the formation surface, the functional group is a dense monomolecular film formed by adsorbing or binding to the constituent atoms of the film formation surface and directing the straight-chain molecules outward. This monomolecular film is referred to as a self-assembled film because it is formed by spontaneous chemical adsorption on the film forming surface of the compound.

  Regarding the self-assembled film, A.I. Chapter 3 of "An Introduction to Ultrathin Organic Film from Langmuir-Blodgett to Self-Assembly" by Ulman (Academic Press Inc. Boston, 1991).

  In the present invention, the surface state of the substrate is adjusted by forming such a self-assembled monolayer. That is, the affinity with the thin film forming material on the substrate is adjusted by forming a self-assembled monolayer.

  In the present invention, a self-assembled monolayer is disposed on the surface of the gate insulating film, and an organic semiconductor material layer, a source electrode, a drain electrode, and the like are disposed at a position aligned with the gate electrode. It is formed with high accuracy.

  Hereinafter, a method for forming a self-assembled monomolecular film of the present invention on a gate insulating film and patterning a thin film such as an organic semiconductor material layer will be described.

  The present invention is exemplified by a substrate in which a gate electrode 2 made of chromium (film thickness 140 nm) and an insulating film 3 made of silicon oxide film (400 nm) are laminated on a substrate 1 made of glass (quartz), for example. explain.

  In the present invention, first, a first self-assembled monolayer made of a compound having a first functional group that is decomposable to light or acid is formed on the gate insulating film.

  As the gate insulating film, a metal oxide such as tantalum oxide, zirconium oxide, lanthanum oxide, or titanium oxide is used as an inorganic material in addition to silicon oxide. Therefore, a hydroxyl group exists on the surface and is chemisorption activity. Therefore, as a compound capable of forming a self-assembled monolayer having a first functional group decomposable with respect to light or acid, a compound having a group reactive with these surfaces is used. These functional groups are, for example, a halogenosilyl group, an alkoxysilyl group, or an isocyanate group, and may be any functional group having reactivity with the surface.

  These compounds capable of forming a first self-assembled monolayer include a first functional group that is decomposed by light or acid, and a group that is reactive with the film surface to form a self-assembled monolayer. If it is a compound which has simultaneously, it will not be limited. In the case of a self-assembled monolayer that is decomposed by an acid, patterning can be performed substantially with light because a photoacid generator is present in the vicinity. A self-assembled monolayer that directly decomposes with light is preferable because the process is simple.

  As functional groups that are directly decomposed by light, for example, 2,2-dimethyl-1,3-dioxin group, nitrobenzyl group and the like are known.

  Since the first self-assembled monolayer has a functional group in the constituent molecules that is decomposed by light or acid, in addition to the adsorption site with the substrate, the formed first self-assembled monomolecule By pattern exposure of actinic rays on the film, the first functional group in the self-assembled monolayer is decomposed to expose the second functional group at the exposed site. For example, in the case of the aforementioned 2,2-dimethyl-1,3-dioxin group, an acrolein group can be formed, and in the case of a nitrobenzyl group, a carboxylic acid residue, a sulfonic acid residue or the like can be exposed.

  Among these photoreactive functional groups, it is possible to use a self-assembled monolayer composed of a silane coupling agent having a nitrobenzyl group that has a relatively long photosensitive wavelength and can use a general-purpose inexpensive light source. preferable. That is, the first self-assembled monolayer is preferably formed of a silane coupling agent represented by the general formula (2).

  First, the silane coupling agent represented by the general formula (2) will be described.

In the general formula (2), Z represents a chalcogen atom selected from oxygen, sulfur, selenium and tellurium, L ₂ represents a single bond, an alkylene group, a cycloalkylene group, an alkene-1,2-diyl group, an alkyne. A divalent linking group selected from a -1,2-diyl group and an arylene group, or a divalent linking group linked to Z via an ether group, a thio group, a carbonyl group or a carbonyloxy group, Represents. R ₄ represents an alkyl group, a halogenated alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group, a heteroaryl group, a substituent selected from alkyl silyl group. X represents a hydrolyzable substituent selected from a halogen atom, an alkoxy group, and an isocyanate group. n represents an integer of 1 to 3.

  Z is particularly preferable because oxygen and sulfur are rich in reactivity.

As alkylene group, cycloalkylene group, alkene-1,2-diyl group, alkyne-1,2-diyl group, alkyl having 1 to 22 carbon atoms, cycloalkyl, alkene-1,2-diyl group, alkyne- A 1,2-diyl group is preferred. Moreover, as an arylene group, a phenylene group and a naphthylene group are mentioned, A phenylene group is preferable. In addition, these alkylene groups, cycloalkylene groups, alkene-1,2-diyl groups, alkyne-1,2-diyl groups, and arylene groups are further substituted with groups represented by R ₄ described later. May be.

  As the halogen atom represented by X, a chloro group is preferable. The alkoxy group is an alkoxy group having 1 to 4 carbon atoms, particularly preferably a methoxy group or an ethoxy group. m and n are integers of 1 to 3. The position at which the nitro group is substituted may be any of the ortho position, meta position, and para position, but preferably has a nitro group at either the ortho position or the para position in view of photosensitivity.

The alkyl group, halogenated alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, and alkylsilyl group represented by R ₄ and R ₅ are specifically alkyl groups (for example, methyl group, ethyl group, etc.). Propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.), halogenated alkyl group (for example, trifluoromethyl group, 1,1 , 1-trifluoropropyl group etc.), alkenyl group (eg vinyl group, allyl group etc.), alkynyl group (eg ethynyl group, propargyl group etc.), cycloalkyl group (eg cyclopentyl group, cyclohexyl group etc.), Aryl group (for example, phenyl group, p-chlorophenyl group, mesityl group, tolyl) , Xylyl group, naphthyl group, anthryl group, azulenyl group, acenaphthenyl group, fluorenyl group, phenanthryl group, indenyl group, pyrenyl group, biphenylyl group, etc.), halogenated aryl group (pentafluorophenyl group, pentachlorophenyl group, etc.), hetero Aryl groups (eg, furyl, thienyl, pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, imidazolyl, pyrazolyl, thiazolyl, quinazolinyl, phthalazinyl, etc.), alkylsilyl groups (eg, trimethylsilyl) Groups, triethylsilyl groups, tripropyl (i or n) silyl groups, tributyl (i, t or n) silyl groups, etc.), and these substituents may be further substituted by the above substituents. Combine to form a ring It may be made. Moreover, it is preferably a linear, branched or cyclic alkyl group.

Among these, R ₄ is preferably a hydrogen atom or a methyl group in order to increase photosensitivity. In order to prevent the organic semiconductor layer from being repelled on the self-assembled monolayer pattern having the third substituent, the self-assembled monolayer pattern having the third substituent The adjacent first self-assembled monolayer pattern preferably has a lower surface energy, and is a linear alkyl group such as an octyl group or a dodecyl group, a trifluoromethyl group, a trifluoropropyl group, or a perfluoro group. A fluorinated alkyl group such as an alkyl group and a fluorinated aryl group such as a pentafluorophenyl group are preferred, and among them, a fluorinated alkyl group is preferably used.

  Specific examples of the compound include the following compounds. These compounds are described in J. Org. Am. Chem. Soc. , Vol. 126 (2004), p16314, Polymer Science Society Proceedings Vol. 52-No. 11 (2003) p2660, Proceedings of the Society of Polymer Science, Vol. 55-No. 2 (2006) p3953 and the like can be synthesized by reference.

  The first self-assembled monolayer (SAM film) formed of the compound represented by the general formula (2) is decomposed by the first functional group having photodegradability by irradiation with actinic rays. A second functional group is generated. An example is schematically shown below.

  The generated second functional group (-ZH) reacts and binds to a compound having a group capable of binding to the second functional group, for example, a compound represented by the general formula (1) (described later). Thus, a new third functional group is formed.

  When the first self-assembled monolayer is exposed to light pattern by a photolithography method using a resist and a mask pattern, a second functional group is generated in the light irradiated portion. Specifically, the end of one self-assembled monolayer is a group such as a carboxyl group, a hydroxy group, or a mercapto group.

  In the present invention, the second functional group is formed by the decomposition of the first functional group in the first self-assembled monolayer (SAM film) by light pattern exposure, but then generated by light irradiation. The second functional group and the compound represented by the general formula (1) are reacted to form a third functional group on the self-assembled monolayer.

  The third functional group is a group that forms a surface having good wettability and high affinity for an organic semiconductor material or a material solution described later.

  Next, the compound represented by the general formula (1) that reacts with the second functional group to form a third functional group will be described.

In general formula (1), A represents a group that can be bonded to the second functional group. L ₁ is a single bond, an alkylene group, a cycloalkylene group, an alkene-1,2-diyl group, an alkyne-1,2-diyl group, an arylene group, or an ether group in these groups. , A divalent linking group selected from a divalent linking group linked to Z via a thio group, a carbonyl group, or a carbonyloxy group. R _{1 to} R ₃ each represents a substituent selected from an alkyl group, a halogenated alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group, a heteroaryl group, and an alkylsilyl group, and is linked to each other to form a ring. May be.

In the general formula (1), A represents a group capable of binding to the second functional group formed by the decomposition of the decomposable group in the silane coupling agent represented by the general formula (2). Is represented by the general formula (1) which reacts with the second functional group generated by the structure of the decomposable group in the silane coupling agent represented by the general formula (2). The group A in the compound also changes. For example, when -L ₂ -Z- constitutes a carbonyloxy group, ie, —CO—O— group, the silane coupling agent represented by the general formula (2) is decomposed to become a carboxyl group. Examples of the group that reacts with the functional group 2 include an amino group, and, for example, when a hydroxy group, a mercapto group, or the like is generated as the second functional group, for example, a terminal vinyl compound, an alkylalkoxysilane, or an alkyl group. Examples include halogenosilane. Moreover, an isocyanate group etc. are mentioned.

Therefore, A cannot be generally limited, but in the present invention, in the general formula (1), L ₂ is — (CH ₂ ) _n —C (═O) — (n = 1 to 10), and Z is An oxygen atom is preferred. In this case, a carboxyl group is generated by elimination of the nitrobenzyl group. In such a case, a preferred example of the group A in the general formula (1) is an amino group.

  When the compound represented by the general formula (1) has a functional group that reacts with the second functional group generated by the decomposition of the first self-assembled monolayer, the first self-assembled single molecule is obtained. As described above, the molecular film can form a coating layer composed of different self-assembled monolayers having the third functional group.

In general formula (1), the alkylene group, cycloalkylene group, alkene-1,2-diyl group, and alkyne-1,2-diyl group represented by L ₁ preferably have 1 to 22 carbon atoms. The arylene group is preferably a phenylene group such as a phenylene group or a naphthalene group. Further, these substituents may be further substituted with a substituent described later.

Q represents a tetravalent atom selected from C, Si, Ge, Sn, and Pb. R _{1 to} R ₃ represent a substituent selected from a substituted or unsubstituted alkyl group, a halogenated alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group, a heteroaryl group, and an alkylsilyl group, and are connected to each other. May form a ring.

  Specifically, an alkyl group (for example, methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.), Halogenated alkyl group (for example, trifluoromethyl group, 1,1,1-trifluoropropyl group, etc.), alkenyl group (for example, vinyl group, allyl group, etc.), alkynyl group (for example, ethynyl group, propargyl group, etc.) , Cycloalkyl groups (for example, cyclopentyl group, cyclohexyl group, etc.), aryl groups (for example, phenyl group, p-chlorophenyl group, mesityl group, tolyl group, xylyl group, naphthyl group, anthryl group, azulenyl group, acenaphthenyl group, fluorenyl group) Group, phenanthryl group, indenyl group, pyrenyl group, bif Nitryl group, etc.), heteroaryl group (for example, furyl group, thienyl group, pyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, triazinyl group, imidazolyl group, pyrazolyl group, thiazolyl group, quinazolinyl group, phthalazinyl group, etc.), alkyl A silyl group (for example, a trimethylsilyl group, a triethylsilyl group, a tripropyl (i or n) silyl group, a tributyl (i, t or n) silyl group, etc.), these substituents are further substituted by the above substituents Alternatively, a plurality of them may be bonded to each other to form a ring. Moreover, it is preferably a linear, branched or cyclic alkyl group.

  A conventional electrode surface treatment agent having a linear alkyl group or an aryl group forms a coating layer having a relatively high film density, whereas a SAM film in which a compound represented by the general formula (1) is reacted is Since the terminal portion is three-dimensionally bulky, a coating layer having a low film density can be formed. Although details are unknown, by forming such a coating layer between the gate insulating layer and the organic semiconductor layer, the carrier trap density at the interface between the insulating film and the organic semiconductor layer is reduced, and it has good characteristics. It is estimated that an organic thin film transistor is obtained. In addition, when an organic solvent-based solution is applied, there is an effect that the solvent is less likely to be repelled than a coating layer formed from a surface treatment agent having a linear alkyl group or an aryl group. Furthermore, by utilizing the difference in the coating properties of these solvents, the organic semiconductor layer can be formed with high accuracy by solvent coating.

In the general formula (1), more preferably, the atom represented by Q is a silicon atom. A silicon atom is an atom larger than carbon, can easily form a bulky end, and can form a coating layer having a lower film density. Further, atoms larger than silicon tend to be unstable in bonding with a substituent represented by R _{1 to} R ₃ or a linking group represented by L 1.

  Hereinafter, although the preferable specific example of a compound represented by General formula (1) of this invention is shown, this invention is not limited to these.

  As for these compounds, all of the above compounds are known compounds, or can be obtained by using known reactions.

  As described above, the first self-assembled monolayer (SAM film) is formed on the substrate surface by treating the substrate surface with the silane coupling agent represented by the general formula (2), and the second functional group is formed by light exposure. The process of forming a new SAM film by exposing the group and reacting it with the compound represented by the general formula (1) has been described.

  As a method for measuring the surface energy of the self-assembled monomolecular film (SAM film) used in the present invention, a method for measuring the contact angle of pure water can be used as a simple method. This contact angle is measured under an environment of 20 ° C. and 50% RH using a contact angle meter (CA-DT • A type: manufactured by Kyowa Interface Science Co., Ltd.).

  In the present invention, the contact angle of water on the surface of the channel formation region between the source and drain electrodes (the surface on which the third functional group is formed) is preferably 50 to 100 degrees, more preferably 70 to 95. Degree, more preferably 80-90. When the contact angle is low, the carrier mobility and on / off ratio of the transistor element are remarkably reduced. When the contact angle is too high, the solution containing the organic semiconductor material is easily repelled when the organic semiconductor layer is formed.

  Further, the contact angle of the region other than between the source and drain electrodes (region having the first functional group) is preferably 1 degree or more larger than the contact angle of the region having the third functional group, more preferably 10 More than 15 degrees, more preferably 15 degrees or more. With such a surface energy relationship, the organic semiconductor solution can be applied with high precision between the desired source / drain electrodes.

  The compound forming the SAM film according to the present invention can be used by mixing with other surface treatment agents. Examples of other surface treatment agents include alkyltrichlorosilane and alkyltrialkoxysilane.

  The thickness of the coating layer formed by the silane coupling agent that forms the first SAM film according to the present invention is preferably in the range of 0.5 to 20 nm, more preferably 0.7 to 10 nm, and still more preferably 1. 0.0 to 3.0 nm.

  The surface roughness Ra of the surface of the gate insulating film formed by the SAM film is largely influenced by the surface properties of the substrate, the gate electrode, and the gate insulating film when the thin film transistor is a bottom gate type described later. The thickness is preferably 10 nm to 10 nm from the viewpoint of carrier mobility of the transistor element.

  The method for forming a self-assembled monolayer (SAM film) of the present invention includes the silane coupling agent represented by the general formula (2), which forms the first self-assembled monolayer. For example, spin coating method, screen printing method, ink jet printing method, air doctor coater method, blade coater method, rod coater method, knife coater method, squeeze coater method, reverse roll coater method, transfer roll coater method, gravure coater method Coating on the surface of gate insulating film using various solution processes such as kiss coater method, cast coater method, spray coater method, slit orifice coater method, calender coater method, dipping method, spray method, dripping method, Langmyer / Blodgett method, etc. And forming by washing and drying It can be.

  Further, as a method of patterning the first self-assembled monomolecular film (SAM film) of the present invention according to the organic semiconductor thin film pattern, light shielding is directly performed on the insulating film by a resist using a known photolithography method or lift-off method. A known method such as a method of forming a layer and performing light exposure, a method of irradiating light through a mask pattern formed of chromium or the like, or a method of scanning with a laser can be used. Patterning can be performed with a clear boundary, high positional accuracy and high reproducibility. Among these, the mask exposure method is preferable because it is simple and efficient.

  In this way, the first SAM film is subjected to pattern exposure to decompose the decomposable group in the SAM film to expose the second functional group, and further, another compound is reacted therewith to newly add a third functional group. By forming the group on the SAM film, regions having different surface energies can be patterned on the gate insulating film.

  By forming a different SAM film having the third functional group by the above reaction only on the semiconductor channel region on the first SAM film, an organic semiconductor layer having high positional accuracy, high reproducibility, and high mobility can be obtained. Can be obtained.

  Next, a method and material for forming the organic semiconductor layer will be described.

(Method for forming organic semiconductor layer)
In the present invention, the organic semiconductor layer is formed in the region where the third functional group formed by the above method is formed. As the organic semiconductor material, materials described later can be used.

  As a method for forming the organic semiconductor layer, the above-described dry process such as vacuum deposition method or MBE (Molecular Beam Epitaxy) method, solution such as spin coating method, screen printing method, ink jet printing method, various coating methods, etc. You can list the process. In the organic thin film transistor of the present invention, it is preferable to form the organic semiconductor layer by a solution process among the above processes.

  If it can be formed by a solution process, the number of steps can be greatly reduced, and not only can an organic thin film transistor be formed by a simple process, but also a crystal larger than that formed by a dry process can be formed. As a result, an organic thin film transistor having good mobility can be formed.

  In the present invention, the surface of the insulating film is patterned by a different self-assembled monolayer film even though it is formed by a solution process, so that an organic semiconductor channel can be formed with high precision and good reproducibility.

(Thickness of organic semiconductor layer)
The film thickness of these organic semiconductor layers is not particularly limited, but the characteristics of the obtained transistor are often greatly influenced by the film thickness of the organic semiconductor layer, and the film thickness varies depending on the organic semiconductor, but is generally 1 μm. Hereinafter, 10 to 300 nm is particularly preferable.

  Next, other elements constituting the organic thin film transistor will be described.

〔electrode〕
Next, an electrode material for forming the gate electrode and the source / drain electrode and a forming method thereof will be described.

  In the organic thin film transistor of the present invention, the material constituting the gate electrode, the gate bus line, the wiring portion connecting the electrode and the power source, and the like can be formed of a known electrode material. The electrode material is not particularly limited as long as it is a conductive material. Platinum, gold, silver, nickel, chromium, copper, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium , Molybdenum, tungsten, tin oxide / antimony, indium tin oxide (ITO), fluorine doped zinc oxide, zinc, carbon, graphite, glassy carbon, silver paste and carbon paste, lithium, beryllium, sodium, magnesium, potassium, calcium, Scandium, titanium, manganese, zirconium, gallium, niobium, sodium, sodium-potassium alloy, magnesium, lithium, aluminum, magnesium / copper mixture, magnesium / silver mixture, magnesium / al Bromide mixture, a magnesium / indium mixture, aluminum / aluminum oxide mixture, a lithium / aluminum mixture, or the like is used. Alternatively, known conductive polymers whose conductivity is improved by doping or the like, for example, conductive polyaniline, conductive polypyrrole, conductive polythiophene (polyethylenedioxythiophene and polystyrenesulfonic acid complex, etc.) are also preferably used.

  Among the materials listed above, platinum, gold, silver, nickel, chromium, copper, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum , Ruthenium, germanium, molybdenum, tungsten, tin oxide / antimony, indium tin oxide (ITO), fluorine doped zinc oxide, zinc, carbon, graphite, glassy carbon, silver paste and carbon paste, lithium, beryllium, sodium, magnesium, Potassium, calcium, scandium, titanium, manganese, zirconium, gallium, niobium, sodium, sodium-potassium alloy, magnesium, lithium, aluminum, magnesium / copper mixture, magnesium / silver mixture, Magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide mixture, and lithium / aluminum mixtures. Among them, those having a small electric resistance at the contact surface with the semiconductor layer are preferable, and platinum, gold, silver, and copper are preferable when the semiconductor layer is a p-type semiconductor. Among them, gold is preferable because it has a small potential difference with respect to the organic semiconductor material and has a small carrier injection barrier from the electrode to the organic semiconductor. Further, since gold does not form an oxide film on the electrode surface due to oxidation or the like, there is no fear that the reactivity between the electrode surface and the electrode surface treating agent of the present invention is lowered.

  As a method for forming an electrode, a conductive thin film formed using a dry process such as vapor deposition or sputtering using the above as a raw material, and a method for forming an electrode shape using a known photolithography method or a lift-off method, aluminum, copper, or the like A method in which a resist is formed on a metal foil by thermal transfer, ink jet, etc., patterned by etching, transferred by laser ablation, etc., or a conductive polymer solution or dispersion containing metal fine particles, conductive ink, conductive And a method of forming a functional paste or the like by a printing process such as relief printing, intaglio printing, lithographic printing, screen printing, or a solution process such as an inkjet method.

  As a means for forming the shape of the source electrode and the drain electrode, it is preferable to use a photolithographic method or an inkjet method.

  The surface treatment agent (silane coupling agent) described above preferably cleans the electrode surface cleanly using a known cleaning method immediately before forming the coating layer (SAM film).

  Examples of such an electrode surface cleaning method include treatment with a strong acid / strong alkali, ultraviolet irradiation, ozone treatment, corona discharge treatment, plasma treatment and the like. Of these, plasma treatment is preferred, and atmospheric pressure plasma treatment is more preferred.

  The atmospheric pressure plasma treatment is a treatment in which a gas containing plasma generated by applying an electric field between opposing electrodes under atmospheric pressure is sprayed onto a substrate. In atmospheric pressure plasma processing, the density of active species is higher than in vacuum plasma processing, so the electrode surface can be processed at high speed and high efficiency. There is an advantage that you can. The atmospheric pressure plasma treatment can be performed with reference to JP-A No. 2003-309266.

[Organic semiconductor film]
As an organic semiconductor material constituting the organic semiconductor film, any material can be used as long as it can control the mobility of carriers by the electric field effect. However, a p-type semiconductor in which the carriers are holes and the carriers are electrons. It can be roughly divided into n-type semiconductors. However, up to now, there are few n-type organic semiconductor materials with high mobility and stability, and the majority are p-type organic semiconductor materials.

  Examples of such organic semiconductor materials include various condensed polycyclic aromatic compounds and conjugated compounds.

  Examples of the condensed polycyclic aromatic compound include anthracene, tetracene, pentacene, hexacene, heptacene, chrysene, picene, fluorene, pyrene, peropyrene, perylene, terylene, quaterylene, coronene, ovalene, thacumanthracene, bisanthene, zeslen, heptazelene. , Pyranthrene, violanthene, isoviolanthene, cacobiphenyl, anthradithiophene, and the like, and derivatives and precursors thereof.

  Examples of the conjugated compound include polythiophene and its oligomer, polypyrrole and its oligomer, polyaniline, polyphenylene and its oligomer, polyphenylene vinylene and its oligomer, polythienylene vinylene and its oligomer, polyacetylene, polydiacetylene, tetrathiafulvalene compound, quinone Compounds, cyano compounds such as tetracyanoquinodimethane, fullerenes and derivatives or mixtures thereof.

  In particular, among polythiophene and oligomers thereof, thiophene hexamer, α-seccithiophene α, ω-dihexyl-α-sexualthiophene, α, ω-dihexyl-α-kinkethiophene, α, ω-bis (3- An oligomer such as butoxypropyl) -α-sexithiophene can be preferably used.

  Furthermore, porphyrin, copper phthalocyanine, metal phthalocyanines such as fluorine-substituted copper phthalocyanine described in JP-A No. 11-251601, naphthalene 1,4,5,8-tetracarboxylic acid diimide, N, N′-bis (4-tri Fluoromethylbenzyl) naphthalene 1,4,5,8-tetracarboxylic acid diimide, N, N'-bis (1H, 1H-perfluorooctyl), N, N'-bis (1H, 1H-perfluorobutyl) and N , N'-dioctylnaphthalene 1,4,5,8-tetracarboxylic acid diimide derivative, naphthalene tetracarboxylic acid diimides such as naphthalene 2,3,6,7 tetracarboxylic acid diimide, and anthracene 2,3,6,7 -Condensed rings such as anthracene tetracarboxylic acid diimides such as tetracarboxylic acid diimide Organics such as tracarboxylic acid diimides, tetrathiafulvalene (TTF) -tetracyanoquinodimethane (TCNQ) complex, bisethylenetetrathiafulvalene (BEDTTTTF) -perchloric acid complex, BEDTTTTF-iodine complex, TCNQ-iodine complex, etc. Molecular complexes, fullerenes such as C60, C70, C76, C78, and C84, carbon nanotubes such as SWNT, dyes such as merocyanine dyes and hemicyanine dyes, σ-conjugated polymers such as polysilane and polygerman, and JP-A 2000- An organic / inorganic hybrid material described in 260999 can also be used.

  Among these π-conjugated materials, at least one selected from the group consisting of condensed polycyclic aromatic compounds such as pentacene, fullerenes, condensed ring tetracarboxylic acid diimides, metal phthalocyanines, and metal porphyrins is preferable. Further, pentacenes are more preferable.

  Examples of pentacenes include substituents described in International Publication No. 03/16599, International Publication No. 03/28125, US Pat. No. 6,690,029, Japanese Patent Application Laid-Open No. 2004-107216, and the like. A pentacene derivative described in U.S. Patent Application Publication No. 2003/136964 and the like; Amer. Chem. Soc. , Vol127. Examples include acenes and derivatives thereof described in No. 14.4986 and the like.

  Among these, J. et al. Amer. Chem. Soc. , Vol127. Condensed polycyclic aromatic compounds having an ethynyl substituent as described in No. 14.4986 and the like are preferably used.

  Examples of these include the following organic semiconductor compounds, but the present invention is not limited thereto.

  As a method for forming the organic semiconductor layer, the above-described dry process such as vacuum deposition method or MBE (Molecular Beam Epitaxy) method, solution such as spin coating method, screen printing method, ink jet printing method, various coating methods, etc. You can list the process. In the organic thin film transistor of the present invention, it is preferable to form the organic semiconductor layer by a solution process among the above processes.

  If it can be formed by a solution process, the number of steps can be greatly reduced, and not only can an organic thin film transistor be formed by a simple process, but also a crystal larger than that formed by a dry process can be formed. As a result, an organic thin film transistor having good mobility can be formed.

  In the present invention, the surface of the insulating film is patterned by a different self-assembled monolayer film even though it is formed by a solution process, so that an organic semiconductor channel can be formed with high precision and good reproducibility.

  However, in general, the above condensed polycyclic aromatic compounds and conjugated compounds have poor solubility, and in order to obtain a soluble organic semiconductor material, an organic group such as the above, an alkyl group, an alkylsilyl group, or a cycloalkyl group. It is preferable to use an organic semiconductor material solubilized in a solvent by adding a substituent such as a group or an aryl group.

(Organic solvent used for coating)
The organic solvent used in preparing the organic semiconductor droplet is preferably an aromatic hydrocarbon, an aromatic halogenated hydrocarbon, an aliphatic hydrocarbon or an aliphatic halogenated hydrocarbon, and the aromatic hydrocarbon or aromatic halogen More preferred are hydrocarbons or aliphatic hydrocarbons.

  Examples of the aromatic hydrocarbon organic solvent include toluene, xylene, mesitylene, and methylnaphthalene, but the present invention is not limited thereto.

  Aliphatic hydrocarbons include octane, 4-methylheptane, 2-methylheptane, 3-methylheptane, 2,2-dimethylhexane, 2,3-dimethylhexane, 2,4-dimethylhexane, 2,5-dimethyl. Although hexanecyclohexane, cyclopentane, methylcyclohexane, etc. can be mentioned, this invention is not limited to these.

  Examples of the organic solvent for the aliphatic halogenated hydrocarbon include chloroform, bromoform, dichloromethane, dichloroethane, trichloroethane, difluoroethane, fluorochloroethane, chloropropane, dichloropropane, chloropentane, and chlorohexane. It is not limited to these.

  These organic solvents used in the present invention may be used alone or in combination of two or more. The organic solvent preferably has a boiling point of 50 ° C to 250 ° C.

  Examples of such a soluble organic semiconductor material include poly (3-hexylthiophene) and polythiophene compounds having an alkyl group as described in JP-A Nos. 2003-292588 and 2005-76030, An acene compound and a heteroacene compound having a trialkylsilylethynyl group as described in Patent Document 1, and a three-dimensional cyclic structure such as a bicyclo ring described in JP-A-2003-304104 Examples thereof include porphyrin compounds.

  The film thickness of these organic semiconductor films is not particularly limited, but the characteristics of the obtained transistor are often greatly influenced by the film thickness of the organic semiconductor film, and the film thickness varies depending on the organic semiconductor. In general, the thickness is 10 nm to 1 μm, preferably 20 nm to 500 nm, more preferably 30 nm to 300 nm.

  According to the method of the present invention, since the affinity of the organic semiconductor droplet is high in the region where the third functional group is formed, a semiconductor channel can be formed in this region with high positional accuracy and good reproducibility.

[Gate insulation film]
Various insulating films can be used as the gate insulating layer of the organic thin film transistor of the present invention. For example, silicon oxide, aluminum oxide, tantalum oxide, titanium oxide, tin oxide, vanadium oxide, barium strontium titanate, titanium zirconate Barium oxide, lead zirconate titanate, lead lanthanum titanate, strontium titanate, barium titanate, barium fluoride magnesium, bismuth titanate, strontium bismuth titanate, strontium bismuth tantalate, bismuth tantalate niobate, trioxide yttrium , Etc., metal nitrides such as silicon nitride, aluminum nitride, boron nitride, titanium nitride, polymethyl methacrylate (PMMA), polyvinylphenol (PVP), polyvinyl alcohol (PVA), polyimide, polyamide, polyester, polyacrylate, photo-radical polymerization system, photo-cationic polymerization system photo-curing resin such as epoxy resin or oxetane resin, or copolymer containing acrylonitrile component, polyvinyl phenol, polyvinyl Examples include alcohols, novolak resins, and organic insulating materials such as resins made from natural polysaccharides such as cyanoethyl pullulan and triacetyl cellulose, gelatin, and parylene formed by low-temperature chemical vapor deposition. A combination of these can also be used.

  Among these materials, it is preferable to use a material having a high dielectric breakdown voltage and a high relative dielectric constant. With a material having a high dielectric breakdown voltage, the film thickness of the insulating film can be reduced, the production speed can be increased, and the occurrence of cracks and peeling when the element is bent can be reduced. If a material having a high relative dielectric constant is used, a channel can be formed with a low gate voltage, and an organic thin film transistor that can be driven with a low voltage can be obtained. As the insulating film material satisfying such characteristics, silicon oxide, silicon nitride, polyvinylphenol, and polyimide can be preferably used.

  The insulating film can be formed by vacuum deposition, molecular beam epitaxial growth, ion cluster beam method, low energy ion beam method, ion plating method, chemical vapor deposition (CVD) method, sputtering method, atmospheric pressure plasma CVD. Dry processes such as spray coating, spray coating, spin coating, blade coating, dip coating, casting, roll coating, bar coating, die coating, etc. And a method of forming the surface of the gate electrode by oxidizing or nitriding, and can be used depending on the material.

  The insulating film can also be formed by using a method of oxidizing or nitriding the surface of the gate electrode. Examples of the method for oxidizing the gate electrode include an oxidation method using oxygen plasma and an anodic oxidation method. As a method for nitriding the surface of the gate electrode, a nitriding method using nitrogen plasma can be exemplified.

  Among these, the method for forming an inorganic thin film is preferably an anodic oxidation method, an atmospheric pressure plasma CVD method, or a method combining them.

The anodized film can be formed on the surface of the metal by anodizing a metal that can be anodized by a known method. Examples of the metal that can be anodized include aluminum and tantalum. Any electrolyte solution that can form a porous oxide film can be used as the anodizing treatment. Generally, sulfuric acid, phosphoric acid, oxalic acid, chromic acid, boric acid, sulfamic acid, benzenesulfone, and the like can be used. Acids or the like, or mixed acids obtained by combining two or more of these or salts thereof are used. The treatment conditions for anodization vary depending on the electrolyte used, and thus cannot be specified in general. In general, the electrolyte concentration is 1 to 80% by mass, the electrolyte temperature is 5 to 70 ° C., and the current density. The range of 0.5 to 60 A / dm ² , voltage of 1 to 100 volts, and electrolysis time of 10 seconds to 5 minutes is appropriate. A preferred anodizing treatment is a method in which an aqueous solution of sulfuric acid, phosphoric acid or boric acid is used as the electrolytic solution and the treatment is performed with a direct current, but an alternating current can also be used. The concentration of these acids is preferably 5 to 45% by mass, and the electrolytic treatment is preferably performed for ²⁰ to 250 seconds at an electrolyte temperature of 20 to 50 ° C. and a current density of 0.5 to 20 A / dm ² .

  The atmospheric pressure plasma CVD method is a fine particle generated by introducing a raw material compound that forms a thin film into a plasma generated by applying an electric field between opposing electrodes under atmospheric pressure, and causing a chemical reaction in the plasma. Is deposited on a substrate to form a thin film using a known technique described in JP-A-11-43781, JP-A-2003-179234, WO2004-75279, or the like. Can be created.

  As the method for forming an insulating film made of an organic compound, the wet process is preferable.

  An inorganic oxide film and an organic oxide film can be laminated and used together. The thickness of these insulating films is generally 50 nm to 3 μm, preferably 100 nm to 1 μm.

  In addition, a second coating layer may be formed on the surface of the gate insulating layer for the purpose of modifying various characteristics such as flatness and surface energy. The second coating layer may be a thin film made of an inorganic oxide such as titanium oxide, aluminum oxide or tantalum oxide, or a high dielectric constant polymer such as polyvinylidene fluoride.

  Since the coating layer formed from the silane coupling agent having a functional group having reactivity with the film surface can form a monomolecular film, the film thickness can be kept constant, and the organic thin film transistor element with little variation Can be obtained.

[Substrate]
Various materials can be used as a base (also referred to as a substrate) for forming an organic thin film transistor. For example, glass, quartz, aluminum oxide, sapphire, silicon nitride, silicon carbide and other ceramic bases, silicon, germanium, gallium A semiconductor substrate such as arsenic, gallium phosphide, and gallium nitrogen, paper, non-woven fabric, and the like, and a substrate made of a metal such as stainless steel and aluminum having a thickness that can be bent can be used. Preferably, for example, a plastic film sheet can be used. 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 a plastic film, it is possible to reduce the weight as compared to the case of using a glass substrate, to improve portability, and to improve resistance to impact. Further, it becomes possible to incorporate or integrate a field effect transistor into a display device or electronic device having a curved shape.

[Undercoat layer]
In the organic thin film transistor of the present invention, when the substrate is a plastic film, an undercoat layer containing a compound selected from an inorganic oxide and an inorganic nitride, and a polymer in order to improve the adhesion between the substrate and the organic thin film transistor It is preferable to have at least one of the undercoat layers containing.

  Examples of the inorganic oxide contained in the undercoat layer include silicon oxide, aluminum oxide, tantalum oxide, titanium oxide, tin oxide, vanadium oxide, barium strontium titanate, barium zirconate titanate, lead zirconate titanate, titanate Examples include lead lanthanum, strontium titanate, barium titanate, barium magnesium fluoride, bismuth titanate, strontium bismuth titanate, strontium bismuth tantalate, bismuth tantalate niobate, and yttrium trioxide. Examples of the inorganic nitride include silicon nitride and aluminum nitride.

  Of these, silicon oxide, aluminum oxide, tantalum oxide, titanium oxide, and silicon nitride are preferable.

  In the present invention, as a method for forming an undercoat layer containing a compound selected from inorganic oxides and inorganic nitrides, the same method for forming an inorganic oxide or inorganic nitride as the above-described gate insulating film forming method is used. However, it is preferably formed by an atmospheric pressure plasma method.

  Polymers used for the undercoat layer containing polymer include polyester resin, polycarbonate resin, cellulose resin, gelatin, acrylic resin, polyurethane resin, polyethylene resin, polypropylene resin, polystyrene resin, phenoxy resin, norbornene resin, epoxy resin, vinyl chloride Vinyl acetate copolymer, vinyl chloride resin, vinyl acetate resin, copolymer of vinyl acetate and vinyl alcohol, partially hydrolyzed vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile Copolymers, ethylene-vinyl alcohol copolymers, polyvinyl alcohol, chlorinated polyvinyl chloride, ethylene-vinyl chloride copolymers, vinyl polymers such as ethylene-vinyl acetate copolymers, polyamide resins, ethylene-butadiene Down resin, a butadiene - rubber resin such as acrylonitrile resin, silicone resin, and fluorine resins.

[Protective layer]
It is also possible to provide a protective layer on the organic thin film transistor of the present invention. Examples of the protective layer include inorganic oxides or inorganic nitrides, metal thin films such as aluminum, polymer films with low gas permeability, and laminates thereof. By having such a protective layer, durability of organic thin film transistors can be mentioned. Improves. As a method for forming these protective layers, the same method as the method for forming the gate insulating film described above can be used. Further, the protective layer may be provided by a method such as simply laminating a film in which various inorganic oxides are laminated on the polymer film.

[Configuration of organic thin film transistor]
An example of the layer structure of the organic thin film transistor of the present invention will be described with reference to the drawings.

  The organic thin film transistor has a source electrode and a drain electrode connected by an organic semiconductor layer on a base, a top gate type having a gate electrode through a gate insulating layer thereon, and a gate electrode on the base first. And a bottom gate type having a source electrode and a drain electrode connected by an organic semiconductor film through a gate insulating layer. Further, the source / drain electrodes as viewed from the gate electrode can be distinguished into a bottom contact type in front of the organic semiconductor layer and a top contact type in the other side of the organic semiconductor layer. Various types of organic thin film transistors can be configured. In the organic thin film transistor of the present invention, since it is necessary to form an organic semiconductor layer after forming a self-assembled monolayer on an insulating film, either a bottom gate / bottom contact type configuration or a bottom gate / top contact type configuration is required. It is preferable that In addition, when a large number of layers are formed on the organic semiconductor layer, the organic semiconductor layer may be deteriorated by heat, light, or the like at the time of forming these layers. Therefore, the most preferable element configuration is shown in FIG. Such a bottom gate / bottom contact type device.

  In FIG. 1, a first electrode pattern 2 is formed on a substrate 1, and an insulating layer 3 is formed so as to cover the entire first electrode pattern 2 (FIG. 1 (1)). On the insulating layer 3, a source electrode 4 and a drain electrode 5 are formed by patterning such as vapor deposition (FIG. 1 (2)). A first self-assembled monolayer 6 is formed thereon (FIG. 1 (3)), and a self-assembled monolayer 7 having a second functional group is formed thereon by photopatterning (FIG. 1). 1 (4)), and further reacting with a compound that reacts with the second functional group (compound represented by the general formula (1)) to introduce the third functional group (FIG. 1 (5), Self-assembled monolayer 7 ′) having 3 functional groups. Next, an organic semiconductor material 8 is formed on the SAM film having the third functional group by dropping an organic semiconductor material between the source and drain electrodes by a solution process (FIGS. 1 (6) and (7)).

  The configuration of FIG. 2 is an example of a bottom contact type configuration in which the source electrode 4 and the drain electrode 5 are formed after the organic semiconductor layer 8 is formed on the gate insulating film 3 by the process of the present invention.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
<< Production of organic thin film transistor >>
On an n-type Si wafer having a silicon oxide film having a thickness of 200 nm formed by thermal oxidation and having a specific resistance of 0.02 Ω · cm, the following electroless plating catalyst solution is used as an ink using an electrostatic suction ink jet apparatus. In use, a bias voltage of 2000 V was applied to the support base, and a pulse voltage (400 V) was superimposed thereon, and ink was ejected according to the source and drain electrode patterns. The inner diameter of the nozzle outlet was 10 μm, and the gap between the nozzle outlet and the substrate was kept at 500 μm. The following prescription was used as the plating catalyst-containing ink.

(Electroless plating catalyst solution)
Soluble palladium salt (palladium chloride, Pd ²⁺ concentration 1.0 g / L) 20% by mass
Isopropyl alcohol 12% by mass
Glycerin 20% by mass
2-Methyl-pentanethiol 5% by mass
1,3-butanediol 3% by mass
Ion exchange water 40% by mass
Furthermore, a catalyst pattern was formed by drying and fixing.

  Next, printing was performed on the region including the region where the plating catalyst pattern was formed by using the following electroless gold plating solution as an ink by a screen printing method. When the plating agent was in contact with the plating catalyst, the gold thin film was deposited only on the plating catalyst pattern.

(Electroless gold plating solution)
Dicyano gold potassium 0.1 mol / L
Sodium oxalate 0.1 mol / L
Sodium potassium tartrate 0.1mol / L
The substrate surface on which the gold thin film was dissolved was thoroughly washed with pure water and dried to form a source / drain electrode pattern made of gold. The source / drain electrodes were formed such that the channel length L was 25 μm and the channel width W was 250 μm, and there were 10 such source / drain electrodes.

  Next, the Si wafer on which the source / drain electrodes are formed is subjected to a vacuum oxygen plasma treatment for 60 seconds under conditions of an oxygen flow rate of 50 sccm, a vacuum degree of 10 Pa, and an output of 200 W using an Anelva dry etching apparatus DEM-451. Then, the substrate surface on which the source / drain electrodes were formed was cleaned.

<Production of Comparative Organic Thin Film Transistor Array 1>
On the substrate subjected to the above cleaning, hexamethyldisilazane (HMDS) is spin-coated at 3000 rpm for 1 minute, dried at 90 ° C. for 2 minutes, then ultrasonically cleaned with toluene, then with isopropanol, and dried. A self-assembled monolayer made of HMDS was formed on the surface of the insulating film.

  Next, the following organic semiconductor material (1) as a p-type organic semiconductor material is dissolved in toluene at a concentration of 0.5% by mass, and this solution is approximately circular with a diameter of about 300 μm using a microinjector IM300 manufactured by Narishige. The organic semiconductor layer is formed by applying heat treatment at 90 ° C. for 1 minute in a nitrogen gas atmosphere after coating between the source electrode and the drain electrode so as to be, and drying at room temperature. Was made.

  Note that the organic semiconductor material 1 is the same as that described in J.I. Am. Chem. Soc. , Vol. 127 (2005) p4986 was synthesized with reference.

<Production of Comparative Organic Thin Film Transistor Array 2>
After being immersed in a 10 mmol / L toluene solution of the following surface treatment agent 1 (synthesized by the method described in Polymer Preprints, Japan, vol 55 (2006) p3953) at 60 ° C. for 10 minutes on the cleaned substrate. Then, it was ultrasonically washed with toluene and then with isopropanol and dried to form a self-assembled monomolecular film composed of the surface treating agent 1 on the surface of the insulating film.

  Next, the organic semiconductor material 1 as a p-type organic semiconductor material is dissolved in toluene at a concentration of 0.5 mass%, and this solution is formed into a substantially circular shape having a diameter of about 300 μm using a microinjector IM300 manufactured by Narishige. The organic semiconductor layer is formed by applying a heat treatment at 90 ° C. for 1 minute in a nitrogen gas atmosphere after coating between the source electrode and the drain electrode and drying at room temperature. did.

<Production of Comparative Organic Thin Film Transistor Array 3>
In the production of the organic thin film transistor array 2, after forming a self-assembled monolayer composed of the surface treating agent 1 on the surface of the insulating film, a high pressure mercury lamp is passed through the mask at an energy of 500 mJ / cm ² only between the source and drain electrodes. Were subjected to photolysis. It was ultrasonically washed with toluene and then with isopropanol and dried.

  Next, the following organic semiconductor material 1 as a p-type organic semiconductor material is dissolved in toluene at a concentration of 0.5% by mass, and this solution is formed into a substantially circular shape having a diameter of about 300 μm using a microinjector IM300 manufactured by Narishige. The organic semiconductor layer is formed by applying a heat treatment at 90 ° C. for 1 minute in a nitrogen gas atmosphere after applying between the source electrode and the drain electrode and drying at room temperature. did.

<Production of Organic Thin Film Transistor Array 4 of the Present Invention>
In the production of the organic thin film transistor array 3, only the source / drain electrodes of the self-assembled monomolecular film made of the surface treatment agent 1 on the surface of the insulating film are exposed through a mask, photolyzed, ultrasonic cleaning, After drying, t-butylamine was spin-coated at 3000 rpm for 1 minute, dried at 90 ° C. for 2 minutes, and then ultrasonically washed with toluene and then with isopropanol, followed by drying. By this operation, the photodecomposed surface treatment agent and t-butylamine were reacted, and converted into a self-assembled monolayer having a t-butyl group at the terminal only between the source and drain electrodes.

  Next, the organic semiconductor material 1 as a p-type organic semiconductor material is dissolved in toluene at a concentration of 0.5 mass%, and this solution is formed into a substantially circular shape having a diameter of about 300 μm using a microinjector IM300 manufactured by Narishige. The organic semiconductor layer is formed by applying heat treatment at 90 ° C. for 1 minute in a nitrogen gas atmosphere after coating between the source electrode and the drain electrode and drying at room temperature. did.

<Preparation of Organic Thin Film Transistor Array 5 of the Present Invention>
In the production of the organic thin film transistor array 3, only the source and drain electrodes of the self-assembled monolayer film made of the surface treatment agent 1 on the surface of the insulating film are exposed through a mask, subjected to photolysis, ultrasonic cleaning, and drying. Then, aminopropyltrimethylsilane (APTMS) was spin-coated at 3000 rpm for 1 minute, dried at 90 ° C. for 2 minutes, and then ultrasonically washed with toluene and then with isopropanol and dried. By this operation, the photodecomposed surface treatment agent and APTMS were reacted to convert into a self-assembled monomolecular film having a trimethylsilyl group at the terminal only between the source and drain electrodes.

  Next, the following organic semiconductor material 1 as a p-type organic semiconductor material is dissolved in toluene at a concentration of 0.5% by mass, and this solution is formed into a substantially circular shape having a diameter of about 300 μm using a microinjector IM300 manufactured by Narishige. The organic semiconductor layer is formed by applying a heat treatment at 90 ° C. for 1 minute in a nitrogen gas atmosphere after applying between the source electrode and the drain electrode and drying at room temperature. did.

<Production of Organic Thin Film Transistor Array 6 of the Present Invention>
In the production of the organic thin film transistor array 3, only the source and drain electrodes of the self-assembled monolayer film made of the surface treatment agent 1 on the surface of the insulating film are exposed through a mask, subjected to photolysis, ultrasonic cleaning, and drying. Then, aminopropyltriisopropylsilane (APTIPS) was spin-coated at 3000 rpm for 1 minute, dried at 90 ° C. for 2 minutes, and then ultrasonically washed with toluene and then with isopropanol and dried. By this operation, the photodecomposed surface treatment agent and APTIPS were reacted, and converted into a self-assembled monolayer having a triisopropylsilyl group at the terminal only between the source and drain electrodes.

  Next, the organic semiconductor material (1) as a p-type organic semiconductor material is dissolved in toluene at a concentration of 0.5% by mass, and this solution is formed into a substantially circular shape having a diameter of about 300 μm using a microinjector IM300 manufactured by Narishige. After being applied between the source electrode and the drain electrode and dried at room temperature, an organic semiconductor layer is formed by performing a heat treatment at 90 ° C. for 1 minute in a nitrogen gas atmosphere. Produced.

  In addition, APTIPS is J. Org. Chem. , Vol. 60 (1995) p1912 was synthesized by reacting aryltriisopropylsilane with o-mesitylsulfonylhydroxylamine.

<Production of Organic Thin Film Transistor Array 7 of the Present Invention>
The organic thin film transistor array 6 was produced in the same manner as the organic thin film transistor array 6 except that the organic semiconductor material (1) was changed to the organic semiconductor material (2).

  Note that the organic semiconductor material 1 is the same as that described in J.I. Am. Chem. Soc. , Vol. 123 (2001) p9482 was synthesized as a reference.

  The following evaluation was performed with respect to the obtained organic thin-film transistor arrays 1-7.

(Applicability of organic semiconductor solution)
When the organic semiconductor solution was dropped on 10 source / drain electrodes of each organic thin film transistor array, the coating property of the organic semiconductor solution was evaluated according to the following criteria.

○ 10 elements that could be applied to cover all the source and drain electrodes △ 7 to 9 elements that could be applied to cover all the areas between the source and drain electrodes × Applied to cover all the areas between the source and drain electrodes Less than 6 elements (carrier mobility before durability test)
For the organic thin film transistor, the carrier mobility was calculated from the saturation region of the IV characteristics when the drain bias was −50 V and the gate bias was swept from −50 V to 0 V, and the average value for 10 elements was calculated. .

  The evaluation results of the organic semiconductor arrays 1 to 7 are shown below.

  As can be seen from the table, in the comparative organic thin film transistor array 1 or 2, the coating property of the organic semiconductor solution is inferior, and the organic semiconductor layer cannot be formed at a desired site. As a result, the average mobility is low. Moreover, in the comparative organic thin-film transistor array 3, although the applicability | paintability is good, the carbonyl group generate | occur | produced by photolysis becomes a trap, and high mobility cannot be obtained. On the other hand, in the organic thin-film transistor of the present invention, the coating property of the organic semiconductor solution was good, and the average mobility was able to obtain a practically high value.

It is sectional drawing which shows an example of a bottom gate type element. It is sectional drawing which shows another example of a bottom gate type element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Gate electrode 3 Gate insulating film 4 Source electrode 5 Drain electrode 6 First self-assembled monolayer 7 Self-assembled monolayer having a third functional group 8 Organic semiconductor layer

Claims (9)

An organic thin film transistor having a gate electrode, a gate insulating film, a semiconductor layer made of an organic semiconductor material, a source electrode, and a drain electrode,
Forming a first self-assembled monolayer made of a compound having a first functional group decomposable by light or acid on the gate insulating film;
Pattern exposure of actinic rays on the self-assembled monolayer, decomposing the self-assembled monolayer, and exposing a second functional group on the self-assembled monolayer at the exposed site;
A step of reacting the second functional group with a compound represented by the following general formula (1) to form a third functional group on the self-assembled monolayer;
An organic thin film transistor comprising a self-assembled monomolecular film having a patterned third functional group, formed by the above, on a gate insulating film.

(In the formula, Q represents a tetravalent atom selected from C, Si, Ge, Sn, and Pb, A represents a group that can be bonded to the second functional group, L ₁ represents a single bond, an alkylene group, cyclo A divalent linking group selected from an alkylene group, an alkene-1,2-diyl group, an alkyne-1,2-diyl group, and an arylene group, or an ether group, a thio group, a carbonyl group, or a carbonyloxy group. Represents a divalent linking group selected from a divalent linking group linked to Z. R _{1 to} R ₃ are an alkyl group, a halogenated alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, and an aryl group. Represents a substituent selected from a heteroaryl group and an alkylsilyl group, which may be linked to each other to form a ring. 2. The organic thin film transistor according to claim 1, wherein a semiconductor layer made of the organic semiconductor material is formed on a self-assembled monomolecular film having the third functional group. The surface energy E3 of the self-assembled monolayer having the third functional group is larger than the surface energy E1 of the self-assembled monolayer having the first functional group. The organic thin film transistor as described in 1. The organic thin film transistor according to any one of claims 1 to 3, wherein the atom represented by Q in the general formula (1) is a silicon atom. The organic thin film transistor according to any one of claims 1 to 4, wherein the functional group capable of binding to the second functional group represented by A is an amino group. The first self-assembled monolayer that is decomposed by the actinic ray is a self-assembled monolayer formed by a silane coupling agent represented by the following general formula (2): The organic thin-film transistor of any one of Claims 1-5.

(In the formula, Z represents a chalcogen atom selected from oxygen, sulfur, selenium and tellurium, and L ₂ represents a single bond, an alkylene group, a cycloalkylene group, an alkene-1,2-diyl group, an alkyne-1,2-diyl. A divalent linking group selected from a group, an arylene group, or a divalent linking group selected from these groups, and a divalent linking group linked to Z via an ether group, a thio group, a carbonyl group, or a carbonyloxy group. R ₄ and R ₅ are selected from a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group, a halogenated aryl group, a heteroaryl group, and an alkylsilyl group. X represents a hydrolyzable substituent selected from a halogen atom, an alkoxy group, and an isocyanate group, and m and n represent an integer of 1 to 3). The organic thin film transistor according to claim 6, wherein the substituent represented by R ₅ in the general formula (2) is a halogenated alkyl group. The organic thin film transistor according to claim 1, wherein the semiconductor layer is formed by coating. The organic thin film transistor according to claim 1, wherein the semiconductor layer is a pentacene derivative.

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