JP5463538B2 - Method for producing organic thin film transistor - Google Patents

Description

  The present invention relates to a method for manufacturing an organic thin film transistor that uses a thin film layer of an organic semiconductor as an operation layer.

  A thin film transistor (TFT) is widely used as a switching element for controlling the display operation of each pixel and a driving element for driving each pixel in a flat panel display device such as a liquid crystal display. As a substrate material used for manufacturing a thin film transistor, use of a substrate made of various light-transmitting insulating polymer materials, for example, a plastic substrate has been promoted.

  The heat resistance of a substrate made of an insulating polymer material, such as a plastic substrate, is significantly inferior to that of a substrate made of an inorganic material, such as a glass substrate. Therefore, the application of organic thin-film transistors that use organic semiconductor thin-film layers that can be manufactured under low-temperature conditions is being promoted as semiconductor thin-film layers that are used for the operating layers of thin-film transistors.

  An effective channel layer in an organic thin film transistor is formed at the junction interface between the gate insulating film and the organic semiconductor thin film layer. In order to improve carrier mobility in this effective channel layer, a method of forming a “self-assembled monolayer” of an organic compound constituting an organic semiconductor in advance on the surface of the gate insulating film is used. (Patent Document 1). When a layer made of an organic compound is stacked on this “self-assembled monolayer”, the stacked organic compound maintains an ordered orientation according to the order of the molecules in the self-assembled monolayer. (Epitaxial growth-like layered state).

  On the other hand, in a region where the “self-assembled monolayer” does not exist in the lower layer, when a layer made of an organic compound is laminated in that region, the ordered orientation is not substantially provided. For example, the organic compound molecules are locally deposited in a “disordered arrangement”, although there are portions where the orientations are uniform to some extent locally.

There has been proposed a method in which a source electrode and a drain electrode constituting an organic thin film transistor are formed in a self-aligned shape with respect to a gate electrode. Specifically, after applying a dispersion of metal nanoparticles to form a source electrode and a drain electrode, this coating film layer is subjected to a low-temperature baking treatment, and this coating layer is used when a sintered body layer of metal nanoparticles is used. The end of the film layer is in a state of self-alignment with the side end position of the gate electrode. For example, in accordance with the shape of the gate electrode, a portion corresponding to the channel region on the surface of the gate insulating film covering the gate electrode is covered with a resist. Further, the gate insulating film surface is covered with the resist so as to surround the openings for the source electrode formation portion and the drain electrode formation portion. When the dispersion of metal nanoparticles uses an aqueous solvent as the dispersion solvent, the resist surface is liquid repellent, but the gate insulating film surface exposed to the opening is lyophilic. Bleeding of the metal nanoparticle dispersion is prevented. Therefore, at the side end position of the gate electrode, the dispersion of the metal nanoparticles applied to the opening is a “self-aligned” coating film layer so as to be in contact with the side end of the resist. Subsequently, the dispersion solvent contained in the coating film layer is evaporated and pre-baked, and then the resist is peeled off and the coating film layer is subjected to main baking. As a result, the manufactured source electrode and drain electrode are formed in a self-aligned shape with respect to the gate electrode (Patent Document 2). After removing the resist, a thin film layer of the organic semiconductor is formed, and the organic semiconductor is coated so as to cover a part corresponding to the channel region on the surface of the gate insulating film covering the gate electrode and a part of the source electrode and the drain electrode. The thin film layer is patterned.
US Pat. No. 6,433,359 JP 2006-286719 A

  The process of producing the source electrode and the drain electrode constituting the organic thin film transistor by using a dispersion of metal nanoparticles can be performed under a low temperature condition, and is made of various light-transmitting insulating polymer materials. Suitable for the use of substrates, for example plastic substrates.

  However, a pretreatment process is required to cover the surface of the gate insulating film with a resist so as to surround the openings for the source electrode formation portion and the drain electrode formation portion. In addition, since the resist surface is liquid repellent, the gate insulating film surface exposed to the opening utilizes a characteristic that it is lyophilic. Therefore, a dispersion of metal nanoparticles using an aqueous solvent as a dispersion solvent is used. Need to use. In addition, when the resist is peeled off, it is necessary to evaporate the dispersion solvent contained in the coating film layer and perform a pre-baking treatment to avoid peeling of the coating film layer. In other words, it is necessary to blend a binder resin component in the metal nanoparticle dispersion to avoid peeling of the coating film layer.

  Therefore, the above resist surface is lyophobic, but the gate insulating film surface exposed to the opening is lyophilic. In the case of using a dispersion of metal nanoparticles, it is not applicable. Further, when the binder resin component is not blended in the dispersion of the metal nanoparticles, when the resist is peeled, the dispersion solvent contained in the coating film layer is evaporated and pre-baked to remove the coating film layer. There is no way to avoid it.

  When using a dispersion of metal nanoparticles using an organic solvent instead of an aqueous solvent, especially when no binder resin component is blended in the dispersion of metal nanoparticles, an organic thin film transistor is formed. In order to produce a source electrode and a drain electrode using a dispersion of metal nanoparticles, it is necessary to develop a new method.

  The present invention solves the aforementioned problems. That is, an object of the present invention is to produce a source electrode and a drain electrode constituting an organic thin film transistor by using a dispersion of metal nanoparticles using an organic solvent as a dispersion solvent. Provided is a method for manufacturing an organic thin film transistor, which uses a technique of applying a dispersion of metal nanoparticles by applying an ink jet printing method without using a resist provided with openings corresponding to the portions and drain electrode forming portions. There is.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies.

First, it was noted that the target organic thin film transistor is a switching element that controls the display operation of each pixel and a driving element that drives each pixel in a flat panel display device such as a liquid crystal display. That is, it was noted that the element size of the driving TFT is determined based on the size of one pixel. Assuming that the size of one pixel is a rectangle of 400 μm × 400 μm, the manufacturing portion of the driving TFT element is, for example, 300 μm × 300 μm or less. In that case, the organic thin film transistor of the gate electrode a gate width: W _G is 300 [mu] m or less, for example, is selected in a range of 100 m to 300 m, the gate length: L _G is selected in the range of 5 m to 30 m. Corresponding to the size of the gate electrode, the sizes of the source electrode and the drain electrode are determined. Therefore, when the source electrode is a rectangle having a length: L _S and a width: W _S and the drain electrode is a rectangle having a length: L _D and a width: W _D , the length: L _S and the length: L _D Is selected in the range of 100 μm or less, for example, in the range of 30 μm to 100 μm, the width: W _S and the width: W _D in the range of 250 μm or less, for example, in the range of 80 μm to 250 μm.

At that time, for example, the size of the channel region between the source electrode and the drain electrode, i.e., the length of the channel region: L _channel, the gate length: based on the L _G, in the range of 2L _G ≧ L _channel ≧ L _G select. That is, between the source electrode and the drain electrode gap: L _SD, the gate length: based on the L _G, selected within the range of _{2L G ≧ L SD ≧ L G} . For example, when observed from directly above the channel region, horizontal gaps between the side edges of the gate electrode and the source and drain electrodes: ΔL _SG , ΔL _DG are 1/2 · L _G ≧ ΔL _SG , ΔL Select within the range of _DG ≧ 0.

In consideration of the target size of the source electrode and the drain electrode and the alignment accuracy target for the gate electrode, the accuracy of drawing the pattern of the metal nanoparticle dispersion coating layer used for the production is the minimum line width / minimum space width, at least, it was concluded that it is preferably in the range of less than 1/2 · L _G. As a means for achieving the accuracy of drawing the pattern of the coating layer of the metal nanoparticle dispersion, the metal nanoparticle dispersion is applied to the metal nanoparticle dispersion in a predetermined pattern using an ultrafine inkjet printing apparatus. It has been found that a technique for forming a coating layer can be used.

On the other hand, in the organic thin film transistor, in the “ON state”, an “effective channel layer” is formed at the interface between the gate insulating film and the organic semiconductor layer immediately above the gate electrode in the channel region. At this time, if the carrier mobility in the organic semiconductor layer in the vicinity of the interface with the gate insulating film, which functions as an “effective channel layer”, is improved, the drain current I _{d-ON in the} “ON state” increases. As a means for this, for example, a “self-assembled monomolecular film” of an organic compound constituting an organic semiconductor is formed on the surface of a gate insulating film, and the “self-assembled monomolecular film” is used as a base layer to form a vacuum deposition method. It was found that a method for forming an organic semiconductor film can be used. It is also confirmed that the drain current I _{d-OFF in the} “OFF state” is reduced by adopting an organic semiconductor film that is formed by vacuum deposition using the “self-assembled monolayer” as the underlayer. Is done. Therefore, it is confirmed that the ON / OFF current ratio: I _d-ON / I _d-OFF is remarkably improved.

  Based on the above findings, the present inventors have completed the present invention.

The manufacturing method of the organic thin film transistor according to the first aspect of the present invention is as follows.
A method of manufacturing an organic thin film transistor, comprising:
Forming a gate electrode on the substrate;
Forming a gate insulating film covering the surface of the gate electrode on the substrate;
Forming a source electrode and a drain electrode on the gate insulating film;
Forming an organic semiconductor film on the gate insulating film so as to cover the source electrode and drain electrode surfaces;
In the step of forming the organic semiconductor film,
Using the vacuum deposition method, the organic semiconductor film is formed,
In the step of forming the source electrode and the drain electrode,
Using an ultrafine inkjet printing apparatus, the metal nanoparticle dispersion is applied in a predetermined pattern shape to form a metal nanoparticle dispersion coating layer,
A method for producing an organic thin film transistor, wherein the metal nanoparticle dispersion coating layer is heated and fired to form a source electrode and a drain electrode composed of a sintered body layer of metal nanoparticles.

The method for producing an organic thin film transistor according to the second embodiment of the present invention is as follows.
A method of manufacturing an organic thin film transistor, comprising:
Forming a gate electrode on the substrate;
Forming a gate insulating film covering the surface of the gate electrode on the substrate;
Forming an organic semiconductor film on the gate insulating film;
Forming a source electrode and a drain electrode on the organic semiconductor film;
In the step of forming the organic semiconductor film,
Using the vacuum deposition method, the organic semiconductor film is formed,
In the step of forming the source electrode and the drain electrode,
Using an ultrafine inkjet printing apparatus, the metal nanoparticle dispersion is applied in a predetermined pattern shape to form a metal nanoparticle dispersion coating layer,
A method for producing an organic thin film transistor, wherein the metal nanoparticle dispersion coating layer is heated and fired to form a source electrode and a drain electrode composed of a sintered body layer of metal nanoparticles.

In the method for producing an organic thin film transistor according to the present invention,
The minimum line width of the metal nanoparticle dispersion liquid coating layer formed using the ultrafine inkjet printing apparatus is selected in the range of 1 μm to 10 μm,
The coating thickness of the metal nanoparticle dispersion coating layer can be selected in the range of 30 nm to 600 nm.

In addition, in the application of the metal nanoparticle dispersion using the ultrafine inkjet printing apparatus,
The amount of droplets to be discharged can be selected in the range of 0.3 femtoliter to 1 femtoliter.

  On the other hand, it is preferable to select the average particle diameter of the metal nanoparticles dispersed in the metal nanoparticle dispersion in the range of 1 to 100 nm.

The metal nanoparticles dispersed in the metal nanoparticle dispersion are:
Nanoparticles composed of one kind of metal or nanometers composed of two or more kinds of metals selected from the group of metals consisting of gold, silver, copper, platinum, palladium, nickel, tantalum, bismuth, indium, tin, titanium, and aluminum Nanoparticles made of a mixture of particles or an alloy of two or more metals selected from the group of metals are preferred.

  In addition, it is preferable to select a liquid viscosity at 20 ° C. of the metal nanoparticle dispersion liquid discharged using the ultrafine inkjet printing apparatus in a range of 2 mPa · s to 30 mPa · s.

In particular, in the method for producing an organic thin film transistor according to the present invention,
The metal nanoparticle dispersion, which is discharged using the ultrafine inkjet printing apparatus,
As a solid component, a dispersion obtained by uniformly dispersing the metal nanoparticles in a dispersion solvent,
The surface of the metal nanoparticle contains a nitrogen, oxygen, or sulfur atom as a group capable of coordinative bonding with the metal element contained in the metal nanoparticle, and is coordinated by a lone electron pair possessed by these atoms. Covered with one or more organic compounds having a group capable of bonding;
It is desirable that 10 to 50 parts by mass of the total of one or more organic compounds having a group containing nitrogen, oxygen or sulfur atoms is contained with respect to 100 parts by mass of the metal nanoparticles.

At that time, the metal nanoparticle dispersion liquid discharged using the ultrafine inkjet printing apparatus,
As a dispersion solvent, containing one or more liquid organic substances or organic solvents,
It is preferable to select an organic solvent having a melting point of 20 ° C. or lower and a boiling point of 80 to 300 ° C. for at least one of the liquid organic substance or organic solvent.

The dispersion solvent is
High solubility capable of dissolving 50 parts by mass or more of the organic compound having a group containing nitrogen, oxygen, or sulfur atoms covering the surface of the metal nanoparticles per 100 parts by mass of the dispersion solvent when heated to 100 ° C. or higher. It is preferable that the organic solvent or the organic solvent having liquidity is a solvent consisting of one kind of liquid organic substance or a mixed solvent consisting of two or more kinds.

  For example, as the dispersion solvent, an alkane having 10 to 18 carbon atoms or a primary alcohol having 8 to 12 carbon atoms can be selected.

Furthermore, the metal nanoparticle dispersion liquid discharged using the ultrafine inkjet printing apparatus is:
A concentrated dispersion obtained by partially evaporating and removing the dispersion solvent contained in the dispersion and concentrating until the volume ratio of the dispersion solvent is in the range of 20 to 50% by volume has a liquid viscosity at 20 ° C. Is preferably a viscous concentrate in the range of 20 Pa · s to 1000 Pa · s.

Meanwhile, when the metal nanoparticle dispersion coating layer is heated and fired,
The firing temperature is selected in the range of 100 ° C to 230 ° C.

In the method for producing an organic thin film transistor according to the present invention,
The organic semiconductor layer is
A layer made of pentacene or hexadecafluorocopper phthalocyanine is preferable.

  By using the method for producing an organic thin film transistor according to the present invention, the source electrode and the drain electrode constituting the organic thin film transistor can be produced using a dispersion of metal nanoparticles using an organic solvent as a dispersion solvent. . In particular, the source electrode and drain electrode manufacturing process does not require a resist provided with openings corresponding to the source electrode formation portion and the drain electrode formation portion, and is applied with an ink jet printing method. It is possible to apply the metal nanoparticle dispersion liquid to the target source electrode formation portion and drain electrode formation portion by using the method of applying the above.

  Below, the manufacturing method of the organic thin-film transistor concerning this invention is demonstrated in detail.

  First, the manufacturing method of the organic thin-film transistor concerning the 1st form of this invention is applied to manufacture of the organic thin-film transistor of the 1st form which has the following structure.

  Moreover, the manufacturing method of the organic thin-film transistor concerning the 2nd form of this invention is applied to manufacture of the organic thin-film transistor of the 2nd form which has the following structure.

The organic thin film transistor of the first form is
A substrate,
A gate electrode formed on the substrate;
A gate insulating film formed on the substrate so as to cover the surface of the gate electrode;
A source electrode and a drain electrode formed on the gate insulating film;
An organic semiconductor film is formed on the gate insulating film so as to cover the surfaces of the source electrode and the drain electrode.

The organic thin film transistor of the second form is
A substrate,
A gate electrode formed on the substrate;
A gate insulating film formed on the substrate so as to cover the surface of the gate electrode;
An organic semiconductor film formed on the gate insulating film;
A source electrode and a drain electrode are formed on the organic semiconductor film.

  When manufacturing this organic thin film transistor, the substrate is a substrate formed of an insulating material. When applied to a flat panel display device such as a liquid crystal display, a substrate formed of a light transmissive insulating material is used. A light-transmitting substrate formed of an inorganic insulating material, for example, a glass substrate can be used. In addition, a substrate formed of a light-transmitting insulating organic resin material, for example, a substrate formed of a light-transmitting plastic material such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or polyimide may be used. it can.

Method for producing an organic thin film transistor of the present invention is directed, in the above organic thin film transistor, for example, the size of the gate electrode, the gate length: L _G is in the range of 5 m to 30 m, preferably, selected within the range of 7μm~20μm The gate width: W _G is selected in the range of 100 μm to 300 μm.

The channel length: L _channel, the gate length: based on the L _G, the range of _{2L G ≧ L channel ≧ L G} , preferably, selected within the range of _{4/3 · L G ≧ L} channel ≧ L G. That is, is formed so as to sandwich the gate electrode, the spacing between the side edge of the gate electrode of the source electrode and the drain electrode: L _SD, the gate length: based on the L _G, the 2L _G ≧ L _SD ≧ L _G range, preferably, selected within the range of _{4/3 · L G ≧ L} SD ≧ L G.

The gate electrode is located under the gate insulating film, and the source electrode and the drain electrode are located on the gate insulating film, but when observed from directly above,
The shape of the source electrode and the drain electrode is substantially a short side having a length L _S , a rectangle having a long side having a length W _S , a short side having a length L _D , and a long side having a length W _D , respectively. Can be considered as having a rectangle,
The shape of the gate insulating film, a short side of length L _G, so that it can be regarded as a rectangle having a long side length W _G, it is preferable to select a pattern of the electrodes.

Usually, the gate electrode, when selecting the shape of the source electrode and the drain electrode as described above, to one side of the rectangular pattern of the source electrode and the drain electrode, the long side length W _G of the rectangular pattern of the gate electrode is parallel Arrange as follows. For example, the long side length W _S of the rectangular pattern of the source electrode and the drain electrode, the long side length W _D is arranged such that a long side length W _G of the rectangular pattern of the gate electrode becomes parallel. At that time, the long side length W _S of the rectangular pattern of the source electrode and the drain electrode, the long side length W _D is shorter than the long side length W _G of the rectangular pattern of the gate electrode, also, the length The long side of W _{S and} the long side of length W _D are selected to be equal in length. That is, the selection is made so as to satisfy the condition of W _G > W _S = W _D. For example, W _G > W _S = W _D ≧ 1/2 · W _G , preferably W _G > W _S = W _D ≧ 2/3 · W _G is selected. For example, the long side of the length W _{S and} the long side of the length W _D of the rectangular pattern of the source electrode and the drain electrode are within the range satisfying the condition of W _G > W _S = W _D ≧ 2/3 · W _G , In the range of 70 μm to 250 μm.

On the other hand, the thin film layer of the organic semiconductor used as the operation layer of the organic thin film transistor has at least the channel region of the channel length L _channel substantially having the short side of the length L _{channel and} the long side of the length W _channel. Pattern so that it can be considered as a rectangular shape. The width of the channel region: W _channel is the gate electrode a gate width: narrower than W _G. Usually, the width of the channel region: W _channel is preferably smaller than the long sides of the long sides, the length W _D of the length W _S of the rectangular pattern of the source electrode and the drain electrode. That is, at least the condition of W _G > W _channel is satisfied, and preferably, the condition of W _G > W _S = W _D ≧ W _channel is satisfied. For example, the condition of _{W G> W S = W D} ≧ W channel ≧ 1/2 · W G, more preferably, satisfies the conditions of _{W G> W S = W D} ≧ W channel ≧ 2/3 · W G To choose. For example, the width of the channel region: W _channel is selected in a range of 70 μm to 250 μm within a range satisfying the condition of W _G > W _S = W _D ≧ W _channel ≧ 2/3 · W _G.

In the organic thin film transistor, the length of the channel region: L _channel corresponds to the distance between the side edges of the source electrode and the drain electrode on the gate electrode side: L _SD . When viewed from directly above the channel region, and a side edge of the gate electrode of the source electrode, the gap between the side edge of the gate electrode: a [Delta] L _SG, the side edge of the gate electrode side of the drain electrode, and the side edge of the gate electrode The sum of the gaps of ΔL _DG is (L _SD −L _G ) = (ΔL _SG + ΔL _DG ). Therefore, L _G ≧ (ΔL _SG + ΔL _DG ) ≧ 0, preferably 1/3 · L _G ≧ (ΔL _SG + ΔL _DG ) ≧ 0. For example, gate length: L _G is in the range of 5 m to 30 m, preferably, when it is selected in the range of _{7μm~20μm, (ΔL SG + ΔL DG} ) is in the range of 0Myuemu～20myuemu, preferably, the 0μm~10μm Select to range.

When forming a rectangular pattern of the source electrode and the drain electrode, the pattern drawing accuracy needs to be higher than the value of (ΔL _SG + ΔL _DG ). In other words, the pattern drawing accuracy is preferably selected so that the minimum space width is in the range of 1 μm to 10 μm. Further, it is preferable to maintain the pattern drawing accuracy so that the line width variation (fluctuation width from the straight line) to be drawn is in the range of 1 μm to 10 μm. When drawing using an ultra-fine inkjet printer, droplet diameter is applied so that the dot diameter (diameter) to which each droplet is applied is in the range of 0.5 μm to 5 μm, depending on the drawing accuracy. Set conditions.

  As the metal forming the gate electrode, the metal species conventionally used for forming the gate electrode of the organic thin film transistor can also be used in the present invention. In the method for producing an organic thin film transistor of the present invention, it is preferable to employ a metal selected from Au, Ag, Cu, Al, Cr, Ni, and Ti as a metal forming the gate electrode. When forming a gate electrode on a substrate, a technique of forming a metal thin film by using a vapor deposition method or a sputtering method and applying a photolithographic method to pattern a desired shape pattern can be used. Also, in the gate electrode forming step, the metal nanoparticle dispersion is applied in a predetermined pattern shape using an ultrafine inkjet printing apparatus to form a metal nanoparticle dispersion coating layer on the substrate, and the metal nanoparticle is applied. The particle dispersion coating layer can be heated and fired to form a gate electrode composed of a sintered body layer of metal nanoparticles.

As an insulating material for forming the gate insulating film, an insulating material conventionally used for forming a gate insulating film of an organic thin film transistor can be used in the present invention. In the method for producing an organic thin film transistor of the present invention, an inorganic insulating material such as SiO ₂ , SiN, Al ₂ O ₃ , or Ta ₂ O ₅ can be suitably used as the insulating material for forming the gate insulating film. The gate insulating film made of these inorganic insulating materials is formed by using the PE-CVD (Plasma-Enhanced Chemical Vapor Phase Deposition) method or sputtering method to form an insulating film with a desired film thickness and applying a photolithographic method. Thus, a method of patterning a desired shape pattern can be used. The thickness of the gate insulating film is selected within a range in which a desired gate breakdown voltage can be achieved in consideration of the relative dielectric constant: ε _{rI of} the insulating film to be used and the insulation resistance.

For example, when using SiO ₂ having a dielectric breakdown electric field strength: E _B = 3 MV / cm and a relative dielectric constant: ε _rI = 4 as an insulating material for forming the gate insulating film, the thickness of the gate insulating film: T _insulator is The maximum rated gate voltage V _G-MAX is preferably selected in the range of E _B <(V _G-MAX / T _insulator ).

The thickness of the gate electrode: T _gate is usually preferably selected to be thinner than the thickness of the gate insulating film covering the surface: T _insulator . That is, the selection is made so as to satisfy the condition of T _insulator ≧ T _gate . For example, the gate electrode satisfies the condition of 3/4 · T _insulator ≧ T _gate ≧ 1/8 · T _insulator , preferably 2/3 · T _insulator ≧ T _gate ≧ _1/6 · T _insulator. Thickness: T _gate is selected.

As long as the above conditions are satisfied, the gate insulating film thickness: T _insulator is thicker than the step (T _gate ) due to the side edge of the gate electrode. Covering with an insulating film is reliably achieved.

Or in the manufacturing method of the organic thin-film transistor of this invention, organic insulating materials, for example, insulating resin materials, such as an epoxy resin, can also be utilized as an insulating material which forms a gate insulating film. Even when an insulating resin material is used, the thickness of the gate insulating film is selected in a range where a desired gate breakdown voltage can be achieved in consideration of the relative dielectric constant: ε _{rI of} the insulating film to be used and the insulation resistance.

A thin film layer of an organic semiconductor formed on the gate insulating film is used as an operation layer. At that time, in the channel region, an effective channel layer is formed immediately above the gate electrode and at the interface between the gate insulating film and the organic semiconductor. That is, when the gate voltage: V _G applied to the gate electrode exceeds the threshold bias: V _th (V _G <V _th ), the drain current passing through the effective channel layer: I _d-ON Flows into the “ON state”.

  Also in the method for producing an organic thin film transistor of the present invention, when a thin film layer of an organic semiconductor is formed on a gate insulating film, a “self-assembled monolayer of an organic compound constituting the organic semiconductor ( It is preferable to use a method of forming “Self Assembled Monolayer (SAM)”. Regarding this technique, for example, US Pat. No. 6,433,359 (Patent Document 1), Frank-J. Meyer zu Heringdorf, et al. “Growth Dynamics of Pentacene Thin Films”, Nature Vol. 412 517 (2001) discloses the details.

  In the method of forming a “self-assembled monolayer” of an organic compound that constitutes an organic semiconductor, the organic compound is adsorbed on the surface of the gate insulating film when immersed in a monomolecular dispersion in which the organic compound is dispersed in a single molecule. With a single molecule as a nucleus, a monomolecular film grows in a “self-organized” lateral direction, and finally, a “self-assembled monomolecular film” having a regular molecular orientation is formed.

For example, when producing a “self-assembled monolayer” using n-octadecylphosphonic acid (C ₁₈ H ₃₇ P (═O) (OH) ₂ ) , the base insulation formed on the surface of the gate electrode It is preferable to fix n-octadecylphosphonic acid (C ₁₈ H ₃₇ P (═O) (OH) ₂ ) on the membrane. Specifically, it is preferable that fixation is performed via an ester bond between the hydroxy group (—OH) present on the surface of the base insulating film and the phosphonic acid . As a base insulating film used for this purpose, a film made of a metal oxide that can be formed by oxidizing a metal constituting a gate electrode, such as aluminum oxide, silver oxide, or tantalum oxide, is adopted. Is preferred.

  Subsequently, when an organic compound was deposited using the “self-assembled monolayer” as a base layer using a vacuum evaporation method, the deposited layer also maintained an ordered arrangement reflecting the regularity of the base layer. It becomes an organic semiconductor thin film layer.

  The method of forming a thin film layer of an organic semiconductor using this “self-assembled monolayer” as an underlayer is a low molecular type that can be evaporated because the deposition process on the underlayer uses a vacuum evaporation method. Applicable to organic semiconductor materials. For example, it can be suitably used to form a thin film layer of an organic semiconductor composed of acenes such as tetracene and pentacene, oligothiophene derivatives, and phthalocyanines. When the organic semiconductor layer to be produced is a layer made of pentacene, which is a typical p-type organic semiconductor, or hexadecafluorocopper phthalocyanine, which is a typical n-type organic semiconductor, this is a particularly effective means. Also in the manufacturing method of the organic thin-film transistor of this invention, it is preferable that the organic-semiconductor layer to produce is a layer which consists of a pentacene or hexadecafluoro copper phthalocyanine.

At that time, the switching operation of the target organic thin film transistor is “ON” when the gate voltage: V _G applied to the gate electrode exceeds the threshold bias: V _th (| V _G |> | V _th |). "Enhanced mode type". Therefore, when the gate voltage V _G applied to the gate electrode is V _G = 0V, no carrier exists in the organic semiconductor layer in the channel region immediately above the gate electrode (depletion state). It is necessary to be. The film thickness of the organic semiconductor layer to be produced: T _channel is selected within the range of the film thickness that satisfies the “depletion” condition.

The range of film thickness satisfying the condition of “depletion” is that the work function eψ (M _gate ) eV of the metal material M _gate of the gate electrode, and the electron affinity eχ (I _gate ) eV of the insulating material I _gate of the gate insulating film. Based on the relative permittivity: ε _rI , the electron affinity eχ (S _channel ) eV of the organic semiconductor and the relative permittivity: ε _r-OS , and the film thickness of the gate insulating film: T _insulator , the poisson is assumed. It can be calculated based on the numerical calculation of the equation. Actually, the concentration of the remaining carrier in the organic semiconductor itself is low, and the above-mentioned “depletion” condition is usually satisfied when the thickness of the organic semiconductor layer: T _channel is 10 nm or less.

It should be noted that the potential change of the conduction band (band bending) in the thickness direction of the organic semiconductor layer constituting the MIS structure when the gate voltage: V _G-ON applied to the gate electrode during the actual switching operation is applied. Occurs. As a result, carriers accumulate at the interface between the gate insulating film and the organic semiconductor layer and function as an effective channel layer. On the other hand, for example, on the uppermost surface of the n-type organic semiconductor layer, it is desirable that the conduction band energy level: E _C is maintained at a level sufficiently higher than at least the quasi-Fermi level (E _f ). The lower limit of the thickness of the organic semiconductor layer to be produced: T _channel is selected within the range of the thickness satisfying the above conditions. On the other hand, when the thickness of the organic semiconductor layer: T _channel is unnecessarily thick, there is no particular problem in operation, but the time required for its production becomes unnecessarily long.

Usually, it is preferable to select the film thickness of the organic semiconductor layer: T _channel in the range of 30 nm to 100 nm.

For example, when an organic semiconductor layer formed of pentacene, which is a p-type organic semiconductor material, is employed, the thickness of the organic semiconductor layer: T _channel is preferably selected in the range of 30 nm to 50 nm. Also, when employing an organic semiconductor layer formed of hexadecafluorophthalocyanine copper phthalocyanine is an n-type organic semiconductor material, the thickness of the organic semiconductor layer: T _channnel may be selected within the range of 30nm~50nm preferable.

  In the method of manufacturing an organic thin film transistor according to the first aspect of the present invention, the organic thin film transistor to be manufactured is formed so that the source electrode and the drain electrode are formed on the gate insulating film, and then the surface of the source electrode and the drain electrode is covered. An organic semiconductor film is formed on the gate insulating film.

Therefore, the organic semiconductor film is formed so as to cover the step portions corresponding to the film thicknesses T _S and T _D of the source electrode and the drain electrode and to cover the surfaces of the source electrode and the drain electrode. Therefore, the side end portions of the source electrode and the drain electrode on the gate electrode side have a shape having inclined side surfaces. The average inclination angles: θ _S and θ _D of the side surfaces having the inclination (taper) are preferably selected in the range of 70 ° ≧ θ _S ≧ 45 ° and 70 ° ≧ θ _D ≧ 45 °.

In order to more reliably cover the stepped portion, the film thicknesses T _S and T _D of the source electrode and the drain electrode may be selected to be not more than 10 times the film thickness T _channnel of the organic semiconductor layer. desirable. Usually, the film thicknesses T _S and T _D of the source electrode and the drain electrode are selected in the range of 50 nm to 1000 nm, preferably in the range of 100 nm to 300 nm.

In the method for manufacturing an organic thin film transistor according to the second aspect of the present invention, an organic thin film transistor to be manufactured is formed by forming an organic semiconductor film on a gate insulating film, and then providing a source electrode and a drain electrode on the surface of the organic semiconductor film. Form.

When used in a flat panel display device such as an actual liquid crystal display, it is covered with a surface protective film for the purpose of protecting the produced organic thin film transistor. Considering the covering of the surface protective film, the side end portions on the gate electrode side of the source electrode and the drain electrode have a shape having inclined side surfaces. The average inclination angles: θ _S and θ _D of the side surfaces having the inclination (taper) are preferably selected in the range of 70 ° ≧ θ _S ≧ 45 ° and 70 ° ≧ θ _D ≧ 45 °.

Considering the coverage of the step portion of the surface protective film, the film thicknesses T _S and T _D of the source electrode and the drain electrode are selected in the range of 50 nm to 1000 nm, preferably in the range of 100 nm to 300 nm.

  In the method of manufacturing the organic thin film transistor according to the first aspect of the present invention, when forming the source electrode and the drain electrode on the gate insulating film, the metal nanoparticle dispersion is formed into a predetermined pattern using an ultrafine inkjet printing apparatus. The metal nanoparticle dispersion coating layer is applied to a shape, and the metal nanoparticle dispersion coating layer is heated and fired to form a source electrode and a drain electrode composed of a sintered body layer of metal nanoparticles. The method is used.

  At that time, an ultrafine inkjet printing apparatus is used to apply a metal nanoparticle dispersion in a predetermined pattern shape to form a metal nanoparticle dispersion application layer, which is disclosed in International Publication No. 2005/025787. The metal nanoparticle dispersion is used.

  The metal nanoparticle dispersion disclosed in International Publication No. 2005/025787 is a metal nanoparticle dispersion that can be sprayed in the form of fine droplets and laminated. The average particle diameter of the metal nanoparticles is selected in the range of 1 to 100 nm, and the metal nanoparticle dispersion is a dispersion obtained by uniformly dispersing the metal nanoparticles in a dispersion solvent as a solid component. .

  The surface of the metal nanoparticle contains a nitrogen, oxygen, or sulfur atom as a group capable of coordinative bonding with the metal element contained in the metal nanoparticle, and is coordinated by a lone electron pair possessed by these atoms. It is coated with one or more compounds having a group capable of bonding, and a total of one or more compounds having a group containing nitrogen, oxygen, or sulfur atoms with respect to 100 parts by mass of the metal nanoparticles, Contains 50 parts by weight.

  On the other hand, the dispersion solvent is a kind of organic solvent or a mixed solvent composed of two or more kinds of liquid organic substances, and shows a uniform liquid state at least at a temperature of 15 ° C. or more, and constitutes the dispersion solvent. Alternatively, at least one of the two or more liquid organic substances has an affinity for one or more compounds having a group containing the nitrogen, oxygen, or sulfur atom. The liquid viscosity (20 ° C.) of the dispersion solvent itself is selected in the range of 10 mPa · s or less.

  In the metal nanoparticle dispersion, the volume ratio of the dispersion solvent is selected in the range of 55 to 80% by volume, and the liquid viscosity (20 ° C.) of the metal nanoparticle dispersion is 2 mPa · s to 30 mPa ·. The range of s is selected. In particular, a concentrated dispersion obtained by partially evaporating and removing the dispersion solvent contained in the metal nanoparticle dispersion and concentrating until the volume ratio of the dispersion solvent is in the range of 20 to 50% by volume, The liquid viscosity (20 ° C.) is characterized in that it becomes a viscous concentrate in the range of 20 Pa · s to 1000 Pa · s.

  For example, the metal nanoparticle dispersion liquid is dispersed in the liquid droplets after being ejected as fine liquid droplets by applying an ink jet printing method and then flying and depositing on the object. As the solvent evaporates, the viscosity of the concentrated liquid increases rapidly and becomes a viscous concentrated liquid at the time of landing.

  That is, when the metal nanoparticle dispersion liquid is sprayed as fine droplets on the gate insulating film, at least the average diameter of the droplets is set to 3 μm or less, thereby promoting the transpiration of the contained dispersion solvent. At the time of landing, the amount of the dispersion solvent remaining in the droplets of the metal nanoparticle dispersion liquid is significantly reduced, and the fluidity is extremely reduced accordingly. As a result, the droplets of the metal nanoparticle dispersion to be ejected are small, and the fluidity of the metal nanoparticle dispersion of the landed droplet is also lowered, so the metal nanoparticles formed per droplet The diameter of the application dots of the dispersion liquid is as very small as 0.5 μm to 5 μm. After that, since the coating film of the individual dispersed dots is also thin, the remaining dispersion solvent is instantly evaporated, and the metal nanoparticles that are densely stacked on the gate insulating film are narrow between the particles. It adheres as a high-viscosity material in which the dispersion solvent infiltrates only in the gaps. By repeating this dot coating operation, a metal nanoparticle coating film having a coating dot diameter can be laminated and formed on the gate insulating film.

  When the above-mentioned mechanism is used to form a coating layer of a dispersion liquid having a high liquid viscosity by spray-coating the metal nanoparticle dispersion liquid having a low liquid viscosity as fine droplets, the volume content ratio of the dispersion solvent The change in the liquid viscosity is preferably caused more rapidly with the change, and the average particle diameter is preferably selected in a smaller range. That is, it is more preferable to select the average particle diameter of the metal nanoparticles in the range of 1 to 20 nm. Further, the content of the metal nanoparticles contained in the initial dispersion of metal nanoparticles is selected to be 40% by mass or more, and the volume content ratio of the dispersion solvent is relatively ejected as fine droplets. Although the high fluidity required above can be achieved, it is preferable to set it as low as possible. On the other hand, if the volume content ratio of the dispersion solvent contained in the initial dispersion of metal nanoparticles is high, the evaporation of the solvent does not progress to the target value before landing after jetting. The particle dispersion still exhibits considerable fluidity. In that case, for example, it becomes difficult to form the side wall portion of the metal nanoparticle coating layer in a steep inclined structure.

  Below, the structure of the metal nanoparticle dispersion liquid suitably used in the present invention will be described in more detail.

  Since the metal nanoparticle dispersion draws a fine planar pattern of the source electrode and the drain electrode with high accuracy, the average particle diameter of the metal nanoparticles is 1 to 2 depending on the target minimum line width and planar shape size. Select within the range of 100 nm. Preferably, the average particle size is selected in the range of 1-20 nm. By selecting the average particle diameter of the contained metal nanoparticles themselves within the above range, application to an extremely fine line width pattern is enabled by an ultrafine ink jet printing apparatus.

  In order to prevent aggregation of metal nanoparticles in the dispersion, a coating layer made of a low molecule is provided on the surface of the metal nanoparticles and is dispersed in the liquid. That is, an oxide film is formed on the surface of the metal nanoparticles so that the coating layer on which the metal nanoparticle dispersion is laminated is heat-treated to cause fusion between the contained metal nanoparticles and the contact interface thereof. Use what is in a state that does not substantially exist.

  Specifically, the surface of the metal nanoparticle is composed of one or more compounds having a group containing nitrogen, oxygen, or sulfur atom as a group capable of coordinative bonding with the metal element contained in the metal nanoparticle. Covered. That is, the metal surface of the metal nanoparticle is uniformly formed by using one or more compounds having a group containing nitrogen, oxygen, or sulfur atom as a group capable of coordinately bonding with the metal element contained in the metal nanoparticle. For example, a dispersion of metal nanoparticles dispersed in one or more organic solvents is used while maintaining a state of being covered with, for example, an amine compound having one or more terminal amino groups.

  The role of this coating layer is to prevent aggregation of metal nanoparticles contained in the dispersion by keeping the metal surfaces in direct contact with each other until heat treatment is performed. It is to keep the cohesion resistance of the high. In addition, even when it is in contact with water or oxygen molecules in the atmosphere, such as when coating, the surface of the metal nanoparticles is already covered with a coating layer, leading to direct contact with water molecules and oxygen molecules. Therefore, it also has a function of suppressing the formation of a natural oxide film on the surface of metal ultrafine particles due to moisture and oxygen molecules in the atmosphere.

  The compound used for the uniform coating of the surface of the metal nanoparticle uses a group having a lone pair on a nitrogen, oxygen, or sulfur atom when forming a coordinate bond with the metal element. . For example, an amino group is mentioned as a group containing a nitrogen atom. Examples of the group containing a sulfur atom include a sulfanyl group (—SH) and a sulfide type sulfanediyl group (—S—). Examples of the group containing an oxygen atom include a hydroxy group (—OH) and an ether type oxy group (—O—).

  A representative example of the compound having an amino group that can be used is an alkylamine. Such an alkylamine is preferably one that does not desorb in a normal storage environment, specifically in a range not reaching 40 ° C., in a state in which a coordinate bond is formed with the metal element, and has a boiling point. A range of 60 ° C. or higher, preferably 100 ° C. or higher, and more preferably 150 ° C. or higher is preferable. On the other hand, when the heat treatment of the conductive nanoparticle paste is performed, it is necessary that the conductive nanoparticle paste can be vaporized together with the dispersion solvent after leaving the surface of the metal nanoparticles. An alkylamine having a boiling point that does not exceed 300 ° C., usually 250 ° C. or lower is preferable. For example, as the alkylamine, those having an alkyl group selected in the range of C8 to C18 and having an amino group at the end of the alkyl chain are used. For example, alkylamines in the range of C8 to C18 have thermal stability, and the vapor pressure near room temperature is not so high. When stored at room temperature or the like, the content is maintained within a desired range. It is preferably used in terms of handling properties, such as being easy to control.

  In general, in forming such a coordination bond, the primary amine type is preferable because it shows higher binding ability, but secondary amine type and tertiary amine type compounds can also be used. is there. In addition, compounds in which two or more adjacent amino groups are involved in bonding, such as 1,2-diamine type and 1,3-diamine type, can also be used. In addition, a polyamine type compound having a relatively small molecular weight that can be dissolved in a dispersion solvent can be used. In some cases, a chain amine compound containing a polyoxyalkyleneamine type ether type oxy group (—O—) in the chain may be used. In addition to the terminal amino group, a hydrophilic terminal group such as a hydroxylamine having a hydroxyl group, such as ethanolamine, can also be used.

  Moreover, alkanethiol can be mentioned as a typical example of a compound having a sulfanyl group (—SH) that can be used. In addition, such alkanethiol is preferably in a state in which a coordinate bond is formed with a metal element and does not desorb in a normal storage environment, specifically, in a range not reaching 40 ° C., and has a boiling point. A range of 60 ° C. or higher, preferably 100 ° C. or higher, and more preferably 150 ° C. or higher is preferable. On the other hand, when heat-treating the coating film of the metal nanoparticle dispersion liquid, it is necessary to be able to evaporate together with the dispersion solvent after leaving the surface of the metal nanoparticle. At least alkanethiol having a boiling point not exceeding 300 ° C., usually 250 ° C. or less is preferable. For example, as the alkanethiol, C4-C20 is used as the alkyl group, and more preferably C8-C18 is selected, and an alkyl chain having a sulfanyl group (—SH) is used. For example, alkanethiols in the range of C8 to C18 have thermal stability, and the vapor pressure near room temperature is not so high. When stored at room temperature or the like, the content is maintained and controlled within a desired range. It is preferably used in terms of handling properties, such as being easy to do. In general, primary thiol type compounds are preferred because they exhibit higher binding ability, but secondary thiol type and tertiary thiol type compounds can also be used. In addition, those in which two or more sulfanyl groups (—SH) are involved in binding, such as 1,2-dithiol type, can also be used. In addition, a polythioether type compound having a relatively small molecular weight that can be dissolved in a dispersion solvent can be used.

  Moreover, alkanediol can be mentioned as a representative of the compound which has a hydroxyl group which can be utilized. Examples include glycols such as ethylene glycol, diethylene glycol, and polyethylene glycol. A polyether type compound having a relatively small molecular weight that can be dissolved in a dispersion solvent can also be used. In addition, such alkanediols are preferably those that do not desorb in a normal storage environment, specifically in a range that does not reach 40 ° C., in a state in which a coordinate bond is formed with the metal element. A range of 60 ° C. or higher, usually 100 ° C. or higher, and more preferably 150 ° C. or higher is preferable. On the other hand, when heat-treating the multilayer coating layer containing metal nanoparticles, it is necessary to be able to evaporate together with the dispersion solvent after leaving the surface of the metal nanoparticles. Alkanediols having a boiling point not exceeding 300 ° C., usually 250 ° C. or less, are preferred. For example, those involving two or more hydroxy groups, such as 1,2-diol type, can be used more suitably.

  The metal nanoparticles contained in the metal nanoparticle dispersion include one or more compounds containing the above-described nitrogen, oxygen, or sulfur atoms, and having a group that can be coordinated by a lone pair of electrons of these atoms. Are dispersed in a dispersion solvent in a state of having a surface coating layer. Such a surface coating layer has an appropriate coating ratio so that unnecessary excessive coating molecules do not exist within a range in which it can function to avoid direct contact between the surfaces of the metal nanoparticles during storage. select. That is, when heated and fired at a low temperature, the coating layer molecules can be eluted and separated in the coexisting dispersion solvent, and the content can be achieved and the coating protection function can be achieved. Select the coverage ratio. For example, with respect to 100 parts by mass of metal nanoparticles, one or more compounds having the above-described nitrogen, oxygen, or sulfur atom and having a group capable of coordinated bonding by a lone electron pair possessed by these atoms as a sum total Generally, it is preferable to select the coating ratio so as to contain 10 to 50 parts by mass, more preferably 20 to 50 parts by mass. In addition, with respect to 100 parts by mass of the metal nanoparticle, the surface of the metal nanoparticle includes a nitrogen atom, an oxygen atom, or a sulfur atom, and a group capable of coordinative bonding by a lone electron pair possessed by these atoms. The sum total of one or more compounds also depends on the average particle size of the metal nanoparticles. That is, when the average particle diameter of the metal nanoparticles becomes smaller, the total surface area of the nanoparticle surface per 100 parts by mass of the metal nanoparticles increases in inverse proportion to the average particle diameter. Need a higher ratio. In consideration of this point, when selecting the average particle diameter of the metal nanoparticles in the range of 1 to 20 nm, the sum of the coating molecules covering the surface with respect to 100 parts by mass of the metal nanoparticles is: It is preferable to select in the range of 20 to 50 parts by mass.

  The organic solvent used as a dispersion solvent contained in the metal nanoparticle dispersion liquid has a role of dispersing the metal nanoparticles provided with the above-described surface coating layer at room temperature. It functions as a solvent capable of eluting and releasing the coating layer molecules on the particle surface. At that time, in the elution stage of the coating layer molecules in the heated state, a high-boiling liquid organic substance in which transpiration does not proceed remarkably is used. Accordingly, when heated to 100 ° C. or higher, preferably, 50 parts by mass or more of the compound having a group containing nitrogen, oxygen, or sulfur atoms covering the surface of the metal nanoparticles can be dissolved per 100 parts by mass of the dispersion solvent. In addition, one kind of organic solvent having high solubility or a mixed solvent composed of two or more kinds of liquid organic substances is used. In addition, when heated to 100 ° C. or higher, one kind of organic solvent capable of forming a compatible solution of any composition with respect to the compound having a group containing nitrogen, oxygen, or sulfur atoms that coats the surface of the metal nanoparticles, or It is more preferable to use a mixed solvent composed of two or more kinds of liquid organic substances, particularly those exhibiting high compatibility.

  Specifically, the coating layer molecule contains a nitrogen, oxygen, or sulfur atom, and is coordinated on the surface of the metal nanoparticle by using a group capable of coordinative bonding by a lone electron pair possessed by these atoms. doing. At that time, utilizing the affinity for the remaining hydrocarbon chain and skeleton, the organic solvent contained in the dispersion solvent can maintain the dispersion state of the metal nanoparticles covered with the coating layer molecules, or achieve compatibility with each other. Demonstrate the function. Although the affinity of the coating layer molecule due to the coordinate bond to the surface of the metal nanoparticle is stronger than physical adsorption, it rapidly decreases with heating. On the other hand, as a result of the increase in the solubility characteristic of the organic solvent accompanying the increase in temperature, when the mixture is heated to a temperature higher than the equilibrium temperature, the desorption and elution of coating layer molecules are accelerated at an accelerated rate as the temperature increases. Eventually, almost all of the coating layer molecules on the surface of the metal nanoparticles are dissolved in the dispersion solvent present during heating, and substantially no coating layer molecules remain on the surface of the metal nanoparticles. Is achieved.

  Of course, since the elution process of the coating layer molecules from the surface of the metal nanoparticles and the reattachment process are in a thermal equilibrium relationship, the solubility of the coating layer molecules in the dispersion solvent during heating is sufficiently high. desirable. Even if the coating layer molecules are eluted into the dispersion solvent infiltrating the gaps between the stacked metal nanoparticles, the coating layer molecules are transferred from the inside of the coating layer to the outer edge through the narrow gaps. It takes more time to spread and flow out. In order to effectively suppress the reattachment of the coating layer molecules during the progress of the sintering between the metal nanoparticles, it is desirable to use the organic solvent exhibiting the high solubility described above.

  That is, the organic solvent used as a dispersion solvent shows affinity for the coating layer molecules on the surface of the metal nanoparticles, but the coating layer molecules on the surface of the metal nanoparticles easily elute into the organic solvent near room temperature. Although it does not occur, the solubility increases with heating, and when the coating layer molecules can be eluted into the organic solvent when heated to 100 ° C. or higher, those are used. For example, a compound that forms a coating layer on the surface of metal nanoparticles, for example, an amine compound such as an alkylamine contains a chain hydrocarbon group that has an affinity with the alkyl group portion, It is preferable to select a nonpolar solvent or a low polarity solvent instead of a solvent having such a high polarity that the solubility of the amine compound is too high and the coating layer on the surface of the metal nanoparticles disappears even at around room temperature. In addition, even at the temperature at which the low-temperature baking treatment is performed, the thermal stability is high enough to prevent thermal decomposition, and the boiling point is at least 80 ° C. or higher, preferably 150 ° C. or higher. It is preferable that the temperature does not exceed 300 ° C. Moreover, when forming a fine line, it is necessary to maintain a metal nanoparticle dispersion liquid in a desired liquid viscosity range in the coating process by the inkjet method. In consideration of the handling property, the non-polar solvent or the low-polar solvent having a high boiling point, which does not easily evaporate near room temperature, such as alkanes having 10 to 18 carbon atoms, such as tetradecane, etc. C8-12 primary alcohols such as 1-decanol are preferably used. However, the liquid viscosity of the dispersion solvent itself used is at least 10 mPa · s (20 ° C.) or less, preferably a solvent having a range of 0.2 to 3 mPa · s (20 ° C.) is selected. desirable.

  On the other hand, the metal nanoparticle dispersion liquid is used for drawing a fine pattern by applying an ink jet method which is a method of spraying and applying as fine droplets. Therefore, it is necessary to prepare the metal nanoparticle dispersion liquid having a liquid viscosity suitable for the drawing technique employed. Specifically, in order to use an inkjet method for drawing a fine wiring pattern, it is desirable to select the liquid viscosity of the metal nanoparticle dispersion in the range of 2 to 30 mPa · s (20 ° C.). At that time, the volume ratio of the dispersion solvent in the dispersion is more preferably selected in the range of 55 to 80% by volume. On the other hand, when jetting fine droplets using the ink jet method, and then flying and landing on the coated surface, the dispersion solvent partially evaporates from the fine droplets, resulting in concentration, and the liquid The viscosity is desirably increased to 20 Pa · s to 1000 Pa · s (20 ° C.). At that time, the volume ratio of the dispersion solvent in the concentrated dispersion is more preferably in the range of 20 to 50% by volume. The liquid viscosity of the metal nanoparticle dispersion is determined depending on the average particle diameter of the metal nanoparticles to be used, the dispersion concentration, and the type of the dispersion solvent being used. The liquid viscosity can be adjusted.

  Specifically, the composition of the metal nanoparticle dispersion is such that when the volume ratio of the dispersion solvent in the dispersion is selected in the range of 55 to 80% by volume, the liquid viscosity is 2 to 30 mPa · s (20 ° C.), but if the amount of the dispersion solvent to be blended is reduced, the volume ratio of the dispersion solvent is in the range of 20 to 50% by volume, and a corresponding concentrated dispersion is prepared. The liquid viscosity exhibited by such a thick dispersion is preferably selected so as to be in the range of 20 Pa · s to 1000 Pa · s (20 ° C.).

  For example, as a dispersion solvent, in addition to the above-mentioned nonpolar solvent or low polarity solvent that exhibits a high boiling point, the liquid viscosity is adjusted, and when heated, it is useful for elution of coating layer molecules, while at around room temperature, A relatively low-polar liquid organic substance that exhibits a function of suppressing the separation of the coating layer molecules and a function of compensating for the separation can be added and blended. Such a low-polarity liquid organic substance added and blended can achieve uniform mixing with the main solvent component, and the boiling point of the liquid organic material should be as high as the main solvent component. desirable. For example, when the main solvent component is a primary alcohol having 8 to 12 carbon atoms, such as 1-decanol, branched diols such as 2-ethyl-1,3-hexanediol, When the main solvent component is an alkane having 10 to 18 carbon atoms, such as tetradecane, a dialkylamine having a branch such as bis-2-ethylhexylamine is supplementally added and blended. It can be used as a low-polar liquid organic material.

  The metal nanoparticle dispersion does not contain acid anhydrides or the like that are reactive with binder resin components and coating molecules, such as thermosetting epoxy resin components that undergo polymerization and cure when heated. As a result, even in the process of proceeding with the low-temperature baking treatment, no polymer is formed inside, and the factors that significantly reduce the fluidity of the dispersion solvent itself are eliminated.

During the heat treatment, the coating layer molecules such as alkylamine coating the surface of the metal nanoparticles are eluted and separated from the dispersion solvent, and the coating layer that has suppressed the aggregation of the metal nanoparticles disappears. As a result, the metal nanoparticles are gradually fused and agglomerated by fusion, and finally a random chain is formed. At this time, the low-temperature sintering of the metal nanoparticles proceeds, the space between the metal nanoparticles decreases, the entire volume shrinks, and the random chains achieve close contact with each other. When the space between the metal nanoparticles decreases, the dispersion solvent that occupies this space maintains fluidity, so even if the space between the metal nanoparticles becomes a bottleneck, it is pushed out to the outside. The whole volume shrinkage proceeds. The heat treatment temperature in this low-temperature firing process is selected within a temperature range that does not damage the organic semiconductor layer. Specifically, it is preferable to select a temperature lower than the heating temperature of the vapor deposition source of the organic semiconductor material when the organic semiconductor layer is manufactured. Therefore, the heat treatment temperature in the low-temperature firing process is usually selected to be 250 ° C. or lower, preferably in the range of 100 ° C. to 230 ° C., more preferably in the range of 130 ° C. to 200 ° C. At that time, the coating layer molecules are eluted and separated in the above-mentioned dispersion solvent, and the obtained sintered metal nanoparticles have a smooth surface without surface irregularities reflecting non-uniform aggregation of metal nanoparticles. Show shape. In addition, the conductor layer is denser and has a very low resistance, for example, a volume resistivity of 10 × 10 ⁻⁶ Ω · cm or less. On the other hand, as the entire volume shrinks, the dispersion solvent extruded to the outside and the coating layer molecules dissolved in the solvent gradually evaporate while continuing to heat, and finally the resulting metal nanoparticles are sintered. The amount of organic matter remaining in the body is limited. Specifically, as a binder resin component, a thermosetting resin component that remains in the sintered body of the obtained metal nanoparticles after the low-temperature firing step and becomes a constituent element of the conductor layer, etc. Since it does not contain, the volume occupation rate of the sintered body of the metal nanoparticles in the conductor layer itself is high. As a result, in addition to the low volume resistivity of the sintered body of metal nanoparticles itself, the thermal conductivity of the entire conductor layer is also greatly improved due to the high volume occupancy of the metal body. . From the advantages of both, the formation of a fine sintered body layer using the metal nanoparticle dispersion is more suitable for forming a fine wiring pattern when the flowing current density is high.

In the method for producing an organic thin film transistor according to the present invention, a conductor layer made of a sintered body of metal nanoparticles formed by the low-temperature baking treatment is used for forming a source electrode and a drain electrode. Therefore, the metal species constituting the metal nanoparticles to be used are selected from metal species suitable for the source electrode and the drain electrode for the organic semiconductor layer. For example, the metal nanoparticles dispersed in the metal nanoparticle dispersion are selected from the group of metals consisting of gold, silver, copper, platinum, palladium, nickel, tantalum, bismuth, indium, tin, titanium, and aluminum. A nanoparticle composed of one type of metal, a mixture of nanoparticles composed of two or more types of metals, or a nanoparticle composed of an alloy of two or more types of metals selected from the group of the metals. preferable.

  For example, in the case of an organic semiconductor layer formed of pentacene, the metal nanoparticles are selected from the group of metals consisting of gold, silver, copper, platinum, palladium, or a single type of metal, or Nanoparticles made of an alloy of two or more metals selected from the metal group are preferred. In the case of an organic semiconductor layer formed of hexadecafluorocopper phthalocyanine, the metal nanoparticles are selected from the group of metals consisting of gold, silver, copper, platinum, palladium, and are made of a single type of metal. Nanoparticles made of an alloy of two or more metals selected from the group of particles or the metal are preferred.

The film thicknesses T _S and T _D of the source electrode and drain electrode to be produced are selected in the range of 50 nm to 1000 nm, preferably in the range of 100 nm to 300 nm. Correspondingly, the average particle diameter D (diameter) of the metal nanoparticles used for the production of the sintered body of the metal nanoparticles is a range of 1/20 or less with respect to T _S and T _D , Preferably, it is desirable to select in the range of 1/30 or less. For example, the average particle diameter D (diameter) of the metal nanoparticles is preferably selected in the range of 1 to 20 nm.

  It is more preferable to select one of gold, silver, copper, platinum, and palladium, which are excellent in ductility and malleability, in addition to high conductivity, as the metal species constituting the metal nanoparticle. Alternatively, it is more preferable to use silver nanoparticles. For example, when using gold nanoparticles or silver nanoparticles, the average particle diameter of such metal nanoparticles: D (diameter) is selected in the range of 1 to 20 nm and included in the original metal nanoparticle dispersion. It is more desirable that the content of the metal nanoparticles be selected to be 40% by mass or more.

In a conductor layer made of a sintered body of metal nanoparticles formed by a low-temperature firing process, a minute uneven structure resulting from the average particle diameter: D (diameter) of metal nanoparticles remains on the surface. The minute concavo-convex structure is about 1/8 to 1/4 of the average particle diameter of metal nanoparticles: D (diameter). When the average particle diameter of the metal nanoparticles: D (diameter) is selected in the range of 1 to 20 nm, the fine concavo-convex structure is at most 5 nm or less, and the organic semiconductor layer is formed so as to cover the upper surface thereof. This is a range that does not substantially cause a problem. That is, the size of the fine concavo-convex structure does not exceed 1/10 with respect to the thickness of the organic semiconductor layer: T _channel , and when the organic semiconductor layer is laminated, the fine concavo-convex structure is embedded. It becomes a shape.

  Moreover, when the metal nanoparticle dispersion liquid is sprayed as fine droplets onto the gate insulating film, at least the average diameter of the droplets is set to 3 μm or less, thereby promoting the transpiration of the contained dispersion solvent. At the time of landing, the amount of the dispersion solvent remaining in the droplets of the metal nanoparticle dispersion liquid is significantly reduced, and the fluidity is extremely reduced accordingly. As a result, the droplets of the metal nanoparticle dispersion to be ejected are small, and the fluidity of the metal nanoparticle dispersion of the landed droplet is also lowered, so the metal nanoparticles formed per droplet The diameter of the application dots of the dispersion liquid is as very small as 0.5 μm to 5 μm.

  Therefore, since the diameter of the coating dot of the metal nanoparticle dispersion formed per droplet is 0.5 to 5 μm, the minimum line width of the coating layer of the metal nanoparticle is the size of the coating dot. It is possible to make it about twice the diameter.

  Accordingly, when forming a rectangular pattern of the source electrode and the drain electrode, the pattern drawing accuracy is such that the minimum line width is about twice the diameter of the application dot, that is, the range of 1 μm to 10 μm. It is possible to select the diameter. In other words, the pattern drawing accuracy can be selected so that the minimum space width is in the range of 1 μm to 10 μm. Moreover, the variation in the line width to be drawn (the fluctuation width from the straight line) can be in the range of 1 μm to 10 μm.

  The diameter of the metal nanoparticle application dots formed per droplet is determined by the size of the droplets ejected by the inkjet method. When the diameter of the coating dot of the metal nanoparticle dispersion formed in one droplet using the metal nanoparticle dispersion is in the range of 0.5 μm to 5 μm, the size of the ejected droplet The (diameter) is in the range of 0.3 μm to 3 μm. In order to achieve this droplet discharge condition, in the present invention, the size (diameter) of the discharged droplet is set in the range of 0.3 μm to 3 μm using an ultrafine inkjet printing apparatus.

  Actually, when the size (diameter) of the ejected droplet is in the range of 0.3 μm to 3 μm, the transpiration of the dispersion solvent contained from the surface is promoted during the flight of the droplet, and the landing At that time, the amount of the dispersion solvent remaining in the droplets of the metal nanoparticle dispersion liquid is significantly reduced, and the fluidity is extremely reduced accordingly. Immediately before landing, the size (diameter) of the droplet is significantly smaller than the range of 0.3 μm to 3 μm, and the fluidity is extremely reduced. The range is 5 μm to 5 μm. When the volume of the droplet decreases to 80% as the dispersion solvent evaporates, the average height of the coating dot is the diameter of the coating dot when the coating dot diameter is in the range of 0.5 μm to 5 μm. Of about 1/8.

When drawing using the above-described metal nanoparticle dispersion using an ultrafine inkjet printing apparatus, each metal nanoparticle dispersion has a high liquid viscosity dispersion on the surface. No further spreading occurs. Therefore, the side wall surface of the drawn coating layer of the metal nanoparticle dispersion is in a state of showing a steep inclination angle. The inclination angle: θ _d can be in the range of 80 ° ≧ θ _d ≧ 60 °. Thereafter, when a low-temperature firing treatment is performed, the fusion of the metal nanoparticles proceeds, and the film thickness of the coating layer; T _d decreases from the film thickness of the sintered layer of the metal nanoparticles: T _baked . The reduction ratio: T _baked / T _d is about 3/4 to 3/5. Therefore, the side wall surface in the sintered body layer of metal nanoparticles also has a steep inclination angle. The inclination angle: θ _baked can be in the range of 70 ° ≧ θ _baked ≧ 45 °.

  A method for preparing the metal nanoparticle dispersion used in the present invention will be described below.

  In the metal nanoparticles, the heat treatment temperature in the low-temperature firing process is 250 ° C. or less, and preferably selected from the range of 100 ° C. to 230 ° C. The body can be formed. Furthermore, even near room temperature, these metal nanoparticles tend to fuse and aggregate with each other when the metal surface is brought into direct contact. Therefore, for example, using a commercially available metal nanoparticle dispersion as a raw material, the dispersion solvent is converted into a desired organic solvent, and the content ratio of the appropriate dispersion solvent and the liquid viscosity are adjusted to achieve the target composition. When preparing the metal nanoparticle dispersion, it is desirable to use, for example, the following procedure.

  As a metal nanoparticle dispersion used as a raw material, the surface of metal nanoparticles is coated and protected with a surface coating molecule such as alkylamine, and the solubility of the surface coating molecule such as alkylamine is poor and can be distilled off. The metal nanoparticles coated with the surface coating molecules are uniformly dispersed in a nonpolar solvent or a low polarity solvent, preferably a nonpolar solvent having a boiling point of at least 150 ° C. or a low polarity solvent. Use things. First, the dispersion solvent contained in the metal nanoparticle dispersion is removed while suppressing the separation of surface coating molecules such as alkylamine.

  For removing the dispersion solvent, a vacuum distillation method is suitable. During this vacuum distillation, in order to suppress the detachment of the surface coating molecules on the surface of the metal nanoparticles, the coating layer may be removed as necessary. Distillation under reduced pressure can be carried out after adding and mixing a protective solvent component having a higher affinity for the molecule and having a boiling point significantly higher than that of the dispersion solvent distilled under reduced pressure. For example, when the dispersion solvent to be distilled off under reduced pressure is toluene, and a dodecylamine that is an alkylamine is used as the coating layer molecule of the metal nanoparticles, a diol-based solvent, for example, It is possible to add a small amount of various glycols such as dipropylene glycol, diethylene glycol, propylene glycol, and ethylene glycol. In addition, in addition to alkylamine, which is used as a metal nanoparticle coating layer molecule, such as dodecylamine, it can be used as a metal nanoparticle coating layer molecule, and another amine having a higher boiling point should be added. You can also. These other types of amines can also be used for the purpose of substituting a part of the coating layer molecules of the metal nanoparticles present initially when the dispersion solvent is distilled off under reduced pressure. The molecular component of the coating layer to be substituted, such as this different type of amine, has an affinity with a solvent component for protection such as various glycols, and at the same time has a group capable of coordinating bonding such as an amino group. A liquid organic compound having a high boiling point can be used. For example, 2-ethylhexylamine and Jeffamine EDR148 (2,2- (ethylenedioxy) bisethylamine) can be used.

  In the process of preparing the metal nanoparticle dispersion liquid, when the dispersion solvent is converted to a nonpolar solvent or a low polarity solvent having a high boiling point as described above and redispersed, other than metal nanoparticles having a coating layer on the surface In some cases, the coating layer may be missing and the agglomerated metal nanoparticle mass may be mixed, and a redispersed liquid with uniform dispersion may be added to a sub-micron pore size filter, for example, a 0.2 μm membrane. It is desirable to perform a treatment for removing the metal nanoparticle mass that has been aggregated by filtering with a filter. By performing this filtration treatment, it is prepared with high certainty by a highly fluid dispersion liquid in which metal nanoparticles having a coating layer on the surface are uniformly dispersed in a target high boiling point dispersion solvent.

  In the method for producing an organic thin film transistor according to the present invention, when forming a coating film of the above-mentioned metal nanoparticle dispersion by applying an ink jet printing method, the size (diameter) of ejected droplets is further refined. An ultra-fine inkjet printing apparatus is used.

The metal nanoparticle dispersion used in the present invention has a coating molecular layer on the surface of the metal nanoparticle. When the liquid temperature of the dispersion is increased, the organic compound molecules constituting the coating molecular layer are dispersed. Elute in the solvent. In order to avoid this phenomenon, it is not possible to employ a thermal method that raises the liquid temperature of the dispersion liquid when ejecting fine droplets in the inkjet printing method. Therefore, an electrostatic attraction method, which is a method for ejecting fine droplets without increasing the liquid temperature of the dispersion, is employed. In particular, it utilizes the fact that the liquid volume: V _O of ejected microdroplets can be controlled by controlling the opening diameter of the nozzle tip and the applied voltage, which is a feature of the electrostatic suction method. The ejected microdroplet becomes substantially spherical due to its surface tension, and its size (diameter): D _O has a relationship of V _O = (4/3) π · (D _O / 2) ³ Satisfied. At that time, the opening diameter (diameter) of the nozzle tip that discharges microdroplets: D _open is in the range of D _O > D _open ≧ 1/3 · D _O. For example, the size of the fine liquid droplets discharged (diameter): The D _O, when selecting the 0.3 [mu] m, the opening diameter of the nozzle tip (diameter): D _open is, 0.3μm> D _open ≧ 0. The range is 1 μm.

In the ultra-fine inkjet printing apparatus used in the present invention, the opening diameter (diameter): D _open at the nozzle tip for discharging the fine droplets is selected in the range of 0.1 μm to 1 μm, for example.

  An electrostatic suction type ultra-fine inkjet printing apparatus that employs the operating principle of the ultra-fine fluid jet apparatus disclosed in Japanese Patent Application Laid-Open No. 2004-164487 can be suitably used for the above-described purpose. In the ultrafine fluid jet apparatus described in Japanese Patent No. 3975272, the nozzle formed of an insulator has an extremely small opening with a nozzle tip opening diameter in the range of 10 nm to 8,000 nm, for example, in the range of 100 nm to 1000 nm. This nozzle is selectable for the aperture. On the other hand, the distance between the nozzle tip and the application target surface is selected to be 100 μm or less, for example.

In consideration of the minimum pattern size of the fine pattern to be drawn, the opening diameter (diameter): D _open at the nozzle tip is appropriately selected in the range of 10 nm to 8,000 nm.

On the other hand, the average particle diameter D (diameter) of the metal nanoparticles contained in the metal nanoparticle dispersion that is discharged as fine droplets using the ultrafine inkjet printing nozzle is at least the tip of the nozzle opening diameter (diameter): based on the D _open, selected within the range of _{1/2 · D open ≧ D} . Usually, the average particle diameter D (diameter) of the metal nanoparticles is 1/5 · D _open ≧ D ≧ 1/200 · D _open , preferably based on the opening diameter (diameter) of the nozzle tip: D _open. Is selected in the range of 1/10 · D _open ≧ D ≧ 1/100 · D _open .

  Further, the insulating nozzle tip having such a fine opening diameter has a tapered inner wall surface structure in which the hole diameter inside the nozzle gradually decreases from the tube inner diameter of the base to the opening diameter of the nozzle tip. Shall. In addition, in general, the wall surface layer thickness (wall thickness) of the nozzle is uniform in the radial direction, so that the inner wall surface and the outer surface have a concentric shape. In addition, the nozzle tip is designed to have a pointed outer shape having an inner wall surface structure and an outer surface structure having rotational symmetry from the opening at the nozzle tip to the hole at the base, and having the same central axis.

  An electrode that contacts the metal nanoparticle dispersion and applies an electric field to the dispersion is disposed inside the nozzle tip. An electrode is also provided on the outer surface of the tip of the nozzle, and an electric field is applied to the metal nanoparticle dispersion by a voltage applied between the electrode and the electrode inside the nozzle.

  In general, it is desirable that the thickness (wall thickness) of the wall surface layer of the nozzle is selected within a range that does not exceed the pipe wall thickness of the introduction pipe at the end of the liquid introduction pipe section to be connected at the nozzle base. Then, the thickness (wall thickness) of the wall surface layer is gradually reduced as the nozzle is advanced. Even at the tip part where the wall surface layer thickness (thickness) is the thinnest, the thickness (thickness) is set according to the material constituting the nozzle so as to satisfy the mechanical strength required for the nozzle. Select as appropriate.

  As a metal nanoparticle dispersion liquid to be ejected from the nozzle and applied, metal nanoparticles having an average particle diameter of 1 to 100 nm, preferably an average particle diameter of 1 to 20 nm, for example, as the metal element, gold, silver, copper, Dispersions containing metal nanoparticles made of simple metals such as platinum, palladium, nickel, aluminum, or alloys thereof are used. The dispersion liquid containing the metal nanoparticles is discharged as a dispersion liquid having a liquid viscosity of 2 mPa · s to 30 mPa · s (20 ° C.). Since the inner wall surface of the nozzle comes into contact with the solid dispersion medium during ejection, it is desirable that the nozzle inner wall surface be made of an insulating material having a certain level of wear resistance. That is, as the insulating material of the nozzle, a material that satisfies such requirements as hardness, wear characteristics, mechanical strength against elastic deformation, and breakdown electric field strength is used.

When the opening diameter (diameter) of the nozzle tip: _Dopen is 200 nm, the size (diameter): D _O of the ejected microdroplet is estimated to be about 1 μm, and the liquid volume of the microdroplet: V _O corresponds to about 0.7 fL.

  Therefore, when using the ultra-fine inkjet printing apparatus that uses the above-described fine-bore nozzle, it is preferable to select the liquid volume of the discharged fine droplets in the range of 0.3 femtoliter to 1 femtoliter.

  In the method for producing an organic thin film transistor according to the second aspect of the present invention, the organic thin film transistor to be produced is formed by forming an organic semiconductor film on the gate insulating film, and then forming a source electrode and a drain electrode on the surface of the organic semiconductor film. Form.

  At that time, in the step of forming the organic semiconductor film on the gate insulating film, the technique used in the method for manufacturing the organic thin film transistor according to the first embodiment can be used. Furthermore, when a thin film layer of an organic semiconductor is formed on the gate insulating film, a method of previously forming a “self-assembled monomolecular film” of an organic compound constituting the organic semiconductor on the surface of the gate insulating film is used. Is preferred.

  In addition, also in the step of forming the source electrode and the drain electrode on the surface of the organic semiconductor film, the technique used in the method for manufacturing the organic thin film transistor according to the first embodiment can be used.

At that time, a coating film of the metal nanoparticle dispersion liquid is formed on the surface of the organic semiconductor film having a film thickness of T _channel . The coating film of the metal nanoparticle dispersion contains a dispersion solvent, but at the time of application, a part of the dispersion solvent has been removed by evaporation. For this reason, the amount of the organic semiconductor eluted in the remaining dispersion solvent is small. Further, when the dispersion solvent is evaporated during the low-temperature baking treatment, the eluted organic semiconductor is re-deposited at the interface between the organic semiconductor film and the sintered layer of the metal nanoparticles to be formed.

  As a result, in the vicinity of the interface where the sintered layer of the metal nanoparticles is in contact with the surface of the organic semiconductor film once formed, organic semiconductor molecules are partially caused by elution and reprecipitation of the organic semiconductor film. Disturbance is introduced into the orientation of the film. However, the orientation of the organic semiconductor molecules in the vicinity of the interface between the organic semiconductor film and the gate insulating film is maintained even in the region immediately below the source electrode and the drain electrode.

  Further, wetting and spreading of the dispersion solvent around the coating film of the metal nanoparticle dispersion liquid is also suppressed. Therefore, the organic semiconductor film formed in the channel region sandwiched between the source electrode and the drain electrode has substantially no influence.

  Hereinafter, the present invention will be described more specifically with reference to examples. Although these examples are examples of the best mode of the present invention, the present invention is not limited to these specific examples.

Example 1
Example 1 is an example in which an organic thin film transistor using an organic semiconductor layer made of pentacene as an operating layer is manufactured by applying the method for manufacturing an organic thin film transistor according to the first aspect of the present invention.

  The organic thin film transistor manufactured in Example 1 has the following configuration.

  As the substrate 1, a polyethylene terephthalate film substrate having a thickness of 500 μm is used. Alternatively, a glass substrate having a thickness of 500 μm is used.

In the gate electrode 2, the shape of the channel region portion used for the switching operation of the TFT is rectangular. In the rectangular shape, the gate length: L _G is the 1 [mu] m, the gate width: W _G is selected 300 [mu] m. The metal species of the gate electrode 2 is aluminum, and a deposited film having a film thickness: T _gate = 20 nm is patterned into the above-described shape pattern.

A gate insulating film 3 made of a self-assembled monolayer (SAM film) / AlO _x is formed so as to cover the gate electrode 2 and cover the entire surface of the substrate 1. At that time, the thickness of AlO _x layer immediately above the gate electrode 2: T _AlOx has a T _AlOx = 3.6 nm. In the region on the surface of the substrate 1, a self-assembled monomolecular film (SAM film) is formed on the AlO _x film, and the film thickness of the SAM film is 2.1 nm.

  A coating film of a metal nanoparticle dispersion for forming the source electrode 4 and the drain electrode 5 is formed on the gate insulating film 3 at a position sandwiching the gate electrode 2. The metal nanoparticle dispersion was prepared by forming a coating molecular layer of dodecylamine (melting point: 28.3 ° C., boiling point: 248 ° C.) on the surface of silver nanoparticles having an average particle diameter D: 3 nm. (Tetradecane, viscosity 2.0-2.3 mPa · s (20 ° C.), melting point 5.86 ° C., boiling point 253.57 ° C., manufactured by Nikko Petrochemical Co., Ltd.). In the metal nanoparticle dispersion, 20 parts by mass of the coating molecule dodecylamine and 52 parts by mass of N14 as the dispersion solvent are contained per 100 parts by mass of the silver nanoparticles. The liquid viscosity of the silver nanoparticle dispersion is 10 mPa · s (20 ° C.).

Using silver nanoparticle dispersion of the bore diameter of the discharge hole of the ultra-fine inkjet device: Select D _open to 0.2 [mu] m, and set the droplet volume to be injected into 0.7FL, to form a coating film . Assuming that a droplet having a droplet volume V _{O of} 0.7 fL at the time of ejection has a spherical shape, the droplet diameter: D _O (diameter) corresponds to 1 μm. Under these coating conditions, the average diameter of dots drawn with one droplet of 0.7 fL of droplet volume at the time of ejection is 1 to 2 μm.

The shape of the coating film of the metal nanoparticle dispersion liquid for forming the source electrode 4 is a rectangle having a short side: L _S = 2 μm and a long side: W _S = 300 μm, and the thickness of the coating film: T _S-draw is 0. 3 μm is selected. Spacing and long sides of the rectangular pattern of the coating film, the side edge of the source electrode side of the gate electrode 3: [Delta] L _SG is selected [Delta] L _SG = 1 [mu] m.

The shape of the metal nanoparticle dispersion liquid coating film for forming the drain electrode 5 is a rectangle having a short side: L _D = 2 μm and a long side: W _D = 300 μm, and the thickness of the coating film: T _D-draw is 0. 3 μm is selected. The distance between the long side of the rectangular pattern of the coating film and the side edge of the gate electrode 3 on the drain electrode side: ΔL _DG is selected to be ΔL _DG = 1 μm.

  The metal nanoparticle dispersion coating film is subjected to a low-temperature baking treatment in a nitrogen gas stream at a temperature of 130 ° C. for 60 minutes to obtain a sintered layer of silver nanoparticles.

Separately, in a sintered body layer of rectangular silver nanoparticles having a width of 2 μm and a length of 100 μm, which is produced under the same conditions on a SAM film used as a gate insulating film, the average film thickness of the sintered body layer: When T _baked is measured, it is 0.3 μm. The resistivity of the silver nanoparticle sintered body layer was 25 μΩ · cm.

A sintered layer of silver nanoparticles obtained by a low-temperature firing treatment is used as the source electrode 4 and the drain electrode 5. Accordingly, the film thicknesses T _S and T _D of the source electrode 4 and the drain electrode 5 are estimated to be 0.3 μm on average. In addition, the line width disturbance (small irregularities): δL _S and δL _D at each side of the rectangular pattern of the silver nanoparticle sintered body layer is estimated to be 100 nm.

Distance between the produced source electrode 4 and drain electrode 5: L _SD was 2 μm. The design value of the length of the channel region: L _channel = 3 μm, but the difference (L _channel −L _SD ) was only 1 μm.

The formation of the gate insulating film 3 made of self-assembled monomolecular film (SAM film) / AlO _x is performed in the following steps. First, plasma oxidation is performed on the surface of the Al gate electrode 2 to form an AlO _x layer on the Al surface. Thereafter, when a water washing treatment is performed, Al—OH type hydroxy groups are present at a high density on the surface of the AlO _x layer. Thereafter, it is immersed in a monomolecular dispersion solution to form a monomolecular film on the surface of the AlO _x layer in a self-composing manner. The monomolecular dispersion solution is obtained by dispersing n-octadecylphosphonic acid (C ₁₈ H ₃₇ P (═O) (OH) ₂ ) in a dispersion solvent 2-propanol at a dispersion concentration of 1% by mass or more. After immersing in the monomolecular dispersion solution having a liquid temperature of 30 ° C. for 12 hours, the solution is taken out and the remaining dispersion is removed by nitrogen blowing. n- octadecyl phosphonic acid _{(C 18 H 37 P (=} O) (OH) 2) is reacted with Al-OH type hydroxy groups of the AlO _x layer surface, result in the formation of an ester bond, the AlO _x layer surface A self-assembled monolayer is formed.

Pentacene is deposited on the surface of the gate insulating film 3 on which the “self-assembled monolayer” is formed on the surface of the AlO _x layer by vapor deposition. The film thickness of the deposited pentacene vapor deposition film: T _channel is selected to be 30 nm. As the pentacene vapor deposition conditions, a pentacene vapor deposition source temperature of 230 ° C. and a substrate temperature of 60 ° C. are selected. The film thickness of the deposited pentacene vapor film: T _channel is separately prepared on the SAM film / AlO _x laminated film used for the gate insulating film under the same vapor deposition conditions, and the vapor deposition time and vapor deposition. This is an estimated value based on the result of measuring the correlation of film thickness. At that time, the thickness of the pentacene vapor-deposited film can be measured by ellipsometry, assuming that the relative refractive index of the pentacene vapor-deposited film is equal to the relative refractive index of the solid.

Finally, the organic semiconductor layer 6 is patterned into a rectangular shape having a predetermined pattern shape, length: L _OS = 300 μm, and width: W _OS = 300 μm.

The threshold voltage: V _th of the produced organic thin film transistor was measured under the condition of drain-source voltage V _DS = −2.5V. The threshold voltage of the organic thin film transistor was measured as V _th = −0.5V. Also, “ON state”: drain current I _d-ON when applying a gate voltage: V _G−ON = −3 V, and “OFF state”: drain current I when applying a gate voltage: V _G−OFF = 0V The ratio of _d-ON , ON / OFF current ratio: I _d-ON / I _d-OFF was about 1 × 10 ⁶ .

(Example 2)
Example 2 is an example in which an organic thin film transistor using an organic semiconductor layer made of hexadecafluorocopper phthalocyanine as an operating layer is manufactured by applying the method for manufacturing an organic thin film transistor according to the first aspect of the present invention.

  The organic thin film transistor manufactured in Example 2 has the following configuration.

  As the substrate 1, a polyethylene terephthalate substrate having a thickness of 500 μm is used. Alternatively, a silicon oxide film / Si substrate having a thickness of 500 μm is used.

In the gate electrode 2, the shape of the channel region portion used for the switching operation of the TFT is rectangular. In the rectangular shape, the gate length: L _G is the 1 [mu] m, the gate width: W _G is selected 300 [mu] m. The metal species of the gate electrode 2 is aluminum, and a deposited film having a film thickness: T _gate = 20 nm is patterned into the above-described shape pattern.

A gate insulating film 3 made of a self-assembled monolayer (SAM film) / AlO _x is formed so as to cover the gate electrode 2 and cover the entire surface of the substrate 1. At that time, the thickness of AlO _x layer immediately above the gate electrode 2: T _AlOx has a T _AlOx = 3.6 nm. In the region on the surface of the substrate 1, a self-assembled monomolecular film (SAM film) is formed on the AlO _x film, and the film thickness of the SAM film is 2.1 nm.

  A coating film of a metal nanoparticle dispersion for forming the source electrode 4 and the drain electrode 5 is formed on the gate insulating film 3 at a position sandwiching the gate electrode 2. The metal nanoparticle dispersion was prepared by forming a coating molecular layer of dodecylamine (melting point: 28.3 ° C., boiling point: 248 ° C.) on the surface of silver nanoparticles having an average particle diameter D: 3 nm. (Tetradecane, viscosity 2.0-2.3 mPa · s (20 ° C.), melting point 5.86 ° C., boiling point 253.57 ° C., manufactured by Nikko Petrochemical Co., Ltd.). In the metal nanoparticle dispersion, 20 parts by mass of the coating molecule dodecylamine and 52 parts by mass of N14 as the dispersion solvent are contained per 100 parts by mass of the silver nanoparticles. The liquid viscosity of the silver nanoparticle dispersion is 10 mPa · s (20 ° C.).

Using silver nanoparticle dispersion of the bore diameter of the discharge hole of the ultra-fine inkjet device: Select D _open to 0.2 [mu] m, and set the droplet volume to be injected into 0.7FL, to form a coating film . Assuming that a droplet having a droplet volume V _{O of} 0.7 fL at the time of ejection has a spherical shape, the droplet diameter: D _O (diameter) corresponds to 1 μm. Under these coating conditions, the average diameter of dots drawn with one droplet of 0.7 fL of droplet volume at the time of ejection is 1 to 2 μm.

The shape of the coating film of the metal nanoparticle dispersion liquid for forming the source electrode 4 is a rectangle having a short side: L _S = 2 μm and a long side: W _S = 300 μm, and the thickness of the coating film: T _S-draw is 0. 3 μm is selected. Spacing and long sides of the rectangular pattern of the coating film, the side edge of the source electrode side of the gate electrode 3: [Delta] L _SG is selected [Delta] L _SG = 1 [mu] m.

The shape of the metal nanoparticle dispersion liquid coating film for forming the drain electrode 5 is a rectangle having a short side: L _D = 2 μm and a long side: W _D = 300 μm, and the thickness of the coating film: T _D-draw is 0. 3 μm is selected. The distance between the long side of the rectangular pattern of the coating film and the side edge of the gate electrode 3 on the drain electrode side: ΔL _DG is selected to be ΔL _DG = 1 μm.

  The metal nanoparticle dispersion coating film is subjected to a low-temperature baking treatment in a nitrogen gas stream at a temperature of 130 ° C. for 60 minutes to obtain a sintered layer of silver nanoparticles.

Separately, a rectangular silver nanoparticle sintered body layer having a width of 2 μm and a length of 300 μm is formed on the SAM film / AlO _x laminated film used for the gate insulating film under the same conditions. The average film thickness: T _baked is 0.3 μm. The resistivity of the silver nanoparticle sintered body layer was 25 μΩ · cm.

A sintered layer of silver nanoparticles obtained by a low-temperature firing treatment is used as the source electrode 4 and the drain electrode 5. Accordingly, the film thicknesses T _S and T _D of the source electrode 4 and the drain electrode 5 are estimated to be 0.3 μm on average. In addition, the line width disturbance (small irregularities): δL _S and δL _D at each side of the rectangular pattern of the silver nanoparticle sintered body layer is estimated to be 100 nm.

Distance between the produced source electrode 4 and drain electrode 5: L _SD was 2 μm. The design value of the length of the channel region: L _channel = 3 μm, but the difference (L _channel −L _SD ) was only 1 μm.

The formation of the gate insulating film 3 made of self-assembled monomolecular film (SAM film) / AlO _x is performed in the following steps. First, plasma oxidation is performed on the surface of the Al gate electrode 2 to form an AlO _x layer on the Al surface. Thereafter, when a water washing treatment is performed, Al—OH type hydroxy groups are present at a high density on the surface of the AlO _x layer. Thereafter, it is immersed in a monomolecular dispersion solution to form a monomolecular film on the surface of the AlO _x layer in a self-composing manner. The monomolecular dispersion solution is obtained by dispersing n-octadecylphosphonic acid (C ₁₈ H ₃₇ P (═O) (OH) ₂ ) in a dispersion solvent 2-propanol at a dispersion concentration of 1% by mass or more. After immersing in the monomolecular dispersion solution having a liquid temperature of 30 ° C. for 12 hours, the solution is taken out and the remaining dispersion is removed by nitrogen blowing. n- octadecyl phosphonic acid _{(C 18 H 37 P (=} O) (OH) 2) is reacted with Al-OH type hydroxy groups of the AlO _x layer surface, result in the formation of an ester bond, the AlO _x layer surface A self-assembled monolayer is formed.

Hexadecafluorocopper phthalocyanine is deposited on the surface of the gate insulating film 3 on which the “self-assembled monolayer” is formed on the surface of the AlO _x layer by vapor deposition. The thickness of the deposited hexadecafluorocopper phthalocyanine vapor deposition film: T _channel is selected to be 30 nm. As the deposition conditions for hexadecafluorocopper phthalocyanine, a deposition source temperature of 230 ° C. and a substrate temperature of 90 ° C. are selected for hexadecafluorocopper phthalocyanine. The film thickness of the deposited film: T _channel is separately prepared on the SAM film / AlO _x laminated film used for the gate insulating film under the same deposition conditions, and the deposition time and the deposited film thickness. It is an estimated value based on the result of measuring the correlation. At that time, the film thickness of the hexadecafluorocopper phthalocyanine deposited film can be measured by ellipsometry, assuming that the relative refractive index of the hexadecafluorocopper phthalocyanine deposited film is equal to the relative refractive index of the solid. .

Finally, the organic semiconductor layer 6 is patterned into a rectangular shape having a predetermined pattern shape, length: L _OS = 300 μm, and width: W _OS = 300 μm.

The threshold voltage: V _th of the manufactured organic thin film transistor was measured under the condition of the drain-source voltage V _SD = 3V. The threshold voltage of the organic thin film transistor was measured as V _th = 1.5V. Further, “ON state”: drain current I _d-ON when applying a gate voltage: V _G-ON = 3V, and “OFF state”: drain current I _d when applying a gate voltage: V _G-OFF = 0V. _-ON ratio, ON / OFF current ratio: I _d-ON / I _d-OFF was about 1 × 10 ⁴ .

(Example 3)
Example 3 is an example in which an organic thin film transistor using an organic semiconductor layer made of pentacene as an operating layer is manufactured by applying the method for manufacturing an organic thin film transistor according to the second aspect of the present invention.

  The organic thin film transistor fabricated in Example 3 has the following configuration.

  As the substrate 1, a polyethylene naphthalate (PEN) substrate having a thickness of 500 μm is used.

In the gate electrode 2, the shape of the channel region portion used for the switching operation of the TFT is rectangular. In the rectangular shape, the gate length: L _G is the 1 [mu] m, the gate width: W _G is selected 300 [mu] m. The metal species of the gate electrode 2 is Al, and a deposited film having a film thickness: T _gate = 20 nm is patterned into the shape pattern described above.

A gate insulating film 3 made of a self-assembled monolayer (SAM film) / AlO _x is formed so as to cover the gate electrode 2 and cover the entire surface of the substrate 1. At that time, the thickness of AlO _x layer immediately above the gate electrode 2: T _AlOx has a T _AlOx = 3.6 nm. In the region on the surface of the substrate 1, a self-assembled monomolecular film (SAM film) is formed on the AlO _x film, and the film thickness of the SAM film is 2.1 nm.

The formation of the gate insulating film 3 made of self-assembled monomolecular film (SAM film) / AlO _x is performed in the following steps. First, plasma oxidation is performed on the surface of the Al gate electrode 2 to form an AlO _x layer on the Al surface. Thereafter, when a water washing treatment is performed, Al—OH type hydroxy groups are present at a high density on the surface of the AlO _x layer. Thereafter, it is immersed in a monomolecular dispersion solution to form a monomolecular film on the surface of the AlO _x layer in a self-composing manner. The monomolecular dispersion solution is obtained by dispersing n-octadecylphosphonic acid (C ₁₈ H ₃₇ P (═O) (OH) ₂ ) in a dispersion solvent 2-propanol at a dispersion concentration of 1% by mass or more. After immersing in the monomolecular dispersion solution having a liquid temperature of 30 ° C. for 12 hours, the solution is taken out and the remaining dispersion is removed by nitrogen blowing. n- octadecyl phosphonic acid _{(C 18 H 37 P (=} O) (OH) 2) is reacted with Al-OH type hydroxy groups of the AlO _x layer surface, result in the formation of an ester bond, the AlO _x layer surface A self-assembled monolayer is formed.

Pentacene is deposited on the surface of the gate insulating film 3 on which the “self-assembled monolayer” is formed on the surface of the AlO _x layer by vapor deposition. The film thickness of the deposited pentacene vapor deposition film: T _channel is selected to be 30 nm. As the pentacene vapor deposition conditions, a pentacene vapor deposition source temperature of 230 ° C. and a substrate temperature of 60 ° C. are selected.

Thereafter, the organic semiconductor layer 6 is patterned into a rectangular shape having a predetermined pattern shape, length: L _OS = 300 μm, and width: W _OS = 300 μm.

  A coating film of a metal nanoparticle dispersion for forming the source electrode 4 and the drain electrode 5 is formed on the organic semiconductor film 6 at a position sandwiching the gate electrode 2. The metal nanoparticle dispersion is obtained by forming a coating molecular layer of dodecylamine (melting point: 28.3 ° C., boiling point: 248 ° C.) on the surface of silver nanoparticles having an average particle diameter D: 3 nm, and dispersing solvent N14 ( Tetradecane having a viscosity of 2.0 to 2.3 mPa · s (20 ° C.), a melting point of 5.86 ° C., a boiling point of 253.57 ° C., manufactured by Nikko Petrochemical Co., Ltd.). In the metal nanoparticle dispersion, 20 parts by mass of the coating molecule dodecylamine and 52 parts by mass of N14 as the dispersion solvent are contained per 100 parts by mass of the silver nanoparticles. The liquid viscosity of the silver nanoparticle dispersion is 10 mPa · s (20 ° C.).

Using silver nanoparticle dispersion of the bore diameter of the discharge hole of the ultra-fine inkjet device: Select D _open to 0.2 [mu] m, and set the droplet volume to be injected into 0.7FL, to form a coating film . Assuming that a droplet having a droplet volume V _{O of} 0.7 fL at the time of ejection has a spherical shape, the droplet diameter: D _O (diameter) corresponds to 1 μm. Under these coating conditions, the average diameter of dots drawn with one droplet of 0.7 fL of droplet volume at the time of ejection is 1 to 2 μm.

The shape of the coating film of the metal nanoparticle dispersion liquid for forming the source electrode 4 is a rectangle having a short side: L _S = 2 μm and a long side: W _S = 300 μm, and the thickness of the coating film: T _S-draw is 0. 3 μm is selected. Spacing and long sides of the rectangular pattern of the coating film, the side edge of the source electrode side of the gate electrode 3: [Delta] L _SG is selected [Delta] L _SG = 1 [mu] m.

The shape of the metal nanoparticle dispersion liquid coating film for forming the drain electrode 5 is a rectangle having a short side: L _D = 2 μm and a long side: W _D = 300 μm, and the thickness of the coating film: T _D-draw is 0. 3 μm is selected. The distance between the long side of the rectangular pattern of the coating film and the side edge of the gate electrode 3 on the drain electrode side: ΔL _DG is selected to be ΔL _DG = 1 μm.

  The metal nanoparticle dispersion coating film is subjected to a low-temperature baking treatment in a nitrogen gas stream at a temperature of 130 ° C. for 60 minutes to obtain a sintered layer of silver nanoparticles.

Separately, an average film thickness of a sintered body layer of silver nanoparticles having a width of 2 μm and a length of 300 μm produced on the same condition on an AlO _x film used as a gate insulating film. : T _baked is measured to be 0.3 μm. The resistivity of the silver nanoparticle sintered body layer was 25 μΩ · cm.

A sintered layer of silver nanoparticles obtained by a low-temperature firing treatment is used as the source electrode 4 and the drain electrode 5. Accordingly, the film thicknesses T _S and T _D of the source electrode 4 and the drain electrode 5 are estimated to be 0.3 μm on average. In addition, the line width disturbance (small irregularities): δL _S and δL _D at each side of the rectangular pattern of the silver nanoparticle sintered body layer is estimated to be 100 nm.

Distance between the produced source electrode 4 and drain electrode 5: L _SD was 2 μm. The design value of the length of the channel region: L _channel = 3 μm, but the difference (L _channel −L _SD ) was only 1 μm.

The threshold voltage: V _th of the produced organic thin film transistor was measured under the condition of drain-source voltage V _DS = −2.5V. The threshold voltage of the organic thin film transistor was measured as V _th = −0.5V. Further, “ON state”: drain voltage I _d-ON when applying a gate voltage: V _G-ON = −3.0 V, and “OFF state”: drain voltage when applying a gate voltage: V _G-OFF = 0V The ratio of current I _d-ON , ON / OFF current ratio: I _d-ON / I _d-OFF was about 1 × 10 ⁶ .

Example 4
Example 4 is an example in which an organic thin film transistor using an organic semiconductor layer made of hexadecafluorocopper phthalocyanine as an operation layer is manufactured by applying the method for manufacturing an organic thin film transistor according to the second aspect of the present invention.

  The organic thin film transistor fabricated in Example 4 has the following configuration.

  As the substrate 1, a polyethylene naphthalate (PEN) substrate having a thickness of 500 μm is used.

In the gate electrode 2, the shape of the channel region portion used for the switching operation of the TFT is rectangular. In the rectangular shape, the gate length: L _G is the 1 [mu] m, the gate width: W _G is selected 300 [mu] m. The metal species of the gate electrode 2 is Al, and a deposited film having a film thickness: T _gate = 20 nm is patterned into the shape pattern described above.

A gate insulating film 3 made of a self-assembled monolayer (SAM film) / AlO _x is formed so as to cover the gate electrode 2 and cover the entire surface of the substrate 1. At that time, the thickness of AlO _x layer immediately above the gate electrode 2: T _AlOx has a T _AlOx = 3.6 nm. In the region on the surface of the substrate 1, a self-assembled monomolecular film (SAM film) is formed on the AlO _x film, and the film thickness of the SAM film is 2.1 nm.

The formation of the gate insulating film 3 made of self-assembled monomolecular film (SAM film) / AlO _x is performed in the following steps. First, plasma oxidation is performed on the surface of the Al gate electrode 2 to form an AlO _x layer on the Al surface. Thereafter, when a water washing treatment is performed, Al—OH type hydroxy groups are present at a high density on the surface of the AlO _x layer. Thereafter, it is immersed in a monomolecular dispersion solution to form a monomolecular film on the surface of the AlO _x layer in a self-composing manner. The monomolecular dispersion solution is obtained by dispersing n-octadecylphosphonic acid (C ₁₈ H ₃₇ P (═O) (OH) ₂ ) in a dispersion solvent 2-propanol at a dispersion concentration of 1% by mass or more. After immersing in the monomolecular dispersion solution having a liquid temperature of 30 ° C. for 12 hours, the solution is taken out and the remaining dispersion is removed by nitrogen blowing. n- octadecyl phosphonic acid _{(C 18 H 37 P (=} O) (OH) 2) is reacted with Al-OH type hydroxy groups of the AlO _x layer surface, result in the formation of an ester bond, the AlO _x layer surface A self-assembled monolayer is formed.

Hexadecafluorocopper phthalocyanine is deposited on the surface of the gate insulating film 3 on which the “self-assembled monolayer” is formed on the surface of the AlO _x layer by vapor deposition. The thickness of the deposited hexadecafluorocopper phthalocyanine vapor deposition film: T _channel is selected to be 30 nm. As the deposition conditions for hexadecafluorocopper phthalocyanine, a deposition source temperature of 230 ° C. and a substrate temperature of 90 ° C. are selected.

Thereafter, the organic semiconductor layer 6 is patterned into a rectangular shape having a predetermined pattern shape, length: L _OS = 300 μm, and width: W _OS = 300 μm.

  A coating film of a metal nanoparticle dispersion for forming the source electrode 4 and the drain electrode 5 is formed on the organic semiconductor film 6 at a position sandwiching the gate electrode 2. The metal nanoparticle dispersion is obtained by forming a coating molecular layer of dodecylamine (melting point: 28.3 ° C., boiling point: 248 ° C.) on the surface of silver nanoparticles having an average particle diameter D: 3 nm, and dispersing solvent N14 ( Tetradecane having a viscosity of 2.0 to 2.3 mPa · s (20 ° C.), a melting point of 5.86 ° C., a boiling point of 253.57 ° C., manufactured by Nikko Petrochemical Co., Ltd.). In the metal nanoparticle dispersion, 20 parts by mass of the coating molecule dodecylamine and 52 parts by mass of N14 as the dispersion solvent are contained per 100 parts by mass of the silver nanoparticles. The liquid viscosity of the silver nanoparticle dispersion is 10 mPa · s (20 ° C.).

Using silver nanoparticle dispersion of the bore diameter of the discharge hole of the ultra-fine inkjet device: Select D _open to 0.2 [mu] m, and set the droplet volume to be injected into 0.7FL, to form a coating film . Assuming that a droplet having a droplet volume V _{O of} 0.7 fL at the time of ejection has a spherical shape, the droplet diameter: D _O (diameter) corresponds to 1 μm. Under these coating conditions, the average diameter of dots drawn with one droplet of 0.7 fL of droplet volume at the time of ejection is 1 to 2 μm.

The shape of the coating film of the metal nanoparticle dispersion liquid for forming the source electrode 4 is a rectangle having a short side: L _S = 2 μm and a long side: W _S = 300 μm, and the thickness of the coating film: T _S-draw is 0. 3 μm is selected. Spacing and long sides of the rectangular pattern of the coating film, the side edge of the source electrode side of the gate electrode 3: [Delta] L _SG is selected [Delta] L _SG = 1 [mu] m.

The shape of the metal nanoparticle dispersion liquid coating film for forming the drain electrode 5 is a rectangle having a short side: L _D = 2 μm and a long side: W _D = 300 μm, and the thickness of the coating film: T _D-draw is 0. 3 μm is selected. The distance between the long side of the rectangular pattern of the coating film and the side edge of the gate electrode 3 on the drain electrode side: ΔL _DG is selected to be ΔL _DG = 1 μm.

  The metal nanoparticle dispersion coating film is subjected to a low-temperature baking treatment in a nitrogen gas stream at a temperature of 130 ° C. for 60 minutes to obtain a sintered layer of silver nanoparticles.

Separately, in the sintered body layer of rectangular silver nanoparticles having a width of 2 mm and a length of 300 mm produced on the same conditions on the AlO _x film used for the gate insulating film, the average film thickness of the sintered body layer : T _baked is measured to be 0.3 μm. The resistivity of the silver nanoparticle sintered body layer was 25 μΩ · cm.

A sintered layer of silver nanoparticles obtained by a low-temperature firing treatment is used as the source electrode 4 and the drain electrode 5. Accordingly, the film thicknesses T _S and T _D of the source electrode 4 and the drain electrode 5 are estimated to be 0.3 μm on average. In addition, the line width disturbance (small irregularities): δL _S and δL _D at each side of the rectangular pattern of the silver nanoparticle sintered body layer is estimated to be 100 nm.

Distance between the produced source electrode 4 and drain electrode 5: L _SD was 2 μm. The design value of the length of the channel region: L _channel = 3 μm, but the difference (L _channel −L _SD ) was only 1 μm.

The threshold voltage: V _th of the manufactured organic thin film transistor was measured under the condition of drain-source voltage V _DS = 1.5V. The threshold voltage of the organic thin film transistor was measured as V _th = 1V. Further, “ON state”: drain current I _d-ON when applying a gate voltage: V _G-ON = 3V, and “OFF state”: drain current I _d when applying a gate voltage: V _G-OFF = 0V. _-ON ratio, ON / OFF current ratio: I _d-ON / I _d-OFF was about 1 × 10 ⁴ .

1A schematically shows the structure of an organic thin film transistor manufactured according to the manufacturing method described in Example 3 or Example 4. FIG. Also, the (b) of FIG. 1, on the pentacene film, the source electrode 4 and drain electrode 5 Interval: the L _SD, 1 [mu] m, 2 [mu] m, the manufacturing line width of the source electrode 4 and drain electrode 5 as 5μm Disturbance (small irregularities): δL _S and δL _D are image images obtained by microscopic observation. In addition, FIG. 1C shows a two-dimensional image in which the surface of the channel region including the source electrode 4 and the drain electrode 5 formed on the pentacene film is observed by AFM (Atomic Force Microscopy). Show the image. FIG. 1C shows that the cross-sectional shapes of the source electrode 4 and the drain electrode 5 actually show a convex shape schematically shown in FIG. That is, in the spot drawn using an ultrafine inkjet device, the applied silver nanoparticle dispersion liquid is in a state of high liquid viscosity, and flattening due to wetting and spreading between adjacent spots is suppressed. It is shown that.

  The organic thin film transistor manufacturing method of the present invention controls the display operation of each pixel in a flat panel display device such as a liquid crystal display manufactured on a substrate made of an insulating polymer material, for example, a plastic substrate. It is suitably used for manufacturing an organic thin film transistor for a switching element and a driving element for driving each pixel.

It is a figure which shows typically the structure of the organic thin-film transistor produced according to the manufacturing method described in Example 3 or Example 4.

Claims (17)

A method of manufacturing an organic thin film transistor, comprising:
Forming a gate electrode on the substrate;
Forming a gate insulating film covering the surface of the gate electrode on the substrate;
Forming a source electrode and a drain electrode on the gate insulating film;
Forming an organic semiconductor film on the gate insulating film so as to cover the source electrode and drain electrode surfaces;
The gate insulating film is composed of a base insulating film and a self-assembled monolayer formed on the surface of the base insulating film,
In the step of forming the organic semiconductor film,
Using the vacuum deposition method, the organic semiconductor film is formed,
The organic semiconductor film formed on the gate insulating film is formed using a vacuum deposition method with the self-assembled monomolecular film as a base layer,
In the step of forming the source electrode and the drain electrode,
Using an ultrafine inkjet printing apparatus, the metal nanoparticle dispersion is applied in a predetermined pattern shape to form a metal nanoparticle dispersion coating layer,
The metal nanoparticle dispersion coating layer is heated and fired to form a source electrode and a drain electrode composed of a sintered body layer of metal nanoparticles,
The ultra-fine inkjet printing apparatus is
An electrostatic suction type ultra-fine inkjet printing device,
From the opening of the nozzle tip formed of an insulator, micro droplets are discharged,
The opening diameter (diameter) of the nozzle tip; D _open is selected in the range of 0.1 μm to 1 μm,
The metal nanoparticle dispersion, which is discharged using the ultrafine inkjet printing apparatus,
As a solid component, a dispersion obtained by uniformly dispersing the metal nanoparticles in a dispersion solvent,
The surface of the metal nanoparticle contains a nitrogen, oxygen, or sulfur atom as a group capable of coordinative bonding with the metal element contained in the metal nanoparticle, and is coordinated by a lone electron pair possessed by these atoms. Covered with one or more organic compounds having a group capable of bonding;
The total of one or more organic compounds having a group containing nitrogen, oxygen, or sulfur atoms with respect to 100 parts by mass of the metal nanoparticles, containing 10 to 50 parts by mass,
The minimum line width of the metal nanoparticle dispersion liquid coating layer formed using the ultrafine inkjet printing apparatus is selected in the range of 1 μm to 10 μm,
The coating thickness of the metal nanoparticle dispersion coating layer is selected in the range of 30 nm to 600 nm ,
And the side edge of the gate electrode side of the source electrode, the gap between the side edge of the gate electrode: [Delta] L _SG and the side edge of the gate electrode side of the drain electrode, the gap between the side edge of the gate electrode: [Delta] L _DG is Each satisfies at least ΔL _SG > 0 μm, ΔL _DG > 0 μm,
Gate length of the gate electrode: the basis of the L _G, the gate electrode of the source electrode and the drain electrode interval: L _SD is selected in the range of _{2L G ≧ L SD> L G} ,
Side edges of the source electrode and drain electrode on the gate electrode side have a shape having inclined side surfaces,
The average inclination angles of the side surfaces having the inclination (taper): [theta] _s , [theta] _D are selected in the range of 70 [deg.]> [Theta] _s > 45 [deg.] And 70 [deg.]> [Theta] _D > 45 [deg.]. A method for manufacturing an organic thin film transistor. A method of manufacturing an organic thin film transistor, comprising:
Forming a gate electrode on the substrate;
Forming a gate insulating film covering the surface of the gate electrode on the substrate;
Forming an organic semiconductor film on the gate insulating film;
Forming a source electrode and a drain electrode on the organic semiconductor film;
The gate insulating film is composed of a base insulating film and a self-assembled monolayer formed on the surface of the base insulating film,
In the step of forming the organic semiconductor film,
Using the self-assembled monolayer as an underlayer,
Using the vacuum deposition method, the organic semiconductor film is formed,
In the step of forming the source electrode and the drain electrode,
Using an ultrafine inkjet printing apparatus, the metal nanoparticle dispersion is applied in a predetermined pattern shape to form a metal nanoparticle dispersion coating layer,
The metal nanoparticle dispersion coating layer is heated and fired to form a source electrode and a drain electrode composed of a sintered body layer of metal nanoparticles,
The ultra-fine inkjet printing apparatus is
An electrostatic suction type ultra-fine inkjet printing device,
From the opening of the nozzle tip formed of an insulator, micro droplets are discharged,
The opening diameter (diameter) of the nozzle tip; D _open is selected in the range of 0.1 μm to 1 μm,
The metal nanoparticle dispersion, which is discharged using the ultrafine inkjet printing apparatus,
As a solid component, a dispersion obtained by uniformly dispersing the metal nanoparticles in a dispersion solvent,
The surface of the metal nanoparticle contains a nitrogen, oxygen, or sulfur atom as a group capable of coordinative bonding with the metal element contained in the metal nanoparticle, and is coordinated by a lone electron pair possessed by these atoms. Covered with one or more organic compounds having a group capable of bonding;
The total of one or more organic compounds having a group containing nitrogen, oxygen, or sulfur atoms with respect to 100 parts by mass of the metal nanoparticles, containing 10 to 50 parts by mass,
The minimum line width of the metal nanoparticle dispersion liquid coating layer formed using the ultrafine inkjet printing apparatus is selected in the range of 1 μm to 10 μm,
The coating thickness of the metal nanoparticle dispersion coating layer is selected in the range of 30 nm to 600 nm ,
And the side edge of the gate electrode side of the source electrode, the gap between the side edge of the gate electrode: [Delta] L _SG and the side edge of the gate electrode side of the drain electrode, the gap between the side edge of the gate electrode: [Delta] L _DG is Each satisfies at least ΔL _SG > 0 μm, ΔL _DG > 0 μm,
Gate length of the gate electrode: the basis of the L _G, the gate electrode of the source electrode and the drain electrode interval: L _SD is selected in the range of _{2L G ≧ L SD> L G} ,
Side edges of the source electrode and drain electrode on the gate electrode side have a shape having inclined side surfaces,
The average inclination angles of the side surfaces having the inclination (taper): [theta] _s , [theta] _D are selected in the range of 70 [deg.]> [Theta] _s > 45 [deg.] And 70 [deg.]> [Theta] _D > 45 [deg.]. A method for manufacturing an organic thin film transistor. In the application of the metal nanoparticle dispersion using the ultrafine inkjet printing apparatus,
The method for producing an organic thin film transistor according to claim 1, wherein the amount of liquid droplets to be ejected is selected in the range of 0.3 femtoliter to 1 femtoliter. In the application of the metal nanoparticle dispersion using the ultrafine inkjet printing apparatus,
The method for producing an organic thin film transistor according to claim 2, wherein the amount of liquid droplets to be discharged is selected in the range of 0.3 femtoliter to 1 femtoliter. The average particle diameter of the metal nanoparticles dispersed in the metal nanoparticle dispersion is selected in the range of 1 to 20 nm ,
The metal nanoparticle dispersion is
The total amount of one or more organic compounds having a group containing nitrogen, oxygen or sulfur atoms is 20 to 50 parts by mass with respect to 100 parts by mass of the metal nanoparticles. The manufacturing method of the organic thin-film transistor as described in any one of Claims 1-4. The metal nanoparticles dispersed in the metal nanoparticle dispersion are:
Selected from the group of metals consisting of gold, silver, copper, platinum, palladium , selected from the group consisting of one type of metal, a mixture of two or more types of nanoparticles, or the group of the metal The method for producing an organic thin film transistor according to any one of claims 1 to 5, wherein the organic thin film transistor is a nanoparticle made of an alloy of two or more kinds of metals. The liquid viscosity at 20 ° C. of the metal nanoparticle dispersion discharged using the ultrafine inkjet printing apparatus is selected in the range of 2 mPa · s to 30 mPa · s. The manufacturing method of the organic thin-film transistor as described in any one. The method for producing an organic thin film transistor according to any one of claims 1 to 7, wherein at least one organic compound having a group containing nitrogen, oxygen, or sulfur atoms is an alkylamine. The metal nanoparticle dispersion, which is discharged using the ultrafine inkjet printing apparatus,
As a dispersion solvent, containing one or more liquid organic substances or organic solvents,
The organic solvent having a melting point of 20 ° C. or lower and a boiling point of 80 to 300 ° C. is selected as at least one of the liquid organic substance or organic solvent. A method for producing an organic thin film transistor according to claim 1. The method for producing an organic thin film transistor according to claim 9, wherein an alkane having 10 to 18 carbon atoms or a primary alcohol having 8 to 12 carbon atoms is selected as a dispersion solvent. The dispersion solvent is
High solubility capable of dissolving 50 parts by mass or more of the organic compound having a group containing nitrogen, oxygen, or sulfur atoms covering the surface of the metal nanoparticles per 100 parts by mass of the dispersion solvent when heated to 100 ° C. or higher. The organic thin-film transistor manufacturing method according to claim 1, wherein the organic thin-film transistor is a solvent composed of one kind of organic solvent or liquid organic substance or a mixed solvent composed of two or more kinds. The metal nanoparticle dispersion, which is discharged using the ultrafine inkjet printing apparatus,
A concentrated dispersion obtained by partially evaporating and removing the dispersion solvent contained in the dispersion and concentrating until the volume ratio of the dispersion solvent is in the range of 20 to 50% by volume has a liquid viscosity at 20 ° C. The method for producing an organic thin film transistor according to any one of claims 1 to 11, wherein the concentrate becomes a viscous concentrated liquid in a range of 20 Pa · s to 1000 Pa · s. When the metal nanoparticle dispersion coating layer is heated and fired,
The method for producing an organic thin film transistor according to any one of claims 1 to 12, wherein the baking temperature is selected in a range of 130C to 200C . The organic semiconductor layer is
It is a layer which consists of pentacene or hexadecafluoro copper phthalocyanine, The manufacturing method of the organic thin-film transistor as described in any one of Claims 1-13 characterized by the above-mentioned. A hydroxy group (-OH) exists on the surface of the base insulating film,
The self-assembled monolayer formed on the surface of the base insulating film is
A monomolecular film grows in a lateral direction in a self-organized manner with a monomolecular organic phosphonic acid adsorbed on the surface of the base insulating film having a hydroxy group (—OH) as a nucleus, and finally The method for producing an organic thin film transistor according to claim 1, wherein the organic thin film transistor has a regular molecular orientation. A method of manufacturing an organic thin film transistor, comprising:
Forming a gate electrode on the substrate;
Forming a gate insulating film covering the surface of the gate electrode on the substrate;
Forming a source electrode and a drain electrode on the gate insulating film;
Forming an organic semiconductor film on the gate insulating film so as to cover the source electrode and drain electrode surfaces;
The gate insulating film is composed of a base insulating film and a self-assembled monolayer formed on the surface of the base insulating film,
In the step of forming the organic semiconductor film,
Using the vacuum deposition method, the organic semiconductor film is formed,
The organic semiconductor film formed on the gate insulating film is formed using a vacuum deposition method with the self-assembled monomolecular film as a base layer,
In the step of forming the source electrode and the drain electrode,
Using an ultrafine inkjet printing apparatus, the metal nanoparticle dispersion is applied in a predetermined pattern shape to form a metal nanoparticle dispersion coating layer,
The metal nanoparticle dispersion coating layer is heated and fired to form a source electrode and a drain electrode composed of a sintered body layer of metal nanoparticles,
The ultra-fine inkjet printing apparatus is
An electrostatic suction type ultra-fine inkjet printing device,
From the opening of the nozzle tip formed of an insulator, micro droplets are discharged,
The metal nanoparticle dispersion, which is discharged using the ultrafine inkjet printing apparatus,
As a solid component, a dispersion obtained by uniformly dispersing the metal nanoparticles in a dispersion solvent,
The surface of the metal nanoparticle contains a nitrogen, oxygen, or sulfur atom as a group capable of coordinative bonding with the metal element contained in the metal nanoparticle, and is coordinated by a lone electron pair possessed by these atoms. Covered with one or more organic compounds having a group capable of bonding;
The total of one or more organic compounds having a group containing nitrogen, oxygen, or sulfur atoms with respect to 100 parts by mass of the metal nanoparticles, containing 10 to 50 parts by mass,
The minimum line width of the metal nanoparticle dispersion liquid coating layer formed using the ultrafine inkjet printing apparatus is selected in the range of 1 μm to 10 μm,
The coating thickness of the metal nanoparticle dispersion coating layer is selected in the range of 30 nm to 600 nm,
And the side edge of the gate electrode side of the source electrode, the gap between the side edge of the gate electrode: [Delta] L _SG and the side edge of the gate electrode side of the drain electrode, the gap between the side edge of the gate electrode: [Delta] L _DG is Each satisfies at least ΔL _SG > 0 μm, ΔL _DG > 0 μm,
Gate length of the gate electrode: the basis of the L _G, the gate electrode of the source electrode and the drain electrode interval: L _SD is selected in the range of _{2L G ≧ L SD> L G} ,
A method of manufacturing an organic thin film transistor, wherein side edges of the source electrode and the drain electrode on the gate electrode side have a side surface having an inclination. A method of manufacturing an organic thin film transistor, comprising:
Forming a gate electrode on the substrate;
Forming a gate insulating film covering the surface of the gate electrode on the substrate;
Forming an organic semiconductor film on the gate insulating film;
Forming a source electrode and a drain electrode on the organic semiconductor film;
The gate insulating film is composed of a base insulating film and a self-assembled monolayer formed on the surface of the base insulating film,
In the step of forming the organic semiconductor film,
Using the self-assembled monolayer as an underlayer,
Using the vacuum deposition method, the organic semiconductor film is formed,
In the step of forming the source electrode and the drain electrode,
Using an ultrafine inkjet printing apparatus, the metal nanoparticle dispersion is applied in a predetermined pattern shape to form a metal nanoparticle dispersion coating layer,
The metal nanoparticle dispersion coating layer is heated and fired to form a source electrode and a drain electrode composed of a sintered body layer of metal nanoparticles,
The ultra-fine inkjet printing apparatus is
An electrostatic suction type ultra-fine inkjet printing device,
From the opening of the nozzle tip formed of an insulator, micro droplets are discharged,
The metal nanoparticle dispersion, which is discharged using the ultrafine inkjet printing apparatus,
As a solid component, a dispersion obtained by uniformly dispersing the metal nanoparticles in a dispersion solvent,
The surface of the metal nanoparticle contains a nitrogen, oxygen, or sulfur atom as a group capable of coordinative bonding with the metal element contained in the metal nanoparticle, and is coordinated by a lone electron pair possessed by these atoms. Covered with one or more organic compounds having a group capable of bonding;
The total of one or more organic compounds having a group containing nitrogen, oxygen, or sulfur atoms with respect to 100 parts by mass of the metal nanoparticles, containing 10 to 50 parts by mass,
The minimum line width of the metal nanoparticle dispersion liquid coating layer formed using the ultrafine inkjet printing apparatus is selected in the range of 1 μm to 10 μm,
The coating thickness of the metal nanoparticle dispersion coating layer is selected in the range of 30 nm to 600 nm,
And the side edge of the gate electrode side of the source electrode, the gap between the side edge of the gate electrode: [Delta] L _SG and the side edge of the gate electrode side of the drain electrode, the gap between the side edge of the gate electrode: [Delta] L _DG is Each satisfies at least ΔL _SG > 0 μm, ΔL _DG > 0 μm,
Gate length of the gate electrode: the basis of the L _G, the gate electrode of the source electrode and the drain electrode interval: L _SD is selected in the range of _{2L G ≧ L SD> L G} ,
A method of manufacturing an organic thin film transistor, wherein side edges of the source electrode and the drain electrode on the gate electrode side have a side surface having an inclination.