JP4934972B2 - Field effect transistor - Google Patents

Description

The present invention relates to a field effect transistor, and more particularly to a field effect transistor in which a gate insulating layer is a gate insulating layer containing a polymer having a specific water absorption amount.

In a field effect transistor having a gate insulating layer, a gate electrode and a semiconductor layer separated by the gate insulating layer, and a source electrode and a drain electrode provided in contact with the semiconductor layer on a supporting substrate, the semiconductor layer Or, as a gate insulating layer, an organic material capable of forming a layer by a formation method by application of a solution compared to a conventional formation method by vapor deposition using an inorganic material such as silicon, In addition to superiority, it has been attracting attention because it can be reduced in weight by using a polymer or the like, and can be given impact resistance. However, in the layer formation by application of a solution, the solvent resistance of the lower layer at the time of forming the upper layer is required, and selection of the material for that is important.

Polyimide has been proposed as an organic material having excellent solvent resistance. For example, Non-Patent Document 1 shows an example in which a gate insulating layer is formed by applying and drying a polyimide solution. However, according to the study by the present inventors, the polyimide described therein has poor water absorption resistance, and as a gate insulating layer of a field effect transistor, it cannot achieve both field effect mobility and On / Off ratio, Further, a decrease with time was observed, and it was found that improvement in these aspects was required.
Chem. Mater. , Vol. 9, no. 6,1299-1301 (1997)

The present invention has been made in view of the above-described prior art. Therefore, the present invention can form a layer by solution coating, and can provide field effect mobility and On / Off as a field effect transistor. An object of the present invention is to provide a field effect transistor having a gate insulating layer that can achieve both of the above ratios.

As a result of various studies to solve the above-mentioned problems, the present inventors have made the above object by adding a polymer having a specific water absorption amount to the gate insulating layer when a specific organic semiconductor layer is used. As a result, the present invention has been achieved. Accordingly, the present invention provides a gate insulating layer, a gate electrode and an organic semiconductor layer separated by the gate insulating layer, and an organic semiconductor layer on the supporting substrate. A field effect transistor having a source electrode and a drain electrode provided in contact with each other, wherein the gate insulating layer is formed by applying, drying , and heat-treating a polyimide precursor solution having any one of the structural repeating units shown below. And a gate insulating layer containing a fluorine atom-containing polyimide having a water absorption of 0.65 mg / cm ³ or less, wherein the organic semiconductor layer is tetrabenzoporphine. The gist of the present invention is a field effect transistor, characterized in that it is ilin or a metal salt thereof.

According to the present invention, there is provided a field effect transistor having a gate insulating layer capable of forming a layer by application of a solution and having both field effect mobility and On / Off ratio as a field effect transistor. be able to.

The field effect transistor of the present invention will be described with reference to the drawings. FIGS. 1 to 3 are longitudinal sectional views showing one embodiment of the field effect transistor of the present invention. The effect transistor includes a gate insulating layer 3, a gate electrode 2 and an organic semiconductor layer 4 separated by the gate insulating layer 3, a source electrode 5 provided in contact with the organic semiconductor layer 4, The drain electrode 6 is included, and its structure is not particularly limited. Typically, the bottom gate / bottom contact type shown in FIG. 1, the bottom gate / top contact type shown in FIG. Examples include the top gate / bottom contact type shown.

<Gate insulation layer>
In a field effect transistor, a gate insulating layer has a function of maintaining an overlapping region of a source electrode, a drain electrode, and a gate electrode, and a channel region on the gate electrode as an electrically insulating region. Here, “electrical insulation” means that the electric conductivity is 10 ⁻⁹ S / cm or less.

In the present invention, it is essential that the gate insulating layer is a gate insulating layer formed by application and drying of a solution and containing a polymer having a water absorption amount of 0.65 mg / cm ³ or less. preferably it has an amount of 0.60 mg / cm ³ or less, more preferably from 0.55 mg / cm ³ or less. Particularly preferred is 0.50 mg / cm ³ or less, and most preferred is 0.45 mg / cm ³ or less. If the amount of water absorption exceeds the above range, the field effect mobility as the field effect transistor and the On / Off ratio cannot be compatible. Here, the amount of water absorption is measured by the Karl Fischer method for a thin film formed by applying and drying a polymer solution.

In the present invention, the polymer is preferably polyimide. Polyimide is obtained by polymerizing polyamic acid, which is a precursor of polyimide, by ring-opening polyaddition reaction of tetracarboxylic dianhydride and diamine, and further dehydrating and cyclizing. In the present invention, Any of an aliphatic polyimide in which both tetracarboxylic dianhydride and diamine are aliphatic compounds and an aromatic polyimide in which both of the tetracarboxylic dianhydride and diamine are aromatic compounds are used. For example, the former aliphatic polyimide is suitable when the insulating layer is a thin film having a thickness of about 10 to 200 nm and a high dielectric constant is not required, and the latter aromatic polyimide is a film having an insulating layer thicker than 200 nm and has a high dielectric constant. Suitable when required. Further, a fluorine atom-containing polyimide in which the tetracarboxylic dianhydride or / and diamine contains a fluorine atom is preferable.

  In the fluorine atom-containing polyimide, the fluorine atom content is preferably 5% by weight or more, and more preferably 10% by weight or more based on the total amount of the polyimide. Here, the fluorine atom content means that the constitutional repeating unit containing a fluorine atom naturally includes a constitutional repeating unit not containing a fluorine atom in the case of containing a polyimide not containing a fluorine atom by copolymerization or mixing. Let's say the average value of all the quantities. The structural repeating unit preferably has no polar group such as a hydroxyl group, an amino group, a carbamoyl group, a sulfo group, a sulfamoyl group, and a group capable of producing active hydrogen, proton free hydrogen, etc. Even if it is, it is preferable that it is 1 or less as an average number per structural repeating unit. When the polymer contained in the gate insulating layer has a polar group, it tends to cause moisture adhesion in the layer and on the surface of the layer. For example, in a π-conjugated organic semiconductor material such as polythiophene described later, As a result, doping occurs and the off-current tends to increase.

  Specific examples of the constitutional repeating unit of the fluorine atom-containing polyimide that is preferably used in the present invention are shown below.

  In the above specific examples, “R” represents, for example, the following structure and the like, and “n” is an integer of 1 to 25.

  Moreover, as a polymer in this invention, it is preferable that a glass transition point is 80 degreeC or more, and it is still more preferable that it is 100 degreeC or more. If the glass transition point is lower than the above range, the fluidity is too high, and softening during the lamination of other layers or heating to easily cause non-uniform film thickness or surface irregularities as a gate insulating layer. It tends to be difficult to maintain the stratum. In addition, it is desirable to have a solvent resistance that is soluble in a solvent that does not dissolve a lower layer when forming a gate insulating layer such as a support substrate, which will be described later, and that is not eroded by a solvent when forming an upper layer such as an organic semiconductor layer.

In the present invention, the gate insulating layer containing the polymer is related to the leakage current to the gate electrode and the low gate voltage driving of the field effect transistor, so that the electrical conductivity at room temperature is 10 ⁻⁹ S / s. It is preferably cm or less, more preferably 10 ⁻¹⁴ S / cm or less, and the relative dielectric constant is preferably 2.0 or more, more preferably 2.5 or more.

  In the present invention, the gate insulating layer is formed by, for example, solution processing using a known method such as spin coating, solution casting, stamp printing, screen printing, or jet printing, followed by drying.

  The thickness of the gate insulating layer is preferably 4 μm or less, more preferably 2 μm or less, and particularly preferably 1 μm or less. Further, it is preferably 0.01 μm or more, more preferably 0.1 μm or more, and particularly preferably 0.2 μm or more.

<Support substrate>
In the field effect transistor of the present invention, the constituent material itself other than the gate insulating layer is not particularly limited, and those used in conventional field effect transistors can be used.

As a material for the support substrate in the present invention, any material can be used as long as it can support a field-effect transistor and a display element, a display panel, and the like formed thereon, known inorganic substrates such as glass and polysiloxane, and various organic polymers. Organic substrates such as polyester, polycarbonate, polyimide, polyamide, polyether sulfone, epoxy resin, polybenzoxazole, polybenzothiazole, polyparabanic acid, polysilsesquioxane, and vinyl polymers such as polyolefin, etc. Organic polymers are preferred. Among them, polyesters such as polyethylene terephthalate, polycarbonate, polyimide, polyamide, polybenzoxazole, polybenzothiazole, polyparabanic acid and other condensed polymers, and crosslinked products such as polyvinylphenol are preferable from the viewpoint of heat resistance and solvent resistance, Polyester, polycarbonate, polyimide, and polybenzoxazole are more preferable, and polyester such as polyethylene terephthalate or polyimide is particularly preferable. In addition, as a material of a support substrate, the blend of these polymers may be sufficient, and a filler, an additive, etc. may be included as needed.

Moreover, as a material of a support substrate, it is preferable that a glass transition point is 40 degreeC or more. When the glass transition point is lower than 40 ° C., the fluidity is too high, and it tends to be difficult to maintain the substrate by being softened when other layers are laminated or heated. The linear expansion coefficient is preferably 25 × 10 ⁻⁵ cm / cm · ° C. or lower, more preferably 10 × 10 ⁻⁵ cm / cm · ° C. or lower. If the linear expansion coefficient is greater than 25 × 10 ⁻⁵ cm / cm · ° C., dimensional changes are likely to occur during heat treatment during the production of the support substrate, and the transistor performance tends to be unstable as a field effect transistor. In addition, those exhibiting solvent resistance with respect to the solvent used in the production of the field effect transistor are preferable, and those having high adhesion to the gate insulating layer and the electrode are preferable.

The thickness of the support substrate is preferably 10 mm or less, more preferably 2 mm or less, and particularly preferably 1 mm or less. Moreover, it is preferable that it is 0.01 mm or more, and it is still more preferable that it is 0.05 mm or more. For example, in the case of an organic polymer substrate, the thickness is preferably about 0.05 to 0.1 mm, and in the case of a substrate such as glass or silicon, the thickness is preferably about 0.1 to 10 mm.

<Organic semiconductor layer>
As the organic semiconductor constituting the organic semiconductor layer in the present invention, any known one can be used as long as it is a π-conjugated low-molecular or high-molecular compound, such as soluble pentacene, a substituted oligothiophene having a substituent. Bisdithienothiophene, dialkylanthradithiophene having a substituent, soluble fullerene, π-conjugated small molecules such as macrocyclic compounds such as phthalocyanine and porphyrin, and regioregular poly (3-hexylthiophene) And π-conjugated polymers such as π-conjugated copolymers such as regioregular poly (3-alkylthiophene) and poly-9,9′-dialkylfluorenecobithiophene. Examples of macrocyclic compounds include copper phthalocyanine, perfluoro copper phthalocyanine, tetrabenzoporphyrin, and metal salts thereof.

Among these π-conjugated low molecules and polymers, those having an electric conductivity in the source electrode-drain electrode direction of 10 ⁻⁴ S / cm or less and 10 ⁻¹² S / cm or more as the organic semiconductor layer are preferable, What shows 10 < ^-6 > S / cm or less, 10 < ^-11 > S / cm or more is still more preferable, What shows 10 < ^-7 > S / cm or less, 10 < ^-10 > S / cm or more is especially preferable. Among these π-conjugated low molecules and polymers, the carrier density obtained from the field effect mobility, the electric conductivity in the direction of the source electrode and the drain electrode, and the elementary charge is 10 ⁷ / cm as the organic semiconductor layer. Those showing ³ or more and 10 ¹⁸ / cm ³ or less are preferred, and those showing 10 ⁸ / cm ³ or more and 10 ¹⁷ / cm ³ or less are more preferred. Among these π-conjugated low molecular weight and high molecular weight polymers, the activation energy required for charge transfer, which is obtained from the temperature dependence of the field effect mobility at room temperature or lower, as an organic semiconductor layer is 0.2 eV or lower. And those showing 0.1 eV or less are more preferred.

  The organic semiconductor layer in the present invention is formed, for example, by subjecting it to solution treatment and drying by a known method such as spin coating, stamp printing, screen printing, or jet printing.

Further, the film thickness of the organic semiconductor layer is preferably 1 nm or more, and more preferably 10 nm or more. Further, it is preferably 10 μm or less, more preferably 1 μm or less, and particularly preferably 500 nm or less.

<Gate electrode, source electrode, drain electrode>
As a constituent material of the gate electrode, the source electrode, and the drain electrode in the present invention, any material may be used as long as it exhibits conductivity, and any known material can be used, for example, platinum, gold, aluminum, chromium, nickel, Metals such as copper, titanium, magnesium, calcium, barium and sodium, conductive metal oxides such as InO ₂ , SnO ₂ and ITO, polyaniline doped with camphor sulfonic acid, polyethylene dioxy doped with paratoluene sulfonic acid Examples thereof include a conductive composite material in which a doped conductive polymer such as thiophene, carbon black, graphite powder, metal fine particles, and the like are dispersed in a binder.

  The gate electrode, the source electrode, and the drain electrode in the present invention are formed by, for example, a vacuum deposition method, a sputtering method, a coating method, a printing method, a sol-gel method, and the patterning method is, for example, photoresist patterning. And photolithographic methods that combine etching with etchant and reactive plasma, printing methods such as inkjet printing, screen printing, offset printing, letterpress printing, soft lithography methods such as microcontact printing methods, and these methods A method combining a plurality of methods may be used. It is also possible to directly form a pattern by irradiating an energy beam such as a laser or an electron beam to remove the material or changing the conductivity of the material.

The thickness of these gate electrode, source electrode, and drain electrode is preferably 0.01 μm or more, and more preferably 0.02 μm or more. Moreover, it is preferable that it is 2 micrometers or less, and it is still more preferable that it is 1 micrometer or less.

  The source electrode and drain electrode have a source electrode-drain electrode distance (channel length L) of usually 100 μm or less, preferably 50 μm or less, and a channel width W of usually 2,000 μm or less, preferably 500 μm or less. / W is usually 0.1 or less, preferably 0.05 or less.

<Other layers>
The basic structure of the field effect transistor of the present invention includes the gate insulating layer, the gate electrode and the organic semiconductor layer separated by the gate insulating layer, and the organic semiconductor layer on the support substrate. The source electrode and the drain electrode provided in contact with each other, and typical examples of the structure include those shown in FIGS. 1 to 3, and the field effect transistor of the present invention is shown in FIG. It is not limited to the field effect transistor having the structure shown in -3, and a layer other than the above layers may be further formed.

  For example, in a field effect transistor exposed by an organic semiconductor layer, such as the field effect transistor shown in FIGS. 1 and 2, in order to minimize the influence of outside air on the organic semiconductor layer, Further, a protective layer may be formed. In this case, the protective layer material is an organic polymer such as epoxy resin, acrylic resin, polyurethane, polyimide, polyvinyl alcohol, or oxide such as silicon oxide, silicon nitride, or aluminum oxide. And inorganic materials such as nitrides. In addition, as a formation method of a protective layer, the apply | coating method, a vacuum evaporation method, etc. are mentioned.

<Field effect transistor>
The field effect transistor of the present invention preferably has a field effect mobility of 10 ⁻³ cm ² / Vs or more, and more preferably 10 ⁻² cm ² / Vs or more. The On / Off ratio depends on the application, but generally it is preferably 10 ² or more, more preferably 10 ³ or more, and particularly preferably 10 ⁴ or more.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

Example 1
A heat-resistant glass plate (manufactured by Furuuchi Chemical Co., Ltd., 2.5 cm × 2.5 cm) is used as a support substrate, and this is covered with a shadow mask having a width of 1.2 mm, and then a vacuum vapor deposition machine (“EX-400” manufactured by ULVAC) The gate electrode was formed by evaporating aluminum with a thickness of 1,000 liters with a vacuum of 10 ⁻⁶ Torr. On top of this, 2 ml of the following polyimide precursor solution (fluorine atom content 30% by weight as polyimide) dissolved in N-methylpyrrolidone at a concentration of 5% by weight and filtered through a 0.2 μm filter was developed. After spin coating at 1,000 rpm for 120 seconds and drying, heat treatment was performed at 150 ° C. for 10 minutes, 200 ° C. for 2 hours, and 300 ° C. for 6 hours to form a gate insulating layer made of polyimide. The film thickness measured with a film thickness meter (“Alpha-Step 500” manufactured by Tencor) was 8,000 mm.

  Next, a 0.7 wt% chloroform solution prepared by dissolving tetrabicycloporphyrin represented by the following structural formula in chloroform at room temperature in a nitrogen atmosphere on this gate insulating layer was spin-coated at 1,000 rpm and dried. After forming the layer, heat treatment is performed at 210 ° C. for 5 minutes to convert it into a semiconductor layer to form an organic semiconductor layer, and subsequently, a channel for forming a source electrode and a drain electrode on the organic semiconductor layer. The film was covered with a shadow mask (L: 1,000 μm, W: 25 μm), and gold was deposited in a thickness of 1,000 mm to produce a field effect transistor having the structure shown in FIG.

With respect to the obtained field effect transistor, the field effect mobility and the On / Off ratio were calculated by the following method. As a result, 4.0 × 10 ⁻² cm ² / Vs and 1.8 × 10 ^{3 were obtained.} Met.

<Field effect mobility, On / Off ratio>
Using a semiconductor parameter analyzer (“4155” manufactured by Agilent), a voltage-current curve when a gate voltage was applied was obtained (FIG. 4) and calculated.

In addition, about the gate insulating layer obtained here, when the amount of water absorption was measured by the method shown below, it was 0.42 mg / cm < ³ >.

<Water absorption>
The heat-resistant glass plate is divided into two equal parts, and 2 ml of the polyimide precursor solution dissolved in dehydrated chloroform at a concentration of 10% by weight and filtered through a 0.2 μm filter is spin-coated at 500 rpm for 120 seconds, After drying, heat treatment was performed in the same manner as described above to form an insulating layer having a thickness of 10 μm, and the water absorption of the insulating layer was measured by the Karl Fischer method with the remaining half of the glass plate as a reference.

Comparative Example 1
Field effect transistor in the same manner as in Example 1, except that the polyimide precursor in Example 1 was changed to a polyimide precursor (“Optomer AL3046” manufactured by JSR Corporation, fluorine atom content of 0% by weight as polyimide) Was made. The film thickness of the gate insulating layer was 9,000 mm. With respect to the obtained field effect transistor, a voltage-current curve at the time of applying a gate voltage was obtained in the same manner as described above (FIG. 5), and the field effect mobility and On / Off ratio were calculated. 0 × 10 ⁻³ cm ² / Vs, and 5.5 × 10 ² . Further, the water absorption of the gate insulating layer obtained here was measured by the same method as described above, and it was 8.5 mg / cm ³ .

Comparative Example 2
A field effect transistor was produced in the same manner as in Example 1 except that the polyimide precursor was changed to the polyimide precursor shown below (fluorine atom content: 0% by weight as polyimide) in Example 1. The film thickness of the gate insulating layer was 9,000 mm. With respect to the obtained field effect transistor, a voltage-current curve when a gate voltage was applied was obtained in the same manner as described above (FIG. 6), and field effect mobility and On / Off ratio were calculated. 0 × 10 ⁻² cm ² / Vs and 7.5 × 10 ² . Further, the water absorption of the gate insulating layer obtained here was measured by the same method as described above, and it was 0.67 mg / cm ³ .

Reference example 1
In Example 1, a chloroform solution of Tetorabishikuropo Le Firin, regioregular poly (3-hexylthiophene-2,5-diyl) (Aldrich Corp., weight average molecular weight 87,000) was dissolved to be 15 mg / ml A field effect transistor was produced in the same manner as in Example 1 except that the organic solvent layer was changed to the adjusted chloroform solution. With respect to the obtained field effect transistor, a voltage-current curve when a gate voltage was applied was obtained (FIG. 7), and field effect mobility and On / Off ratio were calculated. As a result, 1.1 × 10 ⁻² cm ² respectively. / Vs, and 6.3 × 10 ³ .

Comparative Example 3
In Comparative Example 1, a chloroform solution of Tetorabishikuropo Le Firin, regioregular poly (3-hexylthiophene-2,5-diyl) (Aldrich Corp., weight average molecular weight 87,000) was dissolved to be 15 mg / ml A field effect transistor was produced in the same manner as in Comparative Example 1, except that the organic solution was changed to the adjusted chloroform solution. With respect to the obtained field effect transistor, a voltage-current curve at the time of applying a gate voltage was obtained (FIG. 8), and field effect mobility and On / Off ratio were calculated. As a result, 4.2 × 10 ⁻³ cm 2 / Vs and 9.0 × 10.

Comparative Example 4
In Comparative Example 2, a chloroform solution of Tetorabishikuropo Le Firin, regioregular poly (3-hexylthiophene-2,5-diyl) (Aldrich Corp., weight average molecular weight 87,000) was dissolved to be 15 mg / ml A field effect transistor was produced in the same manner as in Comparative Example 2 except that the organic chloroform layer was changed to the adjusted chloroform solution. With respect to the obtained field effect transistor, a voltage-current curve when a gate voltage is applied is obtained (
FIG. 9), field effect mobility, and On / Off ratio were calculated to be 1.0 × 10 ⁻² cm ² / Vs and 3.6 × 10 ² , respectively.

Reference example 2
Heating in Example 1, a chloroform solution of Tetorabishikuropo Le Firin, poly (9,9-dioctyl fluorene -alt- bithiophene) of change in the 0.5 wt% chloroform solution, 30 minutes at 160 ° C., in a nitrogen A field effect transistor was produced in the same manner as in Example 1 except that the semiconductor layer was processed and converted. With respect to the obtained field effect transistor, a voltage-current curve at the time of gate voltage application was obtained (FIG. 10), and field effect mobility and On / Off ratio were calculated. As a result, 5.4 × 10 ⁻³ cm ² respectively. / Vs, and 3.1 × 10 ³ .

Comparative Example 5
In Comparative Example 1, a chloroform solution of Tetorabishikuropo Le Firin, poly (9,9-dioctyl fluorene -alt- bithiophene) of change in the 0.5 wt% chloroform solution, 30 minutes at 160 ° C., under nitrogen heated A field effect transistor was fabricated in the same manner as in Comparative Example 1 except that the semiconductor layer was processed and converted. With respect to the obtained field effect transistor, a voltage-current curve at the time of applying a gate voltage was obtained (FIG. 11), and field effect mobility and On / Off ratio were calculated. As a result, 3.3 × 10 ⁻³ cm ^{2 was obtained.} / Vs, and 3.5 × 10 ² .

Comparative Example 6
In Comparative Example 2, a chloroform solution of Tetorabishikuropo Le Firin, poly (9,9-dioctyl fluorene -alt- bithiophene) of change in the 0.5 wt% chloroform solution, 30 minutes at 160 ° C., under nitrogen heated A field effect transistor was produced in the same manner as in Comparative Example 2 except that the semiconductor layer was processed and converted. With respect to the obtained field effect transistor, a voltage-current curve at the time of applying a gate voltage was obtained (FIG. 12), and field effect mobility and On / Off ratio were calculated. As a result, 4.3 × 10 ⁻³ cm ² respectively. / Vs, and 8.5 × 10 ² .

Reference example 3
Prepared in Example 1, a chloroform solution of Tetorabishikuropo Le Firin, was changed to 0.1 wt% mesitylene solution of dihexyl hexathiophene, except for using the organic semiconductor layer, the field-effect transistor in the same manner as in Example 1 did. About the obtained field effect transistor, the voltage-current curve at the time of gate voltage application is calculated | required (FIG. 13), field effect mobility, and O
As a result of calculating the n / Off ratio, they were 3.2 × 10 ⁻³ cm ² / Vs and 6.8 × 10 ² , respectively.

Comparative Example 7
Produced in Comparative Example 1, a chloroform solution of Tetorabishikuropo Le Firin, was changed to 0.1 wt% mesitylene solution of dihexyl hexathiophene, except for using the organic semiconductor layer, the field-effect transistor in the same manner as in Comparative Example 1 did. The resulting field-effect transistor, the gate voltage application time of the voltage - current curve determined (FIG. 14), the field-effect mobility, and the results of calculating the On / Off ratio, respectively, 3.5 × ¹⁰ -3 cm ² / Vs, and 7.5 × 10 ² .

Comparative Example 8
Manufactured in Comparative Example 2, a chloroform solution of Tetorabishikuropo Le Firin, was changed to 0.1 wt% mesitylene solution of dihexyl hexathiophene, except for using the organic semiconductor layer, the field-effect transistor in the same manner as in Comparative Example 2 did. With respect to the obtained field effect transistor, a voltage-current curve when a gate voltage was applied was obtained (FIG. 15), and field effect mobility and On / Off ratio were calculated. As a result, 3.2 × 10 ⁻³ cm ² respectively. / Vs, and 7.5 × 10 ² .

Example 5
A field effect transistor was produced in the same manner as in Example 1 except that the polyimide precursor in Example 1 was changed to the polyimide precursor shown below (fluorine atom content 29% by weight as polyimide). The film thickness of the gate insulating layer was 9,000 mm. With respect to the obtained field effect transistor, a voltage-current curve when a gate voltage was applied was obtained in the same manner as described above, and the field effect mobility and On / Off ratio were calculated. As a result, 2.8 × 10 ^{− 2} cm ² / Vs and 2.5 × 10 ³ . Further, the water absorption of the gate insulating layer obtained here was measured by the same method as described above, and it was 0.41 mg / cm ³ .

Example 6
A field effect transistor was produced in the same manner as in Example 1 except that the polyimide precursor was changed to the polyimide precursor shown below (fluorine atom content: 16% by weight as polyimide) in Example 1. The film thickness of the gate insulating layer was 9,000 mm. With respect to the obtained field effect transistor, a voltage-current curve at the time of applying a gate voltage was obtained in the same manner as described above, and the field effect mobility and the On / Off ratio were calculated. As a result, 5.4 × 10 ^{− 2} cm ² / Vs, and 1.5 × 10 ³ . Further, the water absorption of the gate insulating layer obtained here was measured by the same method as described above, and it was 0.40 mg / cm ³ .

Example 7
A field effect transistor was produced in the same manner as in Example 1 except that the polyimide precursor in Example 1 was changed to the following polyimide precursor (fluorine atom content as polyimide: 17% by weight). The film thickness of the gate insulating layer was 9,000 mm. The resulting field-effect transistor, in the same manner as above, the voltage at the gate voltage is applied - seeking current curve, field-effect mobility, and the results of calculating the On / Off ratio, respectively, 6.2 × 10 ^{- 2} cm ² / Vs and 2.5 × 10 ³ . Further, the water absorption of the gate insulating layer obtained here was measured by the same method as described above, and it was 0.39 mg / cm ³ .

Example 8
Using a negative photoresist ZPN1100 (manufactured by Zeon Corporation) on a 4-inch glass mask wafer substrate (surface polishing, manufactured by Universal), photolithography is performed, and chromium is vacuum-deposited at a thickness of 1000 mm (vacuum degree: 10 ⁻⁶ Torr). Next, the resist pattern that is no longer needed is removed using an organic solvent, and the surface is further subjected to ultrasonic cleaning using an excitran cleaning solution (manufactured by Merck) to produce a substrate on which a chromium gate electrode is patterned on a glass wafer. did.
On top of this, 2 mL of the polyimide precursor solution used in Example 1 was developed, 3000 rpm,
Spin coating was performed for 120 seconds to form a film. This polyimide precursor film was gradually heated to 300 ° C. in nitrogen to perform imidization, thereby preparing a polyimide insulating film. As a result of measuring the film thickness of the insulating film with a film thickness meter (Alpha-Step 500: manufactured by Tencor), it was 9000 mm. When the capacitance of this insulating film was measured with an electric measuring instrument 4284A manufactured by Agilent Technologies, it was 2.84 × 10 ⁻⁹ F / cm ² .
On the polyimide insulating film, negative type photoresist ZPN1100 (manufactured by Nippon Zeon Co., Ltd.) was used again to perform photolithography to pattern the source / drain electrodes. This pattern was vapor-deposited with a thickness of 100 mm of chromium and 1000 mm of gold using a vacuum deposition machine EX-400 (manufactured by ULVAC, Inc., degree of vacuum: 10 ⁻⁶ Torr). Next, the unnecessary resist pattern was removed with an organic solvent and washed to prepare a bottom contact substrate.
Next, 7 mg of the following compound was dissolved in 1 g of chloroform at 25 ° C., and the solution prepared by filtration through a 0.2 μm filter was spin-coated at 1000 rpm on the bottom contact substrate with the polyimide insulating film prepared above to produce a thin film. did. This substrate was heat-treated at 210 ° C. for 5 minutes to convert it into a semiconductor layer, and a field effect transistor was manufactured. This field effect transistor was measured using a semiconductor parameter analyzer 4155C manufactured by Agilent Technologies, and a voltage-current curve was obtained to calculate mobility, Vt, and On / Off ratio. As a result, 0.15 cm ^{2 /} Vs, 3.4 V 1.4 × 10 ³ .

  The field effect transistor of the present invention can be used as a switching element of an active matrix of a display. This is because the current applied between the source electrode and the drain electrode can be switched by the voltage applied to the gate electrode, and the switch is turned on only when a voltage is applied to or supplied to a certain display element, and the circuit is used for other times. By cutting the line, high-speed and high-contrast display is performed. Examples of the display element to be applied include a liquid crystal display element, a polymer dispersion type liquid crystal display element, an electrophoretic display element, an electroluminescence element, and an electrochromic element.

  In particular, the field-effect transistor of the present invention can be manufactured in a low-temperature process, can use a substrate that cannot withstand high-temperature processing such as plastic, and can be manufactured in a coating or printing process. Therefore, it is also suitable for large area displays. Moreover, it is advantageous as an element capable of energy saving and a low cost process as an alternative to the conventional active matrix.

  Further, by integrating transistors, a digital element or an analog element can be realized. Examples of these include logic circuits such as AND, OR, NAND, NOT, memory elements, oscillation elements, amplification elements, and the like. Furthermore, an IC card, an IC tag, etc. can also be produced by combining these.

It is a longitudinal cross-sectional view which shows one Example of the field effect transistor of this invention. It is a longitudinal cross-sectional view which shows one Example of the field effect transistor of this invention. It is a longitudinal cross-sectional view which shows one Example of the field effect transistor of this invention. 3 is a voltage-current curve in the field effect transistor of Example 1. FIG. 6 is a voltage-current curve in the field effect transistor of Comparative Example 1. 10 is a voltage-current curve in a field effect transistor of Comparative Example 2. 4 is a voltage-current curve in the field effect transistor of Reference Example 1 . 10 is a voltage-current curve in a field effect transistor of Comparative Example 3. 10 is a voltage-current curve in a field effect transistor of Comparative Example 4. 10 is a voltage-current curve in the field effect transistor of Reference Example 2 . 10 is a voltage-current curve in a field effect transistor of Comparative Example 5. 10 is a voltage-current curve in a field effect transistor of Comparative Example 6. 10 is a voltage-current curve in a field effect transistor of Reference Example 3 . 10 is a voltage-current curve in a field effect transistor of Comparative Example 7. 10 is a voltage-current curve in a field effect transistor of Comparative Example 8. 10 is a voltage-current curve in the field effect transistor of Example 5. FIG. 10 is a voltage-current curve in the field effect transistor of Example 6. FIG. 10 is a voltage-current curve in the field effect transistor of Example 7. FIG. 10 is a voltage-current curve in the field effect transistor of Example 8. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support substrate 2 Gate electrode 3 Gate insulating layer 4 Organic-semiconductor layer 5 Source electrode 6 Drain electrode

Claims (1)

A field effect transistor having a gate insulating layer, a gate electrode and an organic semiconductor layer separated by the gate insulating layer, and a source electrode and a drain electrode provided in contact with the organic semiconductor layer on a supporting substrate. , the gate insulating layer, coating the polyimide precursor solution having any of the configurations repeating unit represented below, drying, and is formed by heat treatment, and, water absorption 0.65 mg / cm ³ or less fluorine atoms A field effect transistor, comprising: a gate insulating layer containing a containing polyimide , wherein the organic semiconductor layer is tetrabenzoporphyrin or a metal salt thereof.

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