JP5617280B2 - Field effect transistor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a field effect transistor and a method for manufacturing the field effect transistor.

  In recent years, field-effect transistors using organic semiconductor materials have been actively researched and developed. Compared to inorganic semiconductor materials typified by silicon conventionally used for semiconductor elements, this organic semiconductor material can easily form a thin film at room temperature by a printing method, and can simplify and lower the manufacturing process. Has the advantage. For this reason, the field effect transistor is expected to facilitate the formation of a semiconductor element on a plastic substrate, which has been difficult in the past, and can be manufactured in a large area at a low cost.

In such a field effect transistor, not only the characteristics of the organic semiconductor itself but also the characteristics and shape of the gate insulating film are important. A characteristic required for this gate insulating film is high insulation. In order to stably operate the field effect transistor, it is very important to ensure uniformity of film thickness and smoothness. However, in the printing method, it has been difficult to form a uniform gate insulating film on a substrate having an uneven shape formed with electrodes and the like.
As a means for solving such a problem, a method of transferring a gate insulating film formed on a smooth base material onto a substrate on which the insulating film is formed can be considered. However, this transfer method has a problem that it is difficult to remove the gate insulating film from the base material depending on the material of the gate insulating film. Furthermore, transfer onto the target substrate is difficult, and a uniform gate insulating film having the characteristics of the gate insulating film material cannot be formed.

  A fluorine-based resin is known as a highly insulating gate insulating film material, and an application to an electronic device using an organic semiconductor has been attempted (see Patent Document 1). As a method for forming the gate insulating film made of this fluororesin, a vacuum process such as a vapor deposition method or a sputtering method has been mainly used. In recent years, film formation of a fluororesin by a coating method has also been reported, but the current situation is that the coating method has the same problems as described above.

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, the present invention is manufactured by a method of manufacturing a field effect transistor capable of efficiently forming a gate insulating film having a high insulating property and a uniform film thickness, and a method of manufacturing the field effect transistor. It is an object of the present invention to provide a high-performance field effect transistor having stable characteristics.

Means for solving the problems are as follows. That is,
<1> A method for producing a field effect transistor having at least a gate electrode, a source electrode, a drain electrode, a semiconductor layer, and a gate insulating film on a first substrate,
Forming a gate electrode on the first base material; and
Applying a resin solution for forming a gate insulating film on the second substrate, forming a gate insulating film,
A drying step of drying until the fluidity of the gate insulating film surface disappears;
A contact step of bringing the first base material and the gate electrode into contact with the gate insulating film surface to form a contact body;
A heating step of applying heat above the glass transition temperature of the resin for forming a gate insulating film to the contact body;
A peeling step of peeling the second base material from the contact body and forming a gate insulating film on the first base material;
A field effect transistor manufacturing method characterized by comprising at least
<2> The method for producing a field effect transistor according to <1>, wherein the gate insulating film forming resin is a fluorine-based resin.
<3> Manufacture of a field effect transistor according to any one of <1> to <2>, further including a cooling step of cooling the contact body to a temperature not higher than a glass transition temperature of the resin for forming a gate insulating film after the heating step. Is the method.
<4> The method for producing a field effect transistor according to any one of <1> to <3>, wherein a pressure of 0.1 MPa or more is applied together with heat in the heating step.
<5> The method for producing a field effect transistor according to any one of <1> to <4>, wherein the second base material contains a silicone resin.
<6> The method for producing a field effect transistor according to <5>, wherein the second base material contains polydimethylsiloxane.
<7> The method for producing a field effect transistor according to any one of <1> to <6>, wherein the surface roughness Ra of the second base material is 10 nm or less.
<8> The method for producing a field effect transistor according to any one of <1> to <7>, wherein the second substrate is formed on a mold having a surface roughness Ra of 10 nm or less.
<9> The method for producing a field effect transistor according to any one of <1> to <8>, wherein the second base material has an uneven pattern on a surface.
<10> A field effect transistor manufactured by the method for manufacturing a field effect transistor according to any one of <1> to <9>.

  According to the present invention, a field effect transistor capable of solving the above-described problems and achieving the object, and efficiently forming a gate insulating film having high insulation and a uniform film thickness. It is possible to provide a high-performance field-effect transistor having stable characteristics, which is manufactured by the manufacturing method and the method for manufacturing the field-effect transistor.

FIG. 1 is a schematic diagram illustrating an example of a configuration of a field effect transistor. FIG. 2 is a schematic diagram illustrating another example of the configuration of the field effect transistor. FIG. 3 is a diagram showing channel lengths in the manufacturing process of the source / drain electrodes.

(Field Effect Transistor and Field Effect Transistor Manufacturing Method)
The method for producing a field effect transistor of the present invention is a method for producing a field effect transistor having at least a gate electrode, a source electrode, a drain electrode, a semiconductor layer, and a gate insulating film on a first substrate. ,
It includes at least a gate electrode formation process, a coating process, a drying process, a contact process, a heating process, and a peeling process, and includes a cooling process and, if necessary, other processes.
The manufacturing method of the field effect transistor of the present invention only needs to include at least the above-described steps, and may include other steps before, during, or during the formation of the insulating film. In these steps, the entire surface of the substrate may be processed simultaneously, or a partial process may be repeated continuously to form a gate insulating film in a desired region.
The field effect transistor of the present invention is manufactured by the method for manufacturing a field effect transistor of the present invention.
Hereinafter, the details of the field effect transistor of the present invention will be clarified through the description of the method of manufacturing the field effect transistor of the present invention.

<Gate electrode formation process>
The gate electrode forming step is a step of forming a gate electrode on the first base material.

-First substrate-
The first substrate is not particularly limited as long as it is a substrate capable of forming a field effect transistor, and can be appropriately selected according to the purpose. For example, glass; polycarbonate, polyethylene naphthalate, polyarylate, Examples thereof include plastics such as polyethersulfone and polyester; metals such as silicon and stainless steel. Among these, polycarbonate and polyethylene naphthalate are particularly preferable from the viewpoints of heat resistance and durability.

-Gate electrode-
The gate electrode is not particularly limited as long as it can flow a current sufficient for driving a semiconductor element, and can be appropriately selected according to the purpose. For example, platinum, gold, silver, nickel, chromium Metals such as copper, iron, zinc, tin, tantalum, aluminum, indium, and tungsten; oxides such as ATO, ITO, IZO, and FTO; conductive materials such as conductive polyaniline, conductive polypyrrole, conductive polythiophene, and PEDOT / PSS Functional polymer; carbon and the like. These may be used individually by 1 type and may use 2 or more types together. Among these, platinum, gold, silver, copper, aluminum, indium, ITO, IZO, PEDOT / PSS, and carbon are particularly preferable.

  There is no restriction | limiting in particular as a formation method of the said gate electrode, According to the objective, it can select suitably, For example, a vapor deposition method, a sputtering method, a printing method etc. are mentioned. Among these, the printing method is particularly preferable from the viewpoint of process simplicity.

<Application process>
The coating step is a step of coating the second base material with a resin solution for forming a gate insulating film to form a gate insulating film.

-Second base material-
There is no restriction | limiting in particular as said 2nd base material, Although it can select suitably according to the objective, It is an elastic body at the point which the adhesiveness to the 1st base material which is a transfer destination, and a gate electrode improves. It is preferable that
As the second substrate, a silicone resin is preferably used from the viewpoints of flexibility and durability. Among these, polydimethylsiloxane is particularly preferable.
When polydimethylsiloxane is used as the second substrate, the method for producing a field effect transistor of the present invention has excellent transferability of the insulating film, and the field effect transistor can be produced more stably. It becomes. The silicone resin (or polydimethylsiloxane) is preferably contained as a main component (90% by mass or more) in the second base material.
The silicone resin (or polydimethylsiloxane) is preferably crosslinked with a crosslinking agent in terms of durability.
In order to improve transferability of the gate insulating film to the first substrate, the surface of the second substrate preferably has water repellency. The contact angle of distilled water on the surface of the second substrate is preferably 90 degrees or more, and more preferably 110 degrees or more.
The contact angle of the distilled water can be measured, for example, by dropping 1 μL of water onto a second substrate placed horizontally and using a contact angle meter.

The surface roughness Ra of the second base material is preferably 10 nm or less, and more preferably 1 nm to 5 nm. When the surface roughness Ra of the second substrate is 10 nm or less, the surface of the formed gate insulating film becomes smoother, and as a result, a field effect transistor having stable characteristics can be provided.
The surface roughness Ra can be measured by, for example, an atomic force microscope (AFM).

The second substrate can be produced by curing a silicone resin on a mold having an arbitrary shape. In this case, if the surface roughness Ra of the mold surface is 10 nm or less, a second substrate having a smooth surface can be easily obtained.
Moreover, if there is an uneven pattern on the surface of the mold, the uneven pattern can be formed on the second substrate in accordance with the shape.
As the material used for the mold, glass, silicon, or the like is preferable from the viewpoint of ease of mold release processing or molding, and it is further possible to cure the resist material to an arbitrary shape on a substrate such as glass. It can be easily manufactured. Among these, quartz glass is preferable for obtaining a mold having a smooth surface, and a silicon substrate is particularly preferable for obtaining a smooth surface.

By patterning only the necessary part of the fluororesin on the second substrate, it is possible to form the gate insulating film only on the necessary part on the first substrate as the transfer destination.
There is no restriction | limiting in particular as said patterning method, According to the objective, it can select suitably, An inkjet, offset printing, etc. are mentioned. In addition, there is a method in which patterning is performed on the surface of the second substrate by light, heat, chemical modification, or the like, and a fluororesin is selectively formed on the obtained pattern. Thus, if it is a method of forming an uneven | corrugated pattern in the 2nd base material surface, it will become possible to pattern a gate insulating film with a simpler process.

-Resin solution for gate insulating film formation-
The gate insulating film forming resin solution is a solution in which an insulating film forming resin is dissolved in an organic solvent or in which resin particles are dispersed in an organic solvent or water. Among these, from the viewpoint of the uniformity of the obtained gate insulating film and the stability of the solution, a solution in which the insulating film forming resin is dissolved in an organic solvent is preferable.
It is preferable from the viewpoint of durability that the resin for forming an insulating film can be cured by applying energy such as light or heat after being formed on the first substrate.
The insulating film forming resin may contain a crosslinking agent that undergoes a crosslinking reaction with the resin.

  The insulating film forming resin is not particularly limited as long as it has an insulating property that functions as a gate insulating film, and can be appropriately selected according to the purpose. For example, polyethylene, polypropylene, polystyrene, polyisobutylene, poly Examples include vinyl chloride, phenol resin, polyamide, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, epoxy resin, polyphenylene sulfide, polyetherimide, polyethylene naphthalate, polyethersulfone, polyimide, and other general-purpose resins, fluorine-based resins, and the like. These may be used individually by 1 type and may use 2 or more types together. Among these, a fluorine-based resin is particularly preferable from the viewpoint of electrical characteristics.

  There is no restriction | limiting in particular as said fluororesin, According to the objective, it can select suitably, For example, tetrafluoroethylene-hexafluoropropylene copolymer, polytetrafluoroethylene, tetrafluoroethylene-ethylene copolymer, tetra Fluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinyl fluoride, and the like. These may be used individually by 1 type and may use 2 or more types together. Among these, fluorine resins that can be dissolved in an organic solvent are preferable, and Zeffle GK-500 (manufactured by Daikin Industries, Ltd.) and Cytop (manufactured by Asahi Glass Co., Ltd.) are particularly preferable.

  The coating method of the gate insulating film forming resin solution is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a coating method using a spin coater, a slit coater, a die coater, a spray coater, a bar coater, or the like. Etc.

<Drying process>
The drying step is a step of drying until the fluidity of the gate insulating film surface disappears.

When transfer is performed with the gate insulating film surface maintaining fluidity, there is a problem that the second substrate is displaced from a desired position due to the force applied at the time of transfer, but drying is performed until the fluidity disappears. This makes it possible to avoid the above problem. In addition, it is preferable to perform transfer before the gate insulating film is completely dried in order to improve transferability.
The determination until the fluidity of the surface of the gate insulating film disappears can be made by measuring, for example, a change with time of the adhesiveness of the surface.

<Contact process>
The contact step is a step of forming a contact body by bringing the first base material and the gate electrode into contact with the surface of the gate insulating film.
It is preferable to apply pressure during the contact.

<Heating process>
The heating step is a step of applying heat above the glass transition temperature of the resin for forming a gate insulating film to the contact body.
The contact step and the heating step may be performed sequentially, but the contact step and the heating step may be performed simultaneously.

By applying heat equal to or higher than the glass transition temperature of the resin for forming the gate insulating film, the transferability of the resin can be improved.
The glass transition temperature of the resin for forming a gate insulating film is preferably 50 ° C. to 200 ° C.
In the heating step, it is preferable to apply a pressure of 0.1 MPa or more (preferably 0.2 to 0.5 MPa) together with the heating because transferability can be further improved.
There is no restriction | limiting in particular as said heating method, According to the objective, it can select suitably, For example, the heating by a heat roller, a hot plate, a thermal head, an infrared heater etc. is mentioned.

<Peeling process>
The peeling step is a step of peeling the second base material from the contact body and forming a gate insulating film on the first base material.
The film thickness (channel portion) of the formed gate insulating film is preferably 100 nm to 1,500 nm, and more preferably 300 nm to 1,000 nm.
The film thickness of the gate insulating film (channel portion) can be measured by, for example, a stylus type step gauge (ET4000L, manufactured by Kosaka Laboratory).

<Cooling process>
The said cooling process is a process of cooling a contact body to the temperature below the glass transition temperature of resin for gate insulating film formation after the said heating process.
The peeling step and the cooling step may be performed sequentially, but the peeling step and the cooling step may be performed simultaneously.

  In the cooling step, it is possible to improve transferability to the first substrate by cooling to a temperature not higher than the glass transition temperature of the gate insulating film-forming resin after heating, preferably to room temperature (25 ° C.). Become.

<Other processes>
There is no restriction | limiting in particular as said other process, Although it can select suitably according to the objective, A source electrode formation process, a drain electrode formation process, a semiconductor layer formation process, etc. are mentioned.

  The source electrode formation step and the drain electrode formation step can be formed by the same method using the same material as the gate electrode step.

  In the semiconductor layer forming step, the semiconductor material is not particularly limited and may be appropriately selected depending on the purpose. For example, low molecular organic semiconductors such as pentacene, anthracene, tetracene, porphyrins or derivatives thereof; Organic pigments such as organic silicon compounds, conjugated polymers such as polythiophene, polypyrrole, polyaniline, polyphenylene, polyphenylene vinylene, or derivatives thereof, and general organic semiconductor materials.

  There is no restriction | limiting in particular as a formation method of the said semiconductor layer, According to the objective, it can select suitably, For example, a printing method, a vapor deposition method, a sputtering method etc. are mentioned. Among these, the printing method is particularly preferable from the viewpoint of process simplicity.

There is no restriction | limiting in particular as a field effect transistor manufactured by the manufacturing method of the field effect transistor of this invention, It can select suitably according to the objective, Generally, support substrates, such as glass and a plastics , A gate electrode, a source electrode, a drain electrode, a gate insulating film, and an organic semiconductor layer.
By changing the gate voltage, the charge amount at the interface between the gate insulating film and the organic semiconductor layer is controlled, and the magnitude of the drain current flowing between the drain electrode and the source electrode is changed to perform switching.
On the first substrate to which the gate insulating film is transferred, other members constituting the field effect transistor may be formed first.

Here, as a configuration of the field effect transistor, as shown in FIG. 1, a gate electrode 2 is formed on a first base material 1, and a gate insulating film 3 is formed so as to cover the gate electrode 2. In addition, the source electrode 5 and the drain electrode 6 are formed on the gate insulating film 3 and the organic semiconductor layer 4 is formed to form a field effect transistor.
Further, as shown in FIG. 2, a gate electrode 12 is formed on the first base material 11, a gate insulating film 13 is formed so as to cover the gate electrode 12, and an organic material is formed on the gate insulating film 13. After the semiconductor layer 14 is formed, a source electrode 15 and a drain electrode 16 are further formed to form a field effect transistor.
As the configuration of the field effect transistor, an optimal configuration can be selected depending on the suitability of the process, and the present invention is not limited to these configurations.

The method for producing the field effect transistor of the present invention is not particularly limited and can be appropriately selected according to the purpose, but is suitable as a method for producing an active matrix substrate. In this case, a field effect transistor is used as a thin film device on the first base material, thin film transistors (TFTs) are formed in a matrix, and an active matrix substrate having the thin film transistors in a matrix is manufactured.
In addition, a thin film transistor (TFT) for a driving circuit is formed as the thin film device on the first base material, and an active matrix substrate having a driving circuit including the thin film transistor can be manufactured.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
<Fabrication of field effect transistor>
Five field-effect transistors were produced by a method described in the following (1) to (5) with a predetermined interval on a glass substrate. These are the lot numbers of Example 1. 1 to lot no. It was set to 5.

(1) Formation of gate electrode A nano silver solution was applied on a glass substrate (first base material) by a spin coating method to form a nano silver thin film having a thickness of 500 nm. After baking this nano silver thin film, a photoresist (TSMR8800BE, manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied by a spin coating method to form a 1 μm thick photoresist layer, and pre-annealed at 90 ° C. for 30 minutes.
Next, the photoresist layer was exposed through a photomask and developed and post-baked at 120 ° C. for 20 minutes.
Next, the nano silver thin film is etched with an etching solution (SEA-5, manufactured by Kanto Chemical Co., Inc.), and the resist layer is peeled off and rinsed, so that the gate electrode and the scanning are 500 μm in length, 100 μm in width, and 500 nm in height. A line was formed.

(2) Production of Second Base Material For 100 parts by mass of polydimethylsiloxane (trade name: KE-106, manufactured by Shin-Etsu Chemical Co., Ltd.), a curing agent (trade name: Cat-RG, manufactured by Shin-Etsu Chemical Co., Ltd.). ) 10 parts by mass are mixed, developed on a release-treated glass substrate (surface roughness Ra = 12 nm), heated at 120 ° C. for 60 minutes, peeled off from the glass substrate, and a second 2 mm thick second A substrate was used.
The surface roughness Ra of the obtained second substrate was measured with an atomic force microscope (AFM) (SFT-3500, manufactured by Shimadzu Corporation), and found to be 15 nm.

(3) Formation of gate insulating film On a second base material, a fluorine-based resin solution (trade name: Cytop CTL-809M, manufactured by Asahi Glass Co., Ltd., glass transition temperature 108 ° C.) is applied using a spin coater. When heated to 60 ° C. on a hot plate and the fluidity of the surface was lost, the glass substrate (first base material) on which the gate electrode was formed was contacted so as to cover the gate electrode. . After heating for 1 minute on a 120 ° C hot plate in that state, the glass substrate is cooled to room temperature (25 ° C), and only the second substrate is peeled off from the glass substrate to form a gate insulating film. did.

(4) Production of Source / Drain Electrode A nano silver solution is printed on the gate insulating film by a screen printing method at a position overlapping the gate electrode, the source electrode having a length of 600 μm, a width of 100 μm, a height of 1 μm, and the same shape A drain electrode and respective scanning lines were formed and baked to produce a source / drain electrode. Here, the channel length between the source and drain electrodes was 50 μm (see FIG. 3).

(5) Preparation of organic semiconductor layer A chloroform solution of poly-3-hexylthiophene was dropped onto the channel and dried to form an organic semiconductor layer.

(Example 2)
In Example 1, five field effect transistors were produced in the same manner as in Example 1 except that the second substrate was used as described below. These are designated as lot No. 2 in Example 2. 1 to lot no. It was set to 5.
(2) Production of second substrate 10 parts by mass of curing agent (Cat-RG, manufactured by Shin-Etsu Chemical Co., Ltd.) with respect to 100 parts by mass of polydimethylsiloxane (trade name: KE-106, manufactured by Shin-Etsu Chemical Co., Ltd.) Parts are mixed, developed on a release-treated silicon substrate (surface roughness Ra = 1 nm), heated at 120 ° C. for 60 minutes, peeled off from the silicon substrate, did.
The surface roughness Ra of the obtained second substrate was measured in the same manner as in Example 1 and found to be 3 nm.

(Comparative Example 1)
In Example 1, five field effect transistors were produced in the same manner as in Example 1 except that the gate insulating film was produced by the following method. These were designated as lot Nos. 1 to lot no. It was set to 5.
(3) Formation of gate insulating film A fluorine-based resin solution (trade name: Cytop CTL-809M, manufactured by Asahi Glass Co., Ltd., glass transition temperature 108 ° C.) is formed on the gate electrode produced in (2) above by a spin coater method. Was applied and dried to form an insulating film.

  Next, with respect to the produced Examples 1 and 2 and Comparative Example 1, the characteristics of the transistor were evaluated and the film thickness of the gate insulating film was measured under the conditions of room temperature and nitrogen atmosphere as follows. The results are shown in Table 1.

<Characteristics of drain current (Id-on, Vg = -80V)>
With a voltage of −80 V applied to the gate electrode, a voltage of 40 V was applied between the source and drain electrodes with the source electrode as the ground, and the current flowing through the drain electrode was measured.

<Gate insulating film thickness>
The film thickness of the gate insulating film (channel portion) was measured using a stylus-type step gauge (ET4000L, manufactured by Kosaka Laboratory) after evaluation of transistor characteristics.

表１の結果から、実施例１〜２及び比較例１は、いずれも典型的なｐ型トランジスタの特性を示すことが分かった。
また、実施例１〜２に比べて比較例１では、ドレイン電流（Ｉｄ−ｏｎ、Ｖｇ＝−８０Ｖ）の特性のばらつきが大きい結果となった。これは、ゲート絶縁膜（チャネル部）の膜厚のばらつきが大きいことが原因であると考えられる。

From the results of Table 1, it was found that Examples 1 and 2 and Comparative Example 1 all showed typical p-type transistor characteristics.
Further, compared to Examples 1 and 2, in Comparative Example 1, the variation in the characteristics of the drain current (Id-on, Vg = -80 V) was large. This is considered to be caused by a large variation in the film thickness of the gate insulating film (channel portion).

  The field effect transistor manufactured by the method of manufacturing a field effect transistor according to the present invention has a highly insulating and uniform gate insulating film and has stable characteristics without variations. It is suitable for an active matrix (AFT) substrate.

1, 11 Substrate 2, 12, 21 Gate electrode 3, 13 Gate insulating film 4, 14 Semiconductor layer 5, 15, 22 Source electrode 6, 16, 23 Drain electrode 7, 17 Channel region

JP-A-1-37872

Claims (10)

A method of manufacturing a field effect transistor having at least a gate electrode, a source electrode, a drain electrode, a semiconductor layer, and a gate insulating film on a first substrate,
Forming a gate electrode on the first base material; and
Applying a resin solution for forming a gate insulating film on the second substrate, forming a gate insulating film,
A drying step of drying until the fluidity of the gate insulating film surface disappears;
A contact step of bringing the first base material and the gate electrode into contact with the gate insulating film surface to form a contact body;
A heating step of applying heat above the glass transition temperature of a fluororesin that is a resin for forming a gate insulating film to the contact body;
After the heating step, a cooling step for cooling the contact body to a temperature not higher than the glass transition temperature of the fluororesin,
A peeling step of peeling the second base material from the contact body and forming a gate insulating film on the first base material;
A method for producing a field-effect transistor characterized by comprising: The fluororesin is selected from tetrafluoroethylene-hexafluoropropylene copolymer, polytetrafluoroethylene, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and polyvinyl fluoride. 2. The method for producing a field effect transistor according to claim 1, wherein the field effect transistor is at least one kind. The method for producing a field effect transistor according to claim 1, wherein the cooling step cools to 25 ° C. which is a temperature not higher than the glass transition temperature.   4. The method for manufacturing a field effect transistor according to claim 1, wherein a pressure of 0.1 MPa or more is applied together with heat in the heating step.   The method for producing a field effect transistor according to any one of claims 1 to 4, wherein the second base material contains a silicone resin.   The method for producing a field effect transistor according to claim 5, wherein the second substrate contains polydimethylsiloxane.   The method for producing a field effect transistor according to claim 1, wherein the surface roughness Ra of the second substrate is 10 nm or less.   The method for producing a field effect transistor according to claim 1, wherein the second substrate is formed on a mold having a surface roughness Ra of 10 nm or less.   The method for producing a field effect transistor according to claim 1, wherein the second substrate has an uneven pattern on the surface.   A field effect transistor manufactured by the method for manufacturing a field effect transistor according to claim 1.

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