JP2016082198A - Thin film transistor and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin film transistor which has a gallium-free oxide semiconductor layer and high mobility; and provide a manufacturing method of the thin film transistor.SOLUTION: A thin film transistor 10 which has a gate electrode 2, a gate insulation layer 3, an oxide semiconductor layer 4, a source electrode 5 and a drain electrode 6, in which the oxide semiconductor layer 4 is formed by indium tungsten zinc oxide. It is preferable to achieve the thin film transistor 10 in which the indium tungsten zinc oxide contains WOwithin a range of 5.0-15.5 mass%. It is preferable to achieve the thin film transistor 10 in which the indium tungsten zinc oxide contains ZnO within a range of 0.2-0.8 mass%.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thin film transistor and a manufacturing method thereof, and more particularly to a thin film transistor using indium tungsten zinc oxide (In—W—Zn—O) for a channel layer (active layer) of the thin film transistor and a manufacturing method thereof.

  Conventionally, a thin film transistor (hereinafter also referred to as a TFT (Thin-Film Transistor)) is used for a driving circuit of a display device such as a display. As a thin film transistor, a thin film transistor in which an oxide semiconductor layer made of indium gallium zinc oxide (In-Ga-Zn-O (IGZO: trademark registration No. 5451521)) is attracting attention as a channel layer where a channel is formed. .

  A TFT using In—Ga—Zn—O for a channel layer (hereinafter sometimes referred to as IGZO-TFT) has a higher electron movement speed than a TFT using amorphous silicon (see Non-Patent Document 1). ).

K. Nomura et al., Nature vol. 432, p. 488 (2004)

  However, the IGZO-TFT contains gallium whose output is limited. For this reason, it has been required to realize a thin film transistor having high mobility by using a channel layer that does not contain gallium.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thin film transistor having an oxide semiconductor layer not containing gallium and having high mobility, and a method for manufacturing the thin film transistor.

In order to solve the above-mentioned problems, the present inventor has intensively studied a material that does not contain gallium and can obtain high mobility as a material of an oxide semiconductor layer of a thin film transistor. As a result, it was found that indium tungsten zinc oxide should be used, and the present invention has been completed.
That is, the present invention relates to the following inventions.

[1] A gate electrode, a gate insulating layer, an oxide semiconductor layer, a source electrode, and a drain electrode are provided, and the oxide semiconductor layer is formed of indium tungsten zinc oxide. Thin film transistor.
[2] The thin film transistor according to indium tungsten oxide zinc, characterized in that it contains a WO ₃ 5.0-15.5 wt% [1].
[3] The thin film transistor according to [1] or [2], wherein the indium tungsten zinc oxide contains 0.2 to 0.8% by mass of ZnO.

[4] The gate electrode is provided on a substrate, the oxide semiconductor layer is provided on the gate electrode through the gate insulating layer, and the source electrode is partially formed on the oxide semiconductor layer. It is overlapped and in contact in a plan view, and the drain electrode is spaced apart from the source electrode, and is in contact with a part of the oxide semiconductor layer so as to overlap in a plan view [1] The thin film transistor according to any one of to [3].

[5] A stacking step of forming a gate electrode, a gate insulating layer, an oxide semiconductor layer made of indium tungsten zinc oxide and an electrode layer in this order on a substrate, and a part of the electrode layer, the oxide semiconductor A method of manufacturing a thin film transistor, comprising: an etching step of forming a source electrode and a drain electrode having a predetermined shape by removing the layer by wet etching until the layer is exposed.

  In the thin film transistor of the present invention, the oxide semiconductor layer is formed of indium tungsten zinc oxide. Therefore, gallium is not included as a material of the oxide semiconductor layer. Further, since the oxide semiconductor layer is formed using indium tungsten zinc oxide, a thin film transistor having high mobility can be obtained. Therefore, for example, when the thin film transistor of the present invention is used in a pixel drive circuit of a display device, the pixel of the display device can be driven at high speed.

  In the method for manufacturing a thin film transistor of the present invention, the oxide semiconductor layer and the electrode layer are formed in this order, and then part of the electrode layer is removed by wet etching until the oxide semiconductor layer is exposed. In the manufacturing method of the present invention, indium tungsten zinc oxide having resistance to a wet etching solution is used as a material for the oxide semiconductor layer in wet etching for forming a source electrode and a drain electrode. Therefore, when wet etching for forming the source electrode and the drain electrode is performed, it is not necessary to form an etching stopper layer in addition to the oxide semiconductor layer. Therefore, for example, as compared with the case where an etching stopper layer is formed in addition to the oxide semiconductor layer, it can be efficiently manufactured with fewer steps.

It is the cross-sectional schematic diagram which showed an example of the thin-film transistor of this invention. It is a cross-sectional schematic diagram for demonstrating an example of the manufacturing method of the thin-film transistor shown in FIG. It is a cross-sectional schematic diagram for demonstrating an example of the manufacturing method of the thin-film transistor shown in FIG. 3 is a graph showing gate voltage-drain current characteristics of the thin film transistor of Example 1. FIG. 6 is a graph showing the gate voltage-drain current characteristics of the thin film transistor of Example 2. 6 is a graph showing the gate voltage-drain current characteristics of the thin film transistor of Example 3. 6 is a graph showing the gate voltage-drain current characteristics of the thin film transistor of Example 4. 6 is a graph showing the gate voltage-drain current characteristics of the thin film transistor of Example 5.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments, and it is easy for those skilled in the art to change the modes and details in various ways without departing from the spirit and scope of the present invention. Understood. Therefore, the present invention should not be construed as being limited to the description of the embodiments below.

"Thin Film Transistor"
FIG. 1 is a schematic cross-sectional view showing an example of a thin film transistor of the present invention.
A thin film transistor 10 shown in FIG. 1 is a bottom gate-top contact type TFT. In FIG. 1, reference numeral 1 denotes a substrate. A gate electrode 2 is provided on the substrate 1. An oxide semiconductor layer 4 is provided on the gate electrode 2 with a gate insulating film 3 interposed therebetween. On the oxide semiconductor layer 4, a source electrode 5 and a drain electrode 6 that is spaced apart from the source electrode 5 are provided.

  The substrate 1 is not particularly limited, and can be selected according to the use of the thin film transistor 10. For example, as the substrate 1, a silicon substrate, a glass substrate, a plastic film substrate, or the like can be used. As a plastic film board | substrate, what consists of a polyethylene terephthalate (PET), a polyethylene naphthalate (PEN) etc. can be used, for example.

As the gate electrode 2, for example, a metal such as Ti, Mo, W, Al, or Au, or a conductive oxide such as ITO (Indium Tin Oxide) can be used.
Alternatively, a highly doped silicon substrate into which dopant atoms are implanted at a high concentration may be used as the substrate 1 that also serves as the gate electrode 2.

As the gate insulating layer 3, for example, Si oxide, Si nitride, Al oxide, Al nitride, or the like can be used.
As the source electrode 5 and the drain electrode 6, for example, a metal material such as Al, Mo, or an alloy thereof can be used. The source electrode 5 and the drain electrode 6 may be made of a single metal layer or may have a laminated structure in which a plurality of metal layers made of different metal materials are laminated. Examples of such a laminated structure include a three-layer structure of a Mo alloy layer, an Al layer, and a Mo alloy layer.
As shown in FIG. 1, each of the source electrode 5 and the drain electrode 6 is in contact with a part of the oxide semiconductor layer 4 so as to overlap in plan view.

  The oxide semiconductor layer 4 is formed of amorphous indium tungsten zinc oxide (In—W—Zn—O). Indium tungsten zinc oxide is excellent in acid resistance, and has sufficiently high resistance to an etching solution used when wet etching a metal. For this reason, for example, when the source electrode 5 and the drain electrode 6 are formed by wet etching, an etching stopper layer is unnecessary.

Indium tungsten oxide zinc which forms the oxide semiconductor layer 4 preferably contains a WO ₃ from 5.0 to 15.5 wt%. When WO ₃ is contained in an amount of 5.0% by mass or more, more preferably 10.0% by mass or more, the reliability of the thin film transistor 10 is improved. Further, when WO ₃ is contained in an amount of 5.0% by mass or more, more preferably 10.0% by mass or more, the heat resistance of the oxide semiconductor layer 4 is improved. However, when the content of WO ₃ exceeds 15.0 mass%, the mobility of the thin film transistor 10 may be insufficient. Therefore, the content of WO ₃ is preferably 15.0% by mass or less, and more preferably 12.5% by mass or less.

  The indium tungsten zinc oxide forming the oxide semiconductor layer 4 preferably contains 0.2 to 0.8% by mass of ZnO. When the indium tungsten zinc oxide contains ZnO in an amount of 0.2 to 0.8% by mass, the oxide semiconductor layer 4 having a high film density can be obtained, so that the reliability of the thin film transistor 10 is improved. In order to obtain the oxide semiconductor layer 4 having a high film density, it is more preferable to contain 0.3 to 0.7 mass of ZnO.

The composition of the indium tungsten zinc oxide forming the oxide semiconductor layer 4 contains 5.0 to 15.5% by mass of WO ₃ , 0.2 to 0.8% by mass of ZnO, and the balance is In. ₂ O ₃ is preferred.
Although the thickness of the oxide semiconductor layer 4 is not specifically limited, For example, when using the thin-film transistor 10 for the pixel drive circuit of a display apparatus, it is preferable that it is 10-50 nm.

"Production method"
The thin film transistor 10 shown in FIG. 1 can be manufactured by, for example, the following method.
First, as shown in FIG. 2, a gate electrode 2 and a gate insulating film 3 are sequentially formed on a substrate 1 by using a conventionally known method.
Next, an oxide semiconductor layer 4 made of indium tungsten zinc oxide is formed over the gate insulating film 3.

The oxide semiconductor layer 4 can be formed by a method such as sputtering, chemical vapor deposition (CVD), or coating. When the oxide semiconductor layer 4 is formed by sputtering, for example, the oxide semiconductor layer 4 having a desired composition can be obtained by adjusting the composition of the target and the film formation conditions. Examples of film formation conditions include the type and flow rate of gas supplied to the chamber during film formation. Specifically, when the oxide semiconductor layer 4 is formed by sputtering, a mixed gas of an inert gas such as Ar gas and O ₂ gas is preferably supplied at a predetermined flow rate during film formation.
After the oxide semiconductor layer 4 is formed in this manner, heat treatment for removing defects present in the oxide semiconductor layer 4 may be performed as necessary.

Next, as illustrated in FIG. 2, an electrode layer 51 to be the source electrode 5 and the drain electrode 6 is formed over the oxide semiconductor layer 4. The electrode layer 51 can be formed using a conventionally known method.
Next, a layer serving as a mask is formed on the electrode layer 51 using a conventionally known method and material. Thereafter, using a conventionally known method, the mask layer is patterned to form a mask 52 having a predetermined shape corresponding to the shape of the source electrode 5 and the drain electrode 6 as shown in FIG.

  After that, part of the electrode layer 51 is removed by wet etching until part of the oxide semiconductor layer 4 (indicated by reference numeral 4a in FIG. 1) is exposed. Thereafter, by removing the mask 52, the source electrode 5 and the drain electrode 6 having a predetermined shape are obtained.

As an etching solution used when the electrode layer 51 is wet-etched, an etching solution usually used when wet-etching a metal can be used, and is not particularly limited. Specifically, examples of the etchant include a mixed acid Al etchant manufactured by Kanto Chemical Co., Inc.
After forming the source electrode 5 and the drain electrode 6 in this manner, heat treatment for removing defects existing in the source electrode 5 and the drain electrode 6 may be performed as necessary.
By performing the above steps, the thin film transistor 10 shown in FIG. 1 is obtained.

  In the thin film transistor 10 of this embodiment, the oxide semiconductor layer 4 is formed of indium tungsten zinc oxide. Therefore, gallium is not used as the material of the oxide semiconductor layer 4. In the thin film transistor 10 of this embodiment, since the oxide semiconductor layer 4 is formed of indium tungsten zinc oxide, high mobility can be obtained.

In the thin film transistor 10 of this embodiment, when the oxide semiconductor layer 4 is formed of indium tungsten zinc oxide containing 5.0 to 15.5% by mass of WO ₃ , it is excellent in reliability and heat resistance, and is movable. It will be a high degree.
Further, when the oxide semiconductor layer 4 is formed of indium tungsten zinc oxide containing 0.2 to 0.8% by mass of ZnO, the film density is high and the reliability is excellent.

  In the thin film transistor 10 of this embodiment, the gate electrode 2 is provided on the substrate 1, the oxide semiconductor layer 4 is provided on the gate electrode 2 through the gate insulating layer 3, and the source electrode 5 is provided in the oxide semiconductor layer. 4 is a bottom gate which is in contact with a part of 4 on the oxide semiconductor layer so as to overlap with the drain electrode 6 and is spaced apart from the source electrode 5 and which is in contact with a part of the top of the oxide semiconductor layer 4 so as to overlap with each other. -A top contact type TFT. Therefore, in the wet etching for forming the source electrode 5 and the drain electrode 6 when the thin film transistor 10 is manufactured, the oxide semiconductor layer 4 has resistance to the wet etching solution, so that an etching stopper layer is unnecessary. Therefore, for example, as compared with the case where an etching stopper layer is formed in addition to the oxide semiconductor layer 4, it can be efficiently manufactured with fewer steps.

  In the method for manufacturing the thin film transistor 10 of this embodiment, after the oxide semiconductor layer 4 and the electrode layer 51 are formed in this order, a part of the electrode layer 51 is subjected to wet etching until the oxide semiconductor layer 4 is exposed. Remove. Therefore, it is not necessary to form an etching stopper layer in addition to the oxide semiconductor layer 4 in the wet etching for forming the source electrode 5 and the drain electrode 6. Therefore, for example, as compared with the case where an etching stopper layer is formed in addition to the oxide semiconductor layer 4, it can be efficiently manufactured with fewer steps.

On the other hand, when the oxide semiconductor layer 4 is formed of indium gallium zinc oxide (In—Ga—Zn—O), the oxide semiconductor layer 4 cannot be used as an etching stopper layer. This is because Ga ₂ O ₃ contained in indium gallium zinc oxide is easily dissolved in an etching solution used for removing the source electrode 5 and the drain electrode 6. Therefore, when the oxide semiconductor layer 4 is formed of indium gallium zinc oxide, it is necessary to form an etching stopper layer in addition to the oxide semiconductor layer 4.

"Other examples"
The present invention is not limited to the above embodiment.
In the above embodiment, the bottom gate-top contact type TFT has been described as an example, but the thin film transistor of the present invention is not limited to this structure. For example, the thin film transistor of the present invention is a top-gate TFT in which an oxide semiconductor layer is provided under a gate electrode with a gate insulating film interposed therebetween, and an oxide semiconductor layer is provided between the substrate and the gate electrode. Alternatively, a bottom contact TFT in which the source electrode and the drain electrode are disposed on the substrate side of the oxide semiconductor layer may be used.

Hereinafter, the present invention will be specifically described based on examples. In addition, this invention is not limited only to these Examples.
"Example 1"
The thin film transistor 10 shown in FIG. 1 was formed and evaluated by the following method.
First, a highly doped silicon substrate was prepared as the substrate 1 that also served as the gate electrode 2, and the gate insulating film 3 made of a SiO ₂ thermal oxide film having a thickness of 100 nm was formed by thermally oxidizing the surface silicon.

Thereafter, it was formed on the gate insulating film 3 by sputtering using indium tungsten zinc oxide containing 5.0 mass% WO ₃ , 0.5 mass% ZnO and 94.5 mass% In ₂ O ₃ . An oxide semiconductor layer 4 with a thickness of 30 nm was formed. Sputtering was performed with an applied power of 100 W at high frequency (RF), a gas flow rate during film formation of Ar gas at 18.0 sccm and O ₂ gas at 2.0 sccm.

  Next, the source electrode 5 and the drain electrode 6 illustrated in FIG. 1 were formed over the oxide semiconductor layer 4 using a metal mask. The source electrode 5 and the drain electrode 6 have a three-layer structure in which a Mo alloy layer having a thickness of 10 nm, an Al layer having a thickness of 30 nm, and a Mo alloy layer having a thickness of 10 nm are sequentially stacked from the bottom. did. The Mo alloy layer was formed using MTD-46 (trade name: manufactured by Hitachi Metals, Ltd.). The Al layer was formed using a general material.

  Next, the substrate 1 on which the layers up to the source electrode 5 and the drain electrode 6 were formed was heat-treated in the atmosphere at 200 ° C. for 1 hour using a hot plate.

Through the above steps, the thin film transistor of Example 1 was obtained. Note that the thin film transistor of Example 1 was manufactured so as to have a channel length of 200 μm and a channel width of 1000 μm.
The thin film transistor of Example 1 thus obtained was measured for gate voltage-drain current characteristics using a semiconductor parameter analyzer. As for the gate voltage-drain current characteristics, 0 V was applied to the source electrode, 10 V was applied as the drain voltage to the drain electrode, the gate voltage applied to the gate electrode was changed, and the drain current at that time was measured. The result is shown in FIG.

FIG. 4 is a graph showing the gate voltage-drain current characteristics of the thin film transistor of Example 1. As shown in FIG. 4, the thin film transistor of Example 1 had good transistor characteristics. In addition, the thin film transistor of Example 1 had a mobility of 16.5 cm ² / Vs and high mobility.

"Example 2"
On the gate insulating film 3 formed in the same manner as in Example 1, an oxide containing 10.0% by mass of WO ₃ , 0.5% by mass of ZnO and 89.5% by mass of In ₂ O ₃ is formed by sputtering. An oxide semiconductor layer 4 made of indium tungsten zinc and having a thickness of 10 nm was formed. Sputtering was performed with an applied power of 100 W at high frequency (RF), a gas flow rate during film formation of Ar gas 19.6 sccm and O ₂ gas 0.4 sccm.

Next, a source electrode 5 and a drain electrode 6 were formed on the oxide semiconductor layer 4 in the same manner as in Example 1.
Thereafter, the substrate 1 on which the layers up to the source electrode 5 and the drain electrode 6 were formed was subjected to heat treatment at 250 ° C. for 1 hour in the air using a hot plate.

Through the above process, the thin film transistor of Example 2 was obtained. Note that the thin film transistor of Example 2 was manufactured to have a channel length of 200 μm and a channel width of 1000 μm, similarly to the thin film transistor of Example 1.
With respect to the thin film transistor of Example 2 thus obtained, the gate voltage-drain current characteristics were measured in the same manner as in Example 1. The result is shown in FIG.

FIG. 5 is a graph showing the gate voltage-drain current characteristics of the thin film transistor of Example 2. The thin film transistor of Example 2 had good transistor characteristics as shown in FIG. In addition, the thin film transistor of Example 2 had a mobility of 17.0 cm ² / Vs, and had a high mobility.

"Example 3"
On the gate insulating film 3 formed in the same manner as in Example 1, an oxide containing 15.0% by weight of WO ₃ , 0.5% by weight of ZnO and 84.5% by weight of In ₂ O ₃ is formed by sputtering. An oxide semiconductor layer 4 made of indium tungsten zinc and having a thickness of 10 nm was formed. Sputtering was performed with an applied power of 100 W at high frequency (RF), a gas flow rate during film formation of Ar gas 19.6 sccm and O ₂ gas 0.4 sccm.
Then, the board | substrate 1 with which the oxide semiconductor layer 4 was formed was heat-processed in air | atmosphere at 300 degreeC for 1 hour using the hotplate.

Next, a source electrode 5 and a drain electrode 6 were formed on the oxide semiconductor layer 4 in the same manner as in Example 1.
Thereafter, the substrate 1 on which the layers up to the source electrode 5 and the drain electrode 6 were formed was subjected to heat treatment at 250 ° C. for 1 hour in the air using a hot plate.

Through the above process, the thin film transistor of Example 3 was obtained. Note that the thin film transistor of Example 3 was manufactured to have a channel length of 200 μm and a channel width of 1000 μm, similarly to the thin film transistor of Example 1.
With respect to the thin film transistor of Example 3 obtained in this manner, the gate voltage-drain current characteristics were measured in the same manner as in Example 1. The result is shown in FIG.

FIG. 6 is a graph showing the gate voltage-drain current characteristics of the thin film transistor of Example 3. The thin film transistor of Example 3 had good transistor characteristics as shown in FIG. In addition, the thin film transistor of Example 3 had a mobility of 10.5 cm ² / Vs and high mobility.

Example 4
On the gate insulating film 3 formed in the same manner as in Example 1, an oxide containing 12.5 mass% WO ₃ , 0.5 mass% ZnO and 87.0 mass% In ₂ O ₃ is formed by sputtering. An oxide semiconductor layer 4 made of indium tungsten zinc and having a thickness of 10 nm was formed. Sputtering was performed with an applied power of 100 W at high frequency (RF), a gas flow rate during film formation of Ar gas 19.6 sccm and O ₂ gas 0.4 sccm.

Next, a source electrode 5 and a drain electrode 6 were formed on the oxide semiconductor layer 4 in the same manner as in Example 1.
Thereafter, the substrate 1 on which the layers up to the source electrode 5 and the drain electrode 6 were formed was subjected to heat treatment at 250 ° C. for 1 hour in the air using a hot plate.

Through the above process, the thin film transistor of Example 4 was obtained. Note that the thin film transistor of Example 4 was manufactured to have a channel length of 200 μm and a channel width of 1000 μm, similarly to the thin film transistor of Example 1.
With respect to the thin film transistor of Example 4 thus obtained, the gate voltage-drain current characteristics were measured in the same manner as in Example 1 except that 20 V was applied as the drain voltage. The result is shown in FIG.

FIG. 7 is a graph showing the gate voltage-drain current characteristics of the thin film transistor of Example 4. The thin film transistor of Example 4 had good transistor characteristics, as shown in FIG. In addition, the thin film transistor of Example 4 had a mobility of 16.1 cm ² / Vs and a high mobility.

"Example 5"
The thin film transistor 10 shown in FIG. 1 was formed and evaluated by the following method.
First, a highly doped silicon substrate was prepared as the substrate 1 that also served as the gate electrode 2, and the gate insulating film 3 made of a SiO ₂ thermal oxide film having a thickness of 100 nm was formed by thermally oxidizing the surface silicon.

After that, it was formed on the gate insulating film 3 by sputtering using indium tungsten zinc oxide containing 15.0% by weight of WO ₃ , 0.5% by weight of ZnO and 84.5% by weight of In ₂ O ₃ . An oxide semiconductor layer 4 having a thickness of 10 nm was formed. Sputtering was performed with an applied power of 100 W at high frequency (RF), a gas flow rate during film formation of Ar gas 19.6 sccm and O ₂ gas 0.4 sccm.
Then, the board | substrate 1 with which the oxide semiconductor layer 4 was formed was heat-processed in air | atmosphere at 300 degreeC for 1 hour using the hotplate.

  Next, as illustrated in FIG. 2, an electrode layer 51 to be the source electrode 5 and the drain electrode 6 was formed on the oxide semiconductor layer 4. As the electrode layer 51, a three-layer structure in which a Mo alloy layer having a thickness of 10 nm, an Al layer having a thickness of 30 nm, and a Mo alloy layer having a thickness of 10 nm were sequentially laminated from the bottom was formed. The Mo alloy layer was formed using MTD-46 (trade name: manufactured by Hitachi Metals, Ltd.). The Al layer was formed using a general material.

Next, as shown in FIG. 3, a mask 52 patterned into a predetermined shape was formed on the electrode layer 51 using a known method. Subsequently, part of the electrode layer 51 was removed by wet etching until part of the oxide semiconductor layer 4 was exposed. As an etchant, a mixed acid Al etchant manufactured by Kanto Chemical Co., Ltd. was used.
Then, the source electrode 5 and the drain electrode 6 having a predetermined shape were obtained by removing the mask 52.
Next, the substrate 1 on which the layers up to the source electrode 5 and the drain electrode 6 were formed was heat-treated in the atmosphere at 200 ° C. for 1 hour using a hot plate.

Through the above steps, the thin film transistor of Example 5 was obtained. Note that the thin film transistor of Example 5 was manufactured so as to have a channel length of 100 μm and a channel width of 1000 μm.
For the thin film transistor of Example 5 obtained in this way, the gate voltage-drain current characteristics were measured in the same manner as in Example 4. The result is shown in FIG.

FIG. 8 is a graph showing the gate voltage-drain current characteristics of the thin film transistor of Example 5. The thin film transistor of Example 5 had good transistor characteristics, as shown in FIG. In addition, the thin film transistor of Example 5 had a mobility of 11.0 cm ² / Vs and high mobility.

From the results of Examples 1 to 5, the thin film transistor of the present invention has an oxide semiconductor layer that does not contain gallium, and high mobility of 10.0 cm ² / Vs or more can be obtained. Was confirmed.

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Gate electrode, 3 ... Gate insulating film, 4 ... Oxide semiconductor layer, 5 ... Source electrode, 6 ... Drain electrode, 10 ... Thin-film transistor.

Claims (5)

A gate electrode, a gate insulating layer, an oxide semiconductor layer, a source electrode, and a drain electrode;
The thin film transistor, wherein the oxide semiconductor layer is formed of indium tungsten zinc oxide. 2. The thin film transistor according to claim 1, wherein the indium tungsten zinc oxide contains 5.0 to 15.5% by mass of WO ₃ .   The thin film transistor according to claim 1 or 2, wherein the indium tungsten zinc oxide contains 0.2 to 0.8 mass% of ZnO. The gate electrode is provided on a substrate;
The oxide semiconductor layer is provided on the gate electrode through the gate insulating layer,
The source electrode overlaps and contacts a part of the oxide semiconductor layer in plan view;
4. The drain electrode according to claim 1, wherein the drain electrode is disposed apart from the source electrode, and is in contact with a part of the oxide semiconductor layer so as to overlap in a plan view. A thin film transistor according to 1. A stacking step of forming, in this order, a gate electrode, a gate insulating layer, an oxide semiconductor layer made of indium tungsten zinc oxide, and an electrode layer over a substrate;
An etching step of forming a source electrode and a drain electrode having a predetermined shape by removing a part of the electrode layer by wet etching until the oxide semiconductor layer is exposed. Production method.

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