JP2013232598A - Thin film transistor manufacturing method and thin film transistor - Google Patents

Abstract

Provided is a method for manufacturing a thin film transistor capable of suppressing shift of a threshold voltage of the thin film transistor when a metal oxide semiconductor layer is formed by a coating method.
A step of preparing a substrate 101, a step of forming a gate electrode 102 above the substrate 101, a step of forming a gate insulating film 103 above the gate electrode 102, and above the gate insulating film 103, A step of forming a precursor thin film by applying a precursor of the metal oxide semiconductor layer 105; a step of oxidizing the precursor thin film to convert the precursor thin film into the metal oxide semiconductor layer 105; Irradiating the surface of the metal oxide semiconductor layer 105 opposite to the gate insulating film 103 with ultraviolet light at a temperature of 40 ° C. or lower and in the presence of oxygen.
[Selection] Figure 1

Description

  The present invention relates to a method for manufacturing a thin film transistor having a metal oxide semiconductor layer and a thin film transistor.

  In recent years, organic EL displays using organic EL (Electro Luminescence) have attracted attention as one of the next generation flat panel displays that replace liquid crystal displays. A plurality of thin film transistors (TFTs) are used in an active matrix display device such as an organic EL display.

  As this thin film transistor, a thin film transistor having a metal oxide semiconductor layer is known (for example, see Patent Document 1). In a conventional thin film transistor manufacturing method, the metal oxide semiconductor layer is formed by, for example, a coating method. In this coating method, first, a precursor thin film is formed on a substrate by coating a precursor of a metal oxide semiconductor layer. The precursor of the metal oxide semiconductor layer contains an organic substance as a ligand. Then, the precursor thin film is converted into a metal oxide semiconductor layer by heating and oxidizing the precursor thin film in the presence of oxygen. In addition, a part of impurities, such as organic substance contained in a precursor thin film, is thermally decomposed by this heat processing.

JP 2009-290113 A

  However, the above-described conventional thin film transistor manufacturing method has the following problems. There is a possibility that impurities such as organic substances that have not been thermally decomposed remain inside the metal oxide semiconductor layer formed by the coating method. Further, in a process (for example, a wet etching process) after the precursor thin film is converted into the metal oxide semiconductor layer, impurities may adhere to the surface of the metal oxide semiconductor layer. Since these impurities act as carrier trap sites that hinder the movement of carriers, there arises a problem that the threshold voltage of the thin film transistor is shifted.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide a method of manufacturing a thin film transistor capable of suppressing a shift in threshold voltage of the thin film transistor when a metal oxide semiconductor layer is formed by a coating method. And providing a thin film transistor.

  In order to achieve the above object, a method of manufacturing a thin film transistor according to one embodiment of the present invention is a method of manufacturing a thin film transistor having a metal oxide semiconductor layer, including a step of preparing a substrate, and a gate electrode above the substrate. Forming a gate insulating film above the gate electrode, and forming a precursor thin film by applying a precursor of the metal oxide semiconductor layer above the gate insulating film And a step of converting the precursor thin film into the metal oxide semiconductor layer by oxidizing the precursor thin film, and the metal oxide semiconductor at a temperature of 20 ° C. to 40 ° C. and in the presence of oxygen. Irradiating the surface of the layer opposite to the gate insulating film with ultraviolet light.

  In the method for producing a thin film transistor of the present invention, the precursor thin film is converted into a metal oxide semiconductor layer, and then the surface of the metal oxide semiconductor layer is irradiated with ultraviolet light in the presence of oxygen to form the metal oxide semiconductor layer. Impurities contained can be decomposed. Thus, impurities that serve as carrier trap sites can be reduced, and a shift in threshold voltage of the thin film transistor can be suppressed. Furthermore, the degree of oxidation on the surface of the metal oxide semiconductor layer can be improved by irradiating the surface of the metal oxide semiconductor layer with ultraviolet light at a temperature of 20 ° C. to 40 ° C. and in the presence of oxygen. The amount of oxygen vacancies inside the metal oxide semiconductor layer can be ensured.

FIG. 1 is a cross-sectional view showing a configuration of a thin film transistor according to an embodiment of the present invention. FIG. 2A is a cross-sectional view for explaining the method of manufacturing the thin film transistor according to the embodiment of the present invention. FIG. 2B is a cross-sectional view for explaining the method for manufacturing the thin film transistor according to the embodiment of the present invention. FIG. 2C is a cross-sectional view for explaining the method for manufacturing the thin film transistor according to the embodiment of the present invention. FIG. 2D is a cross-sectional view for explaining the method for manufacturing the thin film transistor according to the embodiment of the present invention. FIG. 2E is a cross-sectional view for describing the method for manufacturing the thin film transistor according to the embodiment of the present invention. FIG. 2F is a cross-sectional view for describing the method for manufacturing the thin film transistor according to the embodiment of the present invention. FIG. 2G is a cross-sectional view for explaining the method for manufacturing the thin film transistor according to the embodiment of the present invention. FIG. 2H is a cross-sectional view for explaining the method for manufacturing the thin film transistor according to the embodiment of the present invention. FIG. 2I is a cross-sectional view for explaining the method for manufacturing the thin film transistor according to the embodiment of the present invention. FIG. 3 is a flowchart showing a flow of a method of manufacturing a thin film transistor according to the embodiment of the present invention.

(Knowledge that became the basis of the present invention)
The present inventor has found that the following problems occur with respect to the method of manufacturing a thin film transistor described in the “Background Art” section.

  A thin film transistor having a metal oxide semiconductor layer is manufactured, for example, as follows. First, a substrate is prepared (first step), and a gate electrode is formed above the substrate (second step). Subsequently, a gate insulating film is formed above the gate electrode (third step). Thereafter, a source electrode and a drain electrode are formed above the gate insulating film (fourth step). Thereafter, a precursor thin film is formed by applying a precursor of the metal oxide semiconductor layer above the gate insulating film (fifth step). The precursor of the metal oxide semiconductor layer contains an organic substance as a ligand.

  Then, the precursor thin film is oxidized by heating the precursor thin film in the presence of oxygen to convert the precursor thin film into a metal oxide semiconductor layer (sixth step). In the sixth step, part of impurities such as organic substances contained in the precursor thin film is thermally decomposed. Note that moderate oxygen vacancies are necessary inside the metal oxide semiconductor layer to allow electricity to flow. Therefore, in the sixth step, the metal oxide semiconductor layer is not completely oxidized in order to generate appropriate oxygen vacancies inside the metal oxide semiconductor layer.

  However, the above-described method for manufacturing a thin film transistor has the following problems. In the sixth step, some impurities such as organic substances contained in the precursor thin film may remain inside the metal oxide semiconductor layer without being thermally decomposed. Furthermore, there is a possibility that impurities may adhere to the surface of the metal oxide semiconductor layer in a process (for example, a wet etching process) after the sixth process. Since these impurities act as carrier trap sites that hinder the movement of carriers, there arises a problem that the threshold voltage of the thin film transistor is shifted.

  In order to prevent the threshold voltage from shifting, a method of setting the temperature of the heat treatment in the sixth step high (for example, 350 to 400 ° C.) can be considered. Thereby, impurities, such as organic substance contained in a precursor thin film, can fully be thermally decomposed. However, in such a method, there is a problem that the degree of oxidation inside the metal oxide semiconductor layer increases and the amount of oxygen vacancies inside the metal oxide semiconductor layer decreases. Furthermore, when indium (In) is contained in the metal oxide semiconductor layer, indium is crystallized by high-temperature heat by setting the temperature of the heat treatment in the sixth step high. When indium is crystallized, there arises a problem that the thin film transistor cannot be turned off.

  In order to solve such a problem, a manufacturing method of a thin film transistor according to one embodiment of the present invention is a manufacturing method of a thin film transistor having a metal oxide semiconductor layer, and includes a step of preparing a substrate, and a step above the substrate. Forming a gate electrode; forming a gate insulating film above the gate electrode; and forming a precursor thin film by applying a precursor of the metal oxide semiconductor layer above the gate insulating film The step of converting the precursor thin film into the metal oxide semiconductor layer by oxidizing the precursor thin film, and the metal oxidation at a temperature of 20 ° C. to 40 ° C. and in the presence of oxygen. Irradiating the surface of the physical semiconductor layer opposite to the gate insulating film with ultraviolet light.

  According to this aspect, the impurity contained in the metal oxide semiconductor layer can be decomposed by irradiating the surface of the metal oxide semiconductor layer with ultraviolet light in the presence of oxygen. Thus, impurities that serve as carrier trap sites can be reduced, and a shift in threshold voltage of the thin film transistor can be suppressed. Furthermore, the degree of oxidation on the surface of the metal oxide semiconductor layer can be improved by irradiating the surface of the metal oxide semiconductor layer with ultraviolet light at a temperature of 20 ° C. to 40 ° C. and in the presence of oxygen. The amount of oxygen vacancies inside the metal oxide semiconductor layer can be ensured.

  For example, in the method for manufacturing a thin film transistor according to one embodiment of the present invention, in the step of irradiating with ultraviolet light, the oxygen-containing concentration in the surface of the metal oxide semiconductor layer may be oxygen-containing in the metal oxide semiconductor layer. You may comprise so that the said ultraviolet light may be irradiated to the said surface of the said metal oxide semiconductor layer so that it may become higher than a density | concentration.

  According to this aspect, the degree of oxidation on the surface of the metal oxide semiconductor layer can be improved. Thereby, for example, in the step after the step of irradiating ultraviolet light, the surface of the metal oxide semiconductor layer can be prevented from reacting with impurities and the like, and the surface of the metal oxide semiconductor layer can be stabilized. it can.

  For example, in the method for manufacturing a thin film transistor according to one embodiment of the present invention, in the step of irradiating the ultraviolet light, the surface of the metal oxide semiconductor layer is irradiated with the ultraviolet light for a time of 1 minute to 20 minutes. You may comprise.

  According to this aspect, it is possible to effectively irradiate the surface of the metal oxide semiconductor layer with ultraviolet light.

  For example, in the method for manufacturing a thin film transistor according to one embodiment of the present invention, in the step of forming the precursor thin film, the precursor of the metal oxide semiconductor layer is configured to include an organic substance as a ligand. May be.

  According to this aspect, even when the precursor of the metal oxide semiconductor layer contains an organic substance as a ligand, the organic substance is removed by irradiating the surface of the metal oxide semiconductor layer with ultraviolet light. Can be disassembled.

  For example, in the method for manufacturing a thin film transistor according to one embodiment of the present invention, in the step of converting the precursor thin film into the metal oxide semiconductor layer, the precursor thin film is heated at a temperature of 240 ° C. or higher and 350 ° C. or lower. You may comprise.

  According to this aspect, the precursor thin film can be effectively oxidized.

  A thin film transistor according to one embodiment of the present invention includes a substrate, a gate electrode formed over the substrate, a gate insulating film formed over the gate electrode, and a metal formed over the gate insulating film. An oxide semiconductor layer; a protective layer formed above the metal oxide semiconductor layer for protecting the metal oxide semiconductor layer; and a source electrode electrically connected to the metal oxide semiconductor layer; A drain electrode electrically connected to the metal oxide semiconductor layer, and the oxygen-containing concentration on the surface of the metal oxide semiconductor layer opposite to the gate insulating film is the concentration of the metal oxide semiconductor layer It is higher than the oxygen-containing concentration inside.

  According to this aspect, the degree of oxidation on the surface of the metal oxide semiconductor layer can be improved. Accordingly, in the manufacturing process of the thin film transistor, the surface of the metal oxide semiconductor layer can be prevented from reacting with impurities and the like, and the surface of the metal oxide semiconductor layer can be stabilized.

(Embodiment)
Hereinafter, a thin film transistor manufacturing method and a thin film transistor according to an embodiment of the present invention will be described with reference to the drawings. Note that each of the embodiments described below shows a specific example of the present invention. Numerical values, shapes, materials, components, arrangement positions and connection forms of components, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept are described as optional constituent elements.

  FIG. 1 is a cross-sectional view showing a configuration of a thin film transistor according to an embodiment of the present invention. A thin film transistor 10 illustrated in FIG. 1 is a bottom-gate thin film transistor. The thin film transistor 10 includes a substrate 101, a gate electrode 102, a gate insulating film 103, a source electrode 104S, a drain electrode 104D, a metal oxide semiconductor layer 105, and a protective layer 106.

The substrate 101 is made of, for example, a glass material such as quartz glass, non-alkali glass and high heat resistant glass, or a resin material such as polyimide. Note that an undercoat layer (not shown) for preventing impurities such as sodium and phosphorus contained in the substrate 101 from entering the metal oxide semiconductor layer 105 can be formed over the substrate 101. The undercoat layer is composed of, for example, a silicon nitride film (SiN _x ), silicon oxide (SiO _y ), silicon oxynitride film (SiO _y N _x ), or the like.

  The gate electrode 102 is patterned in a predetermined shape on the substrate 101. The gate electrode 102 can have a single layer structure or a multilayer structure such as a conductive material and an alloy thereof, for example, molybdenum (Mo), aluminum (Al), copper (Cu), tungsten (W), titanium (Ti) ), Chromium (Cr), molybdenum tungsten (MoW), and other metal materials, as well as oxide conductive materials such as indium tin oxide (ITO) and indium zinc oxide (IZO).

The gate insulating film 103 is formed so as to cover the gate electrode 102. The gate insulating film 103 is made of, for example, aluminum oxide (Al ₂ O ₃ ) or the like.

  The source electrode 104S and the drain electrode 104D are each formed on the gate insulating film 103. The source electrode 104S and the drain electrode 104D are arranged with a space therebetween and facing each other. The source electrode 104S and the drain electrode 104D can have a single layer structure or a multilayer structure such as a conductive material and an alloy thereof, for example, aluminum (Al), molybdenum (Mo), tungsten (W), copper (Cu). In addition to metal materials such as titanium (Ti), chromium (Cr) and molybdenum tungsten (MoW), it is composed of oxide conductive materials such as indium tin oxide (ITO) and indium zinc oxide (IZO). ing.

The metal oxide semiconductor layer 105 is formed above the gate insulating film 103. The metal oxide semiconductor layer 105 has a channel region. Note that the channel region is a region in which the movement of carriers is controlled by the voltage of the gate electrode 102. The above-described source electrode 104S and drain electrode 104D are electrically connected to the metal oxide semiconductor layer 105, respectively. The metal oxide semiconductor layer 105 is made of a metal oxide such as zinc oxide (ZnO), tin oxide (SnO ₂ ), indium oxide (In ₂ O ₃ ), gallium oxide (Ga ₂ O ₃ ), for example. Yes. The metal oxide semiconductor layer 105 may be composed of a plurality of types of metal oxides, for example, zinc oxide (ZnO), indium oxide (In ₂ O ₃ ), and gallium oxide (Ga ₂ O ₃ ). InGaO ₃ (ZnO) ₅ composed of Note that the oxygen-containing concentration on the surface of the metal oxide semiconductor layer 105 opposite to the gate insulating film 103 is higher than the oxygen-containing concentration inside the metal oxide semiconductor layer 105.

The protective layer 106 is formed so as to cover the metal oxide semiconductor layer 105. The protective layer 106 is a layer for protecting the metal oxide semiconductor layer 105, and is made of, for example, silicon oxide (SiO ₂ ).

  Next, a method for manufacturing the thin film transistor 10 according to the present embodiment will be described. 2A to 2I are cross-sectional views for explaining a method of manufacturing a thin film transistor according to the embodiment of the present invention. FIG. 3 is a flowchart showing a flow of a method of manufacturing a thin film transistor according to the embodiment of the present invention.

  First, as shown in FIG. 2A, a substrate 101 made of a glass material, a resin material, or the like is prepared (first step) (S1). In addition, before performing the 2nd process mentioned later, you may form the undercoat layer mentioned above on the board | substrate 101 by plasma CVD (Chemical Vapor Deposition).

  Subsequently, as shown in FIG. 2B, a gate electrode 102 is formed on the substrate 101 (second step) (S2). In this second step, first, a gate metal film made of the material of the gate electrode 102 is formed on the substrate 101 by sputtering. Thereafter, the gate metal film is patterned by photolithography and wet etching to form a gate electrode 102 having a predetermined shape.

  Thereafter, as shown in FIG. 2C, a gate insulating film 103 is formed so as to cover the gate electrode 102 (third step) (S3). In the third step, first, a gate insulating material film made of the material of the gate insulating film 103 is formed on the gate electrode 102 by sputtering. After that, the gate insulating material film 103 is patterned by photolithography and wet etching to form a gate insulating film 103 having a predetermined shape.

  Thereafter, as shown in FIG. 2D, a source electrode 104S and a drain electrode 104D are formed on the gate insulating film 103 (fourth step) (S4). In the fourth step, first, a source / drain metal film made of materials of the source electrode 104S and the drain electrode 104D is formed on the gate insulating film 103 by sputtering. Thereafter, the source / drain metal film is patterned by a photolithography method and a wet etching method to form a source electrode 104S and a drain electrode 104D having a predetermined shape.

  Thereafter, the metal oxide semiconductor layer 105 is formed as follows. First, as shown in FIG. 2E, a precursor of the metal oxide semiconductor layer 105 is applied to the surfaces of the substrate 101, the gate insulating film 103, the source electrode 104S, and the drain electrode 104D so that the metal oxide semiconductor layer 105 is formed above the gate insulating film 103. The precursor thin film 105a is formed (fifth step) (S5). As a method for applying the precursor of the metal oxide semiconductor layer 105, for example, a coating method such as a spin coating method, a spray coating method, or a dip coating method can be used.

  The precursor of the metal oxide semiconductor layer 105 is constituted by, for example, a solution in which a metal salt is dissolved in a solvent. Examples of the metal salt include metal nitrates, sulfates, phosphates, carbonates, and carboxylates such as acetates and propionates. As a metal constituting the metal salt, for example, zinc (Zn), tin (Sn), indium (In), gallium (Ga), aluminum (Al), or the like can be used. For example, when nitrate is used as the metal salt, the metal salt is zinc nitrate, tin nitrate, indium nitrate, gallium nitrate, aluminum nitrate, or the like. In addition to the metal salts described above, the precursor of the metal oxide semiconductor layer 105 includes an organic substance as a ligand (for example, acetylacetonate, succinate, cinnamate, and the like), and a precursor that includes an alkoxide (for example, Methoxy ethoxide, ethoxy ethoxide, isopropoxide, etc.) can also be used. As the solvent, for example, water can be used, and in addition to water, alcohols such as ethanol, propanol and ethylene glycol; ethers such as trahydrofuran and dioxane, esters such as methyl acetate and ethyl acetate; Ketones such as acetone, methyl ethyl ketone, and cyclohexanone; glycol ethers such as diethylene glycol monomethyl ether can be used.

  Thereafter, the precursor thin film 105a is heated in the presence of water vapor and oxygen. At this time, the atmospheric temperature of the precursor thin film 105a is raised from room temperature to a predetermined temperature (240 ° C. or higher and 350 ° C. or lower). Subsequently, the precursor thin film 105a is heated for about several hours in the presence of oxygen. At this time, the atmospheric temperature of the precursor thin film 105a is kept substantially constant at the predetermined temperature. Thus, the precursor thin film 105a is oxidized by heat-treating the precursor thin film 105a in the presence of oxygen. Thereby, as shown in FIG. 2F, the precursor thin film 105a is converted into the metal oxide semiconductor layer 105 '(sixth step) (S6). In the sixth step, the precursor thin film 105a is converted into the metal oxide semiconductor layer 105 ′, and part of impurities such as organic substances contained in the precursor thin film 105a is thermally decomposed and further included in the precursor thin film 105a. The solvent is volatilized. Note that in the sixth step, the metal oxide semiconductor layer 105 ′ is not completely oxidized in order to generate appropriate oxygen vacancies inside the metal oxide semiconductor layer 105 ′.

  Note that the temperature of the heat treatment in the sixth step is 240 ° C. or higher and 350 ° C. or lower. When the heat treatment temperature is lower than 240 ° C., impurities such as organic substances contained in the precursor thin film 105a cannot be sufficiently pyrolyzed. When the temperature of the heat treatment exceeds 350 ° C., the substrate 101 may be deformed by heat.

  Thereafter, as shown in FIG. 2G, the metal oxide semiconductor layer 105 ′ is patterned by photolithography and wet etching to form a metal oxide semiconductor layer 105 having a predetermined shape (seventh step) (S7). .

  Thereafter, as shown in FIG. 2H, the surface of the metal oxide semiconductor layer 105 is irradiated with ultraviolet light at a temperature of 20 ° C. to 40 ° C. and in the presence of oxygen (eighth step) (S8). As an ultraviolet light source, for example, an excimer lamp and a mercury lamp can be used. When an excimer lamp is used as the ultraviolet light source, for example, the wavelength of the ultraviolet light is 172 nm and the energy of the ultraviolet light is 7.2 eV. When a mercury lamp is used as the ultraviolet light source, for example, the wavelength of the ultraviolet light is 185 nm (or 254 nm), and the energy of the ultraviolet light is 6.7 eV (or 4.9 eV).

  In the eighth step, by irradiating the surface of the metal oxide semiconductor layer 105 with ultraviolet light, for example, impurities such as organic substances adhering to the surface of the metal oxide semiconductor layer 105 in the wet etching step in the seventh step are changed to ultraviolet light. It can be decomposed by the action of In addition, part of the ultraviolet light applied to the surface of the metal oxide semiconductor layer 105 penetrates into the metal oxide semiconductor layer 105. Accordingly, impurities such as organic substances remaining in the metal oxide semiconductor layer 105 without being thermally decomposed in the sixth step can be decomposed by the action of ultraviolet light.

  In the eighth step, the surface of the metal oxide semiconductor layer 105 is irradiated with ultraviolet light at a temperature of 20 ° C. or higher and 40 ° C. or lower and in the presence of oxygen, whereby active oxygen is formed in the vicinity of the surface of the metal oxide semiconductor layer 105. (Ozone and oxygen radicals) are generated. By the action of this active oxygen, the degree of oxidation on the surface of the metal oxide semiconductor layer 105 can be improved. Accordingly, the oxygen-containing concentration at the surface of the metal oxide semiconductor layer 105 is higher than the oxygen-containing concentration inside the metal oxide semiconductor layer 105.

  Note that, by setting the atmospheric temperature when irradiating with ultraviolet light to 20 ° C. or more and 40 ° C. or less, the degree of oxidation on the surface of the metal oxide semiconductor layer 105 is increased, while the inside of the metal oxide semiconductor layer 105 is increased. The degree of oxidation does not change. Thereby, the amount of oxygen vacancies in the metal oxide semiconductor layer 105 can be secured. When the ambient temperature at the time of irradiation with ultraviolet light is lower than 20 ° C., the degree of oxidation on the surface of the metal oxide semiconductor layer 105 cannot be sufficiently increased. When the atmospheric temperature during irradiation with ultraviolet light exceeds 40 ° C., the degree of oxidation inside the metal oxide semiconductor layer 105 increases, and the amount of oxygen vacancies inside the metal oxide semiconductor layer 105 decreases. . In the case where indium (In) is contained in the metal oxide semiconductor layer 105, the atmosphere temperature during irradiation with ultraviolet light is set to 20 ° C. or higher and 40 ° C. or lower, so that indium is prevented from being crystallized. can do.

  Note that the time for irradiating the surface of the metal oxide semiconductor layer 105 with ultraviolet light is, for example, not less than 1 minute and not more than 20 minutes. When the irradiation time of ultraviolet light is shorter than 1 minute, impurities such as organic substances contained in the metal oxide semiconductor layer 105 cannot be sufficiently thermally decomposed. When the irradiation time of ultraviolet light is longer than 20 minutes, the degree of oxidation inside the metal oxide semiconductor layer 105 increases, and the amount of oxygen vacancies inside the metal oxide semiconductor layer 105 decreases.

  Thereafter, as shown in FIG. 2I, a protective layer 106 is formed so as to cover the metal oxide semiconductor layer 105 (9th step) (S9). In the ninth step, first, a protective film made of the material of the protective layer 106 is formed on the metal oxide semiconductor layer 105 by sputtering. Thereafter, the protective film 106 having a predetermined shape is formed by patterning the protective film by a photolithography method and a wet etching method.

  As described above, the thin film transistor 10 according to this embodiment is manufactured.

  In the method for manufacturing the thin film transistor 10 according to this embodiment, impurities such as organic substances contained in the metal oxide semiconductor layer 105 are decomposed by irradiating the surface of the metal oxide semiconductor layer 105 with ultraviolet light in the eighth step. be able to. Thereby, since impurities that serve as carrier trap sites can be reduced, the threshold voltage of the thin film transistor 10 can be prevented from shifting.

  In addition, the degree of oxidation on the surface of the metal oxide semiconductor layer 105 can be improved by irradiating the surface of the metal oxide semiconductor layer 105 with ultraviolet light in the eighth step. Accordingly, the surface of the metal oxide semiconductor layer 105 can be prevented from reacting with impurities or the like in the step after the eighth step, and the surface of the metal oxide semiconductor layer 105 can be stabilized.

  As described above, the method for manufacturing a thin film transistor and the thin film transistor according to one or more aspects of the present invention have been described based on the embodiment, but the present invention is not limited to this embodiment. Unless it deviates from the gist of the present invention, one or more of the present invention may be applied to various modifications that can be conceived by those skilled in the art, or forms constructed by combining components in different embodiments. It may be included within the scope of the embodiments.

  In the above embodiment, the source electrode and the drain electrode are formed over the gate electrode. However, for example, the source electrode and the drain electrode may be formed over the metal oxide semiconductor layer, and the arrangement positions thereof may be set as appropriate. it can.

  The thin-film transistor manufacturing method and the thin-film transistor according to the present invention can be widely used for display devices such as a television set, a personal computer, a mobile phone, and other various electric devices having thin-film transistors.

DESCRIPTION OF SYMBOLS 10 Thin-film transistor 101 Substrate 102 Gate electrode 103 Gate insulating film 104S Source electrode 104D Drain electrode 105, 105 'Metal oxide semiconductor layer 105a Precursor thin film 106 Protective layer

Claims (6)

A method of manufacturing a thin film transistor having a metal oxide semiconductor layer,
Preparing a substrate;
Forming a gate electrode above the substrate;
Forming a gate insulating film above the gate electrode;
Forming a precursor thin film by applying a precursor of the metal oxide semiconductor layer above the gate insulating film;
Converting the precursor thin film into the metal oxide semiconductor layer by oxidizing the precursor thin film;
Irradiating the surface of the metal oxide semiconductor layer opposite to the gate insulating film with ultraviolet light at a temperature of 20 ° C. to 40 ° C. and in the presence of oxygen. In the step of irradiating the ultraviolet light, the metal oxide semiconductor layer is formed so that an oxygen-containing concentration at the surface of the metal oxide semiconductor layer is higher than an oxygen-containing concentration inside the metal oxide semiconductor layer. The method for manufacturing a thin film transistor according to claim 1, wherein the surface is irradiated with the ultraviolet light. 3. The method for manufacturing a thin film transistor according to claim 1, wherein, in the step of irradiating with ultraviolet light, the surface of the metal oxide semiconductor layer is irradiated with the ultraviolet light for a time of 1 minute to 20 minutes. The method for producing a thin film transistor according to claim 1, wherein in the step of forming the precursor thin film, the precursor of the metal oxide semiconductor layer includes an organic substance as a ligand. 5. The thin film transistor according to claim 1, wherein the precursor thin film is heated at a temperature of 240 ° C. or higher and 350 ° C. or lower in the step of converting the precursor thin film into the metal oxide semiconductor layer. Method. A substrate,
A gate electrode formed above the substrate;
A gate insulating film formed above the gate electrode;
A metal oxide semiconductor layer formed above the gate insulating film;
A protective layer formed above the metal oxide semiconductor layer for protecting the metal oxide semiconductor layer;
A source electrode electrically connected to the metal oxide semiconductor layer;
A drain electrode electrically connected to the metal oxide semiconductor layer,
The oxygen content concentration in the surface on the opposite side to the said gate insulating film of the said metal oxide semiconductor layer is higher than the oxygen content concentration in the inside of the said metal oxide semiconductor layer.

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