JP2016063053A - Thin film transistor and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin film transistor which achieves high bias stress stability and low density of states due to oxygen defect; and provide a manufacturing method of the thin film transistor.SOLUTION: In a thin film transistor having a laminate composed of a gate insulation layer 4, a metal oxide semiconductor layer 7 containing indium, a buffer layer 8 and a protection layer 9 which is formed by coating a protection layer formation composition which contains polymer including a hydroxyl group in a repeating unit and contains a solvent, the buffer layer 8 is formed to completely cover the metal oxide semiconductor layer 7 and subsequently the protection layer 9 is formed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thin film transistor used for an active matrix substrate of a flat panel display such as a liquid crystal or an organic EL, and a thin film transistor technique characterized by its manufacturing method.

  There is a demand for improving the bias stress stability (reliability) of a thin film transistor using a metal oxide semiconductor. One of the causes of deterioration in reliability is the adsorption of atmospheric components such as oxygen and water onto the semiconductor layer. Non-Patent Document 1 evaluates the bias stress stability of a transistor by forming a fluororesin (Cytop) on a semiconductor layer as a semiconductor protective film for the purpose of improving the reliability of the transistor. However, the shift amount of the threshold voltage is 3 V, which is a large value despite using IGZO formed by a stable sputtering method. In the fluororesin single layer, it is insufficient to suppress the bias stress stability, and further improvement is necessary.

  Patent Document 1 describes that a fluororesin or polyvinyl alcohol can be used as a semiconductor protective film, and that the protective film may have a laminated structure. However, Patent Document 1 is an invention that simplifies the manufacturing process by patterning a semiconductor layer using a protective film as a mask, and does not focus on improving bias stress stability. That is, there is no suggestion that bias stress stability can be improved by forming the protective film in a laminated structure.

  As described above, the laminated structure of the protective film and the manufacturing process of the thin film transistor that can improve the bias stress stability have not yet been clarified.

  In addition, in the case where the thin film transistor is exposed to a vacuum condition for a long time, the oxygen defect induced in the metal oxide semiconductor layer is eliminated, so that there is a problem that the state density distribution of the thin film transistor greatly changes immediately after the production.

International Publication No. 2011/122205 Pamphlet

Sung-Hwan Choi et al, Electron Device Letters IEEE, Vol.33, No.3, P.381-383 (2012)

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a thin film transistor having high bias stress stability and low state density due to oxygen defects, and a method for manufacturing the same.

  As a result of repeated studies, it was found that a thin film transistor having a specific manufacturing process has a particularly excellent effect.

  That is, a manufacturing method of a thin film transistor which is an embodiment of the present invention for solving the above problems includes a gate insulating layer, a metal oxide semiconductor layer containing indium, a buffer layer, a polymer containing a hydroxyl group in a repeating unit, and a solvent. In a thin film transistor having a laminate composed of a protective layer formed by applying a protective layer forming composition, the buffer layer is formed so as to completely cover the metal oxide semiconductor layer, and then the protective layer is formed. It is characterized by doing.

  Moreover, it is preferable to form a layer containing fluorocarbon after applying the protective layer forming composition to form the protective layer.

  In addition, it is preferable that the metal oxide semiconductor layer containing indium is subjected to patterning treatment before the buffer layer is formed.

  The metal oxide semiconductor layer containing indium is preferably formed by coating.

  Moreover, it is preferable that the said polymer containing a hydroxyl group in a repeating unit is a polymer containing the structural unit represented by following General formula (1).

（式中、Ｒは、それぞれ単独に、水素原子、又は炭素原子数１〜１２のアルキル基、Ｘは、単結合、カルボニル基、スルホニル基、炭素原子数１〜１２の有機基からなる群より選択される１種である。）

(In the formula, each R is independently a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and X is a single bond, a carbonyl group, a sulfonyl group, or an organic group having 1 to 12 carbon atoms. One type selected.)

  Moreover, it is preferable that the polymer containing a hydroxyl group in a repeating unit is a polymer obtained by polymerizing a polymerizable monomer containing at least one hydroxyl group-containing polymerizable vinyl monomer.

  Moreover, it is preferable that the polymer containing a hydroxyl group in a repeating unit is a polymer obtained by polymerizing a polymerizable monomer containing a polymerizable vinyl monomer having a group that generates a hydroxyl group by at least one kind of hydrolysis.

  Moreover, it is preferable that the said protective layer forming composition is a resin forming composition containing 10 mass% or more of water.

  The protective layer formed by applying the protective layer forming composition is preferably a protective layer having a relative dielectric constant of 3.0 or more.

  The buffer layer preferably contains carbon fluoride.

  Moreover, it is preferable that the said buffer layer is a layer containing a fluororesin.

  The buffer layer is preferably a resin layer having a relative dielectric constant of 2.9 or less.

  A thin film transistor according to another aspect of the present invention for solving the above-described problems is manufactured by any one of the manufacturing methods described above.

Further, the _Vth shift due to positive bias stress is preferably less than 2V.

  By patterning a metal oxide semiconductor and then using the method for manufacturing a thin film transistor of the present invention, in which a buffer layer and a protective layer are formed, a thin film transistor having high bias stress stability and low stability due to oxygen defects is obtained. It can be manufactured. As a result, a flat panel display with little image quality degradation can be provided.

Sectional drawing which shows the structural example of the thin-film transistor 1, 1A, 1B which concerns on this embodiment. Sectional drawing which shows the structural example of 1 C of thin-film transistors which concern on this embodiment. Sectional drawing which shows the structural example of thin-film transistor 1D which concerns on this embodiment.

(Thin film transistor)
The thin film transistor 1 of the present invention includes a substrate 2, a gate electrode 3 formed on the substrate 2, a gate insulating layer 4 formed on the gate electrode 3, and a gate insulating layer 4 so as to be insulated from the gate electrode 3. A source electrode 5 and a drain electrode 6 to be stacked, a metal oxide semiconductor layer (hereinafter sometimes referred to simply as “semiconductor layer”) 7 formed on the source electrode 5 and the drain electrode 6, and a buffer layer 8 And a protective layer 9. That is, in the thin film transistor 1 shown in FIG. 1A, the source electrode 5 and the drain electrode 6 are disposed opposite to each other on the gate insulating layer 4, and the semiconductor layer 7 of the present invention is so covered as to cover the source electrode 5 and the drain electrode 6. Is formed. Note that, as in the thin film transistor 1A illustrated in FIG. 1B, in order to improve the bias stress stability of the transistor, it is preferable that the protective layer 9 includes a layer 10 containing fluorocarbon.

  On the other hand, the stacking order of the source electrode 5 and the drain electrode 6 and the semiconductor layer 7 may be reversed as shown in FIG. That is, in the thin film transistor 1B shown in FIG. 1C, the semiconductor layer 7 is formed on the gate insulating layer 4, and the source electrode 5 and the drain electrode 6 are formed thereon.

  In any transistor, the buffer layer 8 is formed so as to completely cover the semiconductor layer 7, that is, to completely cover a region functioning as the semiconductor layer 7. Also in the drawing, only the buffer layer 8 is formed on the upper surface (surface opposite to the substrate 2) of the semiconductor layer 7 except for the portion where the source electrode 5 and the drain electrode 6 are stacked. .

(Thin Film Transistor Manufacturing Method)
As the substrate 2, a silicon substrate, a metal substrate, a plastic substrate, a gallium substrate, a transparent electrode substrate, an organic thin film substrate, a glass substrate, or the like can be used.

  The electrode material (the material of the gate electrode 3, the source electrode 5, and the drain electrode 6) is, for example, a metal such as aluminum, gold, silver, copper, molybdenum, titanium, platinum, tungsten, ITO, IZO, carbon black, fullerenes. Inorganic materials such as carbon nanotubes, organic π-conjugated polymers such as polythiophene, polyaniline, polypyrrole, polyfluorene, and derivatives thereof can be used. These electrode materials may be used alone or in combination of two or more. Different electrode materials may be used for each of the gate electrode 3, the source electrode 5, and the drain electrode 6. When the substrate to be used has the function of the gate electrode 3, the configuration of the gate electrode 3 can be omitted.

  The gate insulating layer 4 of the present invention is formed on the substrate 2 and the gate electrode 3. For example, an inorganic insulating film such as silicon oxide, silicon nitride, aluminum oxide, hafnium oxide, yttrium oxide, or an organic insulating film such as polyimide, polymethyl methacrylate, polyvinylphenol, or benzocyclobutene can be used. These gate insulating layers may be used individually by 1 type, and may use 2 or more types together. The gate insulating layer of the present invention is not limited to these.

  As a method for forming the gate insulating layer 4, a sputtering method, a vacuum deposition method, or the like can be used. However, in order to simplify the manufacturing method, various coating methods such as a spray coating method, a printing method, and an ink jet method are used. Also good. When a silicon substrate is used as the substrate, the gate insulating layer can also be formed by thermal oxidation.

  The semiconductor layer 7 of the present invention is an oxide semiconductor material containing indium. The metals may be used alone or in combination. The metals that can be used in combination with indium include Li, Be, B, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn , Ga, Ge, Rb, Sr, Y, Zr, Nb, Mo, Cd, Ir, Sn, Sb, Cs, Ba, La, Hf, Ta, W, Tl, Pb, Bi, Ce, Pr, Nd, Pm , Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and Mg, Al, Zn, Ga, Sn, and W are particularly preferable.

  From these combinations, indium gallium zinc oxide (InGaZnOx), indium gallium oxide (InGaOx), indium tin zinc oxide (InSnZnOx), gallium zinc oxide (GaZnOx), indium tin oxide (InSnOx), indium zinc oxide (InZnOx), oxide A metal oxide semiconductor layer such as indium aluminum (InAlOx), indium magnesium oxide (InMgOx), or indium aluminum zinc oxide (InAlZnOx) can be formed. In all cases, x> 0.

  In general, when a semiconductor compound is used for a field effect transistor or the like, the crystallinity is preferably amorphous from the viewpoint of electrical characteristics, physical strength, and the like. Therefore, if an amorphous metal oxide semiconductor layer is formed using a desired inorganic metal salt as described above, a semiconductor device such as a field effect transistor having excellent characteristics can be manufactured. Note that in this specification, amorphous means a material in which a diffraction peak is not detected by X-ray diffraction (XRD) measurement, or a material having a weak diffraction peak even if a diffraction peak is detected.

  As a method for forming the semiconductor layer 7 containing indium, a coating method can be used in addition to a vacuum method such as a CVD method, a sputtering method, a pulse laser deposition method, or a vacuum evaporation method. Examples of the coating method include a method using a precursor solution containing an organometallic compound and a metal salt, a method using a dispersion solution in which fine particles of metal oxide are dispersed in a solution, and a method using a solution obtained by mixing these. is there.

  As the organometallic compound, metal alkoxides such as methoxide, ethoxide, isopropoxide, organometallic complexes, and the like can be used.

  As the metal salt, an organic metal salt, an inorganic metal salt, or the like can be used.

  As a solvent used for the precursor solution and the dispersion, water and alcohols are preferable.

  Examples of alcohols include methanol, n-propanol, isopropanol, n-butanol, 2-methyl-1-propanol, tert-butanol, 4-methyl-2-pentanol, and propylene glycol monomethyl ether.

  As the coating method, spin coating, dip coating, screen printing, roll coating, ink jet coating, die coating, transfer printing, spraying, slit coating, and the like can be used.

  In the present invention, a step of baking the precursor thin film at 150 ° C. to 400 ° C. is then performed. Although baking time is not specifically limited, For example, they are 3 minutes-24 hours.

  In the firing step, the method for heating the precursor composition is not limited, and a highly versatile and inexpensive heating device such as a hot plate, an IR furnace, or an oven can be used. A relatively expensive apparatus such as an atmospheric pressure plasma apparatus or a microwave heating apparatus may be used. The atmosphere in which the firing step is performed can be performed not only in an oxidizing atmosphere such as oxygen and oxygen, but also in an inert gas such as nitrogen, helium, and argon.

  The method for forming a metal oxide semiconductor layer by the above-described coating and baking makes it easy to increase the area with a simple configuration and has high mobility as compared with the case of using a vacuum film forming apparatus such as a sputtering method. The semiconductor layer 7 having excellent density can be formed.

  Although the thickness of the semiconductor layer 7 is not specifically limited, For example, it can be set as 1-100 nm. Preferably, it is 3-15 nm.

  The semiconductor layer 7 containing indium has, for example, a source electrode 5 and a drain electrode 6 like a thin film transistor 1C shown in FIG. 2A which is a cross-sectional view and FIG. 2B which is a cross-sectional view along the line AA ′. It suffices if the film is formed only during this period. That is, no other semiconductor layer is necessary, and it is preferable to pattern the semiconductor layer before forming the buffer layer 8.

  2A to 2B, the gate electrode 3 is not shown, but this uses the substrate 2a having the function of the gate electrode 3, and the configuration of the gate electrode 3 is omitted in the thin film transistor 1C. Because.

  As a method of patterning the semiconductor layer 7, there is a method of etching with hydrochloric acid or the like using a photoresist (for example, OPFR-800 manufactured by TOK) as a mask. The unnecessary photoresist is removed by an organic solvent or ashing.

The electron carrier concentration of the semiconductor layer 7 containing indium thus formed is preferably 10 ¹² to 10 ¹⁸ / cm ³ . The electron carrier concentration can be adjusted by controlling the composition (constituent element), composition ratio, production conditions and the like of the metal oxide.

  Note that in the case where the semiconductor layer 7 is not patterned, it is necessary to form the semiconductor layer 7 up to a region sufficiently separated from the transistor by using a substrate sufficiently larger than the transistor. The buffer layer 8 and the protective layer 9 formed on the semiconductor layer also need to be formed up to the same region as the semiconductor layer 7. Cross-sectional views of such a thin film transistor 1D are shown in FIGS. Also in the thin film transistor 1D, only the buffer layer 8 is formed on the upper surface in the stacking direction of the semiconductor layer 7 except for the portion where the source electrode 5 and the drain electrode 6 are stacked, and the buffer layer 8 completely covers the semiconductor layer 7. Is formed.

  3A and 3B, the thin film transistor 1D is configured using the substrate 2a having the function of the gate electrode 3, and the configuration of the gate electrode 3 is not shown.

  By depositing each layer to a region far enough away from the transistor, it is possible to prevent the intrusion of oxygen and water from the side of the semiconductor layer, and the bias stress stability due to adsorption of oxygen and water to the semiconductor layer can be prevented. Deterioration can be suppressed. As a specific example of the sufficiently separated region here, it is 5 mm from the outer periphery of the transistor. If the distance is 5 mm or more, the effect of the present invention can be obtained. However, since characteristics other than bias stress stability such as parasitic capacitance are improved, it is better to fabricate a transistor by a method of patterning a semiconductor. In this case, it is easy to completely cover the semiconductor layer 7. That is, it is not necessary to form the buffer layer 8 and the protective layer 9 in a sufficiently distant area.

The buffer layer 8 is formed so as to completely cover the semiconductor layer 7. The buffer layer 8 can mitigate the adverse effect of the protective layer 9 on the semiconductor layer 7. As the buffer layer 8, an inorganic oxide film such as SiO ₂ , SiN, or Al ₂ O _{3 that} can be formed by coating or a vacuum method, or an organic insulating film that can be formed by a coating method can be used. Among these, the coating method is preferable because the energy cost during film formation is low. When an inorganic layer is formed by a coating method, a polar group having a large polarity such as silanol tends to remain in the layer, which may adversely affect the metal oxide semiconductor. Therefore, the buffer layer is preferably an organic layer, and the organic layer containing carbon fluoride is most preferable because of its low polarity.

  When an organic layer containing fluorocarbon is used as the buffer layer 8, a coating method is selected as the film forming method. The coating solution contains a compound containing fluorocarbon and a solvent, but may contain other additives and polymers.

  The compound containing fluorocarbon is not limited as long as it is a component that does not volatilize by heat treatment. For example, a coupling agent such as silane, titanate, and aluminate, and a high molecular weight substance can be used. Examples of the high molecular weight material include a fluororesin having an etheric oxygen atom. Specific examples of the fluororesin having an etheric oxygen atom include resins containing structural units represented by the following general formulas (2) to (4).

（式中、Ｚはエーテル性酸素原子を有する炭素原子数１〜３のフルオロアルキレン基である。）

(In the formula, Z is a C 1-3 fluoroalkylene group having an etheric oxygen atom.)

  Commercially available products such as Cytop (manufactured by Asahi Glass) are available for such fluororesins having etheric oxygen atoms. Also known polymers having fluorocarbons can be used, such as polyacrylate, polymethacrylate, polystyrene, polyester, polyurethane, polyolefin, chlorinated polyolefin, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, alkyd. Insulating organic polymers such as phenol resin, polyimide, and polyamide can be used. Among these, polyacrylate, polymethacrylate, phenol resin, polyimide, polyamide and the like are preferable.

  It is preferable that the buffer layer does not act as an electron donor or an electron acceptor with respect to the metal oxide semiconductor layer. That is, a high molecular weight product having few sensitive groups such as a hydroxyl group, a carbonyl group, and an amide group is preferable, and in particular, a fluororesin mainly containing the structural units represented by the general formulas (2) to (4) is preferable.

  In addition, since oxygen present in the air or during the film formation process is adsorbed to the metal oxide semiconductor layer to transfer charges, the buffer layer preferably has a barrier property against water. From such a viewpoint, a fluororesin is preferable.

  As a film formation method when an organic layer containing fluorocarbon is used as the buffer layer 8, a spin coating method, a dip coating method, a screen printing method, a roll coating method, an ink jet coating method, a die coating method, a transfer printing method, and a spray method are used. A slit coat method or the like can be used.

  By applying heat treatment after coating, the low molecular weight components are volatilized and a denser film can be formed. The heat treatment temperature at this time is preferably 40 ° C to 300 ° C. The lower temperature is more preferably 40 ° C. to 180 ° C. because damage to the electrode and the substrate is less. Although baking time is not specifically limited, For example, they are 3 minutes-24 hours. In addition, two or more stages of heat treatment may be performed for the purpose of improving the film formability. In the case where two or more stages of heat treatment are performed, the heat treatment conditions for the first stage are preferably 40 ° C to 120 ° C. The heat treatment atmosphere can be appropriately selected from any of air, nitrogen, argon, and reduced pressure.

  In the heat treatment step, a heating method is not limited, and a highly versatile and inexpensive heating device such as a hot plate, an IR furnace, or an oven can be used.

  The method of forming the protective layer 9 by the above-described coating and baking makes it easy to increase the area with a simple configuration as compared with the case where a vacuum film forming apparatus such as a CVD method is used.

  Although the thickness of the buffer layer 8 is not specifically limited, For example, it can be 1-1000 nm. In view of the water vapor barrier property, 100 to 1000 nm is particularly preferable. A suitable dielectric constant of the buffer layer is 2.9 or less.

  The layer 10 containing fluorocarbon is a layer having a water vapor barrier property. As a specific example, the compound containing the same fluorocarbon as the organic layer containing the fluorocarbon of the buffer layer 8 is mentioned, and especially the fluororesin containing an etheric oxygen atom is more preferable. The specific structure of the fluororesin containing an etheric oxygen atom is the same as that exemplified for the buffer layer 8.

  The protective layer 9 formed on the buffer layer 8 by a coating method is obtained by applying and forming a protective layer forming composition containing a polymer containing a hydroxyl group as a repeating unit and a solvent.

  Since the metal oxide semiconductor layer causes characteristic deterioration due to adsorption of oxygen, the protective layer 9 should have a higher gas barrier property against oxygen. In order to obtain the protective layer 9 having a high oxygen gas barrier property, a structure containing a large number of hydroxyl groups is preferable because the film density is increased. In order to obtain such a protective layer 9 having a high oxygen gas barrier property, the polymer containing a hydroxyl group in a repeating unit is preferably a polymer containing a structural unit represented by the following general formula (1).

（式中、Ｒは、それぞれ単独に、水素原子又は炭素原子数１〜１２のアルキル基、Ｘは、単結合、カルボニル基、スルホニル基、炭素原子数１〜１２の有機基からなる群より選択される１種である。）

(In the formula, each R is independently a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and X is a single bond, a carbonyl group, a sulfonyl group, or an organic group having 1 to 12 carbon atoms. 1 type.)

  R in the general formula (1) is an alkyl group having 1 to 12 carbon atoms such as a single bond, a methyl group, or an ethyl group, and a hydrogen atom is particularly preferable because the film density increases. X in the general formula (1) is a single bond, a carbonyl group, a sulfonyl group, a linear or branched alkylene group having 1 to 12 carbon atoms, or a divalent organic group having 1 to 12 carbon atoms. Specific examples of the divalent organic group having 1 to 12 carbon atoms include divalent organic groups represented by the following general formula (X-1). Among these, a single bond, a carbonyl group, and a group represented by the following general formula (X-1) are particularly preferable.

（式中、Ｒ_２は、それぞれ単独に、水素原子、又は炭素原子数１〜３のアルキル基を表す。）

(In the formula, each R ₂ independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.)

  In addition, as X of General formula (1), the bivalent organic group derived from the structure of the following hydroxyl group containing polymeric vinyl monomer can also be used.

  In the polymer containing the structural unit of the general formula (1), the proportion of the unit structure of the general formula (1) is preferably 40 mol% or more, more preferably 60 mol% or more, more preferably 90 mol% or more from the viewpoint of gas barrier properties. Further preferred.

  From the viewpoint of oxygen gas barrier properties, the polymer containing the structural unit of the general formula (1) is 60% by mass of the total solid content contained in the protective layer forming composition containing a polymer containing a hydroxyl group as a repeating unit and a solvent. More preferably, it is 70 mass%, More preferably, it is 90 mass%.

  The polymer containing a hydroxyl group in a repeating unit can be obtained, for example, by polymerizing a polymerizable monomer containing at least one hydroxyl group-containing polymerizable vinyl monomer.

  Specific examples of the hydroxyl group-containing polymerizable vinyl monomer include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (Meth) acrylic acid-2-hydroxybutyl, (meth) acrylic acid-3-hydroxybutyl, (meth) acrylic acid-2-hydroxypropyl, (meth) acrylic acid-3-hydroxybutyl, (meth) acrylic acid- (Methoxy) such as 2-methoxyethyl, 3-methoxybutyl (meth) acrylate, 2,3-dihydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3,4-dihydroxybutyl (meth) acrylate, etc. ) Hydroxyalkyl acrylate, hydroxy styrene N-methylol (meth) acrylamide, (meth) allyl alcohol, crotyl alcohol, isocrotyl alcohol, 1-buten-3-ol, 2-buten-1-ol, 2-butene-1,4-diol, Propargyl alcohol, 2-hydroxyethyl propenyl ether, sucrose allyl ether, (meth) acrylic acid-2-hydroxy-3-phenyloxypropyl, hydroxybutyl (meth) acrylate, glycidyl (meth) acrylate and (meth) acrylic acid Half esterified product of bisphenol type epoxy resin and (meth) acrylic acid, diethylene glycol mono (meth) acrylate, dipropylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, acrylic acid poly Alkylene glycol, 3-chlorohydroxypropyl acrylate, 2-hydroxyethyl acrylamide, vinyl phosphonic acid, vinyl sulfonic acid, Placcel FM1 ((meth) acrylic acid-2-hydroxyethyl-caprolactone adduct: product of Daicel Chemical Industries), Plaxel Examples include addition reaction products of 2-hydroxyethyl (meth) acrylate and caprolactone known as FA and FM series.

  In addition, polymerizable monomers other than hydroxyl group-containing polymerizable vinyl monomers can be used in combination as long as the gas barrier properties are not impaired. Examples of such polymerizable monomers include cyano group-containing monomers such as acrylonitrile, vinyl esters such as vinyl acetate, aromatic vinyl compounds such as styrene, phenoxyethyl (meth) acrylate, and benzyl (meth) acrylate, and acrylamide. Amide group-containing monomers such as dimethylacrylamide and diethylacrylamide, amino group-containing monomers such as N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, glycidyl (meth) acrylate, allyl Epoxy group-containing monomers such as glycidyl ether, vinyl ethers such as N-acryloylmorpholine, vinyl ethyl ether, butyl vinyl ether, (meth) acrylic acid, carboxyethyl acrylic Component having a functional group that acts as a crosslinking base point, such as a carboxyl group-containing monomers such as over preparative, vinyl chloride, vinyl bromide, vinylidene chloride. The above components can be used alone or in combination of two or more.

  In the polymer obtained by polymerizing a polymerizable monomer containing at least one hydroxyl group-containing polymerizable vinyl monomer, the content of polymerizable monomers other than the hydroxyl group-containing polymerizable vinyl monomer is less than 60 mol%. Preferably, it is less than 40 mol%, more preferably less than 10 mol%.

  A polymer containing a hydroxyl group in a repeating unit can be obtained by polymerizing and hydrolyzing a polymerizable monomer containing a polymerizable vinyl monomer having a group that generates a hydroxyl group by at least one kind of hydrolysis.

  Specific examples of the polymerizable vinyl monomer having a group that generates a hydroxyl group by hydrolysis of at least one kind include vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl pivalate, and acetoxystyrene. A polymer obtained by polymerizing these vinyl esters or acetoxystyrene has a hydroxyl group formed by alkali hydrolysis (saponification), and in the general formula (1), R is a hydrogen atom and X is a structural unit or a general formula ( In 1), a structural unit having R as a hydrogen atom and X as a phenylene group is obtained. The ester part may be completely converted to a hydroxy group (completely saponified), or only a part may be converted to a hydroxyl group (partially saponified).

  The ratio converted to the hydroxyl group is called saponification degree. From the viewpoint of gas barrier properties, the saponification degree is preferably 51 mol% or more, more preferably 70 mol% or more, and most preferably 97 mol% or more. As the polymer obtained by saponifying such a polymer of vinyl ester or acetoxystyrene, commercially available products are available, for example, polyvinyl alcohol (Sigma Aldrich), polyvinyl phenol (Sigma Aldrich), and the like.

  In addition, a polymerizable monomer other than the polymerizable vinyl monomer having a group that generates a hydroxyl group can be used in combination as long as the gas barrier property is not impaired. Examples of such a polymerizable monomer include acrylic acid, methacrylic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, acrylonitrile, methacrylonitrile, acrylamido-2-methylpropanesulfonic acid or its Examples thereof include sodium salt, sodium vinyl sulfonate, sodium allyl sulfonate, ethyl vinyl ether, butyl vinyl ether, vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, vinylidene fluoride, tetrafluoroethylene and the like. Polymerization having a hydroxyl group-forming polymer in a polymer obtained by polymerizing and hydrolyzing a polymerizable monomer containing a polymerizable vinyl monomer having a hydroxyl group-producing group by at least one kind of hydrolysis The content of polymerizable monomers other than vinyl monomers is preferably less than 60 mol%, more preferably less than 40 mol%, and even more preferably less than 10 mol%.

  In the present invention, the polymer having a hydroxyl group as a repeating unit preferably has a weight average molecular weight Mw of 2,000 to 300,000, more preferably 5,000 to 130,000.

  The solvent for the protective layer-forming composition containing a polymer containing a hydroxyl group as a repeating unit and a solvent is not limited as long as it dissolves the polymer. For example, water, alcohols, phenols, ethers, ketones , Esters, nitrogen-containing compounds, sulfur-containing compounds and hydrocarbons are preferred.

  Examples of alcohols include methanol, n-propanol, isopropanol, n-butanol, 2-methyl-1-propanol, tert-butanol, 4-methyl-2-pentanol, benzyl alcohol, α-terpineol, ethylene glycol, Propylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether, propylene glycol monobutyl ether, glycerin, diethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether It is done.

  Examples of phenols include phenol, o-cresol, m-cresol, and p-cresol.

  Examples of ethers include dioxane, furfural, ethylene glycol dimethyl ether, methyl cellosolve, ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, isobutyl carbitol, dipropylene glycol monomethyl ether, butyl carbitol acetate, methyl cellosolve acetate, Examples include ethyl cellosolve acetate, propylene glycol monoethyl ether acetate, propylene glycol propyl ether acetate, propylene glycol monobutyl ether acetate, and epichlorohydrin.

  Examples of ketones include acetone, methyl ethyl ketone, 2-methyl-4-pentanone, diacetone alcohol, cyclopentanone, cyclohexanone, and acetophenone.

  Examples of esters include methyl formate, ethyl formate, methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, 3-methoxybutyl acetate, n-pentyl acetate, ethyl propionate, ethyl lactate, benzoic acid Examples thereof include methyl, diethyl malonate, dimethyl phthalate, diethyl phthalate, diethyl carbonate, ethylene carbonate, propylene carbonate, cellosolve acetate, butyl carbitol acetate, ethyl acetoacetate, methyl cyanoacetate and ethyl cyanoacetate.

  Examples of the nitrogen-containing compound include nitromethane, nitrobenzene, acetonitrile, propionitrile, succinonitrile, valeronitrile, benzonitrile, ethylamine, diethylamine, ethylenediamine, aniline, N-methylaniline, N, N-dimethylaniline, o- Toluidine, p-toluidine, piperidine, pyridine, α-picoline, 2,6-lutidine, quinoline, propylenediamine, formamide, N-methylformamide, N, N-dimethylformamide, N, N-diethylformamide, acetamide, N- Examples include methylacetamide, N-methylpropionamide, N, N, N ′, N′-tetramethylurea and N-methylpyrrolidone.

  Examples of the sulfur-containing compound include dimethyl sulfoxide and sulfolane. Examples of the hydrocarbon include benzene, toluene, xylene, mesitylene, p-cymene, naphthalene, cyclohexylbenzene, and cyclohexene, and one or more of these can be used. Among these, dimethyl sulfoxide, water, or a mixed solvent of glycerin and water is preferably used. 1-40 mass% is suitable for the density | concentration of the polymer which contains a hydroxyl group in a repeating unit, 2-30 mass% is more suitable, and 3-20 mass% is the most suitable.

  The protective layer forming composition may contain a plasticizer, a surfactant, a cross-linking agent and the like, if necessary.

  As the plasticizer that can be contained, polyhydric alcohol is preferably used, and specific examples thereof include, for example, ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane and the like. Can be mentioned. These polyhydric alcohols can be used alone or in combination of two or more.

  As addition amount of a polyhydric alcohol, 1-30 mass parts is preferable with respect to 100 mass parts of polymers which contain a hydroxyl group in a repeating unit, 1-25 mass parts is more preferable, Especially 1-20 mass parts is the most preferable. If the amount is more than 20 parts by mass, the gas barrier property may be lowered.

  There is no particular limitation on the type of surfactant that can be contained, but nonionic surfactants are preferred. Nonionic surfactants include, for example, alkyl ether types such as polyoxyethylene oleyl ether, alkylphenyl ether types such as polyoxyethylene octylphenyl ether, alkyl ester types such as polyoxyethylene laurate, and polyoxyethylene laurylamino. Alkylamine type such as ether, alkylamide type such as polyoxyethylene lauric acid amide, polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether, alkanolamide type such as oleic acid diethanolamide, polyoxyalkylene allyl phenyl ether, etc. Nonionic surfactants such as allyl phenyl ether type are preferred. These surfactants can be used alone or in combination of two or more.

  As addition amount of surfactant, 0.01-1 mass part is preferable with respect to 100 mass parts of polymers which contain a hydroxyl group in a repeating unit, 0.02-0.5 mass part is more preferable, Especially 0.05 -0.3 parts by mass is most preferred. When the amount is less than 0.01 part by mass, the effect of the surfactant does not appear, and when the amount is more than 1 part by mass, the gas barrier property may be deteriorated.

  As a crosslinking agent that can be contained, a compound capable of reacting with a hydroxyl group, an amino group, an amide group, or the like such as a polyisocyanate compound, an epoxy compound, or an aziridine compound can be used as the crosslinking agent. Of these, polyisocyanate compounds and epoxy compounds are particularly preferably used.

  Examples of the polyisocyanate compound include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate, alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate, 2,4-tolylene diisocyanate, Aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate and xylylene diisocyanate, trimethylolpropane / tolylene diisocyanate trimer adduct (trade name Coronate L), trimethylolpropane / hexamethylene diisocyanate trimer adduct ( Product name Coronate HL), isocyanurate form of hexamethylene diisocyanate (Product name Coronate HX) [all Nippon Poly Urethane Kogyo Co., Ltd.] and the like isocyanate adducts such. Examples of the epoxy compound include N, N, N ′, N′-tetraglycidyl-m-xylenediamine (trade name: TETRAD-X) and 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane (trade name: TETRAD- C) [all manufactured by Mitsubishi Gas Chemical Co., Ltd.]. These crosslinking agents are used alone or in a mixture of two or more. The amount of the crosslinking agent to be used is appropriately selected according to the balance with the polymer to be crosslinked and further according to the properties as a protective layer.

  As a coating method of a protective layer forming composition containing a polymer containing a hydroxyl group in a repeating unit and a solvent, a spin coating method, a dip coating method, a screen printing method, a roll coating method, an ink jet coating method, a die coating method, a transfer printing method A spray method, a slit coat method, or the like can be used.

  By applying heat treatment after coating, the low molecular weight components are volatilized and a denser film can be formed. The heat treatment temperature at this time is preferably 40 ° C to 300 ° C. The lower temperature is more preferably 40 ° C. to 180 ° C. because damage to the electrode and the substrate is less. Although baking time is not specifically limited, For example, they are 3 minutes-24 hours. In addition, two or more stages of heat treatment may be performed for the purpose of improving the film formability. In the case where two or more stages of heat treatment are performed, the heat treatment conditions for the first stage are preferably 40 ° C to 120 ° C. The heat treatment atmosphere can be appropriately selected from any of air, nitrogen, argon, and reduced pressure.

  In the heat treatment step, a heating method is not limited, and a highly versatile and inexpensive heating device such as a hot plate, an IR furnace, or an oven can be used.

  The method of forming the protective layer 9 by the above-described coating and baking makes it easy to increase the area with a simple configuration as compared with the case where a vacuum film forming apparatus such as a CVD method is used.

  Although the thickness of the protective layer 9 is not specifically limited, For example, it can be 500 nm-30 micrometers. Preferably, it is 1 μm to 10 μm.

  Since the relative dielectric constant is a physical property value having a correlation with the film density, a film having a higher value has a higher film density. That is, the relative dielectric constant is preferably 3.0 to 15.0 from the viewpoint of moisture barrier properties.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the examples.

  The evaluation methods performed in this example are as follows.

<Measurement of mobility of thin film transistor>
The mobility of the metal oxide semiconductor was calculated from the transfer characteristics of the thin film transistor. For the measurement of the transfer characteristics, source meters 2635 and 2400 (both KEITHLEY) were used. The thin film transistor was installed in a shield case to reduce the influence of noise. The inside of the shield case was kept at light shielding, atmospheric pressure, 25 ± 2 ° C., and humidity 92 ± 5%.

Transfer characteristic, swept 0.5V step the gate voltage _{V G} from -30V to + 30 V to (Sweep), when the drain voltage _{V D} and + 20V, the current flowing between the source electrode 5 and drain electrode 6 (drain Current) Measured from _ID .

The drain current _ID in the saturated state can be expressed by the following formula. The mobility μ of the metal oxide semiconductor can be obtained from the slope of the graph when the square root of the absolute value of the drain current _ID is plotted on the vertical axis and the gate voltage V _G is plotted on the horizontal axis. In the present invention, the mobility was calculated using the following formula.

[Formula 1]
_{I D = WCμ (V G -V} th) 2 / 2L (1)
(Wherein, W is the channel width of the transistor, L is the channel length of the transistor, C is the capacitance of the gate insulating layer, _Vth is the threshold voltage of the transistor, and μ is the mobility.)

The threshold voltage V _th has a gate voltage when the extrapolated drain current 0A the linear part of the graph is defined as the threshold voltage V _th.

<Bias stress test of thin film transistor>
The stability of the thin film transistor was evaluated by applying electrical stress to the thin film transistor. For stress, a gate voltage V _G 30 V and a drain voltage V _D 0 V were applied to the thin film transistor for 10,000 seconds, and then the transfer characteristics were measured in the same procedure as the mobility measurement to calculate the threshold voltage. The difference between the threshold voltage before applying stress and the threshold voltage after applying stress was defined as the threshold voltage shift amount. Note that while applying stress, the thin film transistor was kept at light shielding, atmospheric pressure, 25 ± 2 ° C., and humidity 92 ± 5%.

<Method for measuring state density distribution>
It calculated | required by the numerical calculation from the transfer characteristic of the thin-film transistor.

[Example 1]
Formation of a metal oxide semiconductor layer containing an indium compound, a zinc compound, and water filtered on a low resistance silicon substrate 2a with a thermal oxide film having a size of 25 mm × 25 mm using a 0.2 μm PTFE filter immediately before film formation. The composition was applied by spin coating so that the film thickness of the semiconductor layer was 6 nm, and then converted into a metal oxide semiconductor layer precursor film by heat treatment at 150 ° C. for 5 minutes using a hot plate. Next, in order to remove impurities in the film and oxidize, the metal oxide semiconductor layer precursor film was subjected to UV ozone treatment. For UV ozone treatment, a UV ozone generator manufactured by SEN LIGHTTS CORPORATION was used. The light source is PL2003N-10, and the power source is UE2003N-7. Finally, heat treatment was performed at 300 ° C. for 60 minutes using a hot plate to obtain a semiconductor layer 7 containing indium.

  Next, an aluminum thin film was deposited on the semiconductor layer 7 through a shadow mask by a vacuum evaporation method. The aluminum thin film formed here becomes the source electrode 5 and the drain electrode 6 of the thin film transistor. The thin film transistor has a channel length of 200 μm, a channel width of 1 mm, a thermal oxide film on the low-resistance silicon substrate 2a, that is, a relative dielectric constant of the gate insulating layer 4 of 3.9, and a thickness of the gate insulating layer 4 of 200 nm. The substrate 2a also functions as a gate electrode. At this time, the region functioning as the semiconductor layer 7 is only a portion where the density of the electric lines of force generated when a voltage is applied to the source electrode 5 and the drain electrode 6, and the area where the density of the electric lines of force is low, that is, A current hardly flows in a region not sandwiched between the source electrode 5 and the drain electrode 6, and does not function as the semiconductor layer 7.

  Next, Cytop CTL-809M (manufactured by Asahi Glass Co., Ltd.) is applied on the semiconductor layer 7, the source electrode 5 and the drain electrode 6 by a spin coating method so as to have a film thickness of 540 nm. The buffer layer 8 is subjected to heat treatment at 50 ° C. for 10 minutes using a hot plate in the inside, then at 80 ° C. for 30 minutes using the hot plate in the atmosphere, and then at 150 ° C. for 1 hour using hot lept in the atmosphere. Got. The buffer layer 8 was formed so as to completely cover the region functioning as the semiconductor layer 7.

  Subsequently, in order to improve wettability, polyvinyl alcohol Mowiol 40-88 (manufactured by Sigma-Aldrich, weight average molecular weight to 127,000, saponification degree 86.7%) is formed on the buffer layer 8 whose surface is hydrophilically treated by UV ozone treatment. (88.7%) A solution in which 10 g was completely dissolved in 90 g of ultrapure water was applied by spin coating so that the film thickness was 2800 nm, and then the coating layer was cured. The protective layer 9 was obtained by performing heat treatment at 50 ° C. for 10 minutes and then using a hot plate under reduced pressure conditions at 100 ° C. for 2 hours. In this way, a thin film transistor was produced.

The mobility of the thin film transistor in Example 1 was 5.8 cm ² / Vs. As a result of the bias stress test, the shift amount of the threshold voltage was 2.3V. The thin film transistor fabricated by the procedure of this example showed excellent bias stress stability.

[Example 2]
A thin film transistor was fabricated in the same procedure as in Example 1 except that a layer 10 containing fluorocarbon was further formed on the protective layer 9. The layer 10 containing fluorocarbon was formed by the following procedure. On top of the protective layer 9, Cytop CTL-809M (manufactured by Asahi Glass) was applied by spin coating so that the film thickness was 540 nm, and then the coating layer was cured using a hot plate in a nitrogen atmosphere. A layer 10 containing carbon fluoride was obtained by heat treatment at 80 ° C. for 30 minutes using a hot plate in a nitrogen atmosphere at 80 ° C. for 30 minutes and then at 150 ° C. for 1 hour using a hot lept in a nitrogen atmosphere.

The mobility of the thin film transistor in Example 2 was 6.3 cm ² / Vs. As a result of the bias stress test, the shift amount of the threshold voltage was 1.86V. The thin film transistor fabricated by the procedure of this example showed excellent bias stress stability.

  Next, the state density distribution of the thin film transistor of Example 2 was evaluated. The state density distribution was measured immediately after fabrication of the thin film transistor, and then after standing in the air for 72 hours and then in vacuum for 4 hours and 30 minutes. The state density distribution of the thin film transistor of Example 2 did not change significantly immediately after fabrication. That is, the thin film transistor having the stacked structure of the present invention not only has high bias stress reliability, but also has the effect of the stacked structure of the buffer layer 8 and the protective layer 9 even when exposed to a vacuum condition for a long time. Has an excellent characteristic of low state density caused by oxygen defects due to prevention of the elimination of oxygen defects induced in the metal oxide semiconductor layer 7 by the effect of the laminate of the layer 10 containing fluorocarbon. It was confirmed that it was retained.

[Comparative Example 1]
The semiconductor layer 7, the source electrode 5, and the drain electrode 6 were formed on the low resistance silicon substrate 2a with the thermal oxide film in the same procedure as in Example 1.

  Next, 10 g of polyvinyl alcohol Mowiol 40-88 (manufactured by Sigma-Aldrich, weight average molecular weight to 127,000, saponification degree of 86.7% to 88.7%) is ultrapure on the semiconductor layer 7, the source electrode 5 and the drain electrode 6. A solution completely dissolved in 90 g of water was applied by spin coating so that the film thickness was 2800 nm, and then the coating layer was cured using a hot plate in the atmosphere at 50 ° C. for 10 minutes, and then reduced in pressure. A protective layer 9 was obtained by heat treatment at 100 ° C. for 2 hours using a hot plate under the conditions (0.1 MPa). In this way, a thin film transistor was produced.

  However, the buffer layer 8 is not formed in the comparative example 1 unlike the first embodiment.

  In the thin film transistor of Comparative Example 1, the drain current did not change even when the gate voltage was swept, and a large current continued to flow. In the procedure of Comparative Example 1, a normal thin film transistor could not be produced. In addition, it is guessed that the hydroxyl group contained in the film | membrane which consists of polyvinyl alcohol exerted some electric effect | actions to a metal oxide semiconductor, and the carrier concentration of the semiconductor layer and the semiconductor layer surface increased.

[Comparative Example 2]
The semiconductor layer 7, the source electrode 5, and the drain electrode 6 were formed on the low resistance silicon substrate 2a with the thermal oxide film in the same procedure as in Example 1.

  Next, Cytop CTL-809M (manufactured by Asahi Glass Co., Ltd.) is applied on the semiconductor layer 7, the source electrode 5, and the drain electrode 6 by a spin coating method so as to have a film thickness of 540 nm. Then, heat treatment was performed at 50 ° C. for 10 minutes using a hot plate at 80 ° C. for 30 minutes using a hot plate in the air, and then at 150 ° C. for 1 hour using hot lept in the air to form the buffer layer 8. Obtained. In this way, a thin film transistor was produced.

  However, in Comparative Example 2, unlike Example 1, the protective layer 9 is not formed.

The mobility of the thin film transistor in Comparative Example 2 was 5.5 cm ² / Vs. As a result of the bias stress test, the shift amount of the threshold voltage was 4.8V. The thin film transistor manufactured by the procedure of this comparative example cannot be used practically because it has a threshold voltage shift amount of 2.5 V or more.

[Comparative Example 3]
Formation of a metal oxide semiconductor layer containing an indium compound, a zinc compound, and water filtered on a low resistance silicon substrate 2a with a thermal oxide film having a size of 25 mm × 25 mm using a 0.2 μm PTFE filter immediately before film formation. The composition was applied by spin coating so that the film thickness of the semiconductor layer was 6 nm, and then converted into a metal oxide semiconductor layer precursor film by heat treatment at 150 ° C. for 5 minutes using a hot plate. Next, in order to remove impurities in the film and oxidize, the metal oxide semiconductor layer precursor film was subjected to UV ozone treatment. For UV ozone treatment, a UV ozone generator manufactured by SEN LIGHTTS CORPORATION was used. The light source is PL2003N-10, and the power source is UE2003N-7. Finally, heat treatment was performed at 300 ° C. for 60 minutes using a hot plate to obtain a semiconductor layer 7 containing indium.

  Next, an aluminum thin film was deposited on the semiconductor layer 7 through a shadow mask by a vacuum evaporation method. The aluminum thin film formed here becomes the source electrode 5 and the drain electrode 6 of the thin film transistor. The thin film transistor has a channel length of 200 μm, a channel width of 1 mm, a thermal oxide film on a low-resistance silicon substrate, that is, a relative dielectric constant of the gate insulating layer 4 of 3.9, and a thickness of the gate insulating layer 4 of 200 nm. In this way, a thin film transistor was produced.

  However, in Comparative Example 3, unlike Example 1, the protective layer 9 is not formed.

The mobility of the thin film transistor in Comparative Example 3 was 5.7 cm ² / Vs. As a result of the bias stress test, the shift amount of the threshold voltage was 9.2V. The thin film transistor manufactured by the procedure of this comparative example cannot be used practically because it has a threshold voltage shift amount of 2.5 V or more.

  Next, the state density distribution of the thin film transistor of Comparative Example 3 was evaluated. The state density distribution was measured immediately after fabrication of the thin film transistor, then after standing in the air for 72 hours, and then standing in vacuum for 4 hours and 30 minutes. The state density distribution of the thin film transistor of Comparative Example 3 greatly changed depending on the stationary environment. That is, the thin film transistor of Comparative Example 3 is not only low in bias stress stability but also unstable due to the generation of oxygen vacancies accompanying oxygen desorption and the resulting localized levels when exposed to vacuum conditions for a long time. It was shown that it was a characteristic.

  INDUSTRIAL APPLICABILITY The present invention can be used in the industrial field of a thin film transistor used for an active matrix substrate of a flat panel display such as a liquid crystal or an organic EL and a manufacturing method thereof. According to the present invention, a thin film transistor with high bias stress stability and low stability due to oxygen defects can be manufactured. As a result, a flat panel display with little image quality deterioration can be provided.

1, 1A, 1B, 1C, 1D Thin film transistor 2, 2a Substrate 3 Gate electrode 4 Gate insulating layer 5 Source electrode 6 Drain electrode 7 Semiconductor layer (metal oxide semiconductor layer)
8 Buffer layer 9 Protective layer 10 Layer containing carbon fluoride

Claims (14)

A gate insulating layer;
A metal oxide semiconductor layer containing indium;
A buffer layer,
A protective layer formed by applying a protective layer-forming composition containing a polymer containing a hydroxyl group in a repeating unit and a solvent;
In a thin film transistor having a laminate comprising:
A method for manufacturing a thin film transistor, wherein the buffer layer is formed so as to completely cover the metal oxide semiconductor layer, and then the protective layer is formed.   2. The method of manufacturing a thin film transistor according to claim 1, further comprising forming a layer containing fluorocarbon after applying the protective layer forming composition to form the protective layer.   3. The method of manufacturing a thin film transistor according to claim 1, wherein the metal oxide semiconductor layer containing indium is subjected to patterning before forming the buffer layer.   The method for manufacturing a thin film transistor according to claim 1, wherein the metal oxide semiconductor layer containing indium is formed by coating. The method for producing a thin film transistor according to any one of claims 1 to 4, wherein the polymer containing a hydroxyl group in a repeating unit is a polymer containing a structural unit represented by the following general formula (1).

(In the formula, each R is independently a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and X is a single bond, a carbonyl group, a sulfonyl group, or an organic group having 1 to 12 carbon atoms. One type selected.)   5. The polymer according to claim 1, wherein the polymer containing a hydroxyl group in a repeating unit is a polymer obtained by polymerizing a polymerizable monomer containing at least one hydroxyl group-containing polymerizable vinyl monomer. The manufacturing method of the thin-film transistor of description.   The polymer containing a hydroxyl group in a repeating unit is a polymer obtained by polymerizing a polymerizable monomer containing a polymerizable vinyl monomer having a group that generates a hydroxyl group by at least one kind of hydrolysis. The method for producing a thin film transistor according to any one of claims 1 to 4.   The method for producing a thin film transistor according to any one of claims 1 to 7, wherein the protective layer forming composition is a resin forming composition containing 10 mass% or more of water.   The method for producing a thin film transistor according to any one of claims 1 to 8, wherein the protective layer formed by applying the protective layer forming composition is a protective layer having a relative dielectric constant of 3.0 or more. .   The method of manufacturing a thin film transistor according to claim 1, wherein the buffer layer contains carbon fluoride.   The method for manufacturing a thin film transistor according to any one of claims 1 to 10, wherein the buffer layer is a layer containing a fluororesin.   The method for manufacturing a thin film transistor according to claim 1, wherein the buffer layer is a resin layer having a relative dielectric constant of 2.9 or less.   A thin film transistor manufactured by the manufacturing method according to claim 1. 14. The thin film transistor according to claim 13, wherein a _Vth shift due to a positive bias stress is less than 2V.

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