JP2010258058A - Method for manufacturing metal oxide semiconductor, metal oxide semiconductor and thin-film transistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve semiconductor characteristics (mobility, on/off ratio and threshold (Vth)), to improve the production efficiency, and to reduce the variations in thin-film transistor that uses a metal oxide semiconductor. <P>SOLUTION: In a method for manufacturing the metal oxide semiconductor that executes heat treatment to a semiconductor precursor layer formed on a substrate for forming a metal oxide semiconductor, the semiconductor precursor layer is simultaneously irradiated with electromagnetic waves with the heat treatment. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a metal oxide semiconductor with improved semiconductor characteristics and high production efficiency, and also relates to a semiconductor device using the same, particularly a thin film transistor.

  A technique of a thin film transistor using an oxide semiconductor is disclosed (for example, Patent Documents 1 to 3 and Non-Patent Document 1). In these thin film transistors, the semiconductor layer used is a vacuum system such as sputtering, and it is said that the production efficiency is low. There is also a problem with variations in manufacturing. In order to eliminate these variations, high temperature treatment was required.

  On the other hand, as a technique capable of forming an oxide semiconductor film at normal pressure, there is a technique proposed in Patent Document 4 and the like. However, in a thin film transistor using the oxide semiconductor, further high-temperature processing is required and carrier transfer is performed. There are problems such as low degree, high off current, and deterioration of threshold Vth.

  The present invention greatly improves these characteristics.

JP 2006-165527 A JP 2006-165528 A JP 2007-73735 A US Patent Application Publication No. 2007/0184576

IDW'07 (International Display Workshop 2007) p1783

  Accordingly, an object of the present invention is to improve semiconductor characteristics (mobility, on / off ratio, threshold value (Vth)), improve production efficiency, and to reduce variations in thin film transistors using the semiconductor characteristics.

  The above object of the present invention is achieved by the following means.

  1. In the method for manufacturing a metal oxide semiconductor, in which a semiconductor precursor layer formed on a substrate is subjected to heat treatment to form a metal oxide semiconductor, the semiconductor precursor layer is irradiated with electromagnetic waves simultaneously with the heat treatment. A method for producing a metal oxide semiconductor.

  2. 2. The method for producing a metal oxide semiconductor according to 1 above, wherein the electromagnetic wave is a microwave.

  3. 3. The method for producing a metal oxide semiconductor according to 1 or 2, wherein the temperature of the heat treatment is 100 ° C. to 250 ° C.

  4). 4. The method for producing a metal oxide semiconductor according to any one of 1 to 3, wherein the heat treatment uses a heat source from outside the substrate.

  5. 5. The method for producing a metal oxide semiconductor as described in 4 above, wherein the heat source used for the heat treatment contains a metal oxide, and the heat treatment is performed by heat generated by the metal oxide absorbing electromagnetic waves.

  6). 6. The method for producing a metal oxide semiconductor according to any one of 1 to 5, wherein the semiconductor precursor layer is formed from a coating film of a solution or dispersion liquid of a precursor material.

  7). 7. The method for producing a metal oxide semiconductor as described in 6 above, wherein the precursor material solution is an aqueous solution.

  8). 8. The method for producing a metal oxide semiconductor as described in 6 or 7 above, wherein the precursor material contains any one of In, Zn, and Sn.

  9. 9. The method for producing a metal oxide semiconductor according to any one of 6 to 8, wherein the precursor material contains either Ga or Al.

  10. 10. A metal oxide semiconductor produced using the method for producing a metal oxide semiconductor according to any one of 1 to 9 above.

  11. 11. A thin film transistor using the metal oxide semiconductor described in 10 above.

  According to the present invention, a thin film transistor in which semiconductor characteristics (mobility, on / off ratio, Vth) are improved, variation is reduced, and production efficiency is improved can be obtained.

It is a cross-sectional schematic diagram which shows an example of thin-film transistor manufacture using the method of this invention. It is a cross-sectional schematic diagram which shows another example of the heat processing which irradiates electromagnetic waves from the outside. It is a figure which shows the typical element structure of a thin-film transistor element. It is a schematic equivalent circuit diagram which shows an example of a thin-film transistor sheet. It is a cross-sectional schematic diagram which shows each process of preparation of a thin-film transistor.

  Hereinafter, embodiments for carrying out the present invention will be described in detail.

  The present invention provides a method for producing a metal oxide semiconductor in which a semiconductor precursor layer formed on a substrate is subjected to heat treatment to form a metal oxide semiconductor, and the semiconductor precursor layer is irradiated with electromagnetic waves simultaneously with the heat treatment. It is characterized by.

  In addition, here, the semiconductor precursor layer is preferably formed from a coating film of a solution or dispersion of a precursor material.

  The semiconductor precursor material is an inorganic salt, an organic metal compound, or an organic metal complex that forms a metal oxide by heat treatment. After a thin film of the precursor material is provided, a semiconductor such as heat treatment is applied to the thin film. A conversion treatment is performed to convert the metal oxide semiconductor into a semiconductor thin film.

  The temperature of the heat treatment is 100 ° C. to 250 ° C., and the semiconductor precursor layer on the substrate is converted into a metal oxide semiconductor by heat treatment at a relatively low temperature to obtain an oxide semiconductor thin film.

  Moreover, as an electromagnetic wave irradiated to a semiconductor precursor layer at the time of heat processing, a microwave (0.3 GHz-50 GHz) is preferable among electromagnetic waves, and in addition to heat processing, this is irradiated, and a thermal oxidation reaction is carried out in a short time. Can be advanced. The metal oxide partially generated by thermal oxidation due to heating absorbs electromagnetic waves and generates heat again, so it is thought that the conversion process to semiconductor is accelerated, but the degree of acceleration is large and details are unknown. Absent.

  Directly on the semiconductor precursor layer, and after forming a gate electrode made of a material that absorbs electromagnetic waves, such as ITO, in the vicinity, it is irradiated with electromagnetic waves to generate heat and then converted to a metal oxide semiconductor. This method is also preferably a method in which heat treatment and electromagnetic wave irradiation are used in combination.

  However, it is a more preferable method to further irradiate electromagnetic waves using heat treatment from outside (outside the substrate). When this method is used, the oxidation reaction can proceed with less variation in a shorter time.

  As a heating method from the outside of the substrate, in addition to using an oven, a heater, a heat block (hot plate), as an external heater, a material that absorbs electromagnetic waves such as a metal oxide (for example, ITO) is used as described later. Alternatively, the metal oxide may be irradiated with electromagnetic waves to absorb the electromagnetic waves, and heat generated thereby may be applied from the outside. In this case, inevitably, in addition to the external heat treatment using the metal oxide generated by the electromagnetic wave irradiation as a heater, the electromagnetic wave is simultaneously irradiated, and the external heating and the electromagnetic wave irradiation are performed at once. It is preferable.

  A method of the present invention for manufacturing a thin film transistor will be described with reference to schematic cross-sectional views.

  A precursor material of a metal oxide semiconductor, for example, a metal nitrate, more specifically, for example, indium nitrate, zinc nitrate, and gallium nitrate were mixed at a metal ratio of 1: 1: 1 (molar ratio) (10 mass). As shown in FIG. 1, for example, an aqueous solution is applied on a substrate on which a pattern of a gate electrode 2, a gate insulating layer 3, and further a source electrode 4 and a drain electrode 5 is formed by, for example, an inkjet method. Apply and pattern the precursor material thin film 6 'uniformly. (FIG. 1 (2)).

  Next, the precursor material thin film 6 'on the substrate is heated by the heater block. The heating temperature may be in the temperature range of 100 ° C. to 250 ° C., and depending on the method, it may be heated in the range of milliseconds to 60 minutes. In the present invention, electromagnetic waves such as microwaves are irradiated simultaneously with this heating.

  1 (3), the entire substrate is heated on the heater block H (the temperature can be measured with a surface thermometer using a thermocouple). The aspect which irradiated was shown.

  In the microwave irradiation, heating by the heater and the microwave output are adjusted so that the surface temperature of the precursor thin film on the substrate is maintained at 100 to 200 ° C.

  In addition, the oxide semiconductor precursor material thin film is cleaned by a dry cleaning process such as oxygen plasma or UV ozone cleaning after the formation and before the semiconductor conversion process. It is also preferable to decompose and wash the organic matter to remove organic matter other than the metal component.

  By thermal oxidation using both heat treatment and microwave irradiation, the oxide semiconductor layer 6 is formed in the channel region, so that a thin film transistor is formed (FIG. 1D).

  FIG. 2 shows another example of the present invention in which heat treatment is performed by irradiating electromagnetic waves from the outside.

  As shown in FIG. 2, a precursor material thin film 6 ′ is similarly uniformly applied and formed on a substrate C (FIG. 2 (1)) on which a gate electrode and a gate insulating layer are formed, and a metal oxide, for example, an ITO pattern is formed. Using a ceramic plate P having a thickness, the substrate is adhered to the substrate C, and irradiated with microwaves, while irradiating while controlling the microwave output so as to keep the surface temperature of the precursor material thin film 6 ′ at 100 to 200 ° C.

  In this case as well, a base material having ITO (pattern) (using a material that does not absorb electromagnetic waves) is used as a heat source from the outside of the substrate to generate heat by performing microwave irradiation, and this is used as an external heat source for the precursor material thin film Heat. For example, if a material that transmits electromagnetic waves, such as glass or ceramic, is used as the substrate having the ITO pattern, the semiconductor precursor thin film in contact with the ITO is heated at the same time when the microwave is irradiated from the back side of the substrate. In addition, the semiconductor precursor thin film itself also receives microwave irradiation at the same time.

  In the present invention, simultaneous irradiation does not have to be performed in synchronization with external heating at all, and it is sufficient if there is a portion overlapping external heating and electromagnetic wave irradiation.

  Microwave irradiation may be further performed from the side of the semiconductor substrate opposite to the substrate side serving as a heat source.

  When the precursor material thin film 6 ′ is uniformly applied and formed on the support, the remaining precursor material thin film can be removed by washing (for example, washing with water) after being converted into a metal oxide semiconductor, and converted. Since only the oxide semiconductor remains, a top contact type thin film transistor having a bottom gate structure can be formed by patterning the source electrode 4 and the drain electrode 5 by vapor deposition, for example.

  In this way, in addition to external heating, electromagnetic wave irradiation can be performed to accelerate the conversion of the precursor material into a metal oxide semiconductor. Since the precursor material thin film basically does not absorb microwaves only by irradiation with electromagnetic waves, it takes time to convert to a semiconductor. In addition, the conversion rate is slow only by external heating, and a high temperature is required for conversion.

  As described above, in the present invention, the conversion process from the semiconductor precursor material thin film to the metal oxide semiconductor can be accelerated by performing electromagnetic wave irradiation simultaneously with the external heating process. Since the conversion to semiconductor can be performed quickly, the productivity of the semiconductor thin film or thin film transistor can be improved, and there are few side reactions, semiconductor characteristics (mobility), and the on / off ratio of the thin film transistor. Further, the threshold value (Vth) and the like can be improved.

  The semiconductor precursor material used in the present invention is not limited as long as it contains an inorganic metal salt, an organic metal compound, or an organic metal complex containing a metal of a metal oxide semiconductor. Among these, metal salts are preferable. Metal salts selected from metal nitrates, sulfates, phosphates, carbonates, acetates or oxalates are preferred. The semiconductor precursor layer made of these metal salts is preferably formed by applying a solution of the metal salt.

  In the present invention, the metal oxide semiconductor is a metal oxide. In the present invention, a thin film of a metal salt containing a metal component of a metal oxide serving as a precursor of the metal oxide semiconductor is provided, and then the thin film is externally applied to the thin film. Simultaneously with the heat treatment, irradiation with electromagnetic waves is performed to convert into a metal oxide semiconductor to obtain a semiconductor thin film.

  As the metal in the metal salt preferably used in the present invention, 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, In, Ir, Sn, Sb, Cs, Ba, La, Hf, Ta, W, Tl, Pb, Bi, Ce, Pr, Nd , Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and the like.

  In the present invention, these metal salts preferably contain one or more of any of indium (In), tin (Sn), and zinc (Zn), and may be used in combination.

  Moreover, it is preferable that the other metal contains a salt of either gallium (Ga) or aluminum (Al).

  In the present invention, by using the above metal salt as a precursor material, a metal oxide semiconductor having a high carrier mobility and a good on / off ratio when a thin film transistor element is obtained can be obtained.

  These metal salts have low energy of oxidation reaction including hydrolysis and dehydration reaction, and decomposition products generated in the process of oxide formation are efficiently vaporized and discharged, and are difficult to remain in the film. It is estimated that good semiconductor characteristics can be obtained because there are few impurity components such as carbon.

  Among the metal salts, nitrate is particularly preferable from the viewpoint of reducing impurities and improving semiconductor characteristics.

  The effect of improving the semiconductor characteristics obtained with metal salts, particularly nitrates, is particularly remarkable in an amorphous metal oxide semiconductor obtained in the temperature range of the present invention in which the heating temperature is 100 ° C. or higher and 250 ° C. or lower.

(Precursor thin film formation method, patterning method)
In order to form a thin film containing a metal salt that is a precursor of these metal oxide semiconductors, a known film formation method, vacuum deposition method, molecular beam epitaxial growth method, ion cluster beam method, low energy ion beam method, An ion plating method, a CVD method, a sputtering method, an atmospheric pressure plasma method, or the like can be used. In the present invention, it is preferable to apply a solution obtained by dissolving the metal salt in an appropriate solvent on the substrate. As a result, productivity can be greatly improved.

  The solvent for dissolving the metal salt is not particularly limited as long as it dissolves the metal compound to be used in addition to water, such as water, alcohols such as ethanol, propanol and ethylene glycol, tetrahydrofuran, dioxane and the like. Ether type, ester type such as methyl acetate and ethyl acetate, ketone type such as acetone, methyl ethyl ketone and cyclohexanone, glycol ether type such as diethylene glycol monomethyl ether, acetonitrile and the like, further aromatic solvents such as xylene and toluene, hexane, It is possible to use α-terpineol such as cyclohexane and tridecane, halogenated alkyl solvents such as chloroform and 1,2-dichloroethane, N-methylpyrrolidone, carbon disulfide and the like.

  The solvent used in the metal salt solution of the present invention is not particularly limited as long as the metal salt is soluble, but water and lower alcohol are preferable from the viewpoint of solubility of the metal salt and drying property after coating. Among these, methanol, ethanol, and propanol (1-propanol and isopropanol) are preferable from the viewpoint of dryness. Moreover, a lower alcohol may be used alone as a solvent, or may be used by mixing with water at an arbitrary ratio. From the viewpoints of solubility, solution stability, and drying properties, it is preferable to prepare “aqueous solution” of the present invention by mixing water and these lower alcohols. When an aqueous solution is prepared by mixing a lower alcohol, the surface tension can be lowered without greatly changing the composition.

  Further, as an effect of adding alcohols, an effect of improving semiconductor characteristics is also recognized. For example, improvement in characteristics such as mobility, on / off ratio, and threshold value of the thin film transistor is recognized. Although the cause of this effect is not clear, it is presumed that it has an influence on the oxide formation process by heating.

  In addition, when considering semiconductor characteristics such as drying characteristics, inkjet emission characteristics, and thin film transistor characteristics, it is preferable to add a lower alcohol with a solvent ratio of 5% by mass or more, and satisfy any characteristics (drying, emission characteristics and solution stability). The water / lower alcohol ratio is preferably 5/5 to 95/5.

  The aqueous solution of the present invention is a mixed solvent having a water content of 30% by mass or more in the solvent and water (water content = 100% by mass) as a solute (in the present invention, a metal salt and other additives added as necessary. ) Is dissolved. From the viewpoints of solubility of solutes such as metal salts and solution stability, the water content is preferably 50% by mass or more, and more preferably 70% by mass or more.

  Since the metal salt according to the present invention is not hydrolyzed at room temperature and water can be used as a main solvent, it is preferable in terms of the production process and the environment.

  For example, metal salts such as metal chlorides are severely deteriorated and decomposed in the atmosphere (particularly in the case of gallium, etc.) and strong deliquescence. However, inorganic salts such as nitrates according to the present invention are deliquescent and deteriorated. It is also preferable in terms of manufacturing environment that it is easy to use.

  Among the metal salts according to the present invention, nitrates having the most excellent properties in performance such as degradation, decomposition, and easy dissolution in water and deliquescence are most preferable.

  In the present invention, a solution containing a metal salt is applied onto a substrate to form a thin film containing a metal oxide semiconductor precursor.

  As a method of forming a precursor thin film of a metal oxide semiconductor by applying a solution containing a metal salt on a substrate, a spray coating method, a spin coating method, a blade coating method, a dip coating method, a casting method, a roll Examples include a coating method, a bar coating method, a die coating method, a mist method, a printing method such as a relief printing plate, an intaglio plate, a lithographic printing method, a screen printing method, and an ink jet printing method in a broad sense. Etc. The coating film may be patterned by photolithography, laser ablation, or the like. Among these, the ink jet method, spray coating method, etc. which can apply | coat a thin film are preferable.

  For example, when forming a film using an inkjet method, a semiconductor precursor layer thin film containing a metal salt is formed by dropping a metal salt solution and volatilizing a solvent (water) at about 80 ° C. to 100 ° C. In addition, when dropping the solution, it is preferable that the substrate itself is heated to about 80 ° C. to 150 ° C. because two processes of coating and drying can be performed simultaneously and the film forming property of the precursor film is good.

(Composition ratio of metal)
By the method of the present invention, a metal oxide semiconductor thin film containing a single metal atom or a plurality of metal atoms selected from the metal atoms described above is produced. As the metal oxide semiconductor, any state of single crystal, polycrystal, and amorphous can be used, but an amorphous thin film is preferably used.

  The metal atom contained in the formed metal oxide semiconductor preferably contains any one of indium (In), tin (Sn), and zinc (Zn), as described in the description of the precursor. It is preferable to contain gallium (Ga) or aluminum (Al).

  When preparing a precursor solution containing these metals as components, the preferred metal composition ratio is as follows: a metal (metal A) contained in a salt selected from metal salts of In and Sn, and metal salts of Ga and Al The molar ratio (metal A: metal B: metal C) of metal (metal B = metal C) contained in the metal salt (metal B) contained in the salt selected from the following relational expression: It is preferable to satisfy.

Metal A: Metal B: Metal C = 1: 0.2-1.5: 0-5
It is.

  As the metal salt, nitrate is most preferable. Therefore, the molar ratio (A: B: C) of In, Sn (metal A), Ga, Al (metal B), and Zn (metal C) is as described above. It is preferable to form a precursor thin film containing a metal inorganic salt by coating using a coating solution in which nitrate of each metal is dissolved and formed in a solvent containing water as a main component so as to satisfy the formula.

  Moreover, the film thickness of the thin film containing the metal inorganic salt used as a precursor is 1-200 nm, More preferably, it is 5-100 nm.

(Amorphous oxide)
As the metal oxide semiconductor to be formed, any state of single crystal, polycrystal, and amorphous can be used, but an amorphous thin film is preferably used. Being amorphous can be confirmed by X-ray diffraction or electron diffraction, and can be regarded as amorphous if a diffraction pattern unique to the crystal is not observed.

The electron carrier concentration of an amorphous oxide, which is a metal oxide according to the present invention, formed from a metal compound material that is a precursor of a metal oxide semiconductor only needs to be less than 10 ¹⁸ / cm ³ . The electron carrier concentration is a value when measured at room temperature. The room temperature is, for example, 25 ° C., specifically, a certain temperature appropriately selected from the range of about 0 ° C. to 40 ° C. Note that the electron carrier concentration of the amorphous oxide according to the present invention does not need to satisfy less than 10 ¹⁸ / cm ³ in the entire range of 0 ° C. to 40 ° C. For example, a carrier electron density of less than 10 ¹⁸ / cm ³ may be realized at 25 ° C. Further, when the electron carrier concentration is further reduced to 10 ¹⁷ / cm ³ or less, more preferably 10 ¹⁶ / cm ³ or less, a normally-off TFT can be obtained with a high yield.

  The electron carrier concentration can be measured by Hall effect measurement.

  The film thickness of the semiconductor that is a metal oxide is not particularly limited, but the characteristics of the obtained transistor are often greatly influenced by the film thickness of the semiconductor film, and the film thickness varies depending on the semiconductor. Generally, 1 μm or less, particularly 10 to 300 nm is preferable.

In the present invention, the precursor material (metal salt), composition ratio, production conditions, and the like are controlled so that, for example, the electron carrier concentration is 10 ¹² / cm ³ or more and less than 10 ¹⁸ / cm ³ . More preferably, it is in the range of 10 ¹³ / cm ³ or more and 10 ¹⁷ / cm ³ or less, and more preferably 10 ¹⁵ / cm ³ or more and 10 ¹⁶ / cm ³ or less.

  In the present invention, the temperature at which the semiconductor precursor layer is heated can be arbitrarily set so that the temperature of the thin film surface containing the precursor material is in the range of 100 ° C to 250 ° C. The temperature of the thin film surface, the temperature of the substrate, etc. can be measured by a surface thermometer using a thermocouple, a radiation thermometer capable of measuring the radiation temperature, a fiber thermometer, or the like. The heating temperature is adjusted by controlling both the external heating temperature and electromagnetic wave irradiation, such as the temperature of the heater that performs external heating, the output of electromagnetic waves, the irradiation time, and the number of irradiations. The time for heating the precursor material can be set arbitrarily, but is preferably in the range of 1 second to 60 minutes from the viewpoint of the characteristics of the electronic device and production efficiency. More preferably, it is 5 minutes to 30 minutes.

  Irradiation of electromagnetic waves does not need to be performed in synchronism with external heating at all, and there may be a portion that overlaps somewhere, such as heating in advance and irradiating electromagnetic waves at different timings.

  By using the method of the present invention in combination with external heating and electromagnetic wave irradiation, semiconductor conversion treatment can be performed at a relatively low temperature and in a short time.

  Note that formation of the metal oxide can be detected by ESCA or the like, and conditions under which the conversion to the semiconductor is sufficiently performed can be selected in advance.

(Electromagnetic radiation)
In the present invention, examples of the electromagnetic wave include ultraviolet light (laser), millimeter wave, microwave, and the like, but it is difficult to apply the ultraviolet light laser to a large area. Therefore, microwave is preferable, and microwave irradiation is preferable. After forming the precursor layer thin film (layer) of the metal oxide semiconductor, the thin film is subjected to heat treatment from the outside and irradiated with electromagnetic waves, particularly microwaves (frequency 0.3 GHz to 50 GHz).

  As heating temperature, 100 to 250 degreeC is preferable. If it is this temperature, a base material with low heat resistance like a resin substrate can be used. Along with the external heating, the microwave output, the irradiation time, and the number of irradiations are controlled so that the temperature of the surface of the thin film containing the precursor becomes 100 ° C. to 250 ° C.

  In general, the microwave refers to an electromagnetic wave having a frequency of 0.3 GHz to 50, and is used in 0.8 GHz and 1.5 GHz bands, 2 GHz bands, amateur radio, aircraft radar, etc. used in mobile communication. .2 GHz band, microwave oven, local radio, 2.4 GHz band used for VICS, 3 GHz band used for ship radar, etc., and 5.6 GHz used for other ETC communications are all electromagnetic waves in the microwave category. is there. In addition, oscillators such as 28 GHz and 50 GHz are available on the market.

  Since substrates such as glass and resin have almost no absorption in the microwave region, the substrate itself hardly generates heat, and only the thin film portion can be selectively heated to be thermally oxidized and converted into a metal oxide semiconductor. Become.

  A metal oxide semiconductor layer with better characteristics can be obtained by using in combination with an ordinary heating method using an oven or a heater block and using electromagnetic wave (microwave) irradiation in combination. When a metal oxide semiconductor is generated from a metal oxide semiconductor precursor material, it is not clear whether there is a direct action of electromagnetic waves on the metal oxide semiconductor precursor material or the metal oxide semiconductor itself. It is presumed that the conversion of the metal oxide semiconductor precursor material into the metal oxide semiconductor is promoted by electromagnetic waves, and side reactions that deteriorate the characteristics are unlikely to occur.

  Further, a method of performing heat treatment from the outside separately from electromagnetic wave irradiation is particularly preferable because of less variation.

  Directly irradiate the semiconductor precursor material thin film with electromagnetic waves, or place a strong electromagnetic wave absorber such as ITO in the vicinity (for example, a gate electrode) and irradiate microwaves to heat the electromagnetic wave absorber. A semiconductor thin film with better performance can be formed in a shorter time than when only the internal heating is used, such as heating the semiconductor precursor material thin film adjacent to.

  Next, a description will be given of a heat source having a substance having a microwave absorbing ability that absorbs electromagnetic waves and generates heat, which can be used as a heat source from the outside, on a substrate.

  As the substance having microwave absorption ability, one is a metal oxide material fine particle, preferably indium oxide, tin oxide, zinc oxide, IZO, ITO, etc., and preferably contains at least an oxide of In and Sn. . These substances having electromagnetic wave absorbing ability are formed on, for example, a resin substrate or a ceramic substrate, and can be used as an external heat source by using it together with microwave irradiation.

For example, an ITO film obtained by doping tin with indium oxide preferably has an In: Sn atomic number ratio of the obtained ITO film of preferably 100: 0.5 to 100: 10. In addition, an FTO film obtained by doping tin oxide with fluorine (Sn: F atomic ratio in the range of 100: 0.01 to 100: 50), an In ₂ O ₃ —ZnO-based amorphous conductive film (In: Zn For example, the atomic ratio of 100: 50 to 100: 5 can be used. The atomic ratio can be determined by XPS measurement.

  The formation of conductive thin films composed of these metal oxide material fine particles having electromagnetic wave absorbing ability can be achieved by using vacuum deposition, sputtering, etc., metal alkoxides such as indium and tin, and organometallic compounds such as alkyl metals. Can be formed by a plasma CVD method. It can also be produced by a coating method such as a sol-gel method using a metal alkoxide such as indium or tin. A thin film of a substance having electromagnetic wave absorbing ability can also be obtained in combination with a photoresist or other known patterning method.

  As the substance having electromagnetic wave absorbing ability, as described above, when a thin film such as IZO or ITO formed by vapor deposition, sputtering, plasma CVD, or the like is used, it is preferably fired after film formation. The substrate is preferably formed on a substrate such as glass or ceramic.

  Also, the metal oxide material fine particles can be patterned by a coating method such as an ink jet method.

  These metal oxide fine particles can also be obtained by, for example, heating and low-temperature sintering from a gel-like material obtained by heating a solution with adjusted pH. The paint (ink) in which the metal oxide fine particles thus obtained are dispersed in an appropriate solvent such as water or alcohol is highly dispersed and fine particles, and clogging due to agglomeration etc. even when used for coating or inkjet or printing methods. Does not occur.

  Such particles are preferably in the range of 5 nm to 50 nm.

These are commercially available and can also be obtained directly from the market. Examples thereof include NanoTek Slurry ITO, SnO _{2 and the} like manufactured by CI Kasei Co., Ltd.

  When these fine particle dispersions are used as precursors, a material such as ITO can be easily patterned by a coating method such as an ink jet method, and the surface temperature of a thin film is 200 to 600 ° C. By low temperature heat treatment or sintering, crystallization occurs and a thin film of metal oxide fine particles having electromagnetic wave absorbing ability is obtained.

  The metal oxide semiconductor thin film formed from the metal salt according to the present invention can be used in various semiconductor elements such as transistors and diodes, electronic circuits, etc., and a solution of a precursor material is applied on a substrate. Thus, a metal oxide semiconductor material layer can be manufactured by a low-temperature process, and can be preferably applied to the manufacture of a semiconductor element such as a thin film transistor element (TFT element) using a resin substrate.

  The metal oxide semiconductor of the present invention can be used for a diode or a photosensor. For example, a Schottky diode or a photodiode can be manufactured by overlapping a metal thin film made of an electrode material described later.

(Element structure)
FIG. 3 is a diagram showing a typical element configuration of a thin film transistor element using a metal oxide semiconductor according to the present invention.

  3A to 3F are cross-sectional views illustrating some structural examples of thin film transistors. In FIG. 3, a semiconductor layer 101 made of a metal oxide semiconductor is connected to a source electrode 102 and a drain electrode 103 as a channel.

  In FIG. 6A, a source electrode 102 and a drain electrode 103 are formed on a support 106 by the method of the present invention, and this is used as a base material (substrate) to form a semiconductor layer 101 between both electrodes. A field effect thin film transistor is formed by forming a gate insulating layer 105 thereon and further forming a gate electrode 104 thereon. FIG. 4B shows the semiconductor layer 101 formed between the electrodes in FIG. 5A so as to cover the entire surface of the electrode and the support using a coating method or the like. (C) shows a structure in which the semiconductor layer 101 is first formed on the support 106, the source electrode 102, the drain electrode 103, and the insulating layer 105 are formed, and then the gate electrode 104 is formed. In the present invention, the semiconductor layer may be formed by the method of the present invention.

  In FIG. 4D, after the gate electrode 104 is formed on the support 106, the gate insulating layer 105 is formed, the source electrode 102 and the drain electrode 103 are formed thereon, and the semiconductor layer 101 is formed between the electrodes. Form. In addition, the configuration as shown in FIGS.

  FIG. 4 is a schematic equivalent circuit diagram showing an example of a thin film transistor sheet in which a plurality of thin film transistor elements are arranged.

  The thin film transistor sheet 120 has a large number of thin film transistor elements 124 arranged in a matrix. 121 is a gate bus line of the gate electrode of each thin film transistor element 124, and 122 is a source bus line of the source electrode of each thin film transistor element 124. An output element 126 is connected to the drain electrode of each thin film transistor element 124. The output element 126 is, for example, a liquid crystal or an electrophoretic element, and constitutes a pixel in the display device. In the illustrated example, a liquid crystal is shown as an output element 126 by an equivalent circuit composed of a resistor and a capacitor. Reference numeral 125 denotes a storage capacitor, 127 denotes a vertical drive circuit, and 128 denotes a horizontal drive circuit. The present invention can be used to manufacture the source, drain electrode, gate electrode, and the like of each transistor element in the thin film transistor sheet 120, as well as the gate bus line, source bus line, and circuit wiring.

  Next, each element constituting the TFT element will be described.

(electrode)
In the thin film transistor using the metal oxide semiconductor of the present invention, as a conductive material used for an electrode such as a source electrode, a drain electrode, and a gate electrode constituting the element, the conductive material has conductivity at a practical level as an electrode. Well, not particularly limited, platinum, gold, silver, nickel, chromium, copper, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, tin oxide Antimony, indium tin oxide (ITO), fluorine-doped zinc oxide, zinc, carbon, graphite, glassy carbon, silver paste and carbon paste, lithium, beryllium, sodium, magnesium, potassium, calcium, scandium, titanium, manganese, zirco Um, gallium, niobium, sodium, sodium-potassium alloy, magnesium, lithium, aluminum, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide mixture, lithium / aluminum mixture, etc. Is used.

  Moreover, as a conductive material, a conductive polymer, metal fine particles, or the like can be suitably used. As the dispersion containing metal fine particles, for example, a known conductive paste may be used, but a dispersion containing metal fine particles having a particle diameter of 1 nm to 50 nm, preferably 1 nm to 10 nm is preferable. In order to form an electrode from metal fine particles, the above-described method can be used in the same manner, and the metal described above can be used as the material of the metal fine particles.

(Method for forming electrodes, etc.)
As a method for forming an electrode, a method for forming an electrode using a known photolithographic method or a lift-off method, using a conductive thin film formed by a method such as vapor deposition or sputtering using the above as a raw material, or a metal foil such as aluminum or copper There is a method in which a resist is formed and etched by thermal transfer, ink jet or the like. Alternatively, a conductive polymer solution or dispersion, a dispersion containing metal fine particles, or the like may be directly patterned by an ink jet method, or may be formed from a coating film by lithography or laser ablation. Further, a method of patterning a conductive ink or conductive paste containing a conductive polymer or metal fine particles by a printing method such as relief printing, intaglio printing, planographic printing, or screen printing can also be used.

  As a method of forming an electrode such as a source, drain, or gate electrode, a gate, or a source bus line without patterning a metal thin film using a photosensitive resin such as etching or lift-off, there is a method by an electroless plating method. Are known.

  Regarding the method of forming an electrode by electroless plating, as described in Japanese Patent Application Laid-Open No. 2004-158805, a liquid containing a plating catalyst that causes electroless plating by acting with a plating agent on a portion where an electrode is provided After patterning, for example, by a printing method (including inkjet printing), a plating agent is brought into contact with a portion where an electrode is provided. If it does so, electroless plating will be performed to the said part by the contact of the said catalyst and a plating agent, and an electrode pattern will be formed.

  The application of the electroless plating catalyst and the plating agent may be reversed, and the pattern formation may be performed either. However, a method of forming a plating catalyst pattern and applying the plating agent to this is preferable.

  As the printing method, for example, screen printing, planographic printing, letterpress printing, intaglio printing, printing by ink jet printing, or the like is used.

(Gate insulation layer)
Although various insulating films can be used as the gate insulating layer of the thin film transistor of the present invention, an inorganic oxide film having a high relative dielectric constant is particularly preferable. Inorganic oxides include silicon oxide, aluminum oxide, tantalum oxide, titanium oxide, tin oxide, vanadium oxide, barium strontium titanate, barium zirconate titanate, lead zirconate titanate, lead lanthanum titanate, strontium titanate, Examples thereof include barium titanate, barium magnesium fluoride, bismuth titanate, strontium bismuth titanate, strontium bismuth tantalate, bismuth tantalate niobate, and yttrium trioxide. Of these, silicon oxide, aluminum oxide, tantalum oxide, and titanium oxide are preferable. Inorganic nitrides such as silicon nitride and aluminum nitride can also be suitably used.

  Examples of the method for forming the film include a vacuum process, a molecular beam epitaxial growth method, an ion cluster beam method, a low energy ion beam method, an ion plating method, a CVD method, a sputtering method, an atmospheric pressure plasma method, and a spray process. Examples include wet processes such as coating methods, spin coating methods, blade coating methods, dip coating methods, casting methods, roll coating methods, bar coating methods, die coating methods, and other methods such as printing and ink jet patterning. Can be used depending on the material.

  The wet process is a method of applying and drying a liquid in which fine particles of inorganic oxide are dispersed in an arbitrary organic solvent or water using a dispersion aid such as a surfactant as required, or an oxide precursor, for example, A so-called sol-gel method in which a solution of an alkoxide body is applied and dried is used.

  Of these, the atmospheric pressure plasma method described above is preferable.

  It is also preferable that the gate insulating layer (film) is composed of an anodized film or the anodized film and an insulating film. The anodized film is preferably sealed. The anodized film is formed by anodizing a metal that can be anodized by a known method.

  Examples of the metal that can be anodized include aluminum and tantalum, and the anodizing method is not particularly limited, and a known method can be used.

  Examples of organic compound films include polyimides, polyamides, polyesters, polyacrylates, photo-radical polymerization-type, photo-cation polymerization-type photo-curing resins, copolymers containing acrylonitrile components, polyvinyl phenol, polyvinyl alcohol, novolac resins, etc. Can also be used.

  An inorganic oxide film and an organic oxide film can be laminated and used together. The thickness of these insulating films is generally 50 nm to 3 μm, preferably 100 nm to 1 μm.

(substrate)
Various materials can be used as the support material constituting the substrate. For example, ceramic substrates such as glass, quartz, aluminum oxide, sapphire, silicon nitride, silicon carbide, silicon, germanium, gallium arsenide, gallium phosphide. In addition, a semiconductor substrate such as gallium nitrogen, paper, and non-woven fabric can be used. In the present invention, the support is preferably made of a resin, for example, a plastic film sheet can be used. Examples of plastic films include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), and cellulose. Examples include films made of triacetate (TAC), cellulose acetate propionate (CAP), and the like. By using a plastic film, the weight can be reduced as compared with the case of using a glass substrate, the portability can be improved, and the resistance to impact can be improved.

  An element protective layer can be provided on the thin film transistor element of the present invention. Examples of the protective layer include the inorganic oxides and inorganic nitrides described above, and it is preferable to form the protective layer by the atmospheric pressure plasma method described above.

  Hereinafter, embodiments of the method for manufacturing a thin film transistor using the oxide semiconductor thin film according to the present invention will be specifically described.

Example 1
The production of a thin film transistor by the thin film transistor manufacturing method of the present invention will be described with reference to cross-sectional schematic diagrams of each step in FIG.

<Production of Thin Film Transistor 1>
A polyimide resin film (200 μm) was used as the support 301, and first, a corona discharge treatment was performed thereon under the condition of 50 W / m ² / min. Thereafter, an undercoat layer was formed in order to improve adhesion as follows.

(Formation of undercoat layer)
A coating solution having the following composition was applied to a dry film thickness of 2 μm, dried at 90 ° C. for 5 minutes, and then cured for 4 seconds from a distance of 10 cm under a 60 W / cm high-pressure mercury lamp.

Dipentaerythritol hexaacrylate monomer 60g
Dipentaerythritol hexaacrylate dimer 20g
Dipentaerythritol hexaacrylate trimer or higher component 20g
Diethoxybenzophenone UV initiator 2g
Silicone surfactant 1g
75g of methyl ethyl ketone
Methyl propylene glycol 75g
Further, a silicon oxide film having a thickness of 50 nm was provided on the layer by continuous atmospheric pressure plasma treatment under the following conditions, and these layers were used as an undercoat layer (barrier layer) 310 (FIG. 5 (1)). As the atmospheric pressure plasma processing apparatus, an apparatus according to FIG. 2 was used.

(Used gas)
Inert gas: helium 98.25% by volume
Reactive gas: oxygen gas 1.5 volume%
Reactive gas: Tetraethoxysilane vapor (bubbled with helium gas) 0.25% by volume
(Discharge conditions)
Discharge output: 10 W / cm ²
(Electrode condition)
The electrode is coated with 1 mm of alumina by ceramic spraying on a stainless steel jacket roll base material having cooling means with cooling water, and then a solution obtained by diluting tetramethoxysilane with ethyl acetate is applied and dried, and then sealed by ultraviolet irradiation. This is a roll electrode having a dielectric (relative permittivity of 10) that has been subjected to hole treatment and has a smooth surface and an Rmax of 5 μm, and is grounded. On the other hand, as the application electrode, a hollow rectangular stainless steel pipe was coated with the same dielectric as described above under the same conditions.

(Formation of gate electrode)
Next, a gate electrode is formed. An aluminum film having a thickness of 300 nm was formed over the entire surface by sputtering, and then etched by photolithography to form the gate electrode 302. (Fig. 5 (1))
(Formation of gate insulating film)
Next, at a film temperature of 200 ° C., a silicon oxide film having a thickness of 250 nm was provided using the same atmospheric pressure plasma processing apparatus under the same conditions as described above to form a gate insulating film 303. (Fig. 5 (2))
The surface temperature was measured with a surface thermometer using a thermocouple.

(Formation of semiconductor layer)
Next, the substrate was immersed in a toluene solution (0.1% by mass, 60 ° C.) in which octyltrichlorosilane (C ₈ H ₁₇ SiCl ₃ ) (OTS) was dissolved, then rinsed with toluene, and further an ultrasonic cleaner. After the treatment for 10 minutes, the entire surface of the gate insulating film reacted with OTS to be surface-treated by drying. A monomolecular film made of octyltrichlorosilane is formed by the surface treatment, but this monomolecular film is represented by the surface treatment layer 308 for convenience (FIG. 5 (3)).

  The surface-treated silicon oxide film was irradiated with ultraviolet light having a wavelength of 254 nm from a low-pressure mercury lamp through a photomask M having a light transmission portion corresponding to the semiconductor channel region (FIG. 5 (4)). Thereby, the surface of the exposure part was decomposed | disassembled and the surface treatment part was hydrophilized. The decomposition product was removed by washing with ethanol, and the surface of the gate insulating layer 303 corresponding to the channel region was exposed (FIG. 5 (5)).

  Next, a 10% by mass aqueous solution in which indium nitrate, zinc nitrate, and gallium nitrate are mixed at a metal ratio of 1: 1: 1 (gram atomic ratio) is used as an ink, and a semiconductor layer pattern is formed using a piezo ink jet device. Ink was discharged according to (substantially gate electrode pattern) to form a semiconductor precursor material thin film 306 ′ (FIG. 5 (6)). An average film thickness of the precursor material thin film 306 ′ formed by heat treatment at 100 ° C. and drying was 50 nm.

  Next, heat treatment was performed on a hot plate heated to 200 ° C. In addition, microwave irradiation was simultaneously performed from the support side during the heat treatment. In other words, microwaves (2.45 GHz) were irradiated at an output of 500 W under atmospheric conditions. The treatment for a total of 15 minutes was performed by controlling the output of microwave irradiation so that the temperature of the precursor thin film surface was maintained at 200 ° C.

  The precursor material thin film 306 ′ is converted into an oxide semiconductor by heat treatment from outside and microwave irradiation, and an IGZO-based oxide semiconductor layer 306 is formed on the gate insulating film so as to face the gate electrode (FIG. 5 ( 7)).

  The surface temperature was measured with a surface thermometer using a thermocouple.

(Formation of protective film)
Further, the substrate was immersed for 10 minutes in a toluene solution (0.1 mass%, 60 ° C.) in which octyltrichlorosilane (C ₈ H ₁₇ SiCl ₃ ) (OTS) was dissolved, then rinsed with toluene, and further an ultrasonic cleaner. The surface of the oxide semiconductor layer 306 was reacted with OTS to form a monomolecular film (surface treatment). Similarly, this monomolecular film was represented by the surface treatment layer 308 (FIG. 5 (8)).

  Next, the protective film formation region was irradiated with ultraviolet light of 254 nm using a mask covering the region other than the protective film formation region on the semiconductor layer (FIG. 5 (9)). The surface treatment layer 308 in the protective film formation region on the semiconductor layer was decomposed to expose the semiconductor layer. Note that since the width of the protective film forms the channel length (distance between the source electrode 304 and the drain electrode 305), the exposure region is adjusted so that the width of the protective film is 15 μm so that only the channel region of the semiconductor layer is exposed (FIG. 5 (10)).

  Next, perhydropolysilazane (Aquamica NP110 (registered trademark)) xylene solution on the oxide semiconductor layer 306 is applied to a predetermined region in the oxide semiconductor layer using a piezo-type ink jet apparatus as described above. (FIG. 5 (11)). Subsequently, this was heat-treated at 200 ° C. for 20 minutes to convert it into a silicon dioxide thin film layer to form a protective layer 307 (FIG. 5 (12)). The thickness of the protective layer was 200 nm.

(Formation of source and drain electrodes)
Next, the remaining surface treatment layer 308 is decomposed by oxygen plasma treatment under the following conditions using the same atmospheric pressure plasma treatment apparatus as described above, and the gate insulating layer 303 and the oxide semiconductor layer 306 are exposed at portions other than the protective layer. (FIG. 5 (13)).

(Used gas)
Inert gas: Nitrogen gas 98% by volume
Reactive gas: 2% by volume of oxygen gas
(Discharge conditions)
High frequency power supply: 13.56 MHz
Discharge output: 10 W / cm ²
Next, a silver fine particle dispersion (CCI-300 (silver content 20 mass%) manufactured by Cabot) is ejected from a piezo-type inkjet head, and printing is performed on the source electrode and drain electrode portions including the exposed regions of the semiconductor layer. gave. Next, heat treatment was performed at 200 ° C. for 30 minutes to form a source electrode 304 and a drain electrode 305 (FIG. 2 (14)). Each size was 40 μm wide, 100 μm long (channel width), and 100 nm thick, and the distance (channel length) between the source electrode 304 and the drain electrode 305 was 20 μm. A thin film transistor 1 was prepared.

<Creation of thin film transistor 2>
In the thin film transistor 1, instead of using a hot plate when forming the semiconductor layer, a substrate on which a precursor material thin film was formed on a ceramic plate with an ITO film was placed, and microwave irradiation was performed from the support side. That is, under atmospheric conditions, microwave (2.45 GHz) is radiated at an output of 500 W, and the microwave irradiation output is controlled so that the temperature of the precursor thin film surface is maintained at 200 ° C. for a total of 15 minutes. Went.

  The following ceramic substrates with ITO films were used.

<Creation of glass substrate with ITO film>
That is, a cleaned glass substrate (thickness 0.5 mm) is introduced into a vacuum chamber, and a DC magnetron is used using an ITO target (indium: tin = 95: 5 (molar ratio)) with a SnO ₂ content of 10% by mass. An ITO film having a thickness of 100 nm was formed on the glass substrate by sputtering (conditions: substrate support temperature 250 ° C., oxygen pressure 1 × 10 ⁻³ Pa).

  The precursor material was converted into an oxide semiconductor by heat treatment from outside and microwave irradiation, and an IGZO-based oxide semiconductor layer 306 was formed on the gate insulating film so as to face the gate electrode (FIG. 5 (7)). .

<Preparation of Thin Film Transistor 3>
In the thin film transistor 1, instead of using aluminum as a gate electrode, a sample in which an ITO film was used was prepared. That is, an ITO film having a thickness of 300 nm was formed on one surface by sputtering, and then etched by photolithography to form the gate electrode 302 (FIG. 5 (1)).

  Specifically, the ITO pattern was formed by masking the region corresponding to the gate electrode with a resist, and then immersing it in a 2.5% hydrochloric acid aqueous solution to remove the exposed ITO film. Thereafter, the resist was removed by immersion in methyl ethyl ketone, followed by washing with water and drying.

  After forming the gate electrode with an ITO film, in the formation of the semiconductor layer, the precursor material thin film 306 'was subjected to heat treatment only by microwave irradiation from the support side. In other words, microwaves (2.45 GHz) were irradiated at an output of 500 W under atmospheric conditions. The treatment for a total of 15 minutes was performed by controlling the output of microwave irradiation so that the temperature of the precursor thin film surface was maintained at 200 ° C. Conversion to a metal oxide semiconductor was performed by absorption and heat generation of microwaves by the ITO film used for the gate electrode.

<Production of Thin Film Transistor 4>
In the thin film transistor 1, the precursor material thin film 306 ′ was converted into a metal oxide semiconductor by heat treatment only by heat treatment of a heated hot plate without using microwave irradiation. The temperature was the temperature of the precursor material thin film surface, and the treatment was performed at 200 ° C. for 15 minutes.

  The characteristics of the four types of thin film transistors 1 to 4 manufactured by the above method and having different conversion methods to oxide semiconductors were evaluated using a semiconductor parameter analyzer (4155 manufactured by Agilent). The thin film transistors 1 to 4 showed n-type enhancement operation.

With respect to the thin film transistors 1 to 4 (3 types each), the drain bias is set to 10 V, and the increase (transfer characteristic) of the drain current when the gate bias is swept from −30 V to +30 V is observed. From the saturation region, the mobility (cm ² / Vs) was estimated. Further, the gate voltage Vth (threshold) at the rise of the drain current and the common logarithm value (on / off ratio) of the ratio between the maximum value and the minimum value of the drain current were evaluated, and the results are shown in Table 1. The threshold value Vth is a gate bias value obtained by extrapolating √Id = 0 to the square root √Id of the drain current value with respect to the gate bias.

  In addition, for the thin film transistors 1 to 4 described above, the mobility was measured for samples that were repeatedly created at n = 30, and the standard deviation of the mobility value variation at n = 30 was calculated.

  The results are shown in Table 1.

  What performed the heat processing and microwave irradiation which concern on this invention simultaneously shows a favorable result in a mobility, a threshold value, and on / off ratio compared with the thing of only external heating. In addition, it can be seen that the variation in the semiconductor characteristics is particularly reduced in those heated from the outside. When the ITO gate was changed to an external heater, the variation in the elements was reduced and the mobility was improved.

DESCRIPTION OF SYMBOLS 1, C board | substrate 2,104 Gate electrode 3,105 Gate insulating layer 4,102 Source electrode 5,103 Drain electrode 101 Semiconductor layer 106 Support body 10 Thin-film transistor sheet 11 Gate bus line 12 Source bus line 14 Thin-film transistor element 15 Storage capacitor 16 Output Element 17 Vertical drive circuit 18 Horizontal drive circuit 301 Support 302 Gate electrode 303 Gate insulating film 304 Source electrode 305 Drain electrode 306 Oxide semiconductor layer 6, 306 ′ Precursor material thin film H Heat block P Ceramic plate

Claims (11)

  In the method for manufacturing a metal oxide semiconductor, in which a semiconductor precursor layer formed on a substrate is subjected to heat treatment to form a metal oxide semiconductor, the semiconductor precursor layer is irradiated with electromagnetic waves simultaneously with the heat treatment. A method for producing a metal oxide semiconductor.   The method for producing a metal oxide semiconductor according to claim 1, wherein the electromagnetic wave is a microwave.   The method for producing a metal oxide semiconductor according to claim 1, wherein a temperature of the heat treatment is 100 ° C. to 250 ° C. 3.   The method for producing a metal oxide semiconductor according to any one of claims 1 to 3, wherein the heat treatment uses a heat source from outside the substrate.   The method for producing a metal oxide semiconductor according to claim 4, wherein the heat source used for the heat treatment contains a metal oxide, and the heat treatment is performed by heat generated by the metal oxide absorbing electromagnetic waves. .   The method for producing a metal oxide semiconductor according to claim 1, wherein the semiconductor precursor layer is formed from a coating film of a solution or dispersion liquid of a precursor material.   The method for producing a metal oxide semiconductor according to claim 6, wherein the solution of the precursor material is an aqueous solution.   The method for producing a metal oxide semiconductor according to claim 6 or 7, wherein the precursor material contains any one of In, Zn, and Sn.   The method for producing a metal oxide semiconductor according to any one of claims 6 to 8, wherein the precursor material contains one of Ga and Al.   A metal oxide semiconductor produced using the method for producing a metal oxide semiconductor according to claim 1.   A thin film transistor using the metal oxide semiconductor according to claim 10.

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