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WO2014112368A1 - スパッタリングターゲット、酸化物半導体薄膜及びそれらの製造方法 - Google Patents

スパッタリングターゲット、酸化物半導体薄膜及びそれらの製造方法 Download PDF

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WO2014112368A1
WO2014112368A1 PCT/JP2014/000148 JP2014000148W WO2014112368A1 WO 2014112368 A1 WO2014112368 A1 WO 2014112368A1 JP 2014000148 W JP2014000148 W JP 2014000148W WO 2014112368 A1 WO2014112368 A1 WO 2014112368A1
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Prior art keywords
thin film
oxide semiconductor
sputtering
sputtering target
semiconductor thin
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PCT/JP2014/000148
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English (en)
French (fr)
Japanese (ja)
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望 但馬
一晃 江端
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出光興産株式会社
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Priority to JP2014557404A priority Critical patent/JP6353369B2/ja
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/08—Oxides
    • C23C14/086—Oxides of zinc, germanium, cadmium, indium, tin, thallium or bismuth
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/453—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zinc, tin, or bismuth oxides or solid solutions thereof with other oxides, e.g. zincates, stannates or bismuthates
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/3407—Cathode assembly for sputtering apparatus, e.g. Target
    • C23C14/3414—Metallurgical or chemical aspects of target preparation, e.g. casting, powder metallurgy
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
    • H10D30/00—Field-effect transistors [FET]
    • H10D30/60—Insulated-gate field-effect transistors [IGFET]
    • H10D30/67—Thin-film transistors [TFT]
    • H10D30/674—Thin-film transistors [TFT] characterised by the active materials
    • H10D30/6755—Oxide semiconductors, e.g. zinc oxide, copper aluminium oxide or cadmium stannate
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
    • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/3217—Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
    • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/3286—Gallium oxides, gallates, indium oxides, indates, thallium oxides, thallates or oxide forming salts thereof, e.g. zinc gallate
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
    • C04B2235/80—Phases present in the sintered or melt-cast ceramic products other than the main phase

Definitions

  • the present invention relates to a sputtering target for producing an oxide thin film such as an oxide semiconductor or a transparent conductive film, a thin film produced using the target, a thin film transistor including the thin film, and a method for producing them.
  • TFTs thin film transistors
  • LCD liquid crystal display devices
  • EL electroluminescence display devices
  • FED field emission displays
  • a driving voltage is applied to the display elements.
  • TFTs are often used as switching elements for driving display devices.
  • a semiconductor layer channel layer which is a main member of a field effect transistor
  • silicon semiconductor compound is most widely used as a material for a semiconductor layer (channel layer) which is a main member of a field effect transistor.
  • a silicon single crystal is used for a high-frequency amplifying element or an integrated circuit element that requires high-speed operation.
  • an amorphous silicon semiconductor is used for a liquid crystal driving element or the like because of a demand for a large area.
  • an amorphous silicon thin film can be formed at a relatively low temperature, its switching speed is slower than that of a crystalline thin film, so when used as a switching element for driving a display device, it may not be able to follow the display of high-speed movies. is there.
  • amorphous silicon having a mobility of 0.5 to 1 cm 2 / Vs could be used, but when the resolution is SXGA, UXGA, QXGA or higher, 2 cm 2 / Mobility greater than Vs is required.
  • the driving frequency is increased in order to improve the image quality, higher mobility is required.
  • the crystalline silicon-based thin film has a high mobility
  • problems such as requiring a large amount of energy and the number of processes for manufacturing, and a problem that it is difficult to increase the area.
  • laser annealing using a high temperature of 800 ° C. or higher and expensive equipment is necessary.
  • a crystalline silicon-based thin film is difficult to reduce costs such as a reduction in the number of masks because the element configuration of a TFT is usually limited to a top gate configuration.
  • an oxide semiconductor thin film is manufactured by sputtering using a target (sputtering target) made of an oxide sintered body.
  • Patent Documents 1, 2, and 3 a target made of a compound having a homologous crystal structure represented by general formulas In 2 Ga 2 ZnO 7 and InGaZnO 4 is known (Patent Documents 1, 2, and 3).
  • sintering density relative density
  • a reduction treatment at a high temperature is necessary after sintering in order to reduce the resistance of the target. there were.
  • Patent Document 4 a thin film transistor using an amorphous oxide semiconductor film made of indium oxide and zinc oxide without containing gallium has also been proposed (Patent Document 4).
  • Patent Document 4 a thin film transistor using an amorphous oxide semiconductor film made of indium oxide and zinc oxide without containing gallium has also been proposed.
  • Patent Document 4 there is a problem that the normally-off operation of the TFT cannot be realized unless the oxygen partial pressure during film formation is increased.
  • Patent Document 5 a sputtering target in which aluminum oxide is added to indium oxide and zinc oxide is disclosed (Patent Document 5).
  • the crystal phase of the target has not been studied, and the mobility of a thin film manufactured using the target is as low as less than 5 cm 2 / Vs, and indium oxide, zinc oxide, and aluminum oxide materials are originally used. I could't draw the mobility I had.
  • the crystal phases of indium oxide, zinc oxide, and aluminum oxide target preferable as a sputtering target for an oxide semiconductor have not been clarified.
  • An object of the present invention is to provide a high-density and low-resistance sputtering target containing indium element (In), zinc element (Zn), and aluminum element (Al). Another object of the present invention is to provide a sputtering target capable of realizing a TFT having high mobility and high reliability.
  • the present inventors have intensively studied and contain a bixbite structure compound containing indium element (In), zinc element (Zn) and aluminum element (Al) and represented by In 2 O 3 .
  • a homologous structure compound represented by In 2 O 3 (ZnO) m (m is an integer) have a relative density of 98% or more and a specific resistance of 10 m ⁇ cm or less, and a thin film produced using the target
  • the present invention was completed by finding that a TFT using a channel layer has a high field effect mobility of 5 cm 2 / Vs or more and high reliability.
  • the following sputtering target and the like are provided.
  • 3. 3 The sputtering target according to 1 or 2, wherein an atomic ratio of the indium element, zinc element and aluminum element satisfies the following formulas (1) to (3).
  • An oxide semiconductor thin film is formed by a sputtering method using the sputtering target according to any one of 1 to 5 in an atmosphere of a mixed gas containing one or more selected from water vapor, oxygen gas, and nitrous oxide gas and a rare gas.
  • 10. 10 The method for producing an oxide semiconductor thin film according to 8 or 9, wherein a ratio of water vapor contained in the mixed gas is 0.1% to 25% in terms of partial pressure ratio. 11.
  • the oxide semiconductor thin film is formed by sequentially transporting the substrate to a position facing three or more targets arranged in parallel in the vacuum chamber at a predetermined interval, and from each AC power source to each target. In the case of alternately applying a negative potential and a positive potential, at least one of the outputs from the AC power supply is switched between two or more targets that are branched and connected while switching the target to which the potential is applied. 12.
  • 13. 13 The method for producing an oxide semiconductor thin film according to 12, wherein the AC power density of the AC power source is 3 W / cm 2 or more and 20 W / cm 2 or less.
  • 14 14. The method for producing an oxide semiconductor thin film according to 12 or 13, wherein the frequency of the AC power source is 10 kHz to 1 MHz.
  • the thin-film transistor of 15 or 16 whose field effect mobility is 5 cm ⁇ 2 > / Vs or more. 18.
  • a display device comprising the thin film transistor according to any one of 15 to 17.
  • the present invention it is possible to provide a high-density and low-resistance sputtering target containing indium element (In), zinc element (Zn), and aluminum element (Al).
  • Example 2 is an X-ray chart of a sintered body obtained in Example 1.
  • 3 is an X-ray chart of a sintered body obtained in Example 2.
  • 4 is an X-ray chart of a sintered body obtained in Example 3.
  • 6 is an X-ray chart of a sintered body obtained in Example 4. It is a figure which shows the sputtering device used for one Embodiment of this invention.
  • the sputtering target of the present invention contains an indium element (In), a zinc element (Zn), and an aluminum element (Al), and a homologous structure compound represented by In 2 O 3 (ZnO) m (m is an integer) and In 2. It includes a bixbyte structure represented by O 3 .
  • the bixbite structure and homologous structure can be confirmed by X-ray diffraction.
  • Bixbyte is also referred to as rare earth oxide C-type or Mn 2 O 3 (I) -type oxide.
  • the stoichiometric ratio is M 2 X 3 (M is a cation, X is an anion, usually an oxygen ion), and one unit cell is composed of 16 molecules of M 2 X 3 , a total of 80 atoms (M is 32, X is 48) Yes.
  • the bixbite structure is an X-ray diffraction pattern, and is a No. of JCPDS (Joint Committee of Powder Diffraction Standards) database. A peak pattern of 06-0416 or a similar (shifted) pattern is shown.
  • the bixbite structure compound also includes a substitutional solid solution in which atoms and ions in the crystal structure are partially substituted with other atoms, and an interstitial solid solution in which other atoms are added to interstitial positions.
  • the homologous structure is a crystal structure composed of a “natural superlattice” structure having a long period obtained by superposing several crystal layers of different substances.
  • the crystal cycle or thickness of each thin film layer is on the order of nanometers, depending on the combination of the chemical composition of these layers and the thickness of the layers, it differs from the properties of a single substance or a mixed crystal in which each layer is uniformly mixed.
  • Unique characteristics can be obtained.
  • the crystal structure of the homologous phase can be confirmed, for example, because the X-ray diffraction pattern of the powder obtained by pulverizing the target matches the crystal structure X-ray diffraction pattern of the homologous phase assumed from the composition ratio. Specifically, it can be confirmed from the coincidence with the crystal structure X-ray diffraction pattern of the homologous phase obtained from a JCPDS card or The Inorganic Crystal Structure Database (ICSD).
  • ICSD Inorganic Crystal Structure Database
  • Examples of the oxide crystal having a homologous structure include an oxide crystal represented by RAO 3 (MO) m .
  • R and A are positive trivalent metal elements, and examples thereof include In, Ga, Al, Fe, and B.
  • M is a positive divalent metal element, and examples thereof include Zn and Mg.
  • m is, for example, an integer, preferably 0.1 to 10, more preferably 0.5 to 7, and further preferably 1 to 5.
  • Al is dissolved in a homologous structure compound represented by In 2 O 3 (ZnO) m (m is an integer).
  • the sputtering target contains In 2-x Al x O 3 (ZnO) m (x 0 ⁇ satisfy x ⁇ 2) represented by the non-stoichiometric oxides.
  • Whether or not Al is dissolved in the homologous structure compound represented by In 2 O 3 (ZnO) m (m is an integer) can be confirmed from the axial length of the crystal calculated from the X-ray diffraction pattern.
  • the crystal axis length (a-axis, b-axis, c-axis) of the homologous structure compound crystal represented by In 2 O 3 (ZnO) m (m is an integer) calculated from the X-ray diffraction pattern is X in the JCPDS database or ICSD.
  • the homologous structure of In 2 Zn 3 O 6 shows an ICSD # 162450 peak pattern or a similar (shifted) pattern by X-ray diffraction.
  • b 3.352 mm
  • c 42.488 mm
  • the homologous structure of InAlZn 3 O 6 is X-ray diffraction. It shows a peak pattern of 40-0260 or a similar (shifted) pattern.
  • the crystal axis lengths a, b, and c of the homologous structure compound crystal represented by In 2 O 3 (ZnO) 2 calculated from the X-ray diffraction pattern are 3.281 ⁇ ⁇ a ⁇ 3.352 ⁇ , 3.281 ⁇ ⁇ b ⁇ .
  • ZnO zinc oxide
  • the atomic ratio of each element preferably satisfies the following formulas (1) to (3). 0.10 ⁇ In / (In + Zn + Al) ⁇ 0.70 (1) 0.10 ⁇ Zn / (In + Zn + Al) ⁇ 0.90 (2) 0.01 ⁇ Al / (In + Zn + Al) ⁇ 0.30 (3) (In the formula, In, Zn, and Al each indicate an atomic ratio of each element in the sputtering target.)
  • the concentration of In is preferably 0.10 ⁇ In / (In + Zn + Al) ⁇ 0.70.
  • the amount of In element [In / (In + Zn + Al)] is more preferably 0.15 to 0.70, and further preferably 0.20 to 0.65.
  • the Zn concentration is preferably 0.10 ⁇ Zn / (In + Zn + Al) ⁇ 0.90.
  • the amount of Zn element [Zn / (In + Zn + Al)] is more preferably 0.15 to 0.80, and further preferably 0.20 to 0.70.
  • the concentration of Al is preferably 0.01 ⁇ Al / (In + Zn + Al) ⁇ 0.30.
  • the amount of Al element [Al / (In + Zn + Al)] is more preferably 0.02 to 0.30, and further preferably 0.02 to 0.25.
  • the atomic ratio of each element contained in the sputtering target can be determined by quantitative analysis of the contained elements using an inductively coupled plasma emission spectrometer (ICP-AES). Specifically, when a solution sample is atomized with a nebulizer and introduced into an argon plasma (about 6000 to 8000 ° C.), the elements in the sample are excited by absorbing thermal energy, and orbital electrons are excited from the ground state. Move to the orbit. These orbital electrons move to a lower energy level orbit in about 10 ⁇ 7 to 10 ⁇ 8 seconds. At this time, the energy difference is emitted as light to emit light. Since this light shows a wavelength (spectral line) unique to the element, the presence of the element can be confirmed by the presence or absence of the spectral line (qualitative analysis).
  • ICP-AES inductively coupled plasma emission spectrometer
  • the sample concentration can be obtained by comparing with a standard solution having a known concentration (quantitative analysis). After identifying the elements contained in the qualitative analysis, the content is obtained by quantitative analysis, and the atomic ratio of each element is obtained from the result.
  • the metal element contained in the sputtering target is substantially composed of In, Zn, and Al, and may contain other inevitable impurities as long as the effects of the present invention are not impaired.
  • “substantially” means that the effect as a sputtering target is attributed to the above In, Zn, and Al, or 95 wt% to 100 wt% (preferably 98 wt% to 100 wt%) of the metal element of the sputtering target. % Or less) means In, Zn and Al.
  • the sputtering target of the present invention preferably has a relative density of 98% or more.
  • the relative density is preferably 98% or more.
  • the relative density is a density calculated relative to the theoretical density calculated from the weighted average.
  • the density calculated from the weighted average of the density of each raw material is the theoretical density, which is defined as 100%.
  • the target surface may be blackened or abnormal discharge may occur if the relative density is less than 98%.
  • the relative density is more preferably 98.5% or more, and even more preferably 99% or more.
  • the relative density can be calculated from the actual density and the theoretical density measured by the Archimedes method.
  • the relative density is preferably 100% or less. When it is 100% or less, it is possible to prevent the metal particles from being generated in the sintered body and the generation of the lower oxide, and it is not necessary to strictly adjust the oxygen supply amount during film formation.
  • the density can be adjusted by performing a post-treatment step such as a heat treatment operation under a reducing atmosphere after sintering.
  • a reducing atmosphere an atmosphere of argon, nitrogen, hydrogen, or a mixed gas atmosphere thereof is used.
  • the sputtering target of the present invention preferably has a relative density of 98% or more and a bulk specific resistance of 10 m ⁇ cm or less. Thereby, when sputtering the sputtering target of this invention, generation
  • the sputtering target of the present invention can form a high-quality oxide semiconductor thin film efficiently, inexpensively and with energy saving.
  • a bulk specific resistance can be measured by the method as described in an Example, for example.
  • the bulk specific resistance is, for example, 0.01 ⁇ cm or more.
  • the maximum grain size of the crystal in the sputtering target of the present invention is desirably 8 ⁇ m or less. Generation of nodules can be prevented when the crystal has a particle size of 8 ⁇ m or less.
  • the cutting speed varies depending on the direction of the crystal plane, and irregularities are generated on the target surface.
  • the size of the unevenness depends on the crystal grain size present in the sputtering target. If the crystal grain size is small, the unevenness of the sputtering target becomes small, and nodules are unlikely to occur.
  • the maximum grain size of these sputtering target crystals is the center point (one place) of the circle and the center point and the peripheral part on two center lines orthogonal to the center point.
  • the central point (one location) and the intermediate point (4) between the central point and the corner on the diagonal of the quadrangle is measured, and the average value of the particle sizes of the maximum particles present in each of these five locations is To express.
  • the particle size is measured for the major axis of the crystal grains.
  • the crystal grains can be observed with a scanning electron microscope (SEM).
  • the manufacturing method of the sputtering target of the present invention includes the following three steps. (1) Mixing step of obtaining a mixture by mixing at least indium element (In), zinc element (Zn), and aluminum element (Al) (2) Molding step of molding the mixture to obtain a molded body (3) Oxygen-containing Sintering process to sinter the molded body in an atmosphere
  • the raw material compound is not particularly limited and is a compound containing In, Zn and Al, It is preferable to use a compound whose aggregate can have the following atomic ratio. 0.10 ⁇ In / (In + Zn + Al) ⁇ 0.70 (1) 0.10 ⁇ Zn / (In + Zn + Al) ⁇ 0.90 (2) 0.01 ⁇ Al / (In + Zn + Al) ⁇ 0.30 (3) (In the formula, In, Zn, and Al each indicate an atomic ratio of each element in the sputtering target.)
  • the raw material is preferably a powder.
  • the raw material is preferably a mixed powder of indium oxide, zinc oxide and aluminum oxide.
  • a single metal is used as a raw material
  • a combination of indium oxide, zinc oxide and aluminum metal is used as a raw material powder
  • aluminum metal particles are present in the obtained sintered body, and the target surface is formed during film formation.
  • the metal particles may not be melted and released from the target, and the composition of the obtained film and the composition of the sintered body may be greatly different.
  • the average particle diameter of the raw material powder is preferably 0.1 ⁇ m to 1.2 ⁇ m, more preferably 0.1 ⁇ m to 1.0 ⁇ m or less.
  • the average particle diameter of the raw material powder can be measured with a laser diffraction type particle size distribution apparatus or the like.
  • An oxide containing three powders is used as a raw material powder, and these are prepared at a ratio satisfying the above formulas (1) to (3).
  • the mixing method will be described together with the following step (2).
  • step (1) and the molding method in step (2) are not particularly limited, and can be performed using known methods.
  • an aqueous solvent is blended with a raw material powder containing a mixed powder of oxides containing indium oxide powder, zinc oxide and aluminum oxide powder, and the resulting slurry is mixed for 12 hours or more. Granulate, and then put this granulated product into a mold and mold it.
  • a wet or dry ball mill, vibration mill, bead mill, or the like can be used.
  • a bead mill mixing method is most preferable because the crushing efficiency of the agglomerates is high in a short time and the additive is well dispersed.
  • the mixing time by the ball mill is preferably 15 hours or more, more preferably 19 hours or more. This is because if the mixing time is insufficient, a high resistance compound such as Al 2 O 3 may be formed in the finally obtained sintered body.
  • the pulverization and mixing time by the bead mill varies depending on the size of the apparatus and the amount of slurry to be processed, but is appropriately adjusted so that the particle size distribution in the slurry is all uniform at 1 ⁇ m or less. Further, when mixing, it is preferable to add an arbitrary amount of a binder and mix them at the same time.
  • a binder polyvinyl alcohol, vinyl acetate, or the like can be used.
  • granulated powder is obtained from the raw material powder slurry.
  • rapid drying granulation it is preferable to perform rapid drying granulation.
  • a spray dryer is widely used as an apparatus for rapid drying granulation. Since specific drying conditions are determined by various conditions such as the slurry concentration of the slurry to be dried, the temperature of hot air used for drying, and the amount of air, it is necessary to obtain optimum conditions in advance.
  • the sedimentation speed varies depending on the specific gravity difference of the raw material powder, so that separation of In 2 O 3 powder, ZnO powder and Al 2 O 3 powder occurs, and there is a possibility that uniform granulated powder cannot be obtained.
  • a sintered body is produced using this non-uniform granulated powder, Al 2 O 3 or the like is present inside the sintered body, which may cause abnormal discharge in sputtering.
  • the granulated powder is usually molded by a die press or cold isostatic press (CIP) at a pressure of, for example, 1.2 ton / cm 2 or more to obtain a molded body.
  • a sintering process which sinters a molded object in oxygen-containing atmosphere
  • a sintering process contains a temperature rising process, a calcination process, and a holding process. Further, in the middle of the temperature raising step, a calcining step of maintaining the temperature in the range of 700 to 900 ° C. for 1 to 5 hours is included. This is preferable because the density of the target is likely to increase and generation of nodules during sputtering can be further suppressed. Moreover, it can prevent that a target shift
  • the heating rate during sintering is usually 8 ° C./min or less, preferably 4 ° C./min or less, more preferably 3 ° C./min or less, and further preferably 2 ° C./min or less.
  • the temperature rising rate is 8 ° C./min or less, cracks are hardly generated.
  • sintering is performed by holding at a sintering temperature of 1200 to 1650 ° C. for 5 to 50 hours (holding step).
  • the sintering temperature is preferably 1300 to 1600 ° C.
  • the sintering time is preferably 10 to 20 hours.
  • the sintering temperature is 1200 ° C. or more and the sintering time is 5 hours or more, Al 2 O 3 and the like can be prevented from being formed inside the target.
  • the firing temperature is 1650 ° C. or less and the firing time is 50 hours or less, an increase in the average crystal grain size can be prevented by significant crystal grain growth, and the production efficiency is not lowered.
  • a pressure sintering method such as hot press, oxygen pressurization, hot isostatic pressurization and the like can be employed in addition to the atmospheric pressure sintering method.
  • a normal pressure sintering method from the viewpoints of reducing manufacturing costs, possibility of mass production, and easy production of large sintered bodies.
  • the compact is sintered in an air atmosphere or an oxidizing gas atmosphere, preferably an oxidizing gas atmosphere.
  • the oxidizing gas atmosphere is preferably an oxygen gas atmosphere.
  • the oxygen gas atmosphere is preferably an atmosphere having an oxygen concentration of, for example, 10 to 100% by volume.
  • a sintered compact density can be made higher by introduce
  • a reduction process may be provided as necessary.
  • the reduction method include a method using a reducing gas, vacuum firing, or reduction using an inert gas.
  • a reducing gas hydrogen, methane, carbon monoxide, a mixed gas of these gases and oxygen, or the like can be used.
  • reduction treatment by firing in an inert gas nitrogen, argon, a mixed gas of these gases and oxygen, or the like can be used.
  • the temperature during the reduction treatment is usually 100 to 800 ° C., preferably 200 to 800 ° C.
  • the reduction treatment time is usually 0.01 to 10 hours, preferably 0.05 to 5 hours.
  • an aqueous solvent is blended into a raw material powder containing a mixed powder of indium oxide powder, zinc oxide powder, and aluminum oxide powder, and the resulting slurry is mixed for 12 hours or more. Drying and granulating, and then molding this granulated product in a mold, and then molding the resulting molded product in an oxygen-containing atmosphere with an average heating rate of 8 ° C./min or less for 1 to 5 hours
  • the sintered body can be obtained by maintaining the temperature in the range of 700 to 900 ° C. and calcining at 1200 to 1650 ° C. for 5 to 50 hours.
  • the sputtering target of the present invention can be obtained by processing the sintered body obtained above.
  • a sputtering target material can be obtained by cutting the sintered body into a shape suitable for mounting on a sputtering apparatus, and a sputtering target can be obtained by bonding the target material to a backing plate.
  • the sintered body is ground with, for example, a surface grinder to obtain a material having a surface roughness Ra of 0.5 ⁇ m or less.
  • the sputter surface of the target material may be further mirror-finished so that the average surface roughness Ra may be 1000 angstroms or less.
  • Mirror surface processing can be performed using a known polishing technique such as mechanical polishing, chemical polishing, mechanochemical polishing (a combination of mechanical polishing and chemical polishing). For example, polishing to # 2000 or more with a fixed abrasive polisher (polishing liquid: water), or lapping with loose abrasive lapping (abrasive: SiC paste, etc.), and then lapping by changing the abrasive to diamond paste Can be obtained.
  • a polishing method is not particularly limited.
  • the surface of the target material is preferably finished with a 200 to 10,000 diamond grindstone, particularly preferably with a 400 to 5,000 diamond grindstone.
  • a diamond grindstone larger than No. 200 and smaller than No. 10,000 is used, the target material becomes difficult to break.
  • the target material has a surface roughness Ra of 0.5 ⁇ m or less and has a non-directional ground surface. If Ra is 0.5 ⁇ m or less and the directionality of the polished surface is lost, abnormal discharge or particles can be prevented from occurring.
  • Air blow or running water washing can be used for the cleaning treatment.
  • This ultrasonic cleaning is effective by performing multiple oscillations at a frequency of 25 to 300 kHz.
  • it is preferable to perform ultrasonic cleaning by multiplying twelve frequencies in 25 kHz increments between frequencies of 25 to 300 kHz.
  • the thickness of the target material is usually 2 to 20 mm, preferably 3 to 12 mm, particularly preferably 4 to 6 mm.
  • a sputtering target can be obtained by bonding the target material obtained as described above to a backing plate. Further, a plurality of target materials may be attached to one backing plate to substantially serve as one target.
  • the oxide semiconductor thin film of the present invention can be obtained by forming a film by a sputtering method using the above-described sputtering target of the present invention.
  • the oxide semiconductor thin film of the present invention is composed of indium, zinc, aluminum, and oxygen, and usually has an atomic ratio of (1) to (3). 0.10 ⁇ In / (In + Zn + Al) ⁇ 0.70 (1 ) 0.10 ⁇ Zn / (In + Zn + Al) ⁇ 0.90 (2) 0.01 ⁇ Al / (In + Zn + Al) ⁇ 0.30 (3) (In the formula, In, Zn, and Al each indicate an atomic ratio of each element in the oxide semiconductor thin film.)
  • the thin film when the amount of In element is 0.10 or more, the thin film can be used as a semiconductor without significantly reducing the carrier concentration of the thin film.
  • the amount of In element when the amount of In element is 0.70 or less, the carrier concentration of the obtained thin film can be prevented from becoming too high, and the thin film can be used as a semiconductor.
  • the amount of Zn element when the amount of Zn element is 0.10 or more, the obtained film can be stabilized as an amorphous film.
  • the amount of Zn element when the amount of Zn element is 0.90 or less, it is possible to prevent the dissolution rate of the obtained thin film in the wet etchant from becoming too fast, and wet etching becomes easy.
  • the amount of Zn element [Zn / (In + Zn + Al)] is more preferably 0.15 to 0.80, and further preferably 0.20 to 0.70.
  • the oxygen partial pressure during film formation can be kept low. Since the Al element has a strong bond with oxygen, the oxygen partial pressure during film formation can be reduced. In addition, reliability can be improved when a channel layer is formed and applied to a TFT. On the other hand, when the amount of Al element is 0.30 or less, it is possible to prevent mobility from being lowered when a channel layer is formed and applied to a TFT.
  • a DC sputtering method having a high deposition rate can be applied.
  • the sputtering target of the present invention can be applied to an RF sputtering method, an AC sputtering method, and a pulsed DC sputtering method in addition to the DC sputtering method, and enables sputtering without abnormal discharge.
  • the oxide semiconductor thin film can also be produced by a vapor deposition method, an ion plating method, a pulse laser vapor deposition method, or the like using the above sputtering target.
  • a mixed gas of a rare gas such as argon and an oxidizing gas can be used.
  • the oxidizing gas include O 2 , CO 2 , O 3 , water vapor (H 2 O), and N 2 O.
  • the sputtering gas is preferably a mixed gas containing a rare gas and one or more selected from water vapor, oxygen gas, and nitrous oxide gas, and more preferably a mixed gas containing at least a rare gas and water vapor.
  • the carrier concentration of the oxide semiconductor thin film is usually 10 19 cm ⁇ 3 or less, preferably 10 13 to 10 18 cm ⁇ 3 , more preferably 10 14 to 10 18 cm ⁇ 3 , and particularly preferably 10 13 cm ⁇ 3. 15 to 10 18 / cm ⁇ 3 .
  • the carrier concentration of the oxide semiconductor thin film can be measured by a Hall effect measurement method.
  • the oxygen partial pressure ratio during sputtering film formation is preferably 0.1% or more and 50% or less.
  • a thin film manufactured under a condition where the oxygen partial pressure ratio is 50% or less can prevent the carrier concentration from being excessively lowered. More preferably, the oxygen partial pressure ratio is 0.1% to 30%.
  • the partial pressure ratio of water vapor (water molecules) contained in the sputtering gas (atmosphere) during oxide thin film deposition in the present invention is preferably 0.1 to 25%. Further, when the water partial pressure ratio is 25% or less, a decrease in film density can be suppressed, and an overlap of In 5s orbitals can be prevented from being reduced, so that the mobility is hardly lowered.
  • the partial pressure ratio of water in the atmosphere during sputtering is more preferably 0.7 to 13%, particularly preferably 1 to 6%.
  • the substrate temperature when forming a film by sputtering is preferably 25 to 120 ° C., more preferably 25 to 100 ° C., and particularly preferably 25 to 90 ° C.
  • the substrate temperature at the time of film formation is 120 ° C. or lower, the incorporation of oxygen or the like introduced at the time of film formation does not decrease, and the carrier concentration of the thin film after heating can be reduced to 10 19 / cm ⁇ 3 or lower.
  • the substrate temperature during film formation is higher than 25 ° C., the film density of the thin film is likely to be improved, and the mobility of the TFT is easily improved.
  • the oxide thin film obtained by sputtering is preferably further annealed by holding at 150 to 500 ° C. for 15 minutes to 5 hours.
  • the annealing temperature after film formation is more preferably 200 ° C. or higher and 450 ° C. or lower, and further preferably 250 ° C. or higher and 350 ° C. or lower.
  • the atmosphere during heating is not particularly limited, but from the viewpoint of carrier controllability, an air atmosphere or an oxygen circulation atmosphere is preferable.
  • a lamp annealing device, a laser annealing device, a thermal plasma device, a hot air heating device, a contact heating device, or the like can be used in the presence or absence of oxygen.
  • the distance between the target and the substrate at the time of sputtering is preferably 1 to 15 cm, more preferably 2 to 8 cm in the direction perpendicular to the film formation surface of the substrate.
  • this distance is 1 cm or more, it is possible to prevent the kinetic energy of the target constituent element particles reaching the substrate from becoming too large, and good film characteristics can be obtained. In addition, in-plane distribution of film thickness and electrical characteristics is less likely to occur.
  • the distance between the target and the substrate is 15 cm or less, the kinetic energy of the particles of the target constituent element reaching the substrate does not become too small, a dense film can be obtained, and good semiconductor characteristics can be obtained. it can.
  • the oxide thin film is preferably formed by sputtering in an atmosphere having a magnetic field strength of 300 to 1500 gauss.
  • the magnetic field strength is 300 gauss or more, the plasma density can be increased, and even a high-resistance sputtering target can be sputtered.
  • it is 1500 gauss or less, the controllability of the film thickness and the electrical characteristics in the film is improved.
  • the pressure in the gas atmosphere is not particularly limited as long as the plasma can be stably discharged, but is preferably 0.1 to 3.0 Pa, more preferably 0.1 to 1.5 Pa. Particularly preferred is 0.1 to 1.0 Pa.
  • the sputtering pressure is 3.0 Pa or less, it is possible to prevent the average free process of sputtered particles from being shortened and the density of the thin film from being lowered. Further, when the sputtering pressure is 0.1 Pa or more, it becomes easy to prevent the formation of microcrystals in the film during film formation.
  • the sputtering pressure refers to the total pressure in the system at the start of sputtering after introducing a rare gas such as argon, water vapor, oxygen gas or the like.
  • the oxide semiconductor thin film may be formed by AC sputtering as described below.
  • the substrate is sequentially transported to a position facing three or more targets arranged in parallel at a predetermined interval in the vacuum chamber, and negative and positive potentials are alternately applied to each target from an AC power source. Then, plasma is generated on the target to form a film on the substrate surface.
  • an oxide semiconductor thin film is formed by AC sputtering
  • sputtering is performed in an atmosphere of a mixed gas containing a rare gas and one or more selected from water vapor, oxygen gas, and nitrous oxide gas. It is particularly preferable to perform sputtering in an atmosphere of a mixed gas containing at least a rare gas and water vapor.
  • the film is formed by AC sputtering, it is possible to obtain an oxide layer that is industrially excellent in large area uniformity and to improve the utilization efficiency of the target. Further, when sputtering film formation is performed on a large-area substrate having a side exceeding 1 m, it is preferable to use an AC sputtering apparatus for large-area production as described in, for example, Japanese Patent Application Laid-Open No. 2005-290550.
  • the AC sputtering apparatus described in Japanese Patent Laid-Open No. 2005-290550 includes a vacuum chamber, a substrate holder disposed inside the vacuum chamber, and a sputtering source disposed at a position facing the substrate holder. .
  • FIG. 5 shows a main part of the sputtering source of the AC sputtering apparatus.
  • the sputter source has a plurality of sputter units, each of which has plate-like targets 31a to 31f, and the surfaces to be sputtered of the targets 31a to 31f are sputter surfaces. It arrange
  • Each target 31a to 31f is formed in an elongated shape having a longitudinal direction, each target has the same shape, and edge portions (side surfaces) in the longitudinal direction of the sputtering surface are arranged in parallel with a predetermined interval therebetween. Therefore, the side surfaces of the adjacent targets 31a to 31f are parallel.
  • AC power supplies 17a to 17c are arranged outside the vacuum chamber, and one of the two terminals of each AC power supply 17a to 17c is connected to one of the two adjacent electrodes. The other terminal is connected to the other electrode.
  • Two terminals of each of the AC power supplies 17a to 17c output voltages of positive and negative different polarities, and the targets 31a to 31f are attached in close contact with the electrodes, so that the two adjacent targets 31a to 31f are adjacent to each other.
  • AC voltages having different polarities are applied from the AC power sources 17a to 17c. Therefore, when one of the targets 31a to 31f adjacent to each other is placed at a positive potential, the other is placed at a negative potential.
  • Magnetic field forming means 40a to 40f are disposed on the surface of the electrode opposite to the targets 31a to 31f.
  • Each of the magnetic field forming means 40a to 40f has an elongated ring-shaped magnet whose outer periphery is substantially equal to the outer periphery of the targets 31a to 31f, and a bar-shaped magnet shorter than the length of the ring-shaped magnet.
  • Each ring-shaped magnet is arranged in parallel with the longitudinal direction of the targets 31a to 31f at the position directly behind the corresponding one of the targets 31a to 31f. As described above, since the targets 31a to 31f are arranged in parallel at a predetermined interval, the ring magnets are also arranged at the same interval as the targets 31a to 31f.
  • the AC power density when an oxide target is used in AC sputtering is preferably 3 W / cm 2 or more and 20 W / cm 2 or less.
  • the power density is 3 W / cm 2 or more, the film formation rate is increased, and production is possible economically.
  • a target can prevent a failure
  • a more preferable power density is 3 W / cm 2 to 15 W / cm 2 .
  • the frequency of AC sputtering is preferably in the range of 10 kHz to 1 MHz. When the frequency is 10 kHz or more, the problem of noise hardly occurs. When the frequency is 1 MHz or less, the plasma does not spread too much, and sputtering can be performed at a position other than the desired target position to prevent the uniformity from being impaired.
  • a more preferable frequency of AC sputtering is 20 kHz to 500 kHz. What is necessary is just to select suitably the conditions at the time of sputtering other than the above from what was mentioned above.
  • the oxide semiconductor thin film of the present invention can be used for a thin film transistor, and can be particularly suitably used as a channel layer.
  • the thin film transistor of the present invention has the above-described oxide semiconductor thin film of the present invention as a channel layer, its element structure is not particularly limited, and various known element structures can be adopted.
  • the thickness of the channel layer in the thin film transistor of the present invention is usually 10 to 300 nm, preferably 20 to 250 nm, more preferably 30 to 200 nm, still more preferably 35 to 120 nm, and particularly preferably 40 to 80 nm.
  • the film thickness of the channel layer is 10 nm or more, it becomes easy to make the film thickness uniform when the film is formed in a large area, and the characteristics of the manufactured TFT are less likely to be in-plane.
  • the film thickness is 300 nm or less, the film formation time does not become too long.
  • the channel layer in the thin film transistor of the present invention is usually used in an N-type region, but a PN junction transistor or the like in combination with various P-type semiconductors such as a P-type Si-based semiconductor, a P-type oxide semiconductor, and a P-type organic semiconductor. It can be used for various semiconductor devices.
  • the thin film transistor of the present invention preferably includes a protective film on the channel layer.
  • the protective film in the thin film transistor of the present invention preferably contains at least SiN x . Since SiN x can form a dense film as compared with SiO 2 , it has an advantage of a high TFT deterioration suppressing effect. Note that x is an arbitrary number, and the stoichiometric ratio of SiN x may not be constant.
  • the protective film may be, for example, SiO 2 , Al 2 O 3 , Ta 2 O 5 , TiO 2 , MgO, ZrO 2 , CeO 2 , K 2 O, Li 2 O, Na 2 O, Rb 2 O, Sc 2 O 3 , Y 2 O 3 , HfO 2 , CaHfO 3 , PbTiO 3 , BaTa 2 O 6 , Sm 2 O 3 , SrTiO 3, or an oxide such as AlN can be included.
  • the field effect mobility of the thin film transistor of the present invention is preferably 5 cm 2 / Vs or more, more preferably 10 cm 2 / Vs or more.
  • the field effect mobility is, for example, 100 cm 2 / Vs or less.
  • the oxide semiconductor thin film containing indium element (In), zinc element (Zn), and aluminum element (Al) of the present invention contains Al, so that the reduction resistance by the CVD process is improved, and a protective film is produced. By this process, the back channel side is not easily reduced, and SiN x can be used as a protective film.
  • the channel layer is preferably subjected to ozone treatment, oxygen plasma treatment, nitrogen dioxide plasma treatment or nitrous oxide plasma treatment.
  • ozone treatment oxygen plasma treatment, nitrogen dioxide plasma treatment or nitrous oxide plasma treatment.
  • Such treatment may be performed at any timing after the channel layer is formed and before the protective film is formed, but is preferably performed immediately before the protective film is formed. By performing such pretreatment, generation of oxygen defects in the channel layer can be suppressed.
  • the threshold voltage may shift and the reliability of the TFT may be reduced.
  • a thin film transistor usually includes a substrate, a gate electrode, a gate insulating layer, an organic semiconductor layer (channel layer), a source electrode, and a drain electrode.
  • the channel layer is as described above, and a known material can be used for the substrate.
  • the material for forming the gate insulating film in the thin film transistor of the present invention is not particularly limited, and a commonly used material can be arbitrarily selected. Specifically, for example, SiO 2, SiN x, Al 2 O 3, Ta 2 O 5, TiO 2, MgO, ZrO 2, CeO 2, K 2 O, Li 2 O, Na 2 O, Rb 2 O, Compounds such as Sc 2 O 3 , Y 2 O 3 , HfO 2 , CaHfO 3 , PbTiO 3 , BaTa 2 O 6 , SrTiO 3 , Sm 2 O 3 , and AlN can be used.
  • SiO 2 , SiN x , Al 2 O 3 , Y 2 O 3 , HfO 2 and CaHfO 3 are preferable, and SiO 2 , SiN x , HfO 2 and Al 2 O 3 are more preferable.
  • the gate insulating film can be formed by, for example, a plasma CVD (Chemical Vapor Deposition) method.
  • a gate insulating film is formed by plasma CVD and a channel layer is formed on the gate insulating film, hydrogen in the gate insulating film may diffuse into the channel layer, leading to deterioration in channel layer quality and TFT reliability. is there.
  • the gate insulating film may be subjected to ozone treatment, oxygen plasma treatment, nitrogen dioxide plasma treatment or nitrous oxide plasma treatment before forming the channel layer. preferable. By performing such pretreatment, it is possible to prevent deterioration of the channel layer film quality and TFT reliability.
  • the gate insulating film may have a structure in which two or more insulating films made of different materials are stacked.
  • the gate insulating film may be crystalline, polycrystalline, or amorphous, but is preferably polycrystalline or amorphous that can be easily manufactured industrially.
  • each of the drain electrode, the source electrode, and the gate electrode in the thin film transistor of the present invention there are no particular limitations on the material for forming each of the drain electrode, the source electrode, and the gate electrode in the thin film transistor of the present invention, and a commonly used material can be arbitrarily selected.
  • transparent electrodes such as indium tin oxide (ITO), indium zinc oxide, ZnO, SnO 2 , metal electrodes such as Al, Ag, Cu, Cr, Ni, Mo, Au, Ti, Ta, or these An alloy metal electrode can be used.
  • the drain electrode, the source electrode, and the gate electrode may have a multilayer structure in which two or more different conductive layers are stacked.
  • a good conductor such as Al or Cu may be sandwiched with a metal having excellent adhesion such as Ti or Mo.
  • the thin film transistor of the present invention can be applied to various integrated circuits such as a field effect transistor, a logic circuit, a memory circuit, and a differential amplifier circuit. Further, in addition to the field effect transistor, it can be applied to an electrostatic induction transistor, a Schottky barrier transistor, a Schottky diode, and a resistance element.
  • a field effect transistor in addition to the field effect transistor, it can be applied to an electrostatic induction transistor, a Schottky barrier transistor, a Schottky diode, and a resistance element.
  • known structures such as a bottom gate, a bottom contact, and a top contact can be adopted without limitation.
  • the bottom gate structure is advantageous because high performance can be obtained as compared with thin film transistors of amorphous silicon or ZnO.
  • the bottom gate configuration is preferable because it is easy to reduce the number of masks at the time of manufacturing, and it is easy to reduce the manufacturing cost for uses such as a large display.
  • the thin film transistor of the present invention can be suitably used for a display device.
  • a channel etch type bottom gate thin film transistor is particularly preferable.
  • a channel-etched bottom gate thin film transistor has a small number of photomasks at the time of a photolithography process, and can produce a display panel at a low cost.
  • a channel-etched bottom gate structure and a top contact structure thin film transistor are particularly preferable because they have good characteristics such as mobility and are easily industrialized.
  • Examples 1 to 4 [Production of sintered body] The following oxide powder was used as a raw material powder.
  • the average particle diameter of the oxide powder was measured with a laser diffraction particle size distribution analyzer SALD-300V (manufactured by Shimadzu Corporation), and the median diameter D50 was used as the average particle diameter.
  • Indium oxide powder average particle size 0.98 ⁇ m
  • Zinc oxide powder Average particle size 0.96 ⁇ m
  • Aluminum oxide powder Average particle size 0.98 ⁇ m
  • the above powder was weighed so as to have the atomic ratio (percentage) shown in Table 1, and after uniformly pulverizing and mixing, a molding binder was added and granulated.
  • the raw material grains were uniformly filled in a mold and subjected to pressure molding with a cold press machine at a press pressure of 140 MPa.
  • the obtained molded body was sintered in a sintering furnace at the sintering temperature and sintering time shown in Table 1 to obtain a sintered body.
  • an oxygen atmosphere was used, and the others were in the air (atmosphere).
  • the temperature was increased from 300 ° C. to 800 ° C. at 1 ° C./min, and from 800 ° C. to the sintering temperature was increased at 1 ° C./min.
  • As the calcination step a step of holding at 800 ° C. for 3 hours was included.
  • the cooling rate after the sintering time was 15 ° C./min.
  • the relative density of the obtained sintered body was calculated from the measured density and the theoretical density measured by the Archimedes method. The results are shown in Table 1. It was confirmed that the sintered bodies of Examples 1 to 4 had a relative density of 98% or more. Further, the bulk specific resistance (conductivity) of the obtained sintered body was measured based on the four-probe method (JIS R 1637) using a resistivity meter (Made by Mitsubishi Chemical Corporation, Loresta). The results are shown in Table 1. As shown in Table 1, the bulk specific resistance of the sintered bodies of Examples 1 to 4 was 10 m ⁇ cm or less.
  • the X-ray diffraction charts of the sintered bodies obtained in Examples 1 to 4 are shown in FIGS.
  • a homologous structure of In 2 Zn 3 O 6 and a bixbite structure of In 2 O 3 were observed.
  • the crystal structure can be confirmed with a JCPDS card or ICSD.
  • the homologous structure of In 2 Zn 3 O 6 is ICSD # 162450
  • the bixbite structure of In 2 O 3 is JCPDS card no. 06-0416.
  • the axial lengths of the crystal phases attributed to In 2 Zn 3 O 6 from the X-ray diffraction chart are a-axis: 3.332 mm, b-axis: 3.332 mm, and c-axis: 42.252 mm.
  • the axial length of the crystal phase of the homologous structure represented by In 2 Zn 3 O 6 that can be confirmed from ICSD # 162450 is a-axis: 3.35235, b-axis: 3.352 ⁇ , c-axis: 42.488 ⁇ .
  • the axial length of the crystal phase of the homologous structure represented by InAlZn 3 O 6 that can be confirmed from 40-0260 is a-axis: 3.28128, b-axis: 3.281 ⁇ , and c-axis: 41.35 ⁇ . It can be seen that the solid solution in in 2 Zn 3 O 6. From the results of XRD, it was found that also in Examples 2 to 4, a homologous structure compound represented by In 2 Zn 3 O 6 and a bix structure compound represented by In 2 O 3 were included.
  • the homologous structure compound represented by In 2 O 3 (ZnO) m (m is an integer) and the bixbite structure compound represented by In 2 O 3 are formed at the same time. It was found that the sintered body density was 98% and the bulk specific resistance was 10 m ⁇ cm.
  • the axial length of the crystal phase of In 2 O 3 (ZnO) m calculated from the obtained X-ray diffraction chart is the crystal of In 2 O 3 (ZnO) m described in the corresponding JCPDS card or ICSD.
  • the obtained sputtering target having a diameter of 4 inches was mounted on a DC sputtering apparatus, a mixed gas in which water vapor was added to argon gas at a partial pressure ratio of 2% as an atmosphere, a sputtering pressure of 0.4 Pa, a substrate temperature of room temperature, DC 10 kWh continuous sputtering was performed at an output of 400 W. Voltage fluctuations during sputtering were accumulated in a data logger, and the presence or absence of abnormal discharge was confirmed. The results are shown in Table 1.
  • the presence or absence of the abnormal discharge was performed by monitoring the voltage fluctuation and detecting the abnormal discharge.
  • the abnormal discharge was determined when the voltage fluctuation generated during the measurement time of 5 minutes was 10% or more of the steady voltage during the sputtering operation.
  • the steady-state voltage during sputtering operation varies by ⁇ 10% in 0.1 second, a micro arc, which is an abnormal discharge of the sputter discharge, has occurred, and the device yield may decrease, making it unsuitable for mass production. is there.
  • Nodules are measured after sputtering at a total of five points: the center point (one place) of the circular sputtering target and the center point (four places) between the center point and the peripheral part on two center lines orthogonal to the center point.
  • a method of measuring the number average of nodules having a major axis of 20 ⁇ m or more generated in a visual field of 3 mm 2 was observed by observing the change of the target surface 50 times with a stereomicroscope.
  • Table 1 shows the number of nodules generated. No nodules were observed on the surfaces of the sputtering targets of Examples 1 to 4.
  • Comparative Examples 1 and 2 Except that the raw material powder was mixed at the atomic ratio (percentage) shown in Table 1 and sintered at the sintering temperature and sintering time shown in Table 1, a sintered body and a sputtering target were produced in the same manner as in Example 1, evaluated. The results are shown in Table 1. In the sputtering target of Comparative Example 1, abnormal discharge occurred during sputtering, and nodules were observed on the target surface. The sputtering target of Comparative Example 2 had high resistance and could not be sputtered.
  • a ZnO wurtz structure and a ZnAl 2 O 4 spinel structure were observed.
  • the ZnO wurtz structure is ICSD # 57156
  • the spinel structure of ZnAl 2 O 4 is JCPDS card no. It can be confirmed at 05-0669.
  • the sputtering target of Comparative Example 2 bixbyite structure of an In 2 O 3, the corundum structure of Al 2 O 3 was confirmed.
  • In 2 O 3 has a big byte structure of JCPDS card no. 06-0416, the corundum structure of Al 2 O 3 is JCPDS card no. 10-173.
  • the homologous structural compound represented by In 2 O 3 (ZnO) m (m is an integer) and the homologous structural compound represented by In 2 O 3 are not simultaneously observed, and Al 2 O 3 and Since ZnO was observed, it was found that the density of the sintered body decreased and the bulk resistance increased. As a result, it is considered that nodules are generated or sputtering is impossible.
  • Examples 5-8 Manufacture of oxide semiconductor thin films
  • a 4-inch target having the composition shown in Table 2 prepared in Examples 1 to 4 was mounted on a magnetron sputtering apparatus, and a slide glass (# 1737 manufactured by Corning) was mounted as a substrate.
  • An amorphous film having a thickness of 50 nm was formed on the slide glass by a DC magnetron sputtering method.
  • Ar gas, O 2 gas, and water vapor were introduced at a partial pressure ratio (%) shown in Table 2.
  • the sputtering conditions are as follows. -Substrate temperature: 25 ° C (however, Example 6 is 80 ° C) -Ultimate pressure: 8.5 ⁇ 10 ⁇ 5 Pa Atmospheric gas: Ar gas, O 2 gas, water vapor (see Table 2 for partial pressure ratio) ⁇ Sputtering pressure (total pressure): 0.4 Pa -Input power: DC100W ⁇ S (substrate) -T (target) distance: 70 mm
  • the substrate over which the amorphous film was formed was heated in the atmosphere at 300 ° C. for 60 minutes to form an oxide semiconductor film.
  • the glass substrate on which this oxide semiconductor film was formed was set in ResiTest 8300 type (manufactured by Toyo Technica Co., Ltd.), and the Hall effect was evaluated at room temperature. The results are shown in Table 2. ICP-AES analysis confirmed that the atomic ratio of each element contained in the oxide semiconductor thin film was the same as that of the sputtering target.
  • the crystal structure of the thin film formed on the glass substrate was examined using an X-ray diffraction measurement apparatus.
  • a diffraction peak was not observed immediately after deposition of the thin film, and it was confirmed that the film was amorphous. Further, even after heat treatment (annealing) at 300 ° C. for 60 minutes in the atmosphere, no diffraction peak was observed, and it was confirmed to be amorphous.
  • the measurement conditions of XRD are as follows.
  • a conductive silicon substrate with a thermal oxide film having a thickness of 100 nm was used as the substrate.
  • the thermal oxide film functions as a gate insulating film
  • the conductive silicon portion functions as a gate electrode.
  • Sputter deposition was performed under the deposition conditions shown in Table 2 and the above sputtering conditions, and an amorphous thin film with a thickness of 50 nm was formed on the gate insulating film.
  • OFPR # 800 manufactured by Tokyo Ohka Kogyo Co., Ltd.
  • pre-baking 80 ° C., 5 minutes
  • the manufactured thin film transistor was evaluated for field effect mobility ( ⁇ ), S value, and threshold voltage (Vth). These characteristic values were measured using a semiconductor parameter analyzer (4200SCS manufactured by Keithley Instruments Co., Ltd.) at room temperature in a light-shielding environment (in a shield box). Further, transfer characteristics of the manufactured transistor were evaluated with a drain voltage (Vd) of 1 V and a gate voltage (Vg) of ⁇ 15 to 25 V. The results are shown in Table 2. The field effect mobility ( ⁇ ) was calculated from the linear mobility and defined as the maximum value of Vg ⁇ .
  • Comparative Example 3 An oxide semiconductor thin film and a thin film transistor were produced and evaluated in the same manner as in Example 5 using the 4-inch target produced in Comparative Example 1. The film forming conditions and results are shown in Table 2. Note that the sputtering target of Comparative Example 2 had high resistance, and sputtering was impossible. As shown in Table 2, it can be seen that the device of Comparative Example 3 has a field effect mobility of less than 5 cm 2 / Vs, which is significantly lower than those of Examples 5 to 8. In addition, a DC bias stress test was performed on the TFT of Comparative Example 3. The results are shown in Table 2. In the TFT of Comparative Example 3, the threshold voltage fluctuated by 1 V or more, and the characteristic was significantly deteriorated.
  • Examples 9-12 Using a film forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2005-290550, AC sputtering was performed on a 4-inch target having the composition shown in Table 3 manufactured in Examples 1 to 4, and a thin film transistor was manufactured.
  • the film forming conditions are as shown in Table 3.
  • a thin film transistor and a thin film evaluation element were prepared and evaluated in the same manner as in Example 5 except that the source / drain patterning was performed by dry etching. The results are shown in Table 3.
  • AC sputtering was performed using the apparatus shown in FIG.
  • Six targets 31a to 31f having a width of 200 mm, a length of 1700 mm, and a thickness of 10 mm prepared in Examples 1 to 3 were arranged at intervals of 2 mm so that the length directions thereof were parallel as shown in FIG. .
  • the width of the magnetic field forming means 40a to 40f was 200 mm, which is the same as that of the targets 31a to 31f.
  • Ar which is a sputtering gas, and water vapor and / or O 2 were introduced into the system from the gas supply system.
  • the film forming atmosphere was 0.5 Pa
  • the frequency was 10 kHz.
  • the film was formed for 10 seconds, and the thickness of the obtained thin film was measured to be 8 nm.
  • the film formation rate was as high as 48 nm / min and was suitable for mass production. ICP-AES analysis confirmed that the atomic ratio of each element contained in the oxide thin film was the same as that of the sputtering target.
  • the glass substrate with a thin film having a thickness of 50 nm thus obtained was put in an electric furnace, heat-treated in air at 300 ° C. for 60 minutes (in an atmospheric atmosphere), cut into a size of 1 cm 2 , and searched for 4 probes. Hall measurement was performed by the needle method. As a result, the carrier concentration was 7.3 ⁇ 10 17 cm ⁇ 3 , and it was confirmed that the semiconductor was sufficiently semiconductorized. Further, from XRD measurement, it was confirmed that the film was amorphous immediately after deposition of the thin film and amorphous even after heat treatment at 300 ° C. for 60 minutes in air.
  • Comparative Example 4 Oxide semiconductor in the same manner as in Example 9 except that the film formation conditions were changed to those shown in Table 3 using the six targets 200 mm wide, 1700 mm long and 10 mm thick produced in Comparative Example 1. A thin film, a thin film evaluation element and a thin film transistor were prepared and evaluated. The results are shown in Table 3. As shown in Table 3, it can be seen that the device of Comparative Example 4 has a field effect mobility of less than 10 cm 2 / Vs, which is significantly lower than those of Examples 9-12.
  • the sputtering target of the present invention can be used for production of oxide thin films such as oxide semiconductors and transparent conductive films.
  • the oxide thin film of the present invention can be used for a transparent electrode, a semiconductor layer of a thin film transistor, an oxide thin film layer, and the like.

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  • Organic Chemistry (AREA)
  • Ceramic Engineering (AREA)
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  • Structural Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Thin Film Transistor (AREA)
  • Physical Vapour Deposition (AREA)
  • Compositions Of Oxide Ceramics (AREA)
PCT/JP2014/000148 2013-01-15 2014-01-15 スパッタリングターゲット、酸化物半導体薄膜及びそれらの製造方法 WO2014112368A1 (ja)

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JP2017186655A (ja) * 2017-03-01 2017-10-12 Ｊｘ金属株式会社 酸化インジウム−酸化亜鉛系（ｉｚｏ）スパッタリングターゲット及びその製造方法
TWI649293B (zh) * 2016-08-29 2019-02-01 Ｊｘ金屬股份有限公司 Sintered body, sputtering target and manufacturing method thereof
WO2020241227A1 (ja) * 2019-05-30 2020-12-03 株式会社コベルコ科研 酸化物焼結体及びスパッタリングターゲット
JP2020196660A (ja) * 2019-05-30 2020-12-10 株式会社コベルコ科研 酸化物焼結体及びスパッタリングターゲット

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JP2017186655A (ja) * 2017-03-01 2017-10-12 Ｊｘ金属株式会社 酸化インジウム−酸化亜鉛系（ｉｚｏ）スパッタリングターゲット及びその製造方法
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JP2020196660A (ja) * 2019-05-30 2020-12-10 株式会社コベルコ科研 酸化物焼結体及びスパッタリングターゲット

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