WO2014112368A1 - Sputtering target, oxide semiconductor thin film, and production methods for both - Google Patents

Sputtering target, oxide semiconductor thin film, and production methods for both 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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thin film
oxide semiconductor
sputtering
sputtering target
semiconductor thin
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PCT/JP2014/000148
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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/en
Publication of WO2014112368A1 publication Critical patent/WO2014112368A1/en

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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
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof  ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
    • H01L29/76—Unipolar devices, e.g. field effect transistors
    • H01L29/772—Field effect transistors
    • H01L29/78—Field effect transistors with field effect produced by an insulated gate
    • H01L29/786—Thin film transistors, i.e. transistors with a channel being at least partly a thin film
    • H01L29/7869—Thin film transistors, i.e. transistors with a channel being at least partly a thin film having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, 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.

Abstract

A sputtering target containing indium (In), zinc (Zn), and aluminium (Al), and including a bixbite structure compound indicated by In2O3 and a homologous structure compound indicated by In2O3 (ZnO)m (m being an integer).

Description

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Sputtering target, oxide semiconductor thin film, and manufacturing method thereof
　本発明は、酸化物半導体や透明導電膜等の酸化物薄膜作製用のスパッタリングターゲット、そのターゲットを用いて作製される薄膜、その薄膜を含む薄膜トランジスタ及びそれらの製造方法に関する。 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.
　薄膜トランジスタ（ＴＦＴ）等の電界効果型トランジスタは、半導体メモリ集積回路の単位電子素子、高周波信号増幅素子、液晶駆動用素子等として広く用いられており、現在、最も多く実用されている電子デバイスである。なかでも、近年における表示装置のめざましい発展に伴い、液晶表示装置（ＬＣＤ）、エレクトロルミネッセンス表示装置（ＥＬ）、フィールドエミッションディスプレイ（ＦＥＤ）等の各種の表示装置において、表示素子に駆動電圧を印加して表示装置を駆動させるスイッチング素子として、ＴＦＴが多用されている。
　電界効果型トランジスタの主要部材である半導体層（チャネル層）の材料としては、シリコン半導体化合物が最も広く用いられている。一般に、高速動作が必要な高周波増幅素子や集積回路用素子等には、シリコン単結晶が用いられている。一方、液晶駆動用素子等には、大面積化の要求から非晶質性シリコン半導体（アモルファスシリコン）が用いられている。 Field effect transistors such as thin film transistors (TFTs) are widely used as unit electronic elements, high frequency signal amplifying elements, liquid crystal driving elements, etc. for semiconductor memory integrated circuits, and are currently the most widely used electronic devices. . In particular, with the remarkable development of display devices in recent years, in various display devices such as liquid crystal display devices (LCD), electroluminescence display devices (EL), and field emission displays (FED), a driving voltage is applied to the display elements. TFTs are often used as switching elements for driving display devices.
As a material for a semiconductor layer (channel layer) which is a main member of a field effect transistor, a silicon semiconductor compound is most widely used. In general, a silicon single crystal is used for a high-frequency amplifying element or an integrated circuit element that requires high-speed operation. On the other hand, an amorphous silicon semiconductor (amorphous silicon) is used for a liquid crystal driving element or the like because of a demand for a large area.
　アモルファスシリコンの薄膜は、比較的低温で形成できるものの、結晶性の薄膜に比べてスイッチング速度が遅いため、表示装置を駆動するスイッチング素子として使用したときに、高速な動画の表示に追従できない場合がある。具体的に、解像度がＶＧＡである液晶テレビでは、移動度が０．５～１ｃｍ２／Ｖｓのアモルファスシリコンが使用可能であったが、解像度がＳＸＧＡ、ＵＸＧＡ、ＱＸＧＡあるいはそれ以上になると２ｃｍ２／Ｖｓ以上の移動度が要求される。また、画質を向上させるため駆動周波数を上げるとさらに高い移動度が必要となる。 Although 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. Specifically, in a liquid crystal television with a resolution of VGA, 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. Further, when the driving frequency is increased in order to improve the image quality, higher mobility is required.
　一方、結晶性のシリコン系薄膜は、移動度は高いものの、製造に際して多大なエネルギーと工程数を要する等の問題や、大面積化が困難という問題があった。例えば、シリコン系薄膜を結晶化する際に８００℃以上の高温や、高価な設備を使用するレーザーアニールが必要である。また、結晶性のシリコン系薄膜は、通常ＴＦＴの素子構成がトップゲート構成に限定されるためマスク枚数の削減等コストダウンが困難であった。 On the other hand, although the crystalline silicon-based thin film has a high mobility, there are 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. For example, when annealing a silicon-based thin film, laser annealing using a high temperature of 800 ° C. or higher and expensive equipment is necessary. In addition, 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.
　このような問題を解決するために、酸化インジウム、酸化亜鉛及び酸化ガリウムからなる酸化物半導体膜を使用した薄膜トランジスタが検討されている。一般に、酸化物半導体薄膜の作製は酸化物焼結体からなるターゲット（スパッタリングターゲット）を用いたスパッタリングで行われる。 In order to solve such a problem, a thin film transistor using an oxide semiconductor film made of indium oxide, zinc oxide and gallium oxide has been studied. In general, an oxide semiconductor thin film is manufactured by sputtering using a target (sputtering target) made of an oxide sintered body.
　例えば、一般式Ｉｎ２Ｇａ２ＺｎＯ７、ＩｎＧａＺｎＯ４で表されるホモロガス結晶構造を示す化合物からなるターゲットが知られている（特許文献１、２及び３）。
　しかしながら、このターゲットでは焼結密度（相対密度）を上げるために、酸化性雰囲気で焼結する必要があるが、その場合、ターゲットの抵抗を下げるため、焼結後に高温での還元処理が必要であった。また、ターゲットを長期間使用していると得られた膜の特性や成膜速度が大きく変化する、焼結時に異常成長したＩｎＧａＺｎＯ４やＩｎ２Ｇａ２ＺｎＯ７による異常放電が起きる、成膜時にパーティクルの発生が多い等の問題があった。異常放電が頻繁に起きると、プラズマ放電状態が不安定となり、安定した成膜が行われず、膜特性に悪影響を及ぼす。 For example, 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).
However, in order to increase the sintering density (relative density) with this target, it is necessary to sinter in an oxidizing atmosphere. In that case, a reduction treatment at a high temperature is necessary after sintering in order to reduce the resistance of the target. there were. In addition, when the target is used for a long period of time, the characteristics and deposition rate of the obtained film change greatly, abnormal discharge due to abnormal growth of InGaZnO 4 and In 2 Ga 2 ZnO 7 occurs during sintering, and during deposition There was a problem such as generation of particles. If abnormal discharge frequently occurs, the plasma discharge state becomes unstable, and stable film formation is not performed, which adversely affects the film characteristics.
　一方、ガリウムを含まずに、酸化インジウム及び酸化亜鉛からなる非晶質酸化物半導体膜を用いた薄膜トランジスタも提案されている（特許文献４）。
　しかしながら、成膜時の酸素分圧を高くしないとＴＦＴのノーマリーオフ動作を実現できないといった問題があった。 On the other hand, 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).
However, 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.
　また、酸化インジウム、酸化亜鉛に酸化アルミニウムを添加したスパッタリングターゲットが開示されている（特許文献５）。
　しかしながら、ターゲットの結晶相については検討されておらず、そのターゲットを用いて作製された薄膜の移動度が５ｃｍ２／Ｖｓ未満と低移動度であり、酸化インジウム、酸化亜鉛及び酸化アルミニウム材料が本来持っている移動度を引き出せていなかった。
　以上のように、酸化物半導体用スパッタリングターゲットとして好ましい酸化インジウム、酸化亜鉛及び酸化アルミニウムターゲットの結晶相は明らかではなかった。 Further, a sputtering target in which aluminum oxide is added to indium oxide and zinc oxide is disclosed (Patent Document 5).
However, 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 couldn't draw the mobility I had.
As described above, 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.
特開平８－２４５２２０号公報JP-A-8-245220 特開２００７－７３３１２号公報JP 2007-73312 A 国際公開第２００９／０８４５３７号公報International Publication No. 2009/084537 国際公開第２００５／０８８７２６号公報International Publication No. 2005/088726 特開２０１２－５４３３５号公報JP 2012-54335 A
　本発明は、インジウム元素（Ｉｎ）、亜鉛元素（Ｚｎ）及びアルミニウム元素（Ａｌ）を含有し、高密度かつ低抵抗のスパッタリングターゲットを提供することを目的とする。
　また、本発明は、高い移動度と高い信頼性を有するＴＦＴを実現可能なスパッタリングターゲットを提供することを目的とする。 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.
　上記目的を達成するため、本発明者らは鋭意研究を行い、インジウム元素（Ｉｎ）、亜鉛元素（Ｚｎ）及びアルミニウム元素（Ａｌ）を含有し、Ｉｎ２Ｏ３で表されるビックスバイト構造化合物とＩｎ２Ｏ３（ＺｎＯ）ｍ（ｍは整数）で表わされるホモロガス構造化合物とを含むスパッタリングターゲットは、相対密度が９８％以上、比抵抗が１０ｍΩｃｍ以下であり、そのターゲットを用いて作製した薄膜をチャネル層に用いたＴＦＴは電界効果移動度５ｃｍ２／Ｖｓ以上の高移動度、かつ高信頼性を示すことを見出し、本発明を完成させた。 In order to achieve the above object, 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 . And 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 mΩcm 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.
　本発明によれば、以下のスパッタリングターゲット等が提供される。
１．インジウム元素（Ｉｎ）、亜鉛元素（Ｚｎ）及びアルミニウム元素（Ａｌ）を含有し、Ｉｎ２Ｏ３で表されるビックスバイト構造化合物とＩｎ２Ｏ３（ＺｎＯ）ｍ（ｍは整数）で表わされるホモロガス構造化合物を含むスパッタリングターゲット。
２．前記Ｉｎ２Ｏ３（ＺｎＯ）ｍ（ｍは整数）で表わされるホモロガス構造化合物にＡｌが固溶している１に記載のスパッタリングターゲット。
３．前記インジウム元素、亜鉛元素及びアルミニウム元素の原子比が、下記式（１）～（３）を満たす１又は２に記載のスパッタリングターゲット。
　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）
（式中、Ｉｎ、Ｚｎ及びＡｌは、それぞれ、スパッタリングターゲット中における各元素の原子比を示す。）
４．相対密度が９８％以上である１～３のいずれかに記載のスパッタリングターゲット。
５．バルク比抵抗が１０ｍΩｃｍ以下である１～４のいずれかに記載のスパッタリングターゲット。
６．少なくともインジウム元素（Ｉｎ）、亜鉛元素（Ｚｎ）及びアルミニウム元素（Ａｌ）を混合して混合物を得る混合工程、
　前記混合物を成形して成形体を得る成形工程、及び
　前記成形体を焼結する焼結工程を有し、
　前記焼結工程は、酸素含有雰囲気で、７００～９００℃において１～５時間、温度を保持する仮焼き工程を含む、１～５のいずれかに記載のスパッタリングターゲットの製造方法。
７．１～５のいずれかに記載のスパッタリングターゲットを用いて、スパッタリング法により成膜してなる酸化物半導体薄膜。
８．水蒸気、酸素ガス及び亜酸化窒素ガスから選択される１以上と希ガスを含有する混合気体の雰囲気下において、１～５のいずれかに記載のスパッタリングターゲットを用いてスパッタリング法で酸化物半導体薄膜を成膜する酸化物半導体薄膜の製造方法。
９．前記酸化物半導体薄膜の成膜を、少なくとも水蒸気と希ガスを含有する混合気体の雰囲気下において行う８に記載の酸化物半導体薄膜の製造方法。
１０．前記混合気体中に含まれる水蒸気の割合が分圧比で０．１％～２５％である８又は９に記載の酸化物半導体薄膜の製造方法。
１１．前記混合気体中に含まれる酸素ガスの割合が分圧比で０．１％～５０％である８～１０のいずれかに記載の酸化物半導体薄膜の製造方法。
１２．前記酸化物半導体薄膜の成膜を、真空チャンバー内に所定の間隔を置いて並設された３枚以上のターゲットに対向する位置に、基板を順次搬送し、前記各ターゲットに対して交流電源から負電位及び正電位を交互に印加する場合に、前記交流電源からの出力の少なくとも１つを、分岐して接続した２枚以上のターゲットの間で、電位を印加するターゲットの切替を行いながら、ターゲット上にプラズマを発生させて基板表面に成膜するスパッタリング方法で行う８～１１のいずれかに記載の酸化物半導体薄膜の製造方法。
１３．前記交流電源の交流パワー密度が３Ｗ／ｃｍ２以上、２０Ｗ／ｃｍ２以下である１２に記載の酸化物半導体薄膜の製造方法。
１４．前記交流電源の周波数が１０ｋＨｚ～１ＭＨｚである１２又は１３に記載の酸化物半導体薄膜の製造方法。
１５．７に記載の酸化物半導体薄膜をチャネル層として有する薄膜トランジスタ。
１６．７に記載の酸化物半導体薄膜の上に、少なくともＳｉＮｘ（ｘは任意の数値）を含有する保護膜を有する薄膜トランジスタ。
１７．電界効果移動度が５ｃｍ２／Ｖｓ以上である１５又は１６に記載の薄膜トランジスタ。
１８．１５～１７のいずれかに記載の薄膜トランジスタを備える表示装置。 According to the present invention, the following sputtering target and the like are provided.
1. Indium element (In), represented by containing zinc element (Zn) and aluminum element (Al), bixbyite structure compound represented by In 2 O 3 and In 2 O 3 (ZnO) m (m is an integer) A sputtering target containing a homologous structural compound.
2. 2. The sputtering target according to 1, wherein Al is dissolved in a homologous structure compound represented by In 2 O 3 (ZnO) m (m is an integer).
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).
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.)
4). 4. The sputtering target according to any one of 1 to 3, having a relative density of 98% or more.
5. The sputtering target according to any one of 1 to 4, which has a bulk specific resistance of 10 mΩcm or less.
6). A mixing step of mixing at least indium element (In), zinc element (Zn) and aluminum element (Al) to obtain a mixture;
A molding step of forming the mixture to obtain a molded body, and a sintering step of sintering the molded body,
6. The method for producing a sputtering target according to any one of 1 to 5, wherein the sintering step includes a calcining step in which the temperature is maintained at 700 to 900 ° C. for 1 to 5 hours in an oxygen-containing atmosphere.
7. An oxide semiconductor thin film formed by sputtering using the sputtering target according to any one of 1 to 5.
8). 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. A manufacturing method of an oxide semiconductor thin film to be formed.
9. 9. The method for producing an oxide semiconductor thin film according to 8, wherein the oxide semiconductor thin film is formed in an atmosphere of a mixed gas containing at least water vapor 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. 11. The method for producing an oxide semiconductor thin film according to any one of 8 to 10, wherein a ratio of oxygen gas contained in the mixed gas is 0.1% to 50% in terms of partial pressure ratio.
12 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. The method for producing an oxide semiconductor thin film according to any one of 8 to 11, which is performed by a sputtering method in which plasma is generated on a target to form a film on a substrate surface.
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.
A thin film transistor including the oxide semiconductor thin film according to 15.7 as a channel layer.
A thin film transistor including a protective film containing at least SiNx (x is an arbitrary value) on the oxide semiconductor thin film according to 16.7.
17. 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.
　本発明によれば、インジウム元素（Ｉｎ）、亜鉛元素（Ｚｎ）及びアルミニウム元素（Ａｌ）を含有し、高密度かつ低抵抗のスパッタリングターゲットを提供できる。 According to 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).
実施例１で得た焼結体のＸ線チャートである。2 is an X-ray chart of a sintered body obtained in Example 1. 実施例２で得た焼結体のＸ線チャートである。3 is an X-ray chart of a sintered body obtained in Example 2. 実施例３で得た焼結体のＸ線チャートである。4 is an X-ray chart of a sintered body obtained in Example 3. 実施例４で得た焼結体のＸ線チャートである。6 is an X-ray chart of a sintered body obtained in Example 4. 本発明の一実施形態に用いるスパッタリング装置を示す図である。It is a figure which shows the sputtering device used for one Embodiment of this invention.
　以下、本発明のスパッタリングターゲット、酸化物薄膜、薄膜トランジスタ、表示装置及びこれらの製造方法について詳細に説明するが、本発明は下記実施態様及び実施例に限定されるものではない。 Hereinafter, the sputtering target, oxide thin film, thin film transistor, display device, and manufacturing method thereof of the present invention will be described in detail, but the present invention is not limited to the following embodiments and examples.
　本発明のスパッタリングターゲットは、インジウム元素（Ｉｎ）、亜鉛元素（Ｚｎ）及びアルミニウム元素（Ａｌ）を含有し、Ｉｎ２Ｏ３（ＺｎＯ）ｍ（ｍは整数）で表わされるホモロガス構造化合物とＩｎ２Ｏ３で表されるビックスバイト構造を含む。上記ビックスバイト構造及びホモロガス構造はＸ線回折により確認できる。 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.
　ビックスバイト（ｂｉｘｂｙｉｔｅ）は、希土類酸化物Ｃ型又はＭｎ２Ｏ３（Ｉ）型酸化物とも言われる。「透明導電膜の技術」（（株）オーム社出版、日本学術振興会、透明酸化物・光電子材料第１６６委員会編、１９９９）等に開示されている通り、化学量論比がＭ２Ｘ３（Ｍは陽イオン、Ｘは陰イオンで通常酸素イオン）で、一つの単位胞はＭ２Ｘ３１６分子、合計８０個の原子（Ｍが３２個、Ｘが４８個）により構成されている。 Bixbyte is also referred to as rare earth oxide C-type or Mn 2 O 3 (I) -type oxide. As disclosed in “Technology of Transparent Conductive Films” (Ohm Publishing Co., Ltd., Japan Society for the Promotion of Science, Transparent Oxide / Optoelectronic Materials 166th Committee, 1999), 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.
　ビックスバイト構造は、Ｘ線回折で、ＪＣＰＤＳ（Ｊｏｉｎｔ　Ｃｏｍｍｉｔｔｅｅ　ｏｆ　Ｐｏｗｄｅｒ　Ｄｉｆｆｒａｃｔｉｏｎ　Ｓｔａｎｄａｒｄｓ）データベースのＮｏ．０６－０４１６のピークパターンか、又は類似の（シフトした）パターンを示す。
　また、結晶構造中の原子やイオンが一部他の原子で置換された置換型固溶体、他の原子が格子間位置に加えられた侵入型固溶体もビックスバイト構造化合物に含まれる。 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.
　ホモロガス構造とは、異なる物質の結晶層を何層か重ね合わせた長周期を有する「自然超格子」構造から成る結晶構造である。結晶周期ないし各薄膜層の厚さが、ナノメーター程度の場合、これら各層の化学組成や層の厚さの組み合わせによって、単一の物質あるいは各層を均一に混ぜ合わせた混晶の性質とは異なる固有の特性が得られる。そして、ホモロガス相の結晶構造は、例えばターゲットを粉砕したパウダーにおけるＸ線回折パターンが、組成比から想定されるホモロガス相の結晶構造Ｘ線回折パターンと一致することから確認できる。具体的には、ＪＣＰＤＳカードやＴｈｅ　Ｉｎｏｒｇａｎｉｃ　Ｃｒｙｓｔａｌ　Ｓｔｒｕｃｔｕｒｅ　Ｄａｔａｂａｓｅ　（ＩＣＳＤ）から得られるホモロガス相の結晶構造Ｘ線回折パターンと一致することから確認することができる。 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. When 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).
　ホモロガス構造をとる酸化物結晶としては、ＲＡＯ３（ＭＯ）ｍで表される酸化物結晶が挙げられる。ここで、ＲとＡは、正三価の金属元素であり、例えば、Ｉｎ、Ｇａ、Ａｌ、Ｆｅ、Ｂが挙げられる。Ｍは、正二価の金属元素であり、例えば、Ｚｎ、Ｍｇが挙げられる。また、ｍは、例えば、整数であり、好ましくは、０．１～１０、より好ましくは、０．５～７、さらに好ましくは、１～５である。 Examples of the oxide crystal having a homologous structure include an oxide crystal represented by RAO 3 (MO) m . Here, 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. Further, m is, for example, an integer, preferably 0.1 to 10, more preferably 0.5 to 7, and further preferably 1 to 5.
　さらに、Ｉｎ２Ｏ３（ＺｎＯ）ｍ（ｍは整数）で表わされるホモロガス構造化合物にＡｌが固溶していると好ましい。これは、スパッタリングターゲットがＩｎ２－ｘＡｌｘＯ３（ＺｎＯ）ｍ（ｘは０＜ｘ＜２を満たす）で表される、非化学量論的な酸化物を含むことを意味する。この非化学量論的な化合物が形成されることによって、Ａｌ量を厳密に制御しなくても高抵抗なＡｌ２Ｏ３が形成されにくく、低抵抗で高密度なスパッタリングターゲットを製造できる。 Furthermore, it is preferable that Al is dissolved in a homologous structure compound represented by In 2 O 3 (ZnO) m (m is an integer). This means that the sputtering target contains In 2-x Al x O 3 (ZnO) m (x 0 <satisfy x <2) represented by the non-stoichiometric oxides. By forming this non-stoichiometric compound, it is difficult to form high-resistance Al 2 O 3 without strictly controlling the amount of Al, and a low-resistance and high-density sputtering target can be manufactured.
　Ｉｎ２Ｏ３（ＺｎＯ）ｍ（ｍは整数）で表わされるホモロガス構造化合物にＡｌが固溶しているかどうかは、Ｘ線回折パターンから算出される結晶の軸長から確かめることができる。
　Ｘ線回折パターンから算出されたＩｎ２Ｏ３（ＺｎＯ）ｍ（ｍは整数）で表わされるホモロガス構造化合物結晶の結晶軸長（ａ軸、ｂ軸、ｃ軸）が、ＪＣＰＤＳデータベースあるいはＩＣＳＤでＸ線回折パターンと一致する結晶の結晶軸長よりも小さく、かつ、ｍの値が対応する、ＩｎＡｌＯ３（ＺｎＯ）ｍ（ｍは整数）で表わされるホモロガス構造化合物結晶の結晶軸長（ａ軸、ｂ軸、ｃ軸）よりも大きい時、Ｉｎ２Ｏ３（ＺｎＯ）ｍ（ｍは整数）で表わされるホモロガス構造化合物にＡｌが固溶しているといえる。 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 crystal axis length of the homologous structure compound crystal represented by InAlO 3 (ZnO) m (m is an integer), which is smaller than the crystal axis length of the crystal corresponding to the line diffraction pattern and corresponding to the value of m (a axis, When larger than (b-axis, c-axis), it can be said that Al is dissolved in the homologous structure compound represented by In 2 O 3 (ZnO) m (m is an integer).
　例えば、Ｉｎ２Ｚｎ３Ｏ６のホモロガス構造は、Ｘ線回折で、ＩＣＳＤの＃１６２４５０のピークパターンか、あるいは類似の（シフトした）パターンを示すものである。ＩＣＳＤの＃１６２４５０によると、ａ＝３．３５２Å、ｂ＝３．３５２Å、ｃ＝４２．４８８Åである。また、ＩｎＡｌＺｎ３Ｏ６のホモロガス構造は、Ｘ線回折で、ＪＣＰＤＳデータベースのＮｏ．４０－０２６０のピークパターンか、あるいは類似の（シフトした）パターンを示すものである。ＪＣＰＤＳデータベースのＮｏ．４０－０２６０によると、ａ＝３．２８１Å、ｂ＝３．２８１Å、ｃ＝４１．３５Åである。
　Ｘ線回折パターンから算出されたＩｎ２Ｏ３（ＺｎＯ）２で表わされるホモロガス構造化合物結晶の結晶軸長ａ、ｂ、ｃが、３．２８１Å＜ａ＜３．３５２Å、３．２８１Å＜ｂ＜３．３５２Å、４１．３５Å＜ｂ＜４２．４８８Åを満たす時、Ａｌは固溶しているといえる。 For example, 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. According to ICSD # 162450, a = 3.352 mm, b = 3.352 mm, and c = 42.488 mm. In addition, 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. JCPDS database No. According to 40-0260, a = 3.281Å, b = 3.281Å, and c = 41.35Å.
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 が <a <3.352Å, 3.281Å <b <. When 3.352Å, 41.35Å <b <42.488Å is satisfied, it can be said that Al is dissolved.
　本発明のスパッタリングターゲットは、各元素の原子比が下記式（１）～（３）を満たすことが好ましい。
　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）
（式中、Ｉｎ、Ｚｎ及びＡｌは、それぞれ、スパッタリングターゲット中における各元素の原子比を示す。） In the sputtering target of the present invention, 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.)
　上記式（１）において、Ｉｎ元素の量が０．１０以上であると、スパッタリングターゲットを製造する際にバルク抵抗値が下がりやすくなり、密度低下が防ぐことができるため、安定してＤＣスパッタリングを行うことができる。
　一方、Ｉｎ元素の量が０．７０以下であると、そのターゲットを用いて作製した薄膜のキャリア濃度が過剰にならずに、薄膜を半導体として利用することができる。
　以上からＩｎの濃度は、０．１０≦Ｉｎ／（Ｉｎ＋Ｚｎ＋Ａｌ）≦０．７０であることが好ましい。Ｉｎ元素の量［Ｉｎ／（Ｉｎ＋Ｚｎ＋Ａｌ）］は、より好ましくは０．１５～０．７０であり、さらに好ましくは、０．２０～０．６５である。 In the above formula (1), when the amount of In element is 0.10 or more, the bulk resistance value is likely to be lowered when the sputtering target is manufactured, and the density reduction can be prevented. It can be carried out.
On the other hand, when the amount of In element is 0.70 or less, the thin film can be used as a semiconductor without excessive carrier concentration of the thin film manufactured using the target.
From the above, 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.
　上記式（２）において、Ｚｎ元素の量が０．１０以上であると、Ｉｎ２Ｏ３（ＺｎＯ）ｍ（ｍは整数）若しくはＩｎＡｌＯ３（ＺｎＯ）ｍで表わされるホモロガス構造化合物が形成されやすくなることで、高抵抗なＡｌ２Ｏ３が形成されにくくなり、スパッタリングターゲットを低抵抗で高密度にしやすくなる。
　一方、Ｚｎ元素の量が０．９０以下であると、得られる薄膜のウェットエッチャントへの溶解速度が速くなりすぎることを防ぐことができる。
　以上からＺｎの濃度は、０．１０≦Ｚｎ／（Ｉｎ＋Ｚｎ＋Ａｌ）≦０．９０であることが好ましい。
　Ｚｎ元素の量［Ｚｎ／（Ｉｎ＋Ｚｎ＋Ａｌ）］は、より好ましくは０．１５～０．８０であり、さらに好ましくは、０．２０～０．７０である。 In the above formula (2), when the amount of Zn element is 0.10 or more, a homologous structure compound represented by In 2 O 3 (ZnO) m (m is an integer) or InAlO 3 (ZnO) m is easily formed. As a result, it becomes difficult to form high-resistance Al 2 O 3 , and it becomes easy to make the sputtering target high in density with low resistance.
On the other hand, 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.
From the above, 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.
　上記式（３）において、Ａｌ元素の量が０．０１以上であると、作製した薄膜のキャリア濃度が過剰になることを防ぐことができ、半導体として利用することができる。また、チャネル層を成膜し、ＴＦＴに適用した場合に信頼性を向上させることができる。
　一方、Ａｌ元素の量が０．３０以下であると、ターゲット中にＡｌ２Ｏ３が生成されるのを防ぐことができ、ターゲットを低抵抗にすることができる。
　以上からＡｌの濃度は、０．０１≦Ａｌ／（Ｉｎ＋Ｚｎ＋Ａｌ）≦０．３０であることが好ましい。Ａｌ元素の量［Ａｌ／（Ｉｎ＋Ｚｎ＋Ａｌ）］は、より好ましくは０．０２～０．３０であり、さらに好ましくは、０．０２～０．２５である。 In the above formula (3), when the amount of Al element is 0.01 or more, it is possible to prevent the carrier concentration of the manufactured thin film from becoming excessive, and it can be used as a semiconductor. 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, generation of Al 2 O 3 in the target can be prevented, and the resistance of the target can be reduced.
From the above, 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.
　スパッタリングターゲットに含まれる各元素の原子比は、誘導結合プラズマ発光分析装置（ＩＣＰ－ＡＥＳ）により、含有元素を定量分析して求めることができる。
　具体的に、溶液試料をネブライザーで霧状にして、アルゴンプラズマ（約６０００～８０００℃）に導入すると、試料中の元素は熱エネルギーを吸収して励起され、軌道電子が基底状態から高いエネルギー準位の軌道に移る。この軌道電子は１０－７～１０－８秒程度で、より低いエネルギー準位の軌道に移る。この際にエネルギーの差を光として放射し発光する。この光は元素固有の波長（スペクトル線）を示すため、スペクトル線の有無により元素の存在を確認できる（定性分析）。 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).
　また、それぞれのスペクトル線の大きさ（発光強度）は試料中の元素数に比例するため、既知濃度の標準液と比較することで試料濃度を求めることができる（定量分析）。
　定性分析で含有されている元素を特定後、定量分析で含有量を求め、その結果から各元素の原子比を求める。 In addition, since the magnitude (luminescence intensity) of each spectral line is proportional to the number of elements in the sample, 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.
　上記のように、スパッタリングターゲットに含有される金属元素は、実質的にＩｎ、Ｚｎ及びＡｌからなっており、本発明の効果を損なわない範囲で他に不可避不純物を含んでいてもよい。
　本発明において「実質的」とは、スパッタリングターゲットとしての効果が上記Ｉｎ、Ｚｎ及びＡｌに起因すること、又はスパッタリングターゲットの金属元素の９５重量％以上１００重量％以下（好ましくは９８重量％以上１００重量％以下）がＩｎ、Ｚｎ及びＡｌであることを意味する。 As described above, 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.
In the present invention, “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.
　本発明のスパッタリングターゲットは、好ましくは相対密度が９８％以上である。大型基板（１Ｇサイズ以上）にスパッタ出力を上げて酸化物半導体薄膜を成膜する場合は、相対密度が９８％以上であることが好ましい。相対密度とは、加重平均より算出した理論密度に対して相対的に算出した密度である。各原料の密度の加重平均より算出した密度が理論密度であり、これを１００％とする。 The sputtering target of the present invention preferably has a relative density of 98% or more. In the case of forming an oxide semiconductor thin film by increasing the sputtering output on a large substrate (1G size 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%.
　相対密度が９８％以上であれば、安定したスパッタリング状態が保たれる。大型基板でスパッタ出力を上げて成膜する場合は、相対密度が９８％未満ではターゲット表面が黒化したり、異常放電が発生したりする場合がある。相対密度はより好ましくは９８．５％以上、さらにより好ましくは９９％以上である。 If the relative density is 98% or more, a stable sputtering state is maintained. When film formation is performed with a large substrate at an increased sputtering output, 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.
　相対密度はアルキメデス法により測定した実測密度と理論密度とから算出できる。相対密度は、好ましくは１００％以下である。１００％以下であると、金属粒子が焼結体に発生したり、低級酸化物が生成したりすることを防ぐことができ、成膜時の酸素供給量を厳密に調整しなくても済む。
　また、焼結後に、還元性雰囲気下での熱処理操作等の後処理工程等を行って密度を調整することもできる。還元性雰囲気は、アルゴン、窒素、水素等の雰囲気や、それらの混合気体雰囲気が用いられる。 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.
In addition, the density can be adjusted by performing a post-treatment step such as a heat treatment operation under a reducing atmosphere after sintering. As the reducing atmosphere, an atmosphere of argon, nitrogen, hydrogen, or a mixed gas atmosphere thereof is used.
　本発明のスパッタリングターゲットは、相対密度が９８％以上であり、かつバルク比抵抗が１０ｍΩｃｍ以下であることが好ましい。これにより、本発明のスパッタリングターゲットをスパッタリングする際には、異常放電の発生を抑制することができる。本発明のスパッタリングターゲットは、高品質の酸化物半導体薄膜を、効率的に、安価に、かつ省エネルギーで成膜することができる。
　バルク比抵抗は、例えば、実施例に記載の方法により測定することができる。
　バルク比抵抗は、例えば０．０１Ωｃｍ以上である。 The sputtering target of the present invention preferably has a relative density of 98% or more and a bulk specific resistance of 10 mΩcm or less. Thereby, when sputtering the sputtering target of this invention, generation | occurrence | production of abnormal discharge can be suppressed. 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 Ωcm or more.
　本発明のスパッタリングターゲット中の結晶の最大粒径は８μｍ以下であることが望ましい。結晶が粒径８μｍ以下であるとノジュールの発生を防ぐことができる。
　スパッタによってターゲット表面が削られる場合、その削られる速度が結晶面の方向によって異なり、ターゲット表面に凹凸が発生する。この凹凸の大きさはスパッタリングターゲット中に存在する結晶粒径に依存している。結晶粒径が小さいとスパッタリングターゲットの凹凸が小さくなり、ノジュールが発生しにくくなると考えられる。 The maximum grain size of the crystal in the sputtering target of the present invention is desirably 8 μm or less. Generation of nodules can be prevented when the crystal has a particle size of 8 μm or less.
When the target surface is cut by sputtering, 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.
　これらのスパッタリングターゲットの結晶の最大粒径は、スパッタリングターゲットの形状が円形の場合、円の中心点（１箇所）と、その中心点で直交する２本の中心線上の中心点と周縁部との中間点（４箇所）の合計５箇所において、また、スパッタリングターゲットの形状が四角形の場合には、その中心点（１箇所）と、四角形の対角線上の中心点と角部との中間点（４箇所）の合計５箇所において１００μｍ四方の枠内で観察される最大径を有する粒子についてその最大径を測定し、これらの５箇所の枠内のそれぞれに存在する最大粒子の粒径の平均値で表す。粒径は、結晶粒の長径について測定する。結晶粒は走査型電子顕微鏡（ＳＥＭ）により観察することができる。 When the shape of the sputtering target is circular, 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. At a total of five intermediate points (four locations), and when the sputtering target has a quadrangular shape, the central point (one location) and the intermediate point (4) between the central point and the corner on the diagonal of the quadrangle. The maximum diameter of particles having the maximum diameter observed in a 100 μm square frame at a total of five locations 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).
　本発明のスパッタリングターゲットの製造方法は以下の３工程を含む。
　（１）少なくともインジウム元素（Ｉｎ）、亜鉛元素（Ｚｎ）及びアルミニウム元素（Ａｌ）を混合して混合物を得る混合工程
　（２）上記混合物を成形して成形体を得る成形工程
　（３）酸素含有雰囲気で上記成形体を焼結する焼結工程 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
　以下、各工程について説明する。
（１）少なくともインジウム元素（Ｉｎ）、亜鉛元素（Ｚｎ）及びアルミニウム元素（Ａｌ）を混合して混合物を得る混合工程
　原料化合物は特に制限されず、Ｉｎ、Ｚｎ及びＡｌを含む化合物であり、焼結体が以下の原子比を有することができる化合物を用いることが好ましい。
　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）
　（式中、Ｉｎ、Ｚｎ及びＡｌは、それぞれ、スパッタリングターゲットにおける各元素の原子比を示す。） Hereinafter, each step will be described.
(1) Mixing step of obtaining a mixture by mixing at least indium element (In), zinc element (Zn) and aluminum element (Al) 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.)
　例えば、酸化インジウム、酸化亜鉛及びアルミニウム金属の組み合わせや、酸化インジウム、酸化亜鉛及び酸化アルミニウムの組合せ等が挙げられる。尚、原料は粉末であることが好ましい。
　原料は、酸化インジウム、酸化亜鉛及び酸化アルミニウムの混合粉末であることが好ましい。 For example, a combination of indium oxide, zinc oxide and aluminum metal, a combination of indium oxide, zinc oxide and aluminum oxide, or the like can be given. The raw material is preferably a powder.
The raw material is preferably a mixed powder of indium oxide, zinc oxide and aluminum oxide.
　原料に単体金属を用いた場合、例えば、酸化インジウム、酸化亜鉛及びアルミニウム金属の組み合わせを原料粉末として用いた場合、得られる焼結体中にアルミニウムの金属粒が存在し、成膜中にターゲット表面の金属粒が溶融してターゲットから放出されないことがあり、得られる膜の組成と焼結体の組成が大きく異なってしまう場合がある。 When a single metal is used as a raw material, for example, when 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.
　原料粉末の平均粒径は、好ましくは０．１μｍ～１．２μｍであり、より好ましくは０．１μｍ～１．０μｍ以下である。原料粉末の平均粒径はレーザー回折式粒度分布装置等で測定することができる。 The average particle diameter of the raw material powder is preferably 0.1 μm to 1.2 μm, more preferably 0.1 μm to 1.0 μm 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.
　例えば、平均粒径が０．１μｍ～１．２μｍのＩｎ２Ｏ３粉末、平均粒径が０．１μｍ～１．２μｍのＺｎＯ粉末及び平均粒径が０．１μｍ～１．２μｍのＡｌ２Ｏ３粉末を含んだ酸化物を原料粉末とし、これらを、上記式（１）～（３）を満たす割合で調合する。
　混合方法については以下の工程（２）とともに説明する。 For example, In 2 O 3 powder having an average particle size of 0.1 μm to 1.2 μm, ZnO powder having an average particle size of 0.1 μm to 1.2 μm, and Al 2 O having an average particle size of 0.1 μm to 1.2 μm 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).
（２）混合物を成形して成形体を得る成形工程
　工程（１）の混合方法、工程（２）の成形方法は特に限定されず、公知の方法を用いて行うことができる。例えば、酸化インジウム粉、酸化亜鉛及び酸化アルミニウム粉を含んだ酸化物の混合粉を含む原料粉末に、水系溶媒を配合し、得られたスラリーを１２時間以上混合した後、固液分離・乾燥・造粒し、引き続き、この造粒物を型枠に入れて成形する。 (2) Molding step of molding the mixture to obtain a molded body The mixing method in step (1) and the molding method in step (2) are not particularly limited, and can be performed using known methods. For example, 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.
　混合については、湿式又は乾式によるボールミル、振動ミル、ビーズミル等を用いることができる。均一で微細な結晶粒及び空孔を得るには、短時間で凝集体の解砕効率が高く、添加物の分散状態も良好となるビーズミル混合法が最も好ましい。
　ボールミルによる混合時間は、好ましくは１５時間以上、より好ましくは１９時間以上とする。混合時間が不足すると最終的に得られる焼結体中にＡｌ２Ｏ３等の高抵抗の化合物が生成するおそれがあるからである。 For mixing, a wet or dry ball mill, vibration mill, bead mill, or the like can be used. In order to obtain uniform and fine crystal grains and vacancies, 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.
　ビーズミルによる粉砕、混合時間は、装置の大きさ、処理するスラリー量によって異なるが、スラリー中の粒度分布がすべて１μｍ以下と均一になるように適宜調整する。
　また、混合する際にはバインダーを任意量だけ添加し、同時に混合を行うと好ましい。バインダーには、ポリビニルアルコール、酢酸ビニル等を用いることができる。 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 μm or less.
Further, when mixing, it is preferable to add an arbitrary amount of a binder and mix them at the same time. As the binder, polyvinyl alcohol, vinyl acetate, or the like can be used.
　次に、原料粉末スラリーから造粒粉を得る。造粒に際しては、急速乾燥造粒を行うことが好ましい。急速乾燥造粒するための装置としては、スプレードライヤが広く用いられている。具体的な乾燥条件は、乾燥するスラリーのスラリー濃度、乾燥に用いる熱風温度、風量等の諸条件により決定されるため、実施に際しては、予め最適条件を求めておくことが必要となる。 Next, granulated powder is obtained from the raw material powder slurry. In granulation, it is preferable to perform rapid drying granulation. As an apparatus for rapid drying granulation, a spray dryer is widely used. 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.
　自然乾燥を行うと、原料粉末の比重差によって沈降速度が異なるため、Ｉｎ２Ｏ３粉末、ＺｎＯ粉末及びＡｌ２Ｏ３粉末の分離が起こり、均一な造粒粉が得られなくなるおそれがある。この不均一な造粒粉を用いて焼結体を作製すると、焼結体内部にＡｌ２Ｏ３等が存在して、スパッタリングにおける異常放電の原因となる場合がある。
　造粒粉に対して、通常、金型プレス又は冷間静水圧プレス（ＣＩＰ）により、例えば１．２ｔｏｎ／ｃｍ２以上の圧力で成形を施して成形体を得る。 When natural drying is performed, 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. When 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.
（３）酸素含有雰囲気で成形体を焼結する焼結工程
　焼結工程は、昇温工程、仮焼き工程、保持工程を含む。また、昇温工程の途中には、１～５時間、７００～９００℃の範囲内において温度を保持する仮焼き工程を含む。これにより、ターゲットの密度が上昇しやすくなり、スパッタ時のノジュールの発生をより抑制できるため好ましい。また、ターゲットが所望の組成からずれてしまうことを防ぐことができる。 (3) 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 | deviates from a desired composition.
　焼結時の昇温速度は、通常８℃／分以下であり、好ましくは４℃／分以下であり、より好ましくは３℃／分以下であり、さらに好ましくは２℃／分以下である。昇温速度が８℃／分以下であるとクラックが発生しにくい。 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. When the temperature rising rate is 8 ° C./min or less, cracks are hardly generated.
　昇温が完了した後、１２００～１６５０℃の焼結温度で５～５０時間保持して焼結を行う（保持工程）。焼結温度は好ましくは１３００～１６００℃である。焼結時間は好ましくは１０～２０時間である。
　焼結温度が１２００℃以上かつ焼結時間が５時間以上であると、Ａｌ２Ｏ３等がターゲット内部に形成されるのを防ぐことができる。一方、焼成温度が１６５０℃以下で焼成時間が５０時間以下であると、著しい結晶粒成長により平均結晶粒径の増大を防ぐことができ、製造の効率も下がらない。 After the temperature rise is completed, 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.
When 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. On the other hand, when 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.
　本発明で用いる焼結方法としては、常圧焼結法の他、ホットプレス、酸素加圧、熱間等方圧加圧等の加圧焼結法も採用することができる。ただし、製造コストの低減、大量生産の可能性、容易に大型の焼結体を製造できるといった観点から、常圧焼結法を採用することが好ましい。 As a sintering method used in the present invention, 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. However, it is preferable to employ a normal pressure sintering method from the viewpoints of reducing manufacturing costs, possibility of mass production, and easy production of large sintered bodies.
　常圧焼結法では、成形体を大気雰囲気、又は酸化性ガス雰囲気、好ましくは酸化性ガス雰囲気にて焼結する。酸化性ガス雰囲気とは、好ましくは酸素ガス雰囲気である。酸素ガス雰囲気は、酸素濃度が、例えば１０～１００体積％の雰囲気であることが好ましい。本発明のスパッタリングターゲットの製造方法においては、昇温過程にて酸素ガス雰囲気を導入することで、焼結体密度をより高くすることができる。 In the normal pressure sintering method, 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. In the manufacturing method of the sputtering target of this invention, a sintered compact density can be made higher by introduce | transducing oxygen gas atmosphere in a temperature rising process.
　上記焼結工程で得られた焼結体のバルク抵抗をターゲット全体で均一化するために、必要に応じて還元工程を設けてもよい。
　還元方法としては、例えば、還元性ガスによる方法や真空焼成又は不活性ガスによる還元等が挙げられる。
　還元性ガスによる還元処理の場合、水素、メタン、一酸化炭素、又はこれらのガスと酸素との混合ガス等を用いることができる。
　不活性ガス中での焼成による還元処理の場合、窒素、アルゴン、又はこれらのガスと酸素との混合ガス等を用いることができる。 In order to make the bulk resistance of the sintered body obtained in the sintering process uniform over the entire target, a reduction process may be provided as necessary.
Examples of the reduction method include a method using a reducing gas, vacuum firing, or reduction using an inert gas.
In the case of reduction treatment with a reducing gas, hydrogen, methane, carbon monoxide, a mixed gas of these gases and oxygen, or the like can be used.
In the case of reduction treatment by firing in an inert gas, nitrogen, argon, a mixed gas of these gases and oxygen, or the like can be used.
　還元処理時の温度は、通常１００～８００℃、好ましくは２００～８００℃である。また、還元処理の時間は、通常０．０１～１０時間、好ましくは０．０５～５時間である。 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.
　以上をまとめると、例えば、酸化インジウム粉と酸化亜鉛粉及び酸化アルミニウム粉との混合粉を含む原料粉末に、水系溶媒を配合し、得られたスラリーを１２時間以上混合した後、固液分離・乾燥・造粒し、引き続き、この造粒物を型枠に入れて成形し、その後、得られた成形物を酸素含有雰囲気で、平均昇温速度を８℃／分以下とし、１～５時間、７００～９００℃の範囲内において温度を保持して仮焼し、１２００～１６５０℃で５～５０時間焼成することで焼結体を得ることができる。 To summarize the above, for example, 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.
　上記で得られた焼結体を加工することにより本発明のスパッタリングターゲットとすることができる。具体的には、焼結体をスパッタリング装置への装着に適した形状に切削加工することでスパッタリングターゲット素材とし、該ターゲット素材をバッキングプレートに接着することでスパッタリングターゲットとすることができる。 The sputtering target of the present invention can be obtained by processing the sintered body obtained above. Specifically, 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.
　焼結体をターゲット素材とするには、焼結体を、例えば平面研削盤で研削して表面粗さＲａが０．５μｍ以下の素材とする。ここで、さらにターゲット素材のスパッタ面に鏡面加工を施して、平均表面粗さＲａが１０００オングストローム以下としてもよい。 In order to use the sintered body as a target material, the sintered body is ground with, for example, a surface grinder to obtain a material having a surface roughness Ra of 0.5 μm or less. Here, 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.
　鏡面加工（研磨）は、機械的な研磨、化学研磨、メカノケミカル研磨（機械的な研磨と化学研磨の併用）等の、公知の研磨技術を用いることができる。例えば、固定砥粒ポリッシャー（ポリッシュ液：水）で＃２０００以上にポリッシングしたり、又は遊離砥粒ラップ（研磨材：ＳｉＣペースト等）にてラッピング後、研磨材をダイヤモンドペーストに換えてラッピングしたりすることによって得ることができる。このような研磨方法には特に制限はない。 Mirror surface processing (polishing) 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. Such a polishing method is not particularly limited.
　ターゲット素材の表面は２００～１０，０００番のダイヤモンド砥石により仕上げを行うことが好ましく、４００～５，０００番のダイヤモンド砥石により仕上げを行うことが特に好ましい。２００番より大きく、１０，０００番より小さいダイヤモンド砥石を使用するとターゲット素材が割れにくくなる。
　ターゲット素材の表面粗さＲａが０．５μｍ以下であり、方向性のない研削面を備えていることが好ましい。Ｒａが０．５μｍ以下であり、研磨面の方向性をなくすと、異常放電が起きたり、パーティクルが発生したりすることを防ぐことができる。 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. When a diamond grindstone larger than No. 200 and smaller than No. 10,000 is used, the target material becomes difficult to break.
It is preferable that the target material has a surface roughness Ra of 0.5 μm or less and has a non-directional ground surface. If Ra is 0.5 μm or less and the directionality of the polished surface is lost, abnormal discharge or particles can be prevented from occurring.
　次に、得られたターゲット素材を清浄処理する。清浄処理にはエアーブロー又は流水洗浄等を使用できる。エアーブローで異物を除去する際には、ノズルの向い側から集塵機で吸気を行なうとより有効に除去できる。
　尚、以上のエアーブローや流水洗浄では限界があるので、さらに超音波洗浄等を行なうこともできる。この超音波洗浄は周波数２５～３００ｋＨｚの間で多重発振させて行なう方法が有効である。例えば周波数２５～３００ｋＨｚの間で、２５ｋＨｚ刻みに１２種類の周波数を多重発振させて超音波洗浄を行なうのが好ましい。 Next, the obtained target material is cleaned. Air blow or running water washing can be used for the cleaning treatment. When removing foreign matter by air blow, it is possible to remove the foreign matter more effectively by suctioning with a dust collector from the opposite side of the nozzle.
In addition, since the above air blow and running water cleaning have a limit, ultrasonic cleaning etc. can also be performed. This ultrasonic cleaning is effective by performing multiple oscillations at a frequency of 25 to 300 kHz. For example, it is preferable to perform ultrasonic cleaning by multiplying twelve frequencies in 25 kHz increments between frequencies of 25 to 300 kHz.
　ターゲット素材の厚みは通常２～２０ｍｍ、好ましくは３～１２ｍｍ、特に好ましくは４～６ｍｍである。
　上記のようにして得られたターゲット素材をバッキングプレートへボンディングすることによって、スパッタリングターゲットを得ることができる。また、複数のターゲット素材を１つのバッキングプレートに取り付け、実質１つのターゲットとしてもよい。 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.
　本発明の酸化物半導体薄膜は、上記説明した本発明のスパッタリングターゲットを用いて、スパッタリング法により成膜することにより得られる。
　本発明の酸化物半導体薄膜は、インジウム、亜鉛、アルミニウム、酸素からなり、通常、原子比は（１）～（３）のとおりである
　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）
（式中、Ｉｎ、Ｚｎ及びＡｌは、それぞれ、酸化物半導体薄膜における各元素の原子比を示す。） 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.)
　上記式（１）において、Ｉｎ元素の量が０．１０以上であると、薄膜のキャリア濃度が大幅に低下することなく、薄膜を半導体として利用することができる。
　一方、Ｉｎ元素の量が０．７０以下であると、得られた薄膜のキャリア濃度が高くなりすぎるのを防ぐことができ、薄膜を半導体として利用することができる。 In the above formula (1), 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.
On the other hand, 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.
　上記式（２）において、Ｚｎ元素の量が０．１０以上であると、得られる膜を非晶質膜として安定させることができる。
　一方、Ｚｎ元素の量が０．９０以下であると、得られる薄膜のウェットエッチャントへの溶解速度が速くなりすぎることが防ぐことができ、ウェットエッチングが容易になる。
　Ｚｎ元素の量［Ｚｎ／（Ｉｎ＋Ｚｎ＋Ａｌ）］は、より好ましくは０．１５～０．８０であり、さらに好ましくは、０．２０～０．７０である。 In the above formula (2), when the amount of Zn element is 0.10 or more, the obtained film can be stabilized as an amorphous film.
On the other hand, 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.
　上記式（３）において、Ａｌ元素の量が０．０１以上であると、成膜時の酸素分圧を低く抑えることができる。Ａｌ元素は酸素との結合が強いため、成膜時の酸素分圧を下げることが出来る。また、チャネル層を成膜し、ＴＦＴに適用した場合に信頼性を向上させることができる。
　一方、Ａｌ元素の量が０．３０以下であると、チャネル層を成膜し、ＴＦＴに適用した場合に移動度が低くなることを防ぐことができる。 In the above formula (3), when the amount of Al element is 0.01 or more, 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.
　本発明のスパッタリングターゲットは、高い導電性を有することから成膜速度の速いＤＣスパッタリング法を適用することができる。
　本発明のスパッタリングターゲットは、上記ＤＣスパッタリング法に加えて、ＲＦスパッタリング法、ＡＣスパッタリング法、パルスＤＣスパッタリング法にも適用することができ、異常放電のないスパッタリングが可能である。 Since the sputtering target of the present invention has high conductivity, 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.
　酸化物半導体薄膜は、上記スパッタリングターゲットを用いて、蒸着法、イオンプレーティング法、パルスレーザー蒸着法等により作製することもできる。 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.
　スパッタリングガス（雰囲気）としては、アルゴン等の希ガスと酸化性ガスとの混合ガスを用いることができる。酸化性ガスとはＯ２、ＣＯ２、Ｏ３、水蒸気（Ｈ２Ｏ）、Ｎ２Ｏ等が挙げられる。スパッタリングガスは、希ガスと、水蒸気、酸素ガス及び亜酸化窒素ガスから選ばれる一種以上を含有する混合気体が好ましく、少なくとも希ガスと水蒸気を含有する混合気体であることがより好ましい。 As the sputtering gas (atmosphere), a mixed gas of a rare gas such as argon and an oxidizing gas can be used. Examples of 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.
　酸化物半導体薄膜のキャリア濃度は、通常１０１９ｃｍ－３以下であり、好ましくは１０１３～１０１８ｃｍ－３であり、さらに好ましくは１０１４～１０１８ｃｍ－３であり、特に好ましくは１０１５～１０１８／ｃｍ－３である。
　酸化物層のキャリア濃度が１０１９ｃｍ－３以下であると、薄膜トランジスタ等の素子を構成した際に、漏れ電流の発生を防ぐことができる。また、ノーマリーオンになってしまったり、ｏｎ－ｏｆｆ比が小さくなってしまったりすることを防ぐことができ、トランジスタ性能が発揮することができる。
　酸化物半導体薄膜のキャリア濃度は、ホール効果測定方法により測定することができる。 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 .
When the carrier concentration of the oxide layer is 10 19 cm −3 or less, generation of leakage current can be prevented when an element such as a thin film transistor is formed. In addition, it is possible to prevent the transistor from being normally on or the on-off ratio from being decreased, and the transistor performance can be exhibited.
The carrier concentration of the oxide semiconductor thin film can be measured by a Hall effect measurement method.
　スパッタリング成膜時の酸素分圧比は０.１％以上５０％以下とすることが好ましい。酸素分圧比が５０％以下の条件で作製した薄膜は、キャリア濃度が低下しすぎることを防ぐことができる。
　より好ましくは、酸素分圧比は０.１％～３０％である。 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%.
　本発明における酸化物薄膜堆積時のスパッタガス（雰囲気）に含まれる水蒸気（水分子）の分圧比、即ち、［水蒸気（Ｈ２Ｏ）］／（［水蒸気（Ｈ２Ｏ）］＋［希ガス］＋［その他のガス分子］）は、０．１～２５％であることが好ましい。
　また、水の分圧比が２５％以下であると、膜密度の低下を抑えることができ、Ｉｎの５ｓ軌道の重なりが小さくなることを防ぐことができるので、移動度が低下しにくくなる。スパッタリング時の雰囲気中の水の分圧比は０．７～１３％がより好ましく、１～６％が特に好ましい。 The partial pressure ratio of water vapor (water molecules) contained in the sputtering gas (atmosphere) during oxide thin film deposition in the present invention, that is, [water vapor (H 2 O)] / ([water vapor (H 2 O)] + [rare gas] ] + [Other gas molecules]) 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%.
　スパッタリングにより成膜する際の基板温度は、２５～１２０℃であることが好ましく、さらに好ましくは２５～１００℃、特に好ましくは２５～９０℃である。成膜時の基板温度が１２０℃以下であると、成膜時に導入する酸素等の取り込みが減少することがなくなり、加熱後の薄膜のキャリア濃度が１０１９／ｃｍ－３以下にすることができる。また、成膜時の基板温度が２５℃よりも高いと薄膜の膜密度が向上しやすく、ＴＦＴの移動度が向上しやすくなる。 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. When 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. . Further, when 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.
　スパッタリングによって得られた酸化物薄膜を、さらに１５０～５００℃に１５分～５時間保持してアニール処理を施すことが好ましい。成膜後のアニール処理温度は２００℃以上４５０℃以下であることがより好ましく、２５０℃以上３５０℃以下であることがさらに好ましい。上記アニールを施すことにより、半導体特性が得られる。 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. By performing the annealing, semiconductor characteristics can be obtained.
　また、加熱時の雰囲気は、特に限定されるわけではないが、キャリア制御性の観点から、大気雰囲気、酸素流通雰囲気が好ましい。
　酸化物薄膜の後処理アニール工程においては、酸素の存在下又は不存在下でランプアニール装置、レーザーアニール装置、熱プラズマ装置、熱風加熱装置、接触加熱装置等を用いることができる。 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.
In the post-treatment annealing step of the oxide thin film, 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.
　スパッタリング時におけるターゲットと基板との間の距離は、基板の成膜面に対して垂直方向に好ましくは１～１５ｃｍであり、さらに好ましくは２～８ｃｍである。この距離が１ｃｍ以上の場合、基板に到達するターゲット構成元素の粒子の運動エネルギーが大きくなりすぎることを防ぐことができ、良好な膜特性を得ることができる。また、膜厚及び電気特性の面内分布が生じにくくなる。一方、ターゲットと基板との間隔が１５ｃｍ以下の場合、基板に到達するターゲット構成元素の粒子の運動エネルギーが小さくなりすぎずに、緻密な膜を得ることができ、良好な半導体特性を得ることができる。 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. When 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. On the other hand, when 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.
　酸化物薄膜の成膜は、磁場強度が３００～１５００ガウスの雰囲気下でスパッタリングすることが望ましい。磁場強度が３００ガウス以上の場合、プラズマ密度を高くすることができ、高抵抗のスパッタリングターゲットでも、スパッタリングすることができる。一方、１５００ガウス以下であると、膜厚及び膜中の電気特性の制御性が向上する。 The oxide thin film is preferably formed by sputtering in an atmosphere having a magnetic field strength of 300 to 1500 gauss. When 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. On the other hand, when it is 1500 gauss or less, the controllability of the film thickness and the electrical characteristics in the film is improved.
　気体雰囲気の圧力（スパッタ圧力）は、プラズマが安定して放電できる範囲であれば特に限定されないが、好ましくは０．１～３．０Ｐａであり、さらに好ましくは０．１～１．５Ｐａであり、特に好ましくは０．１～１．０Ｐａである。スパッタ圧力が３．０Ｐａ以下の場合、スパッタ粒子の平均自由工程が短くなって、薄膜の密度が低下することを防ぐことができる。また、スパッタ圧力が０．１Ｐａ以上である場合、成膜時に膜中に微結晶が生成することを防ぎやすくなる。尚、スパッタ圧力とは、アルゴン等の希ガス、水蒸気、酸素ガス等を導入した後のスパッタ開始時の系内の全圧をいう。 The pressure in the gas atmosphere (sputtering pressure) 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. When 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.
　また、酸化物半導体薄膜の成膜を、次のような交流スパッタリングで行ってもよい。
　真空チャンバー内に所定の間隔を置いて並設された３枚以上のターゲットに対向する位置に、基板を順次搬送し、各ターゲットに対して交流電源から負電位及び正電位を交互に印加して、ターゲット上にプラズマを発生させて基板表面上に成膜する。 Alternatively, 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.
　このとき、交流電源からの出力の少なくとも１つを、分岐して接続された２枚以上のターゲットの間で、電位を印加するターゲットの切替を行いながら行う。即ち、上記交流電源からの出力の少なくとも１つを分岐して２枚以上のターゲットに接続し、隣り合うターゲットに異なる電位を印加しながら成膜を行う。 At this time, at least one of the outputs from the AC power supply is performed while switching the target to which the potential is applied between two or more targets that are branched and connected. That is, at least one of the outputs from the AC power supply is branched and connected to two or more targets, and film formation is performed while applying different potentials to adjacent targets.
　尚、交流スパッタリングによって酸化物半導体薄膜を成膜する場合も、例えば、希ガスと、水蒸気、酸素ガス及び亜酸化窒素ガスから選ばれる一以上とを含有する混合気体の雰囲気下においてスパッタリングを行うことが好ましく、少なくとも希ガスと水蒸気を含有する混合気体の雰囲気下においてスパッタリングを行うことが特に好ましい。 Note that when an oxide semiconductor thin film is formed by AC sputtering, for example, 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.
　ＡＣスパッタリングで成膜した場合、工業的に大面積均一性に優れた酸化物層が得られると共に、ターゲットの利用効率の向上が期待出来る。
　また、１辺が１ｍを超える大面積基板にスパッタ成膜する場合には、たとえば特開２００５－２９０５５０号公報記載のような大面積生産用のＡＣスパッタ装置を使用することが好ましい。 When 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.
　特開２００５－２９０５５０号公報記載のＡＣスパッタ装置は、具体的には、真空槽と、真空槽内部に配置された基板ホルダと、この基板ホルダと対向する位置に配置されたスパッタ源とを有する。図５にＡＣスパッタ装置のスパッタ源の要部を示す。スパッタ源は、複数のスパッタ部を有し、板状のターゲット３１ａ～３１ｆをそれぞれ有し、各ターゲット３１ａ～３１ｆのスパッタされる面をスパッタ面とすると、各スパッタ部はスパッタ面が同じ平面上に位置するように配置される。各ターゲット３１ａ～３１ｆは長手方向を有する細長に形成され、各ターゲットは同一形状であり、スパッタ面の長手方向の縁部分（側面）が互いに所定間隔を空けて平行に配置される。従って、隣接するターゲット３１ａ～３１ｆの側面は平行になる。 Specifically, 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 | positions so that it may be located in. 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.
　真空槽の外部には、交流電源１７ａ～１７ｃが配置されており、各交流電源１７ａ～１７ｃの二つの端子のうち、一方の端子は隣接する二つの電極のうちの一方の電極に接続され、他方の端子は他方の電極に接続されている。各交流電源１７ａ～１７ｃの２つの端子は正負の異なる極性の電圧を出力するようになっており、ターゲット３１ａ～３１ｆは電極に密着して取り付けられているので、隣接する２つのターゲット３１ａ～３１ｆには互いに異なる極性の交流電圧が交流電源１７ａ～１７ｃから印加される。従って、互いに隣接するターゲット３１ａ～３１ｆのうち、一方が正電位に置かれる時には他方が負電位に置かれた状態になる。 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.
　電極のターゲット３１ａ～３１ｆとは反対側の面には磁界形成手段４０ａ～４０ｆが配置されている。各磁界形成手段４０ａ～４０ｆは、外周がターゲット３１ａ～３１ｆの外周と略等しい大きさの細長のリング状磁石と、リング状磁石の長さよりも短い棒状磁石とをそれぞれ有している。 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.
　各リング状磁石は、対応する１個のターゲット３１ａ～３１ｆの真裏位置で、ターゲット３１ａ～３１ｆの長手方向に対して平行に配置されている。上述したように、ターゲット３１ａ～３１ｆは所定間隔を空けて平行配置されているので、リング状磁石もターゲット３１ａ～３１ｆと同じ間隔を空けて配置されている。 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.
　ＡＣスパッタで、酸化物ターゲットを用いる場合の交流パワー密度は、３Ｗ／ｃｍ２以上、２０Ｗ／ｃｍ２以下が好ましい。パワー密度が３Ｗ／ｃｍ２以上の場合、成膜速度が速くなり、経済的に生産が可能となる。２０Ｗ／ｃｍ２以下であると、ターゲットが破損を防止することができる。より好ましいパワー密度は３Ｗ／ｃｍ２～１５Ｗ／ｃｍ２である。 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. When 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 | damage as it is 20 W / cm < 2 > or less. A more preferable power density is 3 W / cm 2 to 15 W / cm 2 .
　ＡＣスパッタの周波数は１０ｋＨｚ～１ＭＨｚの範囲が好ましい。１０ｋＨｚ以上であると、騒音の問題が発生しにくくなる。１ＭＨｚ以下であるとプラズマが広がりすぎず、所望のターゲット位置以外でスパッタが行われ、均一性が損なわれることを防ぐことができる。より好ましいＡＣスパッタの周波数は２０ｋＨｚ～５００ｋＨｚである。
　上記以外のスパッタリング時の条件等は、上述したものから適宜選択すればよい。 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.
　本発明の酸化物半導体薄膜は、薄膜トランジスタに使用でき、特にチャネル層として好適に使用できる。
　本発明の薄膜トランジスタは、上記説明した本発明の酸化半導体薄膜をチャネル層として有していれば、その素子構成は特に限定されず、公知の各種の素子構成を採用することができる。 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.
As long as 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.
　本発明の薄膜トランジスタにおけるチャネル層の膜厚は、通常１０～３００ｎｍ、好ましくは２０～２５０ｎｍ、より好ましくは３０～２００ｎｍ、さらに好ましくは３５～１２０ｎｍ、特に好ましくは４０～８０ｎｍである。チャネル層の膜厚が１０ｎｍ以上の場合、大面積に成膜した際の膜厚を均一性にしやすくなり、作製したＴＦＴの特性が面内で不均一になりにくくなる。一方、膜厚が３００ｎｍ以下の場合、成膜時間が長くなりすぎない。 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. When 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. On the other hand, when the film thickness is 300 nm or less, the film formation time does not become too long.
　本発明の薄膜トランジスタにおけるチャネル層は、通常、Ｎ型領域で用いられるが、Ｐ型Ｓｉ系半導体、Ｐ型酸化物半導体、Ｐ型有機半導体等の種々のＰ型半導体と組合せてＰＮ接合型トランジスタ等の各種の半導体デバイスに利用することができる。
　本発明の薄膜トランジスタは、上記チャネル層上に保護膜を備えることが好ましい。本発明の薄膜トランジスタにおける保護膜は、少なくともＳｉＮｘを含有することが好ましい。ＳｉＮｘはＳｉＯ２と比較して緻密な膜を形成できるため、ＴＦＴの劣化抑制効果が高いという利点を有する。
　尚、ｘは任意の数であり、ＳｉＮｘは化学量論比が一定でなくともよい。 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.
　保護膜は、ＳｉＮｘの他に例えばＳｉＯ２、Ａｌ２Ｏ３、Ｔａ２Ｏ５、ＴｉＯ２、ＭｇＯ、ＺｒＯ２、ＣｅＯ２、Ｋ２Ｏ、Ｌｉ２Ｏ、Ｎａ２Ｏ、Ｒｂ２Ｏ、Ｓｃ２Ｏ３、Ｙ２Ｏ３、ＨｆＯ２、ＣａＨｆＯ３、ＰｂＴｉＯ３、ＢａＴａ２Ｏ６、Ｓｍ２Ｏ３、ＳｒＴｉＯ３又はＡｌＮ等の酸化物等を含むことができる。 In addition to SiN x , 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.
　本発明の薄膜トランジスタの電界効果移動度は、好ましくは５ｃｍ２／Ｖｓ以上であり、より好ましくは１０ｃｍ２／Ｖｓ以上である。電界効果移動度は、例えば１００ｃｍ２／Ｖｓ以下である。
　本発明のインジウム元素（Ｉｎ）、亜鉛元素（Ｚｎ）及びアルミニウム元素（Ａｌ）を含有する酸化物半導体薄膜は、Ａｌを含有しているためＣＶＤプロセスによる耐還元性が向上し、保護膜を作製するプロセスによりバックチャネル側が還元されにくく、保護膜としてＳｉＮｘを用いることができる。 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.
　保護膜を形成する前に、チャネル層に対し、オゾン処理、酸素プラズマ処理、二酸化窒素プラズマ処理もしくは亜酸化窒素プラズマ処理を施すことが好ましい。このような処理は、チャネル層を形成した後、保護膜を形成する前であれば、どのタイミングで行ってもよいが、保護膜を形成する直前に行うことが望ましい。このような前処理を行うことによって、チャネル層における酸素欠陥の発生を抑制することができる。 Before forming the protective film, the channel layer is preferably subjected to 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.
　また、ＴＦＴ駆動中に酸化物半導体膜中の水素が拡散すると、閾値電圧のシフトが起こりＴＦＴの信頼性が低下するおそれがある。チャネル層に対し、オゾン処理、酸素プラズマ処理もしくは亜酸化窒素プラズマ処理を施すことにより、薄膜構造中においてＩｎ－ＯＨの結合が安定化され酸化物半導体膜中の水素の拡散を抑制することができる。 In addition, if hydrogen in the oxide semiconductor film diffuses during driving of the TFT, the threshold voltage may shift and the reliability of the TFT may be reduced. By performing ozone treatment, oxygen plasma treatment or nitrous oxide plasma treatment on the channel layer, the In—OH bond is stabilized in the thin film structure, and diffusion of hydrogen in the oxide semiconductor film can be suppressed. .
　薄膜トランジスタは、通常、基板、ゲート電極、ゲート絶縁層、有機半導体層（チャネル層）、ソース電極及びドレイン電極を備える。チャネル層については上述した通りであり、基板については公知の材料を用いることができる。 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.
　本発明の薄膜トランジスタにおけるゲート絶縁膜を形成する材料にも特に制限はなく、一般に用いられている材料を任意に選択できる。具体的には、例えば、ＳｉＯ２、ＳｉＮｘ、Ａｌ２Ｏ３、Ｔａ２Ｏ５、ＴｉＯ２、ＭｇＯ、ＺｒＯ２、ＣｅＯ２、Ｋ２Ｏ、Ｌｉ２Ｏ、Ｎａ２Ｏ、Ｒｂ２Ｏ、Ｓｃ２Ｏ３、Ｙ２Ｏ３、ＨｆＯ２、ＣａＨｆＯ３、ＰｂＴｉＯ３、ＢａＴａ２Ｏ６、ＳｒＴｉＯ３、Ｓｍ２Ｏ３、ＡｌＮ等の化合物を用いることができる。これらのなかでも、好ましくはＳｉＯ２、ＳｉＮｘ、Ａｌ２Ｏ３、Ｙ２Ｏ３、ＨｆＯ２、ＣａＨｆＯ３であり、より好ましくはＳｉＯ２、ＳｉＮｘ、ＨｆＯ２、Ａｌ２Ｏ３である。 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. Among these, 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.
　ゲート絶縁膜は、例えばプラズマＣＶＤ（Ｃｈｅｍｉｃａｌ　Ｖａｐｏｒ　Ｄｅｐｏｓｉｔｉｏｎ；化学気相成長）法により形成することができる。
　プラズマＣＶＤ法によりゲート絶縁膜を形成し、その上にチャネル層を成膜した場合、ゲート絶縁膜中の水素がチャネル層に拡散し、チャネル層の膜質低下やＴＦＴの信頼性低下を招くおそれがある。チャネル層の膜質低下やＴＦＴの信頼性低下を防ぐために、チャネル層を成膜する前にゲート絶縁膜に対してオゾン処理、酸素プラズマ処理、二酸化窒素プラズマ処理もしくは亜酸化窒素プラズマ処理を施すことが好ましい。このような前処理を行うことによって、チャネル層の膜質の低下やＴＦＴの信頼性低下を防ぐことができる。 The gate insulating film can be formed by, for example, a plasma CVD (Chemical Vapor Deposition) method.
When 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. In order to prevent deterioration in channel layer quality and TFT reliability, 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.
　尚、上記の酸化物の酸素数は、必ずしも化学量論比と一致していなくともよく、例えば、ＳｉＯ２でもＳｉＯｘでもよい。
　ゲート絶縁膜は、異なる材料からなる２層以上の絶縁膜を積層した構造でもよい。また、ゲート絶縁膜は、結晶質、多結晶質、非晶質のいずれであってもよいが、工業的に製造しやすい多結晶質又は非晶質であることが好ましい。 Note that the number of oxygen in the oxide does not necessarily match the stoichiometric ratio, and may be, for example, SiO 2 or SiO x .
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.
　本発明の薄膜トランジスタにおけるドレイン電極、ソース電極及びゲート電極の各電極を形成する材料に特に制限はなく、一般に用いられている材料を任意に選択することができる。例えば、インジウム錫酸化物（ＩＴＯ）、インジウム亜鉛酸化物、ＺｎＯ、ＳｎＯ２等の透明電極や、Ａｌ、Ａｇ、Ｃｕ、Ｃｒ、Ｎｉ、Ｍｏ、Ａｕ、Ｔｉ、Ｔａ等の金属電極、又はこれらを含む合金の金属電極を用いることができる。 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. For example, 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.
　ドレイン電極、ソース電極及びゲート電極の各電極は、異なる２層以上の導電層を積層した多層構造とすることもできる。特にソース・ドレイン電極は低抵抗配線への要求が強いため、ＡｌやＣｕ等の良導体をＴｉやＭｏ等の密着性に優れた金属でサンドイッチして使用してもよい。 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. In particular, since the source / drain electrodes have a strong demand for low-resistance wiring, a good conductor such as Al or Cu may be sandwiched with a metal having excellent adhesion such as Ti or Mo.
　本発明の薄膜トランジスタは、電界効果型トランジスタ、論理回路、メモリ回路、差動増幅回路等各種の集積回路にも適用できる。さらに、電界効果型トランジスタ以外にも静電誘起型トランジスタ、ショットキー障壁型トランジスタ、ショットキーダイオード、抵抗素子にも適応できる。
　本発明の薄膜トランジスタの構成は、ボトムゲート、ボトムコンタクト、トップコンタクト等公知の構成を制限なく採用することができる。 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.
As the structure of the thin film transistor of the present invention, known structures such as a bottom gate, a bottom contact, and a top contact can be adopted without limitation.
　特にボトムゲート構成が、アモルファスシリコンやＺｎＯの薄膜トランジスタに比べ高い性能が得られるので有利である。ボトムゲート構成は、製造時のマスク枚数を削減しやすく、大型ディスプレイ等の用途の製造コストを低減しやすいため好ましい。
　本発明の薄膜トランジスタは、表示装置に好適に用いることができる。 In particular, 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.
　大面積のディスプレイ用としては、チャンネルエッチ型のボトムゲート構成の薄膜トランジスタが特に好ましい。チャンネルエッチ型のボトムゲート構成の薄膜トランジスタは、フォトリソ工程時のフォトマスクの数が少なく低コストでディスプレイ用パネルを製造できる。中でも、チャンネルエッチ型のボトムゲート構成及びトップコンタクト構成の薄膜トランジスタが移動度等の特性が良好で工業化しやすいため特に好ましい。 For a large area display, 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. Among them, 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.
実施例１～４
［焼結体の製造］
　原料粉体として下記の酸化物粉末を使用した。尚、酸化物粉末の平均粒径はレーザー回折式粒度分布測定装置ＳＡＬＤ－３００Ｖ（島津製作所製）で測定し、平均粒径はメジアン径Ｄ５０を採用した。
　酸化インジウム粉：平均粒径０．９８μｍ
　酸化亜鉛粉：平均粒径０．９６μｍ
　酸化アルミニウム粉：平均粒径０．９８μｍ 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 μm
Zinc oxide powder: Average particle size 0.96 μm
Aluminum oxide powder: Average particle size 0.98 μm
　上記の粉体を、表１に示す原子比（百分率）になるように秤量し、均一に微粉砕混合後、成形用バインダーを加えて造粒した。次に、この原料粒を金型へ均一に充填し、コールドプレス機にてプレス圧１４０ＭＰａで加圧成形した。
　得られた成形体を、表１に示す焼結温度及び焼結時間で、焼結炉で焼結して焼結体を得た。昇温中（仮焼き工程を含む）は酸素雰囲気とし、その他は大気中（雰囲気）とした。３００℃から８００℃まで１℃／分で昇温し、８００℃から焼結温度までは１℃／分で昇温した。仮焼き工程として、８００℃で３時間保持する工程を含めた。焼結時間経過後の降温速度は１５℃／分とした。 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. Next, 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. During the temperature increase (including the calcining step), 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.
　得られた焼結体の相対密度をアルキメデス法により測定した実測密度と理論密度とから算出した。結果を表１に示す。実施例１～４の焼結体は相対密度９８％以上であることを確認した。
　また、得られた焼結体のバルク比抵抗（導電性）を抵抗率計（三菱化学（株）製、ロレスタ）を使用して四探針法（ＪＩＳ　Ｒ　１６３７）に基づき測定した。結果を表１に示す。表１に示すように実施例１～４の焼結体のバルク比抵抗は、１０ｍΩｃｍ以下であった。 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 mΩcm or less.
［焼結体の分析］
　得られた焼結体についてＩＣＰ－ＡＥＳ分析を行い、表１に示す原子比であることを確認した。
　また、得られた焼結体についてＸ線回折（ＸＲＤ）測定装置により結晶構造を調べた。ＸＲＤの測定条件は以下のとおりである。 [Analysis of sintered body]
The obtained sintered body was subjected to ICP-AES analysis, and the atomic ratios shown in Table 1 were confirmed.
In addition, the crystal structure of the obtained sintered body was examined using an X-ray diffraction (XRD) measuring device. The measurement conditions of XRD are as follows.
・装置：（株）リガク製Ｕｌｔｉｍａ－ＩＩＩ
・Ｘ線：Ｃｕ－Ｋα線（波長１．５４０６Å、グラファイトモノクロメータにて単色化）
・２θ－θ反射法、連続スキャン（１．０°／分）
・サンプリング間隔：０．０２°
・スリット　ＤＳ、ＳＳ：２／３°、ＲＳ：０．６ｍｍ ・ Equipment: Ultimate-III manufactured by Rigaku Corporation
-X-ray: Cu-Kα ray (wavelength 1.5406mm, monochromatized with graphite monochromator)
・ 2θ-θ reflection method, continuous scan (1.0 ° / min)
・ Sampling interval: 0.02 °
・ Slit DS, SS: 2/3 °, RS: 0.6 mm
　実施例１～４で得られた焼結体のＸ線回折チャートを図１～４に示す。
　チャートを分析した結果、実施例１の焼結体では、Ｉｎ２Ｚｎ３Ｏ６のホモロガス構造とＩｎ２Ｏ３のビックスバイト構造が観測された。
　結晶構造はＪＣＰＤＳカード又はＩＣＳＤで確認することができる。
　Ｉｎ２Ｚｎ３Ｏ６のホモロガス構造はＩＣＳＤ＃１６２４５０であり、Ｉｎ２Ｏ３のビックスバイト構造はＪＣＰＤＳカードＮｏ．０６－０４１６である。 The X-ray diffraction charts of the sintered bodies obtained in Examples 1 to 4 are shown in FIGS.
As a result of analyzing the chart, in the sintered body of Example 1, 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, and the bixbite structure of In 2 O 3 is JCPDS card no. 06-0416.
　実施例１について、Ｘ線回折チャートからＩｎ２Ｚｎ３Ｏ６に帰属される結晶相の軸長は、ａ軸：３．３３２Å、ｂ軸：３．３３２Å、ｃ軸：４２．２５２Åであるのに対して、ＩＣＳＤ＃１６２４５０から確認できるＩｎ２Ｚｎ３Ｏ６で表されるホモロガス構造の結晶相の軸長は、ａ軸：３．３５２Å、ｂ軸：３．３５２Å、ｃ軸：４２．４８８Åであり、ＪＣＰＤＳカードＮｏ．４０－０２６０から確認できるＩｎＡｌＺｎ３Ｏ６で表されるホモロガス構造の結晶相の軸長はａ軸：３．２８１Å、ｂ軸：３．２８１Å、ｃ軸：４１．３５Åであることから、ＡｌがＩｎ２Ｚｎ３Ｏ６に固溶していることがわかる。
　ＸＲＤの結果から、実施例２～４に関してもＩｎ２Ｚｎ３Ｏ６で表わされるホモロガス構造化合物とＩｎ２Ｏ３で表わされるビックス構造化合物が含まれることが分かった。 Regarding Example 1, 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. On the other hand, 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: 3.352Å, c-axis: 42.488Å. JCPDS card No. 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: 3.281Å, and c-axis: 41.35Å. 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.
　実施例１～４の焼結体では、Ｉｎ２Ｏ３（ＺｎＯ）ｍ（ｍは整数）で表わされるホモロガス構造化合物とＩｎ２Ｏ３で表わされるビックスバイト構造化合物が同時に形成されているため、焼結体密度が９８％であり、かつバルク比抵抗が１０ｍΩｃｍであることが分かった。また、得られたＸ線回折チャートから算出されるＩｎ２Ｏ３（ＺｎＯ）ｍの結晶相の軸長はいずれも、対応するＪＣＰＤＳカード又はＩＣＳＤに記載のＩｎ２Ｏ３（ＺｎＯ）ｍの結晶相の軸長よりも小さく、対応するＪＣＰＤＳカード又はＩＣＳＤに記載のＩｎＡｌＯ３（ＺｎＯ）ｍの結晶相の軸長よりも大きいことから、ＡｌがＩｎ２Ｏ３（ＺｎＯ）ｍに固溶していることがわかる。 In the sintered bodies of Examples 1 to 4, 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 mΩcm. In addition, 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. Since it is smaller than the axial length of the phase and larger than the axial length of the crystal phase of InAlO 3 (ZnO) m described in the corresponding JCPDS card or ICSD, Al is dissolved in In 2 O 3 (ZnO) m. I understand that.
［スパッタリングターゲットの製造］
　実施例１～４で得られた焼結体の表面を平面研削盤で研削し、側辺をダイヤモンドカッターで切断し、バッキングプレートに貼り合わせ、それぞれ直径４インチのスパッタリングターゲットを作製した。
　また、それぞれ幅２００ｍｍ、長さ１７００ｍｍ、厚さ１０ｍｍの６枚のターゲットをＡＣスパッタリング成膜用に作製した。 [Manufacture of sputtering target]
The surfaces of the sintered bodies obtained in Examples 1 to 4 were ground with a surface grinder, the sides were cut with a diamond cutter, and bonded to a backing plate to produce sputtering targets each having a diameter of 4 inches.
In addition, six targets each having a width of 200 mm, a length of 1700 mm, and a thickness of 10 mm were prepared for AC sputtering film formation.
［異常放電の有無の確認］
　得られた直径４インチのスパッタリングターゲットをＤＣスパッタリング装置に装着し、雰囲気としてアルゴンガスに水蒸気を分圧比で２％添加した混合ガスを使用し、スパッタ圧０．４Ｐａ、基板温度を室温とし、ＤＣ出力４００Ｗにて、１０ｋＷｈ連続スパッタを行った。スパッタ中の電圧変動をデータロガーに蓄積し、異常放電の有無を確認した。結果を表１に示す。 [Check for abnormal discharge]
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.
　尚、上記異常放電の有無は、電圧変動をモニターして異常放電を検出することにより行った。具体的には、５分間の測定時間中に発生する電圧変動がスパッタ運転中の定常電圧の１０％以上あった場合を異常放電とした。特にスパッタ運転中の定常電圧が０．１秒間に±１０％変動する場合は、スパッタ放電の異常放電であるマイクロアークが発生しており、素子の歩留まりが低下し、量産化に適さないおそれがある。 Note that the presence or absence of the abnormal discharge was performed by monitoring the voltage fluctuation and detecting the abnormal discharge. Specifically, 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. In particular, when 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.
［ノジュール発生の有無の確認］
　また、得られた直径４インチのスパッタリングターゲットを用いて、雰囲気としてアルゴンガスに水素ガスを分圧比で３％添加した混合ガスを使用し、４０時間連続してスパッタリングを行い、ノジュールの発生の有無を確認した。
　尚、スパッタ条件は、スパッタ圧０．４Ｐａ、ＤＣ出力１００Ｗ、基板温度は室温とした。水素ガスは、ノジュールの発生を促進するために雰囲気ガスに添加した。 [Check for nodule occurrence]
In addition, using the obtained sputtering target having a diameter of 4 inches, using a mixed gas obtained by adding 3% of hydrogen gas to argon gas at a partial pressure ratio, sputtering was performed continuously for 40 hours, and no nodules were generated. It was confirmed.
The sputtering conditions were a sputtering pressure of 0.4 Pa, a DC output of 100 W, and a substrate temperature of room temperature. Hydrogen gas was added to the atmospheric gas to promote the generation of nodules.
　ノジュールは、円形のスパッタリングターゲットの中心点（１箇所）と、その中心点で直交する２本の中心線上の中心点と周縁部との中間点（４箇所）の合計５箇所において、スパッタリング後のターゲット表面の変化を実体顕微鏡により５０倍に拡大して観察し、視野３ｍｍ２中に発生した長径２０μｍ以上のノジュールについて数平均を計測する方法を採用した。発生したノジュール数を表１に示す。実施例１～４のスパッタリングターゲット表面において、ノジュールは観測されなかった。 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 μm 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.
比較例１～２
　表１に示す原子比（百分率）で原料粉末を混合し、表１に示す焼結温度、焼結時間で焼結した他は、実施例１と同様に焼結体及びスパッタリングターゲットを製造し、評価した。結果を表１に示す。
　比較例１のスパッタリングターゲットにおいて、スパッタ時に異常放電が発生し、ターゲット表面にはノジュールが観測された。
　比較例２のスパッタリングターゲットは、抵抗が高く、スパッタリングすることができなかった。 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.
　比較例１のスパッタリングターゲットには、ＺｎＯのウルツ構造、ＺｎＡｌ２Ｏ４のスピネル構造が観測された。
　ＺｎＯのウルツ構造はＩＣＳＤ＃５７１５６であり、ＺｎＡｌ２Ｏ４のスピネル構造はＪＣＰＤＳカードＮｏ．０５－０６６９で確認することができる。 In the sputtering target of Comparative Example 1, a ZnO wurtz structure and a ZnAl 2 O 4 spinel structure were observed.
The ZnO wurtz structure is ICSD # 57156, and the spinel structure of ZnAl 2 O 4 is JCPDS card no. It can be confirmed at 05-0669.
　比較例２のスパッタリングターゲットには、Ｉｎ２Ｏ３のビックスバイト構造、Ａｌ２Ｏ３のコランダム構造が確認された。
　Ｉｎ２Ｏ３のビックスバイト構造はＪＣＰＤＳカードＮｏ．０６－０４１６で、Ａｌ２Ｏ３のコランダム構造はＪＣＰＤＳカードＮｏ．１０－１７３で確認することができる。 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.
　比較例の焼結体では、Ｉｎ２Ｏ３（ＺｎＯ）ｍ（ｍは整数）で表わされるホモロガス構造化合物とＩｎ２Ｏ３で表わされるホモロガス構造化合物が同時に観測されず、またＡｌ２Ｏ３やＺｎＯが観測されたため、焼結体の密度が低下し、バルク抵抗が増大することが分かった。その結果、ノジュールが発生したり、スパッタリングが不可能となったりしたと考えられる。 In the sintered body of the comparative example, 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.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
実施例５～８
［酸化物半導体薄膜の製造］
　マグネトロンスパッタリング装置に、実施例１～４で作製した表２に示す組成の４インチターゲットを装着し、基板としてスライドガラス（コーニング社製♯１７３７）をそれぞれ装着した。ＤＣマグネトロンスパッタリング法により、スライドガラス上に膜厚５０ｎｍの非晶質膜を成膜した。成膜時には、表２に示す分圧比（％）でＡｒガス、Ｏ２ガス、及び水蒸気を導入した。 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. At the time of film formation, Ar gas, O 2 gas, and water vapor were introduced at a partial pressure ratio (%) shown in Table 2.
　スパッタ条件は以下のとおりである。
・基板温度：２５℃（但し、実施例６は８０℃）
・到達圧力：８．５×１０－５Ｐａ
・雰囲気ガス：Ａｒガス、Ｏ２ガス、水蒸気（分圧比は表２を参照）
・スパッタ圧力（全圧）：０．４Ｐａ
・投入電力：ＤＣ１００Ｗ
・Ｓ（基板）－Ｔ（ターゲット）距離：７０ｍｍ 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
　次いで、非晶質膜を形成した基板を、大気中、３００℃で６０分加熱して酸化物半導体膜を形成した。この酸化物半導体膜が形成されたガラス基板をホール効果測定用素子として用いてＲｅｓｉＴｅｓｔ８３００型（東陽テクニカ社製）にセットし、室温でホール効果を評価した。結果を表２に示す。
　また、ＩＣＰ－ＡＥＳ分析により、酸化物半導体薄膜に含まれる各元素の原子比がスパッタリングターゲットと同じであることを確認した。 Next, 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. Using the glass substrate on which this oxide semiconductor film was formed as an element for measuring the Hall effect, it 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.
　さらに、ガラス基板上に成膜した薄膜についてＸ線回折測定装置により結晶構造を調べた。実施例５～８では、薄膜堆積直後は回折ピークが観測されず非晶質であることを確認した。また、大気中、３００℃で６０分加熱処理（アニール）した後も回折ピークが観測されず非晶質であることを確認した。
　ＸＲＤの測定条件は以下のとおりである。 Furthermore, the crystal structure of the thin film formed on the glass substrate was examined using an X-ray diffraction measurement apparatus. In Examples 5 to 8, 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.
・装置：（株）リガク製Ｕｌｔｉｍａ－ＩＩＩ
・Ｘ線：Ｃｕ－Ｋα線（波長１．５４０６Å、グラファイトモノクロメータにて単色化）
・２θ－θ反射法、連続スキャン（１．０°／分）
・サンプリング間隔：０．０２°
・スリット　ＤＳ、ＳＳ：２／３°、ＲＳ：０．６ｍｍ ・ Equipment: Ultimate-III manufactured by Rigaku Corporation
-X-ray: Cu-Kα ray (wavelength 1.5406mm, monochromatized with graphite monochromator)
・ 2θ-θ reflection method, continuous scan (1.0 ° / min)
・ Sampling interval: 0.02 °
・ Slit DS, SS: 2/3 °, RS: 0.6 mm
［薄膜トランジスタの製造］
　基板として、膜厚１００ｎｍの熱酸化膜付きの導電性シリコン基板を使用した。熱酸化膜がゲート絶縁膜として機能し、導電性シリコン部がゲート電極として機能する。
　表２に示す成膜条件、上記のスパッタ条件にて、スパッタ成膜し、ゲート絶縁膜上に膜厚５０ｎｍの非晶質薄膜を作製した。レジストとしてＯＦＰＲ♯８００（東京応化工業株式会社製）を使用し、塗布、プレベーク（８０℃、５分）、露光した。現像後、ポストベーク（１２０℃、５分）し、シュウ酸にてエッチングし、所望の形状にパターニングした。その後、熱風加熱炉内にて３００℃で６０分加熱処理（アニール処理）を行った。 [Manufacture of thin film transistors]
As the substrate, a conductive silicon substrate with a thermal oxide film having a thickness of 100 nm was used. The thermal oxide film functions as a gate insulating film, and 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.) was used as a resist, and coating, pre-baking (80 ° C., 5 minutes), and exposure were performed. After development, it was post-baked (120 ° C., 5 minutes), etched with oxalic acid, and patterned into a desired shape. Thereafter, heat treatment (annealing treatment) was performed at 300 ° C. for 60 minutes in a hot air heating furnace.
　その後、リフトオフ法によりＭｏ（１００ｎｍ）をスパッタ成膜により成膜し、ソース／ドレイン電極を所望の形状にパターニングした。さらに保護膜を形成する前段階の処理として、酸化物半導体膜に対し、亜酸化窒素プラズマ処理を施した。その後、プラズマＣＶＤ法（ＰＥＣＶＤ）にてＳｉＯｘを成膜して保護膜とした。フッ酸を用いてコンタクトホールを開口し、薄膜トランジスタを作製した。 Thereafter, Mo (100 nm) was deposited by sputtering using a lift-off method, and the source / drain electrodes were patterned into a desired shape. Further, a nitrous oxide plasma treatment was performed on the oxide semiconductor film as a treatment before the formation of the protective film. After that, a protective film by forming a SiO x by plasma CVD (PECVD). A contact hole was opened using hydrofluoric acid to produce a thin film transistor.
　作製した薄膜トランジスタについて、電界効果移動度（μ）、Ｓ値及び閾値電圧（Ｖｔｈ）を評価した。これらの特性値は、半導体パラメーターアナライザー（ケースレーインスツルメンツ株式会社製４２００ＳＣＳ）を用い、室温、遮光環境下（シールドボックス内）で測定した。
　また、作製したトランジスタについて、ドレイン電圧（Ｖｄ）を１Ｖ及びゲート電圧（Ｖｇ）を－１５～２５Ｖとして伝達特性を評価した。結果を表２に示す。尚、電界効果移動度（μ）は、線形移動度から算出し、Ｖｇ－μの最大値で定義した。 The manufactured thin film transistor was evaluated for field effect mobility (μ), 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 (μ) was calculated from the linear mobility and defined as the maximum value of Vg−μ.
　次に、実施例５～８のＴＦＴに対し、ＤＣバイアスストレス試験を行った。表２に、Ｖｇ＝１５Ｖ、Ｖｄ＝１５ＶのＤＣストレス（ストレス温度８０℃下）を１００００秒印加した前後における、閾値電圧シフト（Ｖｔｈの変化量）ΔＶｔｈを示す。本発明のＴＦＴでは閾値電圧の変動が非常に小さく、ＤＣストレスに対して影響を受けにくいことが分かる。 Next, a DC bias stress test was performed on the TFTs of Examples 5 to 8. Table 2 shows the threshold voltage shift (change amount of Vth) ΔVth before and after applying DC stress (stress temperature of 80 ° C.) of Vg = 15V and Vd = 15V for 10,000 seconds. It can be seen that the threshold voltage variation of the TFT of the present invention is very small and is hardly affected by DC stress.
比較例３
　比較例１で作製した４インチターゲットを用いて実施例５と同様にして酸化物半導体薄膜及び薄膜トランジスタを作製し、評価した。成膜条件及び結果を表２に示す。尚、比較例２のスパッタリングターゲットは、抵抗が高く、スパッタリングは不可能であった。
　表２に示すように、比較例３の素子は電界効果移動度が５ｃｍ２／Ｖｓ未満であり、実施例５～８と比べて大幅に低いことが分かる。
　また、比較例３のＴＦＴに対し、ＤＣバイアスストレス試験を行った。結果を表２に示す。比較例３のＴＦＴでは、閾値電圧が１Ｖ以上変動して著しい特性の劣化が生じた。 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.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
実施例９～１２
　特開２００５－２９０５５０号公報に開示された成膜装置を用い、実施例１～４で作製した表３に示す組成の４インチターゲットについてＡＣスパッタリングを行い、薄膜トランジスタを作製した。成膜条件は表３に示すとおりである。ソース・ドレインパターニングをドライエッチングで行った他は実施例５と同様にして薄膜トランジスタ及び薄膜評価用素子を作製し、評価した。結果を表３に示す。 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スパッタリングは、図５に示す装置を用いて行った。実施例１～３で作製した幅２００ｍｍ、長さ１７００ｍｍ、厚さ１０ｍｍの６枚のターゲット３１ａ～３１ｆを、図５に示すようにそれぞれの長さ方向が平行となるよう２ｍｍの間隔で配置した。磁界形成手段４０ａ～４０ｆの幅はターゲット３１ａ～３１ｆと同じ２００ｍｍであった。ガス供給系からスパッタガスであるＡｒ並びに、水蒸気及び／又はＯ２をそれぞれ系内に導入した。 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.
　例えば実施例９では、成膜雰囲気は０．５Ｐａ、交流電源のパワーは３Ｗ／ｃｍ２（＝１０．２ｋＷ／３４００ｃｍ２）とし、周波数は１０ｋＨｚとした。
　以上の条件で成膜速度を調べるために１０秒成膜し、得られた薄膜の膜厚を測定すると８ｎｍであった。成膜速度は４８ｎｍ／分と高速であり、量産に適していた。
　また、ＩＣＰ－ＡＥＳ分析により、酸化物薄膜に含まれる各元素の原子比がスパッタリングターゲットと同じであることを確認した。 For example, in Example 9, the film forming atmosphere was 0.5 Pa, the power of the AC power source was 3 W / cm 2 (= 10.2 kW / 3400 cm 2 ), and the frequency was 10 kHz.
In order to investigate the film formation speed under the above conditions, 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.
　また、このようにして得られた膜厚５０ｎｍの薄膜付きガラス基板を電気炉に入れ、空気中３００℃、６０分（大気雰囲気下）の条件で熱処理後、１ｃｍ２のサイズに切出し、４探針法によるホール測定を行った。その結果、キャリア濃度が７．３×１０１７ｃｍ－３となり、十分半導体化していることが確認できた。
　また、ＸＲＤ測定から薄膜堆積直後は非晶質であり、空気中３００℃、６０分の熱処理後も非晶質であることを確認した。 Further, 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.
比較例４
　比較例１で作製した幅２００ｍｍ、長さ１７００ｍｍ、厚さ１０ｍｍの６枚のターゲットを用いて成膜条件を、表３に記載のものに変更した他は実施例９と同様にして酸化物半導体薄膜、薄膜評価用素子及び薄膜トランジスタを作製し、評価した。結果を表３に示す。
　表３に示すように、比較例４の素子は電界効果移動度が１０ｃｍ２／Ｖｓ未満であり、実施例９～１２と比べて大幅に電界効果移動度が低いことが分かる。 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.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　本発明のスパッタリングターゲットは、酸化物半導体や透明導電膜等の酸化物薄膜の作製に使用できる。また、本発明の酸化物薄膜は、透明電極、薄膜トランジスタの半導体層、酸化物薄膜層等に使用できる。 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.
　上記に本発明の実施形態及び／又は実施例を幾つか詳細に説明したが、当業者は、本発明の新規な教示及び効果から実質的に離れることなく、これら例示である実施形態及び／又は実施例に多くの変更を加えることが容易である。従って、これらの多くの変更は本発明の範囲に含まれる。
　本願のパリ優先の基礎となる日本出願明細書の内容を全てここに援用する。 Although several embodiments and / or examples of the present invention have been described in detail above, those skilled in the art will appreciate that these exemplary embodiments and / or embodiments are substantially without departing from the novel teachings and advantages of the present invention. It is easy to make many changes to the embodiment. Accordingly, many of these modifications are within the scope of the present invention.
All the contents of the Japanese application specification that is the basis of the priority of Paris in this application are incorporated herein.

Claims (18)

  1. 　インジウム元素（Ｉｎ）、亜鉛元素（Ｚｎ）及びアルミニウム元素（Ａｌ）を含有し、Ｉｎ２Ｏ３で表されるビックスバイト構造化合物とＩｎ２Ｏ３（ＺｎＯ）ｍ（ｍは整数）で表わされるホモロガス構造化合物を含むスパッタリングターゲット。 Indium element (In), represented by containing zinc element (Zn) and aluminum element (Al), bixbyite structure compound represented by In 2 O 3 and In 2 O 3 (ZnO) m (m is an integer) A sputtering target containing a homologous structural compound.
  2. 　前記Ｉｎ２Ｏ３（ＺｎＯ）ｍ（ｍは整数）で表わされるホモロガス構造化合物にＡｌが固溶している請求項１に記載のスパッタリングターゲット。 The sputtering target according to claim 1, wherein Al is dissolved in a homologous structure compound represented by the In 2 O 3 (ZnO) m (m is an integer).
  3. 　前記インジウム元素、亜鉛元素及びアルミニウム元素の原子比が、下記式（１）～（３）を満たす請求項１又は２に記載のスパッタリングターゲット。
    　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）
    （式中、Ｉｎ、Ｚｎ及びＡｌは、それぞれ、スパッタリングターゲット中における各元素の原子比を示す。）     The sputtering target according to claim 1 or 2, wherein an atomic ratio of the indium element, the zinc element, and the aluminum element 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.)
  4. 　相対密度が９８％以上である請求項１～３のいずれかに記載のスパッタリングターゲット。 The sputtering target according to any one of claims 1 to 3, wherein the relative density is 98% or more.
  5. 　バルク比抵抗が１０ｍΩｃｍ以下である請求項１～４のいずれかに記載のスパッタリングターゲット。 The sputtering target according to any one of claims 1 to 4, wherein the bulk specific resistance is 10 mΩcm or less.
  6. 　少なくともインジウム元素（Ｉｎ）、亜鉛元素（Ｚｎ）及びアルミニウム元素（Ａｌ）を混合して混合物を得る混合工程、
    　前記混合物を成形して成形体を得る成形工程、及び
    　前記成形体を焼結する焼結工程を有し、
    　前記焼結工程は、酸素含有雰囲気で、７００～９００℃において１～５時間、温度を保持する仮焼き工程を含む、請求項１～５のいずれかに記載のスパッタリングターゲットの製造方法。     A mixing step of mixing at least indium element (In), zinc element (Zn) and aluminum element (Al) to obtain a mixture;
    A molding step of forming the mixture to obtain a molded body, and a sintering step of sintering the molded body,
    The method for producing a sputtering target according to any one of claims 1 to 5, wherein the sintering step includes a calcining step of maintaining a temperature at 700 to 900 ° C for 1 to 5 hours in an oxygen-containing atmosphere.
  7. 　請求項１～５のいずれかに記載のスパッタリングターゲットを用いて、スパッタリング法により成膜してなる酸化物半導体薄膜。 An oxide semiconductor thin film formed by sputtering using the sputtering target according to any one of claims 1 to 5.
  8. 　水蒸気、酸素ガス及び亜酸化窒素ガスから選択される１以上と希ガスを含有する混合気体の雰囲気下において、請求項１～５のいずれかに記載のスパッタリングターゲットを用いてスパッタリング法で酸化物半導体薄膜を成膜する酸化物半導体薄膜の製造方法。 6. An oxide semiconductor by sputtering using the sputtering target according to claim 1 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. An oxide semiconductor thin film manufacturing method for forming a thin film.
  9. 　前記酸化物半導体薄膜の成膜を、少なくとも水蒸気と希ガスを含有する混合気体の雰囲気下において行う請求項８に記載の酸化物半導体薄膜の製造方法。 The method for producing an oxide semiconductor thin film according to claim 8, wherein the oxide semiconductor thin film is formed in an atmosphere of a mixed gas containing at least water vapor and a rare gas.
  10. 　前記混合気体中に含まれる水蒸気の割合が分圧比で０．１％～２５％である請求項８又は９に記載の酸化物半導体薄膜の製造方法。 10. The method for producing an oxide semiconductor thin film according to claim 8, wherein a ratio of water vapor contained in the mixed gas is 0.1% to 25% in terms of partial pressure ratio.
  11. 　前記混合気体中に含まれる酸素ガスの割合が分圧比で０．１％～５０％である請求項８～１０のいずれかに記載の酸化物半導体薄膜の製造方法。 The method for producing an oxide semiconductor thin film according to any one of claims 8 to 10, wherein a ratio of oxygen gas contained in the mixed gas is 0.1% to 50% in terms of partial pressure ratio.
  12. 　前記酸化物半導体薄膜の成膜を、真空チャンバー内に所定の間隔を置いて並設された３枚以上のターゲットに対向する位置に、基板を順次搬送し、前記各ターゲットに対して交流電源から負電位及び正電位を交互に印加する場合に、前記交流電源からの出力の少なくとも１つを、分岐して接続した２枚以上のターゲットの間で、電位を印加するターゲットの切替を行いながら、ターゲット上にプラズマを発生させて基板表面に成膜するスパッタリング方法で行う請求項８～１１のいずれかに記載の酸化物半導体薄膜の製造方法。 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. The method for producing an oxide semiconductor thin film according to any one of claims 8 to 11, which is performed by a sputtering method in which plasma is generated on a target to form a film on a substrate surface.
  13. 　前記交流電源の交流パワー密度が３Ｗ／ｃｍ２以上、２０Ｗ／ｃｍ２以下である請求項１２に記載の酸化物半導体薄膜の製造方法。 The method for producing an oxide semiconductor thin film according to claim 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. 　前記交流電源の周波数が１０ｋＨｚ～１ＭＨｚである請求項１２又は１３に記載の酸化物半導体薄膜の製造方法。 14. The method for producing an oxide semiconductor thin film according to claim 12 or 13, wherein the frequency of the AC power source is 10 kHz to 1 MHz.
  15. 　請求項７に記載の酸化物半導体薄膜をチャネル層として有する薄膜トランジスタ。 A thin film transistor having the oxide semiconductor thin film according to claim 7 as a channel layer.
  16. 　請求項７に記載の酸化物半導体薄膜の上に、少なくともＳｉＮｘ（ｘは任意の数値）を含有する保護膜を有する薄膜トランジスタ。 A thin film transistor having a protective film containing at least SiNx (x is an arbitrary value) on the oxide semiconductor thin film according to claim 7.
  17. 　電界効果移動度が５ｃｍ２／Ｖｓ以上である請求項１５又は１６に記載の薄膜トランジスタ。 The thin film transistor according to claim 15 or 16, which has a field effect mobility of 5 cm 2 / Vs or more.
  18. 　請求項１５～１７のいずれかに記載の薄膜トランジスタを備える表示装置。 A display device comprising the thin film transistor according to any one of claims 15 to 17.
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