WO2014024975A1 - スパッタリングターゲット及びその製造方法 - Google Patents
スパッタリングターゲット及びその製造方法 Download PDFInfo
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- WO2014024975A1 WO2014024975A1 PCT/JP2013/071516 JP2013071516W WO2014024975A1 WO 2014024975 A1 WO2014024975 A1 WO 2014024975A1 JP 2013071516 W JP2013071516 W JP 2013071516W WO 2014024975 A1 WO2014024975 A1 WO 2014024975A1
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- sputtering target
- powder
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- target
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- 238000005477 sputtering target Methods 0.000 title claims abstract description 155
- 238000004519 manufacturing process Methods 0.000 title claims description 36
- 239000011734 sodium Substances 0.000 claims abstract description 156
- 150000001875 compounds Chemical class 0.000 claims abstract description 113
- 229910052802 copper Inorganic materials 0.000 claims abstract description 51
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 claims abstract description 14
- 239000012535 impurity Substances 0.000 claims abstract description 10
- 235000013024 sodium fluoride Nutrition 0.000 claims abstract description 7
- 239000011775 sodium fluoride Substances 0.000 claims abstract description 7
- VPQBLCVGUWPDHV-UHFFFAOYSA-N sodium selenide Chemical compound [Na+].[Na+].[Se-2] VPQBLCVGUWPDHV-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910052979 sodium sulfide Inorganic materials 0.000 claims abstract description 5
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical compound [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 claims abstract description 5
- 239000000843 powder Substances 0.000 claims description 96
- 238000000034 method Methods 0.000 claims description 54
- 229910052738 indium Inorganic materials 0.000 claims description 53
- 239000002245 particle Substances 0.000 claims description 48
- 229910052733 gallium Inorganic materials 0.000 claims description 47
- 239000011812 mixed powder Substances 0.000 claims description 40
- 229910052751 metal Inorganic materials 0.000 claims description 28
- 239000002184 metal Substances 0.000 claims description 28
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 23
- 229910052760 oxygen Inorganic materials 0.000 claims description 23
- 239000001301 oxygen Substances 0.000 claims description 23
- 239000000758 substrate Substances 0.000 claims description 19
- 238000005245 sintering Methods 0.000 claims description 18
- 239000012298 atmosphere Substances 0.000 claims description 15
- 238000001035 drying Methods 0.000 claims description 15
- 238000005452 bending Methods 0.000 claims description 12
- 229910052708 sodium Inorganic materials 0.000 claims description 11
- 229910002056 binary alloy Inorganic materials 0.000 claims description 9
- 229910002058 ternary alloy Inorganic materials 0.000 claims description 7
- 230000001590 oxidative effect Effects 0.000 claims description 6
- 238000007580 dry-mixing Methods 0.000 claims description 4
- 239000000203 mixture Substances 0.000 abstract description 10
- 229910052731 fluorine Inorganic materials 0.000 abstract description 6
- 229910052711 selenium Inorganic materials 0.000 abstract description 6
- 229910052717 sulfur Inorganic materials 0.000 abstract description 6
- 238000004544 sputter deposition Methods 0.000 description 45
- 230000002159 abnormal effect Effects 0.000 description 31
- 239000010408 film Substances 0.000 description 30
- 238000002156 mixing Methods 0.000 description 24
- 239000010410 layer Substances 0.000 description 22
- 238000002845 discoloration Methods 0.000 description 21
- 230000031700 light absorption Effects 0.000 description 14
- 229910000807 Ga alloy Inorganic materials 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 11
- 239000002994 raw material Substances 0.000 description 9
- 238000010521 absorption reaction Methods 0.000 description 8
- 239000010409 thin film Substances 0.000 description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 239000000523 sample Substances 0.000 description 6
- 229910000846 In alloy Inorganic materials 0.000 description 5
- 238000005520 cutting process Methods 0.000 description 5
- 230000007423 decrease Effects 0.000 description 5
- 238000010298 pulverizing process Methods 0.000 description 5
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
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- 230000003287 optical effect Effects 0.000 description 3
- 239000005361 soda-lime glass Substances 0.000 description 3
- 159000000000 sodium salts Chemical class 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- 239000010935 stainless steel Substances 0.000 description 3
- 229910001220 stainless steel Inorganic materials 0.000 description 3
- 238000007740 vapor deposition Methods 0.000 description 3
- 230000000007 visual effect Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 229910001111 Fine metal Inorganic materials 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 229910052951 chalcopyrite Inorganic materials 0.000 description 2
- -1 chalcopyrite compound Chemical class 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000000110 cooling liquid Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
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- 239000007789 gas Substances 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 238000001755 magnetron sputter deposition Methods 0.000 description 2
- 238000013507 mapping Methods 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 229920006254 polymer film Polymers 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000011163 secondary particle Substances 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 230000003746 surface roughness Effects 0.000 description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000004931 aggregating effect Effects 0.000 description 1
- 235000011114 ammonium hydroxide Nutrition 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- DVRDHUBQLOKMHZ-UHFFFAOYSA-N chalcopyrite Chemical compound [S-2].[S-2].[Fe+2].[Cu+2] DVRDHUBQLOKMHZ-UHFFFAOYSA-N 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
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- 150000002431 hydrogen Chemical class 0.000 description 1
- 230000002706 hydrostatic effect Effects 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
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- 238000012986 modification Methods 0.000 description 1
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- 229910052757 nitrogen Inorganic materials 0.000 description 1
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- 239000000088 plastic resin Substances 0.000 description 1
- 238000013001 point bending Methods 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
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- 239000011164 primary particle Substances 0.000 description 1
- 238000001226 reprecipitation Methods 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 125000004436 sodium atom Chemical group 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- RPACBEVZENYWOL-XFULWGLBSA-M sodium;(2r)-2-[6-(4-chlorophenoxy)hexyl]oxirane-2-carboxylate Chemical compound [Na+].C=1C=C(Cl)C=CC=1OCCCCCC[C@]1(C(=O)[O-])CO1 RPACBEVZENYWOL-XFULWGLBSA-M 0.000 description 1
- 229910000679 solder Inorganic materials 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
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Images
Classifications
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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
- C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
- C23C14/34—Sputtering
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/1003—Use of special medium during sintering, e.g. sintering aid
- B22F3/1007—Atmosphere
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C28/00—Alloys based on a metal not provided for in groups C22C5/00 - C22C27/00
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C30/00—Alloys containing less than 50% by weight of each constituent
- C22C30/02—Alloys containing less than 50% by weight of each constituent containing copper
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
- C22C32/0089—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with other, not previously mentioned inorganic compounds as the main non-metallic constituent, e.g. sulfides, glass
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C9/00—Alloys based on copper
-
- 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
- C23C14/14—Metallic material, boron or silicon
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
- H01L31/0256—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by the material
- H01L31/0264—Inorganic materials
- H01L31/032—Inorganic materials including, apart from doping materials or other impurities, only compounds not provided for in groups H01L31/0272 - H01L31/0312
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
- H01L31/0256—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by the material
- H01L31/0264—Inorganic materials
- H01L31/032—Inorganic materials including, apart from doping materials or other impurities, only compounds not provided for in groups H01L31/0272 - H01L31/0312
- H01L31/0322—Inorganic materials including, apart from doping materials or other impurities, only compounds not provided for in groups H01L31/0272 - H01L31/0312 comprising only AIBIIICVI chalcopyrite compounds, e.g. Cu In Se2, Cu Ga Se2, Cu In Ga Se2
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/541—CuInSe2 material PV cells
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Definitions
- the present invention relates to a sputtering target used for forming a Cu—In—Ga—Se compound film (hereinafter abbreviated as CIGS film) for forming a light absorption layer of a thin film solar cell, and a method for manufacturing the same.
- CIGS film Cu—In—Ga—Se compound film
- This application claims priority on Japanese Patent Application No. 2012-178888 filed in Japan on August 10, 2012, the contents of which are incorporated herein by reference.
- a Mo electrode layer serving as a positive electrode is formed on a soda lime glass substrate, and a light absorption layer composed of a CIGS film is formed on the Mo electrode layer. It has a basic structure in which a buffer layer made of ZnS, CdS or the like is formed thereon, and a transparent electrode layer to be a negative electrode is formed on this buffer layer.
- a method for forming the light absorption layer As a method for forming the light absorption layer, a method of forming a film by vapor deposition is known. Although a light absorption layer obtained by this method can obtain high energy conversion efficiency, film formation by vapor deposition has a vapor deposition rate. Since it is slow, the uniformity of the film thickness distribution tends to decrease when the film is formed on a large-area substrate. Therefore, a method for forming a light absorption layer by a sputtering method has been proposed.
- a Cu—Ga binary alloy film is formed by sputtering using a CuGa alloy target.
- An In film is formed on the CuGa film by sputtering using an In sputtering target, and the resulting precursor film made of the Cu—Ga binary alloy film and the In film is heat-treated in an Se atmosphere.
- a method of forming a CIGS film (so-called selenization method) has been proposed.
- a Cu—Ga—In film is formed by sputtering using a Cu—Ga—In alloy target, and then heat-treated in an Se atmosphere to form a CIGS film.
- a method of forming has also been proposed.
- Non-Patent Document 1 In order to improve the power generation efficiency of the light absorption layer made of the CIGS film, for example, as described in Non-Patent Document 1, it is effective to add Na to the light absorption layer by diffusion from an alkaline glass substrate. ing.
- a flexible CIGS solar cell based on a polymer film or the like instead of alkaline glass, there is an inconvenience that the supply source of Na is lost because there is no alkaline glass substrate.
- Patent Document 2 in order to improve the photoelectric conversion characteristics of the flexible CIGS solar cell formed on the polymer film, a sodium chloride lift-off layer is provided, and Na is diffused from the lift-off layer to the light absorption layer. Propose to let you.
- Non-Patent Documents 1 and 2 propose a method of forming soda-lime glass between the Mo electrode layer and the substrate.
- soda lime glass is attached as in the above non-patent document, the manufacturing process increases and the productivity decreases. Therefore, as shown in Patent Document 3, a technique has been proposed in which sodium salts are added to a Cu—In—Ga (hereinafter referred to as CIG) precursor film to ensure supply of Na to the light absorption layer. . For this reason, it has been considered to add sodium salts to a Cu—In—Ga metal target.
- CIG Cu—In—Ga
- the addition of a large amount of Na salt increases the abnormal discharge during sputtering, and further has the disadvantage that the mechanical strength of the sputtering target is low and it is easily cracked. That is, due to the addition of a large amount of Na salts that are not conductive and difficult to sinter and have low mechanical strength, the mechanical strength of the sputtering target decreases, the incidence of defects during machining increases, and during sputtering, Abnormal discharge due to the Na compound is likely to occur.
- the present invention has been made in view of the above-described problems, and while containing a high concentration of Na, discoloration, generation of spots and abnormal discharge are suppressed, and furthermore, a sputtering target that has high strength and is difficult to break. And it aims at providing the manufacturing method.
- the present inventors have studied so that 0.05 to 15 at% Na can be added to a Cu—In—Ga alloy sputtering target having a Ga concentration of 2 to 30 at% and an In concentration of 15 to 45 at%. As a result, it has been found that the above-mentioned problems can be overcome while adding Na to the sputtering target by selecting raw materials and improving the manufacturing method.
- the present invention has been obtained from the above findings, and the following configuration has been adopted in order to solve the above problems.
- the sputtering target according to the present invention contains Ga: 2 to 30 at%, In: 15 to 45 at%, Na: 0.05 to 15 at% as metal components excluding F, S, and Se of the sputtering target.
- a sintered body having a component composition consisting of Cu and inevitable impurities the sintered body being in a state of a Na compound in which the Na is at least one of sodium fluoride, sodium sulfide and sodium selenide In which the Na compound phase is dispersed, and the average particle size of the Na compound phase is 10 ⁇ m or less.
- the sputtering target of (1) has a theoretical density ratio of the sintered body of 90% or more, a bending strength of 60 N / mm 2 or more, a bulk specific resistance of 0.1 ⁇ ⁇ cm or less, and a sputtering target. Within an area of 1 cm 2 on the surface, an average of 1 or less aggregates of Na compound of 0.05 mm 2 or more may be used.
- the sintered body may have an oxygen content of 50 to 2000 ppm.
- the sputtering target according to any one of (1) to (3) may have an average particle size of the metal phase in the sintered body of 50 ⁇ m or less.
- the method for producing the sputtering target of the present invention is a sintered body containing Cu, Ga, In, Na by sintering a mixed powder of a powder containing Cu, Ga, In and a Na compound powder. Having a sintering process to produce The powder containing Cu, Ga, In is made of a binary or ternary alloy powder made of Cu, Ga, In, or a binary or ternary alloy powder made of Cu, Ga, In and Cu powder. The average particle size of the mixed powder is 1 to 70 ⁇ m.
- the Na compound and the powder containing Cu, Ga, and In may be mixed by a dry mixing method.
- the method for producing a sputtering target according to (5) or (6) includes a step of drying at a temperature of 70 ° C. or higher before the Na compound powder is used as the mixed powder, or before the mixed powder is sintered. And a step of drying at a temperature of 70 ° C. or higher.
- the mixed powder in the sputtering target manufacturing method according to any one of (5) to (7), in the sintering step, the mixed powder may be sintered in a non-oxidizing atmosphere or vacuum.
- Sputtering target has sufficient bending strength and electrical resistance, density is secured, discoloration, generation of spots and abnormal discharge are suppressed while containing Na, and furthermore, sputtering with high strength and hardly breaks.
- a target can be realized.
- the Na content and Ga content of the present invention are based on the entire metal component except F, S, and Se of the sputtering target, and contain Cu, Ga, In, and Na atoms in the target as follows. Calculated as a ratio to the sum of the quantities. Na (at%): Na / (Na + Cu + In + Ga) ⁇ 100% Ga (at%): Ga / (Na + Cu + In + Ga) ⁇ 100% In (at%): In / (Na + Cu + In + Ga) ⁇ 100%
- the reason why the Na content contained in the state of the Na compound is set within the above range is that when the Na content exceeds 15 at%, the mechanical strength of the sputtering target is remarkably lowered, and a sufficient sintered density is ensured. This is because abnormal discharge during sputtering increases at the same time. On the other hand, if the Na content is less than 0.05 at%, the Na content in the film is insufficient, and the intended addition of Na cannot be achieved.
- the sputtering target according to the present invention has a structure in which a Na compound phase is dispersed in a sputtering target substrate, and the average particle diameter of the Na compound phase is 10 ⁇ m or less.
- the average particle diameter is a projected area equivalent circle diameter. Since the sputtering target containing a Na compound contains a Na compound that is an insulator, it is difficult to disperse the Na compound phase by a normal manufacturing method. If microdispersion of the Na compound phase is not properly performed, abnormal discharge called micro-arc is likely to occur when direct current (DC) sputtering is performed.
- DC direct current
- the micro arc does not significantly damage the sputtering target itself, but adversely affects the quality of the film obtained by sputtering.
- the present inventors have found that abnormal micro-arc discharge caused by the Na compound can be significantly reduced when the average particle size of the Na compound is 10 ⁇ m or less. Further, the Na compound located on the surface layer is inevitable to come into contact with the outside air. If the average particle size exceeds 10 ⁇ m, the amount of moisture absorption becomes large, causing discoloration of the target surface.
- the sputtering target of the present invention enables high-speed film formation under DC sputtering or pulsed DC sputtering conditions by optimizing the particle size of the Na compound phase as described above. That is, in the sputtering target of the present invention, the average particle size of each Na compound phase is 10 ⁇ m or less, thereby minimizing the surface discoloration of the target and further suppressing abnormal micro-arc discharge caused by the Na compound. And stable DC sputtering or pulse DC sputtering becomes possible.
- the theoretical density ratio in the sputtering target is 90% or more.
- the open pores connected to the outside air existing in the sputtering target increase, and the Na compound contained in the inside of the sputtering target absorbs moisture from the outside air. This is because the target discolors during storage and use.
- the brittleness tends to increase.
- the bending strength of the target is set to 60 N / mm 2 or more to prevent cracks from being generated during processing and sputtering in target production. Furthermore, when a non-conductive Na compound is added to the sputtering target, abnormal discharge is likely to occur during sputtering, whereas in the present invention, the bulk specific resistance of the target is set to 0.1 ⁇ ⁇ cm or less. To avoid abnormal discharge.
- an aggregate of Na compound of 0.05 mm 2 or more (hereinafter also referred to as Na compound aggregate) has a large contact area with the outside air, so it is particularly easy to absorb moisture. It was found that this was the main cause of discoloration and spots on the sputtering target surface. Such discoloration and spots due to the Na compound aggregates of 0.05 mm 2 or more generated on the surface of the target cannot be removed by pre-sputtering performed at the start of normal sputtering target use, and as a result, in the formed film In this case, impurities (hydrogen, oxygen) are mixed.
- the discharge of adsorbed water by the aggregate during sputtering causes local concentration of the plasma, and a remarkable abnormal discharge occurs around the spots due to the aggregate.
- the high temperature generated by the abnormal discharge evaporates the Na compound having a high vapor pressure and attracts the plasma, so that a hollow abnormal discharge mark is formed in the vicinity of the spotted portion.
- the surface state is remarkably destroyed, and it becomes a state where it cannot be used after one or several abnormal discharges.
- the present invention by limiting the average number of Na compound aggregates of 0.05 mm 2 or more contained in 1 cm 2 area of the sputtering target surface to 1 or less on average, the occurrence of discoloration and spots is suppressed, This makes it possible to prevent impurities from being mixed into the film, the mechanical strength of the sputtering target from being lowered, and the occurrence of abnormal discharge during sputtering.
- the sputtering target according to the present invention preferably has an oxygen content of 50 to 2000 ppm. That is, in this sputtering target, since the oxygen content is 50 to 2000 ppm, generation of NaO having high hygroscopicity can be prevented, so that the discoloration of the sputtering target surface can be further suppressed, and the mechanical strength of the sputtering target is reduced. Can be further suppressed.
- oxygen is present in the CuGa sputtering target to which the Na compound is added, the oxygen and the Na compound react gradually to form NaO having high hygroscopicity, causing discoloration of the sputtering target and a decrease in mechanical strength.
- the oxygen content exceeds 2000 ppm, there is a high possibility of causing discoloration of the sputtering target and a decrease in mechanical strength, so the oxygen content was set to 2000 ppm or less.
- the lower limit of the oxygen concentration in the target is set to 50 ppm.
- the average particle size of the metal phase in the sputtering target substrate is 50 ⁇ m or less.
- the sputtering target since the average particle diameter of the metal phase in the sputtering target substrate is 50 ⁇ m or less, even if the theoretical density ratio is 90% or more and the above-mentioned high concentration Na compound is contained, the sputtering target is used. Can maintain good toughness. That is, as described above, in order to minimize moisture absorption of the sputtering target, it is necessary to set the theoretical density ratio of the sputtering target to 90% or more, but the Na target is contained by improving the density of the sputtering target.
- the brittleness of the sputtering target tends to increase. Therefore, in order to maintain the toughness of the sputtering target, it is effective to set the average crystal grain size of the metal phase to 50 ⁇ m or less. When the average particle size exceeds 30 ⁇ m, defects are likely to occur during machining of the sputtering target.
- the manufacturing method of the sputtering target which concerns on this invention has the process of sintering the mixed powder of the powder containing Na compound powder and Cu, Ga, In, and also the powder containing said Cu, Ga, In Is made of a binary or ternary alloy powder made of Cu, Ga, or In or a Cu powder and an average particle diameter of 1 to 70 ⁇ m. Furthermore, in this manufacturing method of a sputtering target, the said Na compound powder and the powder containing Cu, Ga, and In are mixed by the dry-type mixing method which does not use a solvent.
- this manufacturing method of a sputtering target has the process of drying the said Na compound powder at the temperature of 70 degreeC or more before making it into the said mixed powder, or the process of drying mixed powder at the temperature of 70 degreeC or more. Yes.
- the mixed powder in the step of sintering the mixed powder, the mixed powder is sintered in a non-oxidizing atmosphere or vacuum.
- the average particle size of the powder containing Cu, Ga and In is 1 to 70 ⁇ m and mixed with the Na compound powder, so that the Na distribution in the target is uniform while containing Na. Discoloration due to moisture absorption of Na compound, generation of spots and abnormal discharge are suppressed.
- a fine metal powder that is, an alloy containing Cu, Ga, In or a fine metal powder of pure Cu
- a network of metal powder cannot be formed. . Since the mechanical strength of the obtained sputtering target was lowered and the conductivity was sometimes lowered, the average particle size of the powder containing Cu, Ga, and In was set to 1 ⁇ m or more.
- the particle size of the powder containing Cu, Ga, and In when the particle size of the powder containing Cu, Ga, and In is too large, the dispersion of the Na compound becomes insufficient. In addition, aggregates of large Na compounds are formed, causing discoloration in the sputtering target, reduction in mechanical strength, and abnormal discharge during sputtering. Moreover, in the sputtering target manufactured using the powder containing Cu, Ga, and In having a large particle size, the Na compound tends to concentrate on the grain boundary of the metal phase. This also causes discoloration of the target, reduction in mechanical strength, and abnormal discharge. On the other hand, the average particle diameter of the powder containing Cu, Ga, and In was set to 70 ⁇ m or less.
- the Na compound powder and the powder containing Cu, Ga, In are mixed by a dry mixing method that does not use a solvent. Therefore, non-uniform reprecipitation of the Na compound by wet mixing, enlarging of particles, and mixing of moisture and oxygen can be suppressed by wet mixing. Therefore, problems such as moisture and oxygen contained in the solvent and non-uniform precipitation of the Na compound during drying are suppressed, and furthermore, a sputtering target that has high strength and is difficult to crack is produced with less abnormal discharge during sputtering. can do.
- the process of drying at the temperature of 70 degreeC or more, or 70 degreeC after mixing with the said Na compound powder and the said mixed powder It is preferable to have a step of drying at the above temperature.
- it has the process of drying at the temperature of 70 degreeC or more before making Na compound powder into mixed powder, or the process of drying mixed powder at the temperature of 70 degreeC or more is performed. Therefore, while maintaining the dispersibility of the Na compound particles, it is possible to reduce the oxygen content and suppress reaggregation after mixing the raw material powder.
- the manufacturing method of the sputtering target which concerns on this invention is a process which sinters the said mixed powder, and sinters the said mixed powder in non-oxidizing atmosphere or a vacuum. That is, in this sputtering target manufacturing method, the mixed powder is sintered in a non-oxidizing atmosphere or vacuum, so that the oxygen content can be further reduced.
- the present invention has the following effects. That is, according to the sputtering target and the manufacturing method thereof according to the present invention, Ga: 2 to 30 at%, In: 15 to 45 at%, Na: 0.05 to 15 at% are used as metal components excluding F, S, and Se. It has a structure in which the Na compound phase is dispersed in the base of the sputtering target that contains Cu and inevitable impurities, and the average particle size of the Na compound phase is 10 ⁇ m or less. Therefore, while containing Na, moisture absorption discoloration of the sputtering target and abnormal discharge during sputtering are suppressed, and furthermore, the sputtering target has high strength and is difficult to crack. Therefore, it is possible to add Na to the light absorption layer with high mass productivity by forming the light absorption layer of the CIGS thin film solar cell by sputtering using the sputtering target of the present invention. A highly efficient solar cell can be manufactured.
- the sputtering target of this embodiment contains Ga: 2 to 30 at%, In: 15 to 45 at%, Na: 0.05 to 15 at% as a metal component excluding F, S, and Se of the sputtering target, and the balance is It has a component composition consisting of Cu and inevitable impurities, Na is contained in the state of Na compound consisting of at least one of sodium fluoride, sodium sulfide and sodium selenide, and the Na compound phase is dispersed in the target substrate.
- the average particle size of the Na compound phase is 10 ⁇ m or less.
- the sputtering target of the present embodiment has a theoretical density ratio of 90% or more, a bending strength of 100 N / mm 2 or more, a bulk specific resistance of 0.1 ⁇ ⁇ cm or less, and within a 1 cm 2 area of the target surface. It is preferable that the average number of aggregates of Na compounds of 0.05 mm 2 or more is 1 or less. Further, the oxygen content is preferably 50 to 2000 ppm, and the average particle size of the metal phase in the target substrate is preferably 50 ⁇ m or less.
- the target theoretical density ratio measurement is calculated in weight / dimensions. That is, the theoretical density ratio is calculated as follows because the density of the substrate without pores (theoretical density) varies depending on the actual Cu / In / Ga ratio, the type of input raw material, and the sintering conditions.
- a Cu—In—Ga metal mixture was melted at 1200 degrees at a rate similar to the Cu / In / Ga ratio in the target of the present embodiment, casted, and 10 cm ⁇ 10 cm ⁇ obtained by slow cooling. The density of a 10 cm defect-free ingot is measured, and this is defined as the theoretical density of the Cu—In—Ga alloy having the above ratio.
- the theoretical density of Na compound for example, NaF is 2.79 g / cm 3
- Na 2 S is 1.86 g / cm 3
- Na 2 Se is 2.65 g / cm 3 .
- the theoretical density of the sputtering target using the theoretical density of the Cu—In—Ga alloy and the theoretical density of the Na compound, and the contents of Cu, In, Ga and Na compound in the sputtering target of the present embodiment. Calculate Therefore, the theoretical density ratio is obtained by “(target density obtained by weight / size) / theoretical density of target ⁇ 100%”.
- the sintered target is processed according to JIS R1601, and the bending strength (bending strength) is measured. That is, the target is processed into a rod shape having a length of 40 mm, a width of 4 mm, and a thickness of 3 mm, and the bending strength is measured.
- an observation sample is prepared as follows and the particle diameter is calculated. First, an arbitrary part of the sintered sputtering target is cut to produce a block-shaped sample of about 5 ⁇ 10 ⁇ 3 mm. Next, the sample is polished to a surface roughness Ra: 0.5 ⁇ m or less to prepare an observation surface.
- the method for preparing the observation sample for measuring the average particle diameter of the metal phase and the calculation of the average particle diameter are as follows. First, the observation surface of the block-shaped sample is etched by being immersed in an etching solution composed of 50 ml of pure water, 5 ml of hydrogen peroxide solution and 45 ml of ammonia water for 5 seconds. Next, the etched structure is photographed with an optical microscope having a magnification of 250 times. At this time, the cross-sectional area of the crystal in the 500 ⁇ m ⁇ 1000 ⁇ m visual field is calculated and converted into the projected area equivalent circle diameter, and then the average particle diameter of the particles in the visual field is calculated.
- the manufacturing method of the sputtering target of this embodiment has the sintering process which sinters the mixed powder of Na compound powder and the powder containing Cu, In, and Ga, and produces a sintered compact, Cu, In,
- the powder containing Ga is a binary alloy or ternary alloy powder made of Cu, In, Ga, or a binary alloy or ternary alloy powder made of Cu, In, Ga and Cu powder, and has an average particle diameter. Is 1 to 70 ⁇ m.
- the metal element impurity concentration of the powder containing Cu, In, and Ga is preferably 0.1 atomic% or less, and more preferably 0.01 atomic% or less. Furthermore, in order to reduce the oxygen content of the powder containing Cu, In, and Ga, the average particle size is preferably 5 to 70 ⁇ m.
- the Na compound powder has a purity of 95% or more, more preferably 3N or more.
- the primary particle size is 0 in consideration of the mixing with the powder containing Cu, In, and Ga while suppressing the increase in oxygen content.
- a thickness of 0.01 to 1.0 ⁇ m is preferable.
- a wet pulverizing and mixing apparatus that does not use water is preferable.
- a pulverization method using a pulverization and mixing device for example, a ball mill, a jet mill, a Henschel mixer, an attritor, etc.
- the following methods (1) to (3), which are different methods, can be used.
- the average secondary particle diameter of the Na compound obtained by crushing is preferably 1 to 5 ⁇ m.
- the crushing step is preferably performed in a dry environment with a humidity RH of 40% or less.
- the crushed Na compound powder thus obtained is preferably dried at 70 ° C. or higher before mixing as described above.
- this Na compound powder and the powder containing Cu, In, and Ga prepared for the target composition are mixed in a dry environment having a relative humidity RH of 40% or less using a dry mixing device, and the mixed powder and To do.
- the mixing is more preferably performed in a reducing atmosphere.
- the powder containing Cu, In, and Ga prepared in the dried Na compound powder and the target composition Are simultaneously filled in the pulverizing and mixing device, and mixing and crushing of the Na compound powder are simultaneously performed, and the crushing is terminated when the average secondary particle diameter of the Na compound powder becomes 5 ⁇ m or less.
- the mixing is preferably performed in a dry environment with a humidity RH of 40% or less, and more preferably in a reducing atmosphere.
- any of (1) to (3) it is preferable to remove adsorbed moisture from the mixed powder after mixing. For example, drying at 80 ° C. for 3 hours or more in a vacuum environment in a vacuum dryer is effective.
- the raw material powder mixed by any of the above methods (1) to (3) is sealed and stored in a plastic resin bag in a dry environment with a humidity RH of 30% or less. This is to prevent the Na compound from absorbing moisture and aggregating due to moisture absorption.
- the sintering step is preferably performed in a non-oxidizing reducing atmosphere, a vacuum, or an inert gas atmosphere.
- a method for sintering the mixed powder for example, the following three methods can be applied. 1. Fill the mold with the above mixed powder, fill it into a cold-pressed molded body or molded mold, and tap it to form a molded body with a certain bulk density. Alternatively, sintering is performed in a reducing atmosphere.
- tapping is to change the density state of the mixed powder in the mold from a non-uniform state to a uniform state by applying vibration such as hitting a mold, a molded body, or a molding mold. is there.
- the mixed powder has a certain bulk density.
- the mixed powder is hot pressed in a vacuum or an inert gas atmosphere.
- the mixed powder is sintered by the HIP method (hot isostatic pressing).
- the Cu—In—Ga—Na compound sintered body obtained in the above-described sintering step is processed into the specified shape of the target by using ordinary electric discharge machining, cutting, or grinding, and the sputtering of this embodiment is performed.
- a target is created.
- a dry method that does not use a cooling liquid or a wet method that uses a cooling liquid that does not contain water is preferable during processing.
- the processed sputtering target is bonded to a backing plate made of Cu or SUS (stainless steel) or other metal (for example, Mo) using In as solder, and is subjected to sputtering.
- a vacuum pack or a pack obtained by replacing the entire sputtering target with an inert gas in order to prevent oxidation and moisture absorption.
- the sputtering target thus produced is subjected to DC magnetron sputtering using Ar gas as a sputtering gas. At this time, it is preferable to use a pulsed DC power supply to which a pulse voltage is applied, but depending on the Na compound content, sputtering can be performed even with a DC power supply without a pulse.
- the input power during sputtering is preferably 1 to 10 W / cm 2 .
- the sputtering target of the present embodiment has a structure in which the Na compound phase is dispersed in the sputtering target substrate, and the average particle size of the Na compound phase is 10 ⁇ m or less. Discoloration, generation of spots and abnormal discharge are suppressed, and furthermore, a sputtering target that has high strength and is difficult to break can be realized.
- the theoretical density ratio is 90% or more
- the flexural strength is 100 N / mm 2 or more
- the bulk specific resistance is 0.1 ⁇ ⁇ cm or less
- 0.05 mm 2 or more of Na compound in 1 cm 2 area of the target surface By ensuring sufficient target density with an average of 1 or less aggregates of the above, stable sputtering by suppressing abnormal discharge due to Na compound by ensuring the bending strength and electrical resistance and suppressing the aggregates Pulsed DC sputtering becomes possible.
- the sputtering target of this embodiment has an oxygen content of 50 to 2000 ppm, generation of NaO having high hygroscopicity can be prevented, and discoloration and reduction in mechanical strength can be further suppressed.
- the average particle size of the metal phase in the sputtering target substrate of the present embodiment is 50 ⁇ m or less, the toughness of the target is improved even if the theoretical density ratio is 90% or more and a high concentration Na compound is contained. It can be maintained well.
- the average particle size of the powder containing Cu, In, and Ga is set to 1 to 70 ⁇ m, and the sputtering target is manufactured with reduced mechanical strength and conductivity, and the occurrence of discoloration. can do. Furthermore, since it has the process of drying at the temperature of 70 degreeC or more before making Na compound powder into mixed powder, or has the process of drying mixed powder at the temperature of 70 degreeC or more, the dispersibility of the particle
- Cu—In—Ga alloy powder, Cu—In alloy powder, Cu—Ga alloy powder, Cu powder (purity 4N), and primary average particle diameter of purity 3N having the component composition and particle size shown in Table 1 was mixed with Na compound powder of 1 ⁇ m so as to have an amount shown in Table 1, and mixed powders of Examples 1 to 14 were obtained.
- Each of the Cu-In-Ga alloy powder, Cu-In alloy powder, and Cu-Ga alloy powder can be obtained by pulverizing a cast ingot of Cu-In-Ga alloy, Cu-In alloy, or Cu-Ga alloy. It can also be obtained by methods such as law.
- These Na compound powders were directly used for mixing in accordance with the description in Table 1, or dried in the predetermined vacuum environment described above.
- the dried raw material powder was put in a polyethylene pot having a volume of 10 L, and further, zirconia balls having a diameter of 2 mm dried at 80 ° C. for 10 hours, and mixed at a time specified by a ball mill. .
- This mixing was performed in a nitrogen atmosphere.
- a zirconia ball having a diameter of 1 mm is light in weight and has an effect of dispersing and mixing Cu powder, Cu—In—Ga alloy powder, Cu—In alloy powder, and Cu—Ga alloy powder without being crushed.
- Example 14 2 liters of ethanol was added and wet mixing was performed. The mixed powder was dried in a vacuum dryer at 90 ° C. for 16 hours.
- the mixed powder was filled in a metal mold and pressed at room temperature with a pressure of 1500 kgf / cm 2 to form a compact. This molded body was fired in a mixed atmosphere of nitrogen and 3% hydrogen to obtain high-density sintered bodies of Examples 1 to 14.
- hot pressing HP
- the raw material powder was filled in an iron mold and vacuum hot pressing was performed.
- a hydrostatic hot press can be used.
- a molded body is prepared in the same manner as atmospheric pressure sintering, and the molded body is placed in a 0.5 mm thick stainless steel container. It encloses through vacuum deaeration and a HIP process is performed.
- the sintered body thus produced was subjected to dry cutting to produce the sputtering targets of Examples 1 to 14 having a diameter of 125 (mm) ⁇ thickness of 5 (mm).
- sputtering targets of Comparative Examples 1 to 10 were produced under conditions outside the scope of the present invention.
- the sputtering targets of Comparative Examples 9 and 10 after the respective raw materials of In, Ga, and Cu were vacuum-melted, Na compound powder was added, the molten metal was cast into a mold, and a cast body containing the Na compound was manufactured. did.
- the raw material mixed with the powder was vacuum-melted, the molten metal was cast into a mold, and a cast body containing an Na compound was manufactured.
- the average particle diameter of the Na compound phase and the average particle diameter of the metal phase were measured by the above methods.
- the content of Ga and Na in the produced sputtering target was quantitatively analyzed using an ICP method (high frequency inductively coupled plasma method). Further, the target was left at 25 ° C. and 60% humidity for 8 hours, and the surface discoloration was confirmed by visual observation.
- the sputtering target was set in a magnetron sputtering apparatus, and a film having a thickness of 1000 nm was formed on a silicon substrate with an oxide film by pulse DC sputtering with an input power of 8 W / cm 2 .
- the Ar pressure during sputtering was 1.3 Pa, and the distance between the sputtering target and the substrate was 70 mm. Note that the substrate is not heated during film formation.
- continuous sputtering was performed for 10 minutes under the above conditions, and the number of occurrences of micro-arc abnormal discharge was automatically recorded by an arcing counter attached to the sputtering power source. In addition, the number of occurrences of significant abnormal discharge was visually confirmed.
- the continuous sputtering time is set to the time until the plasma disappears or the sputtering is stopped. It was also confirmed whether or not the surface of the sputtering target after sputtering had a trace of abnormal discharge such as melting, voids, and chips.
- the film obtained by the sputtering was peeled off, and the quantitative measurement of Na, Ga, and In in the film was performed using the ICP method. About these evaluation, the result regarding the sputtering target of each said Example and the sputtering target of each comparative example is shown to Table 2, 3 and Table 5,6.
- the number of micro-arc abnormal discharges during sputtering is less than 1000 times, whereas in the sputtering target of the comparative example, both exceed 1000 times. Frequently occur. Further, in the sputtering target of the example, as shown in Table 3, the number of significant abnormal discharges during sputtering is zero, whereas in the sputtering target of the comparative example, all are one or more. It occurs frequently.
- the sputtering target of Example 1 is shown in FIG. 1 as a representative example of an element distribution mapping image by an electron beam microanalyzer (EPMA).
- EPMA images are all color images, but are converted into black and white images in gray scale. The higher the lightness, the higher the content of the measurement element. From these images, it can be confirmed that the sputtering target of this example has a structure in which the Na compound phase is dispersed in the sputtering target substrate.
- the surface roughness is 5 ⁇ m or less and the metal impurity concentration is 0.1 atomic% or less.
- the sputtering targets of the above-described examples satisfies these conditions.
- the technical scope of the present invention is not limited to the above-described embodiment and examples, and various modifications can be made without departing from the spirit of the present invention.
- the sputtering target and the manufacturing method thereof according to the present invention Ga: 2 to 30 at%, In: 15 to 45 at%, Na: 0.05 to 15 at% are contained as metal components excluding F, S, and Se.
- the base of the sputtering target consisting of Cu and inevitable impurities has a structure in which the Na compound phase is dispersed, and the average particle diameter of the Na compound phase is 10 ⁇ m or less. Therefore, while containing Na, moisture absorption discoloration of the sputtering target and abnormal discharge during sputtering are suppressed, and furthermore, the sputtering target has high strength and is difficult to crack. Therefore, it is possible to add Na to the light absorption layer with high mass productivity by forming the light absorption layer of the CIGS thin film solar cell by sputtering using the sputtering target of the present invention. A highly efficient solar cell can be manufactured.
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Abstract
Description
本願は、2012年08月10日に日本に出願された特願2012-178888号について優先権を主張し、その内容をここに援用する。
このため、例えば、特許文献2では、ポリマーフィルム上に形成されたフレキシブルCIGS太陽電池の光電変換特性向上のため、塩化ナトリウムによるリフトオフ層を設けて、このリフトオフ層から光吸収層へとNaを拡散させることを提案している。
そこで、特許文献3に示されているように、Cu-In-Ga(以下、CIGと称する)プリカーサ膜にナトリウム塩類を添加し、光吸収層へのNa供給を確保する技術が提案されている。このため、Cu-In-Gaの金属ターゲットにナトリウム塩類を添加することが考えられた。
特許文献3に記載の製造方法によってスパッタリングターゲットを製造する場合、金属素地のCIGスパッタリングターゲットに非導電性のナトリウム塩類が適切に混入できず、ターゲット表面の変色や斑点が多発し、量産の直流(DC)スパッタリング時にハードアーキングやソフトア―キングといった異常放電が発生しやすく、安定した成膜が確保できないという問題があった。即ち、特許文献3の製造方法では、Na塩類が凝集しやすく、さらに、水分を吸着しやすいため、これによって、スパッタリングターゲットの表面に変色や斑点が多発し、最終的に、このスパッタリングターゲットによって製造した太陽電池の特性が著しく不安定になる不都合があった。
また、大量のNa塩類の添加によって、スパッタリング時に異常放電が多くなり、さらには、スパッタリングターゲットの機械強度が低く、割れやすいという不都合があった。即ち、導電性が無く且つ焼結し難いと共に機械強度が低いNa塩類の大量の添加により、スパッタリングターゲットの機械強度が低下し、機械加工中の欠陥発生率が上がり、しかも、スパッタリング中には、Na化合物に起因する異常放電が発生しやすくなる。
(1)本発明に係るスパッタリングターゲットは、スパッタリングターゲットのF、S、Seを除く金属成分として、Ga:2~30at%、In:15~45at%、Na:0.05~15at%を含有し、残部がCu及び不可避不純物からなる成分組成を有する焼結体であって、前記焼結体は、前記Naがフッ化ナトリウム、硫化ナトリウム及びセレン化ナトリウムのうち少なくとも1種からなるNa化合物の状態で含有されたNa化合物相が分散している組織を有し、該Na化合物相の平均粒径が、10μm以下である。
(2)前記(1)のスパッタリングターゲットは、前記焼結体の理論密度比が90%以上、抗折強度が60N/mm2以上、バルク比抵抗が0.1Ω・cm以下であり、スパッタリングターゲット表面の1cm2面積内に、0.05mm2以上のNa化合物の凝集体が、平均1個以下であってもよい。
(3)前記(1)又は(2)のスパッタリングターゲットは、前記焼結体の酸素含有量が、50~2000ppmであってもよい。
(4)前記(1)乃至(3)いずれかのスパッタリングターゲットは、前記焼結体の素地中における金属相の平均粒径が、50μm以下であってもよい。
(5)本発明のスパッタリングターゲットを製造する方法は、Cu、Ga、Inを含有した粉末とNa化合物粉末との混合粉末を焼結して、Cu、Ga、In、Naを含有した焼結体を作製する焼結工程を有し、
前記Cu、Ga、Inを含有する粉末は、Cu、Ga、Inからなる2元又は3元の合金粉末からなり、或いは、Cu、Ga、Inからなる2元又は3元の合金粉末とCu粉末とからなり、混合粉末の平均粒径が1~70μmである。
(6)前記(5)のスパッタリングターゲットの製造方法では、前記Na化合物とCu、Ga、Inを含有する粉末とは、乾式混合方法によって混合されてもよい。
(7)前記(5)又は(6)のスパッタリングターゲットの製造方法は、前記Na化合物粉末を前記混合粉末とする前に70℃以上の温度で乾燥させる工程、又は、前記混合粉末を焼結前に70℃以上の温度で乾燥させる工程を有してもよい。
(8)前記(5)乃至(7)のいずれかのスパッタリングターゲットの製造方法は、前記焼結工程では、前記混合粉末を非酸化性雰囲気又は真空中で焼結してもよい。
Na(at%):Na/(Na+Cu+In+Ga)×100%
Ga(at%):Ga/(Na+Cu+In+Ga)×100%
In(at%):In/(Na+Cu+In+Ga)×100%
Na化合物を含有するスパッタリングターゲットは、絶縁体であるNa化合物を含有するため、通常の製造方法では、Na化合物相の分散が困難である。Na化合物相のマイクロ分散が適正に行われていないと、直流(DC)スパッタリングを行う際、マイクロ・アークと呼ばれる異常放電が発生しやすい。マイクロ・アークは、程度にもよるが、スパッタリングターゲット自体には大きなダメージを与えないものの、スパッタリングで得られた膜の膜質に悪い影響を及ぼす。本発明者らは、Na化合物の平均粒径が10μm以下になるとNa化合物によるマイクロ・アーク異常放電が顕著に低減できることを突き止めた。また、表層に位置するNa化合物は、外気との接触は不可避であり、その平均粒径が10μmを超えると、吸湿量が大きくなってターゲット表面の変色の原因になる。
一方、スパッタリングターゲットの密度が高く、Na化合物を大量に含有するスパッタリングターゲットにおいては、脆性が増える傾向が強い。これに対し、本発明では、ターゲットの抗折強度を60N/mm2以上とし、ターゲット製造における加工プロセスやスパッタ中に割れが発生すること防止している。
さらに、スパッタリングターゲットに、導電性のないNa化合物が添加されると、スパッタリング中において異常放電が発生しやすくなるのに対し、本発明ではターゲットのバルク比抵抗を0.1Ω・cm以下にすることで異常放電を回避している。
即ち、このスパッタリングターゲットでは、酸素含有量が50~2000ppmであるので、高い吸湿性を有するNaOの発生を防ぐことができるため、スパッタリングターゲット表面の変色をより抑制でき、スパッタリングターゲットにおける機械強度の低下をより抑制することができる。
Na化合物を添加したCuGaスパッタリングターゲット中に酸素が存在すると、酸素とNa化合物とが徐々に反応し、高い吸湿性を持つNaOが形成され、スパッタリングターゲットの変色や機械強度の低下を発生させる。特に、酸素含有量が2000ppmを超えると、スパッタリングターゲットの変色、機械強度の低下を引き起こす可能性が高いため、酸素含有量を2000ppm以下とした。一方、スパッタリングターゲット中の酸素濃度を事実上、50ppm未満にすることは非常に困難であるため、ターゲット中の酸素濃度の下限を50ppmとした。
このスパッタリングターゲットでは、スパッタリングターゲット素地中の金属相の平均粒径が50μm以下であるので、理論密度比が90%以上で、かつ、上記の高濃度のNa化合物を含有していても、スパッタリングターゲットの靭性を良好に維持することができる。即ち、上述したように、スパッタリングターゲットの吸湿を最小限にするために、スパッタリングターゲットの理論密度比を90%以上にする必要があるが、スパッタリングターゲットの密度が向上することで、Na化合物を含有する本発明のスパッタリングターゲットにおいては、スパッタリングターゲットの脆性が増える傾向が強い。そのため、スパッタリングターゲットの靭性を保つために、金属相の平均結晶粒径を50μm以下にすることが有効である。なお、平均粒径が30μmを超えると、スパッタリングターゲットの機械加工時に欠陥が出やすくなる。
さらに、このスパッタリングターゲットの製造方法では、前記Na化合物粉末とCu、Ga、Inを含有する粉末とは溶剤を使用しない乾式混合方法によって混合される。また、このスパッタリングターゲットの製造方法は、前記Na化合物粉末を、前記混合粉末とする前に70℃以上の温度で乾燥させる工程、又は混合粉末を70℃以上の温度で乾燥させる工程を有している。このスパッタリングターゲットの製造方法は、前記混合粉末を焼結する工程で、前記混合粉末を非酸化性雰囲気又は真空中で焼結する。
Na化合物が添加される際に、細かい金属粉(即ち、Cu、Ga、Inを含む合金又は純Cuの細かい金属粉)と細かいNa化合物粉とを混ぜると、却って金属粉のネットワークが形成できなくなる。得られたスパッタリングターゲットの機械強度が低下し、導電性が低下する場合もあるため、Cu、Ga、Inを含有する粉末の平均粒径を1μm以上とした。
一方、Cu、Ga、Inを含有する粉末の粒径が大きすぎると、Na化合物の分散が不十分になる。また、大きなNa化合物の凝集体が形成され、スパッタリングターゲットにおける変色、機械強度の低下、スパッタリング時の異常放電の原因になる。また、大きい粒径のCu、Ga、Inを含有する粉末を用いて製造したスパッタリングターゲットでは、Na化合物が金属相の粒界に集中しやすい。これもターゲットの変色、機械強度の低下、異常放電の原因になる。これに対し、Cu、Ga、Inを含有する粉末の平均粒径を70μm以下とした。
これらのスパッタリングターゲットの製造方法では、Na化合物粉末を混合粉末とする前に70℃以上の温度で乾燥させる工程を有する、又は混合粉末を、70℃以上の温度で乾燥させる工程のいずれか一方を有するので、Na化合物の粒子の分散性を維持しつつ、酸素含有量の低減を図ると共に原料粉末の混合後における再凝集を抑制することができる。
すなわち、このスパッタリングターゲットの製造方法では、混合粉末を非酸化性雰囲気又は真空中で焼結するので、より酸素含有量を低減することができる。
すなわち、本発明に係るスパッタリングターゲット及びその製造方法によれば、F、S、Seを除く金属成分として、Ga:2~30at%、In:15~45at%、Na:0.05~15at%を含有し、残部がCu及び不可避不純物からなるスパッタリングターゲットの素地中に、Na化合物相が分散している組織を有し、前記Na化合物相の平均粒径が10μm以下である。よって、Naを含有しつつも、スパッタリングターゲットの吸湿変色や、スパッタリング時の異常放電が抑制され、さらには、スパッタリングターゲットの高強度を有して割れ難い。従って、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CIGS薄膜型太陽電池の光吸収層を成膜することで、高い量産性を有して、光吸収層へNaを添加することができ、発電効率の高い太陽電池を製造することが可能となる。
本実施形態のスパッタリングターゲットは、スパッタリングターゲットのF、S、Seを除く金属成分として、Ga:2~30at%、In:15~45at%、Na:0.05~15at%を含有し、残部がCu及び不可避不純物からなる成分組成を有し、Naがフッ化ナトリウム、硫化ナトリウム及びセレン化ナトリウムのうち少なくとも1種からなるNa化合物の状態で含有され、ターゲット素地中にNa化合物相が分散している組織を有し、Na化合物相の平均粒径が10μm以下である。
さらに、酸素含有量が50~2000ppmであることが好ましいと共に、ターゲット素地中の金属相の平均粒径が50μm以下であることが好ましい。
ターゲットの理論密度比の測定は、重量/寸法で計算する。
すなわち、理論密度比については、実際のCu/In/Ga割合および投入原料の種類、焼結条件により、気孔のない素地の密度(理論密度)が変わるため、以下のように計算する。
まず、本実施形態のターゲット中のCu/In/Ga比と同様な割合で、Cu-In-Ga金属混合物を1200度で溶解し、それを鋳造し、徐冷で得られた10cm×10cm×10cmの無欠陥の鋳塊の密度を測定し、これを上記割合のCu-In-Ga合金の理論密度とする。
Na化合物、例えば、NaFの理論密度を2.79g/cm3、Na2Sを1.86g/cm3、Na2Seを2.65g/cm3とする。以上のCu-In-Ga合金の理論密度及びNa化合物の理論密度と、本実施形態のスパッタリングターゲット中のCu、In、Gaの含有量及びNa化合物含有量とを用いて、スパッタリングターゲットの理論密度を計算する。
従って、理論密度比は、「(重量/寸法で得られたターゲット密度)/ターゲットの理論密度×100%」で求められる。
抗折強度については、焼結したターゲットをJIS R1601に従って加工し、曲げ強さ(抗折強度)を測定する。すなわち、ターゲットを、長さ40mm×幅4mm×厚み3mmの棒状に加工し、抗折強度を測定する。
電気抵抗については、4探針法を用いて測定する。
<凝集体について>
凝集体のサイズ測定については、10倍光学顕微鏡でターゲット表面100cm2面積を観察し、写真撮影する(例えば、図2の写真を参照)。そして、この写真に写し出された黒い点によって、凝集体サイズを計算し、0.05mm2以上のNa化合物凝集体の数をカウントする。さらに、凝集体がNa化合物であることをSEMのEDX機能で確認する。また、ターゲット表面1cm2面積内に存在する0.05mm2以上のNa化合物凝集体の平均個数は、ターゲット表面100cm2面積内の平均で計算する。
次に、スパッタリングターゲット素地中のNa化合物相の平均粒径については、測定を行うにあたっては、以下のように観察用サンプルを作製し、その粒径の計算を行う。
まず、焼結したスパッタリングターゲットの任意部位を切断し、約5×10×3mmのブロック状サンプルを作成する。次に、該サンプルを表面粗さRa:0.5μm以下まで研磨し、観察面を作製する。さらに、観察面をSEMにて1000倍で複数枚の写真撮影をし、1000μm×1000μmの範囲中におけるNa化合物相の断面積を計算し、投影面積円相当径に換算したのち、上記視野中の粒子の平均粒径を計算する。
上記金属相の平均粒径を測定するための観察用サンプルの作製方法および平均粒径の計算は、以下の通りである。
まず、上記ブロック状サンプルの観察面を、純水50ml、過酸化水素水5ml及びアンモニア水45mlからなるエッチング液に5秒間浸漬してエッチングする。次に、エッチング面を250倍の光学顕微鏡で、合金組織を撮影する。このとき、500μm×1000μm視野中の結晶の断面積を計算し、投影面積円相当径に換算したのち、上記視野中の粒子の平均粒径を計算する。
次に、上記本実施形態のスパッタリングターゲットを製造する方法について説明する。
本実施形態のスパッタリングターゲットの製造方法は、Na化合物粉末とCu、In、Gaを含有する粉末との混合粉末を焼結して焼結体を作製する焼結工程を有し、Cu、In、Gaを含有する粉末は、Cu、In、Gaからなる2元合金又は3元合金粉末、或いは、Cu、In、Gaからなる2元合金又は3元合金粉末とCu粉末とからなり、平均粒径が1~70μmである。Cu、In、Gaを含有する粉末の金属元素不純物濃度は0.1原子%以下が好ましく、さらに、0.01原子%以下がより好ましい。さらに、Cu、In、Gaを含有する粉末の酸素含有量を低減させるため、平均粒径が5~70μmであることが好ましい。
Na化合物粉末は、純度が95%以上、さらには、3N以上が好ましく、酸素含有量の上昇を抑えると共にCu、In、Gaを含有する粉末との混合性を考慮して、一次粒子径が0.01~1.0μmのものが好ましい。
また、ターゲット中の酸素含有量を2000ppm以下にするために、Na化合物中の吸着水分を、混合する前に予め70℃の乾燥環境で取り除くことが好ましい。例えば、真空乾燥機中で真空環境にて120℃、10時間の乾燥が有効である。
なお、Na化合物は、吸湿性が強く且つ水に溶解されるので、水を使わない湿式の粉砕混合装置が好ましい。
Na化合物粉末とCu、In、Gaを含有する粉末との混合粉末を用意するには、粉砕混合装置(例えば、ボールミル、ジェットミル、ヘンシェルミキサー、アトライター等)を用いた解砕方法や、混合方法の異なる、以下の(1)~(3)の方法が利用できる。
(1)Na化合物粉末の解砕と、Cu、In、Gaを含有する粉末との混合とを別個に実施する場合
解砕によって得られるNa化合物の平均二次粒子径は1~5μmが好ましい。解砕工程は、湿度RH:40%以下の乾燥した環境で行うことが好ましい。こうして得られた解砕後のNa化合物粉末は、上述の通り、混合前に70℃以上で乾燥することが好ましい。
次に、このNa化合物粉末とターゲット組成に調製したCu、In、Gaを含有する粉末とを、乾式混合装置を用いて相対湿度RH:40%以下の乾燥した環境にて混合し、混合粉末とする。なお、混合は還元性雰囲気中で行うことがさらに好ましい。
乾燥済みNa化合物粉末とターゲット組成に調製したCu、In、Gaを含有する粉末とを、同時に粉砕混合装置に充填し、混合とNa化合物粉末の解砕とを同時に行い、Na化合物粉末の平均二次粒子径が5μm以下になる時点で解砕を終了する。なお、上記混合は、湿度RH:40%以下の乾燥した環境にて行うことが好ましく、還元性雰囲気中で行うことがさらに好ましい。
まず、ターゲット組成のCu/In/Gaの割合よりもGa又はInの含有量の多いCu、In、Gaを含有する粉末(高GaIn粉末とする)と、ターゲット組成のCu/In/Gaの割合よりもGa又はInの含有量の少ないCu、In、Gaを含有する粉末又はCu粉(低GaIn粉末とする)を用意する。
高GaIn粉末を乾燥済みのNa化合物粉末と混合してから、さらに低GaIn粉末を追加し、均一になるように混合して混合粉末とする。
以上の混合は、すべて上記(1)および(2)のような低湿度環境で行う。なお、還元性雰囲気中で行うことがさらに好ましい。
次に、このように上記(1)~(3)のいずれかの方法で混合した原料粉末を、湿度RH:30%以下の乾燥環境でプラスチック樹脂性の袋に封入し保管する。これは、Na化合物の吸湿や吸湿による凝集を防止するためである。
Cu-In-Ga粉末の焼結中の酸化防止のため、焼結工程は、非酸化性の還元性雰囲気中、真空中又は不活性ガス雰囲気中で行うことが好ましい。
上記混合粉末を焼結する方法としては、例えば、以下の3つの方法が適用できる。
1.上記混合粉末を金型に充填し、冷間にてプレス成形した成形体あるいは成形モールドに充填し、タッピングして一定のかさ密度を有する成形体を形成し、それを真空中、不活性ガス中又は還元性雰囲気中において焼結する。ここで、タッピングとは、金型、成形体、又は成形モールドを叩くなどの振動を与え、金型等の中の混合粉末の密度の状態を不均一な状態から一様な状態に変えることである。これよって、混合粉末は一定のかさ密度を有する。
2.上記混合粉末を真空又は不活性ガス雰囲気中でホットプレスする。
3.上記混合粉末をHIP法(熱間静水圧プレス法)で焼結する。
次に、上記焼結工程で得たCu-In-Ga-Na化合物焼結体は、通常放電加工、切削加工又は研削加工を用いて、ターゲットの指定形状に加工することで本実施形態のスパッタリングターゲットが作製される。このとき、Na化合物は水に溶解するため、加工の際、冷却液を使わない乾式法又は水を含まない冷却液を使用する湿式法が好ましい。また、湿式法で予め加工した後、さらに乾式法で表面を精密加工する方法もある。
なお、加工済みのスパッタリングターゲットを保管する際には、酸化、吸湿を防止するため、スパッタリングターゲット全体を真空パック又は不活性ガス置換したパックを施すことが好ましい。
このように作製したスパッタリングターゲットは、ArガスをスパッタガスとしてDCマグネトロンスパッタリングに供する。このとき、パルス電圧を付加するパルスDC電源を用いることが好ましいが、Na化合物含有量によっては、パルスなしのDC電源でもスパッタリングも可能である。また、スパッタリング時の投入電力は、1~10W/cm2が好ましい。
このように、本実施形態のスパッタリングターゲットでは、スパッタリングターゲット素地中にNa化合物相が分散している組織を有し、Na化合物相の平均粒径が10μm以下であるので、Naを含有しつつも変色、斑点の発生や異常放電が抑制され、さらには高強度を有して割れ難いスパッタリングターゲットを実現できる。
さらに、本実施形態のスパッタリングターゲットでは、酸素含有量が50~2000ppmであるので、高い吸湿性を有するNaOの発生を防ぎ、より変色や機械強度の低下を抑制することができる。
また、本実施形態のスパッタリングターゲット素地中の金属相の平均粒径が50μm以下であるので、理論密度比が90%以上で、かつ高濃度のNa化合物を含有していても、ターゲットの靭性を良好に維持することができる。
さらに、Na化合物粉末を混合粉末とする前に70℃以上の温度で乾燥させる工程を有する、又は混合粉末を70℃以上の温度で乾燥させる工程を有するので、Na化合物の粒子の分散性を維持しつつ、酸素含有量の低減を図ると共に原料粉末の混合後における再凝集を抑制することができる。
まず、表1に示される成分組成および粒径を有するCu-In-Ga合金粉末、Cu-In合金粉末、Cu-Ga合金粉末と、Cu粉末(純度4N)と、純度3Nで一次平均粒子径が1μmのNa化合物粉末とを、表1に示される量になるように配合し、実施例1~14の混合粉末を得た。Cu-In-Ga合金粉末、Cu-In合金粉末、Cu-Ga合金粉末のそれぞれは、Cu-In-Ga合金、Cu-In合金、Cu-Ga合金の鋳造インゴットを粉砕し得られるが、アトマイズ法などの方法によっても得られる。これらのNa化合物粉末を、表1の記述に従って直接に混合に用いるか、上述した所定の真空環境にて乾燥させた。その後、表1の通り、乾燥させた上記原料粉末を、容積10Lのポリエチレン製ポットに入れ、さらに80℃、10時間乾燥した直径2mmのジルコニアボールを入れて、ボールミルで指定された時間で混合した。この混合は、窒素雰囲気中で行った。なお、直径1mmのジルコニアボールは重量が軽く、Cu粉末やCu-In-Ga合金粉末、Cu-In合金粉末、Cu-Ga合金粉末をつぶさずに分散混合させる効果を有する。また、ボール対粉末の重量割合は、ボール:粉末=2:1が最も分散効果が良い。実施例14では、エタノールを2リッター添加し、湿式混合を行った。その混合後の粉末は、真空乾燥機で90℃、16時間で乾燥された。
常圧焼結する場合、まず混合粉末を金属製金型に充填し、1500kgf/cm2の圧力にて常温加圧して、成形体を作った。この成形体を、窒素と3%水素との混合雰囲気において焼成し、高密度の実施例1~14の焼結体を得た。
ホットプレス(HP)の場合、原料粉末を鉄製金型に充填して真空ホットプレスを行った。また、静水圧ホットプレス(HIP)を用いることもでき、この場合には、常圧焼結と同様に成形体を作成し、この成形体を0.5mm厚みのステンレス容器に装入した後、真空脱気を経て封入し、HIP処理が行われる。
また、比較のため、表4及び表5に示すように、本発明の範囲から外れた条件で、比較例1~10のスパッタリングターゲットを作製した。
なお、比較例9及び10のスパッタリングターゲットでは、In、Ga、Cuの各々の原料を真空溶解したのち、Na化合物粉末を添加し、溶湯を鋳型に鋳造し、Na化合物を含有する鋳造体を製造した。比較例4のスパッタリングターゲットでは、粉末で混合された原料を真空溶解し、溶湯を鋳型に鋳造し、Na化合物を含有する鋳造体を製造した。
実施例1~14のスパッタリングターゲットと比較例1~10について、切削加工時におけるターゲットの欠け発生の有無を記録し、さらに分析用焼結体の小片について非分散赤外線吸収法にて酸素濃度分析を行った。なお、焼結体の理論密度比は上述の方法で計算した。また、抗折強度は、JIS R1601に従い、変形速度0.5mm/mInで三点曲げ試験で行った。さらに、加工後のターゲット表面100cm2を観察し、0.05mm2以上のNa化合物凝集体の数を計測し、その1cm2面積当たりの平均値を計算した。Na化合物相の平均粒径、金属相の平均粒径を上記の方法で測定した。また、作製したスパッタリングターゲット中のGaとNaとの含有量を、ICP法(高周波誘導結合プラズマ法)を用いて定量分析を行った。さらに、ターゲットを25℃、湿度60%に8時間放置し、目視によって表面の変色を確認した。
スパッタリング後のスパッタリングターゲット表面に溶融、空洞、欠けなどの著しい異常放電の痕跡があるかどうかについても確認した。
上記スパッタリングで得られた膜を剥がし、ICP法を用いて、該膜中のNa、Ga、Inの定量測定を行った。
これらの評価について、上記の各実施例のスパッタリングターゲット及び各比較例のスパッタリングターゲットに関する結果を、表2,3及び表5,6に示す。
また、実施例のスパッタリングターゲットでは、表3に示すように、切削加工時の割れや欠けは、いずれも発生していないのに対し、比較例1、6、9のスパッタリングターゲットでは、表6に示すように、切削加工時の欠けが発生している。なお、比較例4、6、9のスパッタリングターゲットでは、金属相の結晶粒が大きくなったため、チッピングが発生した。
さらに、実施例のスパッタリングターゲットでは、表3に示すように、スパッタリング時のマイクロ・アーク異常放電回数がいずれも1000回未満であるのに対し、比較例のスパッタリングターゲットでは、いずれも1000回を超えて多発している。
さらに、実施例のスパッタリングターゲットでは、表3に示すように、スパッタリング時の著しい異常放電回数がいずれも0回であるのに対し、比較例のスパッタリングターゲットでは、いずれも1回又はそれを超えて多発している。
また、本発明の技術範囲は、上記実施形態及び上記実施例に限定されるものではなく、本発明の趣旨を逸脱しない範囲において種々の変更を加えることが可能である。
Claims (8)
- Ga:2~30at%、In:15~45at%、Na:0.05~15at%を含有し、残部がCu及び不可避不純物からなる成分組成を有する焼結体であって、
前記焼結体は、前記Naがフッ化ナトリウム、硫化ナトリウム及びセレン化ナトリウムのうち少なくとも1種からなるNa化合物の状態で含有されたNa化合物相が分散している組織を有し、該Na化合物相の平均粒径が、10μm以下であるスパッタリングターゲット。 - 前記焼結体の理論密度比が90%以上、抗折強度が60N/mm2以上、バルク比抵抗が0.1Ω・cm以下であり、
スパッタリングターゲット表面の1cm2面積内に、0.05mm2以上のNa化合物の凝集体が、平均1個以下である請求項1に記載のスパッタリングターゲット。 - 前記焼結体の酸素含有量が、50~2000ppmである請求項1又は2に記載のスパッタリングターゲット。
- 前記焼結体の素地中における金属相の平均粒径が、50μm以下である請求項1乃至3のいずれか一項に記載のスパッタリングターゲット。
- Cu、Ga、Inを含有する粉末とNa化合物粉末との混合粉末を焼結して、Cu、Ga、In、Naを含有した焼結体を作製する焼結工程を有し、
前記Cu、Ga、Inを含有する粉末は、Cu、Ga、Inからなる2元又は3元の合金粉末からなり、或いは、Cu、Ga、Inからなる2元又は3元の合金粉末とCu粉末とからなり、前記混合粉末の平均粒径が1~70μmであるスパッタリングターゲットの製造方法。 - 前記Na化合物粉末とCu、Ga、Inを含有する粉末とは、乾式混合方法によって混合される請求項5に記載のスパッタリングターゲットの製造方法。
- 前記Na化合物粉末を前記混合粉末とする前に70℃以上の温度で乾燥させる工程、又は、前記混合粉末を焼結前に70℃以上の温度で乾燥させる工程を有する請求項5又は6に記載のスパッタリングターゲットの製造方法。
- 前記焼結工程では、前記混合粉末を非酸化性雰囲気又は真空中で焼結する請求項5乃至7のいずれか一項に記載のスパッタリングターゲットの製造方法。
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