WO2022102765A1 - 白金系スパッタリングターゲット及びその製造方法 - Google Patents
白金系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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- WO2022102765A1 WO2022102765A1 PCT/JP2021/041818 JP2021041818W WO2022102765A1 WO 2022102765 A1 WO2022102765 A1 WO 2022102765A1 JP 2021041818 W JP2021041818 W JP 2021041818W WO 2022102765 A1 WO2022102765 A1 WO 2022102765A1
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- platinum
- sputtering target
- average particle
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- ingot
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- 238000005477 sputtering target Methods 0.000 title claims abstract description 60
- 238000004519 manufacturing process Methods 0.000 title claims description 34
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims abstract description 229
- 229910052697 platinum Inorganic materials 0.000 claims abstract description 114
- 239000002245 particle Substances 0.000 claims abstract description 86
- 239000000463 material Substances 0.000 claims abstract description 46
- 229910001260 Pt alloy Inorganic materials 0.000 claims abstract description 34
- 238000010438 heat treatment Methods 0.000 claims description 81
- 239000013078 crystal Substances 0.000 claims description 79
- 238000000034 method Methods 0.000 claims description 78
- 238000005096 rolling process Methods 0.000 claims description 76
- 230000008569 process Effects 0.000 claims description 57
- 238000005242 forging Methods 0.000 claims description 56
- 238000001953 recrystallisation Methods 0.000 claims description 37
- 238000000265 homogenisation Methods 0.000 claims description 29
- 238000005266 casting Methods 0.000 claims description 16
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 9
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 9
- 239000000654 additive Substances 0.000 claims description 8
- 230000000996 additive effect Effects 0.000 claims description 8
- 229910052741 iridium Inorganic materials 0.000 claims description 6
- 229910052759 nickel Inorganic materials 0.000 claims description 5
- 229910052763 palladium Inorganic materials 0.000 claims description 5
- 239000010948 rhodium Substances 0.000 claims description 5
- 229910052721 tungsten Inorganic materials 0.000 claims description 5
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 claims description 4
- 229910052703 rhodium Inorganic materials 0.000 claims description 4
- 229910052707 ruthenium Inorganic materials 0.000 claims description 4
- 229910045601 alloy Inorganic materials 0.000 claims description 3
- 239000000956 alloy Substances 0.000 claims description 3
- 229910017052 cobalt Inorganic materials 0.000 claims description 3
- 239000010941 cobalt Substances 0.000 claims description 3
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 3
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 3
- 239000010937 tungsten Substances 0.000 claims description 3
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 claims description 2
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 claims description 2
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 claims description 2
- 239000000203 mixture Substances 0.000 abstract description 5
- 235000013339 cereals Nutrition 0.000 description 70
- 239000010408 film Substances 0.000 description 26
- 238000004544 sputter deposition Methods 0.000 description 24
- 239000010409 thin film Substances 0.000 description 24
- 230000000052 comparative effect Effects 0.000 description 21
- 238000000717 platinum sputter deposition Methods 0.000 description 21
- 238000012545 processing Methods 0.000 description 21
- 230000005291 magnetic effect Effects 0.000 description 11
- 239000000047 product Substances 0.000 description 9
- 238000001887 electron backscatter diffraction Methods 0.000 description 8
- 238000005259 measurement Methods 0.000 description 8
- 238000002844 melting Methods 0.000 description 8
- 230000008018 melting Effects 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 7
- 238000004458 analytical method Methods 0.000 description 5
- 238000001816 cooling Methods 0.000 description 5
- 230000007547 defect Effects 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 230000008859 change Effects 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 238000011156 evaluation Methods 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 239000011572 manganese Substances 0.000 description 4
- 239000000155 melt Substances 0.000 description 4
- 238000003860 storage Methods 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- 230000033228 biological regulation Effects 0.000 description 3
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- 238000005520 cutting process Methods 0.000 description 3
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- 239000011261 inert gas Substances 0.000 description 3
- 229910052748 manganese Inorganic materials 0.000 description 3
- 238000007670 refining Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
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- 239000004065 semiconductor Substances 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 240000007594 Oryza sativa Species 0.000 description 1
- 235000007164 Oryza sativa Nutrition 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 229910052793 cadmium Inorganic materials 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
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- 230000001747 exhibiting effect Effects 0.000 description 1
- 239000003302 ferromagnetic material Substances 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- 238000005304 joining Methods 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 239000000696 magnetic material Substances 0.000 description 1
- 238000001755 magnetron sputter deposition Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 238000003801 milling Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910052762 osmium Inorganic materials 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 150000003057 platinum Chemical class 0.000 description 1
- 238000012805 post-processing Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000004663 powder metallurgy Methods 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 235000009566 rice Nutrition 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000010944 silver (metal) Substances 0.000 description 1
- 238000009751 slip forming Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000004901 spalling Methods 0.000 description 1
- 238000000992 sputter etching Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
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
- C23C14/3407—Cathode assembly for sputtering apparatus, e.g. Target
-
- 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
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/02—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling heavy work, e.g. ingots, slabs, blooms, or billets, in which the cross-sectional form is unimportant ; Rolling combined with forging or pressing
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C5/00—Alloys based on noble metals
- C22C5/04—Alloys based on a platinum group metal
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/14—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of noble metals or alloys based thereon
-
- 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
-
- 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
Definitions
- the present invention relates to a platinum-based sputtering target made of platinum or a platinum alloy. More specifically, the present invention relates to a platinum-based sputtering target that suppresses changes in the film thickness of a thin film formed during use over time and enables the formation of a thin film having stable in-plane uniformity for a longer period of time than before. ..
- Platinum is a conductive material with good chemical stability, and its application as a thin film electrode for semiconductor devices such as FeRAM and DRAM is being studied. Further, although platinum is a non-magnetic material, it is known that vertical magnetic anisotropy is exhibited by alloying with a ferromagnetic material or forming multiple layers at the nanometer level. Taking advantage of this phenomenon, a thin film made of platinum or a platinum alloy is also expected as a constituent material of a magnetic recording surface of a magnetic recording medium. When forming a thin film electrode, a magnetic recording surface, or the like, a sputtering method using a platinum-based sputtering target made of platinum or a platinum alloy (hereinafter, may be simply referred to as a target) is applied.
- a target platinum-based sputtering target made of platinum or a platinum alloy
- Patent Document 1 discloses a platinum sputtering target having an average crystal grain size of 50 ⁇ m or less and a tolerance of crystal grain size in the in-plane direction of the target surface and the thickness direction of the target of 20% or less.
- the ingot after melt casting is subjected to primary forging and secondary forging in a predetermined temperature range, then cross-rolled in a predetermined temperature range, and then heat-treated.
- strain is introduced by forging and cross-rolling, and then heat treatment is performed to reduce the grain size by recrystallization.
- the above-mentioned in-plane uniformity of the film thickness of the sparling target is required to be continuous.
- the sparling target is used repeatedly and supplies a thin film to a large number of substrates.
- in-plane uniformity can be achieved at the initial stage of use, it is impossible to manufacture a stable product if the in-plane uniformity is lost as the usage time is integrated.
- the importance of this in-plane uniformity over time has become higher than in recent years, and the standards have become stricter.
- the magnetic tunnel junction element (MTJ element) that is the storage element is composed of a large number of thin films including a platinum thin film.
- MTJ element magnetic tunnel junction element
- each thin film has a film thickness as designed.
- a thin film having a multi-layer structure is formed on one substrate and divided into individual elements. If a target that cannot maintain in-plane uniformity over time is used, the film thickness of the manufactured storage element will vary. Variations in film thickness lead to variations in electrical characteristics such as sheet resistance, that is, variations in the area resistance product of MTJ elements, so that non-standard elements are manufactured. Such non-standard elements not only lead to a decrease in product yield, but also affect the reliability of the entire product. Therefore, stricter in-plane uniformity is required than before.
- the platinum-based sputtering target can form a thin film having good in-plane uniformity at the initial stage of use, but the film thickness varies during use and meets the required criteria. It has been confirmed that there is no such thing.
- the present invention has been made based on the above background, and can maintain in-plane uniformity over time for a platinum-based sputtering target made of platinum or a platinum alloy, and is as strict as described above. It is an object of the present invention to provide a platinum-based sputtering target capable of clearing various standards and a method for producing the same.
- the sputtering method is a thin film forming method in which sputtered particles such as ionized argon particles are accelerated to collide with a target, and constituent atoms of the target sputtered by momentum exchange at that time are deposited on a substrate.
- sputtered particles such as ionized argon particles
- constituent atoms of the target sputtered by momentum exchange at that time are deposited on a substrate.
- the spatterin target takes the above-mentioned uneven wear form, if the state of the crystal grains is uniform in the thickness direction, it is considered that the influence on the in-plane uniformity is small.
- the uniformity of the state of crystal grains in the thickness direction is not sufficient in the conventional sputtered phosphorus target. In particular, it is considered that there is a factor that causes variation in in-plane uniformity near the center of the spatterin target in the thickness direction.
- Patent Document 1 described above also defines a tolerance in the thickness direction regarding the crystal grain size of the sparring target.
- the fact that the in-plane uniformity may decrease with time even in such a spatterin target indicates that the provisions in the prior art cannot cope with it.
- the present inventors have studied a manufacturing method different from the conventional one in order to find a sputtering target having stable sputtering characteristics even when used for a long time. As a result, we have found a sparring target that is in a strict state with respect to the crystal grain size in the thickness direction, and came up with the present invention.
- n 5 to 20
- N-2 When a region consisting of categories is set as a determination region, the average particle size of each category is measured and the average particle size of the entire determination region is measured for the determination region, the entire determination region is measured. It is a platinum-based sputtering target characterized in that the average particle size is 150 ⁇ m or less and the fluctuation coefficient calculated from the average particle size of each category of the determination region is 15% or less.
- the platinum-based sputtering target according to the present invention defines the material structure in the cross section in the thickness direction. Specifically, a predetermined region in the cross section in the thickness direction is set as a determination region for determining in-plane uniformity, and the average particle size of the entire region is defined. In addition to this, it is characterized in that the cross section is divided into a plurality of sections, the average particle size of each section is measured, and the coefficient of variation obtained from them is strictly limited.
- each configuration of the present invention will be described.
- the platinum-based sputtering target according to the present invention is composed of platinum (pure platinum) or a platinum alloy.
- platinum alloy any of Pd (palladium), Rh (lodium), Ir (iridium), Ru (lutenium), Co (cobalt), Mn (manganese), Ni (nickel), and W (tungsten) can be added as an additive element.
- Platinum alloys containing iridium are applied.
- an alloy containing 0.1 atomic% or more and 30 atomic% or less of the additive element is applied.
- the thickness direction is a direction substantially orthogonal to the spatter surface.
- the sputtered surface is a surface on which inert gas ions mainly collide and emit atoms constituting the target.
- the cross section is an arbitrary cut surface in the thickness direction.
- RD rolling cross section
- TD rolling vertical cross section
- the parallel to the rolling direction and the perpendicular to the rolling direction include a tolerance of ⁇ 20 °.
- the above rolling direction is the rolling direction in the final rolling process.
- the platinum target according to the present invention may employ cross rolling in the rolling process performed after forging.
- Cross-rolling is a method of rolling in the width direction (vertical direction) in addition to rolling in the length direction (longitudinal direction) of the material. Therefore, for example, if the rolling direction of the final rolling is the length direction, the cross section parallel to the length direction is defined as the rolling cross section (RD), and the rolling vertical cross section (TD) is perpendicular to the length direction. Will be. Further, in the present invention, it is required that both the above-mentioned overall average particle size and the standard of the coefficient of variation in each determination region are satisfied in both the rolled cross section and the rolled vertical cross section.
- (A) Configuration of platinum-based sputtering target according to the present invention (i) Judgment area
- (N-2) divisions are used as a judgment region, and the average particle size value and the coefficient of variation in this region are defined. Then, the in-plane uniformity of the target over time is determined based on those values. If the number of divisions is 5 or more and 20 or less, the individual divisions become too broad and the statistical reliability becomes poor if the number of divisions is less than 5.
- the coefficient of variation of the average particle size of each category of the determination region satisfies the conditions of the present invention, it cannot be said that the variation of the particle size is suppressed. Therefore, it may not be a target that can maintain in-plane uniformity over time. Further, even if the number of divisions exceeds 20, the area of each division becomes too small and the number of crystal grains contained in each division becomes small, resulting in low statistical reliability. Therefore, the number of divisions n is set to 5 or more and 20 or less.
- the overall average particle size in the cross section of the target of the present invention is 150 ⁇ m or less (preferably 40 ⁇ m or less), so it is preferable to set the number of divisions from the average particle size and the plate thickness of the target. ..
- the division at both ends is excluded from the determination region because the division at the end on the surface side (sputtering surface side) of the target is a region used at the initial stage of the sputtering process, and is in-plane over time. This is because it is an unnecessary part when considering uniformity.
- the division of the end portion on the back surface side was excluded from the determination area because it is not used up to this area. Further, since the sputtering target is usually used by joining a backing plate to the back surface, it is not necessary to consider the division near the back surface.
- the average particle size in the determination region is the average particle size of the entire target, and the value is 150 ⁇ m or less.
- the present inventors have also acknowledged the usefulness of refining crystal grains for exhibiting stable sputtering characteristics in sparling targets.
- the sparling target of the present invention is composed of fine crystal grains having an average particle size of 150 ⁇ m or less.
- the average particle size is preferably 40 ⁇ m or less.
- the target may be cut at an arbitrary cross section and appropriately etched to observe the structure, the grain size of all the crystal grains in the observation region may be measured, and the average value thereof may be obtained. Further, a plurality of crystal grains in the observation region may be arbitrarily extracted, and their particle sizes may be measured to obtain an average value. In these particle size measurements, the average value of the major axis and the minor axis can be adopted as the method for calculating the particle size. Further, a line segment method is also known as a method for measuring the average particle size.
- the line segment method In the line segment method, multiple line segments are arbitrarily drawn for the tissue observation result (photograph). Then, the average particle size in the line segment is calculated from the number of points (intersections) where the line segment and the grain boundary intersect and the length of the line, and this is performed for each line segment, and the overall average value is the crystal particle size. And.
- the line segment method is a method that can obtain the average particle size relatively easily.
- the average particle size can also be measured by cutting the cross section of the target and then using an appropriate analytical means and image processing.
- a suitable analytical means is electron backscatter diffraction (EBSD).
- EBSD is an analytical method that can quickly obtain information on the orientation analysis of crystal grains. Then, by processing with appropriate image analysis software, it is possible to measure the particle size value and calculate the average particle size from the identification of the grain boundaries.
- the average particle size in the surface direction of the surface (sputtering surface) of the platinum-based sputtering target is not particularly specified.
- a treatment is performed so that the grain refinement by recrystallization extends to the entire material. Therefore, a material structure in which crystal grains are refined can be seen on the target surface as well. Therefore, the average particle size on the target surface is also preferably 150 ⁇ m or less, preferably 40 ⁇ m or less.
- the average particle size of the crystal grains contained in these divisions is not taken into consideration.
- the average particle size in the entire thickness of the target including the divisions at both ends is 150 ⁇ m or less, preferably 40 ⁇ m or less.
- the coefficient of variation (CV) of the average particle size of each category included in the determination region is obtained based on the average particle size of each category in the determination region.
- the coefficient of variation is a coefficient obtained by measuring the average particle size for each division in the determination area, calculating the standard deviation thereof, and dividing the standard deviation by the average particle size of the entire determination area.
- the platinum-based sputtering target cross section is divided into n equal parts, and a judgment region consisting of (n-2) categories excluding both ends is set, and in each category, a judgment region is set. Observe and measure the average particle size. Then, the standard deviation, which is the square root of the variance (unbiased dispersion) of the average particle size of each category, is calculated as follows. The coefficient of variation of the average particle size of each category is calculated by dividing this standard deviation by the overall average particle size.
- N number of categories, s: standard deviation of average particle size of each category, X a : average particle size of the entire judgment region, X i : average particle size of each category)
- N number of divisions
- CV coefficient of variation of each division
- s standard deviation of average particle size of each division
- Xa average particle size of the entire judgment region
- the platinum-based sputtering target according to the present invention needs to have a coefficient of variation of 15% or less calculated from the average particle size of (n-2) categories included in the determination region of the cross section in the thickness direction. If the coefficient of variation exceeds 15%, it contains crystal grains that are unfavorable for ensuring in-plane uniformity over time, and the problem of the present invention cannot be solved.
- the standard of the coefficient of variation is preferably 10% or less, and more preferably 7% or less.
- the platinum-based sputtering target according to the present invention has strict rules regarding the average grain size of crystal grains in the cross section in the thickness direction, thereby ensuring in-plane uniformity over time in the process of using the target. do.
- the crystal grain size is miniaturized and the coefficient of variation of the average grain size is defined, and the shape of the crystal grains is defined. It is also preferable to specify.
- the ratio of crystal grains having an aspect ratio of 3 or more based on the number of particles is 20% or less, and the aspect ratio is 5 or more. It is preferable that the ratio of the above is 9% or less based on the number of particles.
- the aspect ratio in the present invention is calculated as a ratio (maximum diameter / minimum diameter) between the maximum diameter and the minimum diameter for each crystal grain. Therefore, according to the standard of the present invention, the aspect ratio is calculated to be 1 or more, and the larger the value, the flatter the crystal grain.
- the shape of the crystal grains in the cross-sectional structure is also uniform.
- the ratio of flat crystal grains having an aspect ratio of 3 or more and 5 or more is low. Therefore, the above conditions are preferable.
- the aspect ratio of the crystal grains is more preferably 18% or less, still more preferably 7% or less, with respect to the ratio of the crystal grains having an aspect ratio of 3 or more based on the number of particles.
- the ratio of crystal grains having an aspect ratio of 5 or more based on the number of particles is more preferably 3% or less, further preferably 1% or less.
- the cross-sectional structure may be observed and each dimension of the crystal grains may be measured from the observation photographs / images in the same manner as in the case of the average particle size measurement.
- Image processing and software can also be used.
- the ratio based on the number of particles is a ratio based on the number of particles of the crystal grains whose aspect ratio is to be measured within the range of the observation area.
- a plurality of crystal grains may be arbitrarily extracted from the crystal grains in the observation region, or all the crystal grains in the observation region may be the measurement target.
- the platinum-based sputtering target according to the present invention is preferably made of high-purity platinum or a platinum alloy in order to ensure the quality of the electrode film / magnetic film.
- the platinum sputtering target made of pure platinum preferably has a platinum purity of 99.99% by mass or more.
- the platinum alloy sputtering target made of the platinum alloy described above has a total purity of 99.9% by mass or more of platinum and any of the additive elements Pd, Rh, Ir, Ru, Co, Mn, Ni and W. Some are preferred.
- the upper limit of the purity of platinum or a platinum alloy is preferably 100% by mass, but in consideration of unavoidable impurities, it is practically 99.999% by mass or less.
- the unavoidable impurities of the platinum sputtering target made of pure platinum are Au, Ag, Pd, Rh, Ir, Ru, Os, Al, As, B, Bi, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn,
- gas components such as O (oxygen), N (nitrogen), C (carbon), and S (sulfur) can be mentioned.
- the platinum alloy sputtering target made of a platinum alloy the gas component and the elements of the element group other than the additive element of the platinum alloy can be unavoidable impurities.
- the total content of these unavoidable impurities is preferably 100 ppm or less.
- the platinum-based sputtering target according to the present invention is a material manufactured by a melt casting method.
- the platinum-based sputtering target one composed of a sintered body of platinum powder or platinum alloy powder produced by a so-called powder metallurgy method is also known, but the present invention is distinguished from this sintered target. ..
- the platinum-based sputtering target according to the present invention has a relative density of 99.5% or more based on the theoretical density of platinum or a platinum alloy having the same composition.
- the shape and dimensions of the platinum-based sputtering target according to the present invention are not particularly limited.
- the shape is generally a circular or rectangular plate shape, but is not particularly limited thereto.
- Regarding the dimensions there are no restrictions on the plane dimensions (diameter, long side, short side) and thickness.
- the platinum-based sputtering target according to the present invention is basically manufactured by the same manufacturing process as the conventional target.
- an ingot is manufactured by melt casting, forged to produce an ingot, and further rolled to produce a rolled material close to the product size, and then the above-mentioned. It is known to heat the rolled material.
- the final heat treatment step is a step for causing recrystallization, and is a step for adjusting the material structure by refining the crystal grains by using lattice defects such as dislocations introduced by the processing history up to that point as a driving force. ..
- the manufacturing process of the platinum-based sputtering target according to the present invention also includes the above-mentioned melt casting process, forging process, rolling process, and recrystallization heat treatment process.
- the present invention in the material structure of the cross section in the thickness direction, it is necessary to adjust the distribution of the average grain size more strictly than before, and preferably the shape (aspect ratio) of the crystal grains is also optimized. ..
- the present inventors perform forging processing so that the cast structure at the center of the ingot does not remain. It was decided to heat the ingot before rolling to homogenize the material structure of the ingot as a whole and then perform the heat treatment.
- the method according to the present invention including this homogenization heat treatment includes a forging step of forging an ingot made of platinum or a platinum alloy after melt casting at least once to produce an ingot, and rolling the ingot at least once.
- the ingot is 850 ° C. or higher and 950 ° C., including a rolling process for producing a rolled material and a recrystallizing heat treatment step for heat-treating the rolled material, after the forging process and before the rolling process.
- This is a method for manufacturing a platinum-based sputtering target, which is subjected to homogenization heat treatment by heating at the following temperature, and further, the heating temperature of the rolled material in the recrystallization heat treatment step is 600 ° C. or higher and 700 ° C. or lower.
- each step of this manufacturing method will be described.
- the melting casting step is a step of melting platinum metal and additive element metal as raw materials, casting them into a mold, and cooling them to obtain an ingot made of platinum or a platinum alloy.
- the raw material metal use a high-purity metal according to the product purity for manufacturing purposes.
- the raw metal is melted by heating in a high-frequency melting furnace, an electric melting furnace, or a plasma melting furnace, preferably in an inert gas atmosphere or a vacuum atmosphere.
- the mold a square or round plate shape is used in consideration of the product shape. Cooling after casting the molten metal may be performed at a moderate cooling rate of furnace cooling or air cooling.
- the ingot made of platinum or a platinum alloy after melt casting may be cut and cut for the purpose of dimensional adjustment and removal of inhomogeneous portions that may exist at the ends.
- the shape of the ingot produced here is not limited, and may be a rectangular parallelepiped shape, a cubic shape, or a cylindrical shape.
- the forging process is a process of compressing and striking an ingot made of platinum or a platinum alloy to form an ingot having a shape and dimensions that can be easily processed in the rolling process described later.
- the forging process also has the important purpose of destroying the cast structure of the ingot.
- the processing method in the conventional technique is basically applied.
- As the processing temperature in the forging process a temperature that enables deformation for the forming process and forging of the ingot may be applied.
- the processing temperature in the forging process can be set to 800 ° C. to 1300 ° C. Further, the forging process in this step is performed at least once, and can be performed intermittently a plurality of times as needed.
- the destruction of the cast structure of the ingot is emphasized as the purpose of the forging process.
- emphasis is placed on the destruction of the cast structure in the center of the ingot.
- it is preferable to forge until the dimension in the direction indicating the maximum dimension of the ingot is 50% or less.
- the maximum side of the ingot is 50% or less.
- the forging process When the forging process is completed by one forging process, it is determined by the dimensions at the end stage of the process. When the forging process is performed a plurality of times, it is determined by the dimension at the end stage of the final forging process.
- the lower limit of the maximum side of the ingot by this forging is preferably 30% or more. In forging, the cast structure should be destroyed as much as possible. However, since it is not preferable that the temperature of the ingot becomes too low due to the forging process, the lower limit of the maximum side of the ingot may be 40% or more. If the forging process is performed until the maximum side of the ingot is 40% or more and 50% or less, the cast structure, which is the purpose of the forging process, can be destroyed. Further, the ingot made of platinum or a platinum alloy obtained by the forging process described above may be cut or face-cut, if necessary.
- the present invention is characterized in that the ingot after the forging process is heat-treated before the subsequent rolling process.
- heat treatment at a high temperature which will be described later, is not performed before rolling. This is because platinum is relatively soft against other precious metals and has good workability, so it is not necessary to raise the temperature so much during rolling.
- the temperature control in the conventional manufacturing process the cast structure remains in the ingot, and even if rolling and recrystallization heat treatment are performed in this state, sufficient recrystallization does not occur in the thickness direction, and the average crystal grain size is average. The distribution of is not exactly adjustable.
- the ingot before the rolling process is heat-treated at a high temperature so that the effect of the recrystallization heat treatment extends to the entire target, and once the ingot is homogenized without a cast structure or strain.
- recrystallization based on lattice defects such as dislocations introduced in the subsequent rolling process can be homogeneously generated, and the distribution of the average particle size in the thickness direction can be made suitable.
- the homogenization heat treatment heats the ingot at a temperature of 850 ° C or higher and 900 ° C or lower. Below 850 ° C, it becomes difficult to obtain the above-mentioned homogenized material. Further, when the temperature exceeds 950 ° C., the strain in the material is sufficiently released, but the crystal grains become coarse, which is considered to affect the final product characteristics.
- the heating time of the homogenization heat treatment is preferably 60 minutes or more and 120 minutes or less. The treatment time is controlled by the treatment temperature, the plate thickness of the ingot, and the like, but heating for at least 60 minutes is required to complete the homogenization. On the other hand, even if the heat treatment is performed for an excessively long time, there is no difference in the homogenization effect, so the time is set to 120 minutes or less in consideration of the production efficiency.
- the rolling process is a processing process for processing an ingot made of platinum or a platinum alloy after forging into a platinum plate material having the dimensions and shape required to obtain the final dimensions of the product. .. In addition to this, it is a step for introducing lattice defects such as transitions that serve as a driving force for recrystallization for grain refinement into the homogenized ingot. Therefore, although the rolling process is also an important process, the same conditions as those performed by the conventional platinum-based sputtering target can be applied to the rolling process itself.
- the rolling process is usually cold rolling, and the temperature of the material to be rolled is 20 ° C to 200 ° C. The rolling process is performed at least once and can be repeated as needed.
- unidirectional rolling may be used, but it is preferable to apply cross rolling.
- various types of rolling are performed according to the respective purposes such as draw-out rolling, intermediate rolling, finish rolling, and flattening rolling.
- appropriate rolling directions and processing rates are set for each rolling process.
- the processing rate of the rolling process for the ingot after the forging process is preferably 90% or more and 95% or less.
- the plate thickness after the final rolling process is preferably 10% or less and 5% or more with respect to the thickness of the ingot after the forging process. The reason why the processing rate of 90% or more is set in this way is to promote the grain refinement by the subsequent recrystallization by introducing a large number of processing strains.
- (V) Recrystallization heat treatment step By heat-treating the rolled material into which lattice defects have been introduced by the above rolling process, grain refinement due to recrystallization occurs.
- the rolling process is performed after the above-mentioned homogeneous heat treatment is performed, and lattice defects are uniformly introduced in the entire material. Then, the recrystallization heat treatment produces uniform crystal refinement in the thickness direction, and crystal grains having little variation in average particle size are produced. Further, the aspect ratio of the crystal grains in the thickness direction is also suitable.
- the heat treatment conditions for the recrystallization heat treatment step are a heating temperature of 600 ° C or higher and 700 ° C or lower. Sufficient recrystallization is unlikely to occur below 600 ° C. On the other hand, if the heat treatment is performed at a temperature exceeding 700 ° C., the crystal grains may be coarsened, and the average crystal grain size as a whole may be out of the range of the present invention. In addition, the coefficient of variation of the average crystal grain size in the determination region may increase.
- the heating time for the recrystallization heat treatment is preferably 60 minutes or more and 120 minutes or less.
- sufficient heating is required in order to cause recrystallization up to the vicinity of the center of the plate thickness to optimize the average crystal grain size and the aspect ratio. Therefore, the lower limit of the processing time is set to 60 minutes.
- the heat treatment is performed for more than 120 minutes, the effect is small and there is a possibility that partial coarsening may occur.
- the platinum-based sputtering target according to the present invention has in-plane uniformity over time by providing a stricter regulation than before regarding the average grain size of crystal grains in the cross section in the thickness direction. According to the present invention, in-plane uniformity at the initial stage of use can be maintained, and a platinum thin film or a platinum alloy thin film having a constant film thickness can be stably produced over a long period of time.
- FIG. 1 The photograph which shows the crystal structure of the platinum ingot before the homogenization heat treatment (after the forging process) and after the homogenization heat treatment in the manufacturing process of this embodiment.
- FIG. 1 The photograph which shows the crystal structure of the platinum ingot before the homogenization heat treatment (after the forging process) and after the homogenization heat treatment in the manufacturing process of this embodiment.
- a platinum sputtering target made of pure platinum is manufactured as a platinum-based sputtering target.
- platinum sputtering targets were manufactured under various conditions, the material structure of the cross section in the thickness direction was observed, and the average particle size and coefficient of variation of the crystal grains were measured. Further, a platinum thin film was produced by a sputtering device, and the in-plane uniformity of the thin film was evaluated.
- Example 1 [Melting casting process / forging process] Platinum with a purity of 99.99% is melted in a high-frequency plasma melting furnace and cast into a copper mold to produce platinum ingots (dimensions: 30 mm (thickness) x 75 mm (width) x 205 mm (length)). Was cut to obtain a platinum ingot having a thickness of 30 mm (thickness) ⁇ 75 mm (width) ⁇ 173 mm (length)). This platinum ingot was heated to 1300 ° C. for 30 minutes and then forged continuously a plurality of times so as to have a size of 60 mm (thickness) ⁇ 78 mm (width) ⁇ 82 mm (length).
- the longest side (173 mm) of the platinum ingot is processed to 47% (82 mm). Then, the surface was face-cut and molded into 55 mm (thickness) ⁇ 78 mm (width) ⁇ 82 mm (length) to manufacture a platinum ingot.
- FIG. 1 shows a photograph of the material structure of the platinum ingot before and after the homogenization heat treatment. This material structure observation was obtained by observing with a metallurgical microscope after etching the side surface of each target. As can be seen from FIG. 1, the material structure of the platinum ingot after the homogenization heat treatment changes significantly from the material structure after the forging process. It can be confirmed that the crystal structure of the platinum ingot is homogenized by the homogenization heat treatment.
- the platinum ingot was rolled in the width and length directions and rolled to a size that could cut out the target as a product.
- it was rolled to a width of 16.4 mm (thickness) ⁇ 270 mm (width) ⁇ 85 mm (length).
- finish rolling to 3.1 mm (thickness) x 273 mm (width) x 427 mm (length). bottom.
- the material to be processed was brought to 20 ° C. and then the process was performed.
- the processing rate in the rolling process is about 94%.
- the platinum plate material after the rolling process was flattened with a roller and then cut to obtain a rolled material for the recrystallization heat treatment process.
- Example 2 In this example, a platinum ingot was manufactured by enlarging the mold in the melt casting process to produce a platinum ingot larger than that of Example 1 and forging until the size became the same as that of Example 1. That is, in this Example 2, a platinum sputtering target was manufactured by performing a more sufficient forging process than in Example 1. In the forging process of this example, the longest side of the platinum ingot was processed to 30%. The homogenization heat treatment, rolling heat treatment, and recrystallization heat treatment after the forging process were the same as in Example 1.
- Example 3 In this embodiment, two stages of forging are intermittently performed in the forging process.
- the same platinum ingot as in Example 1 was produced, the platinum ingot was heated to 1300 ° C. for 30 minutes, forged to a size of 37 mm (thickness) ⁇ 78 mm (width) ⁇ 82 mm (length), and then processing was temporarily interrupted. bottom. Then, the ingot was heated again to 1300 ° C. for 30 minutes and forged until it became 60 mm (thickness) ⁇ 78 mm (width) ⁇ 82 mm (length). Subsequent homogenization heat treatment, rolling process, and recrystallization heat treatment were the same as in Example 1.
- Comparative Example 1 As a comparative example with respect to the above-mentioned Example, a target was manufactured by performing a rolling process and a recrystallization heat treatment without performing a homogenization heat treatment after the forging process. This is the same as in Example 1 except that the homogenization heat treatment was not performed.
- Comparative Example 2 Compared to Example 1, the heating temperature in the recrystallization heat treatment step was set to a high temperature. A platinum ingot was produced in the same manner as in Example 1, homogenized heat treatment was performed, and after rolling, the platinum ingot was heated at 900 ° C. for 60 minutes and recrystallized heat treatment to produce a platinum sputtering target.
- Comparative Example 3 In this comparative example, a sample of a platinum sputtering target was produced without performing a recrystallization heat treatment step. A platinum sputtering target was manufactured in the same manner as in Example 1 without heat-treating the platinum plate material that had undergone the melt casting step, the forging process, the homogenization heat treatment step, and the rolling process.
- Table 1 summarizes the manufacturing conditions of the platinum sputtering targets of Examples 1 to 3 and Comparative Examples 1 to 3 above.
- the average crystal grain size in the thickness direction cross section was measured while observing the material structure in the thickness direction cross section.
- FIG. 2 when the platinum plate material after cutting was recrystallized and heat-treated to cut out a platinum sputtering target, two samples were cut out from the vicinity of the target and evaluated. For each sample, two (No. 1 and No. 3) were cut out from a portion near the center in the length direction of the target and a portion near the side surface.
- a rolled cross section (RD) and a rolled vertical cross section (TD) were set, and each surface was cut and embedded with resin so that each surface could be measured (sample dimensions: 5 mm ⁇ 10 mm).
- the resin-filled sample was subjected to manual polishing and vibration polishing, and then pretreated by ion milling.
- the rolled cross section (RD) and the rolled vertical cross section (TD) were analyzed on the EBSD.
- the particle size and the like of the crystal grains were measured based on the profile of each surface obtained by EBSD.
- the angle difference from the adjacent crystal grains was 6 ° or more as a result of EBSD, it was determined to be a grain boundary, and all the crystal grains were discriminated in the observation region.
- the grain size and aspect ratio of each crystal grain in the observation region were measured by elliptical fitting the discriminated crystal grains.
- Image processing software (HKL CHANNEL 5 manufactured by Oxford Instruments) was used for the above analysis.
- each cross section was divided into 10 equal parts, and 8 divisions excluding both ends were set as the judgment area. .. Then, the average particle size of each category and the average particle size of the entire determination region were measured. Furthermore, the standard deviation of the average particle size of each category was calculated to calculate the coefficient of variation in the determination region.
- the crystal grain size on the surface is also measured. Furthermore, the hardness of each platinum target in the cross section in the thickness direction is also measured. The hardness was measured with a Vickers hardness tester (weight: 0.1 kgf), and the average value of a plurality of measurement points was obtained.
- Table 2 shows the measurement results of the overall average particle size, coefficient of variation, aspect ratio 3 and the ratio of crystal grains of 5 or more in the determination region of the cross section in the thickness direction of each of the above samples. Further, as an example of the material structure of the cross section in the thickness direction of the target analyzed by EBSD, the sample No. 1 of Example 1 was used. The material structure of the rolled cross section of No. 1 is shown in FIG.
- the overall average particle size in the determination region of the cross section in the thickness direction is 150 ⁇ m or less.
- the coefficient of variation of the average particle size in the determination region is 15% or less.
- Comparative Example 3 In the target manufactured without performing the homogenization heat treatment of Comparative Example 1, No. In sample 3, the coefficient of variation of the average particle size exceeded 15%. Since the difference between Comparative Example 1 and Example 1 in the manufacturing process is the presence or absence of the homogenization heat treatment, it was confirmed that the homogenization heat treatment improves the uniformity of the crystal grains in the thickness direction. Further, when the temperature of the recrystallization heat treatment of Comparative Example 2 is raised to a high temperature, the average particle size is coarsened as a whole in the thickness direction. The coefficient of variation was also out of specification in either the rolled cross section or the rolled vertical cross section. Regarding Comparative Example 3, the grain boundaries could not be recognized during the analysis / analysis by EBSD. It is considered that Comparative Example 3 is composed of a rolled structure because the final recrystallization heat treatment was not performed.
- the proportion of crystal grains having an aspect ratio of 3 or more is set to 20% or less (more preferably 18% or less) and the aspect ratio is 5 or more, as in each embodiment of the present application. It can be said that the in-plane uniformity of the film thickness can be ensured by setting the ratio of crystal grains to 3% or less (more preferably 1% or less).
- Example 1 to 3 and Comparative Examples 2 and 3 by the platinum sputtering targets were evaluated.
- each target and substrate (12-inch silicon wafer) were set in a magnetron type sputtering device, the inside of the device was evacuated, and then the inert gas was charged.
- Sputtering was performed under two conditions (condition 1 (small sputtering power) and condition 2 (large sputtering power) according to the magnitude of the sputtering rate.
- the wear depth of the target due to film formation is estimated while monitoring the sputter rate.
- Film formation was performed at each stage of the target at the initial stage of use (wear depth of about 0.2 mm), the middle stage of use (wear depth of about 0.8 mm), and the late stage of use (wear depth of about 1.5 mm). Then, about 30 to 50 points on the wafer were evenly sampled with respect to the platinum thin film of the wafer formed at each stage, and the film thickness and the sheet resistance value of each point were measured.
- the film thickness was measured by a fluorescent X-ray analysis method.
- the sheet resistance was measured by the 4-terminal measuring method. The mean value and standard deviation were calculated from these values, and the value obtained by dividing the standard deviation by the mean value was used as an index of variation.
- the in-plane uniformity of the film thickness was inferior from the initial stage of use and did not change even in the middle stage of use.
- the target of Comparative Example 3 manufactured without undergoing the recrystallization heat treatment step after the rolling process is not in a state where the grain boundaries can be recognized and has the worst in-plane uniformity. rice field.
- the target of Comparative Example 2 in which the heating temperature in the recrystallization heat treatment step was set to a high temperature had a large average grain size of crystal grains and could not clear the standard of in-plane uniformity.
- Comparative Example 1 manufactured without undergoing the homogenization heat treatment has better in-plane uniformity than Comparative Examples 2 and 3, but is significantly reduced in the later stage of use, so that the in-plane uniformity is significantly reduced. It was not possible to suppress the change over time.
- any element of palladium, rhodium, iridium, ruthenium, cobalt, manganese, nickel, and tungsten may be added to platinum in a composition range of 1 atomic% or more and 30 atomic% or less.
- a sputtering target made of added platinum alloy is also useful. Since the concentration of added elements of these platinum alloys is within the composition range of the solid solution limit, alloying is relatively easy. Further, even if any of these additive elements is added in the composition range of 1 atomic% or more and 30 atomic% or less, the platinum alloy has similar processability to the platinum target, so the production method according to the present invention is applied. It is possible.
- the manufacturing method according to the present invention imparts good in-plane uniformity and effectiveness in suppressing changes in in-plane uniformity over time to the sputtering target.
- the platinum alloy sputtering target by this manufacturing method is also effective in suppressing the in-plane uniformity and its change with time.
- a platinum thin film or a platinum alloy thin film having stable and good in-plane uniformity can be produced in the film forming process. This is due to the strict regulation on the average grain size of crystal grains in the cross section in the thickness direction.
- the present invention is useful for thin film electrodes of semiconductor devices and recording films of magnetic recording media, which require high quality platinum thin films or platinum alloy thin films.
Abstract
Description
(i)判定領域
本発明では、ターゲットの断面を厚さ方向に沿ってn等分(n=5~20)に区分し、両端を除いた(n-2)個の区分を判定領域とし、この領域における平均粒径値と変動係数を規定する。そして、それらの値に基づきターゲットの経時的な面内均一性を判定する。区分数に関して5以上20以下とするのは、5未満の区分数では個々の区分が広範となり過ぎて統計的な信頼性に乏しくなる。この場合、判定領域の各区分の平均粒径の変動係数が本発明の条件を具備していたとしても、粒径のばらつきが抑制されている状態とは言い難くなる。そのため、経時的な面内均一性を維持し得るターゲットとならない可能性がある。また、20を超えた数で区分しても、各区分の面積が小さくなり過ぎ各区分に含まれる結晶粒の数が少なくなり、統計的な信頼性が低くなる。そこで、区分数nを5以上20以下とする。
本発明に係る白金系スパッタリングターゲットは、前記判定領域における平均粒径をターゲットの全体の平均粒径とし、その値を150μm以下とする。スパッリングターゲットについて、安定したスパッタリング特性を発揮させるための結晶粒の微細化の有用性は、本発明者等も認めるところである。本発明のスパッリングターゲットは、平均粒径150μm以下の微細な結晶粒で構成される。この平均粒径は、40μm以下であることが好ましい。
本発明では、判定領域内の各区分における平均粒径に基づき、判定領域に含まれる各区分の平均粒径の変動係数(CV)を求める。変動係数は、判定領域内の区分毎に平均粒径を測定し、それらの標準偏差を算出し、当該標準偏差を判定領域の全体の平均粒径で除した係数である。
本発明に係る白金系スパッタリングターゲットは、電極膜・磁性膜としての品質を確保するため、高純度の白金又は白金合金からなるものが好ましい。具体的には、純白金からなる白金スパッタリングターゲットは、白金純度が、99.99質量%以上であるものが好ましい。また、上記した白金合金からなる白金合金スパッタリングターゲットは、白金と添加元素であるPd、Rh、Ir、Ru、Co、Mn、Ni、Wのいずれかとの合計の純度が99.9質量%以上であるものが好ましい。白金又は白金合金の純度の上限については、100質量%が好ましいが、不可避不純物を考慮すると、99.999質量%以下とするのが現実的である。
次に、本発明に係る白金系スパッタリングターゲットの製造方法について説明する。本発明に係る白金系スパッタリングターゲットは、基本的には従来のターゲットと同様の製造工程にて製造される。従来の白金系スパッタリングターゲットの製造工程としては、熔解鋳造で鋳塊を製造し、これを鍛造加工してインゴットを製造し、更に、圧延加工して製品寸法に近い圧延材を製造した後、前記圧延材を熱処理することが知られている。最後の熱処理工程は、再結晶を生じさせるための工程であり、それまでの加工履歴によって導入された転位等の格子欠陥を駆動力として結晶粒を微細化させて材料組織を調整する工程である。
熔解鋳造工程は、原料となる白金金属、添加元素金属を熔解して鋳型に鋳込み冷却して白金又は白金合金からなる鋳塊を得る工程である。この工程に関しては従来技術と特段の差異はない。原料金属は、製造目的の製品純度に合わせて高純度のものを使用する。原料金属の熔解は、高周波熔解炉、電気熔解炉、プラズマ溶解炉で加熱し、好ましくは不活性ガス雰囲気中、真空雰囲気中で行なう。鋳型は、製品形状を考慮して角形状又は丸板形状の鋳型が使用される。熔解金属を鋳込んだ後の冷却は、炉冷又は空冷の緩やかな冷却速度で良い。尚、熔解鋳造後の白金又は白金合金からなる鋳塊については、寸法調整や端部に存在するおそれのある不均質部分の除去を目的として切断、切削を行っても良い。また、ここで製造される鋳塊の形状に制限はなく、直方体形状、立方体形状、円柱形状いずれでも良い。
鍛造加工は、白金又は白金合金からなる鋳塊を圧縮・打撃することで、後述の圧延加工工程での加工を施しやすい形状・寸法のインゴットに加工する工程である。そして、鍛造加工工程には、鋳塊の鋳造組織を破壊するという重要な目的もある。鍛造加工工程は、基本的には従来技術における加工方法が適用される。鍛造加工における加工温度は、鋳塊の成形加工・鍛錬のための変形を可能となるような温度を適用すればよい。本発明においては、後述の均質化熱処理工程があることから、鍛造加工工程で材料組織を変容させるための温度条件は不要である。鍛造加工工程における加工温度は、800℃~1300℃と設定できる。また、この工程における鍛造加工は少なくとも1回行われ、必要に応じて間欠的に複数回行うことができる。
上述のとおり、本発明においては、鍛造加工工程後のインゴットについて、その後の圧延加工工程の前に熱処理を行うことを特徴とする。従来の白金系スパッタリングターゲットの製造工程では、圧延加工の前に後述する高温での熱処理を行うことはない。これは、白金が他の貴金属等に対して比較的軟らかく加工性が良いことから、圧延加工に際してはさほど高温とする必要がないからである。但し、従来の製造工程における温度管理では、インゴットに鋳造組織が残存したままであり、この状態で圧延と再結晶熱処理を行っても厚さ方向において十分な再結晶は生じず、平均結晶粒径の分布を厳密に調整することはできない。
圧延加工工程は、鍛造後の白金又は白金合金からなるインゴットを、製品となる最終寸法を得るのに必要となる寸法・形状の白金板材に加工するための加工工程である。そして、これに加えて、均質化されたインゴットに対して、結晶粒微細化のための再結晶の駆動力となる転移等の格子欠陥を導入するための工程である。よって圧延加工工程も重要な工程ではあるが、圧延加工工程自体は従来の白金系スパッタリングターゲットで行われる加工と同様の条件が適用できる。圧延加工工程は冷間圧延によるものが通常であり、被圧延材の温度は、20℃~200℃で加工される。圧延加工工程は少なくとも1回行われ、必要に応じて繰り返し行うことができる。圧延方向については、一方向圧延によっても良いが、クロス圧延を適用することが好ましい。圧延加工工程では、巾出し圧延、中間圧延、仕上げ圧延、平坦化圧延等のそれぞれの目的に応じた各種の圧延がなされる。これらの圧延加工工程では、それぞれの圧延加工にとって適切な圧延方向・加工率が設定される。そして、鍛造加工工程後のインゴットに対する圧延加工工程の加工率は、90%以上95%以下とするのが好ましい。例えば、最後の圧延加工後の板厚が、鍛造加工工程後のインゴットの厚さに対して10%以下5%以上とするのが好ましい。このように90%以上の加工率を設定するのは、加工歪を多数導入することで、その後の再結晶による結晶粒微細化を促進するためである。
上記圧延加工工程により格子欠陥が導入された圧延材を熱処理することで再結晶による結晶粒の微細化が生じる。特に本発明では、上述した均質加熱処理を行った後に圧延加工工程が行われており、材料全体で均一に格子欠陥が導入されている。そして、再結晶熱処理により厚さ方向で均質な結晶微細化が生じ、平均粒径のばらつきの少ない結晶粒が生成される。また、厚さ方向における結晶粒のアスペクト比も好適となる。
以上の再結晶熱処理工程により本発明で規定する材料組織を有する白金系スパッタリングターゲットを製造することができる。但し、後加工工程として平坦化加工、面削加工、切断等を行っても良い。
[熔解鋳造工程・鍛造加工工程]
純度99.99%の白金を高周波プラズマ溶解炉で熔解し、銅製の鋳型に鋳込み白金鋳塊(寸法:30mm(厚さ)×75mm(巾)×205mm(長さ))を製造し、端部を切断して30mm(厚さ)×75mm(巾)×173mm(長さ))の白金鋳塊を得た。この白金鋳塊を1300℃に30分間加熱した後、60mm(厚さ)×78mm(巾)×82mm(長さ)となるように複数回連続して鍛造した。以上の鍛造加工工程により、白金鋳塊の最も長い辺(173mm)を47%(82mm)となるまで加工したこととなる。その後、表面を面削加工して、55mm(厚さ)×78mm(巾)×82mm(長さ)に成型し白金インゴットを製造した。
そして、鍛造加工工程後の白金インゴットを均質加熱処理した。均質加熱処理工程は、大気中にて電気炉で白金インゴットを900℃で60分間加熱した。加熱後、炉冷して圧延加工工程に供するための白金インゴットとした。ここで、均質化熱処理による材料組織の変化を説明するため、均質化熱処理前後の白金インゴットの材料組織写真を図1に示す。この材料組織観察は、各ターゲットの側面をエッチングした後に金属顕微鏡で観察して得たものである。図1からわかるように、均質化熱処理後の白金インゴットの材料組織は、鍛造加工工程後の材料組織から大きく変化する。均質化熱処理によって、白金インゴットの結晶組織は、均質化されることが確認できる。
圧延加工工程では、白金インゴットを幅及び長さ方向で圧延し、製品となるターゲットを切り出せる寸法にまで圧延加工した。まず、巾出し圧延にて16.4mm(厚さ)×270mm(巾)×85mm(長さ)とした。その後、中間圧延にて6.77mm(厚さ)×273mm(巾)×197mm(長さ)とした後、仕上げ圧延で3.1mm(厚さ)×273mm(巾)×427mm(長さ)とした。各圧延加工では、被加工材を20℃にした後に加工を行った。尚、この圧延加工工程により、厚さ55mmの白金インゴットから厚さ3.1mmの圧延材が製造されたので、圧延加工工程における加工率は約94%となる。圧延加工工程後の白金板材は、ローラーで平坦化した後、切断して再結晶熱処理工程のための圧延材とした。
再結晶熱処理工程では、上記圧延加工工程後に切断された白金の圧延材を650℃で60分間加熱した。その後、再度ローラーで平坦化した。その後、白金スパッタリングターゲットを製造した。
この実施例では、熔解鋳造工程の鋳型を大きくして実施例1よりも大きい白金鋳塊を製造しつつ、実施例1と同じ寸法になるまで鍛造加工して白金インゴットを製造した。つまり、この実施例2では、実施例1よりも更に十分な鍛造加工を行って白金スパッタリングターゲットを製造した。この実施例の鍛造加工工程では、白金鋳塊の最も長い辺が30%になるまで加工した。そして、鍛造加工工程後の均質化熱処理、圧延加工処理、再結晶熱処理は実施例1と同様とした。
この実施例では、鍛造加工工程において間欠的に2段階の鍛造を行っている。実施例1と同じ白金鋳塊を製造し、白金鋳塊を1300℃に30分間加熱し、37mm(厚さ)×78mm(巾)×82mm(長さ)となるまで鍛造した後に一旦加工を中断した。その後、鋳塊を再度1300℃に30分間加熱し、60mm(厚さ)×78mm(巾)×82mm(長さ)となるまで鍛造した。その後の均質化熱処理、圧延加工処理、再結晶熱処理は実施例1と同様とした。
HKL CHANNEL5)を使用した。
Claims (7)
- 白金又は白金合金からなる白金系スパッタリングターゲットにおいて、
厚さ方向に沿った断面を厚さ方向に沿ってn等分(n=5~20)に区分し、両端を除いた(n-2)区分からなる領域を判定領域として設定し、前記判定領域について、区分毎の平均粒径を測定すると共に判定領域の全体の平均粒径を測定したとき、
前記判定領域の全体の平均粒径が150μm以下であり、
前記判定領域の各区分の平均粒径より算出される変動係数が15%以下であることを特徴とする白金系スパッタリングターゲット。 - 判定領域の全体の平均粒径が40μm以下である請求項1記載の白金系スパッタリングターゲット。
- 判定領域において、アスペクト比が3以上の結晶粒の粒子数基準での割合が20%以下であり、且つ、アスペクト比が5以上の結晶粒の粒子数基準での割合が9%以下である請求項1又は請求項2記載の白金系スパッタリングターゲット。
- 純度99.99質量%以上の白金からなる請求項1~請求項3のいずれかに記載の白金系スパッタリングターゲット。
- 添加元素として、パラジウム、ロジウム、イリジウム、ルテニウム、コバルト、マンガン、ニッケル、タングステンのいずれかを1原子%以上30原子%以下含み、
白金と前記添加元素との合計の純度が99.9質量%以上の合金からなる請求項1~請求項3のいずれかに記載の白金系スパッタリングターゲット。 - 請求項1~請求項5のいずれかに記載の白金系スパッタリングターゲットの製造方法であって、
熔解鋳造後の白金又は白金合金からなる鋳塊を少なくとも1回鍛造加工してインゴットを製造する鍛造加工工程と、前記インゴットを少なくとも1回圧延加工して圧延材を製造する圧延加工工程と、前記圧延材を熱処理する再結晶熱処理工程と、を含み、
前記鍛造加工工程の後で且つ前記圧延加工工程前に、前記インゴットを850℃以上950℃以下の温度で加熱する均質化熱処理を行い、
更に、前記再結晶熱処理工程における前記圧延材の加熱温度を600℃以上700℃以下とする白金系スパッタリングターゲットの製造方法。 - 均質化熱処理工程におけるインゴットの加熱時間を60分以上120分以下とする請求項6記載の白金系スパッタリングターゲットの製造方法。
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JP2014043614A (ja) * | 2012-08-27 | 2014-03-13 | Mitsubishi Materials Corp | Ni又はNi合金スパッタリングターゲット及びその製造方法 |
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WO2017209281A1 (ja) * | 2016-06-02 | 2017-12-07 | 田中貴金属工業株式会社 | 金スパッタリングターゲット |
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