Sputtering target and its manufacturing method

Abstract

The aim is to provide a sputtering target with high compositional uniformity. A sputtering target is a sputtering target composed of a noble metal alloy, wherein the noble metal alloy is composed of five or more noble metal elements, and the number of peaks observed in the X-ray diffraction spectrum in the range of diffraction angle 2θ of 38 to 44° is 1.

Description

Sputtering target and method for manufacturing the same The present invention relates to a sputtering target and a method for manufacturing the same. Sputtering, which is one type of physical vapor deposition method, deposits a thin film composed of the material constituting the target on a substrate by bombarding ions such as Ar onto the target. At this time, by using a target containing a plurality of components, a thin film composed of a plurality of components can be formed in a single film-forming process. Therefore, sputtering is used in the manufacture of thin films having various compositions. As a representative method for manufacturing a target for sputtering, a dissolution method and a sintering method can be cited. The dissolution method is a method of dissolving raw materials, solidifying them, and then forming a target by plastic working or machining. The sintering method is a method of sintering powdery raw materials to form a target. In particular, the sintering method can also be applied to high melting point materials, so it is widely used. When manufacturing a target containing a plurality of components by the sintering method, it is only necessary to mix a plurality of raw material powders and then perform sintering (for example, Patent Documents 1 to 3). In addition, in the field of physical vapor deposition, formation of a thin film composed of noble metals is generally carried out. In particular, in recent years, film formation of an alloy thin film containing two or three noble metal elements has been carried out by sputtering (for example, Patent Documents 4 and 5). Here, as noble metal elements, gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), and osmium (Os) can be cited. Although these elements belong to a group of so-called noble metal elements, their actual physical and chemical properties are different for each element. In addition, it is also known that noble metal alloys composed of these noble metal elements greatly change their properties depending on the composition. Therefore, thin films composed of noble metal alloys are expected to have various properties corresponding to the composition. Furthermore, in recent years, research has also been conducted on high-entropy alloys (HEAs) composed of noble metals. A high-entropy alloy, as defined differently, narrowly refers to an alloy containing about five or more elements of equal atomic weight and forming a single-phase solid solution. Since high-entropy alloys exhibit properties quite different from those of ordinary alloys, they have attracted attention. In the past, as high-entropy alloys, base metals such as Cr, Mn, Fe, Co, and Ni have generally been used, but there are also syntheses of high-entropy alloys composed only of noble metal elements (for example, Non-Patent Document 1). [Prior Art Documents] [Patent Documents] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2014-041682 Patent Document 2: Japanese Unexamined Patent Application Publication No. 2014-098206 Patent Document 3: Japanese Unexamined Patent Application Publication No. 2024-010347 Patent Document 4: Japanese Unexamined Patent Application Publication No. 2000-109943 Patent Document 5: Japanese Unexamined Patent Application Publication No. 2006-228688 [Non-Patent Document] Non-Patent Document 1: Journal of the American Chemical Society, February 2022, Vol. 144, No. 8, p.3365-3369 [Problems to be Solved by the Invention] As described above, multicomponent noble metal alloys composed of various noble metal elements have attracted attention. Therefore, it is considered advantageous if a thin film composed of a multicomponent noble metal alloy can be formed by sputtering. However, as described above, the properties of noble metal alloys change greatly depending on the composition, and if there is a variation in the alloy composition of the thin film, the properties will also deviate. Therefore, in order to fully exhibit the properties of noble metal alloys, a noble metal alloy thin film with a highly uniform composition is required. In particular, when manufacturing a thin film composed of the above-mentioned high-entropy alloy, it is considered desirable to minimize segregation of the composition. That is, when there is segregation of the composition in the thin film, the condition of containing each element in equal atomic amounts cannot be satisfied in that part, and there is a risk of not obtaining the original properties of the high-entropy alloy. In addition, when the segregation of the composition is large, there is also a case where a single-phase solid solution cannot be formed. Therefore, significantly higher compositional uniformity is required compared to conventional general alloys. As described above, in order to manufacture a noble metal alloy thin film with an extremely uniform composition by sputtering, it is necessary to极力 exclude factors that cause non-uniformity of the composition. Therefore, even the targets used in sputtering are required to have a high compositional uniformity. However, as a result of investigations by the inventors of the present invention, it has been found that it is difficult to achieve the above-mentioned high compositional uniformity when manufacturing a sputtering target composed of a multicomponent noble metal alloy by conventional methods. An object of the present invention is to solve the above problems and provide a sputtering target having a high compositional uniformity. [Means for Solving the Problems] The inventors of the present invention conducted investigations in order to achieve the above object. As a result, the following findings were obtained. (1) When manufacturing a target by mixing plural powders composed of different noble metal elements and performing sintering, segregation of the composition remains in the target. This is considered to be because the noble metal elements are not sufficiently alloyed. (2) Even when manufacturing a target by a dissolution method using plural powders composed of different noble metal elements as raw materials, segregation of the composition still remains in the target. (3) In contrast, when sintering noble metal alloy powders that have been previously alloyed uniformly in a manner that satisfies specified conditions, even in the case of containing 5 or more noble metal elements, segregation of the composition in the target can be prevented. The target obtained by this method has an extremely uniform composition. The present invention has been completed based on the above见解, and the gist is as follows. 1. A sputtering target composed of a noble metal alloy, wherein the noble metal alloy is composed of 5 or more noble metal elements, and the number of peaks observed in the X-ray diffraction spectrum in the range of diffraction angle 2θ of 38 to 44° is 1. 2. The sputtering target according to 1 above, wherein, for all of the aforementioned noble metal elements, when measured by energy dispersive X-ray spectroscopy, the coefficient of variation CV of the content is 0.2 or less. 3. A method for manufacturing a sputtering target composed of a noble metal alloy, including the following steps: an alloy powder preparation step: preparing alloy powder as a raw material; and a sintering step: sintering the aforementioned alloy powder, wherein the aforementioned alloy powder is a noble metal alloy powder composed of an alloy of 5 or more noble metal elements, and the average particle diameter is 0.1 to 100 μm, and the number of peaks observed in the X-ray diffraction spectrum in the range of diffraction angle 2θ of 38 to 44° is 1. [Effect of the Invention] By the present invention, it is possible to provide a sputtering target composed of 5 or more noble metal alloys with excellent compositional uniformity. Hereinafter, embodiments of the present invention will be specifically described. Note that the present invention is not limited to the embodiments described below. [Sputtering Target] The sputtering target in one embodiment of the present invention is a sputtering target composed of a noble metal alloy. Then, the aforementioned noble metal alloy is an alloy composed of 5 or more noble metal elements and satisfies the following conditions. ・The number of peaks observed in the X-ray diffraction spectrum in the range of diffraction angle 2θ of 38 to 44° is 1 - Noble metal element: The noble metal constituting the aforementioned noble metal alloy is not particularly limited, and any noble metal element can be used. That is, the aforementioned noble metal alloy is an alloy composed of at least five elements selected from the group consisting of Au, Ag, Pt, Pd, Rh, Ir, Ru, and Os. Moreover, among the above noble metal elements, Os has the property of being easily volatilized when heated during the manufacturing process. Therefore, from the perspective of manufacturing ease, the aforementioned noble metal alloy is preferably an alloy composed of at least five elements selected from the group consisting of Au, Ag, Pt, Pd, Rh, Ir, and Ru. The number of noble metal elements constituting the aforementioned alloy is not particularly limited as long as it is 5 or more. That is, all 8 noble metal elements may also be included. The number of the aforementioned noble metal elements may be 6 or 7. Moreover, the ratio (content) of each noble metal element contained in the above noble metal alloy is not particularly limited and can be set to any value. For example, when manufacturing a sputtering target composed of the aforementioned high-entropy alloy, it is only necessary to set the ratio of each noble metal element contained in the aforementioned noble metal alloy to be almost equal. Specifically, the difference (Cmax - Cmin) between the maximum content (Cmax) and the minimum content (Cmin) among the contents (atomic %) of all noble metal elements contained in the aforementioned noble metal alloy is defined as ΔC. This ΔC is preferably 10.0 atomic % or less, more preferably 5.0 atomic % or less, still more preferably 3.0 atomic % or less, and most preferably 2.0 atomic % or less. On the other hand, the lower the aforementioned ΔC, the better, and the lower limit can also be 0 atomic %. - Number of peaks in the XRD spectrum: 1 When the noble metal elements contained in the above noble metal alloy are not sufficiently alloyed, a plurality of peaks from each element will be observed in the X-ray diffraction spectrum in the range of diffraction angle 2θ of 38 - 44°. Therefore, in the present invention, the number of peaks observed in the aforementioned range is set to 1. As long as the number of peaks in the XRD spectrum is 1, it can be said that uniform alloying can be achieved. Here, the reason why the range of diffraction angle 2θ for counting the number of peaks is set at 38 - 44° is that peaks of noble metal elements (Au, Ag, Pt, Pd, Rh, Ir, Ru, and Os) can be observed in this range. ・Coefficient of Variation CV of Content Measured by EDX In the present invention, for all the metal elements constituting the aforementioned precious metal alloy, the content is measured by energy dispersive X-ray spectroscopy (EDX), and the coefficient of variation CV of the content is preferably 0.2 or less, more preferably 0.15 or less. Here, the coefficient of variation CV being 0.2 or less means that the coefficient of variation CV of the content of each precious metal element constituting the aforementioned precious metal alloy is 0.2 or less. By the present invention, a fired body of a precious metal alloy that is extremely uniform with a coefficient of variation CV of 0.2 or less as described above can be obtained. On the other hand, the lower the coefficient of variation CV, the better, so the lower limit is not particularly limited. Typically, the coefficient of variation CV can be 0.05 or more, or can be 0.08 or more. As long as the coefficient of variation CV of the content measured by EDX satisfies the above conditions, it can be said that alloying can be performed more uniformly. ・Crystallite Size The crystallite size of the precious metal alloy constituting the sputtering target of the present invention is not particularly limited. However, the smaller the crystallite size, the higher the smoothness of the thin film obtained by sputtering. In addition, the generation of particles during sputtering can be suppressed. Therefore, the crystallite size of the precious metal alloy constituting the sputtering target is preferably 140 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less. On the other hand, the lower limit of the crystallite size is not limited either. Typically, it can be 1 nm or more, or can be 10 nm or more, or can be 20 nm or more. The above crystallite size can be obtained from the half-value width of the diffraction peak obtained by X-ray diffraction (XRD) measurement. Here, the sputtering target in the present invention means the target material used in sputtering. Therefore, by bonding a backing plate to the above sputtering target as the target material, a sputtering target assembly can be manufactured. In other words, the sputtering target assembly in other embodiments of the present invention includes: the above sputtering target as the target material and a backing plate bonded to the sputtering target. [Manufacturing Method] Next, a manufacturing method of the sputtering target in one embodiment of the present invention will be described. The sputtering target of the present invention can be manufactured by a sintering method. That is, the manufacturing method of the sputtering target in one embodiment of the present invention includes: an alloy powder preparation step and a sintering step. Hereinafter, each step will be specifically described. For matters not particularly mentioned, it can be carried out according to the general manufacturing technology of sputtering targets. [Steps for Preparing Alloy Powder] First, prepare alloy powder as a raw material. The aforementioned alloy powder is a precious metal alloy powder composed of an alloy of 5 or more precious metal elements and must satisfy the following conditions. - The average particle size is 0.1 - 10 μm. - The number of peaks observed in the X-ray diffraction spectrum within the range of diffraction angle 2θ of 38 - 44° is 1. - Average particle size: 0.1 - 100 μm If the average particle size of the above alloy powder is less than 0.1 μm, the apparent density will be significantly reduced. When the apparent density of the powder is low, the shrinkage (volume reduction) during sintering becomes extremely large, so it is not suitable for the manufacture of the target. Therefore, the aforementioned average particle size is set to 0.1 μm or more. On the other hand, when the aforementioned average particle size is greater than 100 μm, the finally obtained target will become brittle. Therefore, the aforementioned average particle size is set to 100 μm or less, preferably 80 μm or less, more preferably 50 μm or less, still more preferably 20 μm or less, and most preferably 10 μm or less. - Number of peaks in the XRD spectrum: 1 In the finally obtained target, in order to set the number of peaks observed in the X-ray diffraction spectrum within the range of diffraction angle 2θ of 38 - 44° to 1, for the alloy powder, the number of peaks observed within the range of diffraction angle 2θ of 38 - 44° must also be 1. - Coefficient of variation CV of the content measured by EDX For all the metal elements constituting the above precious metal alloy powder, the content is measured by energy dispersive X-ray spectroscopy (EDX). The coefficient of variation CV of this content is preferably 0.2 or less, and more preferably 0.15 or less. Here, the coefficient of variation CV being 0.2 or less means that the coefficient of variation CV of the content of each precious metal element constituting the precious metal alloy powder is 0.2 or less. By using the powder with the coefficient of variation CV of 0.2 or less as the alloy powder, the coefficient of variation CV in the finally obtained target can also be set to 0.2 or less. The lower the coefficient of variation CV, the better, so the lower limit is not particularly limited. Typically, the coefficient of variation CV can be 0.05 or more, or can be 0.08 or more. - Crystallite size: 60 nm or more The crystallite size of the alloy powder used as a raw material is not particularly limited. However, when using an alloy powder with a large crystallite size as a raw material, the shrinkage during the target manufacturing process is small and it is easy to form. Therefore, the crystallite size of the alloy powder is preferably set to 60 nm or more, and more preferably 80 nm or more. On the other hand, the upper limit of the aforementioned crystallite size is not particularly limited. Typically, it can be 140 nm or less, or can be 120 nm or less. Also, such precious metal alloy powder with a large crystallite size can be manufactured by the method described later. The above-mentioned microcrystalline size can be obtained from the half-value width of the diffraction peak obtained by X-ray diffraction (XRD) measurement. The method for preparing the above alloy powder is not particularly limited. In one embodiment of the present invention, a noble metal alloy powder manufactured by the following method can be used as the aforementioned alloy powder. Incidentally, the manufacturing methods disclosed herein can be roughly classified into two methods: a method of performing only one firing and a method of performing multiple firings. The former is suitable for manufacturing powders with a relatively small average particle diameter, and the latter is suitable for manufacturing powders with a relatively large average particle diameter. Hereinafter, the respective manufacturing methods will be described. ・Manufacture of powders with a relatively small average particle diameter Fig. 1 shows a flowchart of a method for manufacturing a noble metal alloy powder in one embodiment of the present invention. As shown in Fig. 1, the method for manufacturing a noble metal alloy powder in one embodiment of the present invention includes the following steps (1) to (6). By this manufacturing method, a noble metal alloy powder with an average particle diameter of about 10 μm or less can be manufactured. Hereinafter, each step will be specifically described. (1) Raw material preparation step (2) Slurry preparation step (3) Mixing step (4) First firing step (5) First acetic acid treatment step (6) First washing step This manufacturing method is suitable for manufacturing powders with a relatively small average particle diameter. Specifically, this manufacturing method is suitable for manufacturing powders with an average particle diameter of about 10 μm or less, and is also suitable for manufacturing powders with an average particle diameter of 5 μm or less, and is more suitable for manufacturing powders with an average particle diameter of 3 μm or less. Hereinafter, each step will be specifically described. (1) Raw material preparation step First, in the raw material preparation step, powders (raw material powders) used as raw materials for manufacturing noble metal alloy powders are prepared. The aforementioned raw material powders are prepared separately for each noble metal element constituting the finally manufactured noble metal alloy. For example, when manufacturing a quinary alloy, it is only necessary to prepare five raw material powders. The particle diameter of the aforementioned raw material powder is not particularly limited. From the viewpoint that the finally obtained noble metal alloy powder becomes more uniform, it is preferably to use fine raw material powders. Specifically, it is preferably to set the average particle diameter of each raw material powder used to be 1000 nm or less, more preferably 500 nm or less, and even more preferably 100 nm or less. On the other hand, the lower limit of the aforementioned average particle diameter is not particularly limited either. For example, it can be 1 nm or more, or 5 nm or more, or 10 nm or more. Incidentally, here, the average particle diameter of the aforementioned raw material powder is defined as the average particle diameter d obtained from the specific surface area of the raw material powder using a true sphere model. The aforementioned average particle diameter d (μm) is generally referred to as the BET diameter in some cases. Specifically, it can be obtained from the density ρ (g / cm 3 ) and the BET specific surface area s (m 2 / g) is calculated according to the following formula (1). For the aforementioned raw material powders, metal powders and metal oxide powders can all be used. For example, regarding Pt, Pt powder can be used, or platinum oxide (PtO 2 ) powder can be used. Similarly, for rhodium oxide (RhO 2 , RhO 3 ), palladium oxide (PdO), etc., oxide powders can also be arbitrarily used. These oxide powders will thermally decompose during firing and function as noble metal sources. Basically, whether metal powders or metal oxide powders are used, their function as raw materials remains unchanged, and they can be selected according to the easy availability of the powders, etc. However, regarding Ru, it is better to use ruthenium metal powder as the raw material rather than ruthenium oxide (RuO 2 ) powder. For example, in one embodiment of the present invention, as the aforementioned raw material powder, it is preferably to use at least 5 kinds of powders selected from the group consisting of gold, silver, silver oxide, platinum, platinum oxide, palladium, palladium oxide, rhodium, ruthenium, rhodium oxide, iridium, iridium oxide and osmium. (2) Slurry preparation step Next, while mixing the aforementioned raw material powder, calcium carbonate and water to form a slurry, the pH of the aforementioned slurry is set to 8.0 or more. In the firing step, the aforementioned calcium carbonate will thermally decompose and at least a part of it will become calcium oxide. Because calcium carbonate and calcium oxide have the effect of hindering the grain growth of noble metal alloys. And it helps to refine the finally obtained noble metal alloy powder. The addition amount of the aforementioned calcium carbonate is not particularly limited. From the viewpoint of improving the above-mentioned effect, in terms of weight ratio, relative to all the raw material powders, it is preferably set to 0.1 times or more, more preferably set to 0.2 times or more, and even more preferably set to 0.5 times or more. On the other hand, the upper limit is not particularly limited either, and the effect of excessive addition is also saturated. Therefore, in terms of weight ratio, relative to all the raw material powders, it is preferably set to 10 times or less, more preferably set to 5 times or less, and even more preferably set to 2 times or less. The aforementioned calcium carbonate can be added in any form. Typically, calcium carbonate powder can be used. When using calcium carbonate powder, the average particle diameter of the calcium carbonate powder is not particularly limited, and it is preferably set to 0.2 to 1.0 μm. Here, the average particle diameter of the aforementioned calcium carbonate is defined as the average particle diameter d obtained from the specific surface area of the calcium carbonate using a true sphere model. The aforementioned average particle diameter d (μm) is generally referred to as the BET diameter in some cases. Specifically, it can be calculated from the density ρ (g / cm 3 ) and the BET specific surface area s (m 2 / g) according to the following formula (1). pH: 8.0 or higher In the above slurry preparation step, it is important to set the pH of the slurry to 8.0 or higher. When the pH of the slurry is less than 8.0, the uniformity of the composition in the finally obtained precious metal alloy powder will decrease, and the coefficient of variation CV in EDX measurement will increase. In addition, when the pH of the slurry is less than 8.0, the number of peaks observed in the XRD spectrum within the range of diffraction angle 2θ of 38 to 44° cannot be set to 1. The method for adjusting the pH of the slurry is not particularly limited. For example, when the pH is less than 8.0, an alkali can be added to the slurry. By adding at least one selected from the group consisting of, for example, alkali metal hydroxides, alkaline earth metal hydroxides, and ammonia to the slurry, the pH can be adjusted. Examples of the aforementioned alkali metal hydroxide include sodium hydroxide and potassium hydroxide. In addition, examples of the aforementioned alkaline earth metal hydroxide include calcium hydroxide. Here, the pH of the aforementioned slurry can be measured using a general pH meter. Here, the upper limit of the pH of the above slurry is not particularly limited. However, even when the pH is made higher than 10, the effect of alloy homogenization is saturated. In addition, when the pH is made higher than 10, a large amount of alkali must be added. As a result, a large amount of sodium, potassium, etc. added as the aforementioned alkali will remain as impurities. In addition, when ammonia is used as the aforementioned alkali, a large amount of harmful ammonia gas will be generated during the manufacturing process, which is dangerous. Therefore, the pH of the aforementioned slurry is preferably set to 10 or less. (3) Mixing step In the mixing step, the aforementioned slurry is mixed. Any mixer can be used for the aforementioned mixing, and it is not particularly limited. Examples of the aforementioned mixer include a ball mill, a planetary mill (planetary ball mill), a bead mill, a grinder, etc. From the perspective of mixing more uniformly, it is preferably to use a bead mill or a planetary mill, and among them, it is preferably to use a bead mill. (4) First firing step Next, the slurry mixed in the aforementioned mixing step is fired in a non-oxidizing environment to produce alloy powder. In the present invention, since alloy powder is obtained by firing, the purity can be further improved as compared with the case of using the wet reduction method. The aforementioned firing is not particularly limited and can be carried out with any device. Typically, an electric furnace can be used. In the aforementioned first firing step, in order to prevent oxidation of the components, it is carried out in a non-oxidizing environment. The aforementioned non-oxidizing environment is not particularly limited as long as it is a non-oxidizing environment, and any one can be used. Typically, a nitrogen environment, an argon environment, an environment composed of hydrogen and nitrogen, an environment composed of hydrogen and argon, etc. can be used. From the viewpoint of reliably preventing oxidation of the raw materials, it is preferably to use an environment composed of hydrogen and nitrogen, or an environment composed of hydrogen and argon. The firing temperature (first firing temperature) in the aforementioned first firing step is not particularly limited as long as it is a temperature at which the powder can be fired, and any temperature can be set. The preferred first firing temperature will depend on the melting point T determined by the composition of the noble metal alloy used. M . From the viewpoint of promoting diffusion of the raw material powder and further improving crystallinity, the first firing temperature T 1 is preferably set to T defined by the following formula. L Above. On the other hand, the upper limit of the aforementioned first firing temperature is not particularly limited. If the first firing temperature is too high, necking will occur between the alloy particles, and there will be a case of generating coarse powder. Therefore, the first firing temperature T 1 is preferably set to T defined by the following formula. H Below. Here, T M is set to the weighted average of the melting points of all noble metal elements constituting the noble metal alloy. When calculating the aforementioned weighted average, the content (mass%) of each noble metal element is used. The firing time in the aforementioned first firing step is not particularly limited. From the viewpoint of grain growth of the alloy, it is preferably set to 1 hour or more. On the other hand, from the viewpoint of production efficiency, it is preferably set to 5 hours or less. (5) First acetic acid treatment step Next, the fired product obtained in the aforementioned first firing step is subjected to acetic acid treatment. By applying acetic acid treatment, calcium contained in the fired product can be removed. Also, when using an acid other than acetic acid (for example, hydrochloric acid or nitric acid), not only calcium but also precious metal elements will dissolve, and as a result, the uniformity of the alloy will decrease. In contrast, as long as it is acetic acid, there is no risk of dissolving precious metal elements regardless of the concentration. Therefore, in the present invention, it is important to use acetic acid for the removal of calcium. The method of the aforementioned acetic acid treatment is not particularly limited. Typically, the fired product is stirred in an acetic acid aqueous solution to dissolve calcium contained in the fired product. The aforementioned acetic acid treatment can be carried out any number of times of 1 or more. From the viewpoint of being able to尽可能 reduce the amount of calcium remaining as an impurity, it is preferable to carry out the aforementioned acetic acid treatment 2 or more times, and more preferably 3 or more times. When carrying out acetic acid treatment a plurality of times, as long as a new acetic acid aqueous solution is used each time. During the aforementioned acetic acid treatment, the fired product can be placed in a pre-adjusted acetic acid aqueous solution, or the fired product can be first placed in pure water, and then acetic acid can be added to the aforementioned pure water. Hereinafter, a specific example of a suitable acetic acid treatment method will be described. First, the fired product is placed in pure water and stirred. Thereby, calcium oxide contained in the fired product is changed to calcium hydroxide. Next, acetic acid is further added and stirred to dissolve the aforementioned calcium hydroxide. After that, stirring is stopped and left standing to allow the powder to settle, and the supernatant is removed. The above is one acetic acid treatment. After that, the addition of pure water and acetic acid and stirring, standing, and removing the supernatant are repeated 2 more times. (6) First washing step Next, the fired product (alloy powder) after the above acetic acid treatment is washed with water and dried (washing step). By washing with water, acid or calcium in a state dissolved in acid is removed. During the aforementioned water washing, it is preferable to use pure water. The method of washing with water is not particularly limited. For example, after removing the supernatant in the above acetic acid treatment, pure water is added and stirred, whereby washing can be performed. After stopping stirring, it is left standing to allow the powder to settle, and the supernatant is removed. The aforementioned water washing is preferably repeated 2 or more times, and more preferably 3 or more times. After water washing, it is preferable to perform filtration to separate the water and the powder, and the obtained powder is supplied to the following drying. The aforementioned drying may be carried out by any method as long as it can remove moisture. It may be natural drying, and for efficient moisture removal, heating drying is preferred. When heating drying is carried out, the heating temperature is not particularly limited, preferably set at 50 °C or higher, more preferably set at 80 °C or higher. It may also be 100 °C or higher. The drying time is not particularly limited either and can be set to any time according to the amount of the powder to be dried. From the perspective of achieving sufficient drying, it is preferably set at 1 hour or more, more preferably set at 5 hours or more. It may also be 10 hours or more. On the other hand, the upper limit of the aforementioned heating time is not particularly limited, typically preferably 100 hours or less, more preferably 50 hours or less. Furthermore, after the above drying, it is preferable to further sieve the obtained precious metal alloy powder. Thereby, the particles aggregated during the above washing process can be disintegrated from each other. Through the above procedure, specifically, a precious metal alloy powder with an average particle diameter of 10 μm or less, which is relatively small, can be obtained. ・Manufacture of powder with a relatively large average particle diameter Next, a method for manufacturing a precious metal alloy powder in other embodiments of the present invention will be described. The manufacturing method of this embodiment is a method suitable for manufacturing a relatively large powder with a maximum average particle diameter of 100 μm. Specifically, this manufacturing method is suitable for manufacturing a powder with an average particle diameter exceeding 5 μm, and more suitable for manufacturing a powder exceeding 10 μm. Figure 2 shows a flowchart of the method for manufacturing a precious metal alloy powder in this embodiment. As shown in Figure 2, the method for manufacturing a precious metal alloy powder in an embodiment of the present invention, in addition to steps (1) to (6) in the embodiment shown in Figure 1, further includes the following steps (7) to (10). Additionally, before the second firing step, a particle size adjustment step can be optionally carried out. (7) Second firing step (8) Third firing step (9) Second acetic acid treatment step (10) Second washing step However, among the above steps (7) to (10), only (7) the second firing step is a necessary step, and the remaining steps (8) to (10) are optional steps. In other words, the method for manufacturing a precious metal alloy powder in this embodiment can be roughly divided into two methods: a method of obtaining a precious metal alloy powder through the above steps (1) to (7), and a method of obtaining a precious metal alloy powder through the above steps (1) to (10). The former method involves two firings, namely the first firing step and the second firing step. The latter method involves three firings, namely the first firing step, the second firing step, and the third firing step. Herein, for the sake of explanation, the steps from the raw material preparation step to the first washing step are appropriately referred to as the "front-stage steps", and the steps after the second firing step are referred to as the "back-stage steps". Additionally, between the first washing step and the second firing step, a particle size adjustment step may further be provided. When the particle size adjustment step is implemented, as shown in Figure 3, the particle size adjustment step is included in the back-stage steps. In this embodiment, first, in the front-stage steps, a powder with high crystallinity and excellent compositional uniformity is produced. However, the powder obtained at this stage is composed of relatively small particles (primary particles) with an average particle diameter of about 10 μm or less. Then, the aforementioned primary particles aggregate with each other and form slightly spherical aggregates (secondary particles), and the aforementioned secondary particles have a particle diameter in the range of several tens to hundreds of μm. Therefore, by further subjecting this powder to the back-stage steps, while maintaining high crystallinity and compositional uniformity, the average particle diameter can be made to exceed 10 μm and be 100 μm or less. - Particle size adjustment step In the back-stage steps, before the next second firing step, the particle size of the alloy powder after the first washing step may also be adjusted (particle size adjustment step). By performing the particle size adjustment, it will be possible to more easily obtain a precious metal alloy powder with the desired particle size. The particle diameter of the finally obtained precious metal alloy powder is almost equal to the particle diameter of the powder after the particle size adjustment (i.e., the powder supplied to the next second firing step). Therefore, in the particle size adjustment step, the particle size adjustment may be performed in accordance with the particle diameter of the precious metal alloy powder that is finally desired to be obtained. The method for adjusting the particle size is not particularly limited. Typically, it is sufficient to sieve the alloy powder. The sieve mentioned above is not particularly limited, and any one can be used. Also, both the powder that passes through the sieve (undersize) and the powder that does not pass through the sieve (oversize) can be used. Additionally, the alloy powder may be sieved two or more times to adjust the particle size. For example, first, the coarse particles in the alloy powder may be removed using the first sieve, and then the subsequent sieves may be used to adjust to the desired particle size. When the alloy powder is sieved, in addition to the effect of adjusting the particle size, an effect of spheroidizing the powder particles can also be obtained. This is considered to be because, as an aggregate, the alloy powder is subjected to mechanical forces such as vibration, rotation, and friction on the sieve, resulting in a reduction in the surface irregularities of the particles. The aforementioned spheroidizing effect can be obtained for both the undersize and the oversize, and the effect for the oversize is more significant. Therefore, from the perspective of so-called enhancing the spheroidizing effect, it is preferable to sieve the alloy powder at least once in the particle size adjustment step and use the powder that does not pass through the aforementioned sieve (oversize). ・Second firing step Next, a second firing (second firing step) is performed on the alloy powder. Also, when the particle size adjustment is not performed, the alloy powder after the first washing step may be second-fired; when the particle size adjustment is performed, the alloy powder after the particle size adjustment may be second-fired. The secondary particles before firing are brittle and are likely to disintegrate due to physical contact or impact. Therefore, by performing the second firing, the primary particles forming the secondary particles are necked to each other, and the state of the particles is fixed. Also, calcium carbonate for hindering the necking of secondary particles to each other is used in the subsequent third firing step. However, as described above, the secondary particles before firing are brittle. If they are mixed with calcium carbonate without the second firing, the aggregation of the secondary particles will disintegrate, making it difficult to control the particle size. Therefore, after stabilizing the structure of the secondary particles by performing the second firing and then mixing calcium carbonate, the particle size can be appropriately controlled. The temperature (second firing temperature) during the aforementioned second firing is not particularly limited as long as it is a temperature that causes sintering between primary particles and can be set to any temperature. The preferred second firing temperature depends on the melting point T determined by the composition of the noble metal alloy used. M Therefore, the second firing temperature T 2 is preferably set to T defined by the following formula. L Above, T H Below. Here, T M is set to the weighted average of the melting points of all noble metal elements constituting the noble metal alloy. When calculating the aforementioned weighted average, the content (mass%) of each noble metal element is used. In addition, the time (second firing time) for performing the aforementioned second firing is not particularly limited. It is preferably set to 5 hours or less, more preferably 2 hours or less. In addition, the aforementioned second firing time is preferably set to 30 minutes or more, more preferably 40 minutes or more, and even more preferably 50 minutes or more. The aforementioned second firing step is performed in a non-oxidizing environment to prevent oxidation of the components. The aforementioned non-oxidizing environment is not particularly limited as long as it is a non-oxidizing environment, and any one can be used. Typically, a nitrogen environment, an argon environment, an environment composed of hydrogen and nitrogen, an environment composed of hydrogen and argon, etc. can be used. From the viewpoint of reliably preventing oxidation of the raw materials, an environment composed of hydrogen and nitrogen or an environment composed of hydrogen and argon is preferably used. In one embodiment of the present invention, the alloy powder obtained in the above-described second firing step can be used as a raw material in the manufacture of a sputtering target. In addition, the following treatment can also be further performed on the alloy powder. ・Third firing step The alloy powder after the above-described second firing is further fired in a non-oxidizing environment (third firing step). By firing in two stages in this way, the primary particles constituting the secondary particles can be more firmly bonded to each other, and at the same time, the sphericity of the particles can be further improved. The firing is not particularly limited and can be performed using any device. Typically, an electric furnace can be used. In the above-described third firing step, in order to prevent the secondary particles from bonding to each other to form coarse particles, firing is performed in a state where calcium carbonate is mixed as a sintering inhibitor. The addition amount or form of the calcium carbonate is not particularly limited and can be set to be the same as in the above-described first firing step. The above-described third firing step is performed in a non-oxidizing environment in order to prevent oxidation of the components. The non-oxidizing environment is not particularly limited as long as it is a non-oxidizing environment, and any one can be used. Typically, a nitrogen environment, an argon environment, an environment composed of hydrogen and nitrogen, an environment composed of hydrogen and argon, etc. can be used. From the viewpoint of reliably preventing oxidation of the raw materials, it is preferably to use an environment composed of hydrogen and nitrogen or an environment composed of hydrogen and argon. The firing temperature (third firing temperature) in the above-described third firing step is not particularly limited as long as it is a temperature at which the powder can be fired, and can be set to any temperature. The preferred third firing temperature will depend on the melting point T determined by the composition of the precious metal alloy used. M . Third firing temperature T 3 It is preferably set to T defined by the following formula. L The above. On the other hand, the upper limit of the above-described third firing temperature is not particularly limited. If the third firing temperature is too high, necking will occur between the alloy particles, and there will be a case where coarse powder is generated. Therefore, the third firing temperature T 3 It is preferably set to T defined by the following formula. H The following. Here, T M Is set to the weighted average of the melting points of all the precious metal elements constituting the precious metal alloy. When calculating the above-mentioned weighted average, the content (mass%) of each precious metal element is used. In addition, the firing time in the aforementioned third firing step is not particularly limited, and is preferably set to 1 hour or more. On the other hand, from the viewpoint of production efficiency, it is preferably set to 5 hours or less. ・Second acetic acid treatment step Next, the alloy powder (fired product) after the aforementioned third firing step is treated with acetic acid (second acetic acid treatment step). By applying the acetic acid treatment, calcium contained in the fired product can be removed. Also, when using an acid other than acetic acid (for example, hydrochloric acid or nitric acid), not only calcium but also precious metal elements will dissolve, and as a result, the uniformity of the alloy will decrease. In contrast, as long as it is acetic acid, there is no risk of dissolving precious metal elements regardless of the concentration. Therefore, in the present invention, it is important to use acetic acid for the removal of calcium. The conditions of the second acetic acid treatment step are not particularly limited and can be set the same as those of the aforementioned first acetic acid treatment step. ・Second washing step The alloy powder after the aforementioned first acetic acid treatment is washed with water and dried (second washing step). By performing the water washing, acetic acid or calcium in a state dissolved in the acetic acid can be removed. The conditions of the aforementioned second washing treatment step are not particularly limited and can be set the same as those of the aforementioned first washing step. By the above treatment, a precious metal alloy powder satisfying the above conditions can be obtained. [Sintering step] Next, the alloy powder prepared in the alloy powder preparation step described above is sintered to form a target (sintering step). The method for performing the aforementioned sintering is not particularly limited and can be performed by any method. When performing the aforementioned sintering, it is preferable to pressurize the alloy powder while heating the alloy powder. The aforementioned pressurization can be performed simultaneously with heating, can be performed before heating, or can be both. The method for performing the aforementioned pressurization is not particularly limited. For example, pressurization can be performed with the aforementioned alloy powder placed in a mold. The aforementioned pressurization can be performed in only a uniaxial direction or can be performed isotropically. For example, the aforementioned sintering can be performed by hot press sintering, hot isostatic pressing (HIP), or spark plasma sintering (SPS). The conditions during the aforementioned sintering are not particularly limited and can be adjusted according to the precious metal alloy powder used. For example, when the firing temperature is too low, the bonding between the powders will not be sufficiently performed. Therefore, the sintering temperature T during the aforementioned sintering process S is preferably set to T defined by the following formula L as above. On the other hand, the upper limit of the aforementioned sintering temperature is not particularly limited, and even if the firing temperature is excessively increased, the effect is saturated. Therefore, the aforementioned sintering temperature T S Preferably, T is defined by the following formula H as follows. Here, T M is set to the weighted average of the melting points of all the noble metal elements constituting the noble metal alloy. When calculating the aforementioned weighted average, the content (mass%) of each noble metal element is used. The temperature rise up to the aforementioned sintering temperature can be carried out at any speed. For example, the time (temperature rise time) from the start of the temperature rise to reaching the aforementioned sintering temperature can be 30 to 240 minutes, or can also be 60 to 180 minutes. After reaching the aforementioned sintering temperature, it is preferably maintained at that temperature. The time for maintaining the sintering temperature is not particularly limited, and is preferably set to 30 minutes or more, and more preferably set to 1 hour or more. On the other hand, even if the holding time is excessively long, the effect is saturated. Therefore, the aforementioned holding time is preferably set to 5 hours or less, and more preferably set to 4 hours or less. The aforementioned sintering step is preferably carried out in a non-oxidizing environment in order to prevent oxidation of the components. The aforementioned non-oxidizing environment is not particularly limited, as long as it is a non-oxidizing environment, and any one can be used. Typically, a nitrogen environment, an argon environment, an environment composed of hydrogen and nitrogen, an environment composed of hydrogen and argon, etc. can be used. From the viewpoint of reliably preventing oxidation of the raw materials, an environment composed of hydrogen and nitrogen, or an environment composed of hydrogen and argon is preferably used. The aforementioned firing is carried out using any heating device, and an electric furnace can be used, for example. As the aforementioned electric furnace, an electric furnace equipped with means for controlling the furnace interior environment is preferably used. After the firing step, processing or grinding can also be carried out arbitrarily. That is, in the method for manufacturing a sputtering target in one embodiment of the present invention, after the sintering step, one or both of a processing step and a grinding step can be arbitrarily included. [Examples] Hereinafter, examples and comparative examples of the present invention are given to specifically illustrate the effects of the present invention, but the present invention is not limited thereto. [Example 1] ・ Alloy powder preparation step First, a 5-element noble metal alloy powder composed of Ru, Rh, Pd, Ir, and Pt is manufactured by the following procedure. As raw material powders, Pt, Pd, IrO 2, powders of Ru, Rh. Among the aforementioned powders, as the powders of Pt, Pd, and Ph, Pt black, Pd black, and Rh black are used respectively. Additionally, Ru powder is prepared by reducing RuO 2 powder. Mix the aforementioned raw material powders with calcium carbonate powder and water to form a slurry. At this time, add an alkali for pH adjustment as needed to make the pH of the aforementioned slurry the value shown in Table 1. The addition amount of the aforementioned calcium carbonate is set to 0.8 times the total amount of the aforementioned raw material powders by weight ratio. Additionally, as the aforementioned water, 2 times the amount of pure water is used by weight ratio relative to the total of the aforementioned raw material powders and the aforementioned calcium carbonate. Next, use a planetary ball mill to mix the aforementioned slurry. The mixing conditions are set as rotational speed: 200 rpm, mixing time: 6 hours. Additionally, use a polyamide bottle as the mixing container and polyamide balls with a diameter of 10 mm as the grinding medium. Burn the aforementioned mixed slurry in an N 2 -H 2 environment to produce alloy powder. Specifically, first, dry the aforementioned slurry at 130 °C using a dryer to remove moisture and obtain a mixed powder. Next, put the aforementioned mixed powder into a crucible and conduct firing. Use an environmental temperature-rising electric furnace to conduct the aforementioned firing. The environment during firing is set as 3% H 2 / 97% N 2 gas environment, and set the firing temperature: 1300 °C, firing time: 5 hours. Next, after subjecting the alloy powder obtained from the aforementioned firing step to acetic acid treatment, wash it with pure water and dry it. (Acetic acid treatment) The aforementioned acetic acid treatment is carried out 3 times through the following procedure. First, put the fired product (alloy powder) into pure water and stir. Thereby, the calcium oxide contained in the fired product is changed into calcium hydroxide. Next, further add acetic acid and stir to dissolve the aforementioned calcium hydroxide. After that, stop stirring and let it stand to make the powder settle, and remove the supernatant. The above is one acetic acid treatment. After that, repeat the addition of pure water and acetic acid and stirring, standing, and removing the supernatant 2 more times. Next, the washing with pure water is carried out 3 times through the following procedure. First, after removing the supernatant in the third acetic acid treatment, add pure water and stir. After stopping stirring, let it stand to make the powder settle, and remove the supernatant. Repeat the above washing 3 times. (Drying) After the above washing, filtration is carried out to separate the moisture and the powder, and the obtained powder is dried. The aforesaid drying is carried out at 130°C for 12 hours. The powder after the above drying is sieved to decompose and break up the aggregated powder. As the aforesaid sieve, a stainless-steel test sieve with a screen aperture pitch of 125 μm is used. Also, no particles remain on the sieve and all pass through the sieve. Next, for the obtained precious metal alloy powder, the average particle size, crystallite size, number of peaks in the XRD spectrum, and coefficient of variation CV in EDX are measured by the following procedures. The measurement results are shown in Table 1. (Average particle size) A laser diffraction particle size analyzer MT-3000 manufactured by MicrotracBEL is used to measure the average particle size of the obtained precious metal alloy powder. Specifically, the alloy powder is put into an aqueous solution of sodium hexametaphosphate circulating in the particle size analyzer, and after ultrasonic dispersion for 1 minute, the particle size distribution is measured. The volume-based 50% particle size (D50) obtained is set as the average particle size of the precious metal alloy powder. (Crystallite size) The crystallite size of the obtained precious metal alloy powder is measured by an X-ray diffractometer Ultima IV manufactured by Rigaku. During the aforesaid measurement, the powder to be measured is filled into a glass cell for powder measurement to prepare a sample. The measurement conditions are set as follows: target: Cu, tube voltage: 40 kV, tube current: 40 mA, scanning range: 10~100°, sampling interval: 0.02°, scanning speed: 30° / min. The crystallite size is obtained from the half-value width of the diffraction peak obtained by the aforesaid measurement according to the Scherrer formula. (Number of peaks in the XRD spectrum) In the XRD spectrum obtained from the measurement of the above crystallite size, the number of peaks observed in the range where the diffraction angle 2θ is 38~44° is obtained. Also, when counting the number of peaks, the XRD peaks are peak-separated by Gaussian curve fitting, and those with a peak width of 0.1° or more and a peak intensity of 1 / 100 or more of the maximum peak are regarded as peaks. (Coefficient of Variation CV in EDX) From the measurement results of energy-dispersive X-ray spectroscopy, the coefficient of variation CV of the content of each precious metal element contained in the obtained precious metal alloy powder is calculated. The measurement is carried out using a scanning electron microscope (SEM)-energy-dispersive X-ray analyzer (EDX) JSM-6010LA manufactured by JEOL Ltd. The aforementioned alloy powder is fixed on a carbon tape to prepare a measurement sample. The measurement conditions are set as follows: magnification: 3000 times, acceleration voltage: 20 kV. Under the aforementioned conditions, EDX quantitative measurement is performed on 30 randomly selected points, and the content of each precious metal element is obtained. The coefficient of variation CV is calculated from the obtained average value and standard deviation of the content. As can be seen from the results shown in Table 1, through the above procedure, precious metal alloy powder with high crystallinity and excellent compositional uniformity can be obtained. ・Sintering step Next, the obtained precious metal alloy powder is sintered to fabricate a sputtering target. In this embodiment, the aforementioned sintering is carried out by hot pressing sintering. The specific procedure is as follows. First, 238 g of the above-mentioned precious metal alloy powder is put into a sintering mold made of graphite. The internal shape of the aforementioned sintering mold is 80 mm × 80 mm. Next, the powder in the aforementioned sintering mold is hot pressed under the conditions of a nitrogen environment, a temperature of 1100 °C, a pressure of 15.5 MPa, and a holding time of 30 minutes. After cooling, the sputtering target is taken out from the sintering mold. Using a commercially available automatic cutting machine, the obtained sputtering target can be cut without problems. The cut end face has a metallic luster. In addition, the aforementioned sputtering target can be ground by a conventional method, and the ground surface has a metallic luster. Thus, the sputtering target of the present invention can be processed or ground by a conventional method, and in this regard, it can also be said to be suitable as a target material. Next, for the obtained sputtering target, the crystallite size, the number of peaks in the XRD spectrum, and the coefficient of variation CV in EDX are measured by the following procedure. The measurement results are shown in Table 2. (Crystallite size) The crystallite size of the obtained target is measured by an X-ray diffractometer Ultima IV manufactured by Rigaku. During the aforementioned measurement, the target to be measured is made into a sample. The measurement conditions are set as follows: target: Cu, tube voltage: 40 kV, tube current: 40 mA, scanning range: 10~100°, sampling interval: 0.02°, scanning speed: 30° / min. The crystallite size is obtained from the half-value width of the diffraction peak obtained by the aforementioned measurement according to the Scherrer formula. (Number of Peaks in XRD Spectrum) In the XRD spectrum obtained from the measurement of the crystallite size as described above, the number of peaks observed within the diffraction angle 2θ range of 38 to 44° was determined. Also, when counting the number of peaks, the XRD peaks were separated by Gaussian curve fitting, and peaks with a peak width of 0.1° or more and a peak intensity of 1 / 100 or more of the maximum peak were regarded as peaks. (Coefficient of Variation CV in EDX) From the measurement results of energy-dispersive X-ray spectroscopy, the coefficient of variation CV of the content of each precious metal element contained in the obtained target was calculated. The measurement was performed using a scanning electron microscope (SEM)-energy-dispersive X-ray analyzer (EDX) JSM-6010LA manufactured by JEOL Ltd. The aforementioned target was fixed on a carbon tape to prepare a measurement sample. The measurement conditions were set as follows: magnification: 3000 times, acceleration voltage: 20 kV. Under the aforementioned conditions, EDX quantitative measurements were performed on 30 randomly selected points to obtain the content of each precious metal element. The coefficient of variation CV was calculated from the obtained average value and standard deviation of the content. As can be seen from the results shown in Table 2, through the above procedure, a sputtering target with excellent compositional uniformity and high crystallinity can be obtained. Using the above sputtering target, magnetron sputtering was actually performed to fabricate a precious metal alloy powder film. For the obtained film, the coefficient of variation CV in EDX was measured in the same manner as the evaluation of the target. As a result, the coefficients of variation of Ru, Rh, Pd, Ir, and Pt were 0.135, 0.107, 0.137, 0.149, and 0.112, respectively. From this result, it can be known that as long as a sputtering target that satisfies the conditions of the present invention is used, a precious metal alloy film with excellent compositional uniformity can be obtained. Also, the film obtained by sputtering is generally amorphous. Therefore, the XRD spectrum of the above film cannot be measured. [Comparative Example 1] Next, for comparison, a sputtering target was fabricated by sintering a mixed powder. As the aforementioned mixed powder, a mixed powder obtained by mixing Ru powder, Rh powder, Pd powder, Ir powder, and Pt powder in such a way that each precious metal element has an equal atomic weight was used. The powder of each element used was a chemically reduced powder, and the average particle size of each powder was about several hundred μm to 1 μm. 10 g of the aforementioned mixed powder was put into a water-cooled copper hearth, completely melted by arc melting, and then cooled to room temperature and taken out from the aforementioned water-cooled copper hearth. The aforementioned arc melting was carried out in an Ar environment. Other conditions were the same as those in Example 1 above. For the obtained sputtering target, the number of peaks in the XRD spectrum and the coefficient of variation CV in EDX were measured in the same manner as in Example 1 above. The measurement results are shown in Table 2 together. Also, in the case of the target of Comparative Example 1, a plurality of peaks were observed in the XRD spectrum used when calculating the crystallite size. Therefore, the crystallite size could not be determined unambiguously, so the crystallite size is not shown in Table 2. As can be seen from the results shown in Table 2, in the case of Comparative Example 1 using the mixed powder, the number of peaks in the XRD spectrum was 4, so alloying could not be performed uniformly. In addition, the value of the coefficient of variation CV in EDX was also significantly larger than that in Example 1. Therefore, it can also be known that the compositional uniformity is poor. In the case of the arc melting method, even though each powder was temporarily melted and mixed, when using the mixed powder, a target with a uniform composition could not be obtained. [Comparative Example 2] The same mixed powder as in Comparative Example 1 above was sintered to produce a sputtering target. However, in this Comparative Example 2, in order to mix the powders of each element more uniformly, the target was produced by the following procedure. First, specifically, first, the aforementioned mixed powder, resin, and solvent were mixed to form a paste. The contents in the aforementioned paste were set as follows: mixed powder: 80% by mass, resin: 1.8% by mass, solvent: 18.2% by mass. Specifically, ethyl cellulose was used as the aforementioned resin, and 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (texanol) was used as the aforementioned solvent. Next, the obtained paste was further kneaded using a three-roll mill for a sufficient time to sufficiently disperse each component. Next, by the screen printing method, the above paste was coated on an alumina substrate in the form of a film. Next, it was dried at 120 °C to volatilize the solvent contained in the coated paste to form a film. The obtained film was peeled off from the substrate and pulverized in a crucible to obtain a noble metal powder-resin mixed powder in a state where the noble metal powder and the resin were sufficiently uniformly mixed. Next, pressure was applied to the aforementioned noble metal powder-resin mixed powder to produce a compact (pressed powder). After that, the aforementioned compact was further sintered at 1300 °C to obtain a sintered body (target). Also, this condition was set to be the same as in Comparative Example 1 above. For the obtained sputtering target, the number of peaks in the XRD spectrum and the coefficient of variation CV in EDX were measured in the same manner as in Example 1 above. The measurement results are shown in Table 2 together. Also, in the case of the target of Comparative Example 2, a plurality of peaks were observed in the XRD spectrum used when calculating the crystallite size. Therefore, the crystallite size could not be determined unambiguously, so the crystallite size is not shown in Table 2. As can be seen from the results shown in Table 2, in Comparative Example 2 using the mixed powder, even when the resin and the solvent were used and kneaded sufficiently uniformly, and sintered at a sufficiently high temperature of 1300 °C, the compositional uniformity was still worse than that of Example 1. [Comparative Example 3] Next, for comparison, arc melting was used instead of hot press sintering, and the sputtering target was fabricated under the same conditions as in Example 1 above. The conditions for arc melting were set to be the same as in Comparative Example 1 above. For the obtained sputtering target, the number of peaks in the XRD spectrum and the coefficient of variation CV in EDX were measured in the same manner as in Example 1 above. The measurement results are shown together in Table 2. Also, for the target of Comparative Example 3, a plurality of peaks were observed in the XRD spectrum used when calculating the crystallite size. Therefore, the crystallite size could not be determined unambiguously, and thus the crystallite size is not shown in Table 2. As can be seen from the results shown in Table 2, in Comparative Example 1 using arc melting, even when the same noble metal alloy powder 1 as in Example 1 was used as the raw material, the number of peaks in the XRD spectrum was still 2, and alloying could not be achieved uniformly. In addition, the value of the coefficient of variation CV in EDX was also significantly larger than that in Example 1. Therefore, it can also be known that the compositional uniformity is poor. The reason why the composition became non-uniform in this way is considered to be segregation during the temporary melting and subsequent solidification of the alloy. As can be seen from the above results, in order to obtain a sputtering target with excellent compositional uniformity that satisfies the conditions of the present invention, it is necessary to sinter the raw material powder that has been alloyed uniformly in advance to fabricate the target. [Figure 1] shows a flowchart of a method for manufacturing a raw material (noble metal alloy powder) in an embodiment of the present invention. [Figure 2] shows a flowchart of a method for manufacturing a raw material (noble metal alloy powder) in another embodiment of the present invention.

Claims

1. A sputtering target composed of a noble metal alloy, wherein the noble metal alloy is composed of five or more noble metal elements, and the difference between the maximum content Cmax and the minimum content Cmin of all the noble metal elements contained in the noble metal alloy is defined as ΔC, wherein ΔC is less than 10.0 atomic%, and the number of peaks observed in the X-ray diffraction spectrum within the diffraction angle 2θ of 38 to 44° is 1.

2. As in request item 1, the sputtering target, wherein, For all of the aforementioned precious metal elements, the coefficient of variation (CV) of the content was less than 0.2 when measured by energy-dispersive X-ray spectrophotometry.

3. A method for manufacturing a sputtering target, comprising the following steps: an alloy powder preparation step: preparing alloy powder as raw material; and a sintering step: sintering the aforementioned alloy powder, wherein the aforementioned alloy powder is a noble metal alloy powder composed of an alloy of five or more noble metal elements, and the difference between the maximum content Cmax and the minimum content Cmin of all noble metal elements contained in the aforementioned noble metal alloy is defined as ΔC, wherein ΔC is less than 10.0 atomic%, and the average particle size is 0.1~100 μm, and the number of peaks observed in the X-ray diffraction spectrum within the diffraction angle 2θ range of 38~44° is 1.

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