Sputtering target and method for producing the same

Abstract

The purpose of the present invention is to provide a sputtering target having high composition uniformity. This sputtering target is formed from a noble metal alloy. The noble metal alloy is formed from 5 or more species of noble metal elements. In an X-ray diffraction spectrum, the number of peaks observed within a range of the diffraction angle 2θ between 38° and 44° is 1.

Description

Technical Field

[0001] The present invention relates to a sputtering target and a method for manufacturing the same.

Background Art

[0002] In sputtering, which is a type of physical vapor deposition method, a thin film made of the material constituting the target can be deposited on a substrate by colliding ions such as Ar with the target. At that time, by using a target containing a plurality of components, a thin film composed of a plurality of components can be formed by a single film formation process. Therefore, sputtering is used for manufacturing thin films having various compositions.

[0003] Typical methods for manufacturing a target used in sputtering include a melting method and a sintering method. The melting method is a method in which a raw material is melted, then solidified, and then formed into a target by plastic working or machining. The sintering method is a method in which a powdery raw material is sintered to form a target. In particular, the sintering method is widely used because it is applicable to high melting point materials. When manufacturing a target containing a plurality of components by the sintering method, a plurality of raw material powders may be mixed and then sintered (for example, Patent Documents 1 to 3).

[0004] In the field of physical vapor deposition, it has also been generally practiced to form a thin film made of a noble metal. In particular, in recent years, an alloy thin film containing two or three noble metal elements has also been formed by sputtering (for example, Patent Documents 4 and 5).

[0005] Here, examples of noble metal elements include gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), and osmium (Os). Although these elements belong to a single group called noble metal elements, their actual physical and chemical properties differ from element to element. Additionally, it is known that the properties of noble metal alloys composed of these noble metal elements vary significantly depending on their composition. Therefore, thin films made of noble metal alloys are expected to have various properties depending on their composition.

[0006] Furthermore, in recent years, research has also been conducted on high-entropy alloys (HEAs) composed of noble metals. By definition, a high-entropy alloy, in the narrow sense, refers to an alloy that contains approximately equal atomic amounts of five or more elements and forms a single-phase solid solution. High-entropy alloys have attracted attention because they exhibit properties significantly different from those of ordinary alloys. Conventionally, high-entropy alloys generally used base metal elements such as Cr, Mn, Fe, Co, and Ni, but high-entropy alloys composed only of noble metal elements have also been synthesized (for example, Non-Patent Document 1).

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Non-Patent Documents

[0008]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] As described above, there has been a growing interest in multicomponent noble metal alloys composed of various noble metal elements. Therefore, it is considered beneficial if a thin film made of a multicomponent noble metal alloy can be formed by sputtering.

[0010] However, as described above, since the properties of noble metal alloys vary greatly depending on the composition, if there are variations in the alloy composition of the thin film, variations in the properties will also occur. Therefore, in order to fully exhibit the properties of noble metal alloys, noble metal alloy thin films with a highly uniform composition are required.

[0011] In particular, when manufacturing a thin film made of the above-mentioned high-entropy alloy, it is considered desirable to reduce the composition bias as much as possible. That is, if there is a composition bias in the thin film, the condition of containing each element by an equal atomic weight is not satisfied in that part, and there is a risk that the original properties of the high-entropy alloy cannot be obtained. In addition, when the composition bias is large, a single-phase solid solution may not be formed. Therefore, a significantly higher composition uniformity is required compared to conventional general alloys.

[0012] In order to manufacture a noble metal alloy thin film with an extremely uniform composition by sputtering in this way, it is necessary to eliminate as much as possible the factors that cause composition non-uniformity. Therefore, the target used for sputtering is also required to have a high degree of composition uniformity.

[0013] However, as a result of the inventors' studies, it has been found that when a sputtering target made of a multi-component noble metal alloy is manufactured by a conventional method, it is difficult to achieve the above-described high degree of compositional uniformity.

[0014] An object of the present invention is to solve the above problems and provide a sputtering target having a high degree of compositional uniformity.

Means for Solving the Problems

[0015] The inventors of the present invention conducted studies to achieve the above object. As a result, the following findings were obtained.

[0016] (1) When a target is manufactured by mixing and sintering a plurality of powders made of different noble metal elements, a compositional bias remains in the target. This is considered to be because the alloying of the noble metal elements does not proceed sufficiently.

[0017] (2) Even when a target is manufactured by a melting method using a plurality of powders made of different noble metal elements as raw materials, a compositional bias also remains in the target.

[0018] (3) On the other hand, if a noble metal alloy powder that has been uniformly alloyed in advance to satisfy predetermined conditions is sintered, it is possible to prevent a compositional bias in the target even when five or more noble metal elements are contained. The target obtained by this method had an extremely uniform composition.

[0019] The present invention has been completed based on the above findings, and the gist thereof is as follows.

[0020] 1. A sputtering target made 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 range of diffraction angle 2θ of 38 to 44° in the X-ray diffraction spectrum is 1, the sputtering target.

[0021] 2. For all of the noble metal elements, the coefficient of variation CV of the content measured by energy-dispersive X-ray spectroscopy is 0.2 or less, and the sputtering target according to 1 above.

[0022] 3. A method for manufacturing a sputtering target made of a noble metal alloy, An alloy powder preparation step of preparing an alloy powder as a raw material, And a sintering step of sintering the alloy powder, The alloy powder is A noble metal alloy powder composed of an alloy of 5 or more noble metal elements, and The average particle size is 0.1 to 100 μm, The number of peaks observed in the range of diffraction angle 2θ of 38 to 44° in the X-ray diffraction spectrum is 1, and the method for manufacturing a sputtering target.

Advantages of the Invention

[0023] According to the present invention, it is possible to provide a sputtering target made of an alloy of 5 or more noble metals with excellent compositional uniformity.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0025] Hereinafter, embodiments of the present invention will be specifically described. Note that the present invention is not limited to the embodiments described below.

[0026] [Sputtering Target] The sputtering target in one embodiment of the present invention is a sputtering target made of a noble metal alloy. The 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 range of diffraction angle 2θ of 38 to 44° in the X-ray diffraction spectrum is 1

[0027] · Noble metal element As the noble metals constituting the noble metal alloy, any noble metal element can be used without particular limitation. That is, the noble metal alloy is an alloy composed of at least 5 elements selected from the group consisting of Au, Ag, Pt, Pd, Rh, Ir, Ru, and Os.

[0028] Among the above noble metal elements, Os has the property of being easily volatilized when heated during the manufacturing process. Therefore, from the viewpoint of ease of manufacturing, the noble metal alloy is preferably an alloy composed of at least 5 elements selected from the group consisting of Au, Ag, Pt, Pd, Rh, Ir, and Ru.

[0029] The number of noble metal elements constituting the alloy may be 5 or more, and the upper limit is not particularly limited. That is, it may contain all 8 noble metal elements. The number of noble metal elements may be 6 or 7.

[0030] Note that the ratio (content) of each noble metal element contained in the above noble metal alloy is not particularly limited and can be any value. For example, when manufacturing a sputtering target made of the high-entropy alloy described above, the ratio of each noble metal element contained in the noble metal alloy may be set to a substantially equal value. Specifically, among the contents (atomic %) of all noble metal elements contained in the noble metal alloy, ΔC defined as the difference (Cmax - Cmin) between the maximum content (Cmax) and the minimum content (Cmin) 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 ΔC, the better, and the lower limit may be 0 atomic %.

[0031] ·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 derived from each element are observed in the range of diffraction angle 2θ of 38 to 44° in the X-ray diffraction spectrum. Therefore, in the present invention, the number of peaks observed in the above range is set to 1. If the number of peaks in the XRD spectrum is 1, it can be said that alloying has been achieved uniformly. Note that the range of diffraction angle 2θ for counting the number of peaks is defined as 38 to 44° because the peaks of noble metal elements (Au, Ag, Pt, Pd, Rh, Ir, Ru, and Os) are observed in this range.

[0032] ·Coefficient of variation CV of the content measured by EDX In the present invention, for all the metal elements constituting the noble metal alloy, the coefficient of variation CV of the content measured by energy dispersive X-ray spectroscopy (EDX) 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 noble metal element constituting the noble metal alloy is 0.2 or less. According to the present invention, a fired body of a noble metal alloy that is extremely uniform can be obtained such that the coefficient of variation CV is 0.2 or less. On the other hand, since the lower the coefficient of variation CV, the better, the lower limit is not particularly limited. Typically, the coefficient of variation CV may be 0.05 or more, and may be 0.08 or more.

[0033] If the coefficient of variation CV of the content measured by EDX satisfies the above conditions, it can be said that alloying is more uniform.

[0034] · Crystallite size The crystallite size of the noble metal alloy constituting the sputtering target of the present invention is not particularly limited. However, the lower the crystallite size, the higher the smoothness of the thin film obtained by sputtering. Also, generation of particles during sputtering can be suppressed. Therefore, the crystallite size of the noble 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, but typically, it may be 1 nm or more, may be 10 nm or more, or may be 20 nm or more.

[0035] The above crystallite size can be determined from the half-value width of the diffraction peak obtained by X-ray diffraction (XRD) measurement.

[0036] In the present invention, the sputtering target means a target material used in sputtering. Therefore, a backing plate can be joined to the sputtering target as the target material to form a sputtering target assembly. In other words, the sputtering target assembly in another embodiment of the present invention includes the sputtering target as the target material and a backing plate joined to the sputtering target.

[0037] [Manufacturing method] Next, a method for manufacturing a sputtering target according to an embodiment of the present invention will be described.

[0038] The sputtering target of the present invention can be manufactured by a sintering method. That is, the method for manufacturing a sputtering target according to an embodiment of the present invention includes an alloy powder preparation step and a sintering step. Hereinafter, each step will be specifically described. Note that matters not particularly mentioned can be carried out according to the general manufacturing technology of sputtering targets.

[0039] [Alloy powder preparation step] First, an alloy powder as a raw material is prepared. The alloy powder is a noble metal alloy powder composed of an alloy of 5 or more noble metal elements and needs to satisfy the following conditions. · The average particle size is 0.1 to 100 μm, · The number of peaks observed in the range of diffraction angle 2θ of 38 to 44° in the X-ray diffraction spectrum is 1

[0040] · Average particle size: 0.1 to 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, making it unsuitable for target manufacturing. Therefore, the average particle size should be 0.1 μm or more. On the other hand, if the average particle size is larger than 100 μm, the finally obtained target will become brittle. Therefore, the average particle size is 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.

[0041] ·Number of peaks in the XRD spectrum: 1 In the finally obtained target, in order to make the number of peaks observed in the diffraction angle 2θ range of 38 - 44° in the X-ray diffraction spectrum be 1, it is necessary that the number of peaks observed in the diffraction angle 2θ range of 38 - 44° for the alloy powder is also 1.

[0042] ·Coefficient of variation CV of the content measured by EDX For all metal elements constituting the above noble metal alloy powder, the coefficient of variation CV of the content measured by energy dispersive X-ray spectroscopy (EDX) 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 noble metal element constituting the noble metal alloy powder is 0.2 or less. By using a powder with a coefficient of variation CV of 0.2 or less as the alloy powder, the coefficient of variation CV can also be made 0.2 or less in the finally obtained target. Since the lower the coefficient of variation CV, the better, the lower limit is not particularly limited. Typically, the coefficient of variation CV may be 0.05 or more, and may be 0.08 or more.

[0043] ·Crystallite size: 60 nm or more The crystallite size of the alloy powder used as a raw material is not particularly limited. However, using an alloy powder with a larger crystallite size as a raw material results in less shrinkage during the production process of the target and easier forming. Therefore, the crystallite size of the alloy powder is preferably 60 nm or more, and more preferably 80 nm or more. On the other hand, the upper limit of the crystallite size is not particularly limited, but it may typically be 140 nm or less, and may be 120 nm or less. Note that such a noble metal alloy powder with a large crystallite size can be produced by the method described later.

[0044] The above crystallite size can be determined from the half-value width of the diffraction peak obtained by X-ray diffraction (XRD) measurement.

[0045] The method for preparing the above alloy powder is not particularly limited. In one embodiment of the present invention, a noble metal alloy powder produced by the following method can be used as the above alloy powder. Note that the production method disclosed here can be broadly classified into two methods: a method of performing firing only once and a method of performing firing multiple times. The former is a method suitable for producing powders with a relatively small average particle size, and the latter is a method suitable for producing powders with a relatively large average particle size. Hereinafter, each production method will be described.

[0046] · Production of powders with a relatively small average particle size FIG. 1 is a flowchart showing a method for producing a noble metal alloy powder according to an embodiment of the present invention. As shown in FIG. 1, the method for producing a noble metal alloy powder according to an embodiment of the present invention includes the following steps (1) to (6). According to this production method, a noble metal alloy powder with an average particle size of generally 10 μm or less can be produced. 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

[0047] This manufacturing method is suitable for manufacturing powders with a relatively small average particle size. Specifically, this manufacturing method is suitable for manufacturing powders with an average particle size of about 10 μm or less, more suitable for manufacturing powders with an average particle size of 5 μm or less, and even more suitable for manufacturing powders with an average particle size of 3 μm or less. Hereinafter, each step will be specifically described.

[0048] (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 raw material powders are prepared separately for each of the noble metal elements constituting the finally manufactured noble metal alloy. For example, when manufacturing a quinary alloy, five raw material powders may be prepared.

[0049] The particle size of the raw material powder is not particularly limited, but from the perspective of making the finally obtained noble metal alloy powder more uniform, it is preferable to use fine raw material powders. Specifically, it is preferable that the average particle size of each raw material powder used is 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 average particle size is not particularly limited either. For example, it may be 1 nm or more, 5 nm or more, or 10 nm or more.

[0050] Here, the average particle size of the raw material powder is defined as referring to the average particle size d obtained using the true sphere model from the specific surface area of the raw material powder. The average particle size d (μm) is generally called the BET diameter. Specifically, the density ρ (g / cm 3 ) and the BET specific surface area s (m 2 / g) of the particles constituting the raw material powder can be calculated by the following formula (1). d = 6 / ρs …(1)

[0051] The raw material powder may be either a metal powder or a metal oxide powder. For example, for Pt, Pt powder can be used, or platinum oxide (PtO2) powder can also be used. Similarly, oxide powders such as rhodium oxide (RhO2, RhO3) and palladium oxide (PdO) can be optionally used. These oxide powders thermally decompose during firing and function as noble metal sources. Basically, regardless of whether a metal powder or a metal oxide powder is used, there is no change in the function as a raw material, so it may be selected according to the availability of the powder, etc.

[0052] However, for Ru, it is preferable to use metallic ruthenium powder as the raw material rather than ruthenium oxide (RuO2) powder.

[0053] For example, in one embodiment of the present invention, it is preferable to use at least five 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 as the raw material powder.

[0054] (2) Slurry preparation step Next, the raw material powder, calcium carbonate, and water are mixed to form a slurry, and the pH of the slurry is set to 8.0 or higher. The calcium carbonate is thermally decomposed in the firing step and at least partially becomes calcium oxide. Since calcium carbonate and calcium oxide have the effect of inhibiting the grain growth of the noble metal alloy, it contributes to the refinement of the finally obtained noble metal alloy powder.

[0055] The addition amount of the calcium carbonate is not particularly limited, but from the viewpoint of enhancing the above effects, it is preferably 0.1 times or more, more preferably 0.2 times or more, and even more preferably 0.5 times or more in terms of the weight ratio to the total raw material powder. On the other hand, the upper limit is not particularly limited either, but the effect will saturate even if added excessively. Therefore, it is preferably 10 times or less, more preferably 5 times or less, and even more preferably 2 times or less in terms of the weight ratio to the total raw material powder.

[0056] The calcium carbonate can be added in any form. Typically, calcium carbonate powder may be used. When using calcium carbonate powder, the average particle size of the calcium carbonate powder is not particularly limited, but it is preferably 0.2 to 1.0 μm. Here, the average particle size of the calcium carbonate refers to the average particle size d obtained using the true sphere model from the specific surface area of the calcium carbonate. The average particle size d (μm) is generally called the BET diameter. Specifically, it can be calculated by the following formula (1) from the density ρ (g / cm 3 ) of the particles constituting the calcium carbonate and the BET specific surface area s (m 2 / g). d = 6 / ρs …(1)

[0057] pH: 8.0 or more In the above slurry preparation step, it is important to make the pH of the slurry 8.0 or more. If the pH of the slurry is less than 8.0, the uniformity of the composition in the finally obtained noble metal alloy powder will decrease, and the coefficient of variation CV in the EDX measurement will increase. Also, if the pH of the slurry is less than 8.0, the number of peaks observed in the XRD spectrum in the range of diffraction angle 2θ of 38 to 44° cannot be made 1.

[0058] The method for preparing the pH of the slurry is not particularly limited. For example, when the pH is less than 8.0, an alkali may be added to the slurry. For example, the pH can be adjusted by adding at least one selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, and ammonia to the slurry. Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide. Examples of the alkaline earth metal hydroxide include calcium hydroxide. The pH of the slurry may be measured with a general pH meter.

[0059] Note that the upper limit of the pH of the slurry is not particularly limited. However, even if the pH is increased above 10, the effect of alloy homogenization saturates. Also, when the pH is increased above 10, a large amount of alkali needs to be added. As a result, a large amount of sodium, potassium, etc. added as the alkali may remain as impurities. Also, when ammonia is used as the alkali, a large amount of harmful ammonia gas is generated during the manufacturing process, which is dangerous. Therefore, it is preferable that the pH of the slurry be 10 or less.

[0060] (3) Mixing step In the mixing step, the slurry is mixed. For the mixing, any mixer can be used without particular limitation. Examples of the mixer include a ball mill, a planetary mill (planetary ball mill), a bead mill, and an attritor. From the viewpoint of more uniform mixing, it is preferable to use a bead mill or a planetary mill, and among them, it is particularly preferable to use a bead mill.

[0061] (4) First firing step Next, the slurry mixed in the mixing step is fired in a non-oxidizing atmosphere to obtain alloy powder. In the present invention, since alloy powder can be obtained by firing, the purity can be made higher than in the case of using the wet reduction method. The firing can be carried out with any apparatus without particular limitation. Typically, an electric furnace can be used.

[0062] The first firing step is performed in a non-oxidizing atmosphere to prevent oxidation of the components. The non-oxidizing atmosphere is not particularly limited, and any non-oxidizing atmosphere can be used. Typically, a nitrogen gas atmosphere, an argon gas atmosphere, an atmosphere composed of hydrogen gas and nitrogen gas, an atmosphere composed of hydrogen gas and argon gas, etc. can be used. From the viewpoint of reliably preventing oxidation of the raw materials, it is preferable to use an atmosphere composed of hydrogen gas and nitrogen gas or an atmosphere composed of hydrogen gas and argon gas.

[0063] The firing temperature (first firing temperature) in the first firing step is not particularly limited, and any temperature can be used as long as it can fire the powder. The preferable first firing temperature depends on the melting point T M of the noble metal alloy to be used. From the viewpoint of promoting diffusion of the raw material powder and further enhancing crystallinity, the first firing temperature T1 is preferably T L or higher as defined by the following formula. On the other hand, the upper limit of the first firing temperature is not particularly limited, but if the first firing temperature is excessively high, necking may occur between alloy particles and coarse powder may be generated. Therefore, the first firing temperature T1 is preferably T H or lower as defined by the following formula. T L (°C) = T M (K) × 0.55 - 273.15 T H (°C) = T M (K) × 0.77 - 273.15 Here, T M is the weighted average of the melting points of all noble metal elements constituting the noble metal alloy. The content (mass%) of each noble metal element is used for the calculation of the weighted average.

[0064] The firing time in the first firing step is not particularly limited, but from the viewpoint of grain growth of the alloy, it is preferably 1 hour or more. On the other hand, from the viewpoint of production efficiency, it is preferably 5 hours or less.

[0065] (5) First acetic acid treatment step Next, the fired product obtained in the first firing step is treated with acetic acid. By performing the acetic acid treatment, calcium contained in the fired product can be removed. When an acid other than acetic acid (for example, hydrochloric acid or nitric acid) is used, not only calcium but also noble metal elements will dissolve, and as a result, the uniformity of the alloy will deteriorate. On the other hand, acetic acid will not dissolve noble metal elements regardless of the concentration. Therefore, it is important to use acetic acid for removing calcium in the present invention.

[0066] The method of the acetic acid treatment is not particularly limited. Typically, the fired product may be stirred in an aqueous acetic acid solution to dissolve calcium contained in the fired product. The acetic acid treatment can be performed any number of times, one or more times. From the viewpoint of reducing the amount of calcium remaining as an impurity as much as possible, it is preferable to perform the acid treatment two or more times, and more preferably three or more times. When performing the acetic acid treatment multiple times, a new aqueous acetic acid solution may be used each time.

[0067] In the acetic acid treatment, the fired product may be put into the previously prepared aqueous acetic acid solution, or first, the fired product may be put into pure water, and then acetic acid may be added to the pure water.

[0068] Hereinafter, specific examples of a suitable acetic acid treatment method will be described.

[0069] First, the fired product is put into pure water and stirred. As a result, calcium oxide contained in the fired product changes to calcium hydroxide. Next, acetic acid is further added and stirred to dissolve the calcium hydroxide. Then, the stirring is stopped and the mixture is allowed to stand, the powder is allowed to settle, and the supernatant is removed. The above is one acetic acid treatment. Thereafter, pure water and acetic acid are further added, and stirring, standing, and supernatant removal are repeated twice.

[0070] (6) First washing step Next, the fired product (alloy powder) after the acetic acid treatment is washed with water and dried (washing step). By washing with water, acids and calcium in a dissolved state in the acid are removed.

[0071] For the above-mentioned water washing, it is preferable to use pure water. The method of performing the water washing is not particularly limited. For example, after removing the supernatant in the above acetic acid treatment, pure water can be added and stirred for washing. After stopping the stirring, let it stand to allow the powder to settle, and then remove the supernatant. It is preferable to repeat the above water washing two or more times, and more preferably three or more times. After the water washing, it is preferable to filter to separate the moisture and the powder, and use the obtained powder for the next drying.

[0072] The above-mentioned drying can be carried out by any method as long as it can remove moisture. Natural drying may be used, but in order to efficiently remove moisture, it is preferable to perform heat drying. When performing heat drying, the heating temperature is not particularly limited, but it is preferably 50°C or higher, and more preferably 80°C or higher. It may also be 100°C or higher. The drying time is also not particularly limited and can be set to any time according to the amount of powder to be dried. From the perspective of sufficiently drying, it is preferably 1 hour or more, and more preferably 5 hours or more. It may also be 10 hours or more. On the other hand, the upper limit of the above heating time is not particularly limited, but typically it is preferably 100 hours or less, and more preferably 50 hours or less.

[0073] In addition, after the above drying, it is preferable to further sieve the obtained noble metal alloy powder. Thereby, the particles aggregated in the above washing process can be separated.

[0074] By the above procedure, noble metal alloy powder with a relatively small average particle size, specifically, 10 μm or less, can be obtained.

[0075] ·Manufacture of powder with a relatively large average particle size Next, a method for manufacturing noble metal alloy powder in another embodiment of the present invention will be described. The manufacturing method of this embodiment is a method suitable for manufacturing relatively large powder having an average particle size of up to 100 μm. Specifically, this manufacturing method is suitable for manufacturing powder with an average particle size exceeding 5 μm, and more suitable for manufacturing powder with an average particle size exceeding 10 μm.

[0076] Figure 2 is a flowchart showing a method for manufacturing a noble metal alloy powder according to the present embodiment. As shown in Figure 2, the method for manufacturing a noble metal alloy powder according to an embodiment of the present invention includes the following steps (7) to (10) in addition to the steps (1) to (6) in the embodiment shown in Figure 1. Further, a particle size adjustment step can be optionally performed before the second firing step. (7) Second firing step (8) Third firing step (9) Second acetic acid treatment step (10) Second washing step

[0077] However, among the above steps (7) to (10), the only essential step is the (7) second firing step, and the remaining steps (8) to (10) are optional steps. In other words, the method for manufacturing a noble metal alloy powder according to the present embodiment can be roughly classified into two methods: a method for obtaining a noble metal alloy powder by the above steps (1) to (7), and a method for obtaining a noble metal alloy powder by the above steps (1) to (10). In the former method, two firings, namely the first firing step and the second firing step, are performed. In the latter method, three firings, namely the first firing step, the second firing step, and the third firing step, are performed.

[0078] Here, for the sake of explanation, the steps from the raw material preparation step to the first washing step are conveniently referred to as "pre-steps", and the steps from the second firing step onwards are referred to as "post-steps". Further, a particle size adjustment step may be provided after the first washing step and before the second firing step. When the particle size adjustment step is implemented, as shown in Figure 3, the particle size adjustment step shall be included in the post-steps.

[0079] In this embodiment, first, in the previous process, 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 size of generally 10 μm or less. And the primary particles aggregate with each other to form a substantially spherical aggregate (secondary particle), and the secondary particle has a particle size on the order of several tens to one hundred μm. Therefore, by further performing a subsequent process on the powder, while maintaining high crystallinity and compositional uniformity, the average particle size can be made to exceed 10 μm and be 100 μm or less.

[0080] ·Particle size adjustment process In the subsequent process, prior to the following second firing process, the particle size of the alloy powder after the first cleaning process may be adjusted (particle size adjustment process). By performing particle size adjustment, a noble metal alloy powder with a desired particle size can be obtained more easily. The particle size of the finally obtained noble metal alloy powder is substantially equal to the particle size of the powder after particle size adjustment (that is, the powder to be subjected to the following second firing process). Therefore, in the particle size adjustment process, the particle size may be adjusted according to the particle size of the noble metal alloy powder desired to be finally obtained.

[0081] The method for adjusting the particle size is not particularly limited, but typically, the alloy powder may be sieved. The sieve is not particularly limited and any one can be used. In addition, either the powder that has passed through the sieve (undersize) or the powder that has not passed through the sieve (oversize) can be used. Also, 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 by the first sieve, and then the particle size may be adjusted to the desired particle size by the subsequent sieve.

[0082] When sieving alloy powder, in addition to the effect of adjusting the particle size, the effect of spheroidizing the powder particles can also be obtained. This is presumably because the alloy powder, which is an aggregate, is subjected to mechanical forces such as vibration, rolling, and friction on the sieve, reducing the irregularities on the particle surface. The spheroidizing effect can be obtained both in the undersize fraction and the oversize fraction, but it is more prominent in the oversize fraction. Therefore, from the perspective of 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 (oversize) that did not pass through the sieve.

[0083] ·Second firing step Next, the alloy powder is second-fired (second firing step). When the particle size is not adjusted, the alloy powder after the first washing step may be second-fired, and when the particle size is adjusted, the alloy powder after the particle size adjustment may be second-fired. The secondary particles before firing are brittle and easily break apart due to physical contact or impact. Therefore, by performing the second firing, the primary particles forming the secondary particles are necked together, fixing the state of the particles.

[0084] Note that calcium carbonate is used in the subsequent third firing step to inhibit the necking between secondary particles. As described above, since 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 break apart, making it difficult to control the particle size. Therefore, by performing the second firing to stabilize the structure of the secondary particles and then mixing with calcium carbonate, it becomes possible to appropriately control the particle size.

[0085] The temperature (second firing temperature) when performing the second firing is not particularly limited and can be any temperature as long as sintering between primary particles occurs. The preferred second firing temperature depends on the melting point T M of the noble metal alloy used. Therefore, the second firing temperature T2 is preferably T L or higher and T H or lower as follows. T L (°C) = T M (K) × 0.45 - 273.15 TH (°C) = T M (K) × 0.60 - 273.15 Here, T M is the weighted average of the melting points of all noble metal elements constituting the noble metal alloy. The content (mass%) of each noble metal element is used for the calculation of the weighted average.

[0086] Also, the time for the second firing (second firing time) is not particularly limited, but it is preferably 5 hours or less, more preferably 2 hours or less. Further, the second firing time is preferably 30 minutes or more, more preferably 40 minutes or more, and even more preferably 50 minutes or more.

[0087] The second firing step is performed in a non-oxidizing atmosphere to prevent oxidation of the components. The non-oxidizing atmosphere is not particularly limited, and any non-oxidizing atmosphere can be used. Typically, a nitrogen gas atmosphere, an argon gas atmosphere, an atmosphere composed of hydrogen gas and nitrogen gas, an atmosphere composed of hydrogen gas and argon gas, etc. can be used. From the viewpoint of surely preventing oxidation of the raw materials, it is preferable to use an atmosphere composed of hydrogen gas and nitrogen gas or an atmosphere composed of hydrogen gas and argon gas.

[0088] In one embodiment of the present invention, the alloy powder obtained in the above second firing step can be used as a raw material for manufacturing a sputtering target. Further, the following treatment can also be performed on the alloy powder.

[0089] · Third firing step The alloy powder after the second firing is further fired in a non-oxidizing atmosphere (third firing step). By performing firing in two steps in this way, the primary particles constituting the secondary particles can be more firmly bonded to each other, and the sphericity of the particles can be further increased. The firing can be performed by any device without particular limitation. Typically, an electric furnace can be used.

[0090] In the third firing step, in order to prevent secondary particles from binding to each other to form coarse particles, firing is performed in a state of being mixed with calcium carbonate which is a sintering inhibitor. The addition amount and form of the calcium carbonate are not particularly limited, but can be the same as those in the first firing step described above.

[0091] The third firing step is performed in a non-oxidizing atmosphere in order to prevent oxidation of the components. The non-oxidizing atmosphere is not particularly limited, and any non-oxidizing atmosphere can be used. Typically, a nitrogen gas atmosphere, an argon gas atmosphere, an atmosphere composed of hydrogen gas and nitrogen gas, an atmosphere composed of hydrogen gas and argon gas, etc. can be used. From the viewpoint of surely preventing oxidation of the raw materials, it is preferable to use an atmosphere composed of hydrogen gas and nitrogen gas or an atmosphere composed of hydrogen gas and argon gas.

[0092] The firing temperature (third firing temperature) in the third firing step is not particularly limited, and any temperature can be used as long as it can fire the powder. The preferable third firing temperature depends on the melting point T M which depends on the composition of the noble metal alloy to be used. The third firing temperature T3 is preferably set to T L or higher as defined by the following formula. On the other hand, the upper limit of the third firing temperature is not particularly limited, but if the third firing temperature is excessively high, necking may occur between alloy particles, and coarse powder may be generated. Therefore, the third firing temperature T3 is preferably set to T H or lower as defined by the following formula. T L (°C) = T M (K) × 0.55 - 273.15 T H (°C) = T M (K) × 0.77 - 273.15 Here, T M is the weighted average of the melting points of all noble metal elements constituting the noble metal alloy. In the calculation of the weighted average, the content (mass%) of each noble metal element is used.

[0093] Also, the firing time in the third firing step is not particularly limited, but it is preferably 1 hour or more. On the other hand, from the viewpoint of production efficiency, it is preferably 5 hours or less.

[0094] ·Second acetic acid treatment step Next, the alloy powder (fired product) after the third firing step is treated with acetic acid (second acetic acid treatment step). By performing the acetic acid treatment, calcium contained in the fired product can be removed. When an acid other than acetic acid (for example, hydrochloric acid or nitric acid) is used, not only calcium but also precious metal elements will dissolve, and as a result, the uniformity of the alloy will decrease. In contrast, with acetic acid, there is no risk of dissolving precious metal elements regardless of the concentration. Therefore, it is important to use acetic acid for removing calcium in the present invention.

[0095] The conditions of the second acetic acid treatment step are not particularly limited, but can be the same as those of the first acetic acid treatment step described above.

[0096] ·Second washing step The alloy powder after the first acetic acid treatment is washed with water and dried (second washing step). By washing with water, acetic acid and calcium dissolved in the acetic acid can be removed. The conditions of the second washing treatment step are not particularly limited, but can be the same as those of the first washing step described above.

[0097] Through the above treatments, a precious metal alloy powder satisfying the above-described conditions can be obtained.

[0098] [Sintering step] Next, the alloy powder prepared in the above alloy powder preparation step is sintered to obtain a target (sintering step). The method of performing the sintering is not particularly limited and can be performed by any method. When performing the sintering, it is preferable to heat the alloy powder and pressurize the alloy powder. The pressurization may be performed simultaneously with the heating, prior to the heating, or both. The method of performing the pressurization is not particularly limited. For example, the alloy powder can be pressurized in a state where it is placed in a mold. The pressurization may be performed only in the uniaxial direction or isotropically. For example, the sintering can be performed by hot press sintering, hot isostatic pressing (HIP), or spark plasma sintering (SPS).

[0099] The conditions for performing the sintering are not particularly limited and may be adjusted according to the noble metal alloy powder used. For example, if the sintering temperature is too low, the bonding between the powders does not proceed sufficiently. Therefore, the sintering temperature T S in the sintering process is preferably defined by the following formula for T L or higher. On the other hand, the upper limit of the sintering temperature is not particularly limited, but even if it is set too high, the effect saturates. Therefore, the sintering temperature T S is preferably defined by the following formula for T H or lower. T L (°C) = T M (K) × 0.51 - 273.15 T H (°C) = T M (K) × 0.86 - 273.15 Here, T M is the weighted average of the melting points of all noble metal elements constituting the noble metal alloy. The content (mass%) of each noble metal element is used for the calculation of the weighted average.

[0100] The temperature increase to the sintering temperature can be performed at an arbitrary rate. For example, the time (temperature increase time) from the start of the temperature increase to the arrival at the sintering temperature may be 30 to 240 minutes, or may be 60 to 180 minutes.

[0101] After reaching the sintering temperature, it is preferable to maintain the temperature. The time for maintaining the sintering temperature is not particularly limited, but it is preferably 30 minutes or more, and more preferably 1 hour or more. On the other hand, even if the time is maintained for an excessively long time, the effect saturates. Therefore, the holding time is preferably 5 hours or less, and more preferably 4 hours or less.

[0102] The sintering step is preferably carried out in a non-oxidizing atmosphere in order to prevent oxidation of the components. The non-oxidizing atmosphere is not particularly limited, and any non-oxidizing atmosphere can be used. Typically, a nitrogen gas atmosphere, an argon gas atmosphere, an atmosphere composed of hydrogen gas and nitrogen gas, an atmosphere composed of hydrogen gas and argon gas, etc. can be used. From the viewpoint of reliably preventing oxidation of the raw materials, it is preferable to use an atmosphere composed of hydrogen gas and nitrogen gas or an atmosphere composed of hydrogen gas and argon gas.

[0103] The firing can be carried out using any heating device. For example, an electric furnace can be used. As the electric furnace, it is preferable to use an electric furnace equipped with means for controlling the atmosphere inside the furnace.

[0104] After the firing step, processing or polishing may be optionally performed. That is, the method for manufacturing a sputtering target according to an embodiment of the present invention may optionally include one or both of a processing step and a polishing step after the sintering step.

Examples

[0105] Hereinafter, the effects of the present invention will be specifically described with reference to examples and comparative examples of the present invention, but the present invention is not limited thereto.

[0106] [Example 1]

[0107] · Alloy powder preparation step First, a quinary noble metal alloy powder composed of Ru, Rh, Pd, Ir, and Pt was produced by the following procedure.

[0108] As raw material powders, powders of Pt, Pd, IrO2, Ru, and Rh were prepared. Among the above powders, as the powders of Pt, Pd, and Ph, Pt black, Pd black, and Rh black were used respectively. Also, the Ru powder was prepared by reducing RuO2 powder.

[0109] The above raw material powders were mixed with calcium carbonate powder and water to form a slurry. At that time, an alkali for pH adjustment was added as necessary to make the pH of the slurry the value shown in Table 1. The addition amount of the calcium carbonate was 0.8 times the weight ratio with respect to the total amount of the above raw material powders. Also, as the water, pure water in an amount 2 times the weight ratio with respect to the total of the above raw material powders and the calcium carbonate was used.

[0110] Next, the above slurry was mixed with a planetary ball mill. The mixing conditions were: rotation speed: 200 rpm, mixing time: 6 hours. Also, a polyamide pot was used as the mixing container, and polyamide balls with a diameter of 10 mm were used as the media.

[0111] The slurry after the above mixing was fired in an N2-H2 atmosphere to obtain alloy powder. Specifically, first, the above slurry was dried at 130 °C with a dryer to remove moisture and obtain a mixed powder. Next, the mixed powder was put into a crucible and fired. The firing was carried out using an atmosphere-type temperature-rising electric furnace. The atmosphere during firing was a 3% H2 / 97% N2 gas atmosphere, the firing temperature was 1300 °C, and the firing time was 5 hours.

[0112] Next, the alloy powder obtained in the above firing process was subjected to acetic acid treatment, then washed with pure water and dried.

[0113] (Acetic acid treatment) The acetic acid treatment was carried out three times according to the following procedure. First, the fired product (alloy powder) was put into pure water and stirred. As a result, calcium oxide contained in the fired product was changed into calcium hydroxide. Next, acetic acid was further added and stirred to dissolve the calcium hydroxide. Then, the stirring was stopped and the mixture was allowed to stand still to precipitate the powder, and the supernatant was removed. The above constitutes one acetic acid treatment. Thereafter, pure water and acetic acid were further added, and stirring, standing, and supernatant removal were repeated two more times.

[0114] Next, washing with pure water was carried out three times according to the following procedure. First, after removing the supernatant in the third acetic acid treatment, pure water was added and stirred. After stopping the stirring, the mixture was allowed to stand still to precipitate the powder, and the supernatant was removed. The above washing was repeated three times.

[0115] (Drying) After the above washing, filtration was performed to separate the moisture and the powder, and the obtained powder was dried. The drying was carried out at 130 °C for 12 hours.

[0116] The powder after the above drying was sieved to crush the aggregated powder. As the sieve, a stainless steel test sieve with a mesh opening of 125 μm was used. Note that there were no particles remaining on the sieve, and all passed through the sieve.

[0117] Next, for the obtained noble metal alloy powder, the average particle size, crystallite size, number of peaks in the XRD spectrum, and coefficient of variation CV in EDX were measured according to the following procedure. The measurement results are shown in Table 1.

[0118] (Average Particle Size) The average particle size of the obtained noble metal alloy powder was measured using a laser diffraction particle size distribution analyzer MT-3000 manufactured by MicrotracBEL. Specifically, the alloy powder was put into an aqueous solution of sodium hexametaphosphate circulating inside the particle size distribution analyzer, dispersed by ultrasonic waves for 1 minute, and then the particle size distribution was measured. The volume-based 50% particle size (D50) obtained was taken as the average particle size of the noble metal alloy powder.

[0119] (Crystallite Size) The crystallite size of the obtained noble metal alloy powder was measured using a Rigaku X-ray diffractometer Ultima IV. In the said measurement, the powder to be measured was filled into a glass cell for powder measurement to make a sample. The measurement conditions were as follows: target: Cu, tube voltage: 40 kV, tube current: 40 mA, scanning range: 10 to 100°, sampling interval: 0.02°, scan speed: 30° / min. The crystallite size was determined from the half-value width of the diffraction peak obtained by the said measurement using the Scherrer equation.

[0120] (Number of peaks in the XRD spectrum) In the XRD spectrum obtained by the measurement of the above crystallite size, the number of peaks observed in the range of diffraction angle 2θ of 38 to 44° was determined. In counting the number of peaks, the XRD peaks were separated by Gaussian 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 were regarded as peaks.

[0121] (Coefficient of variation CV in EDX) The coefficient of variation CV of the content of each noble metal element contained in the obtained noble metal alloy powder was calculated from the measurement results of energy dispersive X-ray spectroscopy. For the measurement, a scanning electron microscope (SEM)-energy dispersive X-ray analyzer (EDX) JSM-6010LA manufactured by JEOL Ltd. was used, and the said alloy powder was fixed on a carbon tape to make a measurement sample. The measurement conditions were magnification: 3000 times, acceleration voltage: 20 kV. Under the said conditions, EDX quantitative measurement was performed at 30 randomly selected points to determine the content of each noble metal element. The coefficient of variation CV was calculated from the obtained average value and standard deviation of the content.

[0122] As can be seen from the results shown in Table 1, by the above procedure, a noble metal alloy powder having high crystallinity and excellent compositional uniformity was obtained.

[0123]

Table 1

[0124] ·Sintering process Next, the obtained noble metal alloy powder was sintered to produce a sputtering target. In this example, the sintering was carried out by hot press sintering. The specific procedure was as follows.

[0125] First, 238 g of the above-mentioned noble metal alloy powder was put into a graphite sintering mold. The internal shape of the sintering mold was 80 mm × 80 mm. Next, the powder in the sintering mold was hot pressed under the conditions of a nitrogen atmosphere, a temperature of 1100 °C, a pressure of 15.5 MPa, and a holding time of 30 minutes. After cooling, the sputtering target was taken out of the sintering mold.

[0126] When the obtained sputtering target was cut with a commercially available automatic cutting machine, it could be cut without problems. The cut end face had a metallic luster. Also, the sputtering target could be polished by a normal method, and the polished surface had a metallic luster. Thus, since the sputtering target of the present invention can be processed and polished by a normal method, it can be said to be suitable as a target material in that respect.

[0127] Next, regarding the obtained sputtering target, the crystallite size, the number of peaks in the XRD spectrum, and the coefficient of variation CV in EDX were measured by the following procedure. The measurement results are shown in Table 2.

[0128] (Crystallite size) The crystallite size of the obtained target was measured with a Rigaku X-ray diffractometer Ultima IV. In the measurement, the target to be measured was used as a sample. The measurement conditions were: target: Cu, tube voltage: 40 kV, tube current: 40 mA, scanning range: 10 to 100°, sampling interval: 0.02°, and scan speed: 30° / min. The crystallite size was determined from the half-value width of the diffraction peak obtained by the measurement using the Scherrer equation.

[0129] (Number of peaks in the XRD spectrum) In the XRD spectrum obtained by measuring the crystallite size, the number of peaks observed in the range of diffraction angle 2θ from 38 to 44° was determined. In counting the number of peaks, the XRD peaks were separated by Gaussian 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 were regarded as peaks.

[0130] (Coefficient of variation CV in EDX) The coefficient of variation CV of the content of each noble metal element contained in the obtained target was calculated from the measurement results of energy dispersive X-ray spectroscopy. For the measurement, a scanning electron microscope (SEM)-energy dispersive X-ray analyzer (EDX) JSM-6010LA manufactured by JEOL Ltd. was used, and the target was fixed on a carbon tape to obtain a measurement sample. The measurement conditions were a magnification of 3000 times and an acceleration voltage of 20 kV. Under the above conditions, EDX quantitative measurement was performed at 30 randomly selected points to determine the content of each noble metal element. The coefficient of variation CV was calculated from the obtained average value and standard deviation of the content.

[0131]

Table 2

[0132] As can be seen from the results shown in Table 2, by the above procedure, a sputtering target having excellent compositional uniformity and high crystallinity was obtained.

[0133] Using the above sputtering target, magnetron sputtering was actually performed to form a noble metal alloy powder film. When the coefficient of variation CV in EDX was measured for the obtained film in the same manner as the evaluation of the target, 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 seen that a noble metal alloy film having excellent compositional uniformity can be obtained by using a sputtering target that satisfies the conditions of the present invention. Note that the film obtained by sputtering is generally amorphous. Therefore, the XRD spectrum of the above film was not measured.

[0134] [Comparative Example 1] Next, for comparison, a sputtering target was produced by sintering a mixed powder. As the mixed powder, a mixed powder obtained by mixing Ru powder, Rh powder, Pd powder, Ir powder, and Pt powder so that each noble metal element had 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.

[0135] 10 g of the mixed powder was put into a water-cooled copper hearth, completely melted by arc melting, then allowed to cool to room temperature, and taken out from the water-cooled copper hearth. The arc melting was carried out in an Ar atmosphere. Other conditions were the same as in Example 1 above.

[0136] Regarding the obtained sputtering target, in the same manner as in Example 1 above, the number of peaks in the XRD spectrum and the coefficient of variation CV in EDX were measured. The measurement results are also shown in Table 2. In the target of Comparative Example 1, multiple peaks of the XRD spectrum used for calculating the crystallite size were observed. Therefore, since the crystallite size could not be uniquely determined, the crystallite size was not shown in Table 2.

[0137] As shown in Table 2, in Comparative Example 1 using a mixed powder, the number of peaks in the XRD spectrum was 4, indicating that alloying was not uniformly achieved. Also, the value of the coefficient of variation CV in EDX was significantly larger than that in Example 1. This also shows that the composition uniformity was inferior. In the arc melting method, although each powder was once melted and mixed, when using a mixed powder, a target with a uniform composition could not be obtained.

[0138] [Comparative Example 2] A sputtering target was produced by sintering the same mixed powder as in Comparative Example 1 above. However, in this Comparative Example 2, in order to mix the powders of each element more uniformly, the target was created by the following procedure.

[0139] First, specifically, the mixed powder, resin, and solvent were first mixed to form a paste. The contents in the paste were as follows: mixed powder: 80% by mass, resin: 1.8% by mass, and solvent: 18.2% by mass. Ethyl cellulose was used as the resin, and Texanol was used as the solvent.

[0140] Next, the obtained paste was further kneaded using a three-roll mill for a sufficient time to sufficiently disperse each component.

[0141] Next, the above paste was applied in a film form on an alumina substrate by the screen printing method. Then, drying was performed at 120 °C to volatilize the solvent contained in the applied paste to form a thin film. The obtained thin 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.

[0142] Next, pressure was applied to the noble metal powder-resin mixed powder to create a molded body (compressed powder). Then, the molded body was further sintered at 1300 °C to obtain a sintered body (target). The conditions were the same as those in Comparative Example 1 above.

[0143] Regarding the obtained sputtering target, in the same manner as in Example 1 above, the number of peaks in the XRD spectrum and the coefficient of variation CV in EDX were measured. The measurement results are also shown in Table 2. In the target of Comparative Example 2, a plurality of peaks in the XRD spectrum used for calculating the crystallite size were observed. Therefore, since the crystallite size could not be uniquely determined, the crystallite size was not shown in Table 2.

[0144] As shown in Table 2, in Comparative Example 2 using the mixed powder, even though it was sufficiently uniformly kneaded using a resin and a solvent and further fired at a sufficiently high temperature of 1300 °C, the compositional uniformity was inferior to that of Example 1.

[0145] [Comparative Example 3] Next, for comparison, a sputtering target was fabricated under the same conditions as in Example 1 above, except that arc melting was used instead of hot press sintering. The conditions for arc melting were the same as in Comparative Example 1 above.

[0146] Regarding 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 also shown in Table 2. In the target of Comparative Example 3, multiple peaks of the XRD spectrum used for calculating the crystallite size were observed. Therefore, since the crystallite size could not be uniquely determined, it was not shown in Table 2.

[0147] As shown in Table 2, in Comparative Example 1 using arc melting, although 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 2, indicating that alloying was not achieved uniformly. Also, the value of the coefficient of variation CV in EDX was significantly larger than that in Example 1. From this, it can be seen that the composition uniformity is inferior. It is considered that this non-uniform composition was due to segregation occurring during re-solidification after once melting the alloy.

[0148] As can be seen from the above results, in order to obtain a sputtering target with excellent composition uniformity that satisfies the conditions of the present invention, it is necessary to sinter a raw material powder that has been alloyed uniformly in advance to form the target.

Claims

1. A sputtering target made of a precious metal alloy, The precious metal alloy is Consists of five or more precious metal elements, and A sputtering target having one peak observed in an X-ray diffraction spectrum at a diffraction angle 2θ in the range of 38 to 44°.

2. 2. The sputtering target according to claim 1, wherein the coefficient of variation CV of the content of all the precious metal elements as measured by energy dispersive X-ray spectroscopy is 0.2 or less.

3. A method for producing a sputtering target made of a precious metal alloy, comprising the steps of: an alloy powder preparation step of preparing an alloy powder as a raw material; and a sintering step of sintering the alloy powder. The alloy powder is A precious metal alloy powder made of an alloy of five or more precious metal elements, The average particle size is 0.1 to 100 μm, A method for producing a sputtering target, in which the number of peaks observed in an X-ray diffraction spectrum within a diffraction angle 2θ range of 38 to 44° is 1.

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