Co-Cr-Pt oxide sputtering targets

Abstract

To provide a sputtering target capable of stabilizing a voltage in sputtering regardless of a method of changing a composition and a leakage magnetic flux density, and a manufacturing method of the same.SOLUTION: A Co-Cr-Pt-oxide based sputtering target includes Co of 50 at% or more, Cr of more than 0 at% and 20 at% or less, Pt of more than 0 at% and 25 at% or less, and a rest of one or more types of an oxide and an inevitable impurity. The sputtering target includes (A) includes a composite phase in which a Co oxide and a Pt oxide are dispersed alternately, and (B) ten or more metal Cr phases with an equivalent circle diameter of more than 10 μm and 100 μm or less within an observation area of 1 mm×1 mm under SEM at a magnification ratio of 50 times.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a magnetic thin film used for a magnetic recording layer of a magnetic recording medium, etc., particularly to a sputtering target suitable for forming a granular film, and more particularly to a Co—Cr—Pt—oxide-based sputtering target capable of improving discharge stability during sputtering.

Background Art

[0002] Various compositions are used in sputtering targets containing Co—Cr—Pt—oxide. For example, WO2013 / 136962 A1 (Patent Document 1) describes that, with Co—Cr—Pt—oxide as the main constituent, it contains one or more oxides selected from B, Si, Cr, Ti, Ta, W, Al, Mg, Mn, Ca, Zr, Y as the oxide, and one or more elements selected from B, Ti, V, Mn, Zr, Nb, Ru, Mo, Ta, W, Ag, Au, Cu, C as the additive element.

[0003] In these sputtering targets containing oxides which are insulators, there has been a problem of causing abnormal discharge and generating particles. To address this problem, generally, the probability of abnormal discharge is suppressed by making the oxides finely and uniformly present in the structure. For example, Patent Document 1 also describes that in a Co—Cr—Pt—oxide-based sputtering target, abnormal discharge can be suppressed by making the average particle size of the oxides as fine as 400 nm or less.

[0004] WO2013 / 125469 A1 (Patent Document 2) describes that in addition to making the oxide particles fine, by making the oxide particles present in a spherical or nearly spherical shape, segregation is reduced without causing a difference in the distribution between the locations where the oxides are present and the locations where the oxides are not present in a certain area on the target surface, and abnormal discharge and particle generation can be effectively suppressed.

[0005] On the other hand, many sputtering targets with these compositions are ferromagnetic, have low leakage flux density (PTF), and require high voltage application during sputtering. High voltage during sputtering leads to voltage instability and a tendency for arcing to occur. A common solution to this problem is to reduce the required voltage during sputtering by improving the PTF. Several methods for improving PTF have been published. For example, Japanese Patent Publication No. 2013-108110 (Patent Document 3) describes a sputtering target in which a non-magnetic phase and an oxide phase are dispersed, and which includes a magnetic phase and a non-magnetic phase, comprising a magnetic phase made of a Co-Cr alloy phase containing 85 at.% or more of Co, a non-magnetic phase made of a Co-Cr alloy phase containing more than 0 at.% and 75 at.% or less of Co, or a Co-Cr-Pt alloy phase containing more than 0 at.% and 73 at.% or less of Co, and a non-magnetic phase made of a Co-Pt alloy phase containing 12 at.% or less of Co, and describes how the magnetism of each phase can be controlled by the Co content ratio to improve PTF.

[0006] WO2011 / 089760 A1 (Patent Document 4) describes how leakage flux can be improved by having a metal substrate containing inorganic materials and a spherical phase (particularly with a diameter of 30 to 150 μm) containing 90 wt.% or more of Co.

[0007] Japanese Patent Publication No. 2016-176087 (Patent Document 5) describes how to improve leakage flux in a Co-Cr-Pt oxide ferromagnetic sputtering target by having a metal substrate containing inorganic material and a phase made of Pt with a minimum diameter of 10 to 150 μm. Also, WO2012 / 081669 A1 (Patent Document 6) describes how to improve leakage flux density and stabilize the voltage during sputtering in a Co-Cr-Pt oxide ferromagnetic sputtering target by having a metal substrate (A) in which oxide is dispersed, a Co-Pt alloy phase (B) with a diameter of 10 to 150 μm, and a Co alloy phase (C) with a diameter of 30 to 150 μm and containing 90 mol% or more of Co.

[0008] WO2010 / 110033 A1 (Patent Document 7) describes a Co-Cr-Pt oxide system having a phase (A) in which nonmagnetic particles are uniformly and finely dispersed within the alloy, and a spherical alloy phase (B) having a composition in which the central part contains 25 mol% or more Cr, and the Cr content decreases from the central part to the outer periphery, and improving the leakage magnetic flux by setting the volume of the alloy phase (B) in the target to 4% or more and 40% or less. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] WO2013 / 136962 A1 [Patent Document 2] WO2013 / 125469 A1 [Patent Document 3] Japanese Patent Publication No. 2013-108110 [Patent Document 4] WO2011 / 089760 A1 [Patent Document 5] Japanese Patent Publication No. 2016-176087 [Patent Document 6] WO2012 / 081669 A1 [Patent Document 7] WO2010 / 110033 A1 [Overview of the project] [Problems that the invention aims to solve]

[0010] Various compositions have been proposed for Co-Cr-Pt oxide sputtering targets. WO2013 / 125469 A1 (Patent Document 2) discloses suppressing abnormal discharge and particles by shaping oxide atoms into a predetermined form, and Japanese Patent Application Publication No. 2013-108110 (Patent Document 3) discloses improving PTF by controlling the magnetism of each phase by varying the Co content ratio of the magnetic and non-magnetic phases, but the voltage stability is not entirely satisfactory.

[0011] WO2011 / 089760 A1 (Patent Document 4) discloses how to improve leakage magnetic flux density and stabilize the voltage during sputtering by providing a spherical phase containing 90 wt.% or more of Co, Japanese Patent Application Publication No. 2016-176087 (Patent Document 5) discloses how to provide a phase made of Pt, WO2012 / 081669 A1 (Patent Document 6) discloses how to provide a Co-Pt alloy phase (B) and a Co alloy phase (C) containing 90 mol% or more of Co in predetermined sizes and shapes, and WO2010 / 110033 A1 (Patent Document 7) discloses how to improve leakage magnetic flux density and stabilize the voltage during sputtering by providing a spherical alloy phase (B) with a composition in which the center contains 25 mol% or more of Cr, and the Cr content decreases from the center to the outer periphery. However, the composition and leakage flux density of sputtering targets used in the manufacture of magnetic recording media are limited to those that exhibit the necessary magnetic properties for the recording media and are suitable for mass production, and therefore cannot be easily changed.

[0012] The present invention aims to provide a sputtering target and a method for manufacturing the same that can stabilize the voltage during sputtering without requiring measures to change the composition and leakage magnetic flux density. [Means for solving the problem]

[0013] To solve the above problems, the inventors conducted intensive research and found that they could create a sputtering target cross-section with 10 metallic Cr phase particles per mm², with a circular equivalent diameter exceeding 10 μm and less than or equal to 100 μm. 2 We discovered that by using a sputtering target having the above-mentioned structure, it is possible to reduce the voltage during sputtering and stabilize the discharge while maintaining the composition and leakage magnetic flux density, thus completing the present invention.

[0014] According to the present invention, a Co-Cr-Pt-oxide sputtering target having the following features is provided. [1] A Co-Cr-Pt oxide sputtering target comprising 50 at.% or more of Co, more than 0 at.% but 20 at.% or less of Cr, more than 0 at.% but 25 at.% or less of Pt, with the remainder being one or more oxides and unavoidable impurities, (A) A composite phase in which Co, Pt and oxides are dispersed in each other, (B) Metallic Cr phase, A sputtering target characterized by containing 10 or more metallic Cr phases with an equivalent circular diameter of over 10 μm and up to 100 μm within a 1 mm x 1 mm observation field of view using a 50x magnification SEM. [2] A Co-Cr-Pt-oxide sputtering target comprising 50 at.% or more of Co, more than 0 at.% but 20 at.% or less of Cr, more than 0 at.% but 25 at.% or less of Pt, with the remainder being one or more oxides and unavoidable impurities, (A) A composite phase in which Co, Pt and oxides are dispersed in each other, (B) Metallic Cr phase, (C) An alloy phase containing Co or Pt, Includes, A sputtering target characterized by containing 10 or more metallic Cr phases with an equivalent circular diameter of over 10 μm and up to 100 μm within a 1 mm x 1 mm observation field of view using a 50x magnification SEM. [3] The sputtering target according to [1] or [2] above, characterized in that the composite phase further comprises one or more selected from B, Al, Si, Ti, V, Mn, Fe, Ni, Cu, Zn, Ge, Nb, Mo, Ru, Rh, Pd, Ag, Ta, W, Re, Ir, and Au. [4] The sputtering target according to any one of [1] to [3] above, characterized in that the oxide is contained in the sputtering target in an amount of 20 vol.% or more and 50 vol.% or less. [5] The oxide is an oxide of an element selected from one or more arbitrary combinations selected from B, Mg, Al, Si, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Ga, Ge, Y, Zr, Nb, Mo, Ta, W, La, Ce, Nd, Sm, Gd, and is the sputtering target according to any one of [1] to [4] above. [6] The oxide contains at least a boron oxide, and is the sputtering target according to any one of [1] to [5] above. [7] A method for manufacturing the sputtering target according to [1] or [2] above, wherein a powder of a raw material containing Cr metal powder and oxide powder with an average particle size of 150 μm or more and 1000 μm or less is mixed and stirred to prepare a mixed powder for a target, The method for manufacturing a sputtering target is characterized by sintering the mixed powder for the target. [8] A method for manufacturing the sputtering target according to [1] or [2] above, wherein Cr metal powder with an average particle size of 10 μm or more and 150 μm or less is added to a mixed powder obtained by stirring and mixing other raw material powders and an oxide, and is the method for manufacturing a sputtering target. [Effect of the Invention]

[0015] The Co-Cr-Pt-oxide-based sputtering target of the present invention has a sputtering surface including a metal Cr phase having an area with a circle equivalent diameter exceeding 10 μm and 100 μm or less, even with the same composition and leakage magnetic flux density. Therefore, the voltage during sputtering can be reduced, the discharge can be stabilized, and the occurrence of arcing can be suppressed. [Brief Description of the Drawings]

[0016] [Figure 1] An explanatory diagram showing the definition of the circle equivalent diameter. [Figure 2] A tissue photograph in which each phase was identified by composition mapping analysis by EDX of the cross section of the sputtering target obtained in Example 1. [Figure 3]This image was obtained by magnifying a 1mm x 1mm field of view from an SEM image of the sputtering target cross-section obtained in Example 1 at an observation magnification of 50x, and then performing binarization processing. [Figure 4] Microstructure images showing the identification of each phase by EDX composition mapping analysis of the sputtering target cross-section obtained in Comparative Example 1. [Figure 5] Microstructure images showing the identification of each phase by EDX composition mapping analysis of the sputtering target cross-section obtained in Comparative Example 2. [Figure 6] Microstructure images showing the identification of each phase by EDX composition mapping analysis of the sputtering target cross-section obtained in Example 5. Preferred Embodiment

[0017] The present invention will be described in detail below with reference to the attached drawings, but the present invention is not limited thereto.

[0018] The Co-Cr-Pt oxide sputtering target of the present invention is characterized by containing 10 or more metallic Cr phases with an equivalent circle diameter of over 10 μm and up to 100 μm within a 1 mm × 1 mm observation field of view using a 50x magnification SEM. The equivalent circle diameter refers to the diameter when assuming a circle equivalent to the area of ​​the metallic Cr phase, whose shape is unspecified, as shown in Figure 1. As shown in the examples described later, the presence of metallic Cr phases with a large area reduces the voltage during sputtering and stabilizes the discharge. Within a 1 mm × 1 mm observation field of view using a 50x magnification SEM, the metallic Cr phases are dark or black, and the composite phases are light, i.e., gray to white. By binarizing the SEM observation image and processing the image, the dark or black metallic Cr phases can be extracted, their area can be determined, and the equivalent circle diameter can be calculated.

[0019] The metallic Cr phase can be identified by compositional mapping analysis of the cross-section of the sputtering target using EDX. When the weight ratio of the target-containing composition is quantitatively analyzed, the ideal is the region where it is 100 wt.% Cr, but considering unavoidable analytical errors, the region consisting of 95 wt.% or more, preferably 97 wt.% or more Cr and unavoidable impurities is defined as the "metallic Cr phase".

[0020] [First Embodiment] The Co-Cr-Pt oxide sputtering target of the first embodiment is a Co-Cr-Pt oxide sputtering target comprising 50 at.% or more of Co, more than 0 at.% but 20 at.% or less of Cr, more than 0 at.% but 25 at.% or less of Pt, with the remainder being one or more oxides and unavoidable impurities, (A) A composite phase in which Co, Pt and oxides are dispersed in each other, (B) Metallic Cr phase, The material is characterized by containing 10 or more metallic Cr phases with an equivalent circular diameter of over 10 μm and up to 100 μm within a 1 mm × 1 mm observation field of view using a 50x magnification SEM.

[0021] (B) The metallic Cr phase has an equivalent circle diameter greater than 10 μm and 100 μm or less, preferably 20 μm or more, more preferably 25 μm or more, preferably 70 μm or less, more preferably 60 μm or less. If the metallic Cr phase has an equivalent circle diameter greater than 100 μm, the difference in sputtering rate causes significant irregularities to appear on the target surface during sputtering, making it easier for problems such as particles and arcing to occur. If the metallic Cr phase has an equivalent circle diameter of 10 μm or less, it becomes difficult to obtain the voltage reduction effect during sputtering, and diffusion reactions between the metallic Cr phase and other phases tend to proceed at the grain boundaries, making it easier for the Cr alloy phase or Cr oxide phase to be generated.

[0022] The metallic Cr phase having an area within the above range is present in a 1mm x 1mm observation field of view using a 50x magnification SEM, with 10 or more particles, preferably 15 or more, more preferably 20 or more, preferably 300 or fewer, and more preferably 100 or fewer particles. If there are fewer than 10 metallic Cr phase particles, the effect of reducing the voltage during sputtering cannot be sufficiently obtained. If it can be confirmed that there are 10 or more particles within the 1mm x 1mm observation field of view, it can be said that the metallic Cr phase is uniformly dispersed throughout the entire sputtering target. If there are more than 300 metallic Cr phase particles, many irregularities will appear on the target surface during sputtering due to differences in sputtering rate, making it easier for problems such as particles and arcing to occur. Note that incomplete metallic Cr phase particles appearing at the edges of the observation field of view are not counted.

[0023] In sputtered thin films, Co plays a central role in the formation of granular magnetic particles. In the Co-Cr-Pt oxide sputtering target of the present invention, the Co content relative to the entire target is 50 at.% or more, preferably 55 at.% or more, more preferably 60 at.% or more, preferably 90 at.% or less, and more preferably 80 at.% or less, and is within the range of content required for a recording layer in a magnetic recording medium.

[0024] The Pt content in the Co-Cr-Pt oxide sputtering target of the present invention is greater than 0 at.% and less than or equal to 25 at.% of the target, preferably 5 at.% or more, more preferably 10 at.% or more, preferably 23 at.% or less, and more preferably 22 at.% or less, and is within the range of content required for a recording layer in a magnetic recording medium. In the sputtered thin film, Pt has the function of increasing the magnetic moment of Co by alloying with Co, which is a granular magnetic particle, and plays a role in adjusting the magnetic strength of the magnetic particles.

[0025] In the Co-Cr-Pt oxide sputtering target of the present invention, the Cr content relative to the entire target is greater than 0 at.% and less than or equal to 20 at.%; preferably 1 at.% or more; more preferably 3 at.% or more; preferably 15 at.% or less; and more preferably 10 at.% or less, within the range of content required for a recording layer in a magnetic recording medium. In the sputtered thin film, Cr has the function of reducing the magnetic moment of Co, which is a granular magnetic particle, by alloying with it, and plays a role in adjusting the magnetic strength of the magnetic particles.

[0026] In a sputtered thin film, the oxide acts as a barrier separating the alloy phases to form a granular structure. In the Co-Cr-Pt-oxide sputtering target of the present invention, the oxide content relative to the entire target is preferably 20 vol.% to 50 vol.%, more preferably 25 vol.%, more preferably 30 vol.%, 45 vol.%, and more preferably 40 vol.%, and is within the range of content required for a recording layer in a magnetic recording medium.

[0027] The Co-Cr-Pt oxide sputtering target of the present invention comprises (A) a composite phase in which Co, Pt, and oxides are dispersed among each other, and (B) a metallic Cr phase. In (A) the composite phase, metals (Co, Cr, Pt, etc.) or alloys and oxides are uniformly dispersed among each other, and from the viewpoint of voltage stability, it is desirable that oxides with high electrical resistance are finely dispersed. Since (B) the metallic Cr phase is a non-magnetic material, it can maintain its magnetic properties even when separated from the composite phase (A), and although the exact reason is unclear, it can reduce the voltage during sputtering, stabilize the discharge, and suppress the occurrence of arcing.

[0028] (A) The oxides included in the composite phase are preferably oxides of elements selected from one or any combination of two or more elements selected from B, Mg, Al, Si, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Ga, Ge, Y, Zr, Nb, Mo, Ta, W, La, Ce, Nd, Sm, and Gd, and it is preferable that they include at least boron oxide. Examples of preferred oxides include B2O3, SiO2, Co3O4, Cr2O3, CoO, TiO2, Ta2O5, MnO, Mn2O3, Nb2O5, ZnO, WO3, VO2, MgO, ZrO2, Al2O3, and Y2O3.

[0029] (A) The composite phase may further contain one or more elements selected from B, Al, Si, Ti, V, Mn, Fe, Ni, Cu, Zn, Ge, Nb, Mo, Ru, Rh, Pd, Ag, Ta, W, Re, Ir, and Au. The above-mentioned additive elements are preferably included as alloys with Co and Pt. In thin films formed by sputtering, the above-mentioned additive elements play a role in adjusting the magnetic strength of the magnetic particles by alloying with Co, which is a granular magnetic particle. In particular, Ru and B are effective in adjusting the magnetic moment of Co.

[0030] [Second Embodiment] The Co-Cr-Pt oxide sputtering target of the second embodiment is a Co-Cr-Pt oxide sputtering target comprising 50 at.% or more of Co, Cr exceeding 0 at.% but not exceeding 20 at.% and Pt exceeding 0 at.% but not exceeding 25 at.% and the remainder consisting of one or more oxides and unavoidable impurities, (A) A composite phase in which Co, Pt and oxides are dispersed in each other, (B) Metallic Cr phase, (C) An alloy phase containing Co or Pt, Includes, The material is characterized by containing 10 or more metallic Cr phases with an equivalent circular diameter of over 10 μm and up to 100 μm within a 1 mm × 1 mm observation field of view using a 50x magnification SEM.

[0031] The sputtering target of the second embodiment is the same as that of the first embodiment, except that it further includes an alloy phase containing (C)Co or Pt, so the same explanation as in the first embodiment will be omitted.

[0032] In the second embodiment, by including an alloy phase containing (C)Co or Pt, the melting point can often be lowered compared to the highest melting point of metallic Co or metallic Pt or other components constituting the alloy. As the melting point of the raw material powder is lowered, sinterability can be improved, resulting in a lower sintering temperature. Therefore, when sintered at the same temperature as when the alloy phase is not included, a higher density sintered body can be obtained. On the other hand, lowering the sintering temperature while maintaining high density is also effective in reducing manufacturing costs.

[0033] (C) The alloy phase containing Co or Pt is an alloy phase containing Co or Pt as the main component and does not contain oxides. The alloy phase can be one or any combination of two or more selected from a Co alloy phase containing 50 at.% or more Co, preferably 30 at.% or more, more preferably 10 at.% or more; a Pt alloy phase containing 50 at.% or more Pt, preferably 30 at.% or more, more preferably 10 at.% or more; a Co-Pt alloy phase containing 50 at.% or more Co and 50 at.% or less Pt; and a Co-Pt alloy phase containing 50 at.% or less Co and 50 at.% or more Pt. The Co alloy phase or Pt alloy phase may contain B, Cr, Si, Ti, Ru, Mn, Nb, Zn, W, V, and Ta as other components.

[0034] The sputtering target of the present invention can be manufactured by stirring and mixing Cr metal powder with an average particle size of 150 μm to 1000 μm, other raw material powders, and oxides to prepare a target mixed powder, and then sintering the target mixed powder. Alternatively, the target can be manufactured by stirring and mixing other raw material powders and oxide powders, then stirring and mixing Cr metal powder with an average particle size of 10 μm to 150 μm, preferably 20 μm or more, more preferably 25 μm or more, preferably 100 μm or less, and more preferably 50 μm or less to prepare a target mixed powder, and then sintering the target mixed powder. Although the metallic Cr phase in the sputtering target becomes almost the same size as or smaller than the Cr metal powder added through the stirring and mixing process, during the sintering process in target manufacturing, Cr metal powders may diffusely bond with each other, and there may be metallic Cr phases with a particle size larger than the Cr metal powder added.

[0035] The alloy powder may be prepared by gas atomization. Suitable alloy powders include, for example, Co-Pt alloy, Co-B alloy, Pt-B alloy, Co-Cr-Pt alloy, Co-Ru alloy, Co-Cr-Ru alloy, Co-Si alloy, Co-Cr alloy, Co-Cr-Pt-B alloy, Co-Cr-Pt-Ru alloy, and Co-Cr-Pt-Ru-B alloy.

[0036] Next, each weighed raw material powder is placed into a stirring and grinding device such as a ball mill, and stirred and mixed to uniformly mix and disperse each raw material powder to obtain a mixed powder. The stirring and mixing conditions can be adjusted as appropriate to ensure that each raw material powder is uniformly mixed and dispersed. For example, if the particle size of the raw material powder is close to the desired structure, it is preferable to suppress grinding, and a stirrer or a container-rotating type mixing device can be used without using a grinding medium. If grinding is necessary, a mixing device such as a ball mill that uses a grinding medium can be used. Furthermore, in order to form a metallic Cr phase with an equivalent circle diameter of more than 10 μm and less than or equal to 100 μm, it is preferable to divide the stirring and mixing into two or more stages, and to add metallic Cr powder with an average particle size of 10 μm to 150 μm later and stir gently. In addition, if the Cr content in the design composition of the sputtering target is high, the number of coarse metallic Cr phases present in the sputtering target can be adjusted by adding the metallic Cr powder in two or more stages.

[0037] Next, the mixed powder for the sputtering target is sintered to obtain a sintered body. The sintering conditions can be those of known methods, such as hot pressing, plasma discharge sintering (SPS), or hot isostatic pressing (HIP), as long as a high-density sintered body with a relative density of 90% or more can be obtained. The sintering temperature varies depending on the composition and properties of the mixed powder, but for Co-Cr-Pt oxide systems, it is generally between 600°C and 1200°C. The temperature can also be increased while observing the displacement in the pressurizing direction during sintering, and the temperature at which the displacement stabilizes can be defined as the sintering temperature. [Examples]

[0038] [Fabrication of sputtering targets] [Example 1] Table 1 shows the design composition of the sputtering target for Example 1: 63 at.%Co-6 at.%Cr-22 at.%Pt-2 at.%SiO2-1 at.%Co3O4-6 at.%B2O3. 50Co-50Pt alloy powder (sometimes abbreviated as "Co-50Pt alloy powder"), Co powder, Cr powder, SiO2 powder, Co3O4 powder, and B2O3 powder were weighed accordingly. The Co-50Pt alloy powder and Co powder were produced by gas atomization. The Co-50Pt alloy powder and Co powder were used after passing through a sieve with a mesh size of 106 μm. The Cr powder used had an average particle size of 35 μm after passing through a sieve with a mesh size of 45 μm.

[0039] Of the weighed powders, all except the Cr powder were placed in a ball mill pot and stirred and mixed for the first time until they were sufficiently finely dispersed. Then, the Cr powder was placed in the ball mill pot and stirred and mixed for the second time to obtain a mixed powder for sintering. In the second stirring and mixing, the input energy was reduced compared to the first stirring and mixing to prevent the Cr phase from becoming too fine. Specifically, the total rotation speed in the second stirring and mixing was set to 1 / 140 of that in the first stirring and mixing. In the stirring and mixing of Examples 2 to 25 described later, the total rotation speed in the second stirring and mixing was set to 1 / 70 or less of that in the first stirring and mixing.

[0040] The obtained mixed powder was packed into a carbon die, and a sintered body was obtained using a hot press. The sintering conditions were a vacuum atmosphere, a sintering temperature of 750°C, and a holding time of 1 hour. In order to obtain a high density of 95% or more relative density, the temperature was increased while observing the displacement in the direction of pressure during sintering, and the temperature at which the displacement stabilized was defined as the sintering temperature. The relative density of the obtained sintered body was measured by the Archimedes method, and it was confirmed that a high-density sintered body with a relative density of 99% was obtained. By performing external shaping on the sintered body, a sputtering target with a diameter of 165 mm and a thickness of 6.4 mm was fabricated. The sintering temperature for Examples 2 to 25 and Comparative Examples 1 to 19, described later, was determined using the same method, ranging from 650°C to 1200°C.

[0041] [Example 2] In Example 2, a sputtering target was prepared in the same manner as in Example 1, except that the energy input during the second stirring and mixing was increased.

[0042] [Example 3] In Example 3, the sputtering target was prepared in the same manner as in Example 1, except that the energy input during the second stirring and mixing was greater than in Example 2.

[0043] [Example 4] Of the raw material powders, the Cr powder was selected from the larger particles that passed through a sieve with a mesh size of 1000 μm but not through a sieve with a mesh size of 150 μm. All the raw material powders were placed together in a ball mill pot and stirred and mixed at once using a ball mill to obtain a mixed powder. The resulting mixed powder was then sintered in the same manner as in Example 1 to produce a sputtering target.

[0044] [Comparative Example 1] All of the same raw material powders as in Example 1 were placed together in a ball mill pot and stirred and mixed at once using a ball mill to obtain a mixed powder. The obtained mixed powder was then sintered in the same manner as in Example 1 to produce a sputtering target.

[0045] [Example 5] A sputtering target was prepared in the same manner as in Example 1, except that Pt powder, which had been classified using a sieve with a mesh size of 106 μm, was used instead of Co-50Pt alloy powder from the raw material powders.

[0046] [Comparative Example 2] A sputtering target was prepared in the same manner as in Comparative Example 1, except that Pt powder classified using a sieve with a mesh size of 106 μm was used instead of Co-50Pt alloy powder from the raw material powders.

[0047] [Examples 6-25] Each raw material powder was weighed to achieve the sputtering target design composition shown in Examples 6 to 25 of Table 1, and a sputtering target was prepared in the same manner as in Example 1. In Examples 9 and 15, Pt powder classified with a sieve with a mesh size of 106 μm was used instead of Co-50Pt alloy powder. In Example 17, Co-18.5B alloy powder was used instead of B powder. In Example 24, Co-90Pt alloy powder was used instead of Co-50Pt alloy powder. In Example 25, Co-10Pt alloy powder was used instead of Co-50Pt alloy powder.

[0048] [Comparative Examples 3-22] Each raw material powder was weighed to achieve the sputtering target design composition shown in Comparative Examples 3 to 22 of Table 1, and a sputtering target was prepared in the same manner as in Comparative Example 1. Comparative Examples 6 and 12 used Pt powder classified with a sieve with a mesh size of 106 μm instead of Co-50Pt alloy powder. Comparative Example 14 used Co-18.5B alloy powder instead of B powder. Comparative Example 21 used Co-90Pt alloy powder instead of Co-50Pt alloy powder. Comparative Example 22 used Co-10Pt alloy powder instead of Co-50Pt alloy powder.

[0049] [Tissue analysis] A sample piece for microstructural observation was cut from the obtained sputtering target, and after mirror polishing of the cross-section, the main components of each contained phase were analyzed by EDX composition mapping. The results of Example 1 are shown in Figure 2. The cross-section of the sputtering target was confirmed to consist of a composite phase in which metal and oxide are finely dispersed (gray matrix phase in Figure 2), a Co-Pt alloy phase (white phase in Figure 2), and a metallic Cr phase (black phase in Figure 2). For the metallic Cr phase, the weight ratio of the target-containing composition was quantitatively analyzed for the phase in which mainly only Cr was detected by composition mapping, and it was confirmed to consist of Cr and unavoidable impurities. Next, an image of a 1 mm × 1 mm field of view at an observation magnification of 50x was obtained using SEM, and using image analysis software, the metallic Cr phase was binarized to black and the other phases to white. Furthermore, only the 10th metallic Cr phase with the largest equivalent circle diameter was extracted, and the equivalent circle diameters of the largest metallic Cr phase and the 10th metallic Cr phase were determined. The image of Example 1 is shown in Figure 3. In Figure 3, which shows the results of Example 1, the equivalent circle diameter of the 10th largest metallic Cr phase was 37 μm, and the equivalent circle diameter of the largest metallic Cr phase was 50 μm. If fewer than 10 metallic Cr phases can be identified, measurement is not possible, and this is indicated as "-" in Table 1.

[0050] Microstructural observation of the sputtering target cross-sections revealed that no metallic Cr phase with an equivalent circular diameter of more than 10 μm and less than or equal to 100 μm could be confirmed in Comparative Examples 1 to 22. As representative examples, Figure 4 shows the microstructural image of the target cross-section of Comparative Example 1, and Figure 5 shows the microstructural image of the target cross-section of Comparative Example 2.

[0051] In Examples 5, 9, and 15, the Co-Pt alloy phase could not be identified, and only (A) a composite phase consisting of Co, Pt, and oxides, and (B) a metallic Cr phase were observed. The equivalent circle diameter of the 10th largest metallic Cr phase exceeded 10 μm, while the equivalent circle diameter of the largest metallic Cr phase was 100 μm or less. As a representative example, a microstructure photograph of the target cross-section in Example 5 is shown in Figure 6.

[0052] In Examples 1-4, 6-8, 10-14, and 16-25, (A) a composite phase consisting of Co, Pt, and oxides, (B) a metallic Cr phase, and (C) a Co-Pt alloy phase were identified. The equivalent circle diameter of the 10th largest metallic Cr phase exceeded 10 μm, while the equivalent circle diameter of the largest metallic Cr phase was 100 μm or less.

[0053] [Leakage magnetic flux density] The leakage flux density (PTF) of the obtained sputtering targets was measured according to ASTM F2086-01. For evaluation of the leakage flux density, the leakage flux density measured with a sputtering target of the same composition but without the metallic Cr phase (comparative example) was used as a baseline. A decrease of less than -2% or exceeding the baseline was considered good, and this is indicated by "〇" in Table 1. In Examples 1 to 25, it was confirmed that the PTF was equivalent to or improved compared to the corresponding comparative example of the same composition.

[0054] [Sputter discharge voltage] The obtained sputtering target was mounted on a magnetron sputtering apparatus, and while argon gas was flowed to maintain an argon gas pressure of 1.0 Pa, the sputter discharge voltage was measured using a data logger while continuing sputter discharge with an input power of 1000 W. The data logger was set to measure 15,000 data points with a sampling period of 2 μs, repeated 100 times. The average of the data from each measurement was calculated, and then this average was averaged over 100 measurements to calculate the sputter discharge voltage value under those measurement conditions. Discharge stability was judged to have improved if the sputter discharge voltage value was reduced by 20 V or more compared to the sputtering target (comparative example) with the same composition but without the metallic Cr phase. In Examples 1 to 25, it was confirmed that the discharge voltage difference compared to the corresponding comparative example of the same composition was 20 V or more lower.

[0055] [Relative density] In all examples and comparative examples, the relative density of the sputtering target was 95%. That was all.

[0056] Table 1

Claims

1. A Co-Cr-Pt-oxide sputtering target comprising 50 at.% or more of Co, Cr exceeding 0 at.% but 20 at.% or less, and Pt exceeding 0 at.% but 25 at.% or less, with the remainder being one or more oxides and unavoidable impurities, (A) A composite phase in which Co, Pt and oxides are dispersed among each other, (B) Metallic Cr phase and, A sputtering target characterized by containing 10 or more metallic Cr phases with an equivalent circular diameter of over 10 μm and up to 100 μm within a 1 mm x 1 mm observation field of view using a SEM with an observation magnification of 50x.

2. A Co-Cr-Pt-oxide sputtering target comprising 50 at.% or more of Co, Cr exceeding 0 at.% but 20 at.% or less, and Pt exceeding 0 at.% but 25 at.% or less, with the remainder being one or more oxides and unavoidable impurities, (A) A composite phase in which Co, Pt and oxides are dispersed among each other, (B) Metallic Cr phase, (C) Alloy phase containing Co or Pt, Includes, A sputtering target characterized by containing 10 or more metallic Cr phases with an equivalent circular diameter of over 10 μm and up to 100 μm within a 1 mm x 1 mm observation field of view using a SEM with an observation magnification of 50x.

3. The sputtering target according to claim 1 or 2, characterized in that the composite phase further comprises one or more selected from B, Al, Si, Ti, V, Mn, Fe, Ni, Cu, Zn, Ge, Nb, Mo, Ru, Rh, Pd, Ag, Ta, W, Re, Ir, and Au.

4. The sputtering target according to claim 1 or 2, characterized in that the oxide is contained in the sputtering target in an amount of 20 vol.% or more and 50 vol.% or less.

5. The sputtering target according to claim 1 or 2, characterized in that the oxide is an oxide of an element selected from one or any combination of two or more elements selected from B, Mg, Al, Si, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Ga, Ge, Y, Zr, Nb, Mo, Ta, W, La, Ce, Nd, Sm, and Gd.

6. The sputtering target according to claim 1 or 2, characterized in that the oxide includes at least a boron oxide.

7. The composite phase further comprises one or more selected from B, Al, Si, Ti, V, Mn, Fe, Ni, Cu, Zn, Ge, Nb, Mo, Ru, Rh, Pd, Ag, Ta, W, Re, Ir, and Au, and The sputtering target according to claim 1 or 2, characterized in that the oxide comprises at least a boron oxide and is further an oxide of an element selected from one or any combination of two or more elements selected from Mg, Al, Si, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Ga, Ge, Y, Zr, Nb, Mo, Ta, W, La, Ce, Nd, Sm, and Gd.

8. A method for manufacturing a sputtering target according to claim 1 or 2, A target mixed powder is prepared by mixing and stirring raw material powders, including Cr metal powder and oxide powder with an average particle size of 150 μm to 1000 μm. A method for manufacturing a sputtering target, characterized by sintering the mixed powder for the target.

9. A method for manufacturing a sputtering target according to claim 1 or 2, A target mixed powder is prepared by adding Cr metal powder with an average particle size of 10 μm to 150 μm to a pre-mixed and stirred mixture of other raw material powders and oxide powders. A method for manufacturing a sputtering target, characterized by sintering the mixed powder for the target.

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