Co-Cr-Pt-B ferromagnetic sputtering target

Abstract

This invention provides a ferromagnetic sputtering target that enables stable discharge without discharge abnormalities using the magnetron sputtering method. [Solution] A Co-Cr-Pt-B ferromagnetic sputtering target comprising: a Co-Cr-Pt-B alloy phase (A) containing 0.7 at% to 30 at% of B; and an alloy phase (B) which is one of Co-B alloy, Co-Cr-B alloy, or Co-Pt-B alloy, containing 5 at% to 20 at% of B, with B distributed throughout without uneven distribution of B aggregated phase; alloy phase (A) occupying 50 vol% or more of the sputtering target; alloy phase (B) occupying less than 50 vol% of the sputtering target; the sum of alloy phase (A) and alloy phase (B) being 100 vol%; and a sputtering discharge voltage of 330 V or less measured at 500 W.

Description

Technical Field

[0001] The present invention relates to a sputtering target used for forming a magnetic film of a magnetic recording medium, particularly a magnetic recording layer of a hard disk drive adopting a perpendicular magnetic recording method, and relates to a sputtering target capable of obtaining stable discharge at a lower voltage when sputtering with a magnetron sputtering apparatus.

Background Art

[0002] In the field of magnetic recording typified by hard disk drives, as a material for a magnetic thin film responsible for recording, a material system based on ferromagnetic metals such as Co, Fe, or Ni is used. In particular, for the magnetic recording layer of current hard disk drives, Co-Pt-based, Co-Cr-Pt-based, or a composition system obtained by adding non-magnetic inorganic substances to them is used.

[0003] For the production of the magnetic recording layer of this hard disk drive, mainly due to its high productivity, a sputtering method, particularly a magnetron sputtering method, is often used. As a method for producing a target material essential when using the sputtering method, it is common to use a melting method or a powder metallurgy method. Which one to use is determined by the characteristics of the required target and thin film.

[0004] Sputtering is a method of film formation in which a negative voltage is applied to a target material under an inert gas atmosphere, causing the atoms constituting the target to be deposited onto a substrate. Applying a negative voltage promotes the ionization of the inert gas, and the positively charged inert gas is attracted to the target, colliding with it and knocking out the atoms that make up the target. These atoms then adhere to the substrate surface, resulting in film formation on the substrate. Magnetron sputtering is a method of sputtering in which a magnet is placed on the back of the target, and the magnetic field generated on the target surface promotes the ionization of the plasma gas, thereby improving the efficiency of sputtering. In the field of magnetic recording, exemplified by current hard disk drives, magnetron sputtering is often used due to its film formation speed, target yield, and sputtering stability.

[0005] However, the targets used for magnetic recording layer deposition are primarily ferromagnetic materials, which hinder the transmission of magnetic flux from the magnets placed on the back surface. If the transmission of magnetic flux is hindered too much, the advantages of using the magnetron sputtering method described above are lost, leading to a decrease in target yield and instability of the sputter discharge. Therefore, targets used in the magnetron sputtering method are required to have as high a leakage magnetic flux density as possible.

[0006] Various methods have been proposed to improve the leakage magnetic flux density of a target. For example, Japanese Patent Publication No. 4673453 describes a ferromagnetic sputtering target characterized by a structure having a metal substrate (A) and a spherical phase (B) in the metal substrate (A) with a major axis difference of 0 to 50% and a diameter of 30 to 150 μm, in which 90 mol% or more of Co is contained, wherein the metal has a composition of Cr of 20 mol% or less and the remainder being Co, and a ferromagnetic sputtering target made of a metal has a composition of Cr of 20 mol% or less, Pt of 5 mol% to 30 mol%, and the remainder being Co. Specifically, it has been reported that in ferromagnetic sputtering targets having the compositions 78Co-12Cr-5TiO2-5SiO2, 65Co-13Cr-15Pt-5TiO2-2Cr2O3, 85Co-15Cr, and 70Co-15Cr-15Pt, those with a structure containing spherical Co phase (B) have a higher average leakage flux than those without spherical Co phase (B).

[0007] Japanese Patent Publication No. 4758522 describes a ferromagnetic sputtering target characterized by a structure having a metal substrate (A) and a flattened phase (B) containing 90 wt% or more of Co within the metal substrate (A), with an average particle size of phase (B) of 10 μm to 150 μm and an average aspect ratio of 1:2 to 1:10, wherein the target is mainly composed of a metal with a composition of 20 mol% or less of Cr and the remainder being Co, and a sputtering target is mainly composed of a metal with a composition of 20 mol% or less of Cr, 5 mol% to 30 mol% of Pt and the remainder being Co. Specifically, it is described that a ferromagnetic sputtering target having a composition of 78.73Co-13.07Cr-8.2SiO2 and a structure containing a flattened Co phase (B) has a lower average leakage magnetic flux density than one made using Co atomized powder (spherical), but is higher than conventional ones (details unknown).

[0008] Japanese Patent Publication No. 5394576 describes a ferromagnetic sputtering target characterized by a structure having a metal substrate (A), a Co-Pt alloy phase (B) containing 40 to 76 mol% of Pt within the metal substrate (A), and a Co alloy phase (C) containing 90 mol% or more of Co different from the Co-Pt alloy phase (B), wherein the sputtering target is made of a metal with a composition of 20 mol% or less of Cr, 5 mol% or more of Pt, and the remainder being Co. Specifically, it has been reported that in ferromagnetic sputtering targets having the compositions 88(Co-5Cr-15Pt)-5CoO-7SiO2 and 59Co-6Cr-20Pt-5Ru-4TiO2-4SiO2-2Cr2O3, those with a structure containing a Co-Pt alloy phase (B) with a particle size of 50-150 μm and 50 mol% Pt, and a pure Co phase (C) with a particle size of 70-150 μm, have a higher average leakage magnetic flux density than those with a structure that does not contain the Co-Pt alloy phase (B) and Co alloy phase (C), and those with a structure containing a Co-Pt alloy phase (B) with a particle size of 50-150 μm and 81 mol% Pt, and a pure Co phase (C) with a particle size of 70-150 μm. When B is included as an additive element in an amount of 0.5 mol% to 10 mol%, it is stated that B is present in the metal substrate (A) and may slightly diffuse into the Co-Pt alloy phase (B) or Co phase (C) via the interface between the Co-Pt alloy phase (B) and the metal substrate (A) or the interface between the Co phase (C) and the metal substrate (A). In other words, B may be present near the interface between the Co-Pt alloy phase (B) or Co phase (C) and the metal substrate (A), but it is not distributed throughout the entire Co-Pt alloy phase (B) or Co phase (C).

[0009] All of the aforementioned prior art documents disclose that the leakage magnetic flux density of a ferromagnetic sputtering target can be increased by creating a structure in which a Co alloy phase containing 90 mol% or more of large spherical Co particles with a particle size of 10 μm to 150 μm exists within the metal substrate (A). Although it is stated that B may be included as an additive element, there are no examples containing B, and it is unclear whether the desired effect can be obtained in a Co-Cr-Pt-B sputtering target. Furthermore, there is neither disclosure nor suggestion of controlling the distribution state of B, and since B usually aggregates and is unevenly distributed, a person skilled in the art would not understand that the disclosure indicates that B is distributed throughout.

[0010] In Co-Cr-Pt-B sputtering targets that do not contain oxides, the density of the B aggregated phase in the metal substrate becomes high, and due to the brittleness of B, microcracks are generated. The problem is that arcing occurs starting from these microcracks. When discharge abnormalities occur due to arcing, sputtering cannot be performed stably, and the yield is drastically reduced.

[0011] As a method for suppressing arcing in Co-Cr-Pt-B sputtering targets, Japanese Patent Publication No. 2015-61946 describes adjusting the structure of an ingot made of a Co-Cr-Pt-B alloy by controlling a precise rolling or forging process and heat treatment to obtain a fine and uniform rolled structure without microcracks. Figure 1 of the said publication shows an SEM image of the structure of a sputtering target, which consists of two phases: a matrix phase and a B-rich phase, and the B-rich phase is shaped like ciliary clouds. As can be seen by comparing it with the SEM images of the examples described later, in the sputtering target of the present invention, B is distributed throughout the entire alloy phase, whereas in Figure 1 of the said publication, B is aggregated and unevenly distributed in the B-rich phase. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Patent No. 4673453 [Patent Document 2] Patent No. 4758522 [Patent Document 3] Patent No. 5394576 [Patent Document 4] Japanese Patent Publication No. 2015-61946 [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] The present invention aims to provide a ferromagnetic sputtering target that can obtain a stable discharge without discharge abnormalities in the magnetron sputtering method. In particular, the present invention aims to provide a Co-Cr-Pt-B ferromagnetic sputtering target and a method for manufacturing the same, which have a high leakage magnetic flux density and can reduce the discharge voltage during sputtering. [Means for solving the problem]

[0014] The inventors of the present invention have discovered that in a Co-Cr-Pt-B ferromagnetic sputtering target, by controlling the distribution of B in both the Co-Cr-Pt alloy phase and the Co or Co-Cr alloy phase so that the B aggregated phase is not unevenly distributed, that is, by creating a structure that includes a Co-Cr-Pt-B alloy phase (A) and an alloy phase (B) which is either a Co-B alloy or a Co-Cr-B alloy, the leakage magnetic flux density can be improved and the discharge voltage can be reduced, and have completed the present invention.

[0015] According to the present invention, a Co-Cr-Pt-B ferromagnetic sputtering target and a method for manufacturing the same are provided in the following embodiments. [1] A Co-Cr-Pt-B ferromagnetic sputtering target, A Co-Cr-Pt-B alloy phase (A) containing 0.7 at% to 30 at% of B, A Co-B alloy, Co-Cr-B alloy, or Co-Pt-B alloy, comprising an alloy phase (B) containing 5 at% to 20 at% of B, where B is distributed throughout without uneven distribution of the B aggregated phase. The alloy phase (A) accounts for 50 vol% or more of the sputtering target, the alloy phase (B) accounts for less than 50 vol%, and the sum of the alloy phases (A) and (B) is 100 vol%. A Co-Cr-Pt-B ferromagnetic sputtering target characterized by a sputter discharge voltage of 330V or less, as measured at 500W. [2] A Co-Cr-Pt-B ferromagnetic sputtering target according to [1], characterized in that it contains Cr exceeding 0 at% but not exceeding 30 at%, Pt between 5 at% and 30 at%, B between 5 at% and 25 at%, and the remainder being Co and unavoidable impurities. [3] The Co-Cr-Pt-B ferromagnetic sputtering target according to [1] or [2], characterized in that the alloy phase (A) further contains, as additive elements, one or more elements selected from Al, Si, Sc, Ti, V, Mn, Fe, Ni, Cu, Zn, Ge, Y, Zr, Nb, Ta, Mo, W, Ru, Ag, Sn, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Hf in an amount of more than 0 at% and less than 25 at%. A method for manufacturing a Co-Cr-Pt-B ferromagnetic sputtering target according to any one of [1] to [3], Co-Cr-Pt-B alloy powder containing more than 0.7 at% and less than or equal to 30 at% of B, A mixing step to obtain a mixed powder by weakly mixing one of the following: Co-B alloy powder, Co-Cr-B alloy powder, or Co-Pt-B alloy powder containing 5 at% to 20 at% of B; A sintering step in which the mixed powder is sintered to obtain a sintered body, A manufacturing method characterized by including the following. [5] The manufacturing method according to [4], characterized in that the Co-Cr-Pt-B alloy powder and the Co-B alloy powder, Co-Cr-B alloy powder or Co-Pt-B alloy powder are atomized alloy powders. [6] The manufacturing method according to [4] or [5], characterized in that the sintering step involves holding the mixed powder at a pressure of 10 MPa or more and 100 MPa or less, and at a temperature of 700°C or more and 1300°C or less, for 30 minutes or more and 3 hours or less.

Advantages of the Invention

[0016] The Co-Cr-Pt-B ferromagnetic sputtering target of the present invention contains B in an amount exceeding 0 at% and not exceeding 30 at%, and consists of a Co-Cr-Pt-B alloy phase (A) in which B is distributed throughout, and an alloy phase (B) which is either a Co-B alloy, a Co-Cr-B alloy or a Co-Pt-B alloy, contains B in an amount exceeding 0 at% and not exceeding 20 at%, and in which B is distributed throughout. Since there is no uneven distribution of the B agglomeration phase and B is distributed throughout the target, the discharge voltage during sputtering can be reduced, abnormal discharges such as arcing caused by excessive voltage can be suppressed, and the leakage magnetic flux density is high.

[0017] According to the manufacturing method of the present invention, a Co-Cr-Pt-B ferromagnetic sputtering target can be obtained which consists of a Co-Cr-Pt-B alloy phase (A) containing B in an amount exceeding 0 at% and not exceeding 30 at% and in which B is distributed throughout, and an alloy phase (B) which is either a Co-B alloy, a Co-Cr-B alloy or a Co-Pt-B alloy, contains B in an amount exceeding 0 at% and not exceeding 20 at%, and in which B is distributed throughout. There is no uneven distribution of the B agglomeration phase, B is distributed throughout the target, the leakage magnetic flux density is high, and the discharge voltage during sputtering can be reduced.

Brief Description of the Drawings

[0018] [Figure 1] Graph showing the relationship between input power and voltage values for Examples 1 to 3 and Comparative Examples 1 to 4. [Figure 2] SEM observation image of Example 1. [Figure 3] SEM observation image of Example 2. [Figure 4] SEM observation image of Example 3. [Figure 5] SEM observation image of Comparative Example 1. [Figure 6] SEM observation image of Comparative Example 2. [Figure 7] SEM observation image of Comparative Example 3. [Figure 8]EPMA-WDX mapping image of Example 1. [Figure 9] EPMA-WDX mapping image of Example 2. [Figure 10] EPMA-WDX mapping image of Example 3. [Figure 11] EPMA-WDX mapping image of Comparative Example 1. [Figure 12] EPMA-WDX mapping image of Comparative Example 2. [Figure 13] EPMA-WDX mapping image of Comparative Example 3. Preferred Embodiment

[0019] The present invention provides a ferromagnetic sputtering target that has a high leakage magnetic flux density and can reduce the discharge voltage during sputtering.

[0020] The Co-Cr-Pt-B ferromagnetic sputtering target of the present invention comprises a Co-Cr-Pt-B alloy phase (A) containing more than 0 at% but less than 30 at% of B, with B distributed throughout without uneven distribution of B aggregated phases, and an alloy phase (B) which is one of Co-B alloy, Co-Cr-B alloy, or Co-Pt-B alloy, containing more than 0 at% but less than 20 at% of B, with B distributed throughout without uneven distribution of B aggregated phases, wherein the alloy phase (A) accounts for 50 vol% or more of the sputtering target, and the alloy phase (B) accounts for less than 50 vol% of the sputtering target.

[0021] The Co-Cr-Pt-B ferromagnetic sputtering target of the present invention has an alloy phase (A) that is greater than the alloy phase (B), with alloy phase (A) accounting for 50 vol% or more, preferably 60 vol% or more, and more preferably 65 vol% or more, and alloy phase (B) accounting for less than 50 vol%, preferably less than 40 vol%, and more preferably less than 35 vol%. The Co-Cr-Pt-B ferromagnetic sputtering target of the present invention consists of two phases, alloy phase (A) and alloy phase (B), and does not contain other phases such as oxide phases.

[0022] The alloy phase (A) contains B in an amount greater than 0 at% but less than or equal to 30 at% and preferably between 3 at% and 26 at%. The phase (B) contains B in an amount greater than 0 at% but less than or equal to 20 at% and preferably between 3 at% and 18.5 at%.

[0023] The statement "B is distributed throughout" in alloy phase (B) refers to the observation surface at 1000x magnification with an acceleration voltage of 20kV and an irradiation current of 8×10⁻¹⁰. -5 A means that in an EPMA-WDX mapping image with a beam diameter of 10 μm and an observation magnification of 200x, there are no areas within any given 10 μm × 10 μm region where B is not present.

[0024] Furthermore, it is preferable that B is distributed throughout the alloy phase (A). Here, "B is distributed throughout the alloy phase (A)" means that the SEM observation surface is at 1000x magnification, the acceleration voltage is 20kV, and the irradiation current is 8×10⁻¹⁰. -5 A means that in an EPMA-WDX mapping image with a beam diameter of 10 μm and an observation magnification of 200x, there are no areas within any given 10 μm × 10 μm region where B is not present.

[0025] The Co-Cr-Pt-B ferromagnetic sputtering target of the present invention preferably has a composition in which Cr is greater than 0 at% but less than or equal to 30 at%, Pt is greater than 5 at% but less than or equal to 30 at%, B is greater than 0 at% but less than or equal to 25 at%, and the remainder is Co and unavoidable impurities. In particular, it is preferable to have a composition in which Cr is greater than or equal to 3 at% but less than or equal to 25 at%, Pt is greater than or equal to 10 at% but less than or equal to 25 at%, B is greater than or equal to 3 at% but less than or equal to 20 at%, and the remainder is Co and unavoidable impurities.

[0026] The alloy phase (A) may further contain, as additive elements, one or more elements selected from Al, Si, Sc, Ti, V, Mn, Fe, Ni, Cu, Zn, Ge, Y, Zr, Nb, Te, Mo, W, Ru, Ag, Sn, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Hf in an amount exceeding 0 at% and 25 at% or less, preferably 1 at% to 15 at%.

[0027] In this invention, the average composition of alloy phase (A) and alloy phase (B) is measured by the following method. A cross section perpendicular to the sputtering target is cut out and polished sequentially using abrasive paper with grits from P80 to P1200, and finally a polished surface is obtained by buffing with diamond abrasive grains with a particle size of 1 μm. The polished surface is observed using EPMA. The EPMA observation conditions are as follows: using a JEOL JXA-8500F as the apparatus, acceleration voltage 20 kV, irradiation current 8 × 10⁻¹⁰ -5 A beam diameter of 10 μm, observation magnification of 200x, and 128 × 128 pixels are used to acquire elemental mapping images. During observation, quantitative analysis mode is used, with metal selected as the measurement material and the ZAF method as the correction method. In the obtained elemental mapping image, if a phase in which all of the main components Co, Cr, Pt, and B are detected (corresponding to alloy phase (A)) and a phase in which Cr or Pt is not detected or is at an extremely low concentration compared to Cr or Pt in alloy phase (A) (corresponding to alloy phase (B)) are identified, a location large enough to accommodate a perfect circle with a diameter of 50 μm is selected for each, and the composition at its centroid point is measured. The above observation is performed for three fields of view, three locations each for alloy phase (A) and alloy phase (B), and the average is taken as the average composition of alloy phase (A) and alloy phase (B), respectively.

[0028] In this invention, the volume ratio of alloy phase (A) and alloy phase (B) is measured by the following method. First, a mass concentration map for each element is obtained using EPMA by the method described above. Using the obtained mass concentration map, horizontal line analysis is performed from edge to edge of the image for elements not detected in alloy phase (B) (for example, Cr or Pt in the case of Co-B, and Pt in the case of Co-Cr-B). When performing line analysis, lines are selected that include areas other than the boundary between alloy phase (A) and alloy phase (B), i.e., areas containing only alloy phase (A) and areas containing only alloy phase (B), from among the phases corresponding to alloy phase (A) and alloy phase (B), respectively. The map is binarized using the average of the maximum and minimum values ​​of the profile obtained by line analysis as a threshold. Here, the range above this threshold is defined as alloy phase (A), and the range below the threshold is defined as alloy phase (B). The area ratio of alloy phase (A) and alloy phase (B) is determined by analyzing the obtained binarized image using particle analysis in ImageJ. Perform the above procedure for three fields of view, and the average value is taken as the area ratio of the sample. This area ratio directly corresponds to the volume ratio of each phase. While Pt is generally used as the element for line analysis of the mass concentration map, Cr is used when Pt is present in all phases.

[0029] The Co-Cr-Pt-B ferromagnetic sputtering target of the present invention can be manufactured by powder metallurgy. The manufacturing method of the present invention includes the steps of: weakly mixing a Co-Cr-Pt-B alloy powder containing more than 0 at% but less than or equal to 30 at% of B with one of Co-B alloy powder, Co-Cr-B alloy powder, or Co-Pt-B alloy powder containing more than 0 at% but less than or equal to 20 at% of B to obtain a mixed powder; and sintering the mixed powder to obtain a sintered body.

[0030] The Co-Cr-Pt-B alloy powder and the Co-B alloy powder, Co-Cr-B alloy powder, or Co-Pt-B alloy powder can be atomized alloy powder, chemically produced powder, or powder produced by other methods, but atomized alloy powder is preferred.

[0031] Weak mixing means that instead of applying a large amount of mixing and stirring energy to pulverize each raw material powder, the Co-Cr-Pt-B alloy powder constituting alloy phase (A) and the Co-B alloy powder, Co-Cr-B alloy powder, or Co-Pt-B alloy powder constituting alloy phase (B) are gently mixed without pulverizing each alloy powder, while preserving them. In the manufacturing method of the present invention, weak mixing is preferably performed using a ball mill with a low rotation speed and for a short time, for example, a rotation speed of 30 rpm to 100 rpm for 10 minutes to 1 hour, and is particularly preferably performed using a shaker or mixer that does not use stirring balls and only oscillates up and down and left and right.

[0032] Sintering can be performed in a vacuum atmosphere with a sintering pressure of 10 MPa to 100 MPa, a sintering temperature of 700°C to 1300°C, a holding time of 30 minutes to 3 hours, preferably with a sintering pressure of 20 MPa to 80 MPa, a sintering temperature of 800°C to 1100°C, and a holding time of 30 minutes to 2 hours. If the sintering pressure is too low, the density of the sintered body decreases. If the sintering temperature is too low, the density of the sintered body decreases, while if the sintering temperature is too high, B aggregates too much, forming a coarse B aggregated phase as seen in conventional techniques, and B tends to be unevenly distributed rather than evenly distributed throughout the target. If the sintering holding time is too short, the density of the sintered body decreases, while if the sintering holding time is too long, B aggregates too much, forming a coarse B aggregated phase as seen in conventional techniques, and B tends to be unevenly distributed rather than evenly distributed throughout the target. A decrease in density causes particles to be generated from the target during sputter discharge. On the other hand, uneven distribution of the coarse B aggregated phase causes discharge defects, including arcing. [Examples]

[0033] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0034] Examples 1 to 23 involved weighing atomized alloy powder, the raw material constituting alloy phase (A) as shown in Table 1, and atomized alloy powder, the raw material constituting the second phase (meaning alloy phase (B) in these examples; the same applies hereinafter), so that the second phase content and the remainder would be alloy phase (A) content, as shown in Table 1, to achieve the target compositions shown in Table 1. The mixture was then mixed using a shaker at 15-100 rpm for 15 minutes. The resulting mixed powder was packed into a carbon die and sintered by vacuum hot pressing under vacuum conditions of 30 MPa pressure, 800°C-1100°C temperature, and a holding time of 1 hour. The sintering temperature varied depending on the target composition, but was set to achieve a density of 97% or higher for all samples. The obtained sintered bodies were cut and ground using a surface grinder and a lathe to produce disc-shaped sputtering targets with a diameter of 165 mm and a thickness of 6.4 mm.

[0035] The obtained disc-shaped sputtering target was mounted on a magnetron sputtering apparatus, and while argon gas was flowed to maintain an argon gas pressure of 4.0 Pa, the sputter discharge voltage was measured using a data logger while continuing the sputter discharge at an arbitrary input power. 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 run was calculated, and then this average was averaged over 100 runs to calculate the sputter discharge voltage value under those measurement conditions. The results are shown in Table 1.

[0036] [Table 1]

[0037] Comparative Examples 1, 5, 7, 9, 11, and 13 were prepared in the same manner as the Examples, except that mixed powders were prepared by mixing each metal powder instead of using alloy atomized powders.

[0038] Comparative Examples 2 and 3 were prepared in the same manner as the Examples, except that atomized alloy powder without B was used as the raw material powder constituting the second phase.

[0039] Comparative Examples 4, 6, 8, 10, 12, and 14 were prepared in the same manner as the Examples, except that Co metal powder was used as the raw material powder constituting the second phase.

[0040] Table 2 and Figure 1 show the results of measuring the sputter discharge voltage for sputtering targets of Examples 1-3 and Comparative Examples 1-4, which have the same composition Co-15Cr-10Pt-10B, while varying the input power from 100W to 1000W in 100W increments.

[0041] [Table 2]

[0042] Table 2 shows the measured values ​​of PTF (leakage magnetic flux density). PTF measurements were performed according to ASTM F2086-01. The PTF of the sputtering targets in Examples 1 and 2 was higher than that of the sputtering targets in Comparative Examples 1 and 2, and was equivalent to that of the sputtering target in Comparative Example 3. The PTF of the sputtering target in Example 3 was higher than that of any of the sputtering targets in Comparative Examples 1 to 4, confirming that an improvement in leakage magnetic flux density can also be achieved.

[0043] From Figure 1, when the sputter discharge voltages are arranged in descending order, we see Comparative Example 4, which was made using Co metal powder as the second phase; Comparative Example 1, which was made using individual metal powders instead of alloy atomized powder; and Comparative Examples 3 and 2, which were made using atomized alloy powder that did not contain B as the second phase. It can be seen that the sputter discharge voltage of Examples 1-3, in which B is distributed throughout both alloy phase (A) and alloy phase (B), is significantly lower than that of Comparative Examples 1-4. In particular, the decrease in sputter discharge voltage becomes larger when the input power increases to 300W or more. Furthermore, from Table 1, when comparing the sputter discharge voltage at an input power of 500W, the Examples have a low value of 330V or less, while the Comparative Examples have a high value exceeding 330V.

[0044] SEM images (15.0V × 1,000) of the sputtering targets for Examples 1-3 and Comparative Examples 1-3 are shown in Figures 2-7, and EPMA-WDX mapping images (15.0V × 2,000) of the sputtering targets for Examples 1-3 and Comparative Examples 1-3 are shown in Figures 8-13.

[0045] From the EPMA-WDX mapping image in Figure 8, it can be seen that in the sputtering target of Example 1, the white area at the bottom of the CP image is a Co-Cr-Pt-B alloy phase (A) containing Co, Cr, Pt, and B, and the gray area at the top of the CP image is a Co-Pt-B alloy phase (B) containing Co, Pt, and B. From Figures 2 and 8, it can be seen that the sputtering target of Example 1 consists of a Co-Cr-Pt-B alloy phase (A) and a Co-Pt-B alloy phase (B), and that in both alloy phases (A) and (B), there are no areas where B is not present in any arbitrary 10 μm × 10 μm region, and B is distributed throughout alloy phase (A) and alloy phase (B). Furthermore, B within alloy phase (A) is distributed finely and uniformly throughout, and B within alloy phase (B) is aggregated compared to B within alloy phase (A), but is still distributed throughout alloy phase (B).

[0046] From the EPMA-WDX mapping image in Figure 9, it can be seen that in the sputtering target of Example 2, the white area on the right in the CP image is the Co-Cr-Pt-B alloy phase (A) containing Co, Cr, Pt, and B, and the gray area on the left in the CP image is the Co-Cr-B alloy phase (B) containing Co, Cr, and B. From Figures 3 and 9, it can be seen that the sputtering target of Example 2 consists of a Co-Cr-Pt-B alloy phase (A) and a Co-Cr-B alloy phase (B), and that in both alloy phases (A) and (B), there are no areas where B is not present in any arbitrary 10 μm × 10 μm region, indicating that B is distributed throughout both alloy phase (A) and alloy phase (B), and that B within alloy phase (A) is finely and uniformly distributed throughout, while B within alloy phase (B) is more aggregated compared to B within alloy phase (A), but is still distributed throughout alloy phase (B).

[0047] From the EPMA-WDX mapping image in Figure 10, it can be seen that in the sputtering target of Example 3, the white area in the upper part of the CP image is a Co-Cr-Pt-B alloy phase (A) containing Co, Cr, Pt, and B, and the gray area in the lower part of the CP image is a Co-B alloy phase (B) containing Co and B. From Figures 4 and 10, it can be seen that the sputtering target of Example 3 consists of a Co-Cr-Pt-B alloy phase (A) and a Co-B alloy phase (B), and that in both alloy phases (A) and (B), there are no areas where B is not present in any arbitrary 10 μm × 10 μm region, and B is distributed throughout both alloy phase (A) and alloy phase (B). Furthermore, B within alloy phase (A) is distributed throughout, and B within alloy phase (B) is aggregated compared to B within alloy phase (A), but is still distributed throughout alloy phase (B).

[0048] Figures 5 and 11 show that the sputtering target of Comparative Example 1 is a single phase in which Co, Cr, Pt, and B are dispersed throughout, and does not have an alloy phase (B).

[0049] From the EPMA-WDX mapping image in Figure 12, it can be seen that in the sputtering target of Comparative Example 2, the gray area on the right in the CP image is a Co-Pt phase containing Co and Pt but not B, and the area on the left in the CP image where black dots are present is a Co-Cr-Pt-B phase (A) containing Co, Cr, Pt, and B. From Figures 6 and 12, it can be seen that the sputtering target of Comparative Example 2 consists of a Co-Cr-Pt-B phase (A) and a Co-Pt phase (second phase), and that the Co-Pt phase does not contain B and does not have an alloy phase (B) containing B.

[0050] From the EPMA-WDX mapping image in Figure 13, it can be seen that in the sputtering target of Comparative Example 3, the white area in the lower right of the CP image is the Co-Cr-Pt-B phase (A) containing Co, Cr, Pt, and B, the gray area in the upper left of the CP image is the Co-Pt phase containing Co and a small amount of Pt, and the large black area within the same gray area is the aggregated phase of coarse B unevenly distributed around Co. From Figures 7 and 13, it can be seen that the sputtering target of Comparative Example 3 consists of a Co-Cr-Pt-B phase (A) and a Co-Pt phase (second phase), with B unevenly distributed around the Co-Pt phase, and there is a 10 μm × 10 μm area within the second phase where B is absent, indicating that it does not have an alloy phase (B) in which B is distributed throughout.

[0051] [Other forms] [1] A Co-Cr-Pt-B ferromagnetic sputtering target, A Co-Cr-Pt-B alloy phase (A) contains more than 0 at% but less than or equal to 30 at% of B, and B is distributed throughout without the B aggregated phase being unevenly distributed. A Co-B alloy, Co-Cr-B alloy, or Co-Pt-B alloy, comprising an alloy phase (B) containing more than 0 at% but less than or equal to 20 at% of B, and in which B is distributed throughout without the B aggregated phase being unevenly distributed. A Co-Cr-Pt-B ferromagnetic sputtering target characterized in that the alloy phase (A) accounts for 50 vol% or more of the sputtering target, and the alloy phase (B) accounts for less than 50 vol% of the sputtering target. [2] The Co-Cr-Pt-B ferromagnetic sputtering target described in [1] above, characterized in that Cr is greater than 0 at% but less than 30 at%, Pt is between 5 at% and 30 at%, B is greater than 0 at% but less than 25 at%, and the remainder is Co and unavoidable impurities. [3] The Co-Cr-Pt-B ferromagnetic sputtering target according to [1] or [2] above, characterized in that the alloy phase (A) further contains, as additive elements, one or more elements selected from Al, Si, Sc, Ti, V, Mn, Fe, Ni, Cu, Zn, Ge, Y, Zr, Nb, Ta, Mo, W, Ru, Ag, Sn, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Hf in an amount of more than 0 at% and less than 25 at%. [4] A method for manufacturing a Co-Cr-Pt-B ferromagnetic sputtering target according to any one of [1] to [3] above, Co-Cr-Pt-B alloy powder containing more than 0 at% and 30 at% or less of B, A mixing step to obtain a mixed powder by weakly mixing one of the following: Co-B alloy powder, Co-Cr-B alloy powder, or Co-Pt-B alloy powder containing more than 0 at% but less than or equal to 20 at% of B; A sintering step in which the mixed powder is sintered to obtain a sintered body, A manufacturing method characterized by including the following. [5] The manufacturing method according to [4] above, characterized in that the Co-Cr-Pt-B alloy powder and the Co-B alloy powder, Co-Cr-B alloy powder or Co-Pt-B alloy powder are atomized alloy powders. [6] The manufacturing method according to [4] or [5] above, characterized in that the sintering step involves holding the mixed powder at a pressure of 10 MPa or more and 100 MPa or less, and at a temperature of 700°C or more and 1300°C or less, for 30 minutes or more and 3 hours or less.

Claims

1. A Co-Cr-Pt-B ferromagnetic sputtering target, A Co-Cr-Pt-B alloy phase (A) containing 0.7 at% to 30 at% of B, It consists of an alloy phase (B) which is one of Co-B alloys, Co-Cr-B alloys, or Co-Pt-B alloys, containing 5 at% to 20 at% of B, and in which B is distributed throughout without the B aggregated phase being unevenly distributed. The alloy phase (A) accounts for 50 vol% or more of the sputtering target, the alloy phase (B) accounts for less than 50 vol%, and the sum of the alloy phases (A) and (B) is 100 vol%. A Co-Cr-Pt-B ferromagnetic sputtering target characterized by having a sputter discharge voltage of 330V or less, measured at 500W.

2. The Co-Cr-Pt-B ferromagnetic sputtering target according to claim 1, characterized in that Cr is greater than 0 at% but 30 at% or less, Pt is 5 at% or more but 30 at% or less, B is 5 at% or more but 25 at% or less, and the remainder is Co and unavoidable impurities.

3. The Co-Cr-Pt-B ferromagnetic sputtering target according to claim 1 or 2, characterized in that the alloy phase (A) further contains, as additive elements, one or more elements selected from Al, Si, Sc, Ti, V, Mn, Fe, Ni, Cu, Zn, Ge, Y, Zr, Nb, Ta, Mo, W, Ru, Ag, Sn, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Hf in an amount exceeding 0 at% and not exceeding 25 at%.

4. A method for manufacturing a Co-Cr-Pt-B ferromagnetic sputtering target according to any one of claims 1 to 3, Co-Cr-Pt-B alloy powder containing more than 0.7 at% and 30 at% or less of B, A mixing step to obtain a mixed powder by weakly mixing one of the following: Co-B alloy powder, Co-Cr-B alloy powder, or Co-Pt-B alloy powder containing 5 at% to 20 at% of B, A sintering step in which the mixed powder is sintered to obtain a sintered body, A manufacturing method characterized by including the following.

5. The manufacturing method according to claim 4, characterized in that the Co-Cr-Pt-B alloy powder and the Co-B alloy powder, Co-Cr-B alloy powder, or Co-Pt-B alloy powder are atomized alloy powders.

6. The manufacturing method according to claim 4 or 5, characterized in that the sintering step involves holding the mixed powder at a pressure of 10 MPa to 100 MPa and a temperature of 700°C to 1300°C for 30 minutes to 3 hours.

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