JP2020037713A - Sputtering target allowing stable discharge - Google Patents

Abstract

To provide a ferromagnetic material sputtering target capable of obtaining stable discharge in a magnetron sputtering apparatus, having less particles generated during sputtering and capable of improving a leakage magnetic flux.SOLUTION: A sputtering target comprises: a plurality of metal particles (A) formed of Co or Co alloy; and a composite phase (B) obtained by dispersing Co or Co alloy filling gaps between the plurality of metal particles and metal oxide to each other. A difference between Co concentration in the Co or Co alloy constituting the plurality of metal particles (A) and Co concentration in Co or Co alloy constituting the composite phase (B) is 5 at% or less, and the ratio of the area of the plurality of metal particles to the total area of the plurality of metal particles (A) and the composite phase (B) is 20-65%.SELECTED DRAWING: Figure 3

Description

The present invention relates to a magnetic thin film of a magnetic recording medium, in particular, a ferromagnetic material sputtering target used for forming a magnetic recording layer of a hard disk employing a perpendicular magnetic recording method. The present invention relates to a non-metallic inorganic material particle-dispersed ferromagnetic material sputtering target capable of obtaining a stable discharge and generating less particles.
In the following description, "sputtering target" may be simply abbreviated as "target", but it means substantially the same. I will tell you just in case.

In the field of magnetic recording represented by a hard disk drive, a material based on a ferromagnetic metal such as Co, Fe or Ni is used as a material of a magnetic thin film for recording. For example, a Co-Cr-based or Co-Cr-Pt-based ferromagnetic alloy containing Co as a main component has been used for a recording layer of a hard disk employing an in-plane magnetic recording system. In addition, non-magnetic particles such as oxides and carbon are dispersed in a Co—Cr—Pt-based ferromagnetic alloy containing Co as a main component in a recording layer of a hard disk employing a perpendicular magnetic recording method that has been put into practical use in recent years. Composite materials are often used. The magnetic thin film is often produced by a sputtering method using a sputtering target containing the above material as a component from the viewpoint of productivity. In the sputtering method, a substrate serving as a positive electrode and a target serving as a negative electrode are opposed to each other, and a high voltage is applied between the substrate and the target in an inert gas atmosphere to generate an electric field.
At this time, the inert gas is ionized and a plasma composed of electrons and cations is formed. When the cations in the plasma collide with the surface of the target (negative electrode), atoms constituting the target are knocked out. However, the ejected atoms adhere to the opposing substrate surface to form a film. By such a series of operations, the principle that the material constituting the target is formed on the substrate is used.

  There are various types of sputtering apparatuses, and a magnetron sputtering apparatus equipped with a DC power supply is widely used for forming the magnetic recording film because of its high productivity.

  Magnetron sputtering is a technique in which a permanent magnet is arranged on the back side of a target, and secondary electrons generated by sputtering are confined by the magnetic field to efficiently advance sputtering. However, in the case of a ferromagnetic target such as a target for perpendicular magnetic recording, a magnetic field passes through the inside of the target, and the leakage magnetic flux is reduced, so that sputtering efficiency is deteriorated. Therefore, it is necessary to increase the leakage magnetic flux of the target. At the same time, with the recent increase in the recording density of hard disk drives, the floating amount of the magnetic head has become smaller, and the size and number of particles allowed as a magnetic recording medium have been severely restricted. Particles are also important.

For example, a mixed powder obtained by mixing a Co powder, a Cr powder, a TiO ₂ powder, and a SiO ₂ powder and a Co spherical powder are mixed with a planetary mixer, and the mixed powder is formed by hot pressing to form a magnetic recording medium. A method for obtaining a sputtering target has been proposed (Patent Document 1).
In this case, the target structure has a spherical metal phase (B) having a higher magnetic permeability than the surrounding structure in the phase (A), which is a metal base in which non-metallic inorganic material particles are uniformly dispersed. Can be seen (FIG. 1 of Patent Document 1). Such a structure has a problem described below, and cannot be said to be a suitable sputtering target for a magnetic recording medium.

WO 2011/089760

  As described above, when attempting to sputter a ferromagnetic material sputtering target with a magnetron sputtering apparatus, most of the magnetic flux from the magnet passes through the inside of the target, which is a ferromagnetic material, so that the leakage magnetic flux becomes small, and discharge occurs during sputtering. However, there is a big problem that the discharge is not stable even if the discharge is performed.

  In order to solve this problem, a method of forming a portion having high magnetic permeability (coarse grain portion) and a low portion (oxide dispersing portion) by adding Co coarse particles, lowering the overall magnetic permeability, and increasing the leakage magnetic flux. Can be considered. However, since there is a difference in composition between the Co coarse-grain portion and the oxide dispersion portion, there is a problem that metal diffusion occurs in the Co coarse-grain portion and the oxide dispersion portion in the sintering step, and consequently oxide coagulation occurs. Can occur. This causes an increase in the number of particles. Further, such a method is difficult to obtain an effect with a composition containing a small amount of Cr and containing Pt.

  Therefore, an object of the present invention is to provide a ferromagnetic material sputtering target that can obtain stable discharge with a magnetron sputtering apparatus, generate less particles during sputtering, and improve leakage magnetic flux, based on the above findings.

  The inventor of the present invention has made intensive studies to solve the above-mentioned problems, and focused on controlling the concentration dispersion of the oxide, not the method of providing a metal composition difference as in the case of the Co coarse-grained portion and the oxide dispersion portion. By doing so, the inventors found a method of making the magnetic permeability non-uniform and improving the leakage magnetic flux of the entire target. Then, they have found that by making the Co concentration in the target as uniform as possible, an effect of reducing the aggregation of the oxide due to the suppression of diffusion can be obtained.

Therefore, the present invention is specified as follows.
(1) A plurality of metal particles (A) composed of Co or a Co alloy, and a composite phase in which Co or a Co alloy and a metal oxide filling a gap between the plurality of metal particles are mutually dispersed. B)
A difference between a Co concentration in Co or Co alloy constituting the plurality of metal particles (A) and a Co concentration in Co or Co alloy constituting the composite phase (B) is 5 at% or less;
An area ratio of the plurality of metal particles (A) to a total area of the plurality of metal particles (A) and the composite phase (B) is 20 to 65%;
Sputtering target.
(2) The surface of the plurality of metal particles (A) on one surface where the plurality of metal particles (A) are observed, wherein the plurality of metal particles (A) have a particle diameter of 20 μm or more and the average of the particle diameters is 20 to 250 μm. Sputtering target.
(3) The plurality of metal particles (A) and the composite phase (B) both contain a Co alloy, and the Co alloy is at least one alloy element selected from the group consisting of Cr, Pt, Ru, and B The sputtering target according to (1) or (2), comprising:
(4) The sputtering target according to any one of (1) to (3), wherein an area ratio of the metal oxide in the composite phase (B) is 40 to 70%.

  By performing sputtering using the ferromagnetic material sputtering target according to the present invention, stable discharge can be obtained at the time of sputtering, and particles are less generated at the time of sputtering, and leakage magnetic flux can be improved.

It is a figure showing a plurality of metal particles (A) and a composite phase (B). It is a laser microscope photograph of each sectional structure of each Example and a comparative example. It is a laser microscope photograph of each sectional structure of each Example and a comparative example. It is a figure which shows the Co concentration in Co or Co alloy which comprises several metal particles (A), and the Co concentration in Co or Co alloy which comprises composite phase (B). It is a figure showing a measuring method of an area ratio of a plurality of metal particles (A) to a total area of a plurality of metal particles (A) and a composite phase (B). It is a figure which shows the measuring method of the area ratio of the metal oxide in a composite phase (B).

  In the ferromagnetic sputtering target of the present invention, a plurality of metal particles (A) composed of Co or a Co alloy, and a Co or Co alloy and a metal oxide that fill gaps between the plurality of metal particles are dispersed in each other. A combined composite phase (B). A plurality of metal particles (A) and a composite phase (B) composed of Co or a Co alloy have a difference in magnetic permeability due to a difference in the concentration of the metal oxide. Can be.

(Plurality of metal particles (A) and composite phase (B))
In one embodiment of the sputtering target according to the present invention, a plurality of metal particles (A) composed of Co or a Co alloy include Co or a Co alloy and a metal oxide, which fill gaps between the plurality of metal particles described later. Are compared with the composite phase (B) dispersed in each other, the Co concentration in the Co or Co alloy constituting the plurality of metal particles (A) and the Co or Co alloy constituting the composite phase (B) Is 5 at% or less.
As described above, as a method of improving the leakage magnetic flux as a whole target, it is conceivable to provide a portion having a small amount of metal oxide and a high magnetic permeability and a portion where the metal oxide is concentrated and the magnetic permeability is low. If there is a large difference in composition in the portion, metal diffusion occurs, and an oxide can be aggregated on the outer peripheral portion of (A), so that the number of particles increases. On the other hand, the difference between the Co concentration in the Co or Co alloy constituting the plurality of metal particles (A) and the Co concentration in the Co or Co alloy constituting the composite phase (B) is set to 5 at% or less. Therefore, metal diffusion can be suppressed, and agglomeration of oxides can be suppressed, so that leakage magnetic flux can be improved, stable discharge can be obtained with a magnetron sputtering device, and the effect of reducing generation of particles during sputtering can be obtained. can get.
From this viewpoint, the difference between the Co concentration in Co or Co alloy constituting the plurality of metal particles (A) and the Co concentration in Co or Co alloy constituting the composite phase (B) is 3 at% or less. Is preferred.

  The metal particle portion and the metal oxide portion can be determined by the density of the color at the time of observing the structure. For example, as shown in FIG. 1, in the result of observation of the structure by SEM (scanning electron microscope), the intensity of the secondary electrons appears as shading of the image, so that the metal portion is generally bright because the secondary electron intensity is strong. Oxides appear dark because of their lower strength. It is possible to distinguish the region between the metal coarse-grain portion and the matrix, or the metal portion and the metal oxide portion in the matrix, based on the relative image density difference. However, depending on the device and conditions used for observing the structure, the metal particle portion does not always appear white and the metal oxide portion does not appear black, and may be reversed. In that case, the portion that looks white may be measured as the metal oxide portion, and the portion that looks black may be measured as the metal particle portion. In this specification, an embodiment will be described in which a metal particle portion looks white and a metal oxide portion looks black.

The measurement of the Co concentration is performed by elemental analysis based on point analysis using SEM / EDS (scanning electron microscope / energy dispersive X-ray spectroscopy). As a measurement method, as shown in FIG. 4, a tissue image is acquired at a low magnification for a sputtering target. In the low-magnification tissue image, the plurality of metal particles (A) and the composite phase (B) can be determined from the shade of color, and quantitative analysis is performed on the plurality of metal particles (A). The measurement position is measured at least inside 8 μm from the outermost periphery of the metal particles (A). In order to improve the accuracy of the measurement, at least five metal particles (A) are selected, the Co concentration is measured, and the average value is defined as the Co concentration in Co or a Co alloy constituting the plurality of metal particles (A). . The specific numerical value of the low magnification is preferably a magnification at which a plurality of metal particles (A) can be observed in one visual field, and is preferably 200 to 500 times. The size of the spot when performing quantitative analysis is 3 μm square or less.
Subsequently, an image of the complex phase (B) portion is acquired at a high magnification in the tissue image of a low magnification. At this time, the position where the image is measured at a high magnification is a position at least 10 μm away from the outermost peripheral portion of any of the metal particles (A). In this image, the metal particle portion and the metal oxide portion in the composite phase (B) can be determined from the shading of the color, and the point analysis is performed on the metal particle portion of the composite phase (B). The case where the metal particle portion of the composite phase (B) is measured and the oxygen value of the measurement result is 1 at% or less is adopted. In order to improve the accuracy of the measurement, at least five metal particles of the composite phase (B) are selected, the Co concentration is measured, and the average value is used as the Co concentration in Co or the Co alloy constituting the composite phase (B). And Specific numerical values of the high magnification are preferably magnifications at which only the composite phase (B) can be individually observed, and more preferably 5000 times or more. The size of the spot when performing quantitative analysis is 0.5 μm square or less.
The measuring device is not limited to the SEM / EDS as long as it has a function of observing the structure and a function of performing elemental analysis. For example, SEM / WDS, TEM / EDS, EPMA, etc. may be used.

  The area ratio of the plurality of metal particles (A) to the total area of the plurality of metal particles (A) and the composite phase (B) is set to 20 to 65%. If the area ratio of the plurality of metal particles (A) is lower than 20%, the effect of improving the leakage magnetic flux cannot be obtained, and if the area ratio exceeds 65%, the oxides are connected to each other and become coarse, increasing the number of particles. Resulting in. Preferably, the area ratio of the plurality of metal particles (A) is 35 to 45%.

  The measurement of the area ratio of the plurality of metal particles (A) to the total area of the plurality of metal particles (A) and the composite phase (B) is performed by observing the structure with a laser microscope. As a measuring method, it can be obtained by observing the cut surface of the sputtering target with a laser microscope, measuring the area of a plurality of metal particles (A) present in a visual field of 200 times, and dividing this by the area of the entire visual field. it can. Specifically, since a plurality of metal particles (A) look white and the composite phase (B) looks black in a laser micrograph, binarization is performed using image processing software (FIG. 5), and the area of each is calculated. Further, in order to improve the accuracy, the same measurement is performed in any five visual fields, and the average value of the area of the plurality of metal particles (A) and the composite phase (B) is calculated. The area ratio of (A) is calculated.

  As the metal oxide, an oxide of one or more components selected from Co, Cr, Ta, Si, Ti, Zr, Al, Nb, and B can be used. Note that, instead of the metal oxide, a nitride, a carbide, or a carbonitride can be used in addition to the oxide. Further, these inorganic materials can be used in combination. These can have a function equivalent to an oxide.

The average of the particle diameters of the plurality of metal particles (A) on one surface where the plurality of metal particles (A) are observed is preferably 20 to 250 μm. When the average of the particle diameters is less than 20 μm, it is difficult to distinguish from the (B) phase, and it is difficult to obtain a difference in the concentration of the metal oxide phase. If it exceeds 250 μm, the smoothness of the target surface is lost, and the possibility of becoming a particle source increases. In addition, when the particle diameter of the plurality of metal particles (A) is less than 16 μm, it is difficult to distinguish from the (B) phase. Therefore, the particle diameter of the plurality of metal particles (A) is 16 μm or more. B) Think as a phase.
As for the particle diameter of the plurality of metal particles (A), the area of the metal particle is obtained from the tissue observation image, and the diameter of a circle corresponding to the area is defined as the particle diameter. Specifically, the cut surface of the sputtering target is observed with a laser microscope, the area of a plurality of metal particles (A) present in a visual field of 200 times is measured, and the diameter of a circle corresponding to the area is defined as the particle diameter. This can be determined by measuring this for a plurality of metal particles (A) in the entire field of view and calculating the average value of these.
In addition, in the composite phase (B), particles having a particle diameter of less than 20 μm may be observed as particles made of Co or a Co alloy, but these are not counted again as a plurality of metal particles (A).

  The area ratio of the metal oxide in the composite phase (B) is preferably 40 to 70%. When the area ratio of the metal oxide is 40% or more, the effect of improving the leakage magnetic flux becomes more remarkable, and when the area ratio is 70% or less, the metal oxide can be prevented from becoming coarse.

  The measurement of the area ratio of the metal oxide of the composite phase (B) is also performed by observing the structure with a laser microscope. As a measuring method, a cut surface of a sputtering target is observed with a laser microscope, a composite phase (B) existing in a visual field of 200 times is confirmed, and a metal present in the composite phase (B) in a visual field of 12000 times is further observed. The area can be determined by measuring the area of the oxide and dividing the area by the area of the entire visual field. Specifically, Co or Co alloy constituting the composite phase (B) looks white and the metal oxide looks black in the laser micrograph, so that it was binarized using image processing software (FIG. 6), and The area is calculated, and the same measurement is performed in any five visual fields to improve the accuracy, and the average value of the area of Co or Co alloy and the metal oxide is calculated, whereby the area ratio of the metal oxide is calculated. Is calculated.

A preferred ferromagnetic sputtering target of the present invention may contain at least one selected from the group consisting of Cr, Pt, Ru and B in a composition excluding a metal oxide. These are elements added as necessary to improve the characteristics as a magnetic recording medium. Specifically, a composition in which Cr is zero or 15 mol% or less, Pt is 10 mol% or more and 50 mol% or less, Ru is zero or 15 mol% or less, B is zero or 15 mol% or less, and the balance is Co is preferable.
When containing one or more selected from the group consisting of Cr, Pt, Ru and B, the plurality of metal particles (A) and the composite phase (B) both contain a Co alloy, and the Co alloy is It is preferable to contain at least one selected from the group consisting of Cr, Pt, Ru and B as an alloy element.

  In the present invention, other than the plurality of metal particles (A) and the composite phase (B), other phases can be provided in the sputtering target as long as they do not hinder the effects of the present invention. In order to maximize the effects of the present invention, it is preferable that other phases do not exist.

(Production method)
The sputtering target according to the present invention can be manufactured using the powder sintering method, for example, by the following method. First, a particle powder having a composition composed of Co or a Co alloy, and a particle powder in which the Co or Co alloy and the metal oxide are mutually dispersed are produced, and these are formed to have a desired target composition. Weighed and mixed into a powder for sintering. This is sintered by a hot press or the like to produce the sputtering target of the present invention.

  As a starting material, a fine Co metal powder or a Co alloy powder, or a coarse Co metal powder or a Co alloy powder and a metal oxide powder are used. It is desirable to use fine Co metal powder or Co alloy powder having a maximum particle size of 20 μm or less. The coarse Co metal powder or Co alloy powder desirably has a particle size range of 20 to 250 μm. It is desirable to use a metal oxide powder having a maximum particle size of 5 μm or less. Note that if the particle size is too small, the particles are apt to aggregate, so it is more preferable to use one having a particle size of 0.1 μm or more.

First, in order to form a phase (B) in which Co or a Co alloy and a metal oxide are mutually dispersed, fine Co metal powder or a Co alloy powder and a metal oxide powder are weighed. This powder is mixed using a well-known method such as a ball mill while also serving as pulverization. At this time, it is desirable that an inert gas be sealed in the pulverizing container to suppress oxidation of the raw material powder as much as possible. Examples of the inert gas include Ar and N ₂ gases. Next, a coarse Co metal powder or a Co alloy powder is added to the mixed powder to form a phase (A) composed of Co or a Co alloy, and further mixed. At this time, a ball mill having a high crushing power is not used so that the particle powder is not crushed. By not finely pulverizing the particle powder, coarse metal particles can be left and diffusion between the particle powders can be suppressed during sintering, and the sintering including the plurality of metal particles (A) and the composite phase (B) can be performed. You can get union. Further, the particle powder can be mixed by a method other than the above.

  The sintering powder thus obtained is molded and sintered by hot pressing. In addition to hot pressing, a plasma discharge sintering method and a hot isostatic pressing method can be used. The holding temperature during sintering is preferably set to the lowest temperature in a temperature range where the target is sufficiently densified. Depending on the composition of the target, the temperature is often in the range of 800 to 1300 ° C. Through the above steps, a sintered body for a ferromagnetic material sputtering target can be manufactured.

  The obtained sintered body is formed into a desired shape using a lathe or the like, whereby the sputtering target according to the present invention can be manufactured. The target shape is not particularly limited, and examples thereof include a flat plate shape (including a disk shape and a rectangular plate shape) and a cylindrical shape. The sputtering target according to the present invention is particularly useful as a sputtering target used for forming a granular magnetic thin film.

  Hereinafter, Examples of the present invention are shown together with Comparative Examples, but these Examples are provided for better understanding of the present invention and its advantages, and are not intended to limit the present invention. .

<Preparation of sputtering target>
-Examples 1 to 5, Comparative Examples 2 and 3
As a raw material powder, a Co powder having an average particle diameter of 3 μm, a TiO ₂ powder having an average particle diameter of 1 μm, a SiO ₂ powder having an average particle diameter of 1 μm, a CoO powder having an average particle diameter of 2 μm, and a Co atomized powder having a diameter in the range of 50 to 150 μm. Was prepared. Each of the Examples and Comparative Examples was prepared such that these powders were configured to have the composition of the plurality of metal particles (A) and the composite phase (B) shown in Table 1 and the Co concentration difference between (A) and (B). Was weighed.
Next, the weighed Co powder, TiO ₂ powder, and SiO ₂ powder were each enclosed in a 10-liter capacity ball mill pot together with zirconia balls as a medium, and were rotated and mixed for 20 hours. Furthermore, CoO powder and Co atomized powder were added to the obtained mixed powder, and mixed for 2 hours with a planetary mixer having a capacity of about 7 L to obtain a mixed powder for sintering.
The mixed powder constituting each composition was filled in a carbon mold, and hot-pressed in a vacuum atmosphere under the conditions of a temperature of 950 ° C., a holding time of 2 hours and a pressure of 30 MPa to obtain a sintered body.
-Examples 6, 7, and 8 and Comparative Examples 4 and 5
As the raw material powder, a Co powder having an average particle diameter of 3 μm, a Pt powder having an average particle diameter of 1 μm, a TiO ₂ powder having an average particle diameter of 1 μm, a SiO ₂ powder having an average particle diameter of 1 μm, a CoO powder having an average particle diameter of 2 μm, and a diameter of 30 to A Co-Pt atomized powder in a range of 150 µm was prepared. Each of the Examples and Comparative Examples was prepared such that these powders were configured to have the composition of the plurality of metal particles (A) and the composite phase (B) shown in Table 1 and the Co concentration difference between (A) and (B). Was weighed.
Next, the weighed Co powder, Pt powder, TiO ₂ powder, and SiO ₂ powder were each sealed in a 10-liter capacity ball mill pot together with zirconia balls as a medium, and rotated and mixed for 20 hours. Further, CoO powder and Co-Pt atomized powder were added to the obtained mixed powder, and mixed for 2 hours with a planetary mixer having a capacity of about 7 L to obtain a mixed powder for sintering.
The mixed powder constituting each composition was filled in a carbon mold, and hot-pressed in a vacuum atmosphere under the conditions of a temperature of 950 ° C., a holding time of 2 hours and a pressure of 30 MPa to obtain a sintered body.
-Comparative Examples 1 and 6
As a raw material powder, a Co powder having an average particle diameter of 3 μm, a Pt powder having an average particle diameter of 1 μm, a TiO ₂ powder having an average particle diameter of 1 μm, a SiO ₂ powder having an average particle diameter of 1 μm, and a CoO powder having an average particle diameter of 2 μm were prepared. Each of the Examples and Comparative Examples was prepared such that these powders were configured to have the composition of the plurality of metal particles (A) and the composite phase (B) shown in Table 1 and the Co concentration difference between (A) and (B). Was weighed.
Next, the weighed Co powder, Pt powder, TiO ₂ powder, and SiO ₂ powder were each sealed in a 10-liter capacity ball mill pot together with zirconia balls as a medium, and rotated and mixed for 20 hours. Further, a CoO powder was added to the obtained mixed powder, and mixed for 2 hours with a planetary mixer having a capacity of about 7 L to obtain a mixed powder for sintering.
The mixed powder constituting each composition was filled in a carbon mold, and hot-pressed in a vacuum atmosphere under the conditions of a temperature of 950 ° C., a holding time of 2 hours and a pressure of 30 MPa to obtain a sintered body.

  Next, each sintered body was cut into a shape having a diameter of 180.0 mm and a thickness of 5.0 mm using a lathe to obtain a disk-shaped sputtering target. Composition analysis of a chip obtained by cutting the target according to each of the test examples obtained by the above-described production procedure with a lathe using an ICP-AES device (manufactured by Hitachi High-Tech Science Corporation (formerly SII), device name: SPS3100HV). Was performed, and it was confirmed that the composition of each target was substantially the same as the weighed composition. Here, in order to improve the measurement accuracy, the metal composition analysis was performed by drawing a calibration curve by the internal standard method.

<Binarization method>
The area ratio of the plurality of metal particles (A) was measured by observing the structure with the laser microscope described above. KEYENCE VK-9710 was used for the laser microscope. For the binarization of the image, image processing software image J (manufactured by National Institutes of Health, Ver 1.49n) was used. Read an image from File → Open. Select 8-bit from Image → Type. A part of the image excluding the scale is selected, and the scale part is cut out by Image → Crop. Select Process → Filters → Gaussian Blur, enter 2 for Sigma, and click OK. Select Process → Binary → Make Binary. The image is binarized according to the above procedure.

<Measurement of Co concentration in (A) phase and (B) phase>
The measurement of the Co concentration of the plurality of metal particles (A) and the composite phase (B) is performed by elemental analysis by point analysis using SEM-EDS (Hitachi S-3700N). As a measurement method, an image of the sputtering target is acquired at 500 times by SEM. In the micrograph, since the plurality of metal particles (A) appear white and the composite phase (B) appears black, point analysis is performed on the white portion. The measurement position is measured at least inside 8 μm from the outermost periphery of the metal particles (A). In order to improve the accuracy of the measurement, at least five metal particles (A) are selected, the Co concentration is measured, and the average value is defined as the Co concentration in Co or a Co alloy constituting the plurality of metal particles (A). .
Subsequently, the composite phase (B) which looks black in an image of 500 times with an SEM is imaged at 5000 times. At this time, the position where the image is measured at 5000 times is a position at least 10 μm away from the outermost peripheral portion of any of the metal particles (A). In this image, a portion that looks white and a portion that looks black can be observed, and a point analysis is performed on the white portion. The white portion is measured, and the case where the oxygen value of the measurement result is 1 at% or less is adopted. In order to improve the accuracy of the measurement, at least five white portions of the composite phase (B) are selected, the Co concentration is measured, and the average value is determined as the Co concentration in the Co or Co alloy constituting the composite phase (B). I do.

<Method of measuring PTF>
The measurement of the leakage magnetic flux was performed in accordance with ASTM F2086-01 (Standard Test Method for Pass Through Through Flux of Circular Magnetic Sputting Targets, Method 2). The center of the target is fixed, and the leakage magnetic flux density measured by rotating at 0, 30, 60, 90, and 120 degrees is divided by the value of the reference field defined by ASTM and multiplied by 100. Expressed as a percentage. The result of averaging these five points was taken as the average leakage magnetic flux density (PTF).

<Sputtering evaluation>
The target was attached to a DC magnetron sputtering apparatus to perform sputtering. The sputtering conditions were as follows: sputtering power was 1 kW, Ar gas pressure was 1.5 Pa, pre-sputtering was performed at 2 kWhr, and then sputtering was performed on a 4-inch diameter silicon substrate with a target film thickness of 1000 nm. Then, the number of particles attached to the substrate was measured by a particle counter. Candela CS920 (manufactured by KLA Tencor) was used for the particle counter. Particles are identified by irradiating a laser to a wafer formed by sputtering and detecting reflection and scattering of the laser.

  Comparing the results of these Examples and Comparative Examples, Comparative Example 1 does not include a plurality of metal particles (A) as compared with Examples 1 to 5, so the average leakage magnetic flux density is low, and the number of particles increases. It is thought that it is. In Comparative Example 2, the area ratio of the plurality of metal particles (A) was smaller than the range of the present invention, the effect of improving the average leakage magnetic flux density was not obtained, and it is considered that the number of particles increased. In Comparative Example 3, it is considered that the area ratio of the metal particles (A) is larger than the range of the present invention, the oxide becomes coarse, and the number of particles increases. In Comparative Examples 4 and 5, compared with Examples 6 to 8, the difference in the Co concentration between the (A) and (B) phases was larger than the range of the present invention, and coarse oxides were observed around (A). It is considered that the number of particles is increasing. Comparative Example 6 does not include a plurality of metal particles (A) as in Comparative Example 1, so that the average leakage magnetic flux density is low and the number of particles is considered to be increasing.

Claims (4)

A plurality of metal particles (A) composed of Co or a Co alloy, and a composite phase (B) in which Co or a Co alloy and a metal oxide that fill gaps between the plurality of metal particles are mutually dispersed. Prepared,
A difference between a Co concentration in Co or Co alloy constituting the plurality of metal particles (A) and a Co concentration in Co or Co alloy constituting the composite phase (B) is 5 at% or less;
An area ratio of the plurality of metal particles (A) to a total area of the plurality of metal particles (A) and the composite phase (B) is 20 to 65%;
Sputtering target.   2. The sputtering target according to claim 1, wherein a particle diameter of the plurality of metal particles (A) is 20 μm or more and an average of the particle diameters is 20 to 250 μm on one surface where the plurality of metal particles (A) are observed.   The plurality of metal particles (A) and the composite phase (B) both contain a Co alloy, and the Co alloy contains at least one alloy element selected from the group consisting of Cr, Pt, Ru, and B. The sputtering target according to claim 1.   The sputtering target according to any one of claims 1 to 3, wherein an area ratio of the metal oxide in the composite phase (B) is 40 to 70%.