JP7554192B2 - Sputtering target member for forming non-magnetic layer - Google Patents

Description

The present invention relates to a sputtering target member suitable for forming a thin film for a non-magnetic layer that constitutes a perpendicular magnetic recording medium.

In magnetic recording media used in magnetic recording and playback devices such as HDDs (hard disk drives), the perpendicular magnetic recording method, which allows for higher recording density, has come into the spotlight, replacing the in-plane magnetic recording method used up until now. In the perpendicular magnetic recording method, the axis of easy magnetization in the magnetic recording layer is oriented perpendicular to the substrate surface, and has the advantage of being able to suppress thermal fluctuation phenomena compared to the in-plane magnetic recording method.

Perpendicular magnetic recording media that use the perpendicular magnetic recording method generally have a layer called the magnetic recording layer, which is responsible for the magnetism, and a non-magnetic layer used to improve the characteristics of the magnetic recording layer. hcp-Co alloys are often used as micro-magnets for the magnetic recording layer. When the magnetic recording layer has an hcp (hexagonal close packed) structure, the axis of easy magnetization is the C-axis, and the C-axis must be oriented in the normal direction to the substrate.

In order to improve the orientation of this C-axis, it is effective to provide a non-magnetic layer (also called an "orientation control layer") with an hcp structure under the magnetic recording layer. CoCr alloys, Ti, V, Zr, Hf, etc. are known to be used as non-magnetic layers, but it is known that Ru (ruthenium) in particular can effectively improve the crystal orientation of the magnetic recording layer and increase the coercive force Hc (JP 2012-2088992 A, JP 2009-245484 A, WO 2010/038448 A, JP 2004-310910 A).

JP 2012-208992 A JP 2009-245484 A International Publication No. 2010/038448 JP 2004-310910 A

In recent years, the market price of Ru has risen sharply, and there is a problem that the use of Ru increases production costs. For this reason, it would be advantageous to form a non-magnetic layer with an hcp structure while reducing the amount of Ru used. The present invention was created in consideration of such circumstances, and in one embodiment, the objective of the present invention is to provide an economical sputtering target member that is advantageous for forming a non-magnetic layer with an hcp structure that constitutes a perpendicular magnetic recording medium. In another embodiment, the objective of the present invention is to provide a film formation method using such a sputtering target member.

The inventors have conducted extensive research to solve the above problems and have found that a sputtering target member having a structure in which a metal phase mainly composed of Co, Pt, and Mo and an oxide phase are mutually dispersed is suitable for forming a nonmagnetic layer. The present invention is exemplified below.

[1]
A sputtering target member for forming a nonmagnetic layer, the sputtering target member having a structure in which a metal phase and an oxide phase are mutually dispersed,
The metal phase contains, based on the overall composition of the target member, 20 to 60 mol % Co, 5 to 30 mol % Pt, and 1 to 40 mol % Mo, and also contains Mo, Cr, Ru, and B in a total concentration of 25 mol % or more;
The volume fraction of the oxide phase is 10 to 45%.
A sputtering target member for forming a non-magnetic layer.
[2]
The sputtering target member for forming a nonmagnetic layer according to [1], wherein the metal phase contains 25 to 30 mol % of Mo based on the overall composition of the target member.
[3]
3. The sputtering target member for forming a nonmagnetic layer according to claim 1, wherein the concentration of Cr in the metal phase is 5 mol % or less based on the total composition of the target member.
[4]
The sputtering target member for forming a nonmagnetic layer according to any one of [1] to [3], wherein the concentration of Ru in the metal phase is 5 mol % or less based on the overall composition of the target member.
[5]
The sputtering target member for forming a nonmagnetic layer according to any one of [1] to [4], wherein the concentration of B in the metal phase is 5 mol % or less based on the overall composition of the target member.
[6]
The sputtering target member for forming a nonmagnetic layer according to any one of [1] to [5], wherein the oxide phase contains an oxide of one or more metals selected from the group consisting of Ti, Si, B, Co, Cr, Ta, Mn, Zr, and Nb.
[7]
The sputtering target member for forming a nonmagnetic layer according to any one of [1] to [6], which has a relative density of 90% or more.
[8]
A sputtering target having a structure in which the sputtering target member for forming a nonmagnetic layer according to any one of [1] to [7] and a backing plate or a backing tube are laminated via a brazing material layer.
[9]
A film forming method comprising a step of sputtering using the sputtering target member for forming a nonmagnetic layer according to any one of [1] to [7].

A non-magnetic film can be easily obtained by sputtering the sputtering target member according to one embodiment of the present invention. Since the non-magnetic film maintains the hcp structure of the metal phase, when the magnetic recording layer in the perpendicular magnetic recording medium has an hcp (hexagonal close-packed) structure, the effect of orienting the C-axis in the normal direction of the substrate can be obtained. In addition, since the metal phase and the oxide phase of the film are neatly separated, it is expected to contribute to the separation between magnetic grains in the magnetic layer formed on the upper layer. In addition, Mo used in the sputtering target member according to one embodiment of the present invention is available at a lower price than Ru. Therefore, the sputtering target member according to one embodiment of the present invention can be expected to be used to form a non-magnetic layer that constitutes a perpendicular magnetic recording medium.

In one embodiment, the sputtering target member for forming a nonmagnetic layer according to the present invention has a structure in which a metal phase and an oxide phase are mutually dispersed. The mutual dispersion of the metal phase and the oxide phase in the sputtering target member is advantageous for forming a homogeneous film.

1. Metallic Phase
In one embodiment of the sputtering target member for forming a nonmagnetic layer according to the present invention, the metal phase contains, based on the overall composition of the target member, 20 to 60 mol % Co, 5 to 30 mol % Pt, and 1 to 40 mol % Mo. Co, Pt, and Mo may each be present as a simple metal, or may be present as a CoPt alloy, a CoPtMo alloy, a CoMo alloy, a PtMo alloy, or an alloy of any of these with one or more of Cr, Ru, and B.

The reason why the lower limit of the Co concentration in the metal phase is set to 20 mol% or more is due to the ease of forming a Co alloy. If the amount of Co is reduced, it becomes difficult to maintain the hcp structure of Co and Co alloys. The lower limit of the Co concentration is preferably 30 mol% or more, more preferably 35 mol% or more, and even more preferably 40 mol% or more. The reason why the upper limit of the Co concentration in the metal phase is set to 60 mol% or less is for demagnetization. If the amount of Co is increased, it becomes difficult to demagnetize even if other metals are used. The upper limit of the Co concentration is preferably 55 mol% or less, more preferably 50 mol% or less, and even more preferably 45 mol% or less.

The Pt concentration in the metal phase is set to 5 mol% or more and 30 mol% or less because it affects the stability of the magnetic layer formed on the upper layer. At most, the amount of Pt at least deteriorates the stability of the hcp structure in the magnetic layer. The lower limit of the Pt concentration is preferably 10 mol% or more, and more preferably 15 mol% or more. The upper limit of the Pt concentration is preferably 28 mol% or less, and more preferably 25 mol% or less.

The reason why the lower limit of the Mo concentration in the metal phase is set to 1 mol% or more is that Mo is cheaper to obtain than Ru, and it is found to contribute to the demagnetization of the sputtered film (in other words, the reduction of saturation magnetization), and is also highly effective in maintaining the hcp structure of the metal phase in the sputtered film. Furthermore, Mo is chemically stable and difficult to oxidize, so there is a characteristic that there is little risk of unintentionally reducing oxides such as CoO contained in the oxide phase. This characteristic is advantageous in that it is easy to adjust the constituent phases of the sputtered film. The lower limit of the Mo concentration is preferably 5 mol% or more, more preferably 15 mol% or more, and even more preferably 25 mol% or more.

In addition, the upper limit of the Mo concentration in the metal phase is set to 40 mol% or less in order to prevent the sputtering target member from cracking because the sputtering target member is prone to cracking if the Mo concentration is too high. The upper limit of the Mo concentration is preferably 40 mol% or less, more preferably 35 mol% or less, and even more preferably 30 mol% or less.

Therefore, in a preferred embodiment of the sputtering target member for forming a non-magnetic layer according to the present invention, the metal phase contains 35 to 50 mol % Co, 10 to 28 mol % Pt, and 15 to 35 mol % Mo, based on the overall composition of the target member, and in a more preferred embodiment, the metal phase contains 40 to 45 mol % Co, 15 to 25 mol % Pt, and 25 to 30 mol % Mo, based on the overall composition of the target member.

The metal phase contains Mo, Cr, Ru and B in a total concentration of 25 mol% or more based on the overall composition of the target member. These metal elements contribute to the non-magnetization of the sputtered film, so it is desirable to contain them in a total concentration of 25 mol% or more. However, if the total concentration of these metal elements becomes too high, the hcp structure of the sputtered film may collapse, so the upper limit of the total concentration of these metal elements is preferably 40 mol% or less, more preferably 35 mol% or less, and even more preferably 30 mol% or less based on the overall composition of the target member. In addition, from the viewpoint of not bringing about unexpected changes in characteristics, it is preferable that the amount of metal components other than Mo is small.

Cr has a negative effect on maintaining the hcp structure of the metal phase, and since it is easy to reduce oxides such as CoO, there is a possibility that unintended constituent phases will be generated in the sputtered film. For this reason, the concentration of Cr in the metal phase is preferably 20 mol% or less, more preferably 10 mol% or less, even more preferably 5 mol% or less, and even more preferably 1 mol% or less, based on the overall composition of the target member.

As mentioned above, Ru increases production costs, so it is desirable to add a small amount. Therefore, the concentration of Ru in the metal phase is preferably 20 mol% or less, more preferably 10 mol% or less, even more preferably 5 mol% or less, and even more preferably 1 mol% or less, based on the overall composition of the target member.

Like Cr, B also easily reduces oxides such as CoO, and may generate unintended constituent phases in the sputtered film. For this reason, the concentration of B in the metal phase is preferably 20 mol% or less, more preferably 10 mol% or less, even more preferably 5 mol% or less, and even more preferably 1 mol% or less, based on the overall composition of the target member.

The total concentration of Cr, Ru and B in the metal phase is preferably 20 mol% or less, more preferably 10 mol% or less, even more preferably 5 mol% or less, and even more preferably 1 mol% or less, based on the overall composition of the target member.

2. Oxide Phase
In one embodiment of the sputtering target member for forming a nonmagnetic layer according to the present invention, the volume fraction of the oxide phase is 10 to 45%. By setting the lower limit of the volume fraction of the oxide phase to 10% or more, the effect of blocking magnetic interactions can be enhanced. The lower limit of the volume fraction of the oxide phase is preferably 20% or more, and more preferably 30% or more. The reason why the upper limit of the volume fraction of the oxide phase is set to 45% or less is that if the volume fraction of the oxide phase is greater than this, it becomes difficult to discharge during sputtering. The upper limit of the volume fraction of the oxide phase is preferably 40% or less, and more preferably 35% or less.

The volume fraction of the oxide phase in a sputtering target component is measured using the following procedure. Metal particle and oxide parts can be distinguished by the shade of color when observing the structure. For example, in structure observation using a SEM (scanning electron microscope), the intensity of secondary electrons appears as shades in the image, so metal parts generally appear bright due to the high intensity of secondary electrons, while oxides appear dark due to the low intensity. Using this, the average area fraction of the dark parts in the image is taken as the volume fraction of the oxide phase of the target. Here, we use the fact that the following relationship holds between the average area fraction and volume fraction of uniformly dispersed phases (Fundamentals and Applications of 3D Material Structure and Property Analysis, edited by Shinya Mitsuo, Appendix A1, Uchida Rokakuho, June 2014).

The oxides constituting the oxide phase include, but are not limited to, oxides of one or more metals selected from the group consisting of Ti, Si, B, Co, Cr, Ta, Mn, Zr and Nb. The oxides constituting the oxide phase may be one type or two or more types may be mixed.

As the oxide of titanium, _TiO2 , TiO, etc. can be used. As the oxide of silicon, _SiO2 , SiO, etc. can be used. As the oxide of _boron , _B2O3 , BO, _B2O , _{B6O ,} etc. can be used. As the oxide of cobalt, CoO, _Co2O3 , _Co3O4 , etc. can be used. As the oxide of chromium, _Cr2O3 , _etc. can be used. As the oxide of tantalum, _TaO2 , _Ta2O5 , _etc. can be used. As the oxide of manganese, MnO, _MnO2 , _{Mn3O4 ,} etc. can be used. As the oxide of zirconium, _{Zr2O3 , etc.} can be used. As the oxide of niobium, NbO, _NbO2 , _Nb2O3 , _{Nb2O5 , etc.} can be used. Other oxides can also be used.

The oxide may be a composite oxide containing two or _more metal components. As the composite oxide, composite oxides having a relatively _high melting point such as _CrBO3 , _{Co2B2O5 , Co3B2O6} , _{Mn3B2O6 , TiBO3 , etc.} can be suitably used.

Among the above oxides, from the viewpoint of increasing the separation of the metal phase and the oxide phase in the sputtered film, the oxide of cobalt, which has excellent wettability with the Co constituting the metal phase, is preferred, and CoO is optimal. Therefore, the concentration of cobalt oxide in the oxide phase is preferably 50 mol% or more, and more preferably 70 mol% or more. Furthermore, the concentration of CoO in the oxide phase is preferably 50 mol% or more, and more preferably 70 mol% or more.

3. Relative Density
A high relative density of the sputtering target member is preferable for performing stable sputtering with less arcing. In one embodiment, the sputtering target member for forming a non-magnetic layer according to the present invention has a relative density of 90% or more. The relative density is preferably 95% or more, more preferably 99% or more. The relative density is determined by the ratio of the Archimedes density to the theoretical density determined by the composition. The theoretical density determined by the composition may exceed 100% because it does not take into account the density of compounds that actually exist.

The theoretical density is calculated from the mass concentration and the elemental density of each component obtained by performing a component analysis of the sputtering target material. Specifically, it is the density when it is assumed that the components of the target are mixed together without diffusing or reacting with each other, and is calculated by the following formula.
Formula: theoretical density (g/cm ³ )=Σ(molecular weight of component×molar ratio of component)/Σ(molecular weight of component×molar ratio of component/literature density of component)
Here, Σ means taking the sum over all of the components of the target.

(4. Manufacturing Method)
The sputtering target member for forming a nonmagnetic layer according to the present invention can be produced by a powder sintering method, for example, by the following procedure.

First, one or more types of metal powder are prepared according to the composition of the desired metal phase. The metal powder may be a simple metal powder such as Co powder, Pt powder, Mo powder, Cr powder, Ru powder, or B powder, or an alloy powder such as Co-Pt alloy powder. The metal powder may be produced by pulverizing a melted and cast ingot, or may be produced by gas atomization.

The median diameter of each metal powder is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more. If the metal powder is too small, the powders will aggregate with each other, making it difficult to obtain a uniform structure. However, if the median diameter of each metal powder is too large, it is difficult to mix uniformly with the oxide powder and there is a concern that it may cause particles during sputtering, so it is preferably 150 μm or less, more preferably 30 μm or less, and even more preferably 10 μm or less. The median diameter can be adjusted by crushing or sieving.

Also, one or more types of oxide powders are prepared according to the composition of the desired oxide phase. From the viewpoint of easy uniform dispersion, the median diameter is preferably 30 μm or less, more preferably 10 μm or less, and even more preferably 5 μm or less. Also, from the viewpoint of preventing aggregation of the powders, the oxide powder preferably has a median diameter of 0.1 μm or more, more preferably 1 μm or more, and even more preferably 2 μm or more.

In this specification, the median diameter of a powder refers to the particle size at 50% cumulative volume (D50) in the particle size distribution determined by a laser diffraction/scattering method. In the examples, a HORIBA LA-920 particle size distribution measuring device was used, and the powder was dispersed in an ethanol solvent and measured by the wet method. The refractive index used was that of metallic cobalt.

Next, the raw powders (metal powder and oxide powder) are weighed to obtain the desired composition, and mixed while being pulverized using a known method such as a ball mill. At this time, it is desirable to seal an inert gas in the pulverization container to suppress oxidation of the raw powder as much as possible. Examples of the inert gas include Ar and _N2 gas. At this time, in order to realize a uniform structure, it is preferable to pulverize the mixed powder until the median diameter is 20 μm or less, and more preferably 10 μm or less, and it can be pulverized until it is in the range of, for example, 0.1 to 10 μm. The mixed powder thus obtained is molded and sintered in a vacuum atmosphere or an inert gas atmosphere by a hot pressing method. In addition to the hot pressing method, various pressure sintering methods such as a plasma discharge sintering method can be used. In particular, hot isostatic sintering (HIP) is effective in improving the density of the sintered body, and it is preferable to carry out the hot pressing method and the hot isostatic sintering method in this order from the viewpoint of improving the density of the sintered body.

The holding temperature during sintering depends on the composition of the metal phase in order to avoid melting of the metal powder, but is preferably lower than the melting point of the metal used, more preferably at least 20°C lower than the melting point, and even more preferably at least 50°C lower than the melting point. In addition, the holding temperature during sintering is preferably 650°C or higher in order to avoid a decrease in the density of the sintered body, more preferably 700°C or higher, and even more preferably 750°C or higher.

The pressure for hot pressing is preferably 20 to 70 MPa to promote sintering. The pressure for hot isostatic sintering (HIP) is preferably 100 to 200 MPa to improve the density of the sintered body.

The sintering time is preferably 0.3 hours or more, more preferably 0.5 hours or more, and even more preferably 1.0 hour or more to improve the density of the sintered body. Also, the sintering time is preferably 3.0 hours or less, more preferably 2.0 hours or less, and even more preferably 1.5 hours or less to prevent the crystal grains from becoming coarse.

The sputtering target member according to the present invention can be produced by forming the obtained sintered body into a desired shape using a lathe or the like. There are no particular limitations on the target shape, but examples include a flat plate shape (including a disk shape or a rectangular plate shape) and a cylindrical shape.

There are no particular restrictions on the thickness of the sputtering target member and it may be set appropriately depending on the sputtering equipment used and the film formation time, but it is usually around 3 to 25 mm, typically around 6 to 18 mm.

The sputtering target member may be used as a sputtering target as it is, or may be joined to a backing plate or backing tube with brazing material as necessary. In this case, a sputtering target having a structure in which the sputtering target member and the backing plate or backing tube are laminated via a brazing material layer is provided. The material constituting the brazing material layer is not limited, but is preferably one or more selected from the group consisting of pure In, InSn alloy, and InZn alloy, since the melting point is lower than that of indium.

The thickness of the brazing material layer is not limited, but from the standpoint of the efficiency of use of the sputtering target and the prevention of cracks based on the thermal expansion buffering effect of the brazing material, it is preferably 0.1 mm to 2 mm, more preferably 0.1 mm to 1 mm, and even more preferably 0.3 mm to 0.8 mm.

(5. Film Formation)
In one aspect, the present invention provides a film formation method including a step of sputtering using the sputtering target member for forming a nonmagnetic layer according to the present invention. The sputtering conditions can be appropriately set.

In one embodiment, the sputtered film obtained by carrying out the above-mentioned film formation method has a saturation magnetization of 200 emu/cc or less, preferably 150 emu/cc or less, and more preferably 100 emu/cc or less. The saturation magnetization is a value measured by a vibrating sample magnetometer (VSM). In one embodiment, the sputtered film obtained by carrying out the above-mentioned film formation method has a full width at half maximum (FWHM) of a peak due to the (002) plane of the hcp structure CoPt alloy, which appears between 2θ = 42 ° and 44 °, when analyzed by XRD (X-ray diffraction method), of 5 or less, preferably 4 or less, and typically in the range of 3 to 5. This means that the hcp structure of the metal phase is maintained in the sputtered film.

The following examples of the present invention are presented together with comparative examples, but these examples are provided to provide a better understanding of the present invention and its advantages and are not intended to limit the invention.

<1. Raw material powder>
(1) The following metal raw material powders were prepared:
Co powder (median diameter: 3 μm), Cr powder (median diameter: 10 μm), Pt powder (median diameter: 1 μm), Mo powder (median diameter: 5 μm), B powder (median diameter: 5 μm)
(2) The following metal oxide powders were prepared:
_TiO2 powder (median diameter: 1 μm), _SiO2 powder (median diameter: 1 μm), CoO powder (median diameter: 2 μm)

Next, each raw material powder was weighed so that the raw material composition was according to the test number shown in Table 1, and was put into a 10-liter ball mill pot together with SUS balls as a grinding medium, and mixed and ground by rotating in an Ar atmosphere for 8 hours. The median diameter of the powder after mixing and grinding was measured to be about 3 μm. Next, the powder removed from the pot was filled into a carbon mold, molded and sintered using a hot press device. The hot press conditions were a vacuum atmosphere, a heating rate of 300°C/hour, a holding temperature of 1000°C, and a holding time of 2 hours, and pressure was applied at 30 MPa from the start of heating to the end of temperature holding. After the holding time was completed, the powder was allowed to cool naturally in the chamber. Next, the sintered body removed from the hot press mold was subjected to hot isostatic sintering (HIP). The conditions of hot isostatic sintering were heating temperature 300°C/hour, holding temperature 950°C, holding time 2 hours, and the gas pressure of Ar gas was gradually increased from the start of heating, and pressurized at 150 MPa while holding at 950°C. After the temperature holding was completed, the sintered bodies were naturally cooled in the furnace. Next, using a lathe, each sintered body was cut into a shape of 180.0 mm in diameter and 5.0 mm in thickness to obtain a disk-shaped sputtering target member. A sufficient number of sputtering target members according to each test example were prepared to carry out the following tests.

2. Organizational Analysis
For each sputtering target member obtained by the above procedure, a cut surface horizontal to the sputtering surface was cut out and mirror-polished. The mirror-polished cut surface was analyzed using FE-EPMA element mapping images. As a result, it was confirmed that each sputtering target member had a structure in which the metal phase and the oxide phase were mutually dispersed. From the FE-EPMA element mapping images, it was confirmed that for both the metal phase and the oxide phase, a particle phase with a composition corresponding to the raw material composition was present. The compositions of the metal phase and the oxide phase are shown in Table 2.

<3. Volume ratio of oxide phase>
The mirror-polished cut surface subjected to the structural analysis was imaged at a magnification of 3000 times using a Hitachi S-3700N SEM (scanning electron microscope). Next, the SEM image was binarized to black and white using software called ImageJ manufactured by the National Institutes of Health to identify the oxide phase (black part), and the ratio of the area of the oxide phase to the area of the entire SEM image was determined. The measurement was performed three times, and the average value was used as the measured value of the volume fraction of the oxide phase. The binarization procedure is as follows.
Load the image from File → Open. Select 8-bit from Image → Type. Select the unscaled portion of the image and cut out the scaled portion with Image → Crop. Select Process → Filters → Gaussian Blur, enter 2 for Sigma, and click OK. Select Process → Binary → Make Binary. The image is binarized using the above steps.

<4. Relative Density>
The density of each sputtering target member according to the test example obtained by the above manufacturing method was measured by Archimedes' method, and the ratio (%) to the theoretical density determined by the composition was calculated as the relative density. The results are shown in Table 3.

5. Strength
The sputtering target members according to the respective test examples obtained by the above manufacturing method were visually inspected for the presence or absence of cracks. The results are shown in Table 3.

<6. Film formation test>
The sputtering target members according to the respective test examples obtained by the above manufacturing procedure were attached to a magnetron sputtering device (Canon Anelva C-3010 sputtering system) and sputtering was carried out. The sputtering conditions were an input power of 1 kW, an Ar gas pressure of 1.7 Pa, and a film was formed on a silicon substrate for 20 seconds.

<7. XRD analysis>
The sputtered films according to the test examples obtained in the film formation test were analyzed by XRD (X-ray diffraction method) under the following measurement conditions: The positions of the diffraction peaks were measured by high-angle XRD measurement, and the full width at half maximum (FWHM) was measured by rocking curve measurement.
Analyzer: High-resolution X-ray thin film evaluation device Superlab manufactured by Rigaku Co., Ltd.
High angle XRD measurement tube: Cu (measured with CuKα)
Tube voltage: 40 kV
Tube current: 20mA
Optical system: 2D focusing multilayer mirror Scan mode: 2θ/θ
Scanning range (2θ): 10° to 100°
Measurement step (2θ): 0.1°
Measurement sample size: approx. 10mm x 10mm
Rocking curve measurement Tube: Cu (measured with CuKα)
Tube voltage: 40 kV
Tube current: 20mA
Optical system: 2-dimensional focusing multilayer mirror Scan mode: θ only Scan range (θ): ±10° from the peak position of the (002) plane identified by high-angle XRD
Measurement step (2θ): 0.2°
Measurement sample size: approx. 10mm x 10mm

The obtained XRD profile was analyzed using Rigaku Corporation's integrated powder X-ray analysis software PDXL. The obtained measurement data was subjected to BG removal, Kα2 removal, and peak search in automatic mode to identify the position of the diffraction peak due to the (002) plane of the hcp structure CoPt alloy, which appears between 2θ = 42° and 44°, and also to measure the full width at half maximum (FWHM) of the peak. The presence of the peak means that the (002) plane appears parallel to the measurement surface, i.e., the C-axis of the hcp structure is perpendicular to the sputtered film. The results are shown in Table 3.

8. Magnetic Measurements
For the sputtered films of each test example obtained in the film formation test, magnetic measurements were performed using a VSM (Tamagawa Seisakusho, Model TM-VSM261483-HGC) to measure the saturation magnetization. The results are shown in Table 3. If the saturation magnetization of the sputtered film is 200 emu/cc or less, it can be expected to be used as a non-magnetic layer.

<9. TEM Observation>
The sputtered films of Example 1, Comparative Example 8, and Comparative Example 9 obtained in the film formation test were subjected to structure observation (magnification: ×40,000) using a JEOL transmission electron microscope (TEM). The average particle size and standard deviation of the metal phase particles were then measured by image analysis. The results are shown in Table 4. It can be seen from Table 4 that sputtered films having a fine structure comparable to that obtained when Mo was used instead of Ru were obtained.

10. Discussion
In Comparative Example 1, the metal phase was composed of Co, Cr, and Pt, and did not contain Mo, so it was not possible to form a film while maintaining the hcp structure with good crystallinity (this can be confirmed by the large half-value width).
In Comparative Example 2, the metal phase was composed of Co, Pt and Ru, the sputtered film was made nonmagnetic, and the hcp structure was maintained, but the cost of the raw material Ru was high, which raised a problem in terms of economy.
In Comparative Example 3, the metal phase was composed of Co, B, and Pt, and did not contain Mo, so it was not possible to form a film while maintaining the hcp structure with good crystallinity (this can be confirmed by the large half-value width).
Comparative Examples 4 to 7 contained Mo, but the total concentration of Mo, Cr, Ru and B was insufficient, so that the saturation magnetization of the sputtered films was high.
In Comparative Example 8, the Mo concentration in the metal phase was too high, so that the sputtering target member became embrittled and cracked.
In Comparative Example 9, the metal phase was composed of Co, Cr, and Pt, and did not contain Mo. In addition, Cr and CoO were used simultaneously, which resulted in the formation _{of Cr2O3} instead of CoO. As a result, the metal phase could not be separated well in the oxide phase, and some of the metal phase particles became coarse. This can be confirmed by the fact that the standard deviation of the particle size of the metal phase after film formation became large.
In Comparative Example 10, the metal phase was composed of Co, Pt and Ru, the sputtered film was made nonmagnetic, and the hcp structure was maintained, but the raw material cost of Ru was high, which raised economic problems.
In Comparative Example 11, the metal phase was composed of Co, Pt, and B, and Mo was not included. Also, B and CoO were used simultaneously, which resulted in the formation of _B2O3 instead of _CoO . As a result, the metal phase could not be separated well in the oxide phase, and some of the metal phase particles became coarse. This can be confirmed by the fact that the standard deviation of the particle size of the metal phase after the film formation became large.
On the other hand, in the embodiment 1 to 10, the composition in the metal phase is more appropriate than that in the comparative example, so that the sputtered film becomes non-magnetic and can maintain the hcp structure.In addition, by reducing the concentration of Ru in the metal phase, the economic efficiency is improved.

Claims (13)

A sputtering target member for forming a nonmagnetic layer, the sputtering target member having a structure in which a metal phase and an oxide phase are mutually dispersed,
The metal phase contains, based on the overall composition of the target member, 20 to 60 mol % Co, 5 to 30 mol % Pt, and 1 to 40 mol % Mo, and also contains Mo, Cr, Ru, and B in a total concentration of 25 mol % or more;
The volume fraction of the oxide phase is 10 to 45%.
A sputtering target member for forming a non-magnetic layer. 2. The sputtering target member for forming a nonmagnetic layer according to claim 1, wherein the metal phase contains 15 to 40 mol % of Mo based on the overall composition of the target member. 3. The sputtering target member for forming a nonmagnetic layer according to claim 1, wherein the concentration of Cr in the metal phase is 10 mol % or less based on the overall composition of the target member. The sputtering target member for forming a nonmagnetic layer according to any one of claims 1 to 3, wherein the concentration of Ru in the metal phase is 5 mol% or less based on the overall composition of the target member. The sputtering target member for forming a nonmagnetic layer according to any one of claims 1 to 4, wherein the concentration of B in the metal phase is 5 mol% or less based on the overall composition of the target member. The sputtering target member for forming a nonmagnetic layer according to any one of claims 1 to 5, wherein the oxide phase contains an oxide of one or more metals selected from the group consisting of Ti, Si, B, Co, Cr, Ta, Mn, Zr and Nb. The sputtering target member for forming a non-magnetic layer according to any one of claims 1 to 6, which has a relative density of 90% or more. 8. The sputtering target member for forming a nonmagnetic layer according to claim 1, wherein the metal phase contains 15 to 30 mol % of Pt based on the overall composition of the target member. 9. The sputtering target member for forming a nonmagnetic layer according to claim 1, wherein the metal phase contains 25 to 30 mol % of Mo based on the overall composition of the target member. 10. The sputtering target member for forming a nonmagnetic layer according to claim 1, wherein the concentration of Cr in the metal phase is 5 mol % or less based on the overall composition of the target member. 11. The sputtering target member for forming a nonmagnetic layer according to claim 1, wherein the total concentration of Cr, Ru and B in the metal phase is 10 mol % or less based on the overall composition of the target member. 12. A sputtering target having a structure in which the sputtering target member for forming a nonmagnetic layer according to claim 1 and a backing plate or a backing tube are laminated via a brazing material layer. A film forming method comprising a step of sputtering using the sputtering target member for forming a nonmagnetic layer according to any one of claims 1 to 11 .