JP2009293102A - Sputtering target for depositing vertical magnetic recording medium film with low relative permeability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sputtering target for depositing a vertical magnetic recording medium film with a low relative permeability for depositing a magnetic recording film applied to a high density magnetic recording medium of a hard disk, particularly for depositing a magnetic recording film applied to a vertical magnetic recording medium. <P>SOLUTION: The sputtering target is used for depositing a magnetic recording medium film having a componential composition comprising, by atom, 1 to 30% O, 2 to 20% Cr, 5 to 25% Pt and 0.5 to 15% M metal (M denotes any one selected from Si, Ti, Ta and Al), and the balance C with inevitable impurities. The sputtering target has a structure where a Co-Cr binary alloy phase whose surface is coated with an oxide layer of Co and Cr, an alloy layer of Pt and B and an oxide phase of M are uniformly dispersed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sputtering target for forming a perpendicular magnetic recording medium film having a low relative permeability for forming a magnetic recording film applied to a high-density magnetic recording medium of a hard disk, particularly a magnetic recording film applied to a perpendicular magnetic recording medium. It is about.

Hard disk devices are generally used as external recording devices such as computers and digital home appliances, and further improvement in recording density is required. Therefore, in recent years, a perpendicular magnetic recording system that can realize ultra-high density recording has attracted attention. Unlike the conventional in-plane recording system, this perpendicular magnetic recording system is said to have a stable recording magnetization as the density increases in principle, and has already been put into practical use. A CoCrPt—SiO ₂ granular magnetic recording film has been proposed as a promising candidate for a material to be applied to the recording layer of the perpendicular magnetic recording type hard disk medium, and the CoCrPt—SiO ₂ granular magnetic recording film is a Co containing Cr and Pt. It is known to produce by a magnetron sputtering method using a sputtering target having a mixed phase of a base sintered alloy phase and a silicon dioxide phase (see Non-Patent Document 1).
This sputtering target usually contains silicon dioxide powder, Cr powder, Pt powder and Co powder containing silicon dioxide: 0.5 to 15 atomic%, Cr: 4 to 20 atomic%, Pt: 5 to 25 atomic%. The remainder: It is known to be prepared by mixing and mixing so as to have a composition consisting of Co, and then vacuum hot pressing or hot isostatic pressing, and in addition, a commercially available Co base containing Cr and Pt. Co-based alloy powder containing Cr and Pt and silicon dioxide powder prepared by rapid solidification by alloy powder or silicon dioxide powder: silicon dioxide: 0.5 to 15 atomic%, Cr: 4 to 20 atomic%, Pt: 5 to 25 atomic% It is known that it is prepared by blending and mixing so as to have a composition consisting of Co: balance: Co, and then vacuum hot pressing or hot isostatic pressing (Patent Document 1). See, eg, Patent Document 2).
In addition to silicon dioxide, nonmagnetic oxidation such as TiO, Cr ₂ O ₃ , TiO ₂ , Ta ₂ O ₅ , Al ₂ O ₃ , BeO ₂ , MgO, ThO ₂ , ZrO ₂ , CeO ₂ , Y ₂ O _3, etc. It is known that products can be used (see Patent Documents 3 and 4).
Therefore, the component composition of the target for forming the recording layer of the perpendicular magnetic recording type hard disk medium is as follows: O: 1 to 30 atomic%, Cr: 2 to 20 atomic%, Pt: 5 to 25 atomic%, M metal ( However, it is known that M metal contains any one of Si, Ti, Ta, and Al): 0.5 to 15 atomic%, and has a component composition consisting of the balance: Co and inevitable impurities. .
“Fuji Times” Vol. 75No. 3 2002 (pages 169-172) Japanese Patent Laid-Open No. 2001-236643 JP 2004-339586 A JP 2003-36525 A JP 2006-24346 A

This conventional sputtering target for forming a magnetic recording medium film is based on a Co-based alloy containing Cr and Pt, which are ferromagnetic alloys, in which SiO ₂ , TiO ₂ , Ta ₂ O ₅ , Al ₂ O _3, etc. Since the nonmagnetic oxide has a uniformly dispersed structure, the proportion of magnetic flux passing through the inside of the target is larger than that of the nonmagnetic target, and the magnetic flux leaking over the target is extremely small. This is for magnetron sputtering, which has a magnetic circuit placed under the target and stabilizes the discharge by increasing the ionization efficiency of the noble gas by utilizing the magnetic flux leaking over the target, thereby improving the deposition rate. It becomes a big problem. In other words, if magnetron sputtering is performed using a target with a low leakage magnetic flux density (ie, a target with high relative permeability) that has a small amount of magnetic flux leaking over the target, the deposition rate is stable even if the discharge is not stable or can be discharged. This causes problems such as extremely slowing down.
Also, a target with a low leakage magnetic flux density is such that once erosion is formed by magnetron sputtering, magnetic flux leaks intensively from the erosion part, and only that part is intensively sputtered. It tends to cause problems such as a decrease in utilization efficiency, a change in deposition rate over time, a variation in film thickness within the substrate surface, and a large amount of redeposition film deposited on the target.

Therefore, the present inventors have studied to obtain a sputtering target for forming a magnetic recording medium film having a lower relative permeability.
As a result, a Co—Cr binary alloy powder, a Pt powder, and an M oxide powder coated with a Co and Cr oxide layer on the surface were prepared as raw material powders. %, Cr: 2 to 20 atomic%, Pt: 5 to 25 atomic%, M (however, M is any one of Si, Ti, Ta and Al): 0.5 to 15 atomic% The remainder: a sputtering target for forming a magnetic recording medium film obtained by mixing and mixing so as to have a component composition composed of Co and inevitable impurities, and vacuum hot pressing the obtained mixed powder is made of Co and Cr A target having a structure dispersed as a Co—Cr binary alloy phase coated with an oxide layer, a Pt phase, and an M metal oxide phase is obtained, and the target having this structure is a conventional sputter for forming a magnetic recording medium film. The research result that the relative permeability is further reduced compared to the talling target was obtained.

This invention was made based on these research results,
(1) O: 1 to 30 atomic%, Cr: 2 to 20 atomic%, Pt: 5 to 25 atomic%, M metal: 0.5 to 15 atomic%, and the balance: Co and inevitable impurities In a sputtering target for forming a magnetic recording medium film having a composition, a Co—Cr binary alloy phase whose surface is coated with a Co and Cr oxide layer, a Pt phase, and an M oxide phase are uniformly dispersed And a sputtering target for forming a perpendicular magnetic recording medium film having a low relative magnetic permeability.

By using a Co—Cr binary alloy powder having a Co and Cr oxide layer coated on the surface as a raw material powder, a Co—Cr binary alloy in which the Co and Cr oxide layers are Pt during hot pressing. It is considered that the relative permeability of the entire target is lowered in order to prevent diffusion penetration into the phase and prevent an increase in the relative permeability of the Co—Cr binary alloy phase. The oxide layer of Co and Cr formed on the surface of the Co—Cr binary alloy phase has the base Pt diffused and penetrated into the outer periphery of the Co—Cr binary alloy phase. The thickness of the oxide layer of Co and Cr is more preferably 5 nm or more because it has an effect of preventing the increase of the relative magnetic permeability, but if the thickness exceeds 300 nm, abnormal discharge is caused. Therefore, the thickness of the Co and Cr oxide layers formed on the surface of the Co—Cr binary alloy phase is more preferably in the range of 5 to 300 nm.

In order to produce a sputtering target for forming a perpendicular magnetic recording medium film having a low relative magnetic permeability according to the present invention, a Co—Cr binary alloy powder coated with a Co and Cr oxide layer on its surface as a raw material powder, Pt powder, and M oxide powders are prepared, and these raw material powders are divided into O: 1 to 30 atomic%, Cr: 2 to 20 atomic%, Pt: 5 to 25 atomic%, M (where M is Si, Ti, Ta, Any one of Al): 0.5 to 15 atomic%, balance: blended so as to have a component composition consisting of Co and inevitable impurities, mixed, and the obtained mixed powder is vacuum hot pressed It is manufactured by doing.

The Co—Cr binary alloy powder coated with the Co and Cr oxide layers on the surface, which is one of the raw material powders, contains Cr: 4.2 to 33.3 atomic%, with the balance being Co. The Co—Cr binary alloy powder having the composition can be produced by performing a heat treatment in the atmosphere at a temperature of 150 to 350 ° C. for 0.5 to 2 hours.
Therefore, the Co—Cr binary alloy phase in which the surface dispersed in the substrate of the sputtering target for forming a perpendicular magnetic recording medium film having a low relative permeability according to the present invention is coated with an oxide layer of Co and Cr is also Cr: It has a composition containing 4.2 to 33.3 atomic%, with the balance being Co. The composition of the Co-Cr binary alloy powder coated with the Co and Cr oxide layers on this surface and the Co-Cr oxide layer formed on the surface uniformly dispersed in the substrate The component composition of the binary alloy phase is determined by the component composition of the sputtering target for forming a perpendicular magnetic recording medium film having a low relative magnetic permeability according to the present invention. The Co—Cr binary alloy raw material powder used for producing the Co—Cr binary alloy powder coated on the surface with an oxide layer of Co and Cr has a 50% particle size (D ₅₀ ) of 5 to 40 μm. Are preferably used.

  When the sputtering target for forming a perpendicular magnetic recording medium film having a low relative magnetic permeability according to the present invention is used, magnetron sputtering can be performed efficiently, which can greatly contribute to the development of industries such as computers and digital home appliances.

As a raw material powder, a Co—Cr binary alloy powder having an average particle diameter of 20 μm having the component composition shown in Table 1 is prepared, and the Co—Cr binary alloy powder is heat-treated under the conditions shown in Table 1. Thus, oxide film-coated Co—Cr binary alloy powders A to D having Co and Cr oxide layers on the surface of the Co—Cr binary alloy powder were produced. Furthermore, a Pt powder having an average particle size of 25 μm, a Co powder having an average particle size of 5 μm, and a Cr powder having an average particle size of 15 μm are prepared. Further, as a non-magnetic oxide powder, both are SiO ₂ powder having an average particle size of 3 μm. TiO ₂ powder, Ta ₂ O ₅ powder and Al ₂ O ₃ powder were prepared.

Example 1
The oxide film-coated Co—Cr binary alloy powder A in Table 1 is blended with Pt powder and SiO ₂ powder, and the obtained blended powder is put into a 10-liter container together with zirconia balls as a grinding medium. The atmosphere was replaced in an Ar gas atmosphere, and then the container was sealed. This container was rotated with a ball mill for 12 hours to produce a mixed powder. The obtained mixed powder was filled in a vacuum hot press apparatus and vacuum hot pressed in a vacuum atmosphere under conditions of temperature: 1100 ° C., pressure: 35 MPa, and 3 hours to prepare a plate-like hot press body. The component composition of this plate-like hot press body was measured with a fluorescent X-ray analyzer, and the results are shown in Table 2. Furthermore, by cutting this plate-like hot press body, the target 1 of the present invention having a diameter of 152.4 mm and a thickness of 5 mm is produced, and the target 1 of the present invention is further cut, and its cut surface Was observed by an electron microprobe analyzer (EPMA) surface analysis method, and the structure was shown in Table 2.
Furthermore, the maximum relative magnetic permeability in the in-plane direction of the target 1 of the present invention was measured, and the results are shown in Table 2.

Conventional example 1
The previously prepared Co powder, Cr powder, Pt powder and SiO ₂ powder are blended, and the blended powder obtained is put into a 10 liter container together with zirconia balls as a grinding medium, and the atmosphere in this container is an Ar gas atmosphere Replaced in, then sealed the container. This container was rotated with a ball mill for 16 hours to produce a mixed powder. The obtained mixed powder was filled in a vacuum hot press apparatus and vacuum hot pressed in a vacuum atmosphere under conditions of temperature: 1100 ° C., pressure: 35 MPa, and 3 hours to prepare a plate-like hot press body. The component composition of this plate-like hot press body was measured with a fluorescent X-ray analyzer, and the results are shown in Table 2.
By cutting this plate-like hot press body, a conventional target 1 having a diameter of 152.4 mm and a thickness of 5 mm is produced, the conventional target 1 is cut, and the cut surface is an electron beam microprobe. Table 2 shows the structure observed by the surface analysis method of an analyzer (EPMA). Furthermore, the maximum relative permeability in the target in-plane direction of this conventional target 1 was measured, and the result is shown in Table 2.

Example 2
The oxide film-coated Co—Cr binary alloy powder B, Pt powder and TiO ₂ powder shown in Table 1 were blended, and the resulting blended powder was put into a 10-liter container together with zirconia balls serving as a grinding medium. The atmosphere was replaced in an Ar gas atmosphere, and then the container was sealed. This container was rotated with a ball mill for 16 hours to produce a mixed powder. The obtained mixed powder was filled into a vacuum hot press apparatus, and a plate-like hot press body was produced by vacuum hot pressing in a vacuum atmosphere under conditions of temperature: 950 ° C., pressure: 35 MPa, and 3 hours. The component composition of this plate-like hot press body was measured with a fluorescent X-ray analyzer, and the results are shown in Table 2.
By cutting this plate-like hot press body, the target 2 of the present invention having a diameter of 152.4 mm and a thickness of 5 mm is produced, and the target 2 of the present invention is further cut. Observation was made by the surface analysis method of a line microprobe analyzer (EPMA), and the structure was shown in Table 2. Furthermore, the maximum relative magnetic permeability in the target in-plane direction of this inventive target 2 was measured, and the results are shown in Table 2.

Conventional example 2
The previously prepared Co powder, Cr powder, Pt powder and TiO ₂ powder were blended, and the blended powder obtained was put into a 10-liter container together with zirconia balls as a grinding medium, and the atmosphere in this container was replaced with an Ar gas atmosphere Replaced in, then sealed the container. This container was rotated with a ball mill for 16 hours to produce a mixed powder. The obtained mixed powder was filled into a vacuum hot press apparatus, and a plate-like hot press body was produced by vacuum hot pressing in a vacuum atmosphere under conditions of temperature: 950 ° C., pressure: 35 MPa, and 3 hours. The component composition of this plate-like hot press body was measured with a fluorescent X-ray analyzer, and the results are shown in Table 2.
By cutting this plate-like hot press body, a conventional target 2 having a diameter of 152.4 mm and a thickness of 5 mm is produced, the conventional target 2 is further cut, and the cut surface is cut into an electron microbeam. The surface was observed by a probe analyzer (EPMA) surface analysis method, and the structure was shown in Table 2. Further, the maximum relative magnetic permeability in the target in-plane direction of this conventional target 2 was measured, and the results are shown in Table 2.

Example 3
The oxide film-coated Co—Cr binary alloy powder C, Pt powder and Ta ₂ O ₅ powder in Table 1 were blended, and the resulting blended powder was put into a 10-liter container together with zirconia balls serving as a grinding medium. The atmosphere in the container was replaced with an Ar gas atmosphere, and then the container was sealed. This container was rotated with a ball mill for 16 hours to produce a mixed powder. The obtained mixed powder was filled into a vacuum hot press apparatus, and a plate-like hot press body was produced by vacuum hot pressing in a vacuum atmosphere under conditions of temperature: 1120 ° C., pressure: 35 MPa, and holding for 3 hours. The component composition of this plate-like hot press body was measured with a fluorescent X-ray analyzer, and the results are shown in Table 2.
By cutting this plate-like hot press body, the target 3 of the present invention having a diameter of 152.4 mm and a thickness of 5 mm was produced, the target 3 of the present invention was cut, and the cut surface was converted to an electron beam. The structure was observed by a surface analysis method using a microprobe analyzer (EPMA). Furthermore, the maximum relative magnetic permeability in the in-plane direction of this target 3 of the present invention was measured, and the results are shown in Table 2.

Conventional example 3
The previously prepared Co powder, Cr powder, Pt powder, and Ta ₂ O ₅ powder are blended, and the obtained blended powder is put into a 10-liter container together with zirconia balls as a grinding medium, and the atmosphere in the container is changed to Ar. After replacing in a gas atmosphere, the container was sealed. This container was rotated with a ball mill for 16 hours to produce a mixed powder. The obtained mixed powder was filled into a vacuum hot press apparatus, and a plate-like hot press body was produced by vacuum hot pressing in a vacuum atmosphere under conditions of temperature: 1120 ° C., pressure: 35 MPa, and holding for 3 hours. The component composition of this plate-like hot press body was measured with a fluorescent X-ray analyzer, and the results are shown in Table 2.
By cutting this plate-like hot press body, a conventional target 3 having dimensions of diameter: 152.4 mm and thickness: 5 mm is produced, and further, this conventional target 3 is cut, and the cut surface is converted into an electron microbeam. The surface was observed by a probe analyzer (EPMA) surface analysis method, and the structure was shown in Table 2. Further, the maximum relative magnetic permeability in the target in-plane direction of this conventional target 3 was measured, and the results are shown in Table 2.

Example 4
The oxide film-coated Co—Cr binary alloy powder D, Pt powder, and Al ₂ O ₃ powder shown in Table 1 were blended, and the obtained blended powder was put into a 10-liter container together with zirconia balls as a grinding medium. The atmosphere in the container was replaced with an Ar gas atmosphere, and then the container was sealed. This container was rotated with a ball mill for 16 hours to produce a mixed powder. The obtained mixed powder was filled into a vacuum hot press apparatus, and a plate-like hot press body was produced by vacuum hot pressing in a vacuum atmosphere under conditions of temperature: 1050 ° C., pressure: 35 MPa, and 3 hours. The component composition of this plate-like hot press body was measured with a fluorescent X-ray analyzer, and the results are shown in Table 2.
By cutting this plate-like hot press body, the target 4 of the present invention having a diameter of 152.4 mm and a thickness of 5 mm was produced, and the target 4 of the present invention was further cut. Observation was made by the surface analysis method of a line microprobe analyzer (EPMA), and the structure was shown in Table 2. Furthermore, the maximum relative magnetic permeability in the in-plane direction of the target 4 of the present invention was measured, and the results are shown in Table 2.

Conventional example 4
The previously prepared Co powder, Cr powder, Pt powder, and Al ₂ O ₃ powder are blended, and the resulting blended powder is put into a 10 liter container together with zirconia balls as a grinding medium, and the atmosphere in the container is Ar. After replacing in a gas atmosphere, the container was sealed. This container was rotated with a ball mill for 16 hours to produce a mixed powder. The obtained mixed powder was filled into a vacuum hot press apparatus, and a plate-like hot press body was produced by vacuum hot pressing in a vacuum atmosphere under conditions of temperature: 1050 ° C., pressure: 35 MPa, and 3 hours. The component composition of this plate-like hot press body was measured with a fluorescent X-ray analyzer, and the results are shown in Table 2. By cutting this plate-like hot press body, a conventional target 4 having a diameter of 152.4 mm and a thickness of 5 mm is produced, the conventional target 4 is cut, and the cut surface is used as an electron beam microprobe. The structure was observed by the surface analysis method of an analyzer (EPMA). Further, the maximum relative magnetic permeability in the target in-plane direction of this conventional target 4 was measured, and the results are shown in Table 2.

From the results shown in Tables 1 and 2, even though the composition of the present invention target 1 and the conventional target 1 are substantially the same, a Co—Cr binary alloy in which an oxide layer of Co and Cr is coated in the substrate The target 1 of the present invention in which the phases are uniformly dispersed has a smaller magnetic permeability than the conventional target 1 and thus has a large leakage magnetic flux density during sputtering. Therefore, the target 1 of the present invention is more efficient than the conventional target 1. It can be seen that sputtering can be performed.
Similarly, even though the present invention targets 2 to 4 and the conventional targets 2 to 4 have substantially the same component composition, the Co—Cr binary alloy phase in which the Co and Cr oxide layers are coated in the substrate is formed. Since the present invention targets 2 to 4 which are uniformly dispersed are smaller in relative permeability than the conventional targets 2 to 4, respectively, the leakage magnetic flux density is large during sputtering. Therefore, the present invention targets 2 to 4 are each the conventional target. It can be seen that sputtering can be performed more efficiently than 2-4.

Claims (1)

O: 1 to 30 atom%, Cr: 2 to 20 atom%, Pt: 5 to 25 atom%, M metal (however, M metal is any one of Si, Ti, Ta, and Al): 0. In a sputtering target for forming a magnetic recording medium film containing 5 to 15 atomic% and the balance: Co and inevitable impurities, a Co—Cr binary system whose surface is coated with an oxide layer of Co and Cr A sputtering target for forming a perpendicular magnetic recording medium film having a low relative permeability, characterized by having a structure in which an alloy phase, a Pt phase, and an M oxide phase are dispersed.