JP2009001861A - Sputtering target for forming a perpendicular magnetic recording medium film having a low relative permeability - Google Patents

Abstract

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. provide.
Nonmagnetic oxide: 0.5 to 15 mol%, Cr: 4 to 20 mol%, Pt: 5 to 25 mol%, B: 0.5 to 8 mol%, balance: Co and A sputtering target having a component composition consisting of inevitable impurities, the sputtering target having a structure in which a Co—Cr—B ternary alloy phase is uniformly dispersed in a substrate.
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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, silicon dioxide: 0.5 to 15 mol%, Cr: 4 to 20 mol%, Pt: 5 to 25 mol%. 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 and silicon dioxide powder containing Cr and Pt prepared by alloy solidification or rapid solidification, silicon dioxide: 0.5-15 mol%, Cr: 4-20 mol%, Pt: 5-25 mol% It is known that it is prepared by mixing and mixing so as to have a composition comprising Co: balance: Co, and then vacuum hot pressing or hot isostatic pressing. (See Patent Document 1, Patent Document 2, etc.).
Furthermore, the silicon dioxide: 0.5 to 15 mol%, Cr: 4 to 20 mol%, Pt: 5 to 25 mol%, and the balance: Co is added to the composition consisting of Co: B: 0.5 to 8 mol% In addition to the silicon dioxide, a target having a composition containing TiO, Cr ₂ O ₃ , TiO ₂ , Ta ₂ O ₅ , Al ₂ O ₃ , BeO ₂ , MgO, ThO is also known. It is also known that nonmagnetic oxides such as ₂ , ZrO ₂ , CeO ₂ and Y ₂ O ₃ can be used (see Patent Documents 3 and 4).
“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 JP 2004-310910 A

However, this conventional sputtering target for forming a magnetic recording medium film uses a Co—Cr—Pt—B alloy containing ferromagnetic alloys such as Cr, Pt, and B, and non-magnetic oxidation such as SiO _{2 in the} substrate. Since the structure has a uniformly dispersed structure, the proportion of magnetic flux passing through the inside of the target is larger than that of the non-magnetic target, and the amount of 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 having a low leakage magnetic flux density (ie, a target having a high relative permeability) with a small amount of magnetic flux leaking over the target, the deposition rate is extremely high even if the discharge is not stable or can be discharged. This is because it causes problems such as slowness.
As one of means for solving this problem, a method is adopted in which the thickness of the target is reduced so that the magnetic flux easily escapes over the target. However, if the target is made thin, the replacement frequency of the target becomes frequent, so that the film formation efficiency is deteriorated, which is not preferable in terms of cost.
In addition, a target with low leakage magnetic flux density is once the erosion is formed by performing 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 having a low relative permeability without reducing the thickness of the target. As a result, nonmagnetic oxide: 0.5 to 15 mol%, Cr: 4 to 20 mol%, Pt: 5 to 25 mol%, B: 0.5 to 8 mol%, balance: Co and unavoidable Ferromagnetic components Co and Cr contained in a sputtering target having a component composition composed of impurities are dispersed so as to form a Co—Cr—B ternary alloy phase, and Pt and nonmagnetic oxide are further dispersed into Pt phase and nonmagnetic. A target having a structure composed of a Co—Cr—B ternary alloy phase, a Pt phase, and a nonmagnetic oxide phase dispersed as an oxide phase was measured, and the relative permeability of the target was measured. I got the knowledge that it was obtained.

This invention was made based on these findings,
(1) Nonmagnetic oxide: 0.5 to 15 mol%, Cr: 4 to 20 mol%, Pt: 5 to 25 mol%, B: 0.5 to 8 mol%, balance: Co and inevitable A sputtering target having a component composition comprising impurities, the sputtering target having a structure in which a Co—Cr—B ternary alloy phase, a Pt phase, and a nonmagnetic oxide phase are uniformly dispersed in a substrate. It is characterized by a sputtering target for forming a perpendicular magnetic recording medium film having a low magnetic susceptibility.

In the Co—Cr—B ternary alloy phase of the sputtering target described in (1), Pt and B of the base material diffuse and penetrate into the outer periphery of the Co—Cr—B ternary alloy phase during hot pressing, and Co— The outer periphery of the Cr—B ternary alloy phase may be coated with a diffusion layer composed of Co, Cr, Pt and B. It is preferable that this diffusion layer is not present. However, if this diffusion layer is extremely thin, it does not significantly affect the characteristics, and Co is formed on the outer periphery of the Co—Cr—B ternary alloy phase of the sputtering target described in (1). The case where a diffusion layer composed of Cr, Pt and B is formed is also included in the present invention. Therefore, the present invention
(2) The perpendicular magnetic recording medium having a low relative magnetic permeability according to (1), wherein the Co—Cr—B ternary alloy phase is covered with a diffusion layer composed of Co, Cr, Pt and B. It has the characteristics in the sputtering target for film formation.

The nonmagnetic oxide included in the sputtering target for forming a perpendicular magnetic recording medium film having a low relative magnetic permeability according to the present invention includes silicon dioxide, tantalum oxide, titanium oxide, aluminum oxide, magnesium oxide, thorium oxide, zirconium oxide, and cerium oxide. And yttrium oxide, which are already known.

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, Co—Cr—B ternary alloy powder, Pt powder and nonmagnetic oxide powder are prepared as raw powders. The raw material powder contains nonmagnetic oxide: 0.5 to 15 mol%, Cr: 4 to 20 mol%, Pt: 5 to 25 mol%, B: 0.5 to 8 mol%, the balance: Co and inevitable It mix | blends so that it may become a component composition which consists of impurities, it mixes, and it obtains by hot-pressing the obtained mixed powder at the temperature (700-1050 degreeC) lower than normal hot press temperature (1100 degreeC or more). This prevents the Co and Cr contained in the Co—Cr—B ternary alloy powder from diffusing into the base as much as possible during hot pressing, and the Pt of the base is further reduced to the Co—Cr—B ternary alloy phase. This is to prevent as much as possible from diffusing and entering.

The Co—Cr—B ternary alloy powder preferably contains Cr: 4.2 to 33.3 mol%, B: 0.5 to 13.3 mol%, with the balance being Co. Therefore, the Co—Cr—B ternary alloy phase 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 also Cr: 4.2 to 33.3 mol. %, B: 0.5 to 13.3 mol%, with the balance being Co. The component composition of the Co-Cr-B ternary alloy powder and the component composition of the Co-Cr-B ternary alloy phase uniformly dispersed in the substrate are the perpendicular magnetic recording medium film having a low relative permeability of the present invention. It is determined by the component composition of the forming sputtering target.

  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 raw material powders, the average particle size: 20 μm Co—Cr—B ternary alloy powders A to D having the composition shown in Table 1, average particle size: 25 μm Pt powder, average particle size: 5 μm B powder Co powder having an average particle diameter of 5 μm and Cr powder having an average particle diameter of 15 μm were prepared, and SiO ₂ powder, TiO ₂ powder, Ta ₂ O ₅ powder having an average particle diameter of 3 μm as nonmagnetic oxide powders. And Al ₂ O ₃ powder were prepared.

Example 1
Co—Cr—B ternary alloy powder A, Pt powder and SiO ₂ powder shown in Table 1 are made of Cr: 10.8%, Pt: 15.3%, SiO ₂ : 10.0%, B: 1. .5%, the balance is blended so as to have a component composition consisting of Co and inevitable impurities, 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 Was replaced in an Ar gas atmosphere, and then the vessel was sealed. 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 a plate-like hot press body was produced by vacuum hot pressing in a vacuum atmosphere under conditions of temperature: 900 ° C., pressure: 35 MPa, and 3 hours.
The target 1 of the present invention having a diameter of 152.4 mm and a thickness of 5 mm was produced by cutting the plate-like hot press body. Further cutting the invention the target 1, observation of the cut surface by a surface analysis of an electron beam microprobe analyzer (EPMA), Pt phase, the SiO ₂ phase and Co-Cr-B ternary alloy phase A uniformly dispersed structure was observed, and a diffusion layer was observed around the Co—Cr—B ternary alloy phase. The maximum relative magnetic permeability in the target in-plane direction was measured for the target 1 of the present invention, and the results are shown in Table 2.

Conventional example 1
Co powder, Cr powder, Pt powder, SiO ₂ powder and B powder prepared earlier are Cr: 10.8%, Pt: 15.3%, SiO ₂ : 10.0%, B: 1.5% It is blended so that the balance is a component composition comprising Co and inevitable impurities, 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 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.
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 was produced. Furthermore, when this conventional target 2 was cut and the cut surface was observed by an electron beam microprobe analyzer (EPMA) surface analysis method, the SiO ₂ particle phase was dispersed in the Co—Cr—Pt—B alloy phase. Some organizations were seen. The maximum relative permeability in the target in-plane direction of this conventional target 1 was measured, and the results are shown in Table 2.

Example 2
Co—Cr—B ternary alloy powder B, Pt powder, and TiO ₂ powder shown in Table 1 were changed to Cr: 13.4%, Pt: 15.3%, TiO ₂ : 9.0%, B: 6 Is mixed so that the balance is a component composition consisting of Co and inevitable impurities, 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 Was replaced in an Ar gas atmosphere, and then the vessel was sealed. 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 a plate-like hot press body was produced by vacuum hot pressing in a vacuum atmosphere under conditions of temperature: 900 ° C., pressure: 35 MPa, and 3 hours.
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 was produced. Further cutting the invention target 2, was observed with the cut surface in the surface analysis of the electron beam microprobe analyzer (EPMA), Pt phase, the TiO ₂ phase and Co-Cr-B ternary alloy phase A uniformly dispersed structure was observed, and a diffusion layer was observed around the Co—Cr—B ternary alloy phase. The maximum relative permeability in the target in-plane direction was measured for the target 2 of the present invention, and the results are shown in Table 2.

Conventional example 2
Co powder, Cr powder, Pt powder, TiO ₂ powder and B powder prepared earlier are Cr: 10.8%, Pt: 15.3%, TiO ₂ : 10.0%, B: 6.0% It is blended so that the balance is a component composition comprising Co and inevitable impurities, 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 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.
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 was produced. Furthermore, when this conventional target 2 was cut and the cut surface was observed by the surface analysis method of an electron beam microprobe analyzer (EPMA), TiO ₂ was uniformly dispersed in the Co—Cr—Pt—B alloy substrate. Organization was seen. The maximum relative permeability in the target in-plane direction of this conventional target 2 was measured, and the results are shown in Table 2.

Example 3
Co—Cr—B ternary alloy powder C, Pt powder and Ta ₂ O ₅ powder shown in Table 1 are Cr: 13.4%, Pt: 15.3%, Ta ₂ O ₅ : 4.0% , B: containing 3.5%, the balance is blended so as to have a component composition consisting of Co and inevitable impurities, and the resulting blended powder is 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 in 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: 900 ° C., pressure: 35 MPa, and 3 hours.
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. Further, the target 3 of the present invention was cut, and the cut surface was observed by an electron beam microprobe analyzer (EPMA) surface analysis method. As a result, a Pt phase, a Ta ₂ O ₅ phase and a Co—Cr—B ternary alloy were obtained. A phase was observed, and a diffusion layer was observed around the Co—Cr—B ternary alloy phase. The maximum relative permeability in the target in-plane direction of this target 6 of the present invention was measured, and the results are shown in Table 2.

Conventional example 3
Co powder, Cr powder, Pt powder, Ta ₂ O ₅ powder and B powder prepared earlier were Cr: 13.4%, Pt: 15.3%, Ta ₂ O ₅ : 4.0%, B: 3 .5%, the balance is blended so as to have a component composition consisting of Co and inevitable impurities, 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 Was replaced in an Ar gas atmosphere, and then the vessel was sealed. 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.
By cutting this plate-like hot press body, a conventional target 3 having a diameter of 152.4 mm and a thickness of 5 mm was produced. Furthermore, when this conventional target 3 was cut and the cut surface was observed by an electron beam microprobe analyzer (EPMA) surface analysis method, the Ta ₂ O ₅ particle phase was uniform in the Co—Cr—Pt—B alloy phase. A distributed organization was seen. The maximum relative permeability in the target in-plane direction of this conventional target 3 was measured, and the results are shown in Table 2.

Example 4
Co—Cr—B ternary alloy powder D, Pt powder, and Al ₂ O ₃ powder shown in Table 1 are Cr: 14.7%, Pt: 14.7%, Al ₂ O ₃ : 8.0% , B: 4.0%, with the balance being a component composition consisting of Co and unavoidable impurities, the resulting blended powder is 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 in 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: 900 ° C., pressure: 35 MPa, and 3 hours.
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. Further cutting the invention target 4, it was observed with the cut surface in the surface analysis of the electron beam microprobe analyzer (EPMA), Pt phase, _Al 2 _{O 3} phase and Co-Cr-B ternary alloy A phase was observed, and a diffusion layer was observed around the Co—Cr—B ternary alloy phase. The maximum relative permeability in the target in-plane direction of this target 4 of the present invention was measured, and the results are shown in Table 2.

Conventional example 4
Co powder, Cr powder, Pt powder, Al ₂ O ₃ powder, and B powder prepared earlier were Cr: 14.7%, Pt: 14.7%, Al ₂ O ₃ : 8.0%, B: 4 Is mixed so that the balance is a component composition consisting of Co and inevitable impurities, 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 Was replaced in an Ar gas atmosphere, and then the vessel was sealed. 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.
By cutting this plate-like hot press body, the conventional target 4 having a diameter of 152.4 mm and a thickness of 5 mm was produced. Further, when this conventional target 4 was cut and the cut surface was observed by a surface analysis method of an electron beam microprobe analyzer (EPMA), the Al ₂ O ₃ particle phase was uniform in the Co—Cr—Pt—B alloy phase. A distributed organization was seen. The maximum relative 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 Table 2, when the present invention target 1 and the conventional target 1 are compared, the component composition is the same, but the Pt phase, the nonmagnetic oxide phase SiO ₂ phase and the Co— surrounded by the diffusion layer. The target 1 of the present invention having a structure in which the Cr—B ternary alloy phase is uniformly dispersed is compared with the conventional target having a structure in which SiO ₂ particles are uniformly dispersed in the Co—Cr—Pt—B alloy substrate. It can be seen that the maximum relative magnetic permeability in the target in-plane direction is small, and therefore the leakage magnetic flux density is increased during sputtering, so that sputtering can be performed efficiently. Similarly, when the present invention target 2 and the conventional target 2, the present invention target 3 and the conventional target 3, and the present invention target 4 and the conventional target 4 are respectively compared, the present invention targets 2 to 4 are compared with the conventional targets 2 to 4. It can be seen that sputtering can be performed efficiently.

Claims (2)

Nonmagnetic oxide: 0.5 to 15 mol%, Cr: 4 to 20 mol%, Pt: 5 to 25 mol%, B: 0.5 to 8 mol%, balance: Co and inevitable impurities A sputtering target having a component composition, wherein the sputtering target has a structure in which a Co—Cr—B ternary alloy phase, a Pt phase, and a nonmagnetic oxide phase are uniformly dispersed in a substrate. A sputtering target for forming a perpendicular magnetic recording medium film having a low relative magnetic permeability. 2. The perpendicular magnetic recording with low relative permeability according to claim 1, wherein the Co-Cr-B ternary alloy phase is covered with a diffusion layer composed of Co, Cr, Pt and B. A sputtering target for forming a medium film.