JP2009001862A - Sputtering target for use in forming film of perpendicular magnetic recording medium having low relative magnetic permeability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sputtering target to be used in forming a film of a perpendicular magnetic recording medium having low relative magnetic permeability, which is used for forming a magnetic recording film to be applied to a high-density magnetic recording medium of a hard disk, and particularly for forming a magnetic recording film to be applied to the perpendicular magnetic recording medium. <P>SOLUTION: The sputtering target has a component composition comprising 0.5 to 15 mol% non-magnetic oxide, 4 to 20 mol% Cr, 5 to 25 mol% Pt, and the balance Co with unavoidable impurities; and has such a structure that a Co-Cr-Pt ternary alloy phase and a mixed phase of a Pt phase and a non-magnetic oxide phase coexist, and the Co-Cr-Pt ternary alloy phase is surrounded by the mixed phase of the Pt phase and the non-magnetic oxide phase. <P>COPYRIGHT: (C)2009,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 ultrahigh density recording has been attracting 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 this perpendicular magnetic recording type hard disk medium, and this CoCrPt—SiO ₂ granular magnetic recording film is made of Co—Cr—Pt 3. It is known to produce by performing magnetron sputtering using a sputtering target having a mixed phase of an original 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, commercially available Co-Cr-Pt ternary Alloy powder or Co—Cr—Pt ternary alloy powder prepared by rapid solidification and silicon dioxide powder: silicon dioxide: 0.5 to 15 mol%, Cr: 4 to 20 mol%, Pt: 5 to 25 mol It is known that it is prepared by blending and mixing so as to have a composition consisting of Co, the balance: Co, and then vacuum hot pressing or hot isostatic pressing (Patent Document 1, Patent Document). See, eg, 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).
“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 uses a Co—Cr—Pt ternary alloy phase, which is a ferromagnetic alloy, as a base, and nonmagnetic oxides such as SiO ₂ are uniformly dispersed in the base. It has a structure, and the proportion of magnetic flux passing through the inside of the target is larger than that of a normal 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 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, in a sputtering target having a component composition comprising nonmagnetic oxide: 0.5 to 15 mol%, Cr: 4 to 20 mol%, Pt: 5 to 25 mol%, and the balance: Co and inevitable impurities The structure can be composed of a Co—Cr—Pt ternary alloy phase and a mixed phase composed of a Pt phase and a nonmagnetic oxide phase to reduce the relative magnetic permeability of the target, and the Co—Cr— Research results have been obtained that the relative permeability of the target can be further reduced by making the Pt ternary alloy phase a structure surrounded by a mixed phase composed of the Pt phase and the nonmagnetic oxide phase. It is.

This invention was made based on these research results,
(1) Nonmagnetic oxide: 0.5 to 15 mol%, Cr: 4 to 20 mol%, Pt: 5 to 25 mol%, a sputtering target having a component composition composed of Co and inevitable impurities The structure of the sputtering target is a perpendicular magnetic recording medium film having a low relative permeability having a structure composed of a Co—Cr—Pt ternary alloy phase and a mixed phase composed of a Pt phase and a nonmagnetic oxide phase. Forming sputtering target,
(2) The Co—Cr—Pt ternary alloy phase is surrounded by a mixed phase composed of a Pt phase and a nonmagnetic oxide phase, and the perpendicular magnetic recording medium film formation having a low relative permeability as described in (1) above is performed. The sputtering target has a feature.

In addition to silicon dioxide, the nonmagnetic oxide contained in the sputtering target for forming a perpendicular magnetic recording medium film having a low relative permeability according to the present invention is tantalum oxide, titanium oxide, aluminum oxide, magnesium oxide, thorium oxide, zirconium oxide. In addition, cerium oxide and yttrium oxide can be used. This is already known. Therefore, the present invention
(3) The nonmagnetic oxide is any one of silicon dioxide, tantalum oxide, titanium oxide, aluminum oxide, magnesium oxide, thorium oxide, zirconium oxide, cerium oxide, and yttrium oxide. 2) A sputtering target for forming a perpendicular magnetic recording medium film having a low relative magnetic permeability described in 2).

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—Pt ternary alloy powder, Pt powder and non-magnetic oxide powder are prepared as raw powders. The raw material powder contains non-magnetic oxide: 0.5 to 15 mol%, Cr: 4 to 20 mol%, Pt: 5 to 25 mol%, and the balance: a component composition consisting of Co and inevitable impurities. The mixed powder obtained is hot-pressed at a temperature (700 to 1050 ° C.) lower than the normal hot press temperature (1100 ° C. or higher). This hot pressing at a lower temperature (700 to 1050 ° C.) prevents Co and Cr contained in the Co—Cr—Pt ternary alloy powder, which is a raw material powder, from diffusing into the Pt phase. This is to prevent Pt from diffusing into the Co—Cr—Pt ternary alloy phase and decreasing or disappearing.

The Co—Cr—Pt ternary alloy powder used in manufacturing the sputtering target for forming a perpendicular magnetic recording medium film having a low relative permeability according to the present invention is Cr: 4.2 to 33.3 mol%, Pt: 0. It is preferable that it has a composition of 0.01 to 1 mol% and the balance is Co, and is therefore dispersed in the base material 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—Pt ternary alloy phase also contains Cr: 4.2 to 33.3 mol%, Pt: 0.01 to 1 mol%, and the balance is Co.

  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, average particle size: 20 μm Co—Cr—Pt 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 Co powder , average particle size: providing a Cr powder of 5 [mu] m, further both the average particle size as the non-magnetic oxide powder: was prepared 3 [mu] m SiO ₂ powder, TiO ₂ powder, a _Ta 2 _{O 5} powder and _Al 2 _{O 3} powder .

Example 1
Co—Cr—Pt ternary alloy powder A, Pt powder and SiO ₂ powder shown in Table 1 contain Cr: 10.8%, Pt: 15.3%, SiO ₂ : 10.0%, The balance is blended so as to have 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 is replaced with an Ar gas atmosphere. 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 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-Pt ternary alloy phase As a result, a mixed phase of Pt phase and SiO ₂ phase was observed around the Co—Cr—Pt 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
The previously prepared Co powder, Cr powder, Pt powder and SiO ₂ powder contain Cr: 10.8%, Pt: 15.3%, SiO ₂ : 10.0%, and the remainder from Co and inevitable 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 is replaced with an Ar gas atmosphere, and then the container is sealed. did. 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 1 having a diameter of 152.4 mm and a thickness of 5 mm was produced. Further, when this conventional target 1 was cut and the cut surface was observed by an electron beam microprobe analyzer (EPMA) surface analysis method, a structure in which SiO ₂ particles were uniformly dispersed in the Co—Cr—Pt alloy phase. It was observed. 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—Pt ternary alloy powder B, Pt powder and TiO ₂ powder shown in Table 1 contain Cr: 9.9%, Pt: 13.5%, TiO ₂ : 9.0%, The balance is blended so as to have 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 is replaced with an Ar gas atmosphere. 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 2 of the present invention having a diameter of 152.4 mm and a thickness of 5 mm was produced. Further, the target 2 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 TiO ₂ phase, and a Co—Cr—Pt ternary alloy phase were found. As a result, a mixed phase composed of a Pt phase and a TiO ₂ phase was observed around the Co—Cr—Pt 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
The previously prepared Co powder, Cr powder, Pt powder and TiO ₂ powder contain Cr: 9.9%, Pt: 13.5%, TiO ₂ : 9.0%, and the balance from Co and inevitable 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 is replaced with an Ar gas atmosphere, and then the container is sealed. did. 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, a structure in which the TiO ₂ particle phase was dispersed in the Co—Cr—Pt alloy phase. It was observed. 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—Pt ternary alloy powder C, Pt powder, and Ta ₂ O ₅ powder shown in Table 1 are Cr: 16.0%, Pt: 15.4%, Ta ₂ O ₅ : 5.0% In which the balance is 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 is filled with Ar gas. The atmosphere was replaced, 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 cutting the invention target 3, was observed with the cut surface in the surface analysis of the electron beam microprobe analyzer (EPMA), Pt phase, _Ta 2 _{O 5} phase and Co-Cr-Pt ternary alloy A phase was observed, and a mixed phase composed of a Pt phase and a Ta ₂ O ₅ phase was observed around the Co—Cr—Pt ternary alloy phase. The maximum relative permeability in the in-plane direction of the target 3 of the present invention was measured, and the results are shown in Table 2.

Conventional example 3
Co powder prepared in advance, Cr powder, Pt powder and _Ta 2 _{O 5} powder, Cr: 16.0%, Pt: 15.4%, Ta 2 O 5: it contains 5.0%, the balance being Co 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 replaced with an Ar 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 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, Ta ₂ O ₅ particle phase was dispersed in the Co—Cr—Pt alloy phase. Some organizations were 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—Pt ternary alloy powder D, Pt powder and Al ₂ O ₃ powder shown in Table 1 are Cr: 10.7%, Pt: 14.7%, Al ₂ O ₃ : 6.0% In which the balance is 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 is filled with Ar gas. The atmosphere was replaced, 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, 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-Pt ternary alloy A phase was observed, and a mixed phase composed of a Pt phase and an Al ₂ O ₃ phase was observed around the Co—Cr—Pt 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 prepared in advance, Cr powder, Pt powder and _Al 2 _{O 3} powder, Cr: 10.7%, Pt: 14.7%, Al 2 O 3: contains 6.0%, the balance being Co 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 replaced with an Ar 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 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. Furthermore, when this conventional target 4 was cut and the cut surface was observed by an electron beam microprobe analyzer (EPMA) surface analysis method, the Al ₂ O ₃ particle phase was uniformly dispersed in the Co—Cr—Pt alloy phase. The organization that has been 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 target 1 of the present invention and the conventional target 1 are compared, the composition of the components is the same, but the Co—Cr—Pt ternary alloy phase is uniformly dispersed in the substrate, and the Pt phase surrounds it. and non-magnetic oxide phase present invention targets are surrounded by a mixed phase consisting of SiO ₂ phase 1 is the, SiO ₂ phase is a non-magnetic oxide phase in the Co-Cr-Pt ternary alloy phase Since the maximum relative permeability in the in-plane direction of the target is smaller than that of the conventional target 1 that is dispersed, the leakage magnetic flux density is large during sputtering. Therefore, the target 1 of the present invention can be sputtered more efficiently than the conventional target 1. I understand. 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 (3)

Non-magnetic oxide: 0.5 to 15 mol%, Cr: 4 to 20 mol%, Pt: 5 to 25 mol%, a sputtering target having a component composition consisting of Co: unavoidable impurities: The structure of this sputtering target is composed of a Co—Cr—Pt ternary alloy phase and a mixed phase composed of a Pt phase and a nonmagnetic oxide phase. Sputtering target. 2. The perpendicular magnetic recording medium film with low relative permeability according to claim 1, wherein the Co—Cr—Pt ternary alloy phase is surrounded by a mixed phase comprising a Pt phase and a nonmagnetic oxide phase. Sputtering target for formation. The nonmagnetic oxide is any one of silicon dioxide, tantalum oxide, titanium oxide, aluminum oxide, magnesium oxide, thorium oxide, zirconium oxide, cerium oxide, and yttrium oxide. 2. A sputtering target for forming a perpendicular magnetic recording medium film having a low relative magnetic permeability according to 2.