JP2002133653A - Ru target material for magnetic recording medium and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the coarsening of crystal grain diameter, lowering of breaking resistibility and the increase of the generation of foreign matters and the deterioration with time that have been occurred in an conventional method even though a high purity RU target material can be obtained in the conventional method. SOLUTION: An ideal RU target material is obtained as a magnetic recording medium through decreasing significantly the generation of foreign matters and the deterioration with time at sputtering time that depends on the crystal grain diameter of the target material and in addition, maintaining the strength by making the average crystal grain diameter 100 μm or smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an antiferromagnetic coupling (hereinafter referred to as AF) of a magnetic recording medium for a magnetic disk drive or the like.
C) The present invention relates to a Ru target material for a magnetic recording medium and a magnetic recording medium used for forming a layer.

[0002]

2. Description of the Related Art In recent years, with the miniaturization and high recording density of magnetic disks, research and development of magnetic recording media have been carried out, and various improvements have been made especially on Co-based magnetic layers and underlayers. Recently, the 23rd Annual Meeting of the Japan Society of Applied Magnetism (19
99) p. No. 442, it has been reported that, by inserting a Ru layer between Co-based magnetic layers and laminating it with a Co-based magnetic layer / Ru layer / Co-based magnetic layer, AFC between the Co magnetic layers provides excellent thermal stability of magnetism. ing.

Further, the Ru layer as described above can be formed by sputtering a Ru target material. As for the Ru target material, as a method of manufacturing a Ru target material for a semiconductor, a method of temporarily forming a powder as disclosed in JP-A-8-311641, followed by melting and solidifying with EB or the like, or a method disclosed in JP-A-2000-144395. There is a method of sintering a powder as proposed by hot pressing or hot isostatic pressing (hereinafter referred to as HIP).

[0004]

SUMMARY OF THE INVENTION The present inventors have prepared a target material by the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 8-311641. It was found that the crystal grains became coarse due to the presence of, and the transverse rupture strength was remarkably reduced, so that it was easily broken during sputtering. In addition, a large number of particles were generated during the sputtering, and the time-dependent change of the sputtering depending on the crystal grain size was large. As described above, the method in which the powder is temporarily molded and then melted and solidified by EB or the like is not suitable as a method for manufacturing a Ru target material for a magnetic recording medium because the crystal grain size is large and the transverse rupture strength is low. Was.

Further, the present inventors have disclosed in Japanese Patent Laid-Open No. 2000-14 / 2000.
When a target material was prepared by the method disclosed in No. 4395, the powder used was 3N because of the powder sintering method.
When sintering is performed using the above high-purity powder, as the sintering conditions become high temperature (1300 ° C. or more) and high pressure (100 MPa or more), the crystal grain size becomes coarse. As a result, the generation of foreign matter and the change with time became large, which proved to be unsuitable as a method for manufacturing a Ru target material for a magnetic recording medium. An object of the present invention is to provide a Ru target material having a fine and uniform crystal grain size, a high density and a high transverse rupture force, and suitable for an AFC layer of a magnetic recording medium.

[0006]

The present inventors have studied the Ru target material for forming the AFC layer of the magnetic recording medium. It has been found that it is possible to significantly reduce the generation of foreign substances and changes over time, and it has been found that a target material having a high bending strength can be produced.

That is, according to the present invention, the average crystal grain size is 100
It is a Ru target material for a magnetic recording medium having a size of μm or less.

Further, the target material of the present invention has a carbon content of 5%.
It is preferable that the purity is 3 to 200 ppm. And the relative density is 9
Preferably, it is 7% or more and the bending strength is 350 MPa or more.

Further, a magnetic recording medium having one or more Ru layers formed using the Ru target material of the present invention can be provided.

[0010]

Embodiments of the present invention will be described below. The most important feature of the present invention is that the average crystal grain size of the Ru target material is 100 μm or less.

The sputter rate during sputtering and the direction in which sputtered particles fly out depend on the crystal orientation. Therefore, if the crystal grain size is large, the irregularities on the sputter surface of the target material become large, and the irregularities become large. Nodules, which are the cause of generation of foreign matter, are likely to be formed. Further, in terms of film characteristics, a temporal change depending on the crystal grain size is reflected on the magnetic characteristics, and the magnetic characteristics become non-uniform. Further, when the crystal grain size becomes coarse, the transverse rupture strength decreases. Accordingly, in a target for a magnetic recording medium in which an indirect cooling type target material is mainly used without using a backing plate, breakage of the target material during sputtering becomes a problem.

In the present invention, the generation of foreign matter and the change with time during sputtering depending on the crystal grain size of the target material are significantly reduced by setting the average crystal grain size of the Ru target material to 100 μm or less against these phenomena. In addition, strength is maintained. Also, the variation of the crystal grain size in the target material is
From the viewpoint of stability of the film characteristics, it is preferable that the number is small, and it is preferable that the maximum crystal grain size does not exceed three times the average crystal grain size.

The Ru target material of the present invention preferably has a carbon content of 5 to 200 ppm. As the purity of the Ru target material is increased, for example, when sintering by the HIP method or the like, the crystal grains become coarser, and the above-described problem occurs. Therefore, by containing a certain amount of carbon, it is possible to suppress the growth of crystal grains when sintering the powder.

The lower limit of the amount of carbon to be contained is set to 5 ppm or more because the effect of suppressing the crystal grain growth of the target material is hardly obtained at 5 ppm or less. Further, the upper limit is set to 200 ppm or less because carbon is 200 ppm or less.
R formed by Ru target material containing more than ppm
This is because the magnetic recording medium using the AFC layer of the u film has a problem that the thermal stability is significantly reduced.

The Ru target material of the present invention preferably has a purity of 3N or more. A film formed by using the Ru target material of the present invention is formed on a magnetic recording medium such as AF
When used for the C layer, if the purity is low, the magnetic properties are degraded. In particular, if the purity is less than 3N, the properties are significantly degraded. Therefore, the purity of the target material is preferably 3N or more.

The total content of gaseous components such as hydrogen, oxygen and nitrogen is preferably 2000 ppm or less, more preferably 1000 ppm or less, and further preferably 100 ppm or less. In addition, Fe, Co, Ni
It is preferable that the ferromagnetic element and the rare earth element are particularly small. Fe, Co and Ni are 200 ppm in total.
The following is preferable, More preferably, it is 100 ppm or less, More preferably, it is 10 ppm or less. Further, the total amount of rare earth elements is preferably 10 ppm or less, more preferably 5 ppm or less, and further preferably 1 ppm or less.

The Ru target material of the present invention preferably has a relative density of 97% or more, more preferably has a relative density of 99% or more, and still more preferably has a relative density of 100%. When the relative density is less than 97%, for example, there is a great possibility that cutting oil at the time of machining performed at the time of manufacturing the target material and a cleaning liquid at the time of cleaning remain in the target material. Since these are vaporized during sputtering and contaminate the sputtering atmosphere, the magnetic properties are remarkably deteriorated. Therefore, the relative density is set to 97% or more.

The Ru target material of the present invention preferably has a transverse rupture force of 350 MPa or more. At present, when a magnetic recording medium is formed by sputtering, the sputtering power tends to be increased in order to improve the productivity, and the clamping method of indirect cooling is also predominant in fixing the target material. For this reason, the thermal stress of the target material increases. When a Ru target material having a transverse rupture force of less than 350 MPa is used, breakage of the target material occurs due to the above phenomenon. Therefore, in the present invention, R
The bending strength of the u target material was set to 350 MPa or more.

The Ru target material for a magnetic recording medium of the present invention can be manufactured by, for example, a powder sintering method using HIP or hot pressing. In order to manufacture a Ru target material by a powder sintering method, a sintering temperature of 1500 ° C. or more is required in the hot press method, and a sintering temperature of 1300 ° C. or more in the HIP method. In such a temperature range, pure Ru having a purity of 3N or more usually has remarkable coarsening of crystal grains, and further, depending on pressure distribution and temperature distribution, coarsening of crystal grains locally occurs.

Although the crystal grain size of the target material produced by powder sintering largely depends on the raw material powder and the sintering conditions, as in the present invention, by adding a certain amount of carbon to the raw material powder, Grain growth during sintering is suppressed. Further, it is preferable to reduce oxygen, nitrogen and the like in consideration of the magnetic characteristics of the magnetic recording medium. The powder used for producing the target material can be produced by subjecting Ru powder produced by chemically reducing to a ball mill using a resin pot and balls. This makes it possible to add carbon simultaneously with miniaturization of the Ru powder itself. Further, by controlling the pulverization time, it becomes possible to control the powder particle size and the carbon content.

[0021]

EXAMPLE Ru powder having the impurities and particle diameters shown in Table 1 was pulverized for 1 hour, 10 hours and 20 hours in an Ar atmosphere using a resin ball mill to produce Ru powder. Table 1 shows impurities and particle diameters of the produced Ru powder by chemical analysis. The powder shown in Table 1 was sintered under the conditions shown in Table 2 to produce a target material. Table 3 shows the average crystal grain size, density, and transverse rupture strength of the produced target material. However, the average crystal grain size was measured by a cutting method, the density was measured by an Archimedes method, and the transverse rupture strength was measured by a three-point bending test.

From Table 3, it can be seen that the average particle diameter of the Ru target material sintered using the powder to which C is added and the particle diameter is adjusted can be controlled to 100 μm or less. Also,
It was confirmed that the gas component and the impurity amount of the target material were 2000 ppm or less in total for the gas component elements and 200 ppm or less for the ferromagnetic elements such as Fe, Co, and Ni. Table 4 shows the results of the GD-MS analysis of Sample 1 as an example of the analysis values of the target material.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

[Table 4]

Using an Al substrate plated with NiP, a substrate temperature of 150 ° C., an Ar pressure of 0.66 Pa, a DC
Cr underlayer, Co-20Cr-1 under the condition of power 500W
0Pt-5B (at%) magnetic layer, RuAFC layer, Co-
Film formation was performed in the order of the 20Cr-10Pt-5B (at%) magnetic layer. The Ru layer was formed using a Ru target material shown in Table 3.

Table 5 shows the measurement results of the coercive force Hc of the formed film-forming substrate measured by a VSM (vibrating sample magnetometer).
Table 4 shows the relative values when the coercive force when the Ru target material of Sample 1 is used is set to 100. In addition, Ru shown in Table 3
Table 5 also shows the measurement results of the particle generation ratio when the film was formed using the target material. However,
The particle generation ratio is a value when the number of particles of the Ru target of Sample 1 is 100.

From Table 5, it can be seen that the magnetic properties are not significantly affected up to a C content of 200 ppm, and that the average crystal grain size of the target material exceeding 100 μm affects the generation of particles. I understand.

[0030]

[Table 5]

[0031]

According to the present invention, it is possible to provide a Ru target material for a magnetic recording medium with reduced foreign matter and aging during sputtering, and this is an extremely effective technique for manufacturing a magnetic recording medium.

Continued on the front page (72) Inventor Shigeru Taniguchi 2107-2 Yasugi-cho, Yasugi City, Shimane Prefecture Inside Hitachi Metals Yasugi Plant (72) Inventor Ei Eno 2107-2 Yasugi-cho Yasugi City, Shimane Prefecture Hitachi Metals Yasugi Plant F term (reference) 4K029 BA02 BC00 BD11 DC03 DC09 5D006 BB01 EA03 5D112 AA05 BB01 FA04 FB02

Claims (6)

[Claims] 1. A Ru target material for a magnetic recording medium having an average crystal grain size of 100 μm or less. 2. The Ru target material for a magnetic recording medium according to claim 1, wherein the carbon content is 5 to 200 ppm. 3. The Ru target material for a magnetic recording medium according to claim 1, wherein the purity is 3 N or more. 4. The Ru target material for a magnetic recording medium according to claim 1, wherein the relative density is 97% or more. 5. The Ru target material for a magnetic recording medium according to claim 1, wherein the bending strength of the target material is 350 MPa or more. 6. A magnetic recording medium comprising at least one Ru film formed using the target material according to claim 1.