JP2006338838A - Method for manufacturing vertical magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain excellent orientation of magnetic crystal grains on a magnetic recording layer and to obtain a desirable magnetic characteristic and electromagnetic conversion characteristic in a vertical magnetic recording medium. <P>SOLUTION: In the method for manufacturing a vertical magnetic recording medium provided with a non-magnetic substrate, a soft magnetic backing layer and a magnetic recording layer, the soft magnetic backing layer is composed of Co-based amorphous alloy containing at least one element out of Zr, Nb and Ta, and the soft magnetic backing layer is formed by deposition power of ≥0.5 kW and ≤3.0 kW by using a spattering method without requiring a process for heating the non-magnetic substrate prior to the formation of the soft magnetic backing layer. The surface roughness of the soft magnetic backing layer is preferably 0.35 nm and less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a perpendicular magnetic recording medium mounted on a fixed magnetic recording device (HDD).

As a technique for realizing high density magnetic recording, a perpendicular magnetic recording system is drawing attention in place of the conventional longitudinal magnetic recording system.
In particular, a double-layer perpendicular magnetic recording medium with a soft magnetic film called a soft magnetic backing layer that easily passes the magnetic flux generated from the magnetic head under the magnetic recording layer that plays a role in recording information is generated in the magnetic head. It is known that it is suitable as a perpendicular magnetic recording medium capable of high-density recording because it increases the magnetic field strength and the magnetic field gradient, improves the recording resolution, and increases the magnetic flux leakage from the magnetic recording layer.
However, the soft magnetic underlayer necessary for realizing the desired recording resolution needs to be a thick film in order to concentrate the magnetic flux efficiently, and the optimum value varies depending on the magnetic head used for recording. Therefore, it is necessary to form a thick film of approximately 100 nm or more. When the film thickness is increased, the soft magnetic underlayer tends to have a high surface roughness (Ra), and the orientational dispersion of the magnetic crystal grains of the magnetic recording layer formed thereon deteriorates. As a result, this leads to a problem that causes deterioration of magnetic characteristics and electromagnetic conversion characteristics.

In order to cope with this problem, a method has been proposed in which the increase in surface roughness is suppressed by forming the soft magnetic underlayer in a number of times (see, for example, Patent Document 1). However, in this method, since a plurality of film forming chambers for forming the soft magnetic backing layer are prepared, a large-scale apparatus is required, resulting in an increase in apparatus cost.
In order to realize the performance of magnetic recording media that will be required in the future, it is necessary to further improve the performance of the magnetic recording layer, without causing deterioration of the magnetic recording layer, and efficiently generating the magnetic flux of the magnetic recording head. A method for efficiently forming a supplemental thick soft magnetic layer is desired.
JP 2004-146015 A

  The present invention has been made in view of the above-mentioned problems, and the object of the present invention is that the soft magnetic backing layer has a small surface roughness and is excellent in the orientation of the magnetic crystal grains of the magnetic recording layer formed thereon. Another object of the present invention is to provide a method for manufacturing a perpendicular magnetic recording medium having good magnetic characteristics and electromagnetic conversion characteristics.

In order to achieve such an object, the present invention provides a method for producing a perpendicular magnetic recording medium comprising a nonmagnetic substrate, a soft magnetic backing layer, and a magnetic recording layer, wherein the soft magnetic backing layer is formed of Zr, Nb, Ta. A Co-based amorphous alloy containing at least one element of the above, and without providing a step of heating the nonmagnetic substrate prior to the formation of the soft magnetic backing layer, the soft magnetic backing layer is 0.5 kW or more The film is formed by a sputtering method with a film forming power of 3.0 kW or less.
The surface roughness of the soft magnetic backing layer is preferably 0.35 nm or less.

  By forming the perpendicular magnetic recording medium as described above, it is possible to reduce the surface roughness of the soft magnetic underlayer, and a perpendicular magnetic recording medium having excellent magnetic characteristics and electromagnetic conversion characteristics can be obtained. In addition, it is possible to increase the film forming power when forming the soft magnetic underlayer, to enable efficient mass production through shortening the film forming time, and to reduce the manufacturing cost.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing a configuration example of a perpendicular magnetic recording medium to which the present invention is applied. The perpendicular magnetic recording medium includes a first seed layer 2, an orientation control layer 3, an antiferromagnetic layer 4, a soft magnetic backing layer 5, a second seed layer 6, a nonmagnetic underlayer 7, a magnetic layer on a nonmagnetic substrate 1. A recording layer 8 and a protective layer 9 are formed in this order, and a liquid lubricant layer 10 is further formed thereon.
As the non-magnetic substrate 1, there can be used an Al alloy plated with NiP, chemically strengthened glass, crystallized glass or the like used for a normal magnetic recording medium. When the substrate heating temperature is suppressed to 100 ° C. or less, a plastic substrate made of a resin such as polycarbonate or polyolefin can be used.
As the soft magnetic underlayer 5, a Co-based amorphous alloy containing at least one element of Zr, Nb, or Ta and Co is used. For example, good electromagnetic conversion characteristics can be obtained by using CoNbZr, CoTaZr, or the like. The optimum value of the thickness of the soft magnetic backing layer 5 varies depending on the characteristics of the magnetic head used for recording, but is preferably 10 nm or more and 300 nm or less in view of productivity.

The soft magnetic backing layer 5 is formed using a sputtering method such as a DC magnetron sputtering method or an RF magnetron sputtering method. The nonmagnetic substrate is not heated prior to sputtering, and sputtering is started at room temperature. The deposition power for sputtering deposition is preferably 0.5 kW or more and 3.0 kW or less per side of the nonmagnetic substrate. It has been confirmed that this does not depend on the outer diameter of the nonmagnetic substrate for substrates having an outer diameter of 0.85 inches to 3.5 inches.
The surface roughness Ra of the soft magnetic backing layer is preferably 0.35 nm or less.
The antiferromagnetic layer 4 is preferably a layer provided to form an antiferromagnetic exchange coupling with the soft magnetic backing layer 5 to suppress the formation of domain walls in the soft magnetic backing layer. As the antiferromagnetic layer 4, a Mn-based alloy such as FeMn, CoMn, IrMn is preferably used. The thickness of the antiferromagnetic layer 4 is not particularly limited, but is preferably about 2 nm to 20 nm in order to obtain appropriate exchange coupling and to be suitable for mass production.

The orientation control layer 3 is a layer preferably provided for improving the orientation of the antiferromagnetic layer. The orientation of the antiferromagnetic layer 4 is improved by forming a layer containing at least Ni and Fe and adding at least one element selected from B, Nb, and Si. The film thickness of the orientation control layer 3 is preferably 5 nm or more so that sufficient crystal growth can be obtained.
The first seed layer 2 is a layer that is preferably provided in order to improve the crystallinity and orientation of the orientation control layer 3. It is particularly preferable to form from Ta. The thickness of the Ta film is preferably 20 nm or less, which is amorphous or amorphous.
The nonmagnetic underlayer 7 is used for suitably controlling the crystal orientation, crystal grain size, and grain boundary segregation of the magnetic recording layer 8. As a material, a single metal film or an alloy film having a face-centered cubic (fcc) structure or a hexagonal close-packed (hcp) structure is preferable, and Ti, Ru, Pd, Pt and an alloy film containing them are preferable. It is not limited. The film thickness of the nonmagnetic underlayer 7 is required from the viewpoint of recording to be the minimum film thickness necessary for controlling the structure of the magnetic recording layer 8.

The second seed layer 6 is a layer preferably provided for improving the crystallinity and orientation of the nonmagnetic underlayer 7. It is particularly preferable to form from Ta.
As the magnetic recording layer 8, a CoCrPt-based alloy film, a granular film having a nonmagnetic oxide or nitride such as SiO2 at the crystal grain boundary, and a multilayer laminated film such as (Co / Pd) _n can be used.
The protective layer 9 may be a conventionally used protective film. For example, a protective film mainly composed of carbon can be used. The conditions such as the film thickness of the protective layer 9 can be the same as those used in ordinary magnetic recording media.
The liquid lubricant layer 10 can also be made of a conventionally used material. For example, a perfluoropolyether lubricant can be used. The conditions such as the film thickness of the liquid lubricant layer 10 can be the same as those used in ordinary magnetic recording media.

Hereinafter, it demonstrates in detail, using an Example etc.
The surface roughness of the soft magnetic underlayer is affected by the substrate temperature and the deposition power. First, the results of studying this effect by forming a soft magnetic underlayer will be described.
(Experimental example 1)
A chemically tempered glass substrate (N-5 glass substrate manufactured by HOYA) having a smooth outer surface is used as the non-magnetic substrate 1, and this is washed and introduced into the sputtering apparatus to heat the non-magnetic substrate 1. Sputter film formation was started without performing the steps. First, a Ta first seed layer 2 is formed with a film thickness of 5 nm using a Ta target, followed by a Ni12Fe3B target (where the number represents the atomic% of the subsequent element, Fe is 12 atomic%, and B is 3 The NiFeB orientation control layer 3 is formed at a film thickness of 5 nm using the atomic percent and the balance is Ni. The same applies hereinafter.), And then the IrMn antiferromagnetic layer 4 is formed using the Ir80Mn target. After forming the film at a thickness of 10 nm, the CoZrNb soft magnetic backing layer 5 was formed using a Co5Zr8Nb target. The film formation power was changed from 0.1 kW to 3.0 kW, and the film formation time was adjusted according to the film formation power so that the film thickness was 150 nm. Subsequently, heating was performed using a lamp heater, and immediately after raising the substrate surface temperature to 250 ° C., the substrate was cooled to 150 ° C. in a fixed magnetic field of 1000 Oe, and then taken out from the vacuum apparatus to the soft magnetic backing layer. Experimental Example 1 was obtained. Each layer was formed by DC magnetron sputtering under an Ar gas pressure of 5 mTorr.
(Experimental example 2)
After cleaning the nonmagnetic substrate 1 and introducing it into the sputtering apparatus, immediately before starting the deposition of the Ta first seed layer 2, heating is performed using a lamp heater, and the surface temperature of the nonmagnetic substrate 1 is increased to 100 ° C. Except for the increase, the film was formed in the same manner as in Experimental Example 1 to obtain Experimental Example 2.

Ra of the soft magnetic underlayer of the samples manufactured in Experimental Examples 1 and 2 was measured with an atomic force microscope (AFM).
FIG. 2 shows a change in Ra of the soft magnetic backing layer when the film forming power of the soft magnetic backing layer is changed.
In both Experimental Examples 1 and 2, Ra shows a tendency to decrease as the film forming power increases when the soft magnetic underlayer is formed, and shows a substantially constant value when the film forming power is 0.5 kW or more. In Experimental Example 2 in which the nonmagnetic substrate was heated, Ra was higher than that in Nonheated Experimental Example 1, and Ra was increased by increasing the temperature of the nonmagnetic substrate.
The soft magnetic backing layer having a low Ra can be obtained by heating the nonmagnetic substrate without increasing the film forming power for forming the soft magnetic backing layer to 0.5 kW or higher. The upper limit of the deposition power was confirmed up to 3.0 kW.

  Hereinafter, it demonstrates in detail using an Example.

A chemically tempered glass substrate (N-5 glass substrate manufactured by HOYA) having a smooth outer surface is used as the non-magnetic substrate 1 and is introduced into the sputtering apparatus after cleaning, and the non-magnetic substrate is heated. Without using Ta target, Ta first seed layer 2 is formed with a film thickness of 5 nm, Ni12Fe3B target is used to form NiFeB orientation control layer 3 with a film thickness of 5 nm, and Ir80Mn target is subsequently used. After forming the IrMn antiferromagnetic layer 4 with a film thickness of 10 nm, the CoZrNb soft magnetic backing layer 5 was formed using a Co5Zr8Nb target. The film formation power was changed from 0.1 kW to 3.0 kW, and the film formation time was adjusted according to the film formation power so that the film thickness was 150 nm. For comparison, the deposition power is varied widely. Subsequently, a Ta second seed layer 6 is formed with a film thickness of 5 nm using a Ta target, a Ru nonmagnetic underlayer 7 is formed with a film thickness of 20 nm using a Ru target, and 10 mol of SiO ₂ is subsequently added. A magnetic recording layer 8 was formed to a thickness of 15 nm by RF magnetron sputtering using Ar-added Co12Cr12Pt target under an Ar gas pressure of 10 mTorr. Subsequently, heating was performed using a lamp heater, and immediately after raising the substrate surface temperature to 250 ° C., cooling was performed to 150 ° C. in a fixed magnetic field of 1000 Oe. Subsequently, the carbon protective layer 9 was formed to a thickness of 5 nm and taken out from the vacuum apparatus. The layers other than the magnetic recording layer 8 were formed by DC magnetron sputtering under an Ar gas pressure of 5 mTorr. Subsequently, a liquid lubricant layer 10 was formed at a film thickness of 1.5 nm by a dip coating method to obtain a two-layer perpendicular magnetic recording medium.
(Comparative Example 1)
After cleaning the nonmagnetic substrate 1 and introducing it into the sputtering apparatus, immediately before starting the deposition of the Ta first seed layer 2, heating is performed using a lamp heater, and the surface temperature of the nonmagnetic substrate 1 is increased to 100 ° C. A comparative example 1 was obtained by forming a film in the same manner as in Example 1 except that the film was raised.

The holding power (Hc) of the samples of Example 1 and Comparative Example 1 was measured using a Kerr effect measuring device. The signal-to-noise ratio (SNR) was measured using a spin stand tester equipped with a single magnetic pole type magnetic head for a perpendicular magnetic recording medium.
FIG. 3 shows the change in the Hc value with respect to the deposition power of the soft magnetic backing layer in Example 1 and Comparative Example 1, and FIG. 4 shows the change in the SNR value with respect to the deposition power of the soft magnetic backing layer of the same sample. Show.
In both Example 1 and Comparative Example 1, both the Hc and SNR tend to increase with increasing film forming power when the soft magnetic underlayer is formed, and show a substantially constant value when the film forming power is 0.5 kW or more. In Comparative Example 1 in which the nonmagnetic substrate was heated, both Hc and SNR showed lower values than in Non-heated Example 1. The result corresponds to the change in the surface roughness Ra of the soft magnetic underlayer confirmed in Experimental Examples 1 and 2.

  A perpendicular magnetic recording medium having a high coercive force and a high signal-to-noise ratio can be obtained by increasing the film forming power to 0.5 kW or more when forming the soft magnetic backing layer without heating the nonmagnetic substrate. Can do.

It is a cross-sectional schematic diagram for demonstrating the structural example of the perpendicular magnetic recording medium to which this invention is applied. It is a figure for demonstrating the change of the value of surface roughness with respect to the film-forming power of a soft-magnetic underlayer. It is a figure for demonstrating the change of the value of coercive force with respect to the film-forming electric power of a soft-magnetic underlayer. It is a figure for demonstrating the change of the value of a signal noise ratio with respect to the film-forming electric power of a soft-magnetic underlayer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nonmagnetic base | substrate 2 1st seed layer 3 Orientation control layer 4 Antiferromagnetic layer 5 Soft magnetic backing layer 6 2nd seed layer 7 Nonmagnetic underlayer 8 Magnetic recording layer 9 Protective layer 10 Liquid lubricant layer

Claims (2)

In a perpendicular magnetic recording medium comprising a nonmagnetic substrate, a soft magnetic backing layer, and a magnetic recording layer,
The soft magnetic underlayer is a Co-based amorphous alloy containing at least one element of Zr, Nb, and Ta,
The soft magnetic backing layer is formed by a sputtering method at a film forming power of 0.5 kW or more and 3.0 kW or less without providing a step of heating the nonmagnetic substrate prior to the formation of the soft magnetic backing layer. A method of manufacturing a perpendicular magnetic recording medium.   2. The method of manufacturing a perpendicular magnetic recording medium according to claim 1, wherein the soft magnetic backing layer has a surface roughness of 0.35 nm or less.

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