JP2010182416A - Method for manufacturing perpendicular magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a perpendicular magnetic recording medium having a soft magnetic layer and a magnetic recording layer of a granular structure on a base body capable of easily increasing a coercive force Hc of the magnetic recording layer. <P>SOLUTION: The method for manufacturing the perpendicular magnetic recording medium includes a soft magnetic layer formation process S.3 for forming the soft magnetic layer on the base body, a magnetic recording layer formation process S.6 for forming the magnetic recording layer having the granular structure by a Co magnetic material as an upper layer of the soft magnetic layer, and a heating process S.7 for heating the medium obtained by forming the magnetic recording layer in the magnetic recording layer formation process S.6 to increase the coercive force value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a perpendicular magnetic recording medium mounted on a perpendicular magnetic recording type HDD (hard disk drive) or the like.

  Various information recording techniques have been developed with the recent increase in information processing capacity. In particular, the surface recording density of HDDs using magnetic recording technology continues to increase at an annual rate of about 100%. Recently, an information recording capacity exceeding 100 GB has been required for a 2.5-inch diameter magnetic disk used for HDDs and the like. In order to meet such a demand, per 1 inch. It is required to realize an information recording density exceeding 200 Gbit. In order to achieve a high recording density in a magnetic disk used for an HDD or the like, it is necessary to refine the magnetic crystal particles constituting the magnetic recording layer for recording information signals and to reduce the layer thickness. It was. However, in the case of a magnetic disk of the in-plane magnetic recording method (also called longitudinal magnetic recording method or horizontal magnetic recording method) that has been commercialized conventionally, as a result of the progress of miniaturization of magnetic crystal grains, superparamagnetic phenomenon The thermal stability of the recording signal is impaired, and the so-called thermal fluctuation phenomenon that the recording signal disappears has occurred, which has been an impediment to increasing the recording density of the magnetic disk.

  In order to solve this obstacle, a perpendicular magnetic recording type magnetic disk has recently been proposed. In the case of the perpendicular magnetic recording system, unlike the case of the in-plane magnetic recording system, the easy axis of magnetization of the magnetic recording layer is adjusted to be oriented in the direction perpendicular to the substrate surface. The perpendicular magnetic recording method can suppress the thermal fluctuation phenomenon as compared with the in-plane recording method, and is suitable for increasing the recording density. For example, in JP-A-2005-285275 (Patent Document 1), an adhesion layer, a soft magnetic layer, a seed layer, an underlayer, a perpendicular magnetic recording layer, a medium protective layer, and a lubricating layer are formed in this order on a substrate. A technique relating to the perpendicular magnetic recording medium is disclosed. In addition, US Pat. No. 6,468,670 (Patent Document 2) discloses a perpendicular magnetic recording medium having a structure in which an artificial lattice film continuous layer (exchange coupling layer) exchange-coupled to a particulate recording layer is attached. ing.

JP 2005-285275 A US Pat. No. 6,468,670

  Incidentally, the improvement in the recording density of the magnetic disk is achieved mainly by reducing the medium noise and narrowing the track due to the high coercive force of the magnetic recording layer. To increase the coercive force Hc, the magnetic recording layer is strengthened. It is effective to improve the crystallinity and crystal orientation of the magnetic particles, reduce the crystal grain size, and reduce the magnetic interaction between the crystal particles.

Therefore, for example, in a CoCrPt—SiO ₂ type perpendicular magnetic recording medium, by using a high Ar pressure sputtering process, the magnetic particles are refined, and at the same time, SiO ₂ is segregated at the grain boundaries, and between the crystal grains of the magnetic recording layer. A method of reducing the magnetic interaction is considered.

  Certainly, the coercivity of the magnetic recording layer can be increased to some extent by the high Ar pressure sputtering process. However, in order to fully meet the further demands for increasing the recording density of recent magnetic disks, it is required to realize a higher coercive force than before.

  The present invention solves such problems, and it is possible to easily increase the coercive force Hc of a magnetic recording layer in a perpendicular magnetic recording medium having a soft magnetic layer and a magnetic recording layer having a granular structure on a substrate. An object of the present invention is to provide a method for manufacturing a perpendicular magnetic recording medium.

  In order to solve the above problems, a method of manufacturing a perpendicular magnetic recording medium according to the present invention includes a soft magnetic layer forming step of forming a soft magnetic layer on a substrate, and CoCrPt and an oxide as an upper layer of the soft magnetic layer. A magnetic recording layer forming step for forming a magnetic recording layer, which is a ferromagnetic layer having a granular structure, and a medium obtained by forming the magnetic recording layer are heated at 150 ° C. in a constant temperature bath in order to improve the coercive force. A heating step of heating to a temperature higher than 240 ° C. and a continuous layer forming step of forming a continuous layer having perpendicular magnetic anisotropy as an upper layer of the magnetic recording layer after the heating step. .

  The heating step may be performed in vacuum or in air as long as the surface of the medium is not contaminated. The heating temperature may be higher than 150 ° C. and lower than 240 ° C., but it is desirably 150 ° C. to 230 ° C., particularly about 200 ° C., so that the value of Hc can be greatly improved.

  The substrate is preferably made of glass having excellent heat resistance. As the glass for the substrate, amorphous glass or crystallized glass can be used, and examples thereof include aluminosilicate glass, aluminoborosilicate glass, soda lime glass, and the like. Among these, aluminosilicate glass is preferable. Further, when the soft magnetic layer is made amorphous, it is preferable that the substrate is made of amorphous glass. Use of chemically strengthened glass is preferable because of its high rigidity.

  The surface roughness of the main surface of the substrate is preferably 6 nm or less as Rmax defined by JIS and 0.6 nm or less as Ra. By using such a smooth surface, the gap between the perpendicular magnetic recording layer and the soft magnetic layer can be made constant, so that a suitable magnetic circuit can be formed between the magnetic head, the perpendicular magnetic recording layer, and the soft magnetic layer. it can.

  Each layer on the substrate is preferably formed by sputtering. In particular, when a film is formed by a DC magnetron sputtering method, uniform film formation is possible, but it is also preferable to use an in-line type film formation method from the viewpoint of mass productivity.

  The soft magnetic layer is not particularly limited as long as it is formed of a magnetic material exhibiting soft magnetic properties. For example, an Fe-based soft layer such as an FcTaC-based alloy, FeTaN-based alloy, FeNi-based alloy, FeCoB-based alloy, or FeCo-based alloy is used. Magnetic materials, Co-based soft magnetic materials such as CoTaZr-based alloys and CoNbZr-based alloys, FeCo-based alloy soft magnetic materials, and the like can be used.

  The soft magnetic layer preferably has a magnetic property of 0.01 to 80 Oersted (Oe), preferably 0.01 to 50 Oersted, in coercive force (Hc). The saturation magnetic flux density (Bs) preferably has a magnetic characteristic of 500 emu / cc to 1920 emu / cc. The thickness of the soft magnetic layer is 5 nm to 1000 nm, preferably 20 nm to 150 nm. If it is less than 5 nm, it may be difficult to form a suitable magnetic circuit between the magnetic head, the perpendicular magnetic recording layer, and the soft magnetic layer, and if it exceeds 1000 nm, the surface roughness may increase. Moreover, when it exceeds 1000 nm, sputtering film formation may become difficult.

The magnetic recording layer is preferably formed of CoCrPt containing an oxide. An oxide is a substance that can form a grain boundary around magnetic grains so that exchange interaction between magnetic grains (magnetic grains) is suppressed or blocked, and is solid with cobalt (Co). Any substance that does not dissolve can be used. Examples thereof include silicon oxide (SiO ₂ ), chromium oxide (CrO ₂ ), titanium oxide (TiO ₂ ), zircon oxide (ZrO ₂ ), and tantalum oxide (Ta ₂ O ₅ ). The content of SiO ₂ is preferably 3 mol% to 20 mol%, and desirably 5 mol% to 12 mol%. The film thickness of the magnetic recording layer is preferably 3 nm or more, and desirably 7 nm to 15 nm.

  The continuous layer includes an exchange energy control layer formed by alternately laminating CoB and Pd or Pt, and a coupling control layer made of Pd or Pt and coupling the exchange energy control layer to the magnetic recording layer. It is preferable to form them. However, the exchange energy control layer is intended to improve the reverse domain nucleation magnetic field (Hn), and the exchange energy control layer may not be a multilayer film as long as Hn can be improved.

  When the exchange energy control layer is formed above the magnetic recording layer, the magnetic recording layer, the coupling control layer, and the exchange energy control layer are stacked in this order from the bottom, and the exchange energy control layer is formed below the magnetic recording layer. In this case, the exchange energy control layer, the coupling control layer, and the magnetic recording layer may be laminated in this order from below.

  According to the present invention, the coercive force Hc can be easily increased and a high S / N characteristic can be obtained for a perpendicular magnetic recording medium without significantly changing an existing manufacturing process (without impairing mass productivity). Is possible.

It is a figure explaining the structure of the perpendicular magnetic recording disk based on an Example. It is a figure explaining the manufacturing method of the perpendicular magnetic recording disk of FIG. It is a figure which shows the relationship between heating temperature and coercive force.

  Embodiments of the perpendicular magnetic recording medium according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining the configuration of a perpendicular magnetic recording disk (perpendicular magnetic recording medium) according to this embodiment, FIG. 2 is a diagram for explaining a method of manufacturing the perpendicular magnetic recording disk, and FIG. It is a figure which shows the relationship. The numerical values shown in the following examples are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified.

  The perpendicular magnetic recording disk shown in FIG. 1 includes a disk substrate (substrate) 1, an adhesion layer 2, a soft magnetic layer 3, an orientation control layer 4, an underlayer 5, a granular layer (magnetic recording layer) 6, a continuous layer 7, and medium protection. A layer 8 and a lubricating layer 9 are provided. The continuous layer 7 includes a coupling control layer 10 and an exchange energy control layer 11.

  In producing this perpendicular magnetic recording disk, first, an amorphous aluminosilicate glass was formed into a disk shape by direct pressing to produce a glass disk having a diameter of 65 mm (2.5 inches). The glass disk was ground, polished, and chemically strengthened in order to obtain a smooth non-magnetic disk substrate 1 made of a chemically strengthened glass disk (step 1: described as “S.1” in FIG. 2; the same applies hereinafter). When the surface roughness of the main surface of the disk substrate 1 was measured with an AFM (atomic force microscope), it was a smooth surface shape with Rmax of 3.0 nm and Ra of 0.25 nm. Rmax and Ra are in accordance with Japanese Industrial Standard (JIS).

  On the obtained disk substrate 1, a film was formed in order from the adhesion layer 2 to the granular layer 6 by DC magnetron sputtering in an Ar atmosphere using a vacuum-deposited film forming apparatus (Steps 2 to 2). Step 6). Next, after heating the intermediate product (medium) obtained in step 6 with a constant temperature layer (step 7), the continuous layer 7 was formed by the same sputtering method, and the medium protective layer 8 was further formed by the CVD method ( Step 8 to Step 10). Thereafter, the lubricating layer 9 was formed by dip coating (step 11). Hereinafter, the configuration of each layer and a specific manufacturing method will be described.

  The adhesion layer 2 was formed using a Ti alloy target so as to be a 10 nm Ti alloy layer. By forming the adhesion layer 2, the adhesion between the disk substrate 1 and the soft magnetic layer 3 can be improved, so that the soft magnetic layer 3 can be prevented from peeling off. As a material of the adhesion layer 2, for example, a Ti-containing material can be used. From the practical viewpoint, the thickness of the adhesion layer is preferably 1 nm to 50 nm.

  The soft magnetic layer 3 was formed using a CoTaZr target so as to be an amorphous CoTaZr layer of 50 nm.

  The orientation control layer 4 was formed using a Ta target so that an amorphous Ta layer was formed to a thickness of 3 nm. As the underlayer 5, a Ru layer having a thickness of 20 nm was formed. The underlayer 5 may be two layers made of Ru. When forming Ru on the upper layer side, the crystal orientation can be improved by increasing the Ar gas pressure as compared to forming Ru on the lower layer side.

The granular layer 6 formed a 10 nm hcp crystal structure using a hard magnetic target made of CoCrPt containing SiO ₂ as an example of an oxide. An oxide is a substance that can form a grain boundary around magnetic grains so that exchange interaction between magnetic grains (magnetic grains) is suppressed or blocked, and is solid with cobalt (Co). Any substance that does not dissolve can be used. Examples thereof include silicon oxide (SiO ₂ ), chromium oxide (CrO ₂ ), titanium oxide (TiO ₂ ), zircon oxide (ZrO ₂ ), and tantalum oxide (Ta ₂ O ₅ ).

  The intermediate product obtained after the formation of the granular layer 6 was heated at a predetermined temperature for a predetermined time in a thermostatic bath. The heating temperature at this time is higher than 100 ° C. and lower than 240 ° C. and lower than that in the case of general annealing treatment, and preferably about 150 ° C. to 230 ° C.

  The coupling control layer 10 was formed of a Pd layer. The coupling control layer 10 can be formed of a Pt layer in addition to the Pd layer. The film thickness of the coupling control layer 10 is preferably 2 nm or less, and more preferably 0.5 to 1.5 nm.

  The exchange energy control layer 11 is made of an alternating laminated film of CoB and Pd, and is formed of a low Ar gas. The film thickness of the exchange energy control layer 11 is preferably 1 to 8 nm, and desirably 3 to 6 nm. The exchange energy control layer 11 may be formed by using Pt instead of Pd and alternately stacking CoB and Pt.

  Subsequently, the medium protective layer 8 was formed by depositing carbon by a CVD method while maintaining a vacuum. The medium protective layer 8 is a protective layer for protecting the perpendicular magnetic recording layer from the impact of the magnetic head. In general, carbon deposited by the CVD method has improved film hardness compared to that deposited by the sputtering method, so that the perpendicular magnetic recording layer can be protected more effectively against the impact from the magnetic head.

  The lubricating layer 9 was formed by dip coating using PFPE (perfluoropolyether). The film thickness of the lubricating layer 9 is about 1 nm.

  In the manufacturing method described above, the continuous layer 7 is formed in Step 8 and Step 9. However, when the perpendicular magnetic recording disk is manufactured, the formation process of these continuous layers 7 is arbitrary, and the present invention is not limited thereto. In order to obtain an effect, it does not necessarily need to be formed.

  FIG. 3 shows the measurement results of the Kerr effect measuring apparatus for the perpendicular magnetic recording disk manufactured as described above. FIG. 3 is a graph showing the relationship between the heating temperature and the coercive force Hc by changing the temperature from 50 ° C. to 250 ° C. using a thermostatic bath. In addition, this measurement is performed for the perpendicular magnetic recording medium A (CGC medium) on which the continuous layer 7 is formed and the perpendicular magnetic recording medium B that does not have the continuous layer.

  As is apparent from FIG. 3, the coercive force Hc is almost the same for both the medium A and the medium B until the heating temperature is 50 ° C. or near 100 ° C. when the heat treatment is not performed. However, when the heating temperature is 150 ° C., the Hc value is improved, and when the heating temperature is 200 ° C., a significant improvement of 20% or more is recognized as compared with the case where the heat treatment is not performed. On the other hand, when the heating temperature reaches 250 ° C., the value of Hc tends to decrease rapidly.

Since these tendencies are the same in the medium A and the medium B, it is considered that the heat treatment acts not on the continuous layer 7 but on the granular layer 6. Accordingly, the heat treatment can be performed during the process of forming each layer of the media, but it is necessary to perform at least after the granular layer 6 is formed. The mechanism by which the coercive force is improved by heat treatment has not been elucidated, but it is presumed that the perpendicular magnetic anisotropy is improved by the relaxation of the film stress of the granular layer 6. Further, the decrease in Hc at a high temperature of 250 ° C. or higher is presumed to be caused by diffusion of SiO _{2 in} the granular layer and conversely deteriorating perpendicular magnetic anisotropy.

  Therefore, it can be said that the value of Hc can be significantly improved by setting the heating temperature in the heating step to a range higher than 100 ° C. and lower than 240 ° C., particularly about 200 ° C. From the viewpoint of balancing the ease of temperature management and ensuring a certain quality, it is also very effective to manufacture a perpendicular magnetic recording medium with the heating temperature set at about 200 ° C.

  In the above example, the heating step was performed immediately after the granular layer 6 was formed. However, the present invention is not limited to the above steps, and if the granular layer 6 is formed, the same effect can be obtained even if heat treatment is performed after the medium protective layer 8, the lubricating layer 9, or other films are formed. it can.

  The present invention can be used as a method of manufacturing a perpendicular magnetic recording medium mounted on a perpendicular magnetic recording type HDD or the like.

1 ... Disc base (base)
2 ... Adhering layer 3 ... Soft magnetic layer 4 ... Orientation control layer 5 ... Underlayer 6 ... Granular layer (magnetic recording layer)
7 ... continuous layer 8 ... medium protective layer 9 ... lubricating layer 10 ... coupling control layer 11 ... exchange energy control layer 1: Disc substrate forming step 3 ... Soft magnetic layer forming step 6 ... Granular layer forming step (magnetic recording layer forming step)
S. 7 Heating step 8 ... Coupling control layer forming step (continuous layer forming step)
S. 9 ... Exchange energy control layer forming step (continuous layer forming step)

Claims (4)

A soft magnetic layer forming step of forming a soft magnetic layer on the substrate;
Forming a magnetic recording layer, which is a ferromagnetic layer having a granular structure containing CoCrPt and an oxide, as an upper layer of the soft magnetic layer;
A heating step of heating a medium obtained by forming the magnetic recording layer at least in the magnetic recording layer forming step to a temperature higher than 150 ° C. and lower than 240 ° C. in a constant temperature bath in order to improve the coercive force value; ,
A continuous layer forming step of forming a continuous layer having perpendicular magnetic anisotropy as an upper layer of the magnetic recording layer;
A method of manufacturing a perpendicular magnetic recording medium, comprising:   2. The method of manufacturing a perpendicular magnetic recording medium according to claim 1, wherein the substrate is made of glass.   2. The method of manufacturing a perpendicular magnetic recording medium according to claim 1, wherein the soft magnetic layer is formed of an Fe-based soft magnetic material or an FeCo-based alloy soft magnetic material.   The continuous layer includes an exchange energy control layer formed by alternately laminating a Co-based alloy and Pd or Pt, and a coupling control layer made of Pd or Pt and coupling the exchange energy control layer to the magnetic recording layer. 3. The method of manufacturing a perpendicular magnetic recording medium according to claim 2, wherein the perpendicular magnetic recording medium is formed by laminating.

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