JP2007273050A - Method of manufacturing perpendicular magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a perpendicular magnetic recording medium easily increasing nucleation field Hn and coercive force Hc of a magnetic recording layer on the perpendicular magnetic recording medium (CGC medium) comprising a soft magnetic layer, a magnetic recording layer having a granular structure, and a continuous layer having high perpendicular magnetic anisotropy on a substrate, can be easily enhanced. <P>SOLUTION: The perpendicular magnetic recording medium is characterized by being equipped with; a soft magnetic layer formation process S.3 for forming a soft magnetic layer on the substrate; a magnetic recording layer formation process S.6 for forming a magnetic recording layer comprising a granular structure as a top layer of the soft magnetic layer; a continuous layer formation processes S.7 and S.8 which form continuous layers having a perpendicular magnetic anisotropy as a top layer or a base layer of the magnetic recording layer; a protective layer formation process S.10 which forms a protective layer as a top layer of the magnetic recording layer and the continuous layer; and a heating process S.9 which heats the layers at ≤150°C and ≥240°C after magnetic recording layer formation process, after continuous layer formation process, or after protective layer formation process. <P>COPYRIGHT: (C)2008,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

  As described in Patent Document 1, in a perpendicular magnetic recording medium, a soft magnetic layer is provided below the magnetic recording layer, and a closed magnetic path that returns from the recording head to the recording head through the soft magnetic layer is formed. Therefore, a method of applying a high recording magnetic field to the magnetic recording layer is generally adopted. As a result, it is possible to apply a strong magnetic field to the recording track, but at the same time, the leakage magnetic field to the adjacent track also increases. Therefore, the number of tracks is mainly centered on WAIT (Wide Area Track Erasure), that is, the track to be written. The phenomenon that the recorded information disappears over μm becomes a problem. This problem is particularly apparent in formats where adjacent tracks are close (ie, high recording density).

  As a technique for reducing WAIT, it is said that it is important to make the reverse domain nucleation magnetic field Hn of the magnetic recording layer negative and to further increase its absolute value. In order to obtain high (large absolute value) Hn, a CGC (Coupled Granular Continuous) medium in which a thin film (continuous layer) exhibiting high perpendicular magnetic anisotropy is formed above or below a magnetic recording layer having a granular structure is used. What is devised is as described in Patent Document 2.

  However, even if the configuration of the CGC medium is simply adopted for the perpendicular magnetic recording medium, it is difficult to obtain a sufficient reverse domain nucleation magnetic field satisfying Hn <−2000 Oersted (Oe).

The improvement in recording density is mainly achieved by reducing noise and narrowing the track due to the high coercive force of the magnetic recording layer. To increase the coercive force Hc, the crystal of ferromagnetic particles in the magnetic recording layer is used. It is effective to improve the crystallinity and crystal orientation, refine the crystal grain size, and reduce the magnetic interaction between crystal grains. In the CoCrPt—SiO ₂ type perpendicular magnetic recording medium, the magnetic particles are refined using a high Ar pressure sputtering process, and at the same time, SiO ₂ is segregated at the grain boundaries to cause magnetic interaction between crystal grains of the magnetic recording layer. Although it is conceivable to reduce it, it is difficult to obtain a sufficient coercive force even if the CGC medium is formed by a high Ar pressure sputtering process.

  The present invention solves such a problem, and relates to a perpendicular magnetic recording medium (CGC medium) comprising a soft magnetic layer, a magnetic recording layer having a granular structure, and a continuous layer having high perpendicular magnetic anisotropy on a substrate. Another object of the present invention is to provide a method of manufacturing a perpendicular magnetic recording medium that can easily increase the reverse domain nucleation magnetic field Hn and the coercive force Hc of the magnetic recording layer.

  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 a magnetic recording having a granular structure as an upper layer of the soft magnetic layer. A magnetic recording layer forming step of forming a layer of a Co-based magnetic material, a continuous layer forming step of forming a continuous layer having perpendicular magnetic anisotropy as an upper layer or a lower layer of the magnetic recording layer, the magnetic recording layer and the continuous layer A protective layer forming step for forming a protective layer as an upper layer of the layer and after the magnetic recording layer forming step, after the continuous layer forming step, or after the protective layer forming step, heated to 100 ° C. or higher and 240 ° C. or lower. And a heating step.

  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 DC magnetron sputtering method is used, uniform film formation is possible, but from the viewpoint of mass productivity, it is also preferable to use an in-line type film formation method instead of the sputtering method.

  The soft magnetic layer is not particularly limited as long as it is formed of a magnetic material exhibiting soft magnetic characteristics. 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, preferably 0.01 to 50 oersted in terms of 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 a nonmagnetic substance. A non-magnetic substance 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 cobalt (Co) and Any nonmagnetic substance that does not dissolve in solution may be used. Examples thereof include silicon oxide (SiOx), chromium (Cr), 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. Further, since the magnetic effect does not change, the exchange energy control layer can be disposed above or below the magnetic recording layer. 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.

  The protective layer is preferably formed of carbon. In particular, by forming a film by the CVD method, the hardness of the protective layer can be increased as compared with the case of forming a film by the sputtering method.

  The heating step is preferably performed by heating a medium obtained by forming a continuous layer with a thermostatic chamber (heating device). Such heating of the medium may be performed in vacuum or in air as long as the surface of the medium is not contaminated. The heating temperature may be about 100 ° C. to 240 ° C., but the value of Hn can be greatly improved even at about 100 to 150 ° C., and if it is about 150 to 240 ° C., the values of both Hn and Hc can be improved. It becomes possible to greatly improve.

  According to the present invention, it is possible to easily increase the reverse domain nucleation magnetic field Hn and the coercive force Hc of a perpendicular magnetic recording medium (CGC medium) without significantly changing an existing manufacturing process (without impairing mass productivity). It is possible to achieve both good WAIT characteristics and high S / N characteristics.

  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 the present embodiment, FIG. 2 is a diagram for explaining a method of manufacturing the perpendicular magnetic recording disk, and FIG. FIG. 4 is a diagram showing the change in characteristics, FIG. 4 is a diagram showing the relationship between the heating temperature and the reverse domain nucleation magnetic field Hn, and FIG. 5 is a diagram showing the relationship between the heating temperature and the coercive force Hc. 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 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, a medium protective layer 8, A lubricating layer 9 is 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 continuous layer 7 by DC magnetron sputtering in an Ar atmosphere using a vacuum-deposited film forming apparatus (Steps 2 to 2). Step 8). Next, the intermediate product (medium) obtained in Step 8 was heated by a constant temperature layer (Step 9), and the medium protective layer 8 was formed by a CVD method (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 orientation control layers 4 and 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 a nonmagnetic substance. A non-magnetic substance 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 cobalt (Co) Any nonmagnetic substance that does not dissolve in solution may be used. Examples thereof include silicon oxide (SiOx), chromium (Cr), chromium oxide (CrO ₂ ), titanium oxide (TiO ₂ ), zircon oxide (ZrO ₂ ), and tantalum oxide (Ta ₂ O ₅ ).

  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.

  The intermediate product obtained after the formation of the exchange energy control layer 11 was heated at a predetermined temperature in a thermostatic bath. The heating temperature at this time is 100 ° C. or higher and 240 ° C. or lower, which is lower than in the case of general annealing. This heat treatment may be performed after forming the granular layer 6 described above or after forming the medium protective layer 8 described below.

  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.

  FIG. 3 shows the measurement results of the Kerr effect measuring apparatus for the perpendicular magnetic recording disk manufactured by the above process. FIG. 3 exemplifies the magnetic characteristics when the heating process is performed (heating temperatures of 150 ° C. and 200 ° C.) and the magnetic characteristics when the same process is not performed. As is apparent from the figure, by performing the heat treatment, the inclination of the hysteresis loop becomes steep when the heating temperature is 150 ° C., and the value of the reverse domain nucleation magnetic field Hn is mainly improved. Furthermore, when the heating temperature is 200 ° C., the hysteresis loop expands in the horizontal axis (Kerr rotation angle axis) direction, and both values of the reverse domain nucleation magnetic field Hn and the coercive force Hc are improved.

  FIG. 4 is a graph showing the relationship between the heating temperature and the reverse domain nucleation magnetic field Hn when the temperature is changed from 50 ° C. to 250 ° C. using a thermostatic bath. FIG. 4 shows that the value of Hn is greatly improved when the heating temperature is about 100 ° C. to 240 ° C., particularly around 230 ° C. Since the value of Hn tends to decrease sharply when the heating temperature exceeds 230 ° C., the heating temperature is set to 200 ° C. or less from the viewpoint of balancing the ease of temperature management and ensuring certain quality. It is also very effective to manufacture a perpendicular magnetic recording medium.

  FIG. 5 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 thermostat. FIG. 5 shows that the Hc value is greatly improved when the heating temperature is about 150 ° C. to 240 ° C., particularly around 230 ° C. As in the case of Hn, the value of Hc also tends to drop sharply when the heating temperature exceeds 230 ° C. From the viewpoint of balancing the ease of temperature management and ensuring a certain quality, the heating temperature is It is also very effective to manufacture a perpendicular magnetic recording medium at a temperature of 200 ° C. or lower.

  Therefore, Hn can be improved by setting the heating temperature in the heating step to 100 ° C. or higher and 240 ° C. or lower, and both Hn and Hc can be greatly improved by setting the heating temperature to 150 ° C. or higher and 240 ° C. or lower. It can be said.

  In the above example, the heating process was performed immediately after the exchange energy control layer 11 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.

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 change of the magnetic characteristic by the heating in the heating process of FIG. It is a figure which shows the relationship between heating temperature and a reverse domain nucleation magnetic field. It is a figure which shows the relationship between heating temperature and coercive force.

Explanation of symbols

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 (protective layer)
9 ... Lubrication 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: Coupling control layer forming step (continuous layer forming step)
S. 8 ... Exchange energy control layer forming step (continuous layer forming step)
S. 9 ... heating process 10 ... Medium protective layer forming step (Protective layer forming step)

Claims (6)

A soft magnetic layer forming step of forming a soft magnetic layer on the substrate;
A magnetic recording layer forming step of forming a magnetic recording layer having a granular structure as an upper layer of the soft magnetic layer from a Co-based magnetic material;
A continuous layer forming step of forming a continuous layer having perpendicular magnetic anisotropy as an upper layer or a lower layer of the magnetic recording layer;
A protective layer forming step of forming a protective layer as an upper layer of the magnetic recording layer and the continuous layer;
And a heating step of heating to 100 ° C. or higher and 240 ° C. or lower after at least the continuous layer forming step.   2. The perpendicular magnetic recording medium according to claim 1, wherein the heating step is performed after the magnetic recording layer forming step, after the continuous layer forming step, after the protective layer forming step, or after forming the medium. Manufacturing method.   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, a Co-based soft magnetic material, or an FeCo-based alloy soft magnetic material.   2. The method of manufacturing a perpendicular magnetic recording medium according to claim 1, wherein the magnetic recording layer is formed of CoCrPt and a nonmagnetic material. 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. The method of manufacturing a perpendicular magnetic recording medium according to claim 1, wherein:

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