JP2008090906A - Method of manufacturing perpendicular magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a perpendicular magnetic recording medium which has a high S/N capable of making a recording density high by improving the crystal orientation properties of a magnetic layer of a granular structure. <P>SOLUTION: The method of manufacturing the perpendicular magnetic recording medium 10, which includes: a glass substrate 1, an underlayer 5 formed on the glass substrate 1 and including a hexagonal metal; and a magnetic layer 6 formed on the underlayer 5 and having columnar magnetic crystal grains including a hexagonal metal and a grain boundary part including an oxide and partitioning the magnetic crystal grains, is characterized in that the magnetic layer 6 is deposited on the heated underlayer 5. Since perpendicular orientation properties of the underlayer 5 is enhanced by heat treatment of the hexagonal underlayer, a value of Δθ50 (an index showing the degree of crystal orientation) of a surface (0002) of the hexagonal underlayer is made narrow, film stress of a boundary part between the hexagonal underlayer and at least the hexagonal magnetic crystal grains can be relaxed, the magnetic layer 6 and the underlayer 5 can be film-deposited without incurring generation of high internal stress and crystal orientation properties of these layers can be improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a perpendicular magnetic recording medium suitable for mounting in a high recording density perpendicular magnetic recording type HDD or the like.

  In order to achieve a high recording density of a magnetic recording medium, a perpendicular magnetic recording method has been proposed. A perpendicular magnetic recording type magnetic recording medium (perpendicular magnetic recording medium) has a magnetic layer whose magnetization facilitating axis is oriented perpendicularly to a substrate. In this perpendicular magnetic recording medium, in order to further increase the recording density, it is necessary to achieve both low noise and high thermal stability. For this purpose, it is required to make the ferromagnetic crystal grains of the magnetic layer finer and uniform, and to reliably perform magnetic and spatial separation between the ferromagnetic crystal grains.

In recent years, a magnetic layer called a granular structure has attracted attention in order to reliably separate ferromagnetic crystal grains and reduce the interaction between the grains. In the magnetic layer having a granular structure, the grain boundary between the ferromagnetic crystal grains is made of an oxide or a nitride to ensure the magnetic separation performance of the ferromagnetic crystal grains. Patent Document 1 proposes a method of forming a magnetic layer having a granular structure in which magnetic crystal particles are surrounded by an SiO ₂ additive in order to ensure magnetic separation performance. Patent Document 2 proposes a method of forming a magnetic layer having a granular structure in which magnetic crystal grains are surrounded by a TiO ₂ additive.
JP 2002-83411 A JP 2001-43526 A

  Here, in order to further increase the recording density and improve the reliability of the perpendicular magnetic recording medium, for example, to realize a perpendicular magnetic recording medium having a high recording density of 150 GB / in 2 or more, the magnetic layer It is necessary to further increase the S / N ratio by more surely forming a magnetic and spatial separation between the magnetic crystal grains. However, in the conventional granular magnetic layer, the exchange coupling between crystal grains is not sufficiently reduced, which is an obstacle for obtaining a high S / N ratio.

  This is because the internal stress generated in each layer or each layer is large due to the difference in the material and process conditions of each layer including the magnetic layer in the perpendicular magnetic recording medium, which adversely affects the film formation process. Conceivable. For example, it is considered that the crystal orientation is adversely affected. Further, it is considered that this is a cause of occurrence of peeling or cracking of the film of each layer. When such an adverse effect occurs, exchange coupling between crystal grains cannot be sufficiently reduced, and a high S / N ratio cannot be obtained.

  In view of the above, the present invention has an object to manufacture a perpendicular magnetic recording medium having a high S / N ratio by relaxing internal stress generated in the inside or boundary of each layer including a magnetic layer during film formation. It is to propose a possible method.

  In order to solve the above problems, the present invention provides a substrate, a base layer containing a hexagonal metal formed on the substrate, and a columnar magnetic crystal particle formed on the base layer and containing a hexagonal metal. And a magnetic layer including an oxide and a magnetic layer having a grain boundary section that partitions the magnetic crystal grains, wherein the magnetic layer is formed on a heated underlayer It is characterized by.

  That is, in the present invention, the hexagonal underlayer is subjected to heat treatment before the formation of the magnetic layer containing hexagonal magnetic crystal grains (also simply referred to as crystal grains) that are mutually partitioned by oxide grain boundaries. One of the features.

  Since the hexagonal underlayer is subjected to heat treatment, the vertical orientation of the hexagonal underlayer is improved, so that Δθ50 (an index indicating the degree of crystal orientation) of the hexagonal underlayer (0002) is narrow. It has become.

  Hexagonal magnetic particles are grown epitaxially with respect to the hexagonal underlayer. Since the vertical orientation of the hexagonal underlayer is improved by heat treatment, the vertical orientation of the hexagonal magnetic crystal grains that are epitaxially grown can be improved. Therefore, Δθ50 (an index indicating the degree of crystal orientation) of the (0002) plane of hexagonal magnetic crystal grains is narrow. The angle is preferably within 4.0 degrees. The magnetic crystal grains are formed in a column shape extending vertically upward with respect to the substrate surface.

  The method for heat-treating the hexagonal underlayer is not particularly limited, but the hexagonal underlayer may be heated, a method of forming a hexagonal underlayer on a preheated substrate, Alternatively, a method may be used in which a film formed between the first and second hexagonal underlayers is heated and a hexagonal underlayer is formed thereon.

  According to the present invention, it is possible to relieve the film stress at the boundary between the hexagonal underlayer and at least the hexagonal magnetic crystal grains.

  It was confirmed that if the substrate surface was heated before the magnetic layer was formed, distortion and defects due to thermal expansion during the film formation could be removed, and the crystal orientation could be controlled by the annealing effect. Therefore, by appropriately setting the heating temperature, the crystal orientation of the magnetic layer having a granular structure can be improved to make the crystal grains uniform, and the film can be formed without peeling and cracking. Therefore, a magnetic layer having a granular structure in which exchange coupling between crystal grains is sufficiently reduced can be formed, so that the S / N ratio of the perpendicular magnetic recording medium can be improved.

  Here, the granular structure includes the above-described columnar magnetic crystal grains containing the hexagonal metal and the grain boundary part containing the oxide and partitioning the magnetic crystal grains.

  In the present invention, when a soft magnetic layer is provided between the substrate and the underlayer, the soft magnetic layer is formed between the soft magnetic layer and the underlayer, or the underlayer is formed. It is preferable to heat the substrate between the film process and the film formation process of the magnetic layer. The hexagonal metal contained in the magnetic crystal grains is preferably Co, and the oxide contained in the grain boundary part is preferably silicon oxide. Furthermore, it is preferable that the hexagonal metal contained in the underlayer is Ru.

  Here, in the perpendicular magnetic recording medium, a soft magnetic layer may be formed below the underlayer in order to improve the recording / reproducing characteristics by controlling the magnetic flux from the magnetic head used for magnetic recording. In this case, a heating process for heating the surface of the substrate may be performed at a time between the film forming process of the soft magnetic layer and the film forming process of the underlayer.

  Further, a seed layer may be formed between the soft magnetic layer and the underlayer in order to control the crystal orientation of the underlayer. In this case, the surface of the substrate may be heated at a point between the soft magnetic layer forming step and the seed layer forming step.

  Next, in the heating process of the present invention, it is desirable to heat the substrate so that the surface temperature is 130 ° C. or higher. In a general film formation process, the substrate surface temperature is about 100 ° C., but by heating the substrate surface to a temperature higher than this, the crystal orientation of the underlayer and the magnetic layer can be improved. .

  Specifically, the crystal orientation in the magnetic recording medium is evaluated with an X-ray diffractometer, and the value of the half-value width Δθ50 of the rocking curve of (0002) diffraction between the magnetic layer and the underlayer is 4.0 degrees or less, preferably It is desirable to adjust the surface temperature of the non-magnetic substrate obtained by the heating step so that it falls within the range of 2.5 to 4.0 degrees.

  Further, the thickness of the soft magnetic layer in the film forming process may be increased so that the surface temperature of the substrate rises to the heating temperature obtained through the heating process. In a film forming process such as sputtering that is generally employed, when the film thickness is increased, the substrate surface temperature is increased accordingly. Therefore, even when the film thickness is set so that a suitable heating temperature can be obtained, the same effects as in the case of directly heating the substrate surface using a heater can be obtained.

  In the method for producing a perpendicular magnetic recording medium of the present invention, the hexagonal underlayer is heat-treated before the formation of a magnetic layer containing hexagonal magnetic crystal grains (also simply referred to as crystal grains) partitioned by oxide grain boundaries. It is characterized by having received. Since the hexagonal underlayer is subjected to a heat treatment, the vertical orientation of the underlayer is improved, so the Δθ50 (an index indicating the degree of crystal orientation) of the hexagonal underlayer (0002) plane is narrowed. The film stress at the boundary between the hexagonal underlayer and at least the hexagonal magnetic crystal grains can be relaxed.

  Therefore, according to the present invention, since the magnetic layer and / or the underlayer can be formed without generating a large internal stress, the crystal orientation of these layers can be improved and the crystal grains can be made uniform. In addition, these layers can be formed without peeling or cracking. As a result, the S / N ratio of the perpendicular magnetic recording medium can be further increased, which is suitable for manufacturing a perpendicular magnetic recording medium having a high recording density of, for example, 150 GB / square inch or more.

  FIG. 1 is a schematic sectional view showing an embodiment of a perpendicular magnetic recording medium manufactured according to the present invention. A perpendicular magnetic recording medium 10 according to the present embodiment includes an adhesion layer 2, a soft magnetic layer 3, a seed layer 4, an underlayer 5, a granular magnetic layer 6, a carbon-based protective layer 7 on a glass substrate 1. The lubricating layer 8 is formed in this order.

  Here, as the glass substrate 1 (nonmagnetic substrate), chemically strengthened glass, crystallized glass, or the like can be used. Instead of the glass substrate 1, a substrate made of Al alloy plated with NiP may be used.

  The adhesion layer 2 is a layer for improving the adhesion of the soft magnetic layer 3, and for example, amorphous Ti or TiCr can be used. The soft magnetic layer 3 is formed in order to improve the recording / reproducing characteristics by controlling the magnetic flux from the magnetic head, and an amorphous Co alloy such as CoNbZr or CoTaZr can be used.

  The seed layer 4 is disposed in order to improve the orientation of the underlayer 5 and to refine the crystal grain size of the underlayer 4, and a Ni alloy such as NiTa can be used. This layer can be amorphous. In the case of a crystal structure, it is an fcc or bcc structure.

  The underlayer 5 is a layer for controlling the crystal orientation, crystal grain size, grain size distribution and the like of the magnetic layer 6. As will be described next, the magnetic layer 6 is a granular perpendicular magnetic recording layer and has an hcp crystal structure. Therefore, the underlayer 5 also preferably has an hcp crystal structure. Is used.

  The magnetic layer 6 has a granular structure having a columnar structure in which magnetic crystal grains are surrounded by nonmagnetic grain boundaries (grain boundary portions). Here, the granular structure is a structure in which magnetic crystal grains are formed in a columnar shape extending vertically upward with respect to the substrate surface. The magnetic crystal grains can be formed from a ferromagnetic material containing Co as a main component, and the nonmagnetic grain boundaries can be formed from an oxide material such as Cr, Si, Ti, or Ta.

  The Co crystal grains of the magnetic layer 6 are epitaxially grown on the Ru crystal grains of the underlayer 5 to form a columnar structure. The nonmagnetic grain boundaries of the magnetic layer 6 are grown on the crystal grain boundaries of the underlayer 5. The width of the crystal grain boundary of the magnetic layer 6 needs to be constant in the film thickness direction from the interface with the underlayer 5.

  Note that the carbon-based protective layer 7 and the lubricating layer 8 can be configured using generally used materials.

  By the way, the foundation layer 5 is composed of two layers, an upper foundation layer and a lower foundation layer. In order to make the magnetic layer 6 have a structure having magnetic crystal grains containing Co and a grain boundary portion made of an oxide surrounding the magnetic crystal grains and partitioning the magnetic crystal grains, the magnetic layer 6 is positioned below the magnetic layer 6. In the underlying layer 5 to be formed, it is necessary to form irregularities that trigger grain formation. In addition, if the magnetic layer 6 having an oxide is formed on the upper underlayer, the crystal orientation is likely to deteriorate. Therefore, it is necessary to increase the crystal orientation of the lower underlayer located below the upper underlayer as much as possible. .

  In order to form a film having high crystal orientation, it is desirable to form the film by sputtering in a low gas pressure atmosphere or by sputtering at a high film formation rate. On the other hand, in order to form surface irregularities, it is desirable to form by sputtering in a high gas pressure atmosphere or sputtering at a low film formation rate. Arise.

  Therefore, in order to achieve both high crystal orientation and formation of surface irregularities, the lower underlayer and the upper underlayer are laminated by different film forming processes. However, when an upper underlayer is formed under high gas pressure on a lower underlayer formed under low gas pressure by experiment, separation of the Ru diffraction peak of the upper underlayer from Ru of the lower underlayer and A shift was confirmed. Thus, since the lattice constant of Ru changes depending on the gas pressure during film formation, it is considered that internal stress is generated when the lower underlayer and the upper underlayer are laminated. In the present invention, heat treatment is performed after high gas pressure film formation (that is, after the underlayer 5 film formation) to remove defects and strain.

  Therefore, in the manufacture of the perpendicular magnetic recording medium 10, the magnetic layer 6 is formed on the heated underlayer 5. The method for heat-treating the underlayer 5 is not particularly limited, but the glass substrate 1 (that is, the underlayer 5) may be heated after the underlayer 5 is formed, or the preheated glass substrate 1 may be heated. A method of forming the underlayer 5 on the substrate or a film (for example, the soft magnetic layer 3 and the seed layer 4) formed between the glass substrate 1 and the underlayer 5 is heated, and the underlayer 5 is formed thereon. It is also possible to do it.

  It was confirmed that the crystal orientation of the underlayer 5 and the magnetic layer 6 was improved by this heating. Further, it was confirmed that the same effect can be obtained even when the substrate surface temperature before the formation of the underlayer 5 is increased by increasing the thickness of the soft magnetic layer 3.

(Example 1)
A specific manufacturing process of the perpendicular magnetic recording medium having the above configuration will be described.

  First, an amorphous aluminosilicate glass was formed into a disk shape by direct pressing to produce a glass disk. The glass disk was ground, polished, and chemically strengthened in order to obtain a smooth glass substrate 1 made of a chemically strengthened glass disk and having a diameter of 65 mm.

  On the glass substrate 1 obtained, an adhesion layer 2 and a soft magnetic layer 3 were sequentially formed in an Ar atmosphere by a DC magnetron sputtering method using a film forming apparatus that was evacuated. At this time, the adhesion layer 2 was formed using a Ti target so as to be a 20 nm thick Ti layer. The soft magnetic layer 3 is formed using a CoTaZr target so as to be an amorphous CoTaZr (Co: 88 at%, Ta: 7.0 at%, Zr: 4.9 at%) layer having a thickness of 20 nm. did.

  Next, the seed 4 and the underlayer 5 were sequentially formed on the soft magnetic layer 3 by DC magnetron sputtering in an Ar atmosphere.

  First, a 10 nm-thick seed layer 4 made of amorphous NiTa (Ni: 45 at%, Ta: 55 at%) was formed, and then a 30 nm-thick underlayer 5 made of hexagonal metal Ru was formed. For the underlayer 5, first, a lower underlayer is formed, and then the gas pressure higher than the gas pressure during the formation of the lower underlayer (or the film formation rate during the formation of the lower underlayer). The upper underlayer was formed at a low film formation rate.

  The perpendicular magnetic recording medium substrate thus formed up to the underlayer 5 was taken out of the film forming apparatus, and the substrate surface was heated using a heating device. The heating conditions will be described later.

Next, a magnetic layer 6 having an hcp crystal structure of 15 nm was formed on the underlayer 5 using a ferromagnetic target containing SiO ₂ and CoCrPt. The composition of the target for forming the magnetic layer 6 was Co: 62 at%, Cr: 10 at%, Pt: 16 at%, SiO ₂ : 12 at%, and the film was formed at a gas pressure of 4 Pa.

  Next, a carbon-based protective layer 7 made of hydrogenated carbon and having a thickness of 4.5 nm was formed by sputtering a carbon target using a mixed gas containing 18 vol% hydrogen in Ar.

  Finally, a lubricating layer 8 made of PFPE (perfluoropolyether) was formed by dip coating. The thickness of the lubricating layer 8 was 1 nm.

  Here, in such a manufacturing process, the heating conditions are changed in the heating process immediately after the formation of the underlayer 5 (immediately before the formation process of the magnetic layer 6), thereby changing the crystal orientation of the underlayer 5 and the magnetic layer 6. Examined. In order to evaluate crystal orientation, orientation Δθ50 by X-ray analysis evaluation was measured.

  Δθ50 refers to the half width of the rocking curve for Co, Ru (0002) diffraction observed by X-ray diffraction measurement (2θ / θ). The rocking curve is measured by changing θ (X-ray incident angle) while fixing 2θ (detection angle) at the intensity peak angle of (0002) diffraction of Co and Ru. From this measurement, the strength variation of each Co and Ru with respect to the (0002) disk surface can be evaluated.

  FIG. 2 is a chart showing an example of measurement results. In the illustrated example, the heater output is switched to 200 W, 400 W, 600 W, 800 W and 1000 W in the heating process, and the substrate surface temperature is heated to 130 ° C., 190 ° C., 250 ° C., 300 ° C. and 360 ° C., respectively. It is. From these measurement results, it was confirmed that the Ru crystal orientation of the underlayer 5 and the Co crystal orientation of the magnetic layer 6 were improved as the substrate surface temperature increased. Further, it was confirmed that if the substrate surface temperature is 130 ° C. or higher, Δθ50 can be made 4.0 degrees or less. Furthermore, in consideration of other parameters such as magnetic characteristics, the substrate surface may be heated so that the value of Δθ50 is 4.0 degrees or less, preferably 2.5 to 4.0 degrees. Desirable.

(Example 2)
Next, an example of a method for manufacturing a perpendicular magnetic recording medium including the step of increasing the substrate surface temperature by increasing the thickness of the soft magnetic layer 3 will be described.

  That is, in Example 1, the CoTaZr target is used so that the soft magnetic layer 3 becomes an amorphous CoTaZr (Co: 88 at%, Ta: 7.0 at%, Zr: 4.9 at%) layer having a thickness of 20 nm. A film was formed. In Example 2, the change in crystal orientation of the underlayer 5 and the magnetic layer 6 was measured by changing the film thickness in the film forming process of the soft magnetic layer 3. The crystal orientation was measured by measuring the orientation Δθ50 by X-ray analysis evaluation.

  FIG. 3 is a chart showing an example of measurement results. The illustrated example is a result when the thickness of the soft magnetic layer 3 is changed to 20 nm, 40 nm, 80 nm, and 120 nm in the film forming process of the soft magnetic layer 3. When the film thickness was 20 nm, the substrate surface temperature was 100 ° C. However, when the film thickness was 40 nm, 80 nm, and 120 nm, the substrate surface temperature increased to 130 ° C., 180 ° C., and 240 ° C., respectively. It was confirmed that the Ru crystal orientation and the Co crystal orientation of the magnetic layer 6 were improved as the thickness of the soft magnetic layer 4 was increased. Therefore, after the soft magnetic film 3 is formed, instead of heating the substrate surface, the thickness of the soft magnetic layer 3 is increased, whereby the substrate is heated, and the same effect as in the first embodiment can be obtained. .

It is a cross-sectional schematic diagram which shows an example of the perpendicular magnetic recording medium manufactured by this invention. It is a graph which shows the change of the crystal orientation with respect to the heating temperature of a substrate surface. It is a graph which shows the change of the crystal orientation with respect to the film thickness of a soft-magnetic layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Adhesion layer 3 Soft magnetic layer 4 Seed layer 5 Underlayer 6 Magnetic layer 7 Carbon-based protective layer 8 Lubricating layer 10 Perpendicular magnetic recording medium

Claims (6)

A substrate,
An underlayer containing a hexagonal metal formed on the substrate;
A magnetic layer formed on the underlayer and having a columnar magnetic crystal particle containing a hexagonal metal, and a grain boundary part containing an oxide and defining the magnetic crystal particle;
A method of manufacturing a perpendicular magnetic recording medium including:
A method of manufacturing a perpendicular magnetic recording medium, comprising forming the magnetic layer on a heated underlayer. A soft magnetic layer is provided between the substrate and the underlayer,
The substrate is heated between the soft magnetic layer deposition step and the underlayer deposition step or between the underlayer deposition step and the magnetic layer deposition step. The method of manufacturing a perpendicular magnetic recording medium according to claim 1. 3. The perpendicular magnetic recording medium according to claim 1, wherein the hexagonal metal contained in the magnetic crystal grains is Co, and the oxide contained in the grain boundary is silicon oxide. 4. Method. The method for manufacturing a perpendicular magnetic recording medium according to claim 1, wherein the hexagonal metal contained in the underlayer is Ru. 5. The method of manufacturing a perpendicular magnetic recording medium according to claim 1, wherein the magnetic crystal grains are formed in a column shape extending vertically upward with respect to the surface of the substrate. . A perpendicular magnetic recording medium manufactured by the manufacturing method according to claim 1.

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