JP2005056495A - Magnetic recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain sufficient hardness even when a protective layer is formed with ≤3.0 nm thin film. <P>SOLUTION: Since a growth nucleus layer is formed on the lower side of the protective layer to promote growth of an sp3-coupling structure in the vicinity of an interface, the density of the component of the sp3-coupling structure within the protective layer is made nearly uniform without having inclination between the region on the interface side in the protective layer and the region far from the interface and is made higher than the density of a component of an sp2-coupling structure other than the sp3-coupling structure as a main component. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a magnetic recording medium that can be applied to, for example, a hard disk magnetic recording medium constituting a hard disk device, and a method for manufacturing the same, and more particularly to a magnetic recording layer that forms a recording layer having a head impact and external corrosiveness. It has a function of protecting against corrosion, such as material, a method for forming a protective layer rich in sp ³ bonded carbon (sp 3 ^-C).

  Conventionally, a hard disk device is a main external recording device of a computer, and with the progress of multimedia, the recording density, the transfer speed, and the miniaturization are rapidly increasing. As a result, the magnetic recording medium, which is the main component of the hard disk device, also has a need to maintain tribological mechanical strength as the surface recording density is improved and the flying height of the magnetic head is reduced.

With respect to magnetic recording media, there is a demand for further reduction in film thickness and accompanying increase in hardness. In order to maintain the high hardness of the magnetic recording medium, it is essential to improve the protective layer constituting the medium.
Conventionally, carbon (C) is used for the protective layer as a component element, and film formation is currently performed by sputtering or plasma CVD.
Further, as a magnetic recording medium, in order to further form a protective layer of carbon system having high durability, rich in sp ³ bonded carbon ^{(sp 3 -C), ta-} C ( tetrahedral amorphous high hardness The application of carbon) is also being studied, and research by vacuum arc deposition is being conducted.

  FIG. 7 shows a phase diagram of a carbon-based composition used as a conventional protective layer (see, for example, Non-Patent Document 1).

Each vertex of the triangle corresponds to diamond, graphite, and hydrogen (H), respectively. Ta-C contains almost no hydrogen in the bulk, is rich in sp ³ -bonded carbon, and has a feature of being very dense and hard like diamond.

  Patent Document 1 and Patent Document 2 describe an invention in which a carbon film containing hydrogen (Diamond-Like Carbon: DLC) is formed on Si to improve the adhesion of DLC.

JP-A 64-76423 Japanese Patent Laid-Open No. 6-111287 PHYSICAL REVIEWWB, Vol. 61. No. 20, p14095

FIG. 8 shows the ta-C film with respect to the ratio of sp ³ -bonded carbon of ta-C as a protective layer directly formed on the magnetic layer (= sp ³ -bonded carbon / [sp ³ -bonded carbon + sp ² -bonded carbon]). The dependence of film thickness is shown.
sp ³ ratio bond carbon, the Cls peak of the carbon as measured by X-ray photoelectron spectroscopy, sp ³ bonded carbon component (around 285.5 eV), waveform separation in the sp ² bonded carbon component (around 284.5 eV) And calculated from the peak area ratio.
The proportion of sp ³ -bonded carbon depends on the thickness of the ta-C film, and is 80% or more at 3.0 nm or more, but the proportion of sp ³ -bonded carbon is very small at 3.0 nm or less. A film rich in sp ³ -bonded carbon, which is the original characteristic, cannot be obtained.

FIG. 9 shows the relationship between the proportion of sp ³ bonded carbon and the hardness.

From FIG. 9, it can be seen that in a carbon film (film thickness of about 100 nm), if the proportion of sp ³ bonded carbon is small, the hardness is low, and it cannot be applied to a protective layer that requires high durability.

As can be seen from FIGS. 8 and 9 above, when the thickness of the ta-C film is 3.0 nm or less, the ratio of sp ³ -bonded carbon is drastically reduced, so that the hardness is also drastically lowered. As a result, there is a problem in that it cannot be applied as a protective layer of a magnetic recording medium because sufficient hardness cannot be obtained in a thin film state of 3.0 nm or less.

  Accordingly, an object of the present invention is to provide a magnetic recording medium capable of obtaining sufficient hardness even when the protective layer is formed of a thin film having a thickness of 3.0 nm or less, and a manufacturing method thereof.

  The present invention is a magnetic recording medium in which at least an underlayer, a magnetic recording layer, and a protective layer are laminated on a nonmagnetic substrate, and the protective layer is interposed between the magnetic recording layer and the protective layer. A growth nucleus layer that promotes the growth of only the component of the predetermined structure among the plurality of structures constituting the structure is provided, wherein the protective layer has a growth of the component of the predetermined structure with the growth nucleus layer. By being promoted in the vicinity of the interface, the density of the components of the predetermined structure is made substantially uniform with no inclination between the region on the interface side in the protective layer and the region away from the interface. In addition, the magnetic recording medium is configured by maintaining the hardness of the protective layer formed by the main component higher than the density of the components of the other structural body other than the predetermined structural body. .

Here, the growth nucleus layer is formed with sp ³ -bonded Si or sp ³ -bonded C and sp ³ -bonded Si as main components, and the protective layer has sp ³ -bonded as the predetermined structure. You may form as ta-C (tetrahedral amorphous carbon) which has C as a main component.

  The protective layer may have a thickness of 3.0 nm or less, and the growth nucleus layer may have a thickness of 1.0 nm or less.

The present invention relates to a manufacturing method for producing a magnetic recording medium in which at least an underlayer, a magnetic recording layer, and a protective layer are laminated on a nonmagnetic substrate, and an sp ³ bonded Si is formed on the magnetic recording layer. or a step of forming a growth nucleus layer composed mainly of C and sp ³ bonds of Si sp ³ bonds, the growth nucleus layer, ta-C (tetra mainly composed of C of sp ³ bonds A step of forming a protective layer made of a helical amorphous carbon), wherein the protective layer is formed by promoting the growth of sp ³ -bonded C in the vicinity of the interface with the growth nucleus layer. The density of C in the sp ³ bond is substantially uniform with no inclination between the region on the interface side in the protective layer and the region away from the interface, and other than the sp ³ bond is a more principal component than the density of sp ² bonds and C, thereto By keeping the hardness of the protective layer above a certain level, which is formed Ri, to provide a method of manufacturing a magnetic recording medium.

As described above, according to the present invention, the growth nucleus layer is formed below the protective layer, and the growth of the sp ³ bond structure is promoted near the interface. ³ density of the components of the structure of the coupling, a substantially uniform state without a slope between the interface side of the region and the region away from the interface of the protective layer, and, sp ³ bond The main component can be larger than the density of the component of the sp ² bond structure other than the structure, whereby a sufficient hardness can be obtained even in a protective film having a thickness of 3.0 nm or less. The durability as a medium can be greatly improved.

  A first embodiment of the present invention will be described.

(Overview)
The outline of the present invention will be described.

In order to form a protective layer made of a ta-C film having original characteristics rich in sp ³ -bonded carbon even in a thin film state (initial growth stage) such as a film thickness of 3.0 nm or less, it is made of a ta-C film. A growth nucleus layer mainly composed of an Si-based compound having sp ³ bonds (that is, sp ³ bonded Si or sp ³ bonded C and sp ³ bonded Si) is provided below the protective layer.

In this way, by forming a growth nucleus layer having sp ³ bonds below the protective layer made of the ta-C film, the growth of sp ³ bond carbon of the ta-C film is promoted, and the growth of 3.0 nm or less Even in such a thin film state, a ta-C film rich in sp ³ -bonded carbon can be formed as in the case of 3.0 nm or more. Thereby, the hardness of the film of the protective layer can be increased, and the durability as a magnetic recording medium can be improved.

The ta-C film of the protective layer contains almost no hydrogen in the carbon film, and the formation of the Si-based film of the growth nucleus layer is an introduction means for promoting the growth of sp ³ bonds in the ta-C film. is there.

(Structure of magnetic recording medium)
The structure of the magnetic recording medium according to the present invention will be described.

  FIG. 1 shows a cross-sectional structure of a magnetic recording medium.

In the magnetic recording medium 1, a plating layer 3, an underlayer 4, a magnetic recording layer 5, a growth nucleus layer 6, a carbon protective layer 7, and a liquid lubricating layer 8 are sequentially laminated on a nonmagnetic substrate 2.
Growth nucleus layer 6 is amorphous structure, sp ³ bonds of Si, or, sp ³ bond C (i.e., sp ³ bonded carbon) and a composition whose main component and sp ³ bonds Si.

The growth nucleus layer 6 has a function of promoting the growth of only the C component of sp ³ bond among the plurality of structures constituting the carbon protective layer 7.
The film thickness of the growth nucleus layer 6 is preferably 1.0 nm or less. When the film thickness is 1.0 nm or more, the total film thickness of the growth nucleus layer 6 and the carbon protective layer 7 becomes thick, which is contrary to the thinning of the entire protective film.

The carbon protective layer 7 is formed as ta-C (tetrahedral amorphous carbon) containing sp ³ -bonded C as a main component. The composition ratio of the ta-C film is determined by the ratio of sp ² -bonded carbon and sp ³ -bonded carbon as shown in FIG. 7 described above. In this example, at least 60% or more of sp ³ -bonded carbon is included. ing.

  The carbon protective layer 7 has a function of protecting the magnetic recording layer 5 forming the recording layer from the impact of the magnetic head and the corrosion of an external corrosive substance.

  The film thickness of the carbon protective layer 7 is 3.0 nm or less, preferably 1 nm to 2 nm.

  Hereinafter, other layers will be described.

  The nonmagnetic substrate 2 may be any conventional nonmagnetic substrate such as an aluminum alloy, glass, or plastic substrate. Specific examples of the plastic substrate include substrates made of polycarbonate, polyolefin, polyethylene terephthalate, polyethylene naphthalate, polyimide, and the like.

  The size of the nonmagnetic substrate 2 may be any size of disk substrate such as 2.5 inches, 3 inches, 3.3 inches, 3.5 inches, and 5 inches. In addition, the magnitude | size shown here is a nominal value and is used widely in the said technique.

The magnetic recording layer 5 includes a ferromagnetic metal that can be used as a recording layer, and specifically includes CoCrTaPt, CoCrTaPt—Cr ₂ O ₃ , CoCrTaPt—SiO ₂ , CoCrTaPt—ZrO ₂ , CoCrTaPt—TiO ₂ , CoCrTaPt—Al _2. A magnetic recording layer containing O ₃ or the like as a component. The film thickness is 20 nm or less, preferably 10 to 20 nm. A plurality of magnetic recording layers 5 may be used to form a multilayered recording layer.

  The underlayer 4 may be formed from any conventional component that forms the underlayer 4, and is not particularly limited. Specifically, it consists of Cr, Cr-W, Cr-V, Cr-Mo, Cr-Si, Ni-Al, Co-Cr, Mo, W, Pt, and the like. The film thickness is 20 nm or less, preferably 10 nm to 20 nm.

  The plating layer 3 is made of an alloy such as Ni-P, for example.

(Significance of the growth nucleus layer)
Next, the reason why the growth nucleus layer 6 is provided will be described.
2A and 2B show the layer structure of the interface region 100 between the growth nucleus layer 6 and the carbon protective layer 7 in comparison with the present invention and the conventional example. 2A shows the present invention, and FIG. 2B shows a conventional example. In FIG. 2, for black and white shading, the black one indicates that there are many sp ³ bonds, and the white one indicates that there are many sp ² bonds.

Ta-C film constituting the carbon protective layer 7 is (in bulk) originally, sp ³ bonds of C (hereinafter, referred to as sp ³ bonded carbon) is a film rich. As shown in the phase diagram of FIG. 7 described above, the film is originally a film having a sp ³ bonded carbon ratio of about 60% to 90%.

However, as shown in the waveform 30 of FIG. 8 described above, in the thin film (that is, the film thickness is 3 nm or less), the proportion of sp ³ bonded carbon is drastically decreased, and the original characteristics (sp ³ bonded carbon It is not a rich film.

Further, as shown in the conventional layer structure of FIG. 2B, the proportion of sp ³ bonded carbon is extremely low in the interface region 100 close to the magnetic recording layer 5 in the carbon protective layer 7, and the original characteristics are obtained. It turns out that it is not ta-C film | membrane. That is, in this conventional protective layer 7, the ratio of upward from the interface of sp ³ bonded carbon is divided into three regions: a minimal region, a small region, and a multi-region.

Therefore, in the present invention, even in the interface region close to the magnetic recording layer 5 (in other words, over the entire film including not only the interface region 100 but also the region away from the interface region 100), the ta-C film. In order to obtain a film rich in sp ³ -bonded carbon, the Ta-C film has a role of assisting the formation of sp ³ -bonded carbon, and the Si-based growth nucleus layer 6 having a sp ³ -bonded structure is formed as ta. Introduced under the -C membrane.

By introducing the growth nucleus layer 6, as shown in FIG. 2A, the ta-C film becomes a film rich in sp ³ bonded carbon even when the film thickness is 3 nm or less. That is, in the carbon protective layer 7 of the present invention, the minimum region and the small region as shown in FIG. 2B do not exist in the ratio of upward from the interface of the sp ³ bonded carbon, the middle region, It consists of an area.

Therefore, in the carbon protective layer 7 of the present invention, the density of the sp ³ -bonded carbon structure is substantially uniform with almost no inclination between the interface region and the region away from the interface.

FIG. 3A schematically shows the structure of the structure near the interface between the growth nucleus layer 6 and the carbon protective layer 7. FIG. 3B shows a structural unit of the structure.
Near the interface of the carbon protective layer 7, sp ² -bonded carbon 10 and sp ³ -bonded carbon 20 exist, but the density of sp ³ -bonded carbon 20 is mainly larger than the density of sp ² -bonded carbon 10. It is an ingredient. This is because the growth of sp ³ bonded carbon 20 is promoted near the interface with the growth nucleus layer 6.

As described above, by introducing the growth nucleus layer 6, the ta-C film can increase the proportion of sp ³ bonded carbon in the entire film. In this example, by setting at least 60% or more of sp ³ bonded carbon in the ta-C film as a main component, a certain level of hardness can be maintained from FIG. This certain hardness or higher means that the film is formed as a film having a hardness high enough to be used as a protective film of the magnetic recording medium 1.

(Thinning of protective layer)
Next, the thinning of the carbon protective layer 7 will be described.

4 and 5 show the relationship between the thickness of the growth nucleus layer 6 and the ratio of the ta-C film constituting the carbon protective layer 7 and sp ³ bonded carbon.

Figure 4 is a growth nucleus layer 6 is an example of a SiC (i.e., consisting of C and sp ³ bonds of Si sp ³ bond). FIG. 5 shows an example in which the growth nucleus layer 6 is Si (that is, made of sp ³ -bonded Si).

  A waveform 30 shows a relationship when the thickness of the growth nucleus layer 6 is 0 nm (that is, a conventional layer structure). A waveform 31 indicates the relationship when the thickness of the growth nucleus layer 6 is 0.5 nm, a waveform 32 indicates a relationship when the thickness of the growth nucleus layer 6 is 0.8 nm, and a waveform 33 indicates a relationship when the thickness of the growth nucleus layer 6 is 1.0 nm. .

From the above, the waveforms 31 to 33 indicate that, when the growth nucleus layer 6 is SiC or Si, when the thickness of the ta-C film changes in the range of 1.0 nm to 3.0 nm, the sp ³ bonded carbon is It turns out that the ratio of the composition changes in the range of 60% to 85%. Changes within this range are characteristics that do not exist in the conventional waveform 30.

The fact that the ratio of the density of sp ³ bonded carbon is in the range of 60% to 85% indicates that the hardness is 60 to 80 (GPa) from FIG. 9 described above, and a high hardness can be maintained.

  FIG. 6 shows changes in the amount of wear when the thickness of the ta-C film of the carbon protective layer 7 is 1.5 nm and the thickness of the growth core layer 6 of SiC and Si is 0.5 nm to 1.0 nm. FIG. 6 shows the carbon wear amount normalized by setting the wear amount of the comparative example to 1. As can be seen from FIG. 6, the amount of wear can be kept below a certain level. A waveform 40 is an example of SiC, and a waveform 41 is an example of Si.

  As described above, it can be seen that even when the thickness of the ta-C film of the carbon protective layer 7 is set to 3.0 nm or less, a certain level of hardness can be obtained. This hardness can be easily realized even when the thickness of the growth nucleus layer 6 is 1.0 nm or less.

  Therefore, since the thickness of the ta-C film can be set to 3.0 nm or less, the entire protective film can be thinned, and the magnetic recording medium 1 can be thinned.

  Thereby, the magnetic recording medium 1 can be configured as a hard disk device including an ultra-thin hard disk magnetic recording medium, and has a certain degree of hardness and excellent wear resistance. The magnetic recording layer 5 forming the recording layer can be protected from the impact of the magnetic head and the corrosion of corrosive substances in the outside world, and the reliability of the medium can be improved.

(Prototype example 1)
Next, as a manufacturing method, a prototype example of the magnetic recording medium 1 will be described.

  The Ni—P plating layer 3 is applied on the 3.5 inch aluminum alloy substrate 2. On the plating layer 3, a base layer 4 made of Cr having a thickness of 20 nm is deposited by sputtering and a magnetic recording layer 5 made of Co alloy having a thickness of 10 nm is deposited by sputtering.

Then, on the magnetic recording layer 5, a growth nucleus layer 6 mainly composed of sp ³ -bonded SiC is formed by sputtering to a thickness of 0.8 nm.
A carbon protective film 7 made of a ta-C film (tetrahedral amorphous carbon) having a thickness of 1.5 nm is formed on the growth core layer 6 by a FCA (Filtered Cathodic Arc) method which is one of vacuum arc deposition methods. Filmed.

  Using the magnetic recording medium 1 thus produced, the following evaluation test was performed.

First, the proportion of sp ³ bonded carbon in the carbon protective layer 7 was measured by X-ray photoelectron spectroscopy.

The Cls peak of carbon was waveform-separated into a component of sp ³ bonded carbon (near 285.5 eV) and a component of sp ² bonded carbon (near 284.5 eV), and calculated from the peak area ratio. The proportion of sp ³ bonded carbon components was about 71%. It can be seen that this ratio is within the range of the thin film of 3.0 nm or less shown in the waveforms 31 to 33 in FIG.

Next, a durability test was performed to evaluate the wear resistance as shown in FIG.
Using a sample without a lubrication film, slide a head with a SUS (stainless steel) ball with a constant load, measure the P-wave reflectance near the sliding part with OSA (Optical Surface Analyzer), and peak the reflectance. The area was relatively compared and evaluated as the amount of carbon wear.

  As can be seen from the waveform 40 in FIG. 6, the normalized carbon wear amount was 0.42 when the wear amount of the comparative example was 1.

(Prototype example 2)
The growth nucleus layer 6 of the magnetic recording medium 1 was configured as a composition mainly composed of sp ³ -bonded Si. The other layer configuration and manufacturing method are the same as those of the above-described prototype example 1.
As an evaluation test, measurement of the proportion of sp ³ bonded carbon in the carbon protective layer 7 and evaluation of wear resistance were carried out in the same manner as in Prototype Example 1.
The proportion of sp ³ bonded carbon components was about 65%. It can be seen that this ratio is within the range of the thin film of 3.0 nm or less shown in the waveforms 31 to 33 in FIG.

  Further, as can be seen from the waveform 41 in FIG. 6, the normalized carbon wear amount was 0.53 when the wear amount of the comparative example was 1.

(Comparative example)
As a comparative example with respect to the prototype, a conventional magnetic recording medium was manufactured. The magnetic recording medium was manufactured in the same manner as in Prototype Example 1 except that the growth nucleus layer 6 was not formed.
The proportion of sp ³ bonded carbon components was about 15%. As can be seen from the values in FIG. 9, it can be seen that the hardness is extremely low. The normalized carbon wear amount is set to 1 as a comparative example, and it can be seen that the wear amount is large.

The present invention relates to a magnetic recording medium that can be applied to, for example, a hard disk magnetic recording medium constituting a hard disk device, and a method for manufacturing the same, and more particularly to a magnetic recording layer that forms a recording layer having a head impact and external corrosiveness. has a function of protecting against corrosion, such as material, by providing a method of forming the protective layer rich in sp ³ bonded carbon (sp 3 ^-C), even when formed by the following film 3.0nm protective layer A sufficient hardness can be obtained.

1 is a cross-sectional view showing a schematic configuration of a magnetic recording medium according to the present invention. It is explanatory drawing which shows the density change in the interface vicinity of a protective layer compared with a prior art example. It is explanatory drawing which shows typically the structure in the interface vicinity of a protective layer. When growth nucleus layer is SiC, which is a characteristic diagram showing the relationship between the ratio of ta-C film thickness and sp ³ bonded carbon. It is a characteristic view showing the relationship between the film thickness of the ta-C film and the proportion of sp ³ bonded carbon when the growth nucleus layer is Si. It is a characteristic view showing the relationship between the film thickness of the growth nucleus layer and the normalized amount of carbon wear when the ta-C film is formed as a thin film. It is a phase diagram of a carbon system. It is a characteristic diagram showing the relationship between the ratio of the conventional ta-C film thickness and sp ³ bonded carbon. It is a characteristic view which shows the relationship between the ratio of sp ³ bond carbon, and hardness.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic recording medium 2 Nonmagnetic substrate 3 Plating layer 4 Underlayer 5 Magnetic recording layer 6 Growth nucleus layer 7 Carbon protective layer 8 Liquid lubricating layer 10 sp ² bonded carbon 20 sp ³ bonded carbon 100 Interface region

Claims (5)

A magnetic recording medium in which at least an underlayer, a magnetic recording layer, and a protective layer are laminated on a nonmagnetic substrate,
Between the magnetic recording layer and the protective layer, provided is a growth nucleus layer that promotes the growth of only a component of a predetermined structure among the plurality of structures constituting the protective layer,
Here, the protective layer is
The growth of the component of the predetermined structure is promoted in the vicinity of the interface with the growth nucleus layer, so that the density of the component of the predetermined structure is reduced from the region on the interface side in the protective layer and the interface. The protective layer formed by using a main component that is substantially uniform with no inclination with respect to a distant region and has a density higher than that of components of other structures other than the predetermined structure. A magnetic recording medium characterized in that the hardness of the magnetic recording medium is kept above a certain level. The growth nucleus layer is formed with sp ³ -bonded Si or sp ³ -bonded C and sp ³ -bonded Si as a main component,
The magnetic recording medium according to claim 1, wherein the protective layer is formed as ta-C (tetrahedral amorphous carbon) containing sp ³ -bonded C as a main component as the predetermined structure.   The magnetic recording medium according to claim 1, wherein the protective layer has a thickness of 3.0 nm or less.   4. The magnetic recording medium according to claim 1, wherein the growth nucleus layer has a thickness of 1.0 nm or less. A manufacturing method for producing a magnetic recording medium in which at least an underlayer, a magnetic recording layer, and a protective layer are laminated on a nonmagnetic substrate,
The magnetic recording layer, sp ³ bonds of Si, or, forming a growth nucleus layer composed mainly of C and sp ³ bonds of Si sp ³ bonds,
Forming a protective layer composed of ta-C (tetrahedral amorphous carbon) containing sp ³ -bonded C as a main component on the growth nucleus layer,
Here, the protective layer is
The growth of the sp ³ -bonded C is promoted near the interface with the growth nucleus layer, so that the density of the sp ³ -bonded C is separated from the region on the interface side in the protective layer and the interface. Hardness of the protective layer formed by being substantially uniform with no inclination between the regions and having a main component higher than the density of C of other sp ² bonds other than the sp ³ bond Is maintained at a certain level or more, and a method for manufacturing a magnetic recording medium.

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