WO1999045536A1

WO1999045536A1 - Magnetic recording medium, method of production thereof, and magnetic storage

Info

Publication number: WO1999045536A1
Application number: PCT/JP1998/004038
Authority: WO
Inventors: Yoshinori Honda; Yuuichi Kokaku; Mitsuhiro Syouda; Toshinori Ohno
Original assignee: Hitachi, Ltd.
Priority date: 1998-03-04
Filing date: 1998-09-09
Publication date: 1999-09-10
Also published as: WO1999045537A1

Abstract

The surface of a substrate for a magnetic recording medium is processed with a plasma so as to impart an arbitrary uniform surface roughness to the substrate without removing principal elements in the surface of the substrate with ions or free radicals in the plasma. It has become possible to prevent the adhesion of a magnetic head to the magnetic recording medium, enhance the reliability, to lower the flying height of the magnetic head, to increase TPI through the isotropy of the magnetic characteristics, and to lower the noise of recording. Also a highly reliable magnetic storage having a high recording density can be realized.

Description

Light

Magnetic recording medium, method of manufacturing the same, and magnetic storage device using the same

Technical field

The present invention relates to a magnetic storage device such as a magnetic disk device, and further relates to a magnetic storage device.

The present invention relates to a magnetic recording medium used for a head assembly of a device and a manufacturing method thereof. In particular, it relates to an inexpensive and high-quality magnetic recording medium capable of high-density recording, a manufacturing method thereof, and an HDD using the magnetic recording medium.

Background art

In recent years, with the increase in the amount of information and the increase in transmission speed, the importance of increasing the density and speed of magnetic storage devices used as external storage devices for computers has been increasing more and more.

In general, a magnetic disk drive mainly includes a magnetic disk 1 and a magnetic head 2 that floats on the magnetic disk 1 for recording and reproduction, as shown in FIG. 12, and also rotates the magnetic disk 1 It consists of a rotating mechanism 3, a head positioning mechanism (servo mechanism) 4 for positioning the magnetic head 2 on the rotating magnetic disk 1, and an RZW signal circuit 5 for recording and reproducing from the magnetic disk using a magnetic head. You. Here, the floating gap between the magnetic disk 1 and the magnetic head 2 has become less than 0.05 m due to the increase in recording density. It is desired to guarantee the sliding reliability at the time of contact.

Conventionally, a configuration of a magnetic recording medium and a method of manufacturing the same have been proposed for these measures. Various proposals have been made for the purpose. The magnetic recording medium is composed of a substrate and a layered structure such as a magnetic film and a protective film formed on the substrate.Fine abrasive grains are applied to the surface of the substrate to prevent the magnetic head and magnetic disk from attracting. The method of forming fine grooves by circumferential or non-directional polishing called texture by the machining method used has been generally adopted. Other methods include so-called deposition texture, in which fine projections are formed on the surface of the substrate or magnetic film by sputtering, or DRY etching after coating the surface with teflon particles after forming the protective film. There is a method such as the so-called etching texture method of forming irregularities on the surface of a protective film by etching by an etching method. Examples of these methods are disclosed in Japanese Patent Application Laid-Open Nos. And Japanese Patent Laid-Open No. 58-53026.

In either method, the purpose is to prevent adhesion between the magnetic head and the magnetic disk and to ensure reliability by contact start / stop (hereinafter referred to as CS / S). Needs a certain height. As a result, the flying height of the magnetic head cannot be reduced below the height of the unevenness, and the low flying height of the magnetic head required to achieve the high recording density required today is reduced. There was a problem that I could not do it. In other words, the flying characteristics of the conventional magnetic head depend on the height at which contact between the magnetic head and the magnetic recording medium starts (hereinafter referred to as H to), the protective film thickness on the magnetic film, and the lubricating film thickness. Defined. As a result, conventionally, the limit of H to was about 2 O nm. This is because it is difficult to reduce the surface roughness of the magnetic recording medium to a certain value or less, and the burrs that occur when processing the substrate cause the center line average roughness (R a) to be small even if the center line average roughness (R a) can be reduced. The reason is that the peak height (R p) and the maximum peak height (R max) have abnormally high values, and the uniformity of the surface shape of the entire substrate cannot be controlled. This phenomenon is The same applies to texture and etching texture. In the case of depot texture, since projections are formed by sputtering, there is a high possibility that projections will grow abnormally, and it is difficult to make them uniform in size. In the case of the etching texture, the height of the hill for etching the protective film and the film thickness of the etched surface cannot be absolutely reduced from the viewpoint of adhesion and strength, and the roughness of the substrate also cannot be reduced. The height of the hill is limited to about 10 nm because it appears to be transferred to the protective film surface, and the remaining film thickness needs to be about 10 to 15 nm, making it difficult to improve the flying characteristics. Regarding the uniformity of the hills, secondary and tertiary agglomeration cannot be avoided because the fine particles are applied and masked. This allows thermal aspirity due to contact between the magnetic head and large hills

(Hereinafter referred to as T.A) is inevitable.

As described above, the conventional technology does not consider the uniformity of the surface of the substrate over the entire surface, so the anti-adhesion and reliability of the magnetic head and magnetic disk, which are increasingly required in recent years, In addition, it is difficult to achieve high recording density by lowering the height of the magnetic head. Disclosure of the invention

It is an object of the present invention to solve the problems of the prior art and to achieve ultra-low levitation, high sliding resistance, high TPI and high TPI by eliminating magnetic anisotropy, and reliability with low noise. Another object of the present invention is to provide a magnetic recording medium and a magnetic storage device having high performance. For this purpose, as described above, it is essential to supply a process capable of making the surface of the magnetic disk uneven and uniform in the disk surface and selecting an arbitrary surface roughness.

In the present invention, the basic concept for obtaining a uniform surface is that the height of the concaves and convexes can be controlled uniformly in the plane, and the number of irregularities and the pitch of the irregularities are controlled. The above-mentioned problems of the prior art are solved based on controllability, non-directionality such as machining, improvement of mechanical properties of the surface by processing only the surface, and the present invention. It achieves its purpose.

In the method of forming a medium by sputtering, tracing the surface roughness of the substrate as it is is a fundamental phenomenon.

There are roughly two processing methods. One is a wet chemical treatment method, and the other is a dry method using vacuum and plasma. In wet methods, methods such as etching and plating are the main methods, so control is difficult, there is no stability, and there are significant effects such as contamination of the substrate and necessity of cleaning after processing. As a method of forming the surface shape by a dry method, a physical method using plasma was considered to be easy to control and suitable for arbitrary process construction. Therefore, when the substrate surface was treated with Ar gas using a parallel plate RF etching system, the surface of the substrate was shaved. As shown in the upper part of Fig. 1, the average center of the surface roughness of the substrate before treatment was The position of the average center line of the surface roughness after processing is lower than the position of the line. In other words, it was found that under the conditions that would cause etching, the surface would not be uniform in height of the projections, but only roughened. Thus, by selecting the processing conditions, the present inventors did not change the average center line of the surface roughness of the substrate even after plasma processing, as shown in the lower part of Fig. 1, and changed the surface shape minutely. I found something that could be done. This can be achieved by treating the main constituent elements on the surface of the substrate without erosion by ions or radicals in the plasma.

Further, the present inventors, as shown in FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, FIG. 7, and FIG. The height depends on the processing time and the energy of the plasma to be processed. Tsuchi was found to be dependent on the type of gas being processed and the pressure of the gas. Therefore, it is found that the magnetic recording medium required for the present invention can be obtained by appropriately selecting the processing conditions such as the processing time, the energy of the plasma to be processed, the gas type and the gas pressure, and performing the plasma processing. Was.

This makes it possible to make the pitch finer than was possible with the prior art, and to control very fine irregularities with good reproducibility.

As a result of further study, the cause of the protrusions formed by performing the treatment according to the present invention is that the ions or radicals of the gas excited by the plasma are replaced with some of the constituent elements on the substrate surface or the constituent elements on the surface. It was found that the composition was formed by releasing or increasing the stress and strain of the substrate surface by changing the composition. This is because the release or increase of stress and strain is allowed only above the surface of the substrate, so that a projection is formed upward above the surface. For example, taking the Ni-P substrate surface as an example, Ni is usually an fcc structure, but the structure of Ni-12 wt% P is C22 type. The structure formed by the plating is a group of structures having a strain that has changed from the position shown by the solid line to the position shown by the dotted line by taking M ₃ P (M = N i) shown in FIG. 16 by the heat treatment. Furthermore, the surface of this plating film is flattened by machining, but this results in high mobility, high vapor pressure, and P atoms are easily diffused to the surface. It is considered that it is.

The mechanism when these surfaces are treated with N atoms is that activated N atoms attack P atoms, drive P atoms out of the surface, and N atoms enter instead, as shown in Fig. 17. . As a result, the originally possessed strain of Ni-P is released as shown by the solid line, and the distance between Ni atoms changes, so this change is directed upward to the surface. Therefore, projections are formed on the surface by opening the strain. Further, as shown in Fig. 9, which is a result of measuring the hardness and Young's modulus of the surface treated by the present invention with a thin film hardness tester manufactured by Nanoindenter, the hardness and Young's modulus are clearly improved as compared to before the treatment. Therefore, the effect of alleviating the impact at the time of contact between the magnetic disk and the magnetic head can be greatly expected. This is a clear effect due to the change in morphology accompanying the change in the composition of the substrate surface. Therefore, improvement in scratch resistance and crashability can be expected. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing a roughness curve in the processing of the present invention with “Etchin moat”. FIG. 2 is a diagram showing a relationship between plasma power and surface roughness.

FIG. 3 is a diagram showing the relationship between the plasma power and the pitch of the minute projections. FIG. 4 is a diagram showing the relationship between plasma treatment time and surface roughness.

FIG. 5 is a diagram showing the relationship between the plasma processing time and the pitch of the minute projections. FIG. 6 is a diagram showing the relationship between the processing gas pressure and the surface roughness.

FIG. 7 is a diagram showing the relationship between the processing gas pressure and the pitch of the fine projections. FIG. 8 is a diagram showing the relationship of surface roughness.

FIG. 9 is a diagram showing hardness and Young's modulus before and after the treatment of the present invention. FIG. 10 is a diagram showing a manufacturing flowchart of this embodiment and a conventional example. FIG. 11 is a diagram showing AFM images of the substrate surface of the present embodiment and the conventional example. FIG. 12 is a schematic diagram of a magnetic disk drive.

FIG. 13 is a diagram showing processing conditions of the present example and a comparative example.

FIG. 14 is a diagram showing evaluation results for the present example and the comparative example.

FIG. 15 is a schematic view showing a magnetic recording medium according to this embodiment.

FIG. 16 is a schematic structural view of Ni—P in the substrate of the present invention.

FIG. 17 is a structural change model for explaining the mechanism of the present invention .: FIG. 18 is an analysis result of a substrate surface in one embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.

First, we prepared two types of substrates: a Ni-P plating on aluminum, followed by a machined flat surface, and a chemically strengthened glass substrate. The substrate size is 3.5 inches for the aluminum ZN i-P substrate and 2.5 inches for the glass substrate.

After cleaning the substrate with pure water, treatment is performed under the processing conditions shown in Fig. 13 to treat the substrate surface without eroding the main constituent elements on the substrate surface by ions or radicals in the plasma. Was. As a result, Example No.:! Having the mechanical properties and surface state shown in FIG. ~ 10 substrates were made. As a comparative example, as shown in Comparative Examples 1 to 4 in FIG. 13, a substrate (aluminum / Ni-P substrate) having a texture formed by machining, which is a conventional technique, and an untreated glass substrate were prepared. The mechanical properties and surface condition of the substrate were examined. The processing steps after the re-cleaning were the same for the substrate as the comparative example. FIG. 10 is a flowchart comparing the manufacturing process of the present invention with the manufacturing process of the prior art.

From FIG. 13, it can be seen that the mechanical properties of the substrate of this example, the hardness and Young's modulus, are higher than those of the comparative example, and that the surface modification is performed in this example. Here, both properties are improved by 10% or more in this example as compared with the hardness and Young's modulus of the comparative example not treated in the present invention.

Further, it refinement to the number of projections is also formed on the surface of the substrate Izure In this embodiment IX 10 ⁸ pieces / mm ² or more (7 X 10 ⁹ pieces / mm ² or less).

Here, in order to achieve the object of the present invention, the center line average roughness (R a) is 0.15 nm or more and 10 nm or less, and the center line peak height (R p) is 0.3 or more and 20 η. m or less is preferable.

As shown in FIG. 13, in this embodiment, the processing conditions are different depending on the processing method, but the ultimate pressure of the vacuum exhaust is set to 1 E-4 Pa or less.

The treatment of the surface of the substrate is not limited to the treatment method of this embodiment, but may include a plasma etching method, a reactive ion etching method, a reactive ion beam etching method, a chemical assist ion beam etching method, and an ion beam etching method. , A sputter etching method, or an induced plasma method such as ERC and ICP can be used.

Next, the results of an elemental analysis of the surface of the substrate that has been treated according to the present invention using a substrate made of NiP and glass are shown below. Quantitative analysis was performed using ESC A for analysis.

A soda glass substrate processed in the same way as the machined Ni-P plating AL alloy substrate was prepared as a reference. Each processed according to the present invention was processed under the following conditions and analyzed.

Processing condition 1: N i-P substrate, 40 P a (0.3T orr) , RF200W, processing time 70 sec, process gas: N ₂

Processing condition 2: a glass substrate, 26. 6 P a (0.2T orr ), RF200W, processing time 60s ec, process gas were the Ar + O ₂ 10%.

The measuring instrument used for the analysis was Physical Electronics, INC. Quantum 2000. The measurement conditions were a beam diameter of 200 / zm-40w, a target: A1, an excitation source A1Κα, and an extraction angle: 24. , Pulse energy: 3.57Ε-17 J (187.85 eV), step: 2.56E-19 J (1.6 eV).

Figure 18 shows the measurement results. Fig. 18 shows the following.

In the case of the Ni-P substrate, the P concentration of Ni-P on the surface is clearly reduced from 5.89% to 0.58% after treatment, and N increases to 3.15% instead. I have. As a result, the concentration of Ni increases and the surface becomes rich in Ni.

Furthermore, in the case of a glass substrate, Ar and N are not detected, the oxygen concentration increases, and alkali metals such as Na, Cl, and Ca decrease. As a result, the surface of the glass substrate has changed to a composition closer to Si〇2 than the state before the treatment according to the present invention. Thus, it is apparent that the surface composition is obviously changed and the projections are formed by performing the treatment of the present invention.

The effect of a magnetic recording medium in which an underlayer, a magnetic layer, a protective layer, and a lubricating layer are formed using the substrate that has been processed as described above will be described in detail in an example described later. It is known that the shape of the protrusion is maintained as it is, following the shape, and the same evaluation as the substrate surface is possible even after film formation.

Further, from the above results, it is clear that projections can be formed with a change in the composition, and thus, not only the base surface of the magnetic recording medium, but also the underlayer, Since the treatment of the present invention has been shown to be effective for both the magnetic layer and the protective layer, the present invention is not limited to the substrate surface.

Next, as shown in FIG. 15, a magnetic recording medium 1 was obtained by sequentially forming a base film 12, a magnetic film 13 and a protective film 14 on the substrate 11 of this embodiment by a sputtering apparatus. .

The underlayer 12 was sputtered to 30 nm in an Ar gas atmosphere using a Cr target, and the magnetic film 13 was sputtered in an Ar gas atmosphere using a CoCrPt target. And set it to 25 nm. The protective film 14 was sputtered in an Ar gas atmosphere using a graphite target to a thickness of 15 nm. After film formation, the surface of the magnetic recording medium is rubbed and dust is removed while rotating the substrate with a tape with abrasive grains to clean the surface. Was. Thereafter, a fluorine-based lubricant was applied by DiP to a thickness of 15 A, and cured at 80 ° C. in a clean open to form a lubricant film 15. The magnetic recording media of Examples 1 to 10 were evaluated as described below, and the results are shown in FIG.

The evaluation methods include tangential force, CSS resistance, scratch occurrence frequency due to random seek, magnetic head levitation (H to), T.A occurrence frequency, and static magnetic characteristics (H c, S *, B rt) And magnetic anisotropy.

From FIG. 14, it is clear that this example is superior in any of the evaluation results as compared with the comparative example, and it can be seen that the object of the present invention is sufficiently satisfied.

In addition to this embodiment, any other manufacturing method can be used as long as it is a surface treatment method using a plasma in a vacuum, and the latitude in equipment is increased.

In addition, according to the present invention, there is no need for the conventional substrate processing, cleaning process, formation of DEPO-TEX at the time of film formation, etching by applying particles after formation of the protective film, cleaning process, and the like. Can be confirmed. In addition, it has an excellent cost performance.

Furthermore, this embodiment (N o. 5) to have One substrate of the substrate and the comparative example (No. 2), 1 0 micron ² area with the surface state AFM (Atomic Force 'Microscopy copy I) Was measured. The result is shown in Fig. 11 as an image of unevenness. As can be seen from the figure, it is clear that the substrate surface has been subjected to a uniform surface treatment and has extremely fine irregularities due to the treatment in this embodiment.

The underlying film, magnetic film, protective film, and lubricating film of the magnetic recording medium are not limited to those of the present embodiment, but include a two-layer underlying film, an alloy underlying film, a Co-based magnetic film, Protective film, reactive sputter carbon (H2, N2, etc.) It is also possible to use any combination of such as a carbon film containing PCVD) and a PCVD carbon film. In particular, a combination with a carbon protective film containing H2 and N2, which has a high film strength, is even better.

In addition, when combined with LZT (laser zone texture), the CSS zone is LZT and the processing method of the present invention makes it possible to use a processing method of the present invention to create a high-density surface with extremely low levitation. It is clear that recording density media can be made.

Further, by subjecting the substrate to the surface treatment of the present invention, the in-plane magnetic anisotropy of the magnetic layer disappears, and a magnetic recording medium having isotropic magnetic characteristics is obtained.

Therefore, a highly reliable magnetic recording medium with high TPI and low noise due to loss of magnetic anisotropy is obtained. Industrial applicability

According to the present invention, it is possible to realize a magnetic disk medium capable of achieving extremely low flying height and to supply a sufficiently clean substrate without using an unstable and special cleaning technique such as machining. Thus, a cheaper and higher quality magnetic recording medium can be obtained. Therefore, not only can the reliability of the HDD be ensured, but also a system such as a HDD with a high recording density and a high capacity can be supplied.

Further, according to the present invention, the total amount of investment in manufacturing equipment itself is reduced by eliminating the process of machining such as machining in the manufacturing process, and the manufacturing yield power is significantly increased, so that the cost of magnetic disks is reduced. In addition, the cost of HDDs can be greatly reduced.

For this reason, ultra-low flying and compatibility with sliding resistance and T.A. It is possible to provide a highly reliable magnetic recording medium and a magnetic storage device having a high TPI and low noise due to disappearance.

Claims

The scope of the claims

1. In a magnetic recording medium having a base film, a magnetic film, a protective film, and a lubricating film on a non-magnetic substrate, the surface of the substrate is formed on a surface of the substrate by plasma using ions or radicals. A magnetic recording medium characterized in that minute projections are formed by treating the constituent elements without erosion.

2. In a magnetic recording medium having a base film, a magnetic film, a protective film, and a lubricating film on a non-magnetic substrate, minute protrusions are formed on the surface of the substrate, and the constituent elements of the protrusions are other than the protrusions. A magnetic recording medium characterized by being different from a constituent element of a portion.

3. The surface of the substrate has a centerline average roughness (Ra) of 0.15 nm or more and 10 ηm or less, a centerline peak height (Rp) force of 0.3 or more and 20 nm or less, and the number of protrusions is 1 X ^2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium has an isotropic magnetic property of 10 ⁸ pieces / mm ² or more.

4. The surface of the substrate has a centerline average roughness (Ra) of 0.15 nm or more and 10 ηm or less, a centerline peak height (Rp) of 0.3 or more and 20 nm or less, and the number of protrusions is 1 X 3. The magnetic recording medium according to claim 2, wherein the number is 10 ⁸ / mm ² or more, and the magnetic recording medium has isotropic magnetic characteristics.

5. On the surface of the non-magnetic substrate, use plasma and treat the main constituent elements on the surface of the substrate without erosion by ions or radicals in the plasma to form minute projections.

A method for manufacturing a magnetic recording medium, comprising sequentially forming a base film, a magnetic film, and a protective film on the substrate by sputtering, and further forming a lubricating film.

6. Treating the surface of the substrate so that both the hardness and the Young's modulus of the surface of the substrate are improved by at least 10% compared to the hardness and the Young's modulus of the surface of the substrate before the treatment. 6. The method for producing a magnetic recording medium according to claim 5, wherein:

7. The method of manufacturing a magnetic recording medium according to claim 6, wherein an average centerline position of the surface roughness of the substrate is substantially equal to an average centerline position of the surface roughness before the processing.

8. The treatment of the surface of the substrate uses at least one gas of H2, He, N, 〇, F, Ne, Ar, Kr, and Xe. 8. The method for producing a magnetic recording medium according to 7.

9. The surface treatment of the substrate may be performed by a plasma etching method, a reactive ion etching method, a reactive ion beam etching method, a chemical assisted ion beam etching method, an ion beam etching method, a sputter etching method or an induction plasma method. 8. The method for producing a magnetic recording medium according to claim 7, wherein the method is performed by any one of the following methods.

10. A magnetic recording medium, a rotating mechanism for rotating the magnetic recording medium, a magnetic head for levitating above the magnetic recording medium to perform recording and reproduction, and on the magnetic recording medium for rotating the magnetic head In a magnetic storage device composed of a head positioning mechanism for positioning at

The magnetic recording medium is composed of a base film, a magnetic film, a protective film, and a lubricating film on a non-magnetic substrate. A magnetic storage device characterized in that minute projections are formed on the surface of the substrate by processing without eroding constituent elements, and the magnetic storage device has isotropic magnetic characteristics.