JPH0969459A - Manufacturing method of magnetic recording medium - Google Patents

Abstract

(57) Abstract: A disk-shaped magnetic recording medium having uniform magnetostatic characteristics in the circumferential direction is manufactured. SOLUTION: Cathode 3 of magnetron sputtering device
A magnet 6a provided to confine the plasma inside
By arranging 6h alternately in the circumferential direction of the cathode 3 with different polarities, and rotating the central part of the cathode 3 as the center of rotation, a magnetic field is generated in the circumferential direction of the target fixed on the cathode 3. To do. When the Co-Sm alloy magnetic layer is formed, the leakage magnetic field from the rotating magnets 6a to 6h affects the circumferential direction of the substrate surface, and Co-
The easy axis (c-axis) of the Sm-based alloy magnetic layer is oriented in the circumferential direction of the substrate. As a result, a magnetic recording medium having a Co-Sm alloy magnetic layer having uniform magnetostatic properties in the circumferential direction is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magnetic recording medium such as a magnetic disk used in an external recording device such as a computer, and more particularly to a medium having a uniform high coercive force and a high recording density. The present invention relates to a compatible magnetic recording medium manufacturing method.

[0002]

2. Description of the Related Art In recent years, an increase in the amount of information has promoted an increase in the capacity / recording density of magnetic disks used in external recording devices of computers. In general, the linear recording density, the coercive force Hc of the magnetic recording medium, the residual magnetic flux density Br, and the magnetic layer thickness t have the following relationship.

Linear recording density ∝Hc / (Br * t) Therefore, in order to increase the recording density, it is necessary to increase the coercive force of the magnetic recording medium. In order to meet the demand for high coercive force for such magnetic recording media, Co--Cr--Pt based alloy materials having a large crystal magnetic anisotropy, Co--
Sm-based alloy materials are being investigated.

As a Co-Cr-Pt alloy material, Co-C
r-Pt, Co-Cr-Pt-Ta, Co-Cr-Pt-B, Co-Ni-
Cr-Pt and the like are used, but since Pt, which is a very expensive precious metal, is used, a large increase in cost cannot be avoided. On the other hand, various reports have been made in recent years on the magnetic layer material of the Co-Sm type alloy, and its practical application is expected.

For example, Japanese Unexamined Patent Publication No. 2-103717,
JP-A-3-23513, US Pat. No. 5,344,
No. 706 discloses a magnetic recording medium having a high coercive force in which an alloy magnetic layer containing Co and Sm is formed on a nonmagnetic substrate via a nonmagnetic metal underlayer, and a method for producing the magnetic recording medium. Has been done. The inventors of the present application conducted various reproduction experiments with reference to the above literature. As a result, as disclosed in the above document under specific film forming conditions,
It was confirmed that the excellent magnetostatic characteristics of the magnetic layer material of the Co-Sm alloy were obtained.

[0006]

By the way, a magnetron sputtering technique is commonly used for forming such an alloy magnetic layer. This is because a magnet is placed on the back side of the target and the magnetron motion of electrons near the target surface is used to confine the plasma in a donut-shaped space to increase the plasma density and enable efficient sputtering. Therefore, it has advantages such as high film forming speed, less damage to the substrate side, and good reproducibility.

However, when the magnetic layer of Co--Sm alloy is produced by using the magnetron sputtering technique according to the conventional method for producing the magnetic recording medium as described above, the magnetostatic characteristics become non-uniform in the plane of the substrate. It turned out that there is. Various experiments have been tried, but there is a problem that it is not possible to obtain a stable product by suppressing the non-uniformity of the magnetostatic characteristics in the plane of the substrate only by the conditions disclosed in the above-mentioned document.

As a result of repeated experiments, it was found that the static magnetic characteristics are not uniform in the plane of the substrate because the leakage magnetic field from the magnetron type cathode affects the surface of the substrate. FIG. 4A is a cross-sectional view of a magnetron type cathode used in a conventional magnetron sputtering apparatus, and FIG. 4B is a BB arrow view. Magnets 7 and 8 for confining plasma are provided in the cathode 3 located on the back side of the target 5. Due to its structure, a leakage magnetic field is generated in the radial direction of the substrate fixed facing the target 5. Will end up. It is considered that the easy magnetization axis (c-axis) is oriented in the direction of the leak magnetic field in the portion where the leak magnetic field acts on the alloy during film formation, and the easy magnetization direction is provided in the radial direction of the substrate. In particular, Co-Sm type alloys are sensitive to the presence of a magnetic field, and their influence is more remarkable than other alloys.

As a result, in the entire substrate after film formation, a portion in which the easy magnetization direction is in the circumferential direction and a portion in the radial direction are formed at arbitrary radial positions, and the magnetostatic characteristics become non-uniform. . Such non-uniform characteristics in the circumferential direction seriously impair the performance as a magnetic recording medium, and become a major obstacle to realizing high-density and large-capacity magnetic recording and reproduction.

In view of such conventional problems, it is an object of the present invention to provide a method of manufacturing a magnetic recording medium having stable magnetostatic characteristics in the circumferential direction.

[0011]

Therefore, according to the first aspect of the invention, when a magnetic layer containing Co and Sm is formed on a non-magnetic substrate, a magnetic field is applied in the circumferential direction of the substrate. It is characterized by applying. As a result, a magnetic recording medium having uniform magnetostatic properties in the circumferential direction can be obtained.

Further, in the invention according to claim 2, a plurality of magnets having different polarities are alternately provided in the circumferential direction inside the cathode of the sputtering apparatus, and the magnets are rotated around the center of the cathode as a rotation center. The magnetic field is applied in the circumferential direction of the substrate by the leakage magnetic field of the magnet. Thereby, a uniform leakage magnetic field can be formed in the circumferential direction of the substrate.

According to the third aspect of the invention, a plurality of magnets having different polarities are fixed and provided in a circumferential direction inside the cathode of the sputtering apparatus, and the circular magnetic field of the magnets causes a circle of the substrate. It is characterized in that a magnetic field is applied in the circumferential direction. Thereby, a magnetic field can be easily applied in the circumferential direction of the substrate.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. The present invention is to apply a magnetic field in the circumferential direction of the substrate when forming the magnetic layer. In particular,
The cathode magnetic circuit of the magnetron sputtering apparatus was reexamined, and the magnetic layer was formed by using the cathode having a mechanism in which a leak magnetic field acts in the circumferential direction of the substrate.

FIG. 1 is a schematic view showing an example of a magnetron sputtering apparatus used in the method of manufacturing a magnetic recording medium of the present invention. Substrate holder 2 (anode) in chamber 1
The cathode 3 (cathode) is provided to face. The substrate 4 is fixed to the substrate holder 2 with the film forming surface facing the cathode 3 side. On the other hand, a target 5 made of metal (Co, Sm, etc.) as a film forming material is fixed on the upper surface of the cathode 3.

FIG. 2 is a view of the cathode 3 taken along the line AA. Inside the cathode 3 located on the back side of the target 5, magnets 6a to 6h, which are alternately arranged in the circumferential direction of the cathode 3 with different polarities, are arranged in the direction of the arrow R with the center of the cathode 3 as the center of rotation. It is provided to rotate. The magnetic field generated by the rotating magnets 6a to 6h is the target 5
Occurs in the circumferential direction.

In forming the magnetic layer, first, Ar gas is introduced into the vacuumed chamber 1 to maintain a predetermined pressure. Next, when a discharge is generated between the electrodes, A
r Plasma is formed and is confined in the space near the target 5 by the magnetic field generated by the rotating magnets 6a to 6h. Then, the Ar ions in the plasma are accelerated and collide with the target 5, so that the metal that is the film forming material is sputter-evaporated and adheres to the film forming surface of the substrate 4 to form a film.

On the other hand, the leakage magnetic field from the rotating magnets 6a to 6h also affects the circumferential direction of the surface of the substrate 4, and the easy axis (c-axis) of the Co-Sm alloy magnetic layer after film formation is the substrate 4.
To face in the circumferential direction. As a result, a magnetic recording medium having a Co-Sm alloy magnetic layer having uniform magnetostatic properties in the circumferential direction can be stably manufactured. Incidentally, the magnets 6a-6
h may be a permanent magnet or an electromagnet.

When four or more even magnets are used,
It is preferable that the stray magnetic field is well oriented in the circumferential direction of the substrate 4. Further, in the above-mentioned example, the plurality of magnets is configured to rotate inside the cathode, but the plurality of magnets may be provided in the circumferential direction inside the cathode by alternately fixing the magnets with different polarities. A similar effect can be obtained by generating a leak magnetic field in the circumferential direction. In this case, a more uniform magnetic field can be applied by increasing the number of magnets.

[0020]

EXAMPLES An example of a magnetic recording medium manufactured by the manufacturing method of the present invention will be described below. The substrate has a surface roughness Ra of 0.
A 2.5 inch diameter amorphous carbon substrate with a diameter of 5 to 1.0 nm was used. After precision cleaning this amorphous carbon substrate, using the magnetron sputtering device described above,
Film formation was sequentially performed.

The composition of various metals in the magnetic layer was controlled by mounting 5 × 5 × 1 mm chips of other metals on a Co target having a diameter of 5 inches and increasing or decreasing the number of chips.
The film forming conditions for each sample are as follows. [Example 1] (1) First underlayer Material: Ti, substrate temperature: room temperature, Ar gas pressure: 5 mTor
r, substrate bias voltage: 0 V, film thickness: 50 nm (2) Second underlayer material: Cr, substrate temperature: room temperature, Ar gas pressure: 5 mTor
r Substrate bias voltage: 0V, Film thickness: 50nm (3) Magnetic layer Material: Co-Sm (21.2at%), Substrate temperature: Room temperature, Ar
Gas pressure: 5 mTorr Substrate bias voltage: 0 V, film thickness: 30 nm (4) Intermediate layer material: Cr, substrate temperature: room temperature, Ar gas pressure: 5 mTor
r Substrate bias voltage: 0 V, Film thickness: 7 nm (5) Protective layer Material: Amorphous carbon, Substrate temperature: Room temperature, A
r Gas pressure: 5 mTorr Substrate bias voltage: 0 V, film thickness: 10 nm [Example 2] The composition of the magnetic layer was Co-Sm (19.5 at%)-Cr (1.
8 at%) except that the same conditions as in Example 1 were used. [Example 3] The composition of the magnetic layer was changed to Co-Sm (20.9 at%)-Ce (0.
8 at%) except that the same conditions as in Example 1 were used. [Comparative Example 1] A conventional magnetron sputtering apparatus (a leakage magnetic field acts in the radial direction of the substrate) is used, and the other is Example 1.
It was produced under the same conditions as. [Comparative Example 2] The magnetic layer was made of Co-Cr (14at%)-Ta (4at%),
Fabrication was performed under the same conditions as in Comparative Example 1 except that the substrate temperature was 300 ° C. [Comparative Example 3] The magnetic layer was made of Co-Cr (12at%)-Pt (10at%),
It was manufactured under the same conditions as in Comparative Example 1 except that the substrate temperature was 200 ° C.

In each of the above film compositions, a magnetic layer only is formed on a slide glass, and an ICP (Inductive
y coupled plasma) is a value obtained by analysis. After forming the protective layer, burnish,
Subsequently, a lubricant AM2001 (manufactured by Aojimont) was applied to a film thickness of 2 nm to obtain each sample. The membrane structure is shown in FIG.

With respect to each of the obtained samples, a VSM (vibrating sample magnetometer) was used, and static magnetism in the circumferential direction was measured at four points (center angles θ = 0, 90, 180, and 270 °) near a substrate radius of 23 mm. The characteristics (coercive force Hc) were measured and the results were compared. Magnetic layer film composition and coercive force H of each sample
Table 1 shows the average value of c and the difference between the maximum value and the minimum value.

[0024]

[Table 1]

Although Example 1 and Comparative Example 1 have the same composition, the difference between the maximum value and the minimum value of the coercive force Hc in the circumferential direction is greatly different. The sample of Example 1 used has a uniform magnetostatic property. This is apparently due to the influence of the magnetic field when forming the magnetic layer. In addition, in Examples 2 and 3, samples having uniform magnetostatic characteristics were obtained. From this result, the manufacturing method of the present invention is
It was confirmed that it is also effective in the ternary alloy magnetic layer in which the third element is added to the alloy.

In Comparative Example 2 and Comparative Example 3, good uniformity of the coercive force Hc in the circumferential direction was obtained even when the film was formed using the conventional magnetron sputtering apparatus. Considering the results of Comparative Example 1, there are materials such as Co-Sm which are strongly affected by the leakage magnetic field and materials which are not affected by the leakage magnetic field such as Co-Cr-Ta and Co-Cr-Pt. It is presumed that.

[0027]

As described above, according to the invention of claim 1, the influence of the magnetic field on the Co-Sm type alloy during the formation of the magnetic layer is in the circumferential direction of the substrate and is uniform in the circumferential direction. There is an effect that a magnetic recording medium having excellent static magnetic characteristics can be stably manufactured. According to the second aspect of the present invention, the leakage magnetic field generated in the circumferential direction of the substrate becomes uniform in any portion of the substrate due to the rotation of the magnet, so that the magnetostatic characteristics in the circumferential direction are extremely uniform. There is an effect that a recording medium can be manufactured.

According to the third aspect of the invention, there is an effect that a magnetic recording medium having uniform magnetostatic characteristics in the circumferential direction can be manufactured by a simple method. In addition, since there is little modification of the device, there is an effect that the implementation is easy.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a magnetron sputtering apparatus used in a method for manufacturing a magnetic recording medium according to an embodiment of the present invention.

FIG. 2 Cross-sectional view of cathode

FIG. 3 is a diagram showing a film structure of an example.

FIG. 4 is a schematic cross-sectional view of a conventional magnetron-type cathode and a BB arrow view.

[Explanation of symbols]

 1 Chamber 2 Substrate Holder 3 Cathode 4 Substrate 5 Target 6a to 6h Magnet

Claims (3)

[Claims] 1. A method of manufacturing a magnetic recording medium, which comprises applying a magnetic field in a circumferential direction of a substrate when forming a magnetic layer containing Co and Sm on a non-magnetic substrate. 2. A plurality of magnets having different polarities are alternately provided in the circumferential direction inside the cathode of the sputtering apparatus, and the magnets are rotated about the center of the cathode as a center of rotation, and the magnet is leaked by a leakage magnetic field. The method of manufacturing a magnetic recording medium according to claim 1, wherein a magnetic field is applied in a circumferential direction of the substrate. 3. A plurality of magnets are fixedly provided alternately with different polarities in the circumferential direction inside the cathode of the sputtering apparatus, and a magnetic field is applied in the circumferential direction of the substrate by a leakage magnetic field of the magnets. The method of manufacturing a magnetic recording medium according to claim 1, wherein