JPH0647722B2 - Method of manufacturing magnetic recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a magnetic recording medium having a ferromagnetic metal thin film formed by a sputtering method as a recording layer.

[Prior art and its problems]

In recent years, magnetic recording media such as magnetic disks used in magnetic recording devices are required to have higher density recording, and in order to meet such demand, it is necessary to thin the magnetic layer and strengthen magnetic force. The non-magnetic substrate is coated with γ-Fe ₂ O ₃ particles dispersed in a binder and baked to form a magnetic layer, instead of the coating type medium, plating or vacuum deposition on the non-magnetic substrate. Further, the development of a metal thin film type magnetic recording medium in which a thin film magnetic layer made of a ferromagnetic metal is formed by a sputtering method or the like is being actively pursued.

For coating media, the thickness of about 0.7 μm is currently the thinnest film that has been put to practical use, whereas for plating, vapor deposition, sputtering, etc., it is 1/10 of the coating thickness of 0.03 to 0.05 μm.
The following thin films can be easily realized. Moreover, the magnetic layer of the coating type medium is a layer containing a large amount of non-magnetic binder, whereas the thin layer type medium has very excellent magnetic characteristics because the magnetic layer is formed of a ferromagnetic thin film, and the magnetic layer is saturated. Since the magnetization is large and the coercive force is sufficiently large, the thin film type medium is more suitable for high-density recording because it can be adapted to such a thin film characteristically.

At present, a metal thin film type magnetic disk used as a recording medium of a fixed magnetic disk device, which has become a mainstream as a high density magnetic recording device, generally has a layer structure as schematically shown in FIG. In FIG. 3, reference numeral 31 is a disk-shaped substrate made of, for example, an aluminum alloy, and the surface thereof is covered with a nonmagnetic base layer 32 made of a Ni-P alloy.
The base layer 32 is provided to prevent mechanical deformation and damage of the thin film magnetic layer when the magnetic head comes into contact with and slides on the medium surface during recording and reproduction, and to impart sufficient smoothness to the medium surface. , Its surface is mirror-finished. A non-magnetic metal underlayer 33 made of Cr is vapor-deposited on the base layer 32.
It is formed by sputtering, ion plating, etc. The underlayer 33 is provided to improve the magnetic characteristics of the magnetic layer provided thereon. A thin film magnetic layer 34 made of a Co alloy is formed on the underlayer 33 by vapor deposition, sputtering, ion plating or the like. Finally, a protective lubricating layer 35 made of, for example, carbon is formed on the magnetic layer. This layer is provided to cover and protect the metal thin film magnetic layer which is easily corroded and worn, and to improve corrosion resistance and durability.

As a technique for forming each thin film as described above, a vacuum vapor deposition method,
The sputtering method, the ion plating method, the plating method, the spin coating method, and the like are available, but the sputtering method is drawing attention as a medium manufacturing method. This is because it is easy to obtain a thin film with a homogeneous composition, the film thickness is relatively easy to control, and the nonmagnetic metal underlayer and all subsequent layers can be continuously sputtered, making it suitable for mass production.

Conventionally, Co alloy thin film magnetic layers have been often used for magnetic tapes, but at that time, oblique deposition method was adopted. The oblique deposition method was used because the easy axis of magnetization of the Co alloy thin film fell in the plane, magnetic anisotropy appeared, and the coercive force was significantly improved. On the other hand, when the above-mentioned metal thin film magnetic disk is produced by the sputtering method, the continuously sputtered Co alloy is a Cr thin film on the Cr thin film sputtered as the nonmagnetic metal underlayer on the nonmagnetic substrate layer. Epitaxially grow on it to form a thin film magnetic layer. At this time, due to the crystal orientation of the Cr thin film of the underlayer, the easy axis of magnetization of the Co alloy thin film grown on it becomes aligned within the film plane, and the magnetic anisotropy in the horizontal direction appears largely and the sufficiently high protection is obtained. A magnetic force will be obtained.

When a magnetic disk is manufactured by the sputtering method, a sputtering apparatus whose main part is schematically shown in FIG. 1 is often used. A Cr target 13 and a Co alloy target 14 are juxtaposed in a vacuum chamber (not shown). Transport rail
While being transported by 12, a Cr underlayer and a Co alloy magnetic layer are sequentially laminated by sputtering. After that, the substrate is transported by a substrate transport rail to a target of a material for a protective lubricating layer (not shown), and the protective lubricating layer is formed by sputtering to become a medium.

The magnetic disk manufactured in this manner has a sufficient coercive force, but when actually mounted in a recording device and written and read in combination with a magnetic head, as shown in FIG. The envelope curve B of No. 2 fluctuates, and the electromagnetic conversion characteristic also fluctuates. In particular, when the coercive force is increased, the fluctuation rate (Emax-Emin) / E ₀ × 100 (%) of this envelope curve becomes large. When the cause of this was investigated, it was found that the variation of the envelope curve was due to the difference in the magnetic anisotropy strength depending on the location in the magnetic layer.

As one of the solutions to this problem, when forming the magnetic layer by sputtering, the pressure of Ar gas in the atmosphere is increased to increase the number of collisions between sputtered particles and Ar atoms, and It was effective to randomize. Specifically, when the Ar gas pressure was increased to 3.5 × 10 ^-2 Torr, a reproduction output envelope curve with almost no practical problems was obtained.

However, when the Ar gas pressure is increased to 3.5 × 10 ^-2 Torr, the film formation rate by sputtering becomes very low, and the adhesion of the underlayer to the Cr film becomes weak. Further, deterioration of magnetic characteristics also occurs.

[Object of the Invention]

The present invention has been made in view of the above points, and has a large coercive force, little change in magnetic characteristics over time, and excellent electromagnetic characteristics as seen in the uniformity of the envelope curve of the reproduction output. An object of the present invention is to provide a method for manufacturing a magnetic recording medium having conversion characteristics.

[Main points of the invention]

The present invention, in order to achieve the above-mentioned object, conveys the non-magnetic substrate along the Cr target and the Co alloy target provided side by side in the conveyance direction, and at the time of the conveyance, the Cr target and
In the method of manufacturing a magnetic recording medium, wherein a Cr underlayer and a Co alloy magnetic layer are laminated on the non-magnetic substrate by sequentially sputtering a Co alloy target, the Cr underlayer and the Co alloy magnetic layer are formed. At this time, the angle of the erosion region of the Cr target and the erosion region of the Co alloy target from the surface of the non-magnetic substrate is 40 with respect to the normal line of the non-magnetic substrate.
It is characterized by being within °.

Example of Invention

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

In practicing the present invention, a sputtering apparatus which has been conventionally used can be used, as schematically shown in FIG. As the substrate 11, a disc-shaped Al alloy substrate on the surface of which a Ni-P alloy is formed by electroless plating as a non-magnetic substrate layer and which has been mirror-polished is used. The substrate 11 is a Cr target 13 and a Co alloy target 14 of Co-30at% Ni-7.5at% Cr, which are arranged side by side in a vacuum chamber (not shown).
While being transported by the substrate transport rail 12 in the direction of arrow A at a speed of 90 mm / min, the surface of the substrate is first used as a base layer.
Cr is deposited to a thickness of 1500Å, and then Co is deposited on this underlayer.
The alloy is deposited to a film thickness of 500Å to form the magnetic layer. Board 11
Is further transported and a carbon target (not shown) is deposited to form a carbon film having a thickness of 500 Å to form a protective lubricating layer, which is used as a magnetic recording medium. All of these film formations are performed by DC magnetron system sputtering in an Ar gas atmosphere.

The target is provided with a mask 15. The shape of the mask 15 and the distance between the mask 15 and the substrate 11 determine the maximum angle θmax with respect to the normal line of the substrate into the erosion region 16 of the target on the substrate. This angle is
This is the maximum angle at which the sputtered particles enter the substrate, and the sputtered particles do not obliquely enter the substrate at an angle greater than this angle.

When the substrate on which the Cr underlayer is formed is conveyed toward the Co alloy target, sputtered particles of the Co alloy start to adhere to the substrate from the position of the angle θmax, and the formation of the magnetic layer begins. After that, as the substrate is transported, the incident angle of the sputtered particles becomes smaller and becomes vertical when the substrate comes over the Co alloy target. The incident angle increases, and the adhesion of sputtered particles to the substrate stops at the position where the maximum angle θmax is reached, and the film formation of the magnetic layer ends.

In this way, since the substrate is sputtered while moving with respect to the target, the incident angle of the sputtered particles on the substrate changes, and the crystal growth direction of the formed film changes depending on the location within the substrate. As a result, the magnetic characteristics of the magnetic layer change depending on the location. This is considered to be the reason why the envelope curve of the reproduction output of the medium fluctuates and the electromagnetic conversion characteristics fluctuate. The smaller the change in the incident angle of the sputtered particles on the substrate, the smaller the fluctuation range of the magnetic characteristics in the magnetic layer. The change in the incident angle of sputtered particles decreases as θmax decreases. Therefore, by reducing θmax, it is possible to suppress the variation rate of the envelope curve of the reproduction output.

Therefore, when the Ar gas pressure in the sputtering atmosphere when forming the magnetic layer is 5 × 10 ⁻³ Torr and 1 × 10 ⁻² Torr, θmax is 20 °, 40 °, 50 °, 60. Magnetic recording media were prepared by changing the angle to 0 °, and the fluctuation rate of the reproduction output envelope curve was examined for these media. as a result,
For both Ar gas pressures, when θmax was 20 ° and 40 °, the fluctuation rate of the envelope curve was within ± 10%, which was sufficient for practical use. For other media, the fluctuation rate of the envelope curve was between ± 15% and ± 25%, which was a practical problem.

In addition, regarding the above-mentioned medium prepared with Ar gas pressure of 1 × 10 ^-2 Torr and θmax of 40 ° and 60 °, temperature 60 ° C., relative humidity 90%
An environmental test was carried out by leaving it in the atmosphere for 2 weeks. As a result, in the electromagnetic conversion characteristics, no increase in the number of errors was observed in the medium manufactured at θmax 40 °, but an increase in the number of errors of 5 / plane was observed in the medium manufactured at θmax 60 °.

From the above results, when θmax is set within 40 °, pressure 10
^In an Ar gas atmosphere of ^-2 Torr or less, a Co alloy is sputtered to form a magnetic layer without reducing the deposition rate, and a medium that does not pose a practical problem because the fluctuation rate of the reproduction output envelope curve is sufficiently small is produced. I know what I can do.

In this embodiment, the magnetic layer material is Co-30 at% Ni-
Although 7.5 at% Cr was used, it is not limited to this composition, and the Ni content is 20 at% to 35 at% and the Cr content is 5 at% to 10 a.
An alloy having a composition ratio such that the balance is Co at t% can be preferably used, and a Co alloy having another composition may be used.

In addition, Co-30at% Ni-7.5at% C formed on the Cr underlayer
The magnetic characteristics of the magnetic layer composed of r are as shown in FIG.
Depends on the thickness of the Cr film as the underlayer. In the examples, the Cr film thickness is set to 1500 Å, but if it is 1000 Å or more, there is no practical problem.

〔The invention's effect〕

According to the present invention as described above, when the Cr underlayer and the Co alloy magnetic layer are formed by sputtering, the angles for observing the erosion region of the Cr target and the erosion region of the Co alloy target from the surface of the nonmagnetic substrate are respectively nonmagnetic substrates. By keeping the angle within 40 ° with respect to the normal line, the fluctuation range of the incident angle of the Cr and Co alloy sputtered particles on the substrate can be made small to suppress the fluctuation of the magnetic properties within the substrate and make it uniform. Therefore, it is possible to manufacture a magnetic recording medium that has a small variation rate of the reproduction output envelope curve, is uniform, has excellent electromagnetic conversion characteristics, and has a large coercive force.

Further, according to the method of the present invention, the atmosphere of the sputtering is changed.
Since it is not necessary to increase the Ar gas pressure, it is possible to form a magnetic layer that has good adhesion and little deterioration in magnetic characteristics without decreasing the deposition rate of the Co alloy film. Obtainable.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a main part of a sputtering apparatus capable of implementing the present invention, FIG. 2 is a diagram showing an envelope curve of reproduction output of a magnetic recording medium, and FIG. 3 is a schematic diagram showing an example of a layer structure of the magnetic recording medium. Fig. 4 shows the Cr film thickness of the Cr underlayer and Co-30a
FIG. 6 is a diagram showing a relationship with the magnetic characteristics of a magnetic layer of t% Ni-7.5at% Cr. 11 …… Substrate, 12 …… Substrate transport rail, 13 …… Cr target, 14 …… Co alloy target, 15 …… Mask, 16 …… Erosion area.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G11B 5/85 C 7303-5D (56) References JP-A-57-8919 (JP, A) Special features Kai 62-185245 (JP, A) JP 60-67662 (JP, A)

Claims (1)

[Claims] 1. A Cr target arranged side by side in the carrying direction,
A non-magnetic substrate is conveyed along a Co alloy target, and at the time of the conveyance, a Cr underlayer and a Co alloy magnetic layer are laminated on the non-magnetic substrate by sequentially sputtering the Cr target and the Co alloy target. In the method of manufacturing a magnetic recording medium, the angle of the erosion area of the Cr target and the erosion area of the Co alloy target from the surface of the non-magnetic substrate when forming the Cr underlayer and the Co alloy magnetic layer, A method for manufacturing a magnetic recording medium, wherein the angle is within 40 ° with respect to the normal line of the non-magnetic substrate.