JPH05101385A - Production of magnetic recording medium having axis of easy magnetization unified in circumferential direction - Google Patents

Abstract

PURPOSE:To produce the magnetic recording medium having the axis of easy magnetization unified in a circumferential direction with good productivity. CONSTITUTION:The process for production of the magnetic recording medium having substrate film layers 28, 29 consisting of a Cr system on a nonmagnetic base body 27 and a magnetic alloy film 30 of a Co system thereon and having the axis of easy magnetization unified in the circumferential direction consists in making medium particles incident on the base body 27 by a sputtering method from the substantially radial direction of the magnetic recording medium to be formed with the substrate film layers 28, 29 to form the initial layer 28 of the extremely thin film consisting of the Cr system at the time of forming the above-mentioned substrate film layers 28, 29, then laminating and forming the Cr film 29 by the sputtering method which does not restrict the incident direction of the medium particles until the thickness sufficient as the substrate film layer is attained. The magnetic recording medium is produced with more excellent productivity than the conventional process for production.

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 having easy axes of magnetization aligned in the circumferential direction, for example, a disk-shaped magnetic recording medium used for hard disks, floppy disks and the like.

[0002]

2. Description of the Related Art As a magnetic recording medium of this type, there is one using a Co-based alloy thin film as a magnetic recording layer.
In order to have a strong anisotropy in the film surface of the medium, a Cr thin film having a body-centered cubic structure or the like is provided as an underlayer between the substrate and the magnetic recording layer, so that the coercive force and the corner of the magnetic recording layer are increased. It is known that the mold ratio can be increased. For example, when a recording layer made of Co—Cr having a hexagonal close-packed structure is provided on a Cr underlayer, the magnetization easy axis of the Co—Cr layer is c.
A magnetic recording medium having a remarkably good squareness and a large coercive force can be produced as compared with the case where the axis is oriented in the plane of the film and there is no Cr underlayer.

However, a medium that is generally manufactured may have an easy axis in a certain direction in the plane by the manufacturing apparatus, or may have distributed easy axes in different directions depending on the position. Therefore, for example, a hard disk, a floppy disk, or the like, which is a disk-shaped magnetic recording medium, may be along the easy magnetization axis direction or the hard magnetization axis direction during one round when viewed from the concentric track traveling direction. Appears in sequence, which causes output fluctuation during reproduction.
The remanent magnetization M _r (easy) in the easy-axis direction is larger than the remanent magnetization M _r (hard) in the hard-axis direction. For example, when the easy-axis is aligned in one direction on the disk, the track goes around one track. The envelope of the reproduced output is similar to a two-period sine wave. In order to suppress such an output fluctuation in a disk-shaped magnetic recording medium, it is necessary to align the easy axis of magnetization in the circumferential direction or to prepare an isotropic medium.

[0004]

In order to align the easy axis of magnetization in the circumferential direction, a method of controlling the easy axis of magnetization has been attempted by texturing the disk-shaped substrate in a concentric manner in the circumferential direction. ing. According to this method, the radial direction becomes the hard axis of magnetization and the circumferential direction becomes the easy axis of magnetization due to the shape magnetic anisotropy, and the residual magnetization in the easy axis of magnetization becomes approximately 30% larger than that in the hard axis of magnetization. Playback output fluctuations are suppressed and the playback output itself becomes large on average (eg, S. Uchinami et al., IEEE Trans. Mag.
n., vol.23, No.5, Sept (1987) 3408).

However, the method by texture processing is
This will increase the surface roughness of the substrate. This is not suitable for high-density recording in which the distance between the medium surface and the head is locally varied due to surface roughness, and the precision of the distance between the head and the medium is a particular problem. It is also possible to manufacture an isotropic recording medium within the film surface depending on the medium manufacturing conditions, but the squareness is averaged and deteriorated compared to a medium in which the easy axis of magnetization is aligned in the circumferential direction. Therefore, the residual magnetization also becomes small and the reproduction output becomes small.

[0006] On the other hand, a method is known in which the axis of easy magnetization is aligned in the circumferential direction by making medium particles enter the Cr underlayer in the radial direction of the disk-shaped substrate without texturing. This method utilizes the so-called oblique incidence effect. The oblique incidence effect means that when a thin film is formed by sputtering or vapor deposition, the medium particles are generally incident on the substrate in a direction perpendicular to the substrate surface. Unlike that, the anisotropy is affected by the incident direction.

In particular, as shown in FIG. 5 of the accompanying drawings, the Cr-based underlayer 2 and the Co-based alloy recording layer 1 are actually used as the base 3
When the medium particles are made to enter at a certain angle θ, that is, in the direction of arrow 4 when the recording medium is made to adhere onto the recording medium, the recording medium to be produced is in a direction perpendicular to the incident direction (α = ±).
The easy magnetization axis is aligned at 90 ° (the direction of arrow 5 in FIG. 5). Here, the arrow 4 is in the x-z plane and the arrow 5 is in the xy plane. That is, in order to align the easy axis of magnetization in the circumferential direction, the medium particles should be obliquely incident in the radial direction.

As an example of such a method, a method called a planar magnetron method as schematically shown in FIG. 6 is conventionally known. According to this method, when the disk-shaped magnetron 10 is used during sputtering, the magnetron target is most likely to be sputtered in a region in which the magnetic field parallel to the target surface is the strongest. This area is called an erosion area. Since the magnetic flux from the disk-shaped target goes toward the periphery from the center of the target along the radial direction,
The erosion area 11 has a circular shape. Therefore, the anisotropy can be aligned in the circumferential direction by controlling the incident angle of the medium particles 14 with respect to the substrate 13 using the mask 12 having a hole in the center between the substrate 13 and the target 10 ( T. Abe et al. IEEETrans. Magn., Vol.22,
No. 5, Sept. (570) 1986).

As described above, C produced by limiting the incident angle
When an r-type underlayer is provided, and a Co-type ferromagnetic layer formed by a usual method (hereinafter, referred to as a batch type method) on which a mask is removed is formed, a medium having a two-layer structure is produced.
Also in the upper Co-based ferromagnetic layer, the easy axis of magnetization is aligned in the circumferential direction due to the influence of this underlayer.

However, the Cr-based underlayer has a certain degree (5
If the thickness of the recording layer is not more than 0 nm), good characteristics of the recording layer cannot be obtained. However, when the Cr-based underlayer is prepared by the above-mentioned conventional method, the deposition rate of the film is remarkably reduced because of the mask. There has been a drawback that productivity is deteriorated because it takes too much time to form a sufficiently thick underlayer. Further, in this conventional method, the target is limited to the disk-shaped planar magnetron type having a size commensurate with the substrate. So, for example,
In the in-line sputtering apparatus with the highest production efficiency, this method cannot be applied because each layer is formed while the substrate passes over the rectangular target.

An object of the present invention is to provide a method of manufacturing a magnetic recording medium which can solve the above-mentioned conventional problems.

[0012]

According to the present invention, a Cr-based underlayer film is provided on a non-magnetic substrate, and a Co-based ferromagnetic alloy film is provided thereon, and they are aligned in the circumferential direction. In the method of manufacturing a magnetic recording medium having an easy axis of magnetization, when forming the underlayer, medium particles are incident on the substrate by a sputtering method from a substantially radial direction of the magnetic recording medium to be formed. Thus, after forming an extremely thin Cr-based initial layer, by further forming a Cr-based film as a base film layer to a sufficient thickness by a sputtering method that does not limit the incidence direction of medium particles, the easy axis of magnetization is A base film layer having a sufficient thickness that is aligned in the circumferential direction can be formed with good productivity.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, based on FIGS. 1 to 4 of the accompanying drawings,
The present invention will be described in more detail with reference to examples of the present invention.

Before describing specific examples of the present invention, first, the points of interest by which the inventor can make the present invention will be described. It is generally known that, in crystal growth in a thin film, the crystal orientation is aligned in the same direction as the initial crystal. Actually, this phenomenon is also utilized in the magnetic recording medium in which the Co-based magnetic layer is provided on the conventional Cr-based underlayer, and the Cr-based thin film itself has no magnetism. It is provided to control the crystal direction of the Co-based magnetic layer formed in 1. That is, the Co-based magnetic layer grows under the influence of the crystal structure of the Cr-based underlayer, and if the crystal direction of the Cr-based underlayer is the circumferential direction, the Co-based magnetic layer formed on the Co-based magnetic layer also has the crystal structure. The growth is influenced by the structure, and the direction of the easy axis of magnetization can be set to the circumferential direction.

The inventors of the present invention thought that such a phenomenon could be applied to the formation of the Cr-based underlayer, and even in the formation of the Cr-based underlayer, the medium particles were obliquely incident only at the initial stage to direct the crystallographically. After that, various experiments were carried out with the idea that after that, even if the incident direction of the medium particles is not limited, the stacking can be performed according to the crystal direction of the initial layer. As a result, C formed in this way
Even if a Co-based recording layer, which is a ferromagnetic metal thin film, is provided on the r-based underlayer, the Co-based recording has anisotropy in which the easy axis of magnetization is aligned in the direction perpendicular to the incident direction of the Cr-based initial layer. The inventors arrived at the present invention by confirming that layers could be realized.

In the present invention, a Cr-based ultrathin film initial layer is provided as a control layer by oblique incidence with a limited incident angle, and a Cr-based underlayer and Co are formed on the initial layer by a normal film formation method that does not limit the incident angle. The anisotropy of the recording layer is controlled by preparing the recording layer of the system. FIG. 1 conceptually shows the cross-sectional structure of a magnetic recording medium formed by the manufacturing method of the present invention. As shown in FIG. 1, this magnetic recording medium was produced by obliquely incident on a non-magnetic substrate 27 C
After the initial layer 28 of an r-type ultra-thin film is formed, a Cr-type underlayer 29 and a Co-type recording layer 30 which are produced by a method that does not normally limit the incident angle are laminated.

Actually, as the initial layer 28, the average incident angle θ = 30 from the Cr target by the sputtering method.
The ultrathin Cr film is made incident to the glass substrate 27 at a temperature of 10 nm to form a film having a thickness of 10 nm, and the ordinary incident angle is not limited, that is, the Cr underlayer 29 is made to have a thickness of 50 nm at an average incident angle θ = 90 °. Further, the Co recording layer 30 is set to 50
A magnetic recording medium was produced by sputtering to a thickness of nm. At this time, the sputtering gas pressure was 1.5 mTorr and the temperature of the substrate was kept at 200 ° C.

FIG. 4 shows the results of evaluation of the magnetic recording medium thus obtained by a vibrating sample type magnetometer (VSM). The curve of FIG. 4 shows the ratio (M _r / M _r (0)) of the remanent magnetization of the incident direction (α = 0 °) to the remanent magnetization obtained by measuring in the direction of an angle α in the film plane. It is plotted with respect to α. As can be seen from the curve in FIG. 4, the remanent magnetization ratio is about 1.4 at the maximum around α = 90 °, and it is clear that the anisotropy is clear. In other words, if an initial layer of a Cr ultra-thin film is provided by oblique incidence with a limited incident angle, and a Cr underlayer and a Co—Cr system recording layer that are thick to some extent are provided by a method that does not normally limit the incident angle, the recording layers will differ. It can be seen that the directionality can be controlled. As a result, it can be seen that the productivity is much improved as compared with the conventional method in which the incident angle is limited and the relatively thick Cr-based underlayer is entirely manufactured.

Here, the Co-based ferromagnetic metal thin film 30 is C
In addition to o and Co, Ni, Cr, Ta, V, B, C,
W, Pt, Fe, Al, etc. added, for example, C
o-Cr, Co-Cr-Ni, Co-Cr-Ta, Co
-Pt, Co-Cr-Pt, Co-Cr-Pt-B and the like. The Cr-based underlayer and the initial layer are made of Cr, W
Alternatively, it is an alloy containing Cr and W as main components.

Specific examples of the manufacturing method of the present invention will be described below. In the following description, “an initial layer of a Cr-based ultrathin film formed by oblique incidence with a limited incident angle” is referred to as an A layer, and “C formed without limiting the incident angle”.
The "r-based underlayer" is referred to as the B layer, and the "Co-based recording layer formed without limiting the incident angle" is referred to as the C layer.

Example-1 FIG. 2 is a schematic view for explaining one example of the manufacturing method of the present invention. In this embodiment, an in-line type sputtering apparatus having high productivity is used. According to the manufacturing method of this embodiment, the substrate 40 of the magnetic recording medium is sputtered on the rectangular target 44 while moving in the direction of arrow 50. First, the A layer is formed via the mask 41 provided close to the substrate 40. The mask 41 is provided with slits 42 in the incident direction of the medium particles. At this time, the base body 40 does not move in the direction of the arrow 50 but rotates on its axis. Sputtering medium particles from the sputtering target 44, arrows 52, 53 from the erosion region 51.
Are scattered in the direction of and are incident on the substrate 40 through the slit 42. Since the base body 40 is rotating,
The light is obliquely incident on the entire substrate in the radial direction.

The substrate on which the A layer is formed in this way is indicated by the arrow 5
It is moved in the direction of 0 and held at the position indicated by reference numeral 43. In this state, the B layer and the C layer are sequentially formed by the sputtering method in which the incident angle by the sputtering target 44 is not limited. In this case, the substrate may be rotating or stationary. As a result, the easy axis of magnetization of the recording layer is aligned in the circumferential direction. Reference numerals 54 and 55 indicate directions in which each medium particle is scattered from the erosion region 51 of the sputtering target 44.

The length of the slit 42 is about the radius of the substrate 40, but may be about the diameter. Further, the slit 42 may have a fan shape extending from the center of the base body. Here, the A layer is formed on only one side of the substrate 40, but if a mask and a target are provided at vertically symmetrical positions with respect to the substrate 40, the double-sided initial layer can be simultaneously formed. Further, here, the substrate 40 and the mask 41 are
Although the case where the substrate 40 is relatively stationary except the rotation is shown, the slit 42 may be appropriately lengthened, the mask 40 may be stationary, and only the substrate 40 may be rotated and moved in the direction of the arrow 50. .. If you use the above mask,
It is understood that the easy axis of magnetization can be aligned in the circumferential direction of the disk-shaped substrate even in a highly productive apparatus such as in-line sputtering. Further, a conventional sputtering method in which the entire surface of the target is averagely sputtered without using a magnetron is also possible.

Embodiment-2 FIG. 3 is a schematic view for explaining another embodiment of the manufacturing method of the present invention. This example uses an improved facing target scheme to form the A layer. As shown in FIG. 3, in this embodiment, two pairs of opposed sputtering targets 70 and 71 having a relatively small area with respect to the area of the substrate are arranged with respect to the substrate 72 having a hole at the center. Form the layers.

The target pair 70 has a cylindrical shape, and the target pair 71 has a donut shape. Further, donut-shaped magnets 80, 81, 82, 83, 84, 85 are arranged as shown. With such a structure, the layer A is obliquely incident on the substrate 72 along the radial direction as indicated by arrows 75, 76, and 77 regardless of the rotation of the substrate. Among the pair of targets facing each other, the target pair 71 is not effective in that it has the same anisotropy as the target pair 70, and may be omitted because it is an auxiliary one. The target area for forming the A layer is much smaller than that of a normal target, and the cost is low. Further, since the targets face each other and a mask is not used, the amount of sputtered particles wasted is small, which is a very efficient method as compared with the conventional method.
The remaining B layer and C layer may be formed by an inline or batch type method which is a normal sputtering method.
As a result, the axes of easy magnetization are aligned in the circumferential direction.

[0026]

According to the manufacturing method of the present invention, in order to align the easy axis of magnetization of the magnetic recording layer in the circumferential direction, only the ultrathin Cr-based initial layer is sputtered with the incident angle limited. The magnetic recording medium can be manufactured with much higher productivity than the conventional method, because the target can be formed by the method described above and the shape of the target does not have to be taken into consideration.

[Brief description of drawings]

FIG. 1 is a view conceptually showing a cross-sectional structure of a magnetic recording medium formed by a manufacturing method of the present invention.

FIG. 2 is a diagram for explaining one embodiment of the manufacturing method of the present invention, in which the cross-sectional structure and the one seen from above the substrate when forming the initial layer of the Cr-based ultrathin film by oblique incidence are schematically shown. It is the figure shown.

FIG. 3 is a diagram for explaining another embodiment of the manufacturing method of the present invention, which is a cross-sectional structure when a Cr-based ultrathin initial layer is formed by oblique incidence and a view seen from above the substrate in a simplified manner. It is the figure shown.

FIG. 4 is a diagram showing a graph for explaining the effect of the oblique incidence on the recording layer of the Cr-based ultrathin film initial layer.

FIG. 5 is a diagram for explaining an oblique incidence effect.

FIG. 6 is a diagram for explaining an example of a conventional method for circumferentially applying an easy axis of magnetization.

[Explanation of symbols]

1 Co-based magnetic recording layer 2 Cr-based underlayer 3 Substrate 10 Disc-shaped magnetron target 11 Erosion region 12 Disc-shaped mask for incident angle control 13 Disc-shaped substrate 27 Substrate 28 Cr-based ultra-thin film initial layer by oblique incidence 29 Incident angle limited Cr-based underlayer 30 formed without forming a Co-based magnetic recording layer formed without limiting the incident angle 40 Disc-shaped substrate 41 Mask 42 Slit 44 Rectangular magnetron target 70 Opposed cylindrical sputtering target 71 Opposed donut-shaped sputtering target 72 Disk-shaped substrate 81, 82, 83, 84, 85 Donut magnet for facing target

Claims (3)

[Claims] 1. A magnetic recording medium having a Cr-based underlayer on a non-magnetic substrate, a Co-based ferromagnetic alloy layer on the underlayer, and an easy axis of magnetization aligned in the circumferential direction. In the method, when forming the base film layer, on the substrate,
After forming a Cr-based initial layer of a very thin film by injecting medium particles by a sputtering method from substantially the radial direction of the magnetic recording medium to be formed, a Cr-based initial layer is further formed by a sputtering method that does not limit the incident direction of the medium particles. A method of manufacturing a magnetic recording medium, comprising laminating films as a base film layer to a sufficient thickness. 2. The Cr-based initial layer is formed by arranging a mask having slits extending in the radial direction of a magnetic recording medium to be formed above the upper surface of the base and rotating the base while rotating the base. The method of manufacturing a magnetic recording medium according to claim 1, wherein the method is performed by performing sputtering through a slit of a mask. 3. The formation of the Cr-based initial layer is performed in the same manner as the small circular sputter target arranged substantially on the central surface of the base body and the outer surface of the base body facing each other. The method for producing a magnetic recording medium according to claim 1, wherein the method is performed by using a doughnut-type sputter target having an inner diameter of about 3 mm.