JP2593590B2 - Manufacturing method of magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium such as a magnetic disk, and more particularly to a method for improving overwriting characteristics.

[0002]

2. Description of the Related Art In recent years, with the increase in recording density of magnetic recording media, a thin film (magnetic layer) of a Co alloy ferromagnetic metal having uniaxial crystal magnetic anisotropy such as CoNiCr or CoCr has been formed on a non-magnetic substrate. A metal thin film type magnetic recording medium formed by sputtering is used. In order to achieve high-density recording in the magnetic recording medium, it is necessary to have a high coercive force, and it is necessary to promote thinning of the magnetic layer.
However, when the thinning is promoted, the residual magnetic flux density Br and the film thickness δ
And the product Brδ of the product becomes small, and the reproduction output becomes small.

In order to improve the coercive force without intending to reduce the thickness of the magnetic layer, Japanese Patent Laid-Open No. 2-154322 discloses a method for improving the coercive force.
As disclosed in Japanese Patent Application Laid-Open Publication No. H10-157, there has been proposed a method for improving the coercive force of a magnetic layer by applying a negative bias voltage to a substrate during the formation of the magnetic layer. On the other hand, JP
As disclosed in Japanese Patent No. 217723, a method has been developed in which a base layer made of Cr is provided on a nonmagnetic substrate, and a Co alloy-based magnetic layer and a nonmagnetic layer are alternately stacked on the base layer by sputtering. I have. According to this method, a plurality of thin-film magnetic layers having a high coercive force are formed.
Is a large value, and high-density recording can be performed without impairing the reproduction output.

[0004]

However, in the magnetic recording medium formed by these methods, the overwriting characteristics (overwrite characteristics, O / W characteristics) are not considered, and the O / W characteristics are not considered. Had a problem.
In other words, the magnetomotive force of the magnetic head decreases as it goes downward (toward the substrate) from the surface of the magnetic recording medium (head-facing surface), but the coercive force also decreases below the single-layer magnetic layer and below the multilayer magnetic layer. Since the magnetic field is high, a new pattern (information) is hardly written to the lower or lower layer in combination with a decrease in the magnetomotive force of the magnetic head, and the S / N of the new pattern deteriorates due to noise caused by the remaining pattern. there were.

The present invention has been made in view of the above problems, and has as its object to provide a method of manufacturing a magnetic recording medium having a high recording density and a high reproduction output and having good overwrite characteristics.

[0006]

SUMMARY OF THE INVENTION In view of the above objects, a method of manufacturing a magnetic recording medium according to the present invention comprises:
A magnetic recording medium is manufactured by forming a magnetic recording layer by alternately laminating a magnetic layer made of a ferromagnetic Co alloy and a Cr layer on the underlayer by sputtering. A zero or negative bias voltage is applied to the substrate to form a magnetic layer, and the magnitude of the bias voltage when forming the lower magnetic layer is smaller than when forming the upper magnetic layer. Is a configuration of the present invention.

[0007]

When a negative bias voltage is applied to the substrate, the purity of the Co alloy forming the magnetic layer is improved, the crystal orientation of the Co alloy film is improved, and the segregation of Cr in the Co alloy film is promoted. You. For this reason, the coercive force is improved. When forming the magnetic layer adjacent to the Cr layer, the magnitude of the bias voltage at the time of forming the lower magnetic layer is set smaller than that at the time of forming the upper magnetic layer, so that the lower magnetic layer can be formed. The Co alloy purity of the layer is lower than that of the upper layer. For this reason, the holding force is also lower on the lower side than on the upper side, and even if the magnetomotive force from the magnetic head weakens, the pattern can be easily rewritten, and noise due to the remaining pattern before writing can be prevented.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will now be given of a magnetic recording medium shown in FIG. 1 as an example. In this medium, an underlayer 4 made of Cr is formed on a nonmagnetic substrate 3, and a magnetic layer made of a ferromagnetic Co alloy having uniaxial crystal magnetic anisotropy is formed thereon.
A magnetic recording layer 10 in which 5, 7, 9 and Cr layers 6, 8 are alternately stacked and the uppermost layer is a magnetic layer 9 is formed, and a protective layer 11 is further formed thereon.

FIG. 2 shows an example of a sputtering apparatus for carrying out the present invention. A target 22 for emitting atoms for forming a magnetic layer or a Cr layer is provided below a vacuum vessel 21. An annular anode 33 is attached therearound, and a negative voltage (generally -1 KV or less) is applied by a sputtering power supply 24. on the other hand,
A holder 25 for mounting the base 3 is provided on the upper part, and the base 3 mounted on the holder 25 includes:
Zero or negative voltage (usually about 0 to -200 V) is applied by the bias power supply 26 via the holder 25. Reference numeral 27 denotes an exhaust pipe connected to a vacuum pump by piping, and reference numeral 28 denotes a sputtering gas supply pipe such as an Ar gas.

[0010] As a sputtering apparatus, any apparatus can be used as long as it can apply a negative voltage to the substrate. For example, in order to improve the uniaxial orientation of the magnetic layer, a heater for heating the base may be provided in the vacuum vessel. Further, a magnetron sputtering apparatus provided with a magnet on the back surface of the target may be used. Further, the sputtering power supply and the bias power supply are not limited to DC, but may be radio frequency (RF) power.

The sputtering conditions vary depending on the sputtering apparatus used, the substrate, the target material, etc., but generally the Ar gas partial pressure is 1 to 10 × 10 ⁻³ Torr, the substrate temperature is 150 to
It is about 300 ° C. In FIG. 1, the base 3 is formed on the Al alloy substrate 1 by 10 to 20 μm to secure rigidity.
Although an amorphous Ni—P plating layer 2 having a thickness of about m is shown, the present invention is not limited to this configuration, and glass or ceramics may be used. The upper surface of the Ni-P plating layer 2 is
Usually, in order to reduce the contact resistance with the magnetic head, irregular processing called texture is performed.

The Cr underlayer 4 formed on the substrate 3 is
The c-axis (crystal axis indicating crystal magnetic anisotropy) of the ferromagnetic Co alloy (crystal structure hcp) of the magnetic layer 5 formed thereon is formed to orient in-plane. 200
It is formed by sputtering to a thickness of about 0 °. The ferromagnetic Co alloy forming the magnetic layers 5, 7, 9 of the magnetic recording layer 10 may be any ferromagnetic Co alloy having an hcp crystal structure, such as CoNiCr, CoCrTa, C
oCrPt and the like. Since the coercive force of the magnetic layers 5, 7, 9 decreases from the surface side to the underlayer side, the magnitude of the bias voltage is sequentially increased as the layers are formed from the lower side to the upper side. The bias voltage at the time of forming the lowermost layer 5 may be zero. The total thickness of each magnetic layer 5, 7, 9 is 600 to
It should be 800 mm. The reason why the total layer thickness is set to 600 to 800 ° is that a magnetic recording medium having a Brδ of 450 to 600 G · μ is required as a magnetic recording medium in order to secure reproduction output and reduce noise. The thickness of each magnetic layer is preferably set to 100 ° or more. If the angle is less than 100 °, not a continuous film but an alloy portion is scattered in an island shape, superparamagnetism appears, and the coercive force decreases rapidly. In the example shown in FIG.
7 and 9 have three layers, but the number of layers can be freely set.

The Cr layers 6, 8 formed between the magnetic layers 5, 7, 9
Is provided for in-plane orientation of the c-axis of the Co-based alloy of the magnetic layer and for weakening magnetic interaction between the magnetic layers, and the layer thickness may be about 50 to 250 °. If less than 50 mm, Cr
Since the magnetic interaction between the magnetic layers sandwiching the layers is too strong, it is difficult to reduce the medium noise due to the multilayering. On the other hand, if the angle exceeds 250 °, the medium noise increases and the electrical characteristics deteriorate. It is needless to say that a negative bias voltage may be applied when forming the Cr layer and the Cr underlayer.

On the magnetic recording layer 10, a non-magnetic protective layer 11 made of carbon or the like is formed by sputtering at about 200 to 400 °, and a lubricant such as fluorinated polyether is further coated with a lubricant at about 20 to 50 °. It may be applied. The protective layer 11 and the lubricating coating layer may be formed as needed. In addition, as an industrial film forming method of the Cr underlayer, the magnetic layer, the Cr layer, and the non-magnetic protective layer, a sputtering apparatus provided with a target material for forming an intended layer is provided in parallel, and the substrate is sputtered. What is necessary is just to move to an apparatus sequentially and to form a laminated film.

Next, specific embodiments will be described. (1) A Ni-P plating layer was formed on an Al substrate, and a Cr underlayer 4 was formed on the Ni-P plating layer at a thickness of 1000 の 上 as shown in FIG. 1 using a substrate having a textured surface.
On top of this, a 250 mm thick magnetic layer 5,7,9 is added to a 100 mm Cr layer.
Three layers were stacked via 6,8. Table 1 shows the magnitude of the bias voltage applied to the substrate when the magnetic layers 5, 7, and 9 were formed. After the upper magnetic layer 9 was formed, a carbon layer was further formed thereon to a thickness of 300 mm.

As a film forming apparatus, an RF magnetron sputtering apparatus was used, the RF power was set to 500 W, and the film forming conditions were an Ar gas pressure of 5 mmTorr and a substrate temperature of 230 ° C. The Co alloy composition (composition of the magnetic layer) used as the target was Co ₈₄
Cr ₁₄ Ta ₂ . FIG. 3 shows the relationship between the bias voltage applied to the base and the coercive force of the magnetic layer. It can be seen from the figure that the smaller the bias voltage is, the smaller the coercive force is.

[0017]

[Table 1]

(2) The coercive force, medium noise (SNm) and overwrite characteristics of the magnetic recording medium after film formation were examined.
Table 2 shows the results. The overwrite characteristics are as follows: 1F data is written on the medium,
After overwriting the 2F data, the frequency components of 1F and 2F were measured with a spectrum analyzer and evaluated by the value (O / W value) defined by the following equation. The smaller the O / W value (the larger the absolute value), the clearer the pattern before writing is. The measurement conditions were as follows: a thin film head was used as the magnetic head, and the flying height was 0.13 μm, 1F data: 1.75 MHz, and 2F data: 5.0 MHz.

[0019]

(Equation 1)

[0020]

[Table 2]

(3) As shown in Table 2, the O / W value of the example is significantly lower than that of the comparative example, even though the coercive force is equal to or higher than that of the comparative example. Is recognized. Although no remarkable improvement was observed in the medium noise, good results equivalent to or better than the comparative example were obtained.

[0022]

As described above, in the method of manufacturing a magnetic recording medium according to the present invention, a plurality of magnetic layers are stacked and formed with a Cr layer interposed therebetween, so that recording density and reproduction output can be improved. Moreover, the lower the magnetic layer, the smaller the negative bias voltage applied to the substrate during film formation, so that the coercive force of the lower magnetic layer can be reduced, and the magnetomotive force from the magnetic head can be reduced. Even if the number of magnetic layers decreases, a new pattern can be easily written in the lower magnetic layer, and the overwrite characteristics can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a magnetic recording medium according to an embodiment.

FIG. 2 is a configuration explanatory view showing an example of a sputtering apparatus for carrying out the present invention.

FIG. 3 is a graph showing a relationship between a bias voltage applied to a base and a coercive force.

[Explanation of symbols]

 3 Base 4 Underlayer 5 Magnetic layer 6 Cr layer 7 Magnetic layer 8 Cr layer 9 Magnetic layer 10 Magnetic recording layer 22 Target 24 Bias power supply 26 Power supply for sputtering

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoshiki Takemura 5-10-10 Okuhata, Itami-shi, Hyogo Pref. Japan, Kubota Amagasaki Plant Itami-Bran Plant (56) References JP-A-2-161617 (JP, A) Kaihei 1-217723 (JP, A)

Claims (1)

(57) [Claims] An underlayer made of Cr is formed on a nonmagnetic substrate, and a ferromagnetic layer is formed on the underlayer by sputtering.
In a method for manufacturing a magnetic recording medium in which a magnetic recording layer is formed by alternately laminating a magnetic layer made of an o-alloy and a Cr layer, a magnetic layer is formed by applying a zero or negative bias voltage to a substrate. A method of manufacturing the magnetic recording medium, wherein the magnitude of the bias voltage at the time of forming the lower magnetic layer is smaller than that at the time of forming the upper magnetic layer.