JP3304382B2 - Magnetic recording medium and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk, a magnetic tape, a magnetic card and other information recording media, and more particularly to a magnetic recording medium suitable for high-density information recording and a method of manufacturing the same.

[0002]

2. Description of the Related Art A sputtering method is used as a method for forming a thin film medium for magnetic recording because of its features such as easy control of the composition of a magnetic film, good adhesion of the film to a substrate, and high mass productivity. Currently mainstream. When a magnetic recording medium is manufactured by a sputtering method, a film is formed in an atmosphere of an inert gas such as Ar of several tens mPa to several Pa, so that the back pressure is generally 1/10 ⁴ to 1/10 ⁵ before introducing the inert gas. It is considered sufficient to evacuate to Pa, and the film is actually formed under the above back pressure.

However, in the sputtering method, the gas pressure at the time of film formation must be higher than that of the electron beam evaporation method, so that high energy particles such as Ar ions and γ electrons are ejected from the inner wall of the chamber during the film formation. Impurities are easily taken into the film, and defects are easily generated in the crystal lattice. Therefore,
As described in JP-A-63-225923, a method of reducing the incorporation of impurities into a film by increasing the deposition rate of a ferromagnetic metal thin film layer to 10,000 ° / s or more has been proposed. In this method, a necessary amount of the film is grown before the impurity is taken into the film, but the amount of the impurity taken into the film is determined by the amount of the residual impurity originally existing in the sputtering chamber. Therefore, it is difficult to produce a magnetic recording medium having uniform characteristics such as crystallinity, magnetic characteristics, and recording / reproducing characteristics with good reproducibility.

[0004]

SUMMARY OF THE INVENTION The main object of the present invention is to:
Co-Cr based alloy magnetic films which are particularly susceptible to impurities among magnetic recording thin film media, and Ti or Ti
It is an object of the present invention to provide a sputtering method in which impurities incorporated in the alloy underlayer containing Cr as a main component or Cr or Cr as a main component are extremely reduced.

Another object of the present invention is to produce a magnetic recording medium by using a sputtering method in which impurities during film formation are extremely reduced, so that a magnetic material particularly effective in improving recording characteristics and an additive element added thereto. Is to provide.

[0006]

The main object of the present invention is achieved by a sputtering method in which a back pressure is reduced to a degree of vacuum of 1/10 ⁷ Pa or less when a thin film medium for magnetic recording is produced in a sputtering apparatus. be able to. Also,
Another object of the present invention can be achieved by using a perpendicular magnetic recording medium in which the magnetic layer of the magnetic recording thin film medium produced by the above-mentioned sputtering method is an alloy composed of Co and Cr.

[0007] In addition, Ta, P
It is desirable to provide a perpendicular magnetic recording medium having a magnetic layer to which at least one element selected from t, W, V, Nb, Si, B, O, and Ni is added.

Further, the magnetic layer of the magnetic recording thin film medium is a two-layer laminated film, and the lower layer is made of an alloy composed of Co and Cr and made of at least one selected from Ta, V, Nb, Si and O.
Co and Cr have higher saturation magnetization and higher coercive force in the easy axis direction than the lower layer and the magnetic layer to which the element is added.
More preferably, the perpendicular magnetic recording medium has a magnetic layer in which at least one element selected from Pt, W, B and Ni is added to an alloy comprising

Further, as a base layer of the above-described perpendicular magnetic recording medium, a Ti film or Ti is formed of Ta, Nb, Cr, Pt, Pt.
It is desirable to form an alloy film to which at least one element selected from d and V is added. When the underlayer is a Cr film or an alloy film obtained by adding Ti, Ta, Nb, Cr, and V to Cr, all of the perpendicular magnetic recording media have an in-plane magnetic recording in which the axis of easy magnetization is directed to the in-plane direction of the medium. Good characteristics can be obtained as a medium.

[0010]

When producing a thin film medium for magnetic recording with a sputtering apparatus, if the back pressure is set at 1/10 ⁷ Pa of the present invention to 1/10 ⁴ to 1/10 ⁵ Pa of the prior art, first, the sputtering chamber The impurities attached to the inner wall of the metal are greatly reduced. Thus, impurities sputtered from the inner wall of the sputtering chamber by high-energy particles during sputtering are greatly reduced. Further, the air leaking into the sputter chamber due to the pressure difference between the outside of the sputter chamber and the sputter chamber is extremely reduced, so that impurities taken into the formed magnetic recording medium are significantly reduced. According to the method for manufacturing a magnetic recording medium described above, impurities are obtained by gettering action such as Cr, which is the main component of the underlayer for the longitudinal magnetic recording medium, and Ti, which is the main component of the underlayer for the perpendicular magnetic recording medium. Elements that are easy to take in,
C used for both in-plane media and perpendicular media magnetic layers
Deterioration of crystallinity due to contamination of the o-Cr alloy can be prevented.

FIG. 1 shows the relationship between the back pressure and the back pressure when a Co-20 at% Cr perpendicular magnetization film is formed by sputtering.
The change in the c-axis orientation (Δθ ₅₀ ) of the 002 reflection of 20 at% Cr and the output half-line recording density (D ₅₀ ) are shown. According to this, it can be seen that the lower the back pressure, the higher the c-axis orientation and the higher the recording density. As in this example, a magnetic recording medium composed of a magnetic film having good crystallinity exhibited excellent recording / reproducing characteristics.

[0012]

【Example】

<Embodiment 1> FIG. 2 showing a sectional view of a magnetic recording medium of the present invention.
Example 1 will be described with reference to FIG. First, an in-line type DC magnetron sputtering apparatus was used. First, using a vacuum exhaust system in which two turbo molecular pumps were connected in series, the back pressure in the sputtering chamber was evacuated to 7/10 ⁸ Pa, and argon gas was then pumped to 0.10 Pa. After introducing up to 2 Pa, a magnetic disk is manufactured according to the following procedure. A 150 nm thick Ti-15 at% Ta underlayer 2, 2 'on both surfaces of a disc-shaped non-magnetic substrate 1 made of tempered glass and having a diameter of 95 mm and a thickness of 1.27 mm.
Was formed, a 150 nm thick magnetic layer 3, 3 'made of Co-19 at% Cr-2 at% Ta, and a 10 nm thick carbon protective layer 4, 4' were sequentially formed to produce a magnetic disk. The film formation conditions were such that the substrate temperature was kept constant at 175 ° C., and the argon gas pressure was set to the underlayers 2 and 2 ′,
0.3 Pa at the time of forming 3 ', carbon protective layer 4, 4'
During the formation, the pressure was adjusted to 1.0 Pa. All target input power densities were maintained at 100 kW / m ² .

<Comparative Example 1> Using an in-line type DC magnetron sputtering apparatus, the back pressure in the sputtering chamber was evacuated to 5/10 ⁵ Pa using a cryopump, and argon gas was introduced to 0.2 Pa. Except for filming,
Another magnetic disk was manufactured in the same procedure as in Example 1.

Embodiment 2 Embodiment 2 will be described with reference to FIG. 3 which shows a sectional view of a magnetic recording medium of the present invention. First, using an in-line type DC magnetron sputtering apparatus, a vacuum exhaust system in which turbo molecular pumps are connected in two stages in series was used to evacuate the back pressure in the sputtering chamber to 8/10 ⁹ Pa. After introducing up to 3Pa,
A magnetic disk is manufactured according to the following procedure. After forming a Ti-16 at% Nb underlayer 2, 2 'with a thickness of 125 nm on both sides of a disc-shaped non-magnetic substrate 1 made of tempered glass and having a diameter of 95 mm and a thickness of 1.27 mm, Co-19 at% Cr-2
75% thick magnetic layers 3a, 3a 'made of at% Ta,
Magnetic layers 3b and 3b 'made of Co-12.5 at% Cr-7.5 at% Pt and having a thickness of 75 mm were successively formed to form carbon protective layers 4 and 4' having a thickness of 10 nm to produce a magnetic disk. The film formation conditions were such that the substrate temperature was kept constant at 200 ° C., and the argon gas pressure was set to the underlayers 2 and 2 ′, the magnetic layers 3 a and 3 a ′,
The pressure was set to 0.3 Pa for both the layers 3b and 3b ', and to 1.0 Pa for the layers 4 and 4'. All target input power densities were maintained at 120 kW / m ² .

Comparative Example 2 After using a cryopump to evacuate the back pressure of the sputtering chamber to 6/10 ⁵ Pa using an in-line type DC magnetron sputtering apparatus, the argon gas was introduced to 0.3 Pa, and then formed. Except for filming,
Another magnetic disk was manufactured in the same procedure as in Example 2.

<Embodiment 3> Embodiment 3 will be described with reference to FIG. 2 showing a sectional view of a magnetic recording medium of the present invention. First, a back pressure in the sputtering chamber was evacuated to 6/10 ⁸ Pa using a vacuum evacuation system in which a turbo molecular pump was connected in two stages using an in-line type DC magnetron sputtering apparatus. Then, a magnetic disk is manufactured according to the following procedure. Disc-shaped non-magnetic substrate 1 made of tempered glass and having a diameter of 95 mm and a thickness of 1.27 mm
After forming a 150 nm thick Cr underlayer 2, 2 'on both sides of the film, a 150 nm thick magnetic layer 3, 3' made of Co-14 at% Cr-2 at% B, a 10 nm thick carbon protective layer 4, 4 'were sequentially formed to produce a magnetic disk. The film forming conditions are as follows: the substrate temperature is kept constant at 150 ° C .; the argon gas pressure is 0.4 Pa for forming the underlayers 2 and 2 ′ and the magnetic layers 3 and 3 ′; and the argon gas pressure is for forming the carbon protective layers 4 and 4 ′. The pressure was set to 1.0 Pa. The target input power density is
All were kept at 100 kW / m ² .

<Comparative Example 3> Using a DC magnetron sputtering apparatus of an in-line type, the back pressure in the sputtering chamber was evacuated to 4/10 ⁵ Pa by a turbo molecular pump, and then argon gas was introduced to 0.2 Pa. Another magnetic disk was manufactured in the same procedure as in Example 3 except that the film was formed.

Embodiment 4 Embodiment 4 will be described with reference to FIG. 3 which shows a sectional view of a magnetic recording medium according to the present invention. First, a back pressure in the sputtering chamber was evacuated to 6/10 ⁹ Pa using an evacuation system in which a turbo molecular pump was connected in two stages using an in-line type DC magnetron sputtering apparatus. Then, a magnetic disk is manufactured according to the following procedure. Disc-shaped non-magnetic substrate 1 made of tempered glass and having a diameter of 95 mm and a thickness of 1.27 mm
After forming Cr underlayers 2 and 2 'with a thickness of 125 nm on both surfaces of the magnetic layer 3a, 3a' and 3a 'with a thickness of 15 nm made of Co-14 at% Cr-2 at% V and Co-12.5 at% C, respectively.
15 nm thick magnetic layers 3b, 3 made of r-2at% W
b ', carbon protective layers 4 and 4' having a thickness of 10 nm were sequentially formed to produce a magnetic disk. As the film forming conditions, the substrate temperature was kept constant at 175 ° C., and the argon gas pressure was 0.3 Pa for forming the underlayers 2, 2 ′ and the magnetic layers 3 a, 3 a ′, 3 b, 3 b ′. The pressure was adjusted to 1.0 Pa during the formation of 4 '.

The target input power density is 120
kW / m ² was maintained.

Comparative Example 4 Using a DC magnetron sputtering apparatus of an in-line type, evacuating the back pressure in the sputtering chamber to 5/10 ⁶ Pa using a turbo molecular pump, and then introducing argon gas to 0.3 Pa. Another magnetic disk was manufactured in the same procedure as in Example 4 except that the film was formed from.

For the magnetic disks of Examples 1 and 2 and Comparative Examples 1 and 2, the c-axis orientation (Δθ ₅₀ ) of the 002 reflection of the magnetic layer, the output half-line recording density (D ₅₀ ), the reproduction output, and the medium Table 1 shows recording / reproducing characteristics such as S / N. Also,
Regarding the magnetic disks of Examples 3 and 4 and Comparative Examples 3 and 4,
Coercivity squareness ratio (S *) and output half-line recording density (D ₅₀ )
Table 2 shows recording / reproducing characteristics such as reproducing output and medium noise.
Here, the reproduction output, the medium noise, and the medium S / N were normalized based on the measured values of Comparative Example 1. Evaluation of recording / reproducing characteristics
Recording was performed using a thin-film magnetic head having a gap length of 0.18 μm, and reproduction was performed using an MR head with the head flying height set to 0.05 μm. The reproduction output was evaluated with a linear recording density of 2 kFCI and a track density of 15 kTPI. The medium noise was evaluated with a linear recording density of 100 kFCI and a track density of 15 kTPI.

[0022]

[Table 1]

[0023]

[Table 2]

As can be seen from Tables 1 and 2, Examples 1 and 2
2,3,4 with the D ₅₀ of the comparative example corresponding to each are greatly improved, reduced reproduction output increases the medium noise medium S / N is significantly increased.

In the first and second embodiments, the underlayers 2, 2 'are replaced by Nb, C instead of Ta added to Ti.
Similar effects were obtained when r, Pt, Pd, V, etc. were added.

In the first and third embodiments, the magnetic layers 3 and 3 'are made of T added to an alloy composed of Co and Cr.
Pt, W, V, Nb, Si, B, O, Ni instead of a
The same effect was obtained also when adding. Further, in the first and second embodiments, Ni was added between the underlayer and the magnetic layer.
-2 provided with a soft magnetic layer of Fe, Co-Ta-Zr, etc.
With a layered medium, a higher reproduction output can be obtained by combination with a perpendicular magnetic head.

In the second and fourth embodiments, the magnetic layer 3
a and 3a 'include Ta added to an alloy composed of Co and Cr.
Instead of adding V, Nb, Si, O, etc., the magnetic layer 3
For b and 3b ', the same effect was obtained when W, B, Ni or the like was added instead of Pt added to the alloy composed of Co and Cr. In Example 3 and Example 4, Cr, Ti, Ta, N was used instead of the Cr film for the underlayers 2 and 2 '.
The same effect was obtained with an alloy film to which b, Cr, and V were added.

[0028]

When the magnetic recording medium is manufactured by the sputtering method, the back pressure is reduced to 1/10 ⁷ Pa or less.
The mixing of impurities into the medium can be extremely reduced, and as a result, compared to the conventional sputtering method in which the back pressure is set to about 1/10 ⁴ Pa to 1/10 ⁵ Pa, the underlayer constituting the magnetic recording medium In addition, the crystallinity of the magnetic layer can be improved, the linear recording density and the medium S / N can be significantly improved, and these characteristics can be obtained stably with good reproducibility.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing the effect of a method for manufacturing a magnetic recording medium according to the present invention.

FIG. 2 is a partial cross-sectional perspective view of the magnetic recording medium of the present invention.

FIG. 3 is a partial cross-sectional perspective view of the magnetic recording medium of the present invention.

[Explanation of symbols]

1, 1 ': non-magnetic substrate; 2, 2': non-magnetic underlayer;
3 ': magnetic layer, 3a, 3a': first magnetic layer, 3b, 3
b ': second magnetic layer, 4, 4' ... protective layer.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Nobuyuki Inaba 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. (56) References JP-A-2-218103 (JP, A) JP-A Sho64 JP-A-3-36763 (JP, A) JP-A-3-86914 (JP, A) JP-A-3-168918 (JP, A) JP-A-63-201911 (JP, A) JP-A-5-36054 (JP, A) JP-A-5-109042 (JP, A) JP-B-61-36285 (JP, B2)

Claims (3)

(57) [Claims] Claims: 1. A back pressure is reduced to a degree of vacuum of 1/10 ⁷ Pa or less ,
Thereafter, a film is formed in a sputtering chamber into which an inert gas has been introduced.
A method of manufacturing a magnetic recording medium by a sputtering method. 2. The method according to claim 1, wherein the magnetic layer is formed by sputtering using an alloy containing Co and Cr as a material of the magnetic layer. 3. An alloy containing Co and Cr as a material of a magnetic layer is made of Ta, Pt, W, V, Nb, Si, B, O, Ni.
3. The method for manufacturing a perpendicular magnetic recording medium according to claim 2, wherein a material to which at least one element selected from the following is added is used.