JP2864957B2 - Method for manufacturing magneto-optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a magneto-optical disk, and more particularly to a method for manufacturing a magneto-optical recording medium having excellent recording magnetic field sensitivity.

[0002]

2. Description of the Related Art In a magnetic field modulation overwrite method,
Improving the recording magnetic field sensitivity of the magneto-optical recording medium is important for increasing the recording density and reducing the magnetic field required for recording / erasing to reduce the load on the drive. In order to improve the recording sensitivity, a capping layer may be added to the TbFeCo film (Y. Yamada, M. Yoshihira).
o, N. Ohta, H .; Sukeda, T .; Nihar
a and H.A. Fujiwara; Magn. S
oc. Jpn. , 15, Suppl. Sl, 417 (1
991)), a GdFeCo film having a thickness of 10 nm and a thickness of 20
-layered magneto-optical recording medium with a two-layer exchange-coupled two-layer TbFeCo film (Katsumi Ichitani, Shigeru Tsunashima, Susumu Uchiyama; 15th Annual Meeting of the Japan Society of Applied Magnetics, 31p
B-2, p. 307). In these two magneto-optical recording media, a magnetic layer is newly added to a conventionally known magneto-optical recording medium to improve the recording magnetic field sensitivity by adopting a five-layer medium configuration. It is more complicated than the medium.

[0003] The use of pure Kr as a sputtering gas when producing a Co / Pt or Co / Pd multilayer film by a sputtering method is described in a literature (PF Carcia, SI).
Shah and W.S. B. Zeper; Appl. P
hys. Lett. 56, 2345 (1990)) and JP-A-5-6589. A Co / Pt or Co / Pd multilayer film produced by a sputtering method using pure Ar gas has a coercive force of only several hundreds Oe at most, which is much smaller than the coercive force of a rare earth-transient metal amorphous film. And the perpendicular magnetic anisotropy energy is less than one tenth of the rare earth-transition metal amorphous film,
In addition, since the square ratio of the Kerr loop is as far as 1, it is not suitable as a recording film of a magneto-optical recording medium. Therefore, it was necessary to increase the coercive force and the perpendicular magnetic anisotropy energy and to make the squareness ratio close to 1. To solve this problem, a sputtering method using Kr gas or Xe gas is used. In a magneto-optical recording medium, a method of producing a recording film containing a rare earth-transition metal alloy by a sputtering method using a gas containing Kr or Xe is disclosed in JP-A-4-298835 and JP-A-4-366441. It is shown.

In Japanese Patent Application Laid-Open No. Hei 4-298835, the coercive force is small because the magnetic film contains a light rare earth element.
Therefore, in order to increase the holding power and to improve the reproduction signal characteristics, it is manufactured by a sputtering method using a gas containing Kr or Xe.

[0005] Further, there is no description about a target such as whether an alloy target or a composite target is used when producing a recording film. JP-A-4-36644
In Japanese Patent Publication No. 1 (1993), a mixed gas always containing Ar is used as a sputtering gas, and Pt, P
It contains at least one element selected from d and Au. Generally, when a nonmagnetic element is added to an amorphous film of Tb or Dy and a transition metal, the squareness ratio of the Kerr loop deteriorates. Conversely, if no non-magnetic element is added,
There is no need to worry about squareness. Also, Japanese Patent Application Laid-Open No. Hei 4-366
In Japanese Patent No. 441, indicating that a square loop exhibiting good Kerr hysteresis indicates a Kerr rotation angle (θ _{K 1} ) at the maximum external magnetic field and a residual Kerr rotation angle (θ _{K 2} ) which is a Kerr rotation angle at zero external magnetic field. Has a non-θ _{K 2} / θ _{K 1} of 0.
Although it is specified to mean 9 or more, as far as the examples and comparative examples are concerned, both θ _{K 2} / θ _{K 1} are 0.9 or more, and no improvement in the Kerr loop squareness ratio was confirmed. This effect is hardly remarkable.

[0006]

The five-layer magneto-optical recording medium has a problem that the medium structure is complicated in order to improve the recording magnetic field sensitivity.

The production of a Co / Pt or Co / Pd multilayer film using pure Kr gas or pure Xe gas is as follows.
This is disclosed in Japanese Patent Application Laid-Open No. Hei 5-6589. In this,
Although it has been shown that the coercive force is increased, the squareness ratio is set to near 1, and the recording noise level is lowered, it is not possible to obtain knowledge on the recording magnetic field sensitivity.

Japanese Patent Application Laid-Open No. 4-298835 describes a recording laser power sensitivity.
There is no description about the recording magnetic field sensitivity or any description for obtaining knowledge regarding the recording magnetic field sensitivity.

Japanese Patent Application Laid-Open No. 4-366441 also discloses a car loop as a magnetostatic characteristic, but does not describe an actual read / write characteristic, particularly a recording magnetic field sensitivity.

An object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a method for manufacturing a magneto-optical recording medium having excellent recording magnetic field sensitivity without complicating the medium structure.

[0011]

[Means for solving the problem] Pure K as a sputtering gas
r, a target composed mainly of a Tb or Dy element and a target composed mainly of a transition metal element, and two targets are simultaneously sputtered to produce a metal composed mainly of Tb or Dy and a transition metal element. An amorphous film is formed by alternately stacking metals as components.

[0012]

The Tb or Dy target and the FeCo target are simultaneously sputtered using Kr, an element heavier than Ar, so that sputtered atoms (Tb, Dy,
The energy distribution of Fe, Co) shifts to the higher energy side. As a result, the short-range order of the amorphous film changes, and the anisotropic dispersion of the magnetic film changes, thereby improving the recording magnetic field sensitivity. This phenomenon is newly discovered experimentally.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

(Embodiment 1) The magneto-optical recording medium according to Embodiment 1 is such that a SiN film, a Tb / FeCo periodic multilayer film is 200 Å, a SiN film is 400 Å, and an Al reflective film are sequentially formed on a polycarbonate substrate. Was formed into a film of 400 Å. Tb / Fe at this time
The Tb layer thickness in the Co periodic multilayer film is 4 Å, and the FeCo layer thickness is 6 Å. S
The iN film was formed by a reactive RF magnetron sputtering method using a mixed gas of Ar and N2 at a degree of vacuum of 2.0 × 10 -1 Pa during sputtering. The Al reflection film was formed by an RF sputtering method using Ar gas. In the first embodiment, the Tb / FeCo periodic multilayer film is composed of a Tb target and Fe90.
The substrate rotation speed was fixed at 20 rpm using a Co10 target, and the degree of vacuum during sputtering was 8.0 using pure Kr gas.
At 10 × 10-2 Pa, two targets are simultaneously D
It was produced by sputtering with a C magnetron sputtering method.

Comparative Example 1 Further, a magneto-optical recording medium as Comparative Example 1 was manufactured.
In the magneto-optical recording medium of Comparative Example 1, a SiN film, a Tb / FeCo periodic multilayer film were 200 Å, a SiN film was 400 Å, and an Al reflective film was 400 Å on a polycarbonate substrate. Tb / Fe at this time
The Tb layer thickness in the Co periodic multilayer film is 4 Å, and the FeCo layer thickness is 6 Å. S
The iN film was formed by a reactive RF magnetron sputtering method using a mixed gas of Ar and N2 at a degree of vacuum of 2.0 × 10 -1 Pa during sputtering. The Al reflection film was formed by an RF sputtering method using Ar gas. In the first embodiment, the Tb / FeCo periodic multilayer film is composed of a Tb target and Fe90.
The substrate rotation speed was fixed at 20 rpm using a Co10 target, and the degree of vacuum during sputtering was 8.0 using pure Ar gas.
At 10 × 10-2 Pa, two targets are simultaneously D
It was produced by sputtering with a C magnetron sputtering method.
That is, except for using Ar instead of Kr when forming the Tb / FeCo periodic multilayer film, the film thickness of each layer and the manufacturing conditions are exactly the same as those of the magneto-optical recording medium of the first embodiment.

FIG. 1 shows a carrier level 1 and a noise level 2 of the magneto-optical recording medium of Example 1 manufactured by the method according to the present invention, and a carrier level 3 of the magneto-optical recording medium of Comparative Example 1.
4 shows the recording magnetic field dependence of the noise level 4. The recording and reproduction conditions were a linear velocity of 11 m / s, a recording frequency of 3.
7 MHz, and the reproduction laser power was 1.0 mW. In the magneto-optical recording medium of Comparative Example 1, the noise level 4 does not saturate unless a magnetic field of 350 (Oe) or more is applied. However, in the magneto-optical recording medium of Example 1 manufactured by the manufacturing method according to the present invention, the noise level 2 is saturated when a magnetic field of 250 (Oe) or more is applied. That is, according to the production method of the present invention,
The recording magnetic field sensitivity of the magneto-optical recording medium is improved.

(Embodiment 2) The magneto-optical recording medium of Embodiment 2 was manufactured in the same manner as the magneto-optical recording medium of Embodiment 1 described above. The difference from the first embodiment lies in the Tb layer thickness and the FeCo layer thickness in the Tb / FeCo periodic multilayer film. The Tb layer thickness in the Tb / FeCo periodic multilayer film of Example 2 was 6.
4 Å and the FeCo layer thickness is 9.6 Å.

Comparative Example 2 Further, as Comparative Example 2, a magneto-optical recording medium was manufactured. The magneto-optical recording medium of Comparative Example 1 was produced in the same manner as described above. The difference from Comparative Example 1 is that Tb
/ The thickness of the Tb layer and the thickness of the FeCo layer in the FeCo periodic multilayer film. The Tb layer thickness of the Tb / FeCo periodic multilayer film of Comparative Example 2 was 6.4 angstroms, and the FeCo layer thickness was 9.6 angstroms. That is, Tb /
Except for using Ar instead of Kr when forming the FeCo periodic multilayer film, the thickness of each layer and the manufacturing conditions are exactly the same as those of the magneto-optical recording medium of Example 2 according to the present invention.

FIG. 2 shows a recording magnetic field of the carrier level 5 and the noise level 6 of the magneto-optical recording medium of Example 2 manufactured by the method according to the present invention, and the carrier level 7 and the noise level 8 of the magneto-optical recording medium of Comparative Example 2. It shows the dependency.
The recording and reproducing conditions are the same as in the first embodiment. In the magneto-optical recording medium of Comparative Example 2, the noise level 8 does not saturate unless a magnetic field of 200 (Oe) or more is applied. However, in the magneto-optical recording medium of Example 2 manufactured by the manufacturing method according to the present invention, 1
When a magnetic field of 00 (Oe) or more is applied, the noise level 6 is saturated. That is, the recording magnetic field sensitivity of the magneto-optical recording medium was improved by the manufacturing method of the present invention.

Comparative Example 3 In the magneto-optical recording medium of Comparative Example 3, one SiN film was sequentially formed on a polycarbonate substrate.
2,000 angstroms, TbFeCo alloy film 200
An Angstrom, SiN film was formed to 400 Å, and an Al reflective film was formed to 400 Å. The recording film of Comparative Example 3 was not a TbFeCo periodic multilayer film,
TbFeCo an alloy film, Fe _{9 0} Co _{1 0} a DC magnetron sputtering method using a composite target of arranging the Tb chip onto a target, sputtering during vacuum with pure Kr gas 8.0 × 10 ^{- 2} Pa Was manufactured by a DC magnetron sputtering method. The SiN film is composed of Ar and N
_The degree of vacuum at the time of sputtering 2.0 × 1
0 ^- was prepared by reactive RF magnetron sputtering at ¹ Pa. The Al reflection film was formed by an RF sputtering method using Ar gas.

(Comparative Example 4) The magneto-optical recording medium of Comparative Example 4 was such that a SiN film and a TbFeCo alloy film were sequentially formed on a polycarbonate substrate in a thickness of 1000 angstroms and a TbFeCo alloy film.
0 angstrom, 400 angstrom of SiN film, and 400 angstrom of Al reflective film. Recording film of Comparative Example 4, Fe _{9 0} Co _{1 0} a DC magnetron sputtering method using a composite target of arranging the Tb chip on the target beauty, sputtering during vacuum using pure Ar gas 8.0 × 10 ^{- It} was produced at ² Pa by DC magnetron sputtering. The SiN film is formed by using a mixed gas of Ar and N ₂ , and has a degree of vacuum of 2.0 × 10 -1 P during sputtering.
In a, it was prepared by a reactive RF magnetron sputtering method. The Al reflection film was formed by an RF sputtering method using Ar gas. Moreover, as the composition of the recording film of Comparative Example 4 and Comparative Example 3 is the same, to adjust the number of Tb chips was placed on the Fe _{9 0} Co _{1 0} target.

FIG. 3 shows the recording magnetic field dependence of the carrier level 9 and the noise level 10 of the magneto-optical recording medium of Comparative Example 3, and the carrier level 11 and the noise level 12 of the magneto-optical recording medium of Comparative Example 4. is there. The recording and reproducing conditions are the same as in the first embodiment. In the magneto-optical recording media of Comparative Example 3 and Comparative Example 4, the noise level does not saturate unless a magnetic field of 250 (Oe) or more is applied. Almost the same. That is, the recording magnetic field sensitivity of the magneto-optical recording medium manufactured by the sputtering method using the composite target does not improve even when pure Kr gas is used, and the two targets are formed using pure Kr gas using a Tb target and an Fe90Co10 target. Is simultaneously produced by sputtering with a DC magnetron sputtering method, the recording magnetic field sensitivity is improved.

[0023]

As described above, in the method for manufacturing a magneto-optical recording medium according to the present invention, the recording magnetic field sensitivity of the magneto-optical recording medium can be improved, and the magnetic field required for recording and erasing can be reduced to reduce the load on the drive. And is suitable as a magnetic field modulation overwrite medium. Further, since the medium has a four-layer structure, the structure is not complicated as compared with the conventional medium.

[Brief description of the drawings]

FIG. 1 is a diagram showing a recording magnetic field dependency of a carrier level and a noise level in a magneto-optical recording medium of Example 1 according to the present invention and a magneto-optical recording medium of Comparative Example 1.

FIG. 2 is a diagram showing a recording magnetic field dependence of a carrier level and a noise level in a magneto-optical recording medium of Example 2 according to the present invention and a magneto-optical recording medium of Comparative Example 2.

FIG. 3 is a diagram showing a recording magnetic field dependency of a carrier level and a noise level in the magneto-optical recording media of Comparative Examples 3 and 4.

[Explanation of symbols]

1 Dependency of carrier level on recording magnetic field in Example 1 2 Dependence of noise level on recording magnetic field in Example 1 3 Dependence of carrier level on recording magnetic field in Comparative Example 1 4 Dependence of noise level on recording magnetic field in Comparative Example 1 5 Dependence of carrier level on recording magnetic field in Example 2 6 Dependence of noise level on recording magnetic field in Example 2 7 Dependence of carrier level on recording magnetic field in Comparative Example 8 8 Dependence of noise level on recording magnetic field in Comparative Example 9 9 Comparative Example 3 10 Dependence of Carrier Level on Recording Magnetic Field in Comparative Example 3 11 Dependence of Carrier Level on Recording Magnetic Field in Comparative Example 4 12 Dependence of Noise Level on Recording Magnetic Field in Comparative Example 4

Claims (1)

(57) [Claims] In a method for manufacturing a magneto-optical recording medium, wherein an amorphous film of a Tb or Dy element and a transition metal element is used as a recording film and the recording film is formed by a sputtering method, pure Kr is used as a sputtering gas. Using a target whose main component is Tb or Dy and a target whose main component is a transition metal element, two targets are simultaneously sputtered and a metal whose main component is Tb or Dy and a metal whose main component is a transition metal element Are alternately stacked to form an amorphous film.