JPH0765425A - Production of magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To provide a production method for a magneto-optical recording medium excellent in sensitivity for a recording magnetic field. CONSTITUTION:An amorphous recording film is formed by co-sputtering by using pure Kr as sputtering gas, a target essentially comprising Tb or Dy element, and a target essentially comprising transition metal elements to alternately deposit Tb or Dy element and the transition metal elements. By this method, the obtd. magneto-optical recording medium shows saturation in the noise level 2 with a smaller magnetic field applied and has improved sensitivity for a recording magnetic field compared to a medium produced by the conventional method using Ar as sputtering gas.

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 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 system,
The improvement of 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 and erasing to reduce the load on the drive. To improve recording sensitivity, a capping layer may be added to the TbFeCo film (Y. Yamada, M. Yoshihir).
o, N.N. Ohta, H .; Sukeda, T .; Nihar
a and H.A. Fujiwara; J. Magn. S
oc. Jpn. , 15, Suppl. Sl, 417 (1
991)), a GdFeCo film having a thickness of 10 nm and a thickness of 20
5-layer magneto-optical recording medium using a 2-layer film exchange-coupled with a TbFeCo film of 30 nm (Katsumi Ichiya, Shigeru Tsunashima, Shin Uchiyama; 15th Annual Meeting of the Japan Society for Applied Magnetics, 31p)
B-2, page 307) has been proposed. In these two magneto-optical recording media, a magnetic layer is newly added to a conventionally known magneto-optical recording medium so that the recording magnetic field sensitivity is improved by making a medium structure of 5 layers. It is more complex than the medium.

When pure Co is used as a sputtering gas when a Co / Pt or Co / Pd multilayer film is formed by a sputtering method, it is disclosed in the literature (PF Carcia, SI.
Shah and W. B. Zeper; Appl. P
hys. Lett. 56, 2345 (1990)) and (JP-A-5-6589). The Co / Pt or Co / Pd multilayer film produced by the sputtering method using pure Ar gas has a coercive force of about several hundreds Oe, which is very small as compared with the coercive force of the rare earth-transitive metal amorphous film. Moreover, the perpendicular magnetic anisotropy energy is also one tenth or less of the rare earth-transition metal amorphous film,
In addition, since the squareness ratio of the Kerr loop is far from 1, it is not suitable as a recording film for a magneto-optical recording medium. Therefore, it is necessary to increase the coercive force and the perpendicular magnetic anisotropy energy, or to bring the squareness ratio close to 1. In order to solve this problem, a sputtering method using Kr gas or Xe gas is used. In a magneto-optical recording medium, a recording film containing a rare earth-transition metal alloy is prepared by a sputtering method using a gas containing Kr or Xe, as disclosed in JP-A-4-298835 and JP-A-4-366441. It is shown.

In Japanese Patent Laid-Open No. 4-298835, the magnetic film contains a light rare earth element, so that the coercive force is small,
Therefore, in order to increase the coercive force and enhance the reproduction signal characteristics, the sputtering method is used using a gas containing Kr or Xe.

Further, there is no description about a target such as whether an alloy target or a composite target was used when producing a recording film. JP-A-4-36644
In JP-A-1 No. 1, a mixed gas that always contains Ar is used as the sputtering gas, and Pt and P are used for the recording film.
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 is deteriorated. Conversely, if no non-magnetic element is added,
There is no need to worry about squareness. In addition, Japanese Patent Laid-Open No. 4-366
In Japanese Patent Publication No. 441, a Kerr rotation angle at a maximum external magnetic field (θ _{K 1} ) and a residual Kerr rotation angle (θ _{K 2} ) at a zero external magnetic field are referred to as showing a rectangular loop with good Kerr sterilysis. Non-θ _{K 2} / θ _{K 1} of 0.
Although it is specified that it means 9 or more, both the examples and the comparative examples show that θ _{K 2} / θ _{K 1} is 0.9 or more, and no improvement in the Kerr loop squareness ratio is confirmed. This effect is hard to say.

[0006]

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

Producing a Co / Pt or Co / Pd multilayer film using pure Kr gas or pure Xe gas
It is disclosed in Japanese Patent Laid-Open No. 5-6589. In this,
Although it has been shown that the coercive force is increased, the squareness ratio is set to around 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 discloses a recording laser power sensitivity.
There is no description about the recording magnetic field sensitivity or for obtaining knowledge about the recording magnetic field sensitivity.

Japanese Unexamined Patent Publication (Kokai) No. 4-366441 also discloses a Kerr loop as a magnetic static characteristic, but does not describe actual read / write characteristics, particularly recording magnetic field sensitivity.

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

[0011]

[Means for Solving the Problems] Pure K as a sputtering gas
Using r, a target whose main component is Tb or Dy element and a target whose main component is transition metal element are used, and an amorphous film is formed by alternately stacking Tb or Dy element and transition metal oxide by a co-sputtering method. Form a film.

[0012]

By co-sputtering the FeCo target with Tb or Dy using Kr, which is an element heavier than Ar, the energy distribution of sputtered atoms (Tb, Dy, Fe, Co) shifts to the high energy side. As a result, the short-range order of the amorphous film is changed, and the anisotropic dispersion of the magnetic film is changed to improve the recording magnetic field sensitivity. This phenomenon has been newly discovered experimentally.

[0013]

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

Example 1 The magneto-optical recording medium in Example 1 is a SiN film having a thickness of 1000 Å, a Tb / FeCo periodic multilayer film having a thickness of 200 Å, a SiN film having a thickness of 400 Å, and an Al reflection film on a polycarbonate substrate. Was formed into a 400 angstrom film. At this time, the Tb layer thickness of the Tb / FeCo periodic multilayer film is 4 Å and the FeCo layer thickness is 6 Å. The SiN film was formed by a reactive RF magnetro sputtering method using a mixed gas of Ar and N ₂ at a vacuum degree of 2.0 × 10 ⁻¹ Pa during sputtering.
The Al reflection film was formed by the RF sputtering method using Ar gas. The Tb / FeCo periodic multilayer film in Example 1 is Tb
Using a target and Fe _{9 0} Co _{1 0} target, substrate rotation speed was fixed at 20 rpm, sputtering time of vacuum degree 8.0 × 10 using pure Kr gas ^- was produced by DC magnetron co-sputtering method in ² Pa.

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 having a thickness of 1000 Å, a Tb / FeCo periodic multilayer film having a thickness of 200 Å, a SiN film having a thickness of 400 Å, and an Al reflection film having a thickness of 400 Å were sequentially formed on a polycarbonate substrate. At this time, the Tb layer thickness of the Tb / FeCo periodic multilayer film is 4 Å and the FeCo layer thickness is 6 Å. The SiN film was formed by a reactive RF magnetron sputtering method using a mixed gas of Ar and N ₂ at a vacuum degree of 2.0 × 10 ⁻¹ Pa during sputtering. The Al reflection film was formed by the RF sputtering method using Ar gas. The Tb / FeCo periodic multilayer film in Comparative Example 1 uses a Tb target and a Fe ₉₀ Co ₁₀ target,
Substrate rotation speed was fixed at 20 rpm, sputtering time of vacuum degree 8.0 × 10 using pure Ar gas ^- was produced by DC magnetron co-sputtering method in ² Pa. That is, Tb
The film thickness and manufacturing conditions of each layer are exactly the same as those of the magneto-optical recording medium of Example 1 except that Ar was used instead of Kr when the / FeCo periodic multilayer film was formed.

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.
And the recording magnetic field dependency of the noise level 4. Recording / reproducing conditions are a linear velocity of 11 m / s and a recording frequency of 3.
It is 7 MHz and the reproduction laser power is 1.0 mW. In the magneto-optical recording medium of Comparative Example 1, the noise level 4 is not saturated 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 manufacturing method of the present invention,
The recording magnetic field sensitivity of the magneto-optical recording medium is improved.

(Example 2) The magneto-optical recording medium in Example 2 was manufactured by the same method as the magneto-optical recording medium in Example 1 above. The difference from Example 1 is the Tb layer thickness and the FeCo layer thickness in the Tb / FeCo periodic multilayer film. The Tb layer thickness of the Tb / FeCo periodic multilayer film of Example 2 was 6.
It is 4 angstroms and the FeCo layer thickness is 9.6 angstroms.

Comparative Example 2 Further, as Comparative Example 2, a magneto-optical recording medium was manufactured. It was manufactured by the same method as the magneto-optical recording medium of Comparative Example 1 above. The difference from Comparative Example 1 is that Tb
/ FeCo layer thickness in the FeCo periodic multilayer film. The Tb / FeCo periodic multilayer film of Comparative Example 2 has a Tb layer thickness of 6.4 Å and a FeCo layer thickness of 9.6 Å. That is, Tb /
The film thickness of each layer and the manufacturing conditions are exactly the same as those of the magneto-optical recording medium of Example 2 of the present invention except that Ar was used instead of Kr when the FeCo periodic multilayer film was formed.

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

COMPARATIVE EXAMPLE 3 The magneto-optical recording medium in Comparative Example 3 has a SiN film formed by sequentially depositing 1 SiN film on a polycarbonate substrate.
000 angstrom, TbFeCo alloy film 200
An Angstrom and a SiN film were formed to 400 angstroms, and an Al reflection film was formed to 400 angstroms. The recording film of Comparative Example 3 is 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 In DC magnetron sputtering method. SiN film has Ar and N
_Using a mixed gas of _2, the degree of vacuum during sputtering is 2.0 × 1.
0 ^- was prepared by reactive RF magnetron sputtering at ¹ Pa. The Al reflection film was formed by the RF sputtering method using Ar gas.

COMPARATIVE EXAMPLE 4 The magneto-optical recording medium in Comparative Example 4 has a SiN film of 1000 Å and a TbFeCo alloy film of 20 in sequence on a polycarbonate substrate.
0 Å, SiN film was 400 Å, and Al reflection film was 400 Å. The recording film of Comparative Example 4 was a DC magnetron sputtering method using a composite target in which a Tb chip was placed on a Fe ₉₀ Co ₁₀ target and a vacuum degree at the time of sputtering 8.0 × 10 ⁻ with pure Ar gas. ^It was prepared by a DC magnetron sputtering method at ² Pa. The SiN film uses a mixed gas of Ar and N ₂ and has a vacuum degree of 2.0 × 10 −1 P during sputtering.
In a, it was prepared by the reactive RF magnetron sputtering method. The Al reflection film was formed by the RF sputtering method using Ar gas. Further, the number of Tb chips arranged on the Fe ₉₀ Co ₁₀ target was adjusted so that the recording films of Comparative Example 3 and Comparative Example 4 had the same composition.

FIG. 3 shows the recording magnetic field dependence of the carrier level 9 and noise level 10 of the magneto-optical recording medium of Comparative Example 3 and the carrier level 11 and noise level 12 of the magneto-optical recording medium of Comparative Example 4. is there. The recording / 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 is not saturated unless a magnetic field of 250 (Oe) or more is applied, and the magnitude of the recording magnetic field required for the noise level to be saturated in both is It is 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 is not improved even by using the pure Kr gas, and the pure Kr gas is used by using the Tb target and the Fe ₉₀ Co ₁₀ target. DC magnetron
The recording magnetic field sensitivity is improved when manufactured by the co-sputtering method.

[0023]

As described above, in the method of manufacturing a magneto-optical recording medium of the present invention, the sensitivity of the recording magnetic field 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. It is also suitable as a magnetic field modulation overwrite medium. Furthermore, since it has a four-layer medium structure, it is not complicated as compared with the conventional medium.

[Brief description of drawings]

FIG. 1 is a diagram showing the recording magnetic field dependence 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 the recording magnetic field dependence of the carrier level and the noise level in the magneto-optical recording medium of Example 2 and the magneto-optical recording medium of Comparative Example 2 according to the present invention.

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

[Explanation of symbols]

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

Claims (1)

[Claims] 1. A method of manufacturing a magneto-optical recording medium in which 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 sutter method, and pure Kr is used as a sputtering gas. A target containing a Tb or Dy element as a main component and a target containing a transition metal element as a main component are used, and a metal containing Tb or Dy as a main component and a metal containing a transition metal element as a main component are alternately laminated by a co-sputtering method. A method of manufacturing a magneto-optical recording medium, which comprises forming an amorphous film.