JPH04195750A - Manufacture of magnetooptic recording medium - Google Patents

Abstract

PURPOSE:To form a reading layer and a writing layer having suitably weak exchange bond by flattening the surface of a GdFeCoTi film by sputter etching and forming a TbFeTi film thereon. CONSTITUTION:A silicon nitride protective layer 2 is formed, and argon gas is introduced to sputter a GdFeCoTi target to form a GdFeCoTi film 3. Then, the surface is sputter etched with the argon gas to relatively flat the surface of the GdFeCoTi film as a reading layer. Thereafter, the target is sputtered with the argon gas to form a writing layer having weak exchange bond with the reading layer. Thus, in a magnetic recording medium, the TbFeTi film is formed after it is flattened by sputter etching the GdFeCoTi surface. In this manner, an exchange bonding force operating between the reading layer of the GdFeCoTi film and the writing layer of the TbFeTi film is weakened.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a magneto-optical recording medium, and more particularly, to a method for manufacturing a magneto-optical recording medium in which information is recorded and reproduced using a laser beam using the magneto-optic effect. .

[Conventional technology]

Conventionally, with the aim of improving the recording and reproduction characteristics of magneto-optical recording media, it has been proposed to use a two-layer magnetic film with an exchange coupling force as the magneto-optical recording layer (Japanese Patent Application Laid-Open No. 1983-1989).
No. 78652), the present inventors have also developed a readout device that is made of an amorphous alloy of gadolinium, iron, cobalt, and titanium, is perpendicularly magnetizable, has high oxidation resistance, exhibits a high Curie temperature, and has good reproduction characteristics and a low coercive force. layer (hereinafter referred to as GdFeCoTi
(hereinafter referred to as TbPeTi layer) and a writing layer (hereinafter referred to as TbPeTi layer), which is made of an amorphous alloy of terbium, iron, and titanium and has high coercive force with perpendicular magnetization, high oxidation resistance, and low Curie temperature, and good recording properties. The bits (partial magnetization reversal regions) written in the TbFeTi layer with a small laser beam energy are transferred to the GdFeCoTi layer with a large magneto-optic effect by exchange coupling force, and the TbFeTi layer is sequentially stacked.
We have already proposed something that reads out from the FeTi layer side (
JP-A-1-125609).

Next, a conventional method for manufacturing a magneto-optical recording medium will be described with reference to the drawings. FIG. 3 is a manufacturing process diagram for explaining a conventional example, and FIG. 4 is a schematic cross-sectional view of a magneto-optical recording medium using the conventional example shown in FIG.

In the figure, 1 is a substrate, 2 is a protective layer, and 23 is gadolinium/iron/cobalt/titanium (GdFeC).

GdFeCoTi layer consisting of an amorphous alloy of Ti), 24
25 is a TbFeTi layer made of an amorphous alloy of terbium-iron-titanium (TbFeTi), and 25 is a protective layer.

The substrate l is a photopolymer (hereinafter abbreviated as 2P)
Glass plate with , epoxy resin plate with 2P,
A polycarbonate resin plate or the like is used, and the protective layers 2 and 25 are made of silicon nitride, silicon oxynitride, or the like. A sputtering device is usually used to form each layer of such a magneto-optical recording medium.

As shown in FIG. 3, the conventional method for manufacturing a magneto-optical recording medium is that after the substrate manufacturing process a, the substrate l is mounted in a sputtering apparatus, and after the sputtering apparatus has been evacuated in the evacuation process,
In the substrate sputter etching step C, the substrate 1 is etched, and in the protective layer forming step d, a protective layer 2 is formed, and then in the step G
GdFeCoTi layer 2 in the dFeCoT i layer deposition step e.
3, and then in the TbFeTi layer forming step g
Finally, a protective layer 25 is formed on the Ti layer 24 in a protective layer forming step, and the magneto-optical recording medium thus produced is taken out from the sputtering apparatus in a magneto-optical recording medium take-out step j. be.

Note that before forming the protective layer 2, the surface of the substrate was slightly sputter-etched in order to strengthen the adhesion between the substrate and the protective layer, but this may be omitted.

[Problem to be solved by the invention]

However, magneto-optical recording media manufactured by the conventional magneto-optical recording medium manufacturing method described above have a pit error rate (BER) due to differences in the sputtering equipment used to manufacture them.
The problem was that it sometimes got better and sometimes worse.

As a result of intensive study by the inventors to solve this problem,
It has been discovered that the reason for the poor BER is that the exchange coupling force acting between the reading layer and the writing layer is too strong, and the present invention has been achieved.

[Means to solve the problem]

The method for manufacturing a magneto-optical recording medium of the present invention includes gadolinium
A low coercive force layer made of an amorphous alloy of iron, cobalt, and titanium that can be perpendicularly magnetized and has a high Curie point, and a
A magneto-optical recording medium in which a high coercive force layer made of an amorphous alloy of iron and titanium that can be perpendicularly magnetized and has a low Curie point is sequentially laminated, and the low coercive force layer and the high coercive force layer exert an exchange coupling force. In the manufacturing method, the high coercive force layer is formed after flattening the surface of the low coercive force layer by sputter etching, thereby forming an exchange coupling between the low coercive force layer and the high coercive force layer. Constructed to reduce force.

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a manufacturing process diagram for explaining an example of the present invention, and FIG. 2 is a schematic cross-sectional view of a magneto-optical recording medium manufactured using the embodiment shown in FIG.

In the figure, 1 is the substrate, 2 is the protective layer, and 3 is the Gci
After forming a film of an amorphous FeCoTi alloy, the surface was flattened by a little sputter etching to form a readout layer.
5 is a writing layer made of an amorphous alloy, and 5 is a protective layer formed thereon.

The magneto-optical recording medium manufactured by the magneto-optical recording medium manufacturing method of the present invention is formed by forming a TbFeTi film after flattening the GdFeCoTi surface by sputter etching.
It utilizes the phenomenon in which the exchange coupling force acting between the FeTi film and the writing layer becomes weaker.

When the film surface is sputter-etched, it appears that the film surface generally becomes flat according to the experiments conducted by the present inventors. This confirmation was carried out using transmission electron micrographs at a magnification of approximately 200,000 times using the replica method. The reason for the flatness is thought to be that the argon ions during sputter etching are incident on the film surface at various angles other than perpendicular.

It is not clear why the exchange coupling force becomes weaker when TbFeTi is formed after flattening the surface of the GdFeCoTi film by sputter etching than when sputter etching is not performed, but the shape of the underlying surface during the growth of the TbFeTi film is not clear. This is thought to be due to the difference in the magnetic properties induced by the two. This property varies depending on the material.

Note that the reason why the exchange coupling force differs depending on the sputtering apparatus used for film formation is thought to be that the atmosphere on the film surface is not constant from after the readout layer is formed until the writing layer is formed.

Next, embodiments of the present invention will be specifically described with reference to the drawings.

As shown in FIG. 1, the substrate l is mounted in the sputtering equipment in the substrate mounting step a, and the sputtering equipment is vacuum evacuated in step 3.
After evacuation to below X I O-'Torr, in the substrate sputter etching process C, argon gas is introduced and the substrate 1 is sputter etched by about 10 people, and then in the protective layer forming process D, a mixed gas of argon and nitrogen is used. A protective layer 2 of silicon nitride with a thickness of 800 mm was formed by reactive sputtering of a silicon target. Next, in the GdFeCoTi layer forming step e, argon gas was introduced and a G d Fe Co Ti target was sputtered, so that the ratio in atomic % was 234:62.8:12.
A GdFeCoTi film 3 with a ratio of 5:1.3 is formed to have a thickness of about 210 mm, and then in the GdFeTiff1t sputtering step d, this surface is sputter-etched with argon gas to form G'dFeC.

The surface of the Ti film was made relatively flat to serve as a readout layer. After that, in the TbFeTi layer forming step g, the Tb
By sputtering a FeTi target, a TbFeTi film 4 with a ratio of 20.0 to 78 and 4 to 16 atomic % was deposited to a thickness of about 1000 layers to form a writing layer weakly exchange-coupled with the reading layer.

Finally, in a protective layer forming step, a silicon target was reactively sputtered using a mixed gas of argon and nitrogen to form a protective layer 5 of silicon nitride having a thickness of 800 mm. The magneto-optical recording medium thus manufactured is taken out of the sputtering apparatus in a magneto-optical recording medium removal step 1.

The Kerr hysteresis loop of the produced magneto-optical recording medium exhibited a loop shape similar to that when no TbFeTi film was attached at 150° C., and was desirable as a magneto-optical recording medium utilizing exchange coupling force.

The fact that the loop shape is similar to that without the TbFeTi film means that the exchange coupling force between the GdFeCoTi film and the TbFeTi film is weak.

For comparison, a magneto-optical recording medium fabricated by forming TbFeTi on the surface of the GdFeCoTi film without sputter etching remained a well-formed loop even at 150°C due to the influence of the TbFeTi film. The exchange coupling force was quite strong.

Such a state is not desirable for a magneto-optical recording medium because writing of magnetization into the writing layer is affected by the direction of magnetization in the reading layer.

The magneto-optical recording medium of the above example was tested with an optical disk evaluation device.
Although the ER evaluation was good, the magneto-optical recording medium prepared in the comparative example was unsatisfactory.

Incidentally, in the above-described embodiments, an example was shown in which a substrate sputter etching process was performed, but this is for strengthening the adhesion between the substrate and the protective layer, and is not necessarily necessary.

〔Effect of the invention〕

The method for manufacturing a magneto-optical recording medium of the present invention includes a method for manufacturing a GdFeCoTi
By sputter etching the surface of the film to make it flat and forming a TbFeTi film on it, it is possible to form a reading layer and a writing layer with moderately weak exchange coupling forces, resulting in improved recording characteristics.
This has the effect that a magneto-optical recording medium with good reproduction characteristics can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a manufacturing process diagram for explaining one embodiment of the present invention, FIG. 2 is a schematic sectional view of a magneto-optical recording medium manufactured using the embodiment shown in FIG. 1, and FIG. 3 is a conventional FIG. 4 is a manufacturing process diagram for explaining one example, and is a schematic cross-sectional view of a magneto-optical recording medium manufactured using the conventional example shown in FIG. 1...Substrate, 2,5.25...Protective layer, 3
゜23...GdFeCoTi layer, 4, 24
・-・−T bFeTi layer, a... Substrate mounting process, b... Sputtering device vacuum evacuation process, C... - Substrate sputter etching process, d... Protective layer Film forming process, e...Gd
FeCoT i-layer film formation process, f...GdFeCo
Ti layer sputter etching step, g...TbF
eTi layer deposition process, h...protective layer deposition process, l.
...Magneto-optical recording medium ejection process. Agent Patent Attorney Susumu Uchihara Figure J

Claims (1)

[Claims] a first protective layer forming step of forming a protective layer on the substrate;
A step of forming a GdFeCoTi layer on the protective layer to form a low coercive force readout layer made of an amorphous alloy of gadolinium, iron, cobalt, and titanium and capable of perpendicular magnetization and having a high Curie point, and a sputtering process of this GdFeCoTi layer. a GdFeCoTi layer sputter etching step;
On the GdFeCoTi layer, a TbFeTi layer forming step of forming a high coercive force writing layer made of an amorphous alloy of terbium, iron, and titanium and capable of perpendicular magnetization and having a low Curie point; A method for manufacturing a magneto-optical recording medium, comprising: a second protective layer forming step for forming a protective layer.