JP2576285B2 - Magneto-optical recording medium manufacturing method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method of manufacturing a magneto-optical recording medium, and more particularly to a method of manufacturing a magneto-optical recording medium in which information is recorded / reproduced by laser light utilizing a magneto-optical effect. .

[Conventional technology]

Conventionally, an exchange coupling force has been applied as a magneto-optical recording layer for the purpose of improving the recording and reproducing characteristics of a magneto-optical recording medium.
A device using a magnetic layer has been proposed (Japanese Patent Laid-Open No.
No. 78652), the present inventors have also made a perpendicular magnetization made of an amorphous alloy of gadolinium / iron / cobalt / titanium and have high oxidation resistance and high Curie temperature. Layer (hereinafter referred to as GdFeCoTi layer)
And a write layer (hereinafter referred to as Tb) having perpendicular magnetization, which is made of an amorphous alloy of terbium and iron / titanium, has high oxidation resistance, and has a low Curie temperature and a high coercive force with good recording characteristics.
Bits (partial magnetization reversal regions) written in the TbFeTi layer with a small amount of laser light energy are transferred to the GdFeCoTi layer with a large magneto-optical effect by exchange coupling force, and read from the TbFeTi layer side. One has already been proposed (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 one example of a conventional example, and FIG. 4 is a schematic 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, 23 is a GdFeCoTi layer made of an amorphous alloy of gadolinium / iron / cobalt / titanium (GdFeCoTi), and 24 is TVium / iron / titanium (TbFe
A TbFeTi layer made of an amorphous alloy of Ti), 25 is a protective layer.

The substrate 1 is a photopolymer (hereinafter abbreviated as 2P)
, An epoxy resin plate with 2P, a polycarbonate resin plate, etc. are used.
For example, silicon nitride or silicon oxynitride is used. For forming each layer of such a magneto-optical recording medium, a sputtering apparatus is usually used.

As shown in FIG. 3, a conventional method of manufacturing a magneto-optical recording medium includes mounting a substrate 1 in a sputtering apparatus in a substrate manufacturing step a, evacuating the substrate in a sputtering apparatus evacuation step b, and then performing substrate sputter etching. In step c, the substrate 1 is sputter-etched to form a protective layer 2 in a protective layer forming step d, and then a GdFeCoTi layer 23 is formed in a GdFeCoTi layer forming step e.
A TbFeTi layer 24 is formed in a TbFeTi layer forming step g, and a protective layer 25 is formed in a protective layer forming step h. The magneto-optical recording medium thus manufactured is subjected to magneto-optical recording by a sputtering apparatus. It is taken out in the medium taking out step i.

Before the formation of 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.

[Problems to be solved by the invention]

However, the magneto-optical recording medium manufactured by the above-described conventional method for manufacturing a magneto-optical recording medium has a problem that a bit error rate (BER) is improved or deteriorated depending on a different sputtering apparatus to be manufactured. .

The present inventors have conducted intensive studies to solve this problem, and as a result, have found that the BER deteriorates because the exchange coupling force acting between the read layer and the write layer is too strong. Was.

[Means for solving the problem]

The method of manufacturing a magneto-optical recording medium according to the present invention includes a low coercivity layer having perpendicular magnetization and a high Curie point, which is made of an amorphous alloy of gadolinium / iron / cobalt / titanium; A method for manufacturing a magneto-optical recording medium, in which a high coercivity layer having perpendicular magnetization and a low Curie point made of an alloy is sequentially laminated, and the low coercivity layer and the high coercivity layer act on exchange coupling force. The high coercivity layer is configured so as to weaken the exchange coupling force acting between the low coercivity layer and the high coercivity layer by forming a film after flattening the surface of the low coercivity layer by sputter etching. Is done.

〔Example〕

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

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

In the figure, 1 is a substrate, 2 is a protective layer, and 3 is GdFe
After forming an amorphous alloy of CoTi, the surface is slightly flattened by sputter etching to form a readout layer, and 4 is a writing layer made of an amorphous alloy of TbFeTi formed thereon. Reference numeral 5 denotes a protective layer formed thereon.

The magneto-optical recording medium manufactured by the method of manufacturing a magneto-optical recording medium of the present invention is formed by forming a TbFeTi film after flattening the surface of the GdFeCoTi by sputter etching, so that the reading layer of the GdFeCoTi film and the TbFeTi film are written. It utilizes the phenomenon that the exchange coupling force acting between the embedded layers is weakened.

When the film surface is sputter-etched, the film surface generally seems to be flat within the scope of the experiments performed by the present inventors. This confirmation was made by a transmission electron microscope photograph of about 200,000 times by the replica method. It is considered that the reason why the surface becomes flat is that the angle of incidence of the argon ion being sputter-etched on the film surface has various angles in addition to the perpendicular incidence.

The reason why the exchange coupling force is weaker when sputter-etching the TbFeTi film than after not sputter-etching when forming the TbFeTi film after flattening the GdFeCoTi film surface by sputter etching is unknown, but depending on the underlying surface shape during the growth of the TbFeTi film film This is probably because the induced magnetic properties are different.
This property depends on the material.

The reason why the exchange coupling force differs depending on the sputtering apparatus for forming a film is presumably because the atmosphere on the film surface is not constant after the formation of the readout layer until the formation of the write layer.

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

As shown in FIG. 1, the substrate 1 is mounted in a sputtering apparatus in a substrate mounting step a, and 3
After evacuating to a pressure of ^10-7 Torr or less, the substrate 1 is sputter-etched by about 10 ° by introducing an argon gas in a substrate-sputtering-etching step c.
Then, a mixed gas of argon and nitrogen was introduced, and a silicon target was reactively sputtered to form a 800-nm-thick silicon nitride protective layer 2. Next, in a GdFeCoTi layer forming step e, an argon gas is introduced and a GdFeCoTi target is sputtered to obtain 23.4 to 62.8 to 12.5 by atomic%.
A GdFeCoTi film 3 of 1.3 forms a film of about 210 mm thickness,
In the GdFeTi layer sputter etching step d, this surface is sputter-etched with argon
The surface of the Ti film was made relatively flat to form a readout layer. Td
In the FeTi layer forming step g, the TbFeTi target was sputtered with an argon gas to obtain 20.0 to 78.4 to 1.
A TbFeTi film 4 of No. 6 was formed to a thickness of about 1000 ° to form a write layer weakly exchange-coupled to the read layer. Finally, in a protective layer forming step h, a silicon target was reactively sputtered with a mixed gas of argon and nitrogen to form a 800-nm-thick protective layer 5 of silicon nitride. The magneto-optical recording medium manufactured in this manner is subjected to a magneto-optical recording medium removal step i.
And is taken out of the sputtering apparatus.

The Kerr hysteresis loop of the manufactured magneto-optical recording medium exhibited a loop shape at 150 ° C. as if no TbFeTi film was formed, and was desirable as a magneto-optical recording medium utilizing exchange coupling force.

The resemblance of the loop shape without the TbFeTi film means that the exchange coupling force between the GdFeCoTi film and the TbFeTi film is weak.

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

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

Using the magneto-optical recording medium of the above embodiment with an optical disk evaluation device
Although the BER evaluation was good, the magneto-optical recording medium produced in the comparative example was insufficient.

In the above-described embodiment, the example in which the substrate sputter etching step is performed is shown. However, this is not necessarily required, but is for enhancing the adhesion between the substrate and the protective layer.

〔The invention's effect〕

In the method of manufacturing a magneto-optical recording medium of the present invention, the surface of a GdFeCoTi film is flattened by sputter etching, and TbFeTi
By forming the film, it is possible to form a read layer and a write layer whose exchange coupling force is appropriately weak, and thus it is possible to manufacture a magneto-optical recording medium having good recording characteristics and reproduction characteristics.

[Brief description of the drawings]

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 by using the embodiment shown in FIG. 1, and FIG. FIG. 4 is a schematic sectional view of a magneto-optical recording medium manufactured by using the conventional example shown in FIG. 1 ... substrate, 2,5,25 ... protective layer, 3,23 ... GdFeCoTi layer,
4, 24 ... TbFeTi layer, a ... substrate mounting step, b ... sputtering apparatus evacuation step, c ... substrate sputter etching step, d ... protective layer film forming step, e ... GdFeCoTi layer film forming step, f ... GdFeCoTi
Layer sputter etching step, g ... TbFeTi layer film forming step,
h: protective layer forming step, i: magneto-optical recording medium take-out step.

Claims (1)

(57) [Claims] A first protective layer forming step of forming a protective layer on a substrate; and a vertically magnetizable and high-magnetizable amorphous alloy of gadolinium / iron / cobalt / titanium on the protective layer. GdFeCoTi forming low coercivity readout layer with Curie point
A GdFeCoTi layer sputter etching step of sputter-etching the GdFeCoTi layer;
A TbFeTi layer forming step of forming a perpendicularly magnetizable and high coercive force writing layer having a low Curie point composed of an amorphous alloy of terbium, iron and titanium on the layer, and a protective layer on the TbFeTi layer. And a second protective layer forming step of forming a magnetic recording medium.