JPH0448449A - Production of magneto-optical disk - Google Patents

Abstract

PURPOSE:To improve recording sensitivity by using plural electromagnets to constitute a magnet to apply a magnetic field on a target, and controlling the current in the electromagnets by on-off control or at a specified value so as to control the intensity of the magnetic field and the columnar degree of grains in the recording film. CONSTITUTION:A target 31 is a disk type, to which plural numbers of electromagnets 32 are disposed in the center and along concentrical circles. This target 31 is disposed in a sputtering chamber 33, as two kinds of targets, one for formation of a recording film and the other for formation of a protective film. A film containing column-like grains and a film containing no column- like grains can be formed by controlling the current applied on these electromagnets to specified value. Thereby, a magneto-optical recording medium having a four-layer structure comprising a protective film 47, recording film 48 containing no column-like grains, recording film 49 comprising column-like grains, and protective film cane easily obtained in a simplified process without increasing the number of targets. The obtd. recording medium has higher sensitivity.

Description

[Detailed Description of the Invention] [Summary] Regarding a method of manufacturing a magneto-optical recording medium, in order to improve the data transfer speed, the recording sensitivity is such that even when the magneto-optical disk is rotated at high speed, it can be recorded with a small laser power. A target equipped with a magnet for applying a magnetic field and a substrate are placed facing each other in a vacuum container, a sputtering gas is introduced into the container, and a magnetron sputtering method is provided. In the method for manufacturing a magneto-optical recording medium having a rare earth-transition metal amorphous alloy as a recording film on the substrate, the magnet for applying a magnetic field to the target is composed of a plurality of electromagnets, and the magnetic field is applied to the plurality of electromagnets. The strength of the magnetic field is controlled by turning the current on and off or controlling it to a predetermined value, thereby controlling the degree of columnarization of the recording film.

[Industrial application field] The present invention relates to a method for manufacturing a magneto-optical recording medium.

In magneto-optical disk devices, it is desired to improve the data transfer speed in order to expand the field of application as memory.

Therefore, it is desired to improve the recording sensitivity of the magneto-optical disk medium itself so that recording can be performed with a small laser power even when the magneto-optical disk is rotated at high speed.

A method for easily manufacturing this magneto-optical recording medium is also desired.

[Conventional technology]

Conventionally, rare earth-transition metal amorphous alloy thin films have generally been used as magnetic films for magneto-optical disks.

These rare earth elements include terbium (Tb), dysprosium (Dy), gadolinium (Gd), and holmium (
Iron (Fe), cobalt (Co), etc. are used as transition metal elements, and amorphous alloy thin films such as terbium-iron-cobalt (TbFeCo) and dysprosium-iron-cobalt (DyFeCo) are used. is forming.

By the way, the magneto-optical disk having the magneto-optical recording medium of the rare earth-transition metal amorphous alloy was heated at 3600 rpm.
In order to perform magneto-optical recording by rotating at a high speed of 1.
It requires an extremely high writing laser power of 5 sec.

However, it is difficult to obtain such a large laser power with a semiconductor laser device. Helium-neon (He-Ne) also provides high laser power.
If a laser light source is used, the device becomes larger and consumes more power, and the magnetic recording medium that is formed also becomes more expensive.

Conventionally, magneto-optical disk recording media that combine high signal quality and high sensitivity have been made up of substrates, protective films, non-columnar recording films,
The present applicant has previously proposed a recording medium having a four-layer structure of a columnar recording film/protective film.

The structure of this columnar recording film is schematically shown in FIG. As shown in the figure, a recording film 1 having a typical columnar structure consists of fine columnar bodies (columns) 3 having an axis perpendicular to a recording surface 2.
is composed of a collection of

A gap 4 is formed between each columnar body 3 in which the columnar bodies 3 are not in contact with each other. Such a columnar recording film is observed using a scanning electron microscope.

By providing such a columnar recording film, since the gaps 4 of the columnar recording film have poor thermal conductivity, it is difficult to transfer heat laterally, and laser light during recording is efficiently converted into thermal energy. By efficiently increasing the temperature of the recording film, the recording sensitivity can be increased.

Furthermore, by laminating a non-columnar recording film on the columnar recording film, multiple reflections of the laser beam occur at the interface between the columnar recording film and the non-columnar recording film, thereby improving writing efficiency.
The signal quality of written records can be improved.

[Problem to be solved by the invention]

By the way, in order to form a recording film having the above-mentioned four-layer structure, for example, a combination of substrate/protective film/columnar recording film/protective film or substrate/protective film is required.
Compared to the case of forming a three-layer recording film of a protective film/non-columnized recording film/protective film, one additional target for sputtering is required, and one additional recording film manufacturing process is required. This poses a problem in that it takes extra time and increases the cost of the magneto-optical recording medium to be formed.

Further, the structure of a commonly used magnetron sputtering apparatus is as shown in FIG.
2 and a target 13 are arranged opposite to each other, and this target has a permanent magnet 14A provided at the lower part of the target,
A magnetic field is applied by 14B. As shown in Figure 7, the structure of this permanent magnet is that the permanent magnet 1 in the center is
4A and a permanent magnet 14B arranged concentrically around it.
It consists of

These targets are targets for forming a protective film,
Three types of targets, a target for forming a columnar recording film and a target for forming a non-columnar recording film, are arranged in a circumferential manner, and a shutter having an opening is arranged between the target and the substrate,
The substrate rotates on a circumference on which the plurality of targets are arranged,
When the substrate is rotated and moved onto a predetermined target, the shutter opens and a high voltage is applied between the substrate and the target to deposit components of the target onto the substrate.

However, in conventional targets using permanent magnets, the erosion area (the area where the target is most often used and scraped during sputtering) is limited, so there is a problem that the entire area of the target cannot be used effectively.

The present invention solves the above-mentioned problems, and aims to provide a method for manufacturing a magneto-optical recording medium that does not require an increase in the number of targets even when the number of stacked recording films increases, and in which the erosion area is not limited.

[Means to solve the problem]

A method for manufacturing a magneto-optical recording medium of the present invention that achieves the above object includes arranging a target equipped with a magnet that generates a magnetic field and a substrate facing each other in a vacuum container, introducing sputtering gas into the container, and In the method for manufacturing a magneto-optical recording medium using a rare earth-transition metal amorphous alloy as a recording film on the substrate by a sputtering method, the magnet for generating a magnetic field in the target is composed of a plurality of electromagnets, ! The strength of the magnetic field is controlled by turning on and off the current applied to the magnet or controlling it to a predetermined value, thereby controlling the degree of columnarization of the recording film. Furthermore, a plurality of NvL stones for generating the magnetic field are arranged concentrically with respect to the target, and a magnetic field is partially generated along the concentric circle facing the target by applying a current to the electromagnet. .

[For production]

Generally, as the magnitude of the magnetic field applied to the target increases, the degree of columnarization of the recording film tends to decrease, and as the magnitude of the magnetic field applied to the target decreases, the degree of columnarization tends to increase. be.

Further, as the gas pressure of the sputtering gas increases, the degree of columnarization increases, and as the sputtering gas pressure decreases, the degree of columnarization decreases.

Therefore, in the conventional method, when forming a non-columnar recording film and a columnar recording film, two targets of the same composition are provided, and
A non-columnar recording film is formed by increasing the strength of the magnetic field applied to one target, and a columnar recording film is formed by decreasing the strength of the magnetic field applied to the other target.

Figure 5 is a diagram showing the relationship between the magnetron magnetic field and the sensitivity of the magneto-optical recording medium. Show the output.

As shown by curve 21 in the figure, it can be seen that when the magnetic field during sputter film formation becomes 2000 e or less, the output of the writing laser power decreases. This means that the weaker the magnetic field strength during sputtering film formation, the more columnar the recording film becomes.
Bit writing can be started with low laser power.

Therefore, in the present invention, the target for forming the non-columnar recording film and the columnar recording film is a common target equipped with a plurality of electromagnets, and the strength of the magnetic field applied to the target is applied to the plurality of electromagnets. The degree of columnarization of the recording film formed by sputtering can be controlled by controlling the strength of the current applied or by turning on and off the current applied to the plurality of 11N stones.

Further, by controlling the current value of the plurality of electromagnets that apply a magnetic field to the target, or by turning the current value on and off, the erosion region can be controlled to a desired region.

By controlling the current value applied to the target in this way, it is possible to form a non-columnar recording film and a columnar recording film with one common target, which reduces the number of targets required, and also allows for non-columnar recording. There is no need to move the substrate onto two types of targets: a film forming target and a columnar recording film forming target, so the time for forming the recording film can also be shortened.

In addition, by controlling the current applied to the target electromagnet, the erosion area can be controlled within an appropriate range.
Since the number of times the target is used increases, the cost required for sputtering decreases.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram of an apparatus used in the method of the present invention, and FIG. 2 is a schematic diagram of a target used in the method of the present invention, which is a plan view of the target viewed from the back side.

As shown in FIGS. 1 and 2, a target 31 used in the method of the present invention is disc-shaped, and a plurality of electromagnets 32 are arranged at the center of this disc-shaped target and along concentric circles of the target. do. Two types of targets, a protective film forming target and a recording film forming target, are installed in the sputtering container 33, and the columnar recording film and the non-columnar recording film are connected to the electromagnet of the recording film forming target. It is formed by controlling the current value applied to a predetermined value.

In the method of the present invention, an RF type magnetron sputtering apparatus equipped with an electromagnet as shown in FIG. 1 was used, but this apparatus can also be applied to a DC sputtering apparatus.

The case where a magneto-optical disk is formed using such a method of the present invention will be described.

As shown in FIGS. 3 and 4, the sputtering container 33
A substrate 41, a protective film forming target 42, and a recording film forming target 43 are placed facing each other in the inside, and a shutter 44 is placed between the substrate and both targets. Next, the inside of the container is evacuated to a high vacuum using an exhaust pump (not shown) connected to the exhaust pipe 45, and then Ar gas is supplied from the gas supply pipe 46 until the pressure inside the container reaches 1.8 Pa.

Next, the substrate 41 is rotated to form a protective film formation target 4.
2, open the shutter 44 and apply a high frequency voltage between the substrate and the target, and while forming a magnetic field on the target with the electromagnet 32, a 90 nm thick film is placed on the substrate.
A protective film 47 made of a terbium-silicon dioxide (TbSiO□) film is formed. By adjusting the magnitude of the magnetic fields of the inner and outer electromagnets of the electromagnet 32, the erosion region can be expanded to a desired range, and the target for forming a protective film will not be partially scraped even after multiple sputtering operations, making it effective. Can be used for a long time.

Further, the substrate 41 is rotated to form a target 43 for forming a recording film.
, and open the shutter 44 to apply a high frequency voltage between the substrate and the target for forming a recording film. Magnet 32 generates a magnetic field of 10,000
The magnetic field is stronger than e, and the sputtering gas pressure is 0.2P.
A non-columnarized recording film 48 of terbium-iron-copal l-(TbFeCo) having a thickness of Ions is formed on the substrate in a state where the thickness is reduced to a.

Furthermore, without moving the substrate 41 as it is, the magnetic field of the electromagnet 32 that applies a magnetic field to the target 43 for forming a recording film is set to a weak magnetic field of 1000 e, and the sputtering gas pressure is increased to 1.8 Pa, and the sputtering gas is sputtered onto the substrate. A columnar recording film 49 having a thickness of 80 nm is formed.

In this way, the strength of the magnetic field applied to the target can be adjusted by controlling the strength of the current flowing through the electromagnet that applies the magnetic field to the recording film forming target using one target without rotating the substrate. By controlling the above, both a columnar recording film and a non-columnar recording film can be easily formed.

Next, the substrate 41 is rotated to form a protective film formation target 4.
2, open the shutter 44 and apply a high frequency voltage between the substrate and the target, and while forming a magnetic field on the target by the electromagnet 32, a 9 On-thick film is placed on the substrate.
A protective film 47 made of a terbium-silicon dioxide (TbSiO□) film is formed.

In this way, the same target was used to form the non-columnarized recording film/columnarized recording film, and the Ar gas pressure was set to 11
By instantaneously changing the size of the M1 stones, continuous film formation becomes possible.

In addition, by replacing the conventionally used permanent magnet with MTa stone as the magnet that applies the magnetic field to the target,
The number of targets can be reduced by one, and the sputtering time is reduced from the usual 50 minutes (including the time for forming the protective film) to 4 minutes.
It can be shortened to 0 minutes.

Furthermore, the erosion area can be changed by controlling the current value flowing through the electromagnets or by switching the number of electromagnets, so a normal permanent magnet sputtering device can only produce 1,200 magneto-optical disks with one target. However, with the device using the electromagnet of the present invention, it has become possible to manufacture twice as many 2,300 magneto-optical disks.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a magneto-optical recording medium having a four-layer structure of a protective film, a non-columnar recording film, a columnar recording film, and a non-columnar recording film can increase the number of targets. It can be easily obtained with a shortened manufacturing process.

In addition, since the magnetic field applied to the target can be controlled by changing the strength of the current applied to the electromagnet, the erosion area can be controlled within the desired range, increasing target usage efficiency and reducing target consumption. This has the effect of reducing the cost required for sputtering.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the method of the present invention, FIG. 2 is a schematic diagram of a target used in the method of the present invention, FIG. 3 is a cross-sectional view of a magneto-optical disk formed by the method of the present invention, and FIG. 4 is a schematic diagram showing the method of the present invention. A schematic diagram showing an embodiment of the method of the present invention, FIG. 5 is a diagram of the relationship between the magnetic field of the magnetron and the sensitivity of the magneto-optical recording medium, FIG. 6 is a schematic diagram of the apparatus used in the conventional method, and FIG. A schematic diagram of a target used in the conventional method. FIG. 8 is a schematic diagram of a columnar recording film. In the figure, 31 is a target, 32 is an electromagnet, 33 is a sputtering container, 41 is a substrate, 42 is a target for forming a protective film, 43 is a target for forming a recording film, 44 is a shutter, 45 is an exhaust pipe, and 46 is a gas supply pipe. , 47 is a protective film, 48 is a non-$4
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Claims (2)

[Claims] (1) Target equipped with a magnet that applies a magnetic field (31
, 42, 43) and the substrate (41) in a vacuum container (33).
In a method for manufacturing a magneto-optical recording medium having a rare earth-transition metal amorphous alloy as a recording film on the substrate by a magnetron sputtering method, the targets ( 31, 42, 43) is composed of a plurality of electromagnets (32), and the magnetic field applied to the target can be controlled by turning on/off the current applied to the plurality of electromagnets or controlling it to a predetermined value. A method for producing a magneto-optical recording medium, characterized in that the degree of columnarization of the recording film is controlled by controlling the strength. (2) A plurality of electromagnets (32) for applying the magnetic field are arranged concentrically opposite to each other on the back side of the target (31, 42, 43), and a current is applied to the electromagnet (32) to apply the magnetic field to the target. 2. The method of manufacturing a magneto-optical recording medium according to claim 1, wherein the magnetic field is generated concentrically.