JPH0630182B2 - Manufacturing method of magneto-optical recording element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention improves the reproducing performance index of a magneto-optical recording element, especially a rewritable element, and improves the environment resistance of a magneto-optical recording medium, and further, a film formed by sputtering. The present invention relates to a method for manufacturing a magneto-optical recording element with improved productivity in formation.

(Prior Art) In recent years, high-density recording using a magneto-optical recording element has been actively researched. This is to write pits by projecting a laser beam to locally heat the recording medium and utilize the magneto-optical effect. This is a method of recording a large amount of information that is read out in high density. This magneto-optical recording medium can be obtained by forming an amorphous metal perpendicular magnetization film composed of a rare earth element-transition metal mainly by a sputtering method.

According to this magneto-optical recording method, it has been proposed to provide a dielectric layer between the substrate and the recording medium together with the improvement of the recording medium in order to improve the magneto-optical characteristics.

That is, in a magneto-optical recording element in which a magnetic layer made of a magneto-optical recording medium is formed on a transparent substrate via a transparent dielectric layer,
Conditions for causing multiple reflection of the film thickness t of the dielectric layer when the laser light is projected from the substrate side and reproduced, t = λ / 4n · (2m + 1) (where λ: reproduction wavelength of laser light, n : Refractive index of dielectric layer, m = 0, 1, 2, 3 ...
...), the enhancement of the extreme car effect can be obtained, and the reproduction performance is remarkably improved.

Such dielectric materials include oxides such as CeO ₂ , ZrO ₂ , TiO ₂ , Al ₂ O ₃ and SiO, and non-oxides such as Si ₃ N ₄ , AlN and ZnS,
This non-oxide has the advantage that oxygen originating from the dielectric material does not exist at the interface of the amorphous metal perpendicular magnetization film, and the deterioration of the magnetic layer due to diffusion of oxygen is small. A dielectric layer having long-term stability and high reliability can be obtained by selecting an importer material having excellent barrier properties such as.

In addition, a plastic material has come to be used for a substrate for an optical disc used for this high-density recording because it is lightweight, low priced, durable and safe, and a substrate with a guide track by injection molding can be reproduced in a large amount. In particular, a magneto-optical recording substrate is manufactured by using a polymer material having excellent translucency, such as polycarbonate resin or polymethylmethacrylate resin.

Further, in such an existing situation, when reproducing by emitting a laser beam from the substrate side of a magneto-optical recording element in which a magnetic layer is formed on this plastic substrate via a non-oxide type dielectric layer, It can be said that the enhancement effect is increased as the refractive index of the dielectric layer is larger than that of the substrate.

ZnS (n = 2.3) is used for the non-oxide dielectric layer with a high refractive index.
5), they are relatively inferior in environmental resistance, and when exposed to a high temperature and high humidity environment for a long period of time, oxygen in the atmosphere passes through a large number of pinholes generated during the process of forming the dielectric layer, Water or the like is supplied to the magnetic layer, and various deterioration phenomena such as oxidation of the magnetic layer occur. However, Si ₄ N ₄ has a refractive index of 1.9.
~ 2.1, but a dense film quality without pinholes,
Excellent environmental resistance. Therefore, it is desired to make the environment resistant property effective and to improve the refractive index of the Si ₃ N ₄ dielectric layer itself, but this point has not been proposed yet.

As the present inventors has already filed in Japanese Patent Application No. Sho 59 years No. 143,079, focusing on Si ₃ N ₄ dielectric itself, the Si ₃ N ₄
In addition to having the advantages of long-term stability with excellent oxidation resistance and environment resistance characteristics such as high temperature and high humidity, the specific refractive index of the Si ₃ N ₄ dielectric layer can be increased. Thus, the reproducing performance of the magneto-optical recording medium could be improved.

(Object of the Invention) An object of the present invention is to manufacture such a magneto-optical recording element with good productivity while maintaining high quality magneto-optical recording characteristics, and an excellent dielectric material suitable for magneto-optical recording characteristics. Another object of the present invention is to provide a method of manufacturing a magneto-optical recording element capable of efficiently forming a layer by sputtering.

(Means for Achieving the Object of the Invention) According to the present invention, in a method of manufacturing a magneto-optical recording element in which a magnetic layer and a dielectric layer are formed on a substrate, a composition containing an additive component of aluminum oxide and yttrium oxide in silicon nitride. A method for manufacturing a magneto-optical recording element is provided, which comprises sputtering a target made of a material to form the dielectric layer.

In the present invention, the substrate to be the adherend of the magnetic layer may have various shapes, which will be described in detail below as an example of a disk substrate.

FIG. 1 shows a typical layer structure of a magneto-optical recording element according to the present invention, in which a magnetic layer 3 is laminated on a disk substrate 1 with a first Si ₃ N ₄ system dielectric layer 2 interposed therebetween. Furthermore, a second Si ₃ N ₄ based dielectric layer 4 is provided thereon, and a protective layer 5 is formed thereon.

On the surface of the disk substrate 1, Si ₃ N ₄ system dielectric layers 2, 4
The magnetic layer 3 can be formed by PVD (physical vapor deposition) or CVD (chemical vapor deposition), and the same thin film forming technique such as the sputtering method can be used for suitability for mass production. In order to form the Si ₃ N ₄ based dielectric layer 2 by the sputtering method, a target is a Si ₃ N ₄ sintered body containing the additive component of the present invention, or an additive component target other than the Si ₃ N ₄ target is used. The composite target used may be used, or the reactive sputtering method in the nitrogen atmosphere of the alloy target to which the Si additive is further added may be used.

In the present invention, the Si ₃ N ₄ system dielectric layer is formed by sputtering, but the magnetic layer may be formed by using other thin film forming techniques such as electron beam evaporation and chemical plating.

Next, when manufacturing the above-described magneto-optical recording element according to the present invention, various kinds of sputtering can be used. The manufacturing method using the magnetron sputtering apparatus shown in FIG. 3 will be described in detail.

In the figure, inside the vacuum chamber 6, a first target 7 made of a Si ₃ N ₄ sintered body, a second target 8 made of a magnetic alloy, and a disk shape on which a combined thin film is formed by being rotationally driven. Substrate 9 is arranged.

High frequency sputtering is performed between the first target 7 and the substrate 9, and sputtering is performed between the second target 8 and the substrate 9 by applying a high frequency voltage or a DC voltage.

Below the first and second targets 7 and 8, a planar magnetron type cathode is provided, which enhances the ionization efficiency of discharge gas molecules by utilizing the Penning effect phenomenon in which an electric field and a magnetic field are orthogonal to each other, and is suitable for mass production. Suitable high-speed film formation becomes possible.

According to the present invention, the formation of the Si ₃ N ₄ based dielectric layer and the formation of the magnetic layer are performed in an arbitrary stacking order in the above-mentioned apparatus. First,
After degassing the inside of the apparatus to a high vacuum of 1 × 10 ⁻⁵ Torr or less, an inert gas for sputtering, such as argon or nitrogen, is introduced so as to have a predetermined pressure. Atmospheric gas pressure is 1
If it is less than × 10 ^-3 Torr, a stable discharge state cannot be obtained and film formation becomes difficult, and if it exceeds 50 × 10 ^-3 Torr, argon (Ar) and oxygen (O) contained in the magnetic thin film increase. Film characteristics are deteriorated, it is difficult to achieve the object of the present invention, and it is difficult to obtain uniformity and stability.
^-3 to 50 x 10 ^-3 Torr, preferably 3 x 10 ^{-3 to} 20 x 1
It is set in the range of 0 ^-3 Torr.

In the case of the recording element shown in FIG. 1, a high frequency power is applied between the first target 7 and the substrate 9 to form a Si ₃ N ₄ system dielectric layer and a predetermined film thickness is obtained, and then sputtering is performed. Stop. Next, high frequency power or DC voltage is similarly applied between the second target 8 and the substrate 9 to form a magnetic layer, and when the predetermined thickness is reached, this sputtering is stopped and Si ₃ The N ₄ -based dielectric layer is sputtered.

According to the present invention, the following advantages are achieved by using, as the first target 7, the composite Si ₃ N ₄ sintered body in which Si ₄ N ₄ is mixed with the above-mentioned additive component.

Before the introduction of an inert gas such as argon or nitrogen, it is necessary to set the ultimate vacuum inside the apparatus within a predetermined range. If it is less than this range, residual gas in the device (water, oxygen, nitrogen, etc.) will be taken into the dielectric layer and form silicon oxynitride (Si-N-O), which reduces the refractive index. This is because n becomes close to SiO ₂ .

According to the present invention, the ultimate vacuum is 1 × 10 ⁻⁵ Torr (1.3 ×
It can be set to 10 ^-3 Pa) or less. When a high-purity Si ₃ N ₄ target containing no additive by the conventional method is used, the ultimate vacuum is required to be a high vacuum of 1 × 10 ⁻⁶ Torr or less. Can be relaxed, and as a result, the evacuation time for evacuating can be shortened, and improvement in production efficiency can be expected.

The conventional Si ₃ N ₄ target has a porosity of about 30% or more in porosity, but the target of the present invention uses a sintering aid of a silicon nitride sintered body as an additive component as described later, A Si ₃ N ₄ target having a porosity of 5% or less can be obtained, and the following effects can be obtained. In other words, the conventional target has many large pores, so there is a close
The fact that impurity gas is contained in d-shaped pores has been confirmed as a factor that prevents stable quality from being obtained.

Moreover, although cooling is required to control the temperature of the target, the conventional target cannot achieve a sufficient cooling effect due to the presence of pores. Therefore, when the substrate temperature rises significantly and a sufficiently thick protective film is formed on the plastic substrate. Had been an obstacle.

Therefore, it is obvious that the present invention is an effective means for solving the above problems.

According to the production method of the present invention, in addition to the effects described above, the following effects can be obtained.
As described in No. 79.

The Si ₃ N ₄ based dielectric layer 2 according to the present invention contains an additive component that improves the refractive index of Si ₃ N ₄ itself, that is, a refractive index improver so that the refractive index exceeds 2.15. It is important to.

Although it is considered that such additional components include various simple substances and compounds, the present inventors target a silicon nitride composition containing aluminum oxide (Al ₂ O ₃ ) and yttrium oxide (Y ₂ O ₃ ). It turned out that it is good to use.

In the present invention, as the refractive index improver, the same components as those conventionally known as sintering aids for Si ₃ N ₄ are used as the components contained in the Si ₃ N ₄ based dielectric layer. However, in the dielectric layer of the present invention, Si ₃ N ₄ is contained in a completely different state from the sintered state, that is, in general, it is contained in an amorphous state.
It was a completely unexpected finding that the refractive index of the Si ₃ N ₄ dielectric layer was improved.

Of course, in the present invention, the above-mentioned remarkable advantages can be achieved by using a sintered body of Si ₃ N ₄ as a target for forming a dielectric layer by sputtering.

A difference may be observed between the composition of the dielectric layer target used and the composition of the dielectric layer actually formed. In general, the content the Si ₃ N ₄ dielectric layer has a high tendency is observed than the content the Si ₃ N ₄ in the target.

However, if Al ₂ O ₃ is less than 0.03 in the Si ₃ N ₄ -based dielectric layer.
1 to 5 mol%, preferably 0.5 to 1 mol%, and Y ₂ O
_{When 3} is contained in an amount of 0.1 to 3 mol%, preferably 0.2 to 0.5 mol%, satisfactory results can be obtained in terms of refractive index. On the other hand, the target composition contains Al ₂ O _{3 in an amount} of 4 to 10 mol%, preferably 7 to 9 mol%, and Y ₂ O _{3 in an amount} of 0.5 to 10 mol%, preferably 1 to 3 mol%. Is good.

The Si ₃ N ₄ -based dielectric layer according to the present invention essentially includes the above-mentioned additional components, but does not exclude the inclusion of other components unless the effects of the additional components are lost. Absent. For example, it does not matter that a small amount of SiO ₂ , WC, etc. is contained.

Regarding the content of the target additive component according to the present invention, as a result of repeating various experiments, the maximum refractive index of the Si ₃ N ₄ system dielectric layer is related to the optical constant of the magnetic layer and the substrate material. It is desirable that it is determined within a range where the reflectance does not drop too much and the amount of focusing light at the time of disk rotation is sufficiently taken. When PC resin, PMMA resin and glass are used for the substrate, the respective refractive indexes are 1.59. , 1.5
Since it is 1.5 and 1.5, it is preferable that the refractive index be practically increased within a range not exceeding 3.5.

Further, when the refractive index of the Si ₃ N ₄ system dielectric layer is increased, the enhancement effect is improved and the layer thickness t is reduced based on the equation t = λ4n · (2m + 1) for obtaining the enhancement effect. can do. As a result, it is possible to reduce the film formation time of the layer by several tens of percent, and to reduce the variation in the enhancement effect due to the non-uniformity of the layer thickness distribution on the substrate.

Further, according to the present invention, when Si ₃ N ₄ is contained as a main component in the target for Si ₃ N ₄ based dielectric layer in an amount of 80 mol% or more, a dense and pinhole-free film is formed. Even if the dielectric layer is placed in a high-humidity environment, no deterioration phenomenon such as oxidation will occur in the dielectric layer, and the excellent environment resistance characteristic of Si ₃ N ₄ can be maintained.

In the magneto-optical recording element of the present invention, an amorphous metal perpendicular magnetization film, such as TbFe, is used as a magnetic layer 3 on a glass substrate or a plastic substrate via the Si ₃ N ₄ system dielectric layer 2 as described above.
GdCo, TbFeCo, DyFeCo, GdTbFeCo, GdDy
It is preferable to form FeCo and the like, and further to form a second Si ₃ N ₄ based dielectric protective layer 4 thereon in order to prevent oxidation of the magnetic layer 3 and the like. This protective layer 4 is also preferably made of the Si ₃ N ₄ system dielectric layer according to the present invention, whereby the same common target can be used.

In the magneto-optical recording element of the present invention, in order to effectively improve the magneto-optical characteristics, the substrate 1 and the Si ₃ N ₄ -based dielectric layer 2 are interposed between the dielectric layer 2 and the magnetic layer 3. There is no problem even if layers are provided.

In the recording element of the present invention, a resin protective layer 5 can be further formed on the second dielectric layer 4 if necessary. As the resin protective layer 5, a UV-curable acrylic resin, polyester resin, acrylic urethane resin or the like known per se can be used.

As shown in FIG. 2, the second dielectric layer 4 in FIG.
Alternatively, the ultraviolet curable resin protective layer 5 may be provided directly on the surface of the magnetic layer 3.

(Example) Next, the Example of this invention is described.

(Example 1) With a high frequency binary magnetron sputtering device,
A mixture of Al ₂ O ₃ and Y ₂ O ₃ added to a 9.9% pure Si ₃ N ₄ raw material was molded, sintered and processed into a thickness of 6 inches × 5 mm to obtain a composite Si ₃ N ₄ target. Disk substrate 1
A glass substrate, a DC substrate, or a PMMA substrate is provided as a substrate, and after sufficiently evacuating to 5 × 10 ⁻⁶ Torr, Ar gas having a purity of 99.999% is introduced and 5 × 10 5
^-3 Torr. Then, after applying a power of 50 W to the substrate 1 for etching, pre-sputtering was performed on the substrate 1 at an RF power of 1 kW for 5 minutes, and then a Si ₃ N ₄ based dielectric layer 2 was formed. The thickness of the Si ₃ N ₄ system dielectric layer 2 thus formed is λ / 4n (where λ is the wavelength of the reproducing laser beam, and in this embodiment, 8000Å, and n
Is the refractive index of the Si ₃ N ₄ system dielectric layer 2). After that, pre-sputtering was performed for 60 minutes at an RF power of 200 W, and the same DyFeCo layer was formed in each element with a film thickness of about 1500 Å.

Further, a Si ₃ N ₄ based protective layer 4 was coated on the magnetic layer 3 under the same manufacturing conditions as the Si ₃ N ₄ based dielectric layer 2.

The target for the Si ₃ N ₄ system dielectric layer 2 and the Si ₃ N ₄ system protective layer was Si ₃ N ₄ (90 mol%) by fluorescent X-ray analysis.
-Al ₂ O ₃ (6 mol%) - it was found to be Y ₂ O ₃ (4 mol%).

The magneto-optical recording element of the present invention thus obtained was tested for reproduction performance index and environmental resistance.

(1) Reproduction performance index test Reproducing laser light (wavelength 8000Å) for magneto-optical recording element laminated on glass substrate (refractive index 1.5)
Is projected from the substrate side, force-rotation angle θK, reflectance R
Measure the playback performance index I asked.

The results are shown in Table 1.

In Table 1, as a comparative example, Si ₃ N ₄ containing no added components was used.
A magneto-optical recording element manufactured by forming the system dielectric layer and the Si ₃ N ₄ system protective layer under the same conditions as in the present embodiment, and otherwise making the same as in the present embodiment is described.

In addition, the second to display the enhancement effect numerically.
As shown in the figure, the above-mentioned Si ₃ N ₄ system protective layer 4 is absent, and the others are completely the same Si ₃ N ₄ system dielectric layer 2 and magnetic layer 3,
A magneto-optical recording element in which the protective layer 5 was not formed was manufactured in addition to this example, and a reproducing laser beam (wavelength 8000Å) was projected from the magnetic layer side of this element to obtain the reproduction index η ′ inherent to the magnetic layer. It was Then, in the comparative example, the enhancement effect was similarly obtained.

According to Table 1, in the device of this example, the enhancement effect becomes larger as the refractive index of the dielectric layer becomes larger than that of the comparative example, and the reproducing performance index is about 12.
You can see that it has become bigger.

(ii) Environmental resistance test A magneto-optical recording element laminated on a glass substrate,
It was installed in a high temperature and high humidity atmosphere of 65 ° C. and 90 to 95% relative humidity, and changes over time of the Kerr rotation angle and coercive force immediately after production were traced. As shown in FIGS. 4 and 5, respectively. The result was. These results were obtained from a Kerr hysteresis loop using a Kerr effect measuring device manufactured by JASCO Corporation, and the wavelength of this reproducing laser beam was 6328.
It is Å.

In FIG. 4, the Kerr rotation angle θkr with respect to the elapsed time t
The ratio between (t) and the Kerr rotation angle θkr (0) is shown, where θkr (0) is the value immediately after fabrication. However, θkr represents the residual Kerr rotation. The mark ● is the plot of this embodiment, and (a) is its time-dependent characteristic curve. ▲ indicates Si ₃ N with no added ingredients
₄ is a plot in the case where a ₄ system dielectric layer and a Si ₃ N ₄ system protective layer were formed under the same conditions as in this example, and the other comparative element manufactured in exactly the same manner as this example was used. , (B)
Is the time-dependent characteristic curve.

The device of the present invention shows almost no change after 500 hours compared with the comparative example, and the Si ₃ N ₄ based dielectric layer uses the magnetic thin film for magneto-optical recording as a protective layer similarly to the conventionally known Si ₃ N ₄ protective layer. It has excellent performance.

FIG. 5 shows the ratio of the coercive force Hc (t) and the coercive force Hc (0) with respect to the elapsed time t, where Hc (0) is the value immediately after fabrication. In the figure, ● marks are plots of this embodiment, and (C) is a time-dependent characteristic curve thereof. The symbol ▴ is a plot of the element of the comparative example described above, and (d) is its time-dependent characteristic curve.

According to FIG. 5, the device of the present invention is similar to the result of FIG.
Even after 500 hours, it has excellent performance as well as the well-known Si ₃ N ₄ layer.

In the present invention, the film formation rate could be increased with the same amount of electric power, and the substrate temperature during the film formation could be decreased, as compared with the comparative example. Such low-temperature and high-speed film formation technology is a particularly important technology when using a plastic substrate with a low heat distortion temperature, and is achieved by preventing the incidence of secondary electrons on the substrate and reducing the thermal radiation of the target as much as possible. it can. According to the example, high power efficiency (film formation speed / input power) is effective for low-temperature film formation, and high-speed film formation is possible at a low substrate temperature so as not to have a thermal effect on the plastic substrate. Naru Si ₃ N ₄
A dielectric layer can be provided. The substrate temperature was set to a film thickness at which an enhancement effect was obtained and compared.

Example 2 In this example, the composition of the composite Si ₃ N ₄ target (porosity 2%) in Example 1 was Si ₃ N ₄ (89.2 mol%)-Al ₂ O ₃ (8.7). Mol%)-Y ₂ O ₃ (2.1 mol%) and changing the ultimate vacuum before sputtering from 5 × 10 ^{−7 to} 1.5 × 10 ⁻⁵ Torr under other conditions. In the same manner as in Example 1, a Si ₃ N ₄ based dielectric layer was formed on the substrate. As a comparative example, Si ₃ N ₄ having a purity of 99.9%
The same experiment was conducted using a sintered body (porosity 28%) as a target.

The result is shown in FIG.

(E) is the Si ₃ N ₄ system dielectric layer manufactured in this example,
(F) is a comparative example.

As is clear from the figure, the ultimate vacuum is 1 according to the present invention.
It can be seen that the value is set to × 10 ^-5 Torr or less.

When the ultimate vacuum was poor, it was found from the measurement results of the quadrupole mass spectrometer that the main component of the residual gas was water.

(Effect of the Invention) As described above, according to the magneto-optical recording element of the present invention, when the Si ₃ N ₄ system dielectric layer having excellent oxidation resistance to the magnetic layer is used, the resistance against high temperature and high humidity is increased. There is provided a magneto-optical recording element having a high refractive index while maintaining the characteristics, resulting in an improved reproducing performance index and improved adhesion.

Further, in the manufacturing method of the present invention, S suitable for magneto-optical recording characteristics is used.
The i ₃ N ₄ -based dielectric layer can be efficiently formed by sputtering, and improvement in manufacturing yield and productivity can be expected.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a layer structure of a typical example of a magneto-optical recording element according to the present invention, FIG. 2 is a cross-sectional view of a magneto-optical recording element having a different layer structure, and FIG. 3 is used in an embodiment of the present invention. FIG. 4 is a schematic diagram of a magnetron sputtering apparatus to be used, and FIG. 4 is a diagram showing a time-dependent characteristic of the ratio of the Kerr rotation angle θkr (t) and the Kerr rotation angle θkr (0) in the magneto-optical recording element according to the present invention. FIG. 5 is a diagram showing the time-dependent characteristics of the ratio of the coercive force Hc (t) and the coercive force Hc (0) in the magneto-optical recording element according to the present invention, and FIG. 6 is a Si ₃ N ₄ system dielectric. FIG. 4 is a diagram showing the ultimate vacuum degree-dependent characteristics in the refractive index of the body layer. 1 ... Disk substrate, 2, 4 ... Si ₃ N ₄ system dielectric layer, 3 ... Magnetic layer, 5 ... Protective layer.

Claims (1)

[Claims] 1. A method of manufacturing a magneto-optical recording element in which a magnetic layer and a dielectric layer are formed on a substrate, the target comprising a composition containing silicon oxide and an additive component of aluminum oxide and yttrium oxide is sputtered to form the dielectric layer. A method of manufacturing a magneto-optical recording element, which comprises forming a body layer.