JPH0524571B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field of the Invention> The present invention relates to a method for manufacturing a magneto-optical memory element in which information is recorded, reproduced, erased, etc. by irradiation with light such as a laser.

<Technical background of the invention and its problems> In recent years, magneto-optical storage elements have been actively developed as optical memory elements capable of recording, reproducing, and erasing information.

Among these, those using rare earth transition metal amorphous alloy thin films as storage media have the advantage that recording bits are not affected by grain boundaries and that it is relatively easy to create a recording medium film over a large area. has attracted particular attention.

However, when a magneto-optical recording element is constructed using the above-mentioned rare earth transition metal amorphous alloy film as a recording medium, it is generally not possible to obtain sufficient magneto-optical effects (Kerr effect, Faraday effect). Therefore, the S/N ratio of the reproduced signal was insufficient.

In order to improve such problems, as shown in Japanese Patent Application Laid-Open No. 57-12428,
An element structure called a reflective film structure is employed in magneto-optic memory elements.

FIG. 2 is a partial side sectional view of a conventional magneto-optical memory element having a reflective film structure.

In Fig. 2, 1 is a transparent substrate, 2 is a transparent wood dielectric film having a higher refractive index than the transparent substrate 1, 3 is an amorphous alloy thin film made of rare earth transition metal, and 4 is a transparent dielectric film. Body membrane 5 is a metal reflective membrane. In the magneto-optical memory element of this structure, the amorphous alloy thin film 3 is sufficiently thin, so that a portion of the light incident on the amorphous alloy thin film 3 passes through. Therefore, the reproduced light is caused by the Kerr effect caused by reflection on the surface of the amorphous alloy thin film 3, as well as by passing through the amorphous alloy thin film 3, being reflected by the metal reflective film 5, and passing through the amorphous alloy thin film 3 again. By combining the Faraday effects, the Kerr rotation angle appears to increase several times compared to an element based only on the Kerr effect.

Note that the transparent dielectric film 2 on the amorphous alloy thin film 3 also functions to increase the Kerr rotation angle.

As an example, in FIG. 2, the transparent substrate 1 is a glass plate, the transparent dielectric film 2 is 120 nm SiO,
The amorphous alloy thin film 3 is made of 15 nm GdTdFe, and the transparent dielectric film 4 is made of 50 nm SiO ₂ . metal reflective film 5
In the configuration with 50 nm of Cu, the apparent Kerr rotation angle increased to 17.5 degrees.

The reason why the Kerr rotation angle increases significantly by employing the above element structure will be explained next.

As shown in FIG. 2, a laser beam L is emitted from the transparent substrate 1.
When the amorphous alloy thin film 3 is irradiated with , the incident laser light L is repeatedly reflected inside the transparent dielectric film 2,
As a result of the interference, the apparent Kerr rotation angle increases, and in this case, the larger the refractive index of the transparent dielectric film 2, the greater the effect of increasing the Kerr rotation angle.

In addition, as shown in FIG. 2, the arrangement of the reflective film 5 on the back surface of the amorphous alloy thin film 3 increases the apparent Kerr rotation angle, and the difference between the amorphous alloy thin film 3 and the reflective film 5 increases. By interposing the transparent dielectric film 4 between them, the apparent Kerr rotation angle is further increased.

Next, the principle of this action will be qualitatively explained.

Considering the composite film of the transparent dielectric film 4 and the reflective film 5 as one reflective layer A, in FIG.
The light enters from the transparent substrate 1 side, passes through the amorphous alloy thin film 3, is reflected by the reflective layer A, and then passes through the amorphous alloy thin film 3 again, and the light enters from the transparent substrate 1 side. The light reflected on the surface of the amorphous alloy thin film 3 is combined, but in this case, the Kerr effect caused by the reflection of the incident light L on the surface of the amorphous alloy thin film 3 and the incident light L When combined with the Faraday effect caused by passing through the inside of the amorphous alloy thin film 3, the apparent Kerr rotation angle increases.

In a magneto-optical memory element having such a structure, it is extremely important how the Faraday effect is added to the Kerr effect.

Regarding the Faraday effect, the rotation angle can be increased by increasing the layer thickness of the amorphous alloy thin film 3, but the incident laser beam L
As a result, the intended purpose cannot be achieved.
Therefore, the appropriate layer thickness of the amorphous alloy thin film 3 is approximately 10 to 50 nm, and the value is determined by the wavelength of the laser beam L used, the refractive index of the reflective layer A, and the like.

As is clear from the above description, the condition required for the reflective layer A is that the reflectance be high.

As described above, the transparent substrate 1 and the amorphous alloy thin film 3
By adding the structure of the reflective layer A on the back surface of the transparent dielectric film 2 and the amorphous alloy thin film 3 interposed between the two, it is possible to obtain the effect of increasing the Kerr rotation angle.

As is clear from the above description, the requirement for the metal reflective film 5 is that it has a high reflectance. Materials that meet this condition include Au, Ag,
Examples include Cu and Al.

In general, magneto-optical memory elements are often fabricated by the sputtering method due to ease of fabrication.
Materials such as Ag are extremely difficult to obtain as targets. In addition, the target of Cu is easy to obtain,
Since it is a material that can be sputtered easily, it is easy to form a film, but there is a problem in that it lacks the necessary corrosion resistance in terms of long-term reliability of magneto-optic storage elements. Further, although Al is easily available as a target and has excellent corrosion resistance as described above, it has the disadvantage that it is difficult to form a film with high reflectance.

The reason why it is difficult to form a film with high reflectivity when forming an Al reflective film by sputtering is that white turbidity occurs during film formation by sputtering, and this clouding causes The reflectance of the metal reflective film decreases,
Undesirable. The main cause of this cloudiness is, firstly, a small amount of H, which is present during film formation.
This is due to contaminants such as C, O ₂ , N ₂ , H ₂ , H ₂ O, etc., and the second is due to an increase in the substrate temperature of the magneto-optic memory element due to film formation.

Therefore, in order to obtain an aluminum reflective film that does not become cloudy and has a high reflectance, the above-mentioned H, C, O ₂ , N ₂ ,
It is necessary to prevent the contamination of H ₂ , H ₂ O, etc., and to prevent the substrate temperature of the magneto-optic memory element from rising, but to achieve this, the sputtering conditions are severely limited. This is extremely difficult.

<Object and structure of the invention> Therefore, the present invention has been made in view of the above points, and is a novel magneto-optical method capable of preventing clouding of an aluminum (Al) reflective film formed by sputtering. An object of the present invention is to provide a method for manufacturing a memory element. To achieve this object, the present invention provides a method for manufacturing a magneto-optical storage element having a recording layer having a multilayer structure including an aluminum reflective film layer, in which a target used when forming the aluminum reflective film layer by sputtering is provided. This method of manufacturing a magneto-optical memory element is characterized by using a target to which nickel, which is an element for preventing clouding occurring in the aluminum reflective film layer, is added.

<Embodiment of the Invention> Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a partial side sectional view showing the structure of a magneto-optic memory element having an aluminum/nickel reflective film obtained by adding nickel to aluminum as an embodiment of the magneto-optic memory element according to the present invention.

In FIG. 1, 1 is a transparent substrate made of glass, polycarbonate, acrylic, etc.
A transparent aluminum nitride (AlN) film 6, which is a first transparent dielectric film, is formed on the aluminum nitride (AlN) film 6 to have a thickness of, for example, 100 nm, and a GdTbFe alloy thin film 3, which is a rare earth transition metal alloy thin film, is formed on the aluminum nitride (AlN) film 6. is formed to have a thickness of 27 nm, for example, and a transparent aluminum nitride (AlN) film 7, which is a second transparent dielectric film, is formed to have a thickness of 35 nm, for example, on the GdTbFe alloy thin film 3, and further on the aluminum nitride film 7. As a reflective film, aluminum (Al) and nickel (Ni) are used as reflective films.
An aluminum/nickel film 8 obtained by sputtering a target doped with is formed to have a thickness of 60 nm or more, for example.

In this way, when the reflective film 8 is formed of aluminum/nickel, there are the following advantages.

That is, when the transparent dielectric film 7 is formed of aluminum nitride (AlN) as described above, a conventional reflective film such as aluminum (Al) is applied thereon with a high reflectance in the laser wavelength range (800 nm). Deposition by sputtering was very difficult as it caused clouding. This clouding is thought to be because the influence of the nitrogen component in aluminum nitride (AlN) on Cu and Al cannot be ignored.

On the other hand, the reflective film 8 made of aluminum/nickel can be easily applied to the transparent dielectric film 7 made of aluminum nitride in a state where the reflectance is high in the laser wavelength range, that is, in a state where no clouding occurs.

As a result, the amount of light reflected by the magneto-optical storage element can be increased, and the reproduced signal can be improved. The aluminum-nickel film 8 also has excellent corrosion resistance and can contribute to the corrosion resistance of the recording medium (recording layer).

<Effects of the Invention> As described above, according to the manufacturing method for a magneto-optical memory element according to the present invention, clouding of the aluminum reflective film formed by sputtering can be prevented, so that a reflective film having high reflectance can be obtained. As a result, it is possible to provide a magneto-optical storage element with significantly improved information reproducing characteristics.

[Brief explanation of drawings]

FIG. 1 is a partial side cross-sectional view showing the structure of an embodiment of a magneto-optic memory element according to the present invention, and FIG. 2 is a partial side cross-sectional view showing the structure of a conventional magneto-optic memory element. DESCRIPTION OF SYMBOLS 1... Transparent substrate, 3... Rare earth transition metal alloy thin film, 6... First transparent dielectric film (AlN film), 7...
...Second transparent dielectric film (AlN film), 8...Metal reflective film (AlNi reflective film).

Claims (1)

[Scope of Claims] 1. In a method for manufacturing a magneto-optical storage element having a recording layer having a multilayer structure including an aluminum reflective film layer, the target used when forming the aluminum reflective film layer by sputtering comprises: 1. A method for manufacturing a magneto-optical memory element, characterized by using a target doped with nickel, an element for preventing cloudiness occurring in a reflective film layer.