JP2511230B2 - Optical memory device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical memory device for recording, reproducing and erasing information by using light such as a laser.

[0002]

2. Description of the Related Art In recent years, various researches and developments have been carried out in various fields because optical memory elements have become high-density and large-capacity memories.

In particular, a memory in which a user can additionally record information or a memory in which a user can additionally record and erase information has a wide range of application fields and various materials and systems have been announced.

The former materials include TeOx, TeSe,
TeC and the like, and the latter materials include GdTbFe and G
There are dTbDyFe, TbFe and the like.

However, most of the basic storage materials of the memory capable of additionally recording the information or the memory capable of additionally recording and erasing the information lack corrosion resistance such as oxidation. It has been devised.

Next, the structure of a conventional optical memory device will be described.

FIG. 2 shows a spacer 3 between two substrates 1 and 2.
To provide a space 4 and fill it with an inert gas,
This is an optical memory element having a sandwich structure in which a recording layer 5 is provided on the inner surfaces of the two substrates 1 and 2 (see Japanese Patent Publication No. 57-32413). The optical memory element having this structure prevents the oxidation by sealing the recording layer.

Further, FIG. 3 shows an optical memory device in which a recording layer 7 is sandwiched by a transparent film 8 which is stable against oxidation on a substrate 6, and a film 9 which is easily oxidized is further coated thereon (Japanese Patent Application No. 57-149).
806). The optical memory element having this structure is designed to prevent oxygen from reaching the recording layer by absorbing oxygen with a film that is easily oxidized.

[0009]

However, all of the above optical memory elements are effective structures for avoiding the entry of corrosive substances such as oxygen from the outside. Has no effect.

However, in some optical memory devices, oxygen and the like are mixed in when the devices are formed.

Next, the problem of oxidation of a magneto-optical storage element, which is an optical memory element that allows a user to additionally record and erase information, will be described.

The present inventor investigated a magneto-optical storage element formed by sequentially sputtering GdTbFe, SiO ₂ and Cu on a glass substrate.

FIG. 4 shows the magneto-optical storage element.

10 is a glass substrate, 11 is a film thickness of 100Å ~
GdTbFe film of 200Å, 12 is 300Å to 40４０
0 ° SiO ₂ film, 13 is a C film having a thickness of 300-500 ° C.
It is a u film.

FIG. 5 shows the change over time in the coercive force when this magneto-optical storage element is stored at 70 ° C.

According to FIG. 1, it can be seen that the coercive force Hc after 400 to 500 hours has changed to less than half of the initial coercive force Hco. This tendency is more remarkable as the thickness of the GdTbFe film is smaller and the storage temperature is higher.

On the other hand, when the magneto-optical storage element at the time of formation by the above-described manufacturing method was analyzed by Auger electron spectroscopy, FIG.
Can be obtained.

The results shown in FIG. 1 show that the GdTbFe film and the SiO
_It shows Auger electron intensities for Si, Fe, and O in the two-layer film and the two-layer film.

As shown in the figure, the oxygen content increases from the surface of the two-layer film to the glass substrate, and the GdT
It can be seen that much oxygen is mixed in the bFe film. It is considered that this is because oxygen separated from SiO ₂ was taken into the GdTbFe film during the sputtering when the device was formed. That is, GdTb has already been formed at the time of element formation.
The Fe film has been oxidized.

An object of the present invention is to provide a novel optical memory device capable of avoiding oxygen mixed in at the time of forming the optical memory device as described above.

[0021]

In order to achieve the above object, the present invention provides a substrate, a recording medium comprising a rare earth transition metal alloy thin film formed on the substrate, and a Cu formed on the recording medium. , Ag, Al, or Au, the oxygen from the substrate side during the film formation of the recording medium formed of the rare earth-transition metal alloy thin film between the substrate and the recording medium. An optical memory device is provided with a transparent dielectric film made of aluminum nitride having a thickness of 100 Å or more for preventing the invasion of the.

As the transparent dielectric film, instead of aluminum nitride, MgF ₂ , ZnS, CeF ₃ , AlF ₃ ,
3NaF or the like can also be used.

[0023]

According to the present invention, a highly reliable optical memory device can be obtained.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical memory device according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram of an optical memory device for explaining an embodiment of a method for manufacturing an optical memory device according to the present invention.

Reference numeral 14 is a transparent substrate made of glass, polycarbonate, acrylic, or the like. On the transparent substrate 14, a transparent Al nitride film 15 which is a first transparent dielectric film is formed. Rare earth transition metal alloy thin films (eg GdTbFe, TbDyFe, GdTbDyFe, Tb)
Fe, GdFeCo, GdCo or S in them
n, Zn, Si, Bi, B, etc.)
Is formed on the rare earth transition metal alloy thin film 16, a transparent Al nitride film 17 as a second transparent dielectric film is formed, and Cu, Ag, Al, Au is formed on the Al nitride film 17.
And the like.

Auger electron spectroscopic analysis of the magneto-optical storage element having this structure yields the results shown in FIG. The results shown in the figure show that the Al nitride film and GdTb
Al, Fe, in a three-layer film of an Fe film and an Al nitride film
The Auger electron intensity for O is shown. As shown in the figure, no oxygen is contained in the GdTbFe film,
Slight oxidation is observed at the interface between the surface and the Al nitride film and at the interface between the Al nitride film and the transparent substrate. This is after film formation
This indicates that there is oxygen that has entered the Al nitride film from the outside and oxygen that has entered the Al nitride film from the glass substrate.

As can be judged from the results of this experiment, the structure in which the rare earth-transition metal alloy thin film 16 is sandwiched by the Al nitride films can prevent the rare earth-transition metal alloy thin film 16 from being oxidized during the film formation. Is. This is because Si
Unlike an O ₂ film, an Al nitride film does not contain oxygen. For example, if a film is formed by reactive sputtering in a nitrogen atmosphere using an Al target, oxygen is added to the rare earth transition metal alloy thin film during the film formation. There is no danger of intrusion. In view of this point, a rare-earth transition metal alloy thin film is converted into another oxygen-free transparent dielectric film (for example, Mg).
F ₂ , ZnS, CeF ₃ , AlF ₃ , 3NaF). However, since the other transparent dielectric films described above have many porous dielectric film targets and are porous, oxygen and moisture trapped in the pores may be released during sputtering to oxidize the rare earth transition metal alloy thin film. It is relatively difficult to produce a rare earth transition metal alloy thin film that does not really contain oxygen. On the other hand, in the case of an Al nitride film, since the target is only Al, the target can be saved. Further, since the Al target is not porous, there is no possibility of taking in oxygen or moisture into the pores. From this point, Si ₃ N _{4 is} formed by reactive sputtering in a nitrogen atmosphere using a Si target.
May be a transparent dielectric film.

Here, the film thickness of the first transparent dielectric film of the optical memory element must be at least 100Å. The reason is that, for example, when the first transparent dielectric film is formed on the glass substrate, the depth in which oxygen in the glass substrate is mixed into the transparent dielectric film is about 50Å. When the film thickness of the transparent dielectric film is 100 Å or less, oxygen may enter the rare earth transition metal alloy thin film when the rare earth transition metal alloy thin film is sputtered on the first transparent dielectric film. . The second transparent dielectric film is mainly provided to increase the magneto-optical rotation angle and improve the quality of the reproduced signal. However, when the quality of the reproduced signal is sufficient, it is omitted and the rare earth transition metal alloy is omitted. A reflective film of Cu, Ag, Al, Au or the like may be directly formed on the thin film 16.

Incidentally, Ti, Mg rare earth metals (Gd, Tb, D) are formed on the reflection film 18 of the optical memory device having the structure shown in FIG.
y, Ho, Y, etc.), rare earth transition metal alloys (GdTbF
e, TbDyFe, GdCo, GdTbDyFe, etc.) provides a perfect element structure capable of preventing oxygen from entering from the outside by coating a film made of an easily oxidizable metal such as e.g.

[0031]

According to the present invention described above, a substrate, a transparent dielectric film made of aluminum nitride, a recording medium made of a rare earth-transition metal alloy thin film, and a reflective film made of Cu, Ag, Al or Au. Since the above structure is provided in this order, the reliability of the memory element is greatly improved.

When aluminum nitride is formed as a transparent dielectric film by using aluminum as a target material during film formation, aluminum is a metal and has higher conductivity than a material such as silicon, so that reactive sputtering is performed. The speed of can be greatly increased. A major drawback of the film formation method by sputtering is that the film formation rate is slower than the film formation method by vapor deposition, and as a result, productivity was poor. Can be greatly improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical memory device according to the present invention.

FIG. 2 is a configuration diagram of a conventional optical memory device.

FIG. 3 is a configuration diagram of a conventional optical memory element.

FIG. 4 is a configuration diagram of a conventional optical memory element.

FIG. 5 is a diagram showing changes in coercive force of a conventional optical memory element over time.

FIG. 6 is a diagram showing a result of Auger electron spectroscopy analysis of a conventional optical memory element.

FIG. 7 is a diagram showing a result of Auger electron spectroscopy analysis of the optical memory device according to the present invention.

[Explanation of symbols]

1, substrate 3 spacer 4 space 5 recording layer 6 substrate 7 recording layer 8 transparent film 9 easily oxidizable film 10 glass substrate 11 GDTbFe film 12 SiO ₂ 13 Cu film 14 transparent substrate 15 first transparent dielectric film 16 rare earth transition Metal alloy thin film 17 Second transparent dielectric film 18 Reflective film

Front Page Continuation (72) Inventor Hiroyuki Katayama 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Prefecture Sharp Corporation (72) Hideka Yamaoka 22-22 Nagaike-cho, Abeno-ku, Osaka City, Osaka Prefecture Sharp ( 56) References JP-A-57-169996 (JP, A)

Claims (1)

(57) [Claims] 1. A substrate, a recording medium made of a rare earth transition metal alloy thin film formed on the substrate, and a reflective film made of any one of Cu, Ag, Al and Au formed on the recording medium. In the optical memory device having the above, a nitride film having a thickness of 100 Å or more is provided between the substrate and the recording medium to prevent oxygen from entering from the substrate side during film formation of the recording medium made of the rare earth-transition metal alloy thin film. An optical memory device comprising a transparent dielectric film made of aluminum.