JPH05144107A - Magmeto-optical memory element - Google Patents

Abstract

PURPOSE:To enable to make a first layer AlN thin, since two layers of a first layer of tin oxide and a first layer of AlN have a function to reduce a reflectance of GdTbFe and to shorten the totally required time for a film formation of a magneto-optical disk, since a sputtering ratio of the tin oxide is larger than that of AlN. CONSTITUTION:On a PC substrate 11, the first layer of tin oxide 12 (900Angstrom ), the first layer of AlN 13 (10nm), GdTbFe 14 (35nm), the second layer of AlN 15 (10nm), the second layer of tin oxide 16 (11nm) and an Al reflective film 17 (40nm) are formed in this order.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical memory element capable of perpendicular magnetic recording, and more particularly to a film structure of a magneto-optical memory element capable of shortening a film formation time required by a sputtering method.

[0002]

2. Description of the Related Art A magneto-optical storage element capable of perpendicular magnetic recording such as a so-called magneto-optical disk has been developed in response to an increasing demand for high-density recording in fields such as data files and external memories of computers. There is.

Amorphous alloy thin films of rare earth metals (RE) and transition metals (TM) have characteristics such as high recording sensitivity, no grain boundary noise, and easy film production. Promising as a recording medium.

FIG. 4 shows an example of a film structure of a magneto-optical disk at a practical level (Journal of Japan Applied Magnetics Vol.8,
No.2, 1984 p.93). The magneto-optical disk 50 is, for example,
PC (polycarbonate) substrate 51 / first AlN52 (1
0 nm) / GdTbFe53 (35 nm) / second AlN54
It has a multilayer film structure of (21 nm) / Al55 (40 nm).

The first AlN 52 has the functions of protecting GdTbFe53 and serving as an antireflection film for reducing the reflectance of GdTbFe53. Al55 is a reflective film, and the second AlN54 has a function of increasing the reflectance of Al55. Such a multilayer film structure can increase the Kerr rotation angle, which is small when the RE-TM amorphous alloy thin film is used alone, to an effective level by the enhancing effect of multiple reflection.

There is an optimum range for each film thickness.
A range of 80 to 110 nm is selected for the film thickness of the first AlN 52, and a range of 20 to 40 nm is selected for the film thickness of the second AlN 54.

These films are manufactured by using the sputtering method. AlN has the slowest deposition rate of 40 nm
/ Min, GdTbFe and Al are both 100 nm / min. For example, the required time for forming the film with the above-mentioned film thickness is 2.5 minutes for the first AlN52 and 0.5 minutes for the GdTbFe53.
35 minutes, 2nd AlN54 is 0.525 minutes, Al55 is 0.4
It will take 3.7 minutes.

An in-line sputtering apparatus as schematically shown in FIG. 5 is used as a mass production apparatus in the magneto-optical disk film forming process. In this apparatus, in the vacuum chamber 31, from the upstream side of the line, a preliminary chamber 35 in which rough vacuum evacuation is performed, a first AlN sputtering chamber 36, G
dTbFe sputtering chamber 37, second AlN sputtering chamber 3
8 and an Al sputtering chamber 39 are sequentially provided, and each chamber 3
A buffer chamber 34 is provided between 6 and 39 to make each sputtering process independent.

In the film forming process, a plurality of disc-shaped PC substrates 33 attached to the tray 32 are provided in the chambers 35 to 3 respectively.
9, and the targets in the chambers 36 to 39 are discharged one after another. In this system, each film 52-5
It is necessary that the film forming times of 5 are equal. Therefore, it is usual to adjust the film forming times to be equal by weakening the power applied to the targets of other film forming processes in accordance with the film forming process that takes the longest time.

Therefore, in the case of the magneto-optical disk 50 having the above film structure, the film forming time of the first AlN 52 determines the time of the whole film forming process, in other words, the productivity.

[0011]

However, as described above, the film forming time of the first AlN 52 is much slower than the film forming times of the other films 53 to 55. Therefore, the first AlN5
No. 2 prevents mass production of the magneto-optical disk 50 at a higher speed.

As a solution to this problem, it is conceivable to replace the AlN film with a transparent dielectric film having a high sputtering rate. However, the transparent dielectric material generally has a low sputtering rate, which is about the same as AlN.

On the other hand, as a transparent film having a high sputtering rate, there is conductive tin oxide. However, since tin oxide is an oxide, oxygen is liberated when a RE-TM amorphous alloy thin film is formed on tin oxide. Since the liberated oxygen enters the RE-TM amorphous alloy thin film, selective oxidation of the rare earth metal occurs and deteriorates the magnetic characteristics of the RE-TM amorphous alloy thin film. For example, the above-mentioned publicly known material includes Si
As a result of an environment resistance test in which the medium using the O ₂ film was left in the air at 80 ° C. for a long time, it was reported that the perpendicular magnetization finally disappeared.

As described above, the magneto-optical storage element in which AlN is simply replaced with tin oxide cannot maintain reliability as a recording medium for a long period of time.

[0015]

In order to solve the above-mentioned problems, a magneto-optical storage element according to the invention of claim 1 is provided with a first transparent dielectric film (for example, a polycarbonate substrate) on a transparent substrate (for example, a polycarbonate substrate). , AlN), perpendicular magnetization film (eg G
dTbFe), a second transparent dielectric film (for example, AlN),
In a magneto-optical storage element in which a reflective film (for example, Al) is formed in this order, at least a part of the first transparent dielectric film on the transparent substrate side has a sputtering rate higher than that of the first transparent dielectric film. It is characterized in that it is replaced with a transparent conductive film (for example, tin oxide) to shorten the film formation time required for the magneto-optical storage element.

In order to solve the above problems, a magneto-optical storage element according to a second aspect of the present invention is a transparent substrate (for example,
Tin oxide, first layer aluminum nitride, rare earth transition metal amorphous alloy film (for example, Gd) on a polycarbonate substrate)
TbFe), a second layer of aluminum nitride, and an aluminum reflection film are formed in this order to shorten the time required for forming the magneto-optical storage element.

[0017]

According to the structure of claim 1, since at least a part of the first transparent dielectric film on the transparent substrate side is replaced with the transparent conductive film, the first transparent dielectric film for reducing the reflectance of the perpendicular magnetization film is formed. The first transparent dielectric film can be thinned without impairing its function. Moreover, since the sputter rate of the transparent conductive film is higher than the sputter rate of the first transparent dielectric film, the time required for film formation can be shortened.

When the transparent conductive film is formed of an oxide, the transparent conductive film and the first transparent substrate are formed so that free oxygen generated by sputtering does not oxidize the perpendicular magnetization film. It is essential to provide it between the dielectric film.

According to the second aspect of the present invention, the tin oxide layer having a sputtering rate higher than that of the first layer aluminum nitride is provided between the transparent substrate and the first layer aluminum nitride. However, the function of reducing the reflectance of the rare earth-transition metal amorphous alloy film is not impaired. Therefore, the high sputtering rate of tin oxide,
By making the first layer aluminum nitride thin,
The time required for film formation can be shortened.

The thickness of the first-layer aluminum nitride layer is set to be equal to or larger than the depth at which free oxygen generated from tin oxide enters the adjacent layer during the sputtering of the first-layer aluminum nitride. This prevents the rare earth-transition metal amorphous alloy film from being oxidized and deteriorated by free oxygen.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

As shown in FIG. 1, a magneto-optical disk 10 is provided.
Is, for example, a PC (polycarbonate) substrate 11 / first
Layer Tin oxide 12 (900) / First layer AlN13 (10 nm) / G
dTbFe14 (35 nm) / second layer AlN15 (10 nm) /
The second layer has a multilayer film structure of tin oxide 16 (11 nm) / Al17 (40 nm). First layer tin oxide 12 and second layer
The layer tin oxide 16 is a transparent conductive film, and GdTbFe14
Is an amorphous magnetic film.

Each of the films 12 to 17 is sequentially formed by an in-line sputtering device described later as schematically shown in FIG. The film formation rate of each individual film is 40 nm / min, which is the slowest for AlN, and 100 nm / min for GdTbFe, tin oxide, and Al. Therefore, GdTbFe1
The antireflection film of No. 4 and the reflectance enhancement film of Al17 are not composed of an AlN single layer as in the conventional case, but are composed of two layers of tin oxide and AlN so that a part of the conventional AlN film is sputtered. Since it is replaced with tin oxide having a high rate, the time required for film formation of the magneto-optical disk 10 can be shortened.

First layer AlN13 and second layer AlN15
The reason why the film thickness is set to 10 nm is that the oxygen released from the oxide during sputtering is taken into the preceding and following films at a depth of about 3 to 5 nm. Therefore, if the thickness of the AlN layer is set to 10 nm in consideration of safety, free oxygen enters GdTbFe14 and GdTbFe14
There is no risk of oxidizing bFe14.

As a result of the above film structure, for example, the time required for forming each film with the above film thickness is 0.9 minutes for the first layer tin oxide 12 and 0.225 minutes for the first layer AlN 13. , GdT
bFe14 is 0.35 minutes, second layer AlN15 is 0.225
2nd layer tin oxide 16 requires 0.11 minutes and Al 17 requires 0.4 minutes, which is 2.2 1 minutes in total, and the total film formation time is It is greatly reduced from 3.7 75 minutes.

As described above, the in-line sputtering device shown in FIG. 2 is used as a mass production device in the film forming process of the magneto-optical disk 10. In this apparatus, in the vacuum chamber 21, from the upstream side of the line, a preliminary chamber 25 in which rough vacuum evacuation is performed, a first layer tin oxide sputtering chamber 22a, a first layer AlN sputtering chamber 26, and a GdTbFe sputtering chamber 2 are provided.
7, a second layer AlN sputtering chamber 28, a second layer tin oxide sputtering chamber 22b, and an Al sputtering chamber 29 are sequentially provided.

A buffer chamber 24 is provided between the sputtering chambers to make each sputtering process independent.
In addition, the first-layer tin oxide sputtering chamber 22 is sandwiched by the buffer chamber 24.
There are two rooms a. Thus, seven targets are used in the film forming process of this embodiment.

In the film forming process, a plurality of disk-shaped PC substrates 23 mounted on the tray 20 are sequentially sent from the preliminary chamber 25 to each sputtering chamber, and the targets in each sputtering chamber are discharged one after another. The entire film forming process of this embodiment is rate-controlled by the film forming process of the first layer tin oxide 12 which takes the longest time to form a film. Therefore, according to the film formation time of the first layer tin oxide 12, the electric power applied to the targets of the other film formation processes is weakened, and the passage time of the tray 20 in each sputtering chamber is adjusted to be equal.

In this embodiment, as described above, the two first-layer tin oxide sputtering chambers 22a are provided, so that the passage time of the tray 20 in each sputtering chamber is 1 times that of the first-layer tin oxide.
It becomes equal to the film formation required time per chamber, and 0.9 minutes / 2 = 0.
It can be set to 45 minutes.

On the other hand, assuming that the film structure of the magneto-optical disk 10 is a PC substrate / first AlN (100 nm) / GdTbF.
In the case of e (35 nm) / second AlN (21 nm) / Al (40 nm), the sputtering process is configured with seven targets in the same manner as above by providing three sputtering chambers for the first AlN. it can. However, 100 nm thick first AlN
It takes 2.5 minutes to form a film, so tray 2
The passage time of 0 is 0.84 minutes (≈2.5 minutes / 3), which is the time required for film formation of the first AlN per chamber.

As described above, the magneto-optical disk 10 having the film structure according to the present invention can greatly reduce the time required for the film forming process.

Next, as shown in FIG. 3, the second layer tin oxide 16 may be omitted from the film structure of FIG. In this case, it is necessary to slightly change each film thickness, but the second layer AlN
By omitting the second layer tin oxide sputtering chamber 22b in the film forming process while setting the film thickness of 15 to the optimum value, it is possible to further reduce the time required for the entire film forming process.

[0033]

As described above, in the magneto-optical storage element according to the first aspect of the present invention, at least a part of the first transparent dielectric film on the transparent substrate side is sputtered from the first transparent dielectric film. Is replaced with a large transparent conductive film, and the time required for forming the magneto-optical storage element is shortened.

Therefore, at least a part of the first transparent dielectric film on the transparent substrate side is replaced with the transparent conductive film, so that the function of the first transparent dielectric film for reducing the reflectance of the perpendicular magnetization film is not impaired. In addition, the first transparent dielectric film can be thinned. Moreover, since the sputter rate of the transparent conductive film is higher than that of the first transparent dielectric film, there is an effect that the time required for forming the magneto-optical storage element can be shortened.

As described above, in the magneto-optical memory device according to the second aspect of the present invention, tin oxide, the first layer of aluminum nitride, the rare earth transition metal amorphous alloy film, the second layer of aluminum nitride, and the like are formed on the transparent substrate. The aluminum reflective film is formed in this order to shorten the time required for forming the magneto-optical storage element.

Therefore, since the function of reducing the reflectance of the rare earth-transition metal amorphous alloy film is taken care of by the two layers of the tin oxide layer and the first aluminum nitride layer, the first aluminum nitride layer is thinned. be able to. Moreover, since the sputtering rate of tin oxide is higher than that of the first layer aluminum nitride, there is an effect that the time required for film formation of the magneto-optical storage element can be shortened as a whole.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a film structure of a magneto-optical storage element according to the present invention.

FIG. 2 is an explanatory view schematically showing an in-line sputtering device used in a film forming process of a magneto-optical storage element.

FIG. 3 is a vertical cross-sectional view showing another film structure of the magneto-optical storage element according to the present invention.

FIG. 4 is a vertical sectional view showing a film structure of a conventional magneto-optical storage element.

FIG. 5 is an explanatory view schematically showing an in-line sputtering device used in a film forming process of a conventional magneto-optical storage element.

[Explanation of symbols]

10 magneto-optical disk (magneto-optical storage element) 11 polycarbonate substrate (transparent substrate) 12 first layer tin oxide (transparent conductive film) 13 first layer AlN (first transparent dielectric film) 14 GdTbFe (perpendicular magnetization film and rare earth) Transition metal amorphous alloy film) 15 Second layer AlN (second transparent dielectric film) 17 Al (reflection film)

Claims (2)

[Claims] 1. A magneto-optical memory device comprising a transparent substrate, a first transparent dielectric film, a perpendicular magnetization film, a second transparent dielectric film, and a reflective film formed in this order on at least the first transparent dielectric film. A magneto-optical memory characterized in that a part of the body film on the transparent substrate side is replaced with a transparent conductive film having a sputtering rate higher than that of the first transparent dielectric film, thereby shortening the time required for film formation of the magneto-optical memory element. element. 2. A magneto-optical storage element is formed by depositing tin oxide, a first layer of aluminum nitride, a rare earth transition metal amorphous alloy film, a second layer of aluminum nitride and an aluminum reflective film in this order on a transparent substrate. A magneto-optical storage element characterized in that the time required for the film is shortened.