JPS6113456A - Manufacture of photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the photomagnetic recording medium excellent in reproducibility and never causes a device to deteriorate by using mixed gas of inert gas and hydrogen gas as sputter gas used for sputtering. CONSTITUTION:A target which has a small piece of Tb arranged on a Co disk of 110mm. in diameter so that its occupation area is 35% of that of the disk is used. A vacuum is produced up to a 8X10<-7>Torr attainable degree of vacuum and then the mixed sputter gas of hydrogen gas varied in addition amount and argon gas is admitted into a vacuum tank for sputtering; and high frequency electric power of 100W is applied under 5X10<-3>Torr total pressure to perform sputtering, thereby forming a Tb-Co thin film on a glass substrate. Even if there is time or spatial variation in hydrogen partial pressure PH2, the value Ku does not vary greatly and the reproducibility of the Ku value is high. The Ku value is controllable according to the composition of the target for sputtering, i.e. the number of Tb small pieces arranged on the Co plate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for manufacturing a magneto-optical recording medium, and particularly to a manufacturing method suitable for forming a film of the recording medium by a sputtering method or a vapor deposition method.

[Background of the invention]

In recent years, magneto-optical recording has attracted much attention as an optical recording method that allows information once recorded to be erased and used repeatedly. As a recording medium used for magneto-optical recording, an amorphous metal magnetic thin film made of a rare earth metal and a transition metal is advantageous in terms of recording sensitivity and read performance.

The most basic characteristic required of this amorphous metal magnetic thin film is that the magnetization be perpendicular to the film surface.

In other words, it is necessary that the energy for keeping the magnetization perpendicular (perpendicular magnetic anisotropy energy Ku) is sufficiently large. When manufacturing such thin films (perpendicularly magnetized films) by sputtering, the conventional method has been to apply a bias voltage to the substrate. However, since the substrate is made of an insulating material such as glass, must be made conductive by some means, which complicates the thin film manufacturing process. Furthermore, since the substrate is damaged, there is also the problem that the shape of the guide groove formed on the substrate is disturbed.

In order to solve such problems, for example,
As described in Publication No. 3-76399, sputtering is performed by mixing a reactive gas (e.g., nitrogen, oxygen, chlorine gas, etc.) into a non-reactive sputtering gas (e.g., argon gas) to obtain a perpendicularly magnetized film. There is a method. However, in the method of mixing nitrogen gas, the perpendicular magnetic anisotropy energy Ku of the thin film produced changes greatly due to slight fluctuations in the nitrogen gas partial pressure, making it difficult to produce thin films with good reproducibility. Yes. Furthermore, oxygen gas and chlorine gas have the problem of causing oxidation and corrosion of the vacuum exhaust system of the sputtering apparatus.

[Purpose of the invention]

An object of the present invention is to provide a method for manufacturing a magneto-optical recording medium that has good reproducibility and does not cause any deterioration.

[Summary of the invention]

In order to achieve the above object, the present invention provides a method for manufacturing an amorphous magneto-optical recording medium made of an alloy of a rare earth metal and a transition metal by a sputtering method or a vapor deposition method. The gas is a mixed gas of an inert gas and hydrogen gas, and the atmosphere used during the vapor deposition is 1×1o-5.
It is characterized by containing H2 at a gas pressure of ~I x 10-'Torr.

[Embodiments of the invention]

The present invention will be explained below using examples.

FIG. 1 is a diagram showing that perpendicular magnetic anisotropy energy Ku can be induced in a Tb--Co thin film. The thin film whose characteristics are shown in this figure was produced by high-frequency sputtering. That is, Tb is placed on a 00 disk with a diameter of 110 mm.
Using a target arranged with -glπ so that the area occupied by the small piece is 35% of that of the disk, the vacuum degree reaching λ is 8
After evacuation to X 10 Torr, mixed sputtering gas of hydrogen gas and argon gas with different amounts of hydrogen gas added was introduced into the sputtering vacuum chamber, and the total pressure was raised to 5 X
Sputtering was performed by applying 100 W of high-frequency power under 1 O-3 Torr, and sputtering was performed on the glass substrate.
I'b-C! o A thin film was formed. The horizontal axis in Figure 1 is the hydrogen partial pressure (P"2) in the above-mentioned mixed sputtering gas, and the vertical axis is the uniaxial anisotropy energy Ku. Note that as the hydrogen partial pressure P H2 increases, the Tb concentration increases. tends to decrease slightly, and the composition when P) + 2 = Q% is T
b26. sCo7.3.5%p)+2:
The composition at 10% was Tb (!o)23.3 76.7 The alloy composition is shown in atomic percent. From the same figure, P
)+2 becomes 5% or more, the size of Ku becomes almost constant. However, if the PH2 becomes too large, the film formation rate will slow down, making it impractical, and there is also the risk of explosion.
The upper limit of H2 is 30%, more preferably up to 15%. That is, PH2 is 5-30%, more preferably 5-1
If it is set within the range of 5%, the value of Ku will not change much even if the hydrogen partial pressure P H2 changes over time and space. In other words, the Ku value.

This shows that reproducibility is high.

Note that the Ku value can be controlled by the composition of the sputtering target, that is, the number of Tb pieces placed on the CO deposition plate. However, in order to obtain a thin film with characteristics that can withstand use as a magneto-optical recording medium (for example, a squareness ratio of 1), the number of Tb pieces must be set so that its composition is close to the compensation composition. Must be. Figure 2 shows Tb when the hydrogen partial pressure PH2 is 0% and 10%, respectively.
-C! FIG. 3 is a diagram showing the relationship between the saturation magnetization MS of the o film and the target composition.

When pH2 goes from 0% to 10%, the compensation composition increases by several %T
b Shifts to the excessive side. This is produced by co because hydrogen selectively combines with some of the Tb to make it non-magnetic.

This is because the Tb concentration required to cancel the sublattice magnetization is required accordingly. Therefore, when constructing the target, it is necessary to take this into consideration and arrange more Tb pieces than in the case of normal sputtering using only argon gas.

FIG. 3 shows the pH2 dependence of Ku of the Dy-Co thin film. The target and sputtering conditions during film formation are the same as those described in the explanation regarding FIG. 1, and the deviation in composition is also about the same as in the case of the Tb--Co thin film. Although the Ku value is smaller than that of the Tb-Co thin film, it can be seen that Ku is induced as the PH2 increases.

The above is Tb-C! Although the present invention has been described for O and Dy-Co systems, similar effects can be obtained for amorphous metal magnetic thin films made of alloys of other rare earth metals and transition metals. In particular, Tb as a rare earth metal element
, as can be seen from the two examples, large anisotropic energy can be induced. For example, the Tb-Co thin film shown in this example or the Tb-Fe thin film
, Tb-Gd-Co.

By forming a Tb-Fe-Co thin film or the like using the method of the present invention, a perpendicularly magnetized film with large anisotropic energy can be obtained.

In order to thermally stabilize the thin film produced by the manufacturing method of the present invention, it is necessary to add T to the rare earth-transition metal thin film.
i, Zr, Nb, Or, AI, Ga+Ge+
'-Elements such as Rh, Ru, and pt may be added.

The present invention is not limited to high frequency sputtering, but includes direct current sputtering, magnetron sputtering,
Similar results can be obtained when forming a thin film using ion beam sputtering or the like. Further, the inert gas may be other than argon gas, and neon gas, krypton gas, xenon gas, etc. can be used. Furthermore, although the adhesion to the substrate is inferior to that of the sputtering method, even when using the vapor deposition method, 1×10 to I
By introducing hydrogen gas to the H2 gas pressure of X 10 Torr, Tb-(Eo, Dy-C
o, Tb-Fe, Gd-Fe, Gd-C
A perpendicularly magnetized film can also be obtained in an amorphous metal magnetic thin film such as .

[Effects of the Invention] As described above in detail, the present invention can provide a method for manufacturing a magneto-optical recording medium that has good reproducibility and does not cause deterioration of a film forming apparatus.

[Brief explanation of drawings]

Figure 1 shows the perpendicular magnetic anisotropy energy of a Tb-Co amorphous magnetic thin film produced by sputtering in a mixed sputtering gas of argon gas and hydrogen gas, as well as the hydrogen partial pressure in the mixed gas. Figure 2 shows the dependence of Tb − when the hydrogen partial pressure in the mixed sputtering gas is kept constant.
A diagram showing the composition dependence of saturation magnetization of a Co amorphous magnetic thin film,
Figure 3 shows Dy-C. FIG. 3 is a diagram showing the hydrogen partial pressure dependence of the perpendicular magnetic anisotropy energy of an amorphous magnetic thin film produced in a mixed sputtering gas.

Claims (1)

[Claims] 1. In a method for manufacturing an amorphous magneto-optical recording medium made of an alloy of rare earth metal and transition metal by sputtering or vapor deposition, the atmospheric gas used during the sputtering or vapor deposition is hydrogen gas. 1. A method for manufacturing a magneto-optical recording medium, comprising: 2. The method for producing a magneto-optical recording medium as set forth in claim 1, characterized in that the atmospheric gas consists of 5 to 30% hydrogen gas and the remainder inert gas, and is produced by a sputtering method. A method for manufacturing a magneto-optical recording medium. 3. The method for manufacturing a magneto-optical recording medium according to claim 2, wherein the atmospheric gas is composed of 5 to 15% hydrogen gas and the remainder inert gas. Method. 4. A method for manufacturing a magneto-optical recording medium according to claim 1, 2 or 3, characterized in that the rare earth metal contains at least Tb.