JPH0626171B2 - Method for producing amorphous magnetic thin film - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing an amorphous magnetic thin film, and more particularly to a rare earth / transition metal amorphous magnetic thin film suitable for a magneto-optical recording medium or a magnetic bubble memory medium. It relates to a manufacturing method.

[Background of the Invention]

A necessary condition of the magnetic thin film used for the magneto-optical recording medium or the magnetic valve memory medium is that the magnetization is perpendicular to the film surface. That is, the following expression, Ku> 2πMs ² (1) must be satisfied. Here, Ku is the perpendicular magnetic anisotropy energy, and Ms is the magnetization.

From the equation (1), the perpendicular magnetic anisotropy energy needs to be a certain value or more. Further, in the magnetic bubble memory medium, it is necessary to control both the saturation magnetization and the perpendicular magnetic anisotropy energy to a certain specific value in order to hold the bubble main having a specific diameter.

Conventionally, as a method for controlling the magnitude of the perpendicular magnetic anisotropy energy of a rare earth / transition metal amorphous magnetic thin film, for example, as shown in Japanese Patent Publication No. 59-31970, an amorphous magnetic thin film is formed by a sputtering method. A method is known in which a reactive gas is mixed into the spatula gas at the time of manufacturing.

This method is a method of controlling the perpendicular magnetic anisotropy energy of the amorphous magnetic thin film by adjusting the partial pressure amount of the reactive gas to be mixed. However, it was found that the magnitude of the perpendicular magnetic anisotropy energy sensitively depends not only on the partial pressure amount of the mixed reactive gas but also on other thin film forming conditions such as the growth rate of the thin film. Therefore, the perpendicular magnetic anisotropy energy fluctuates in the film thickness direction or in the film plane, and the reproducibility is deteriorated, which causes a problem that the perpendicular magnetic anisotropy energy cannot be controlled accurately.

[Object of the Invention]

An object of the present invention is to provide a method for producing an amorphous magnetic thin film which can control the perpendicular magnetic anisotropy energy of the amorphous magnetic thin film made of a rare earth metal and a transition metal with high accuracy.

[Outline of Invention]

The present inventors have found that in the conventional method of mixing the reactive gas into the sputtering gas, the following two points cause the deterioration of the uniformity and controllability of the perpendicular magnetic anisotropy energy.

(1) The amount of the reactive gas taken into the thin film changes depending on not only the partial pressure amount of the reactive gas but also the growth rate of the thin film and the distance between the substrate and the target or the substrate temperature.

(2) The reactive gas mixed in the sputtering gas influences the particles, types and number of particles ejected from the target, and changes the composition and growth rate of the produced thin film.

The present invention recognizes these causes for the first time and uses a compound of a rare earth metal containing a reactive gas element as a part of a spatula target to eliminate the above causes and achieve the object of the present invention. According to the configuration of the present invention, the perpendicular magnetic anisotropy energy of the amorphous ferromagnetic thin film can be easily controlled by adjusting the ratio of the rare earth metal compound contained in the target. That is, since the reactive gas element is supplied from the target in a state of being combined with the rare earth element, the reactive gas element does not depend on the growth rate of the thin film, the distance between the substrate and the target, or the substrate temperature. Is taken into. Further, since the sputter gas does not contain a reactive gas, the transition metal or the rare earth metal does not react with the reactive gas on the target surface, and the spatter condition on the target surface is kept constant. In this way, the perpendicular magnetic anisotropy energy can be accurately controlled even with a very thin magnetic layer such as an interface layer of a desired magnetic thin film.

The method for producing an amorphous magnetic thin film according to the present invention includes various sputter methods including the high frequency sputter method and the ion beam sputter method. The rare earth metal compound containing a reactive gas element includes oxides, nitrides, chlorides, fluorides, hydrides, and the like. As a method for producing the target, in addition to a method in which a transition metal and a rare earth metal and a rare earth metal compound are combined to form a target, a so-called composite target, the transition metal and the rare earth metal are alloyed or burned in a reactive gas atmosphere. As a binder, there is a method of forming a target containing a compound of a rare earth metal and a reactive gas element. Alternatively, it can be manufactured by heat-treating a target composed of a transition metal and a rare earth metal in a reactive gas atmosphere. When forming an alloy or a sintered body in a reactive gas atmosphere, or when performing heat treatment, the ratio of the compound of the rare earth metal and the reactive gas element in the target should be changed according to the supply pressure of the reactive gas. You can

Example of Invention

Hereinafter, as an example of the present invention, an amorphous magnetic thin film of Gd—Co prepared by using Gd ₂ O ₃ as a part of a target and Tb− prepared by using TbF ₃ and Tb ₄ O ₇ , respectively.
An example of the Fe amorphous magnetic thin film will be described. Similar effects are obtained with Gd-Fe, Tb-Co, Ho-Co, Tb-Fe.
It can also be obtained in rare-earth transition metal amorphous magnetic thin films such as -Co and Gd-Tb-Fe-Co. Also, Bi, S
The same effect as that of the embodiment can be obtained also in the rare earth transition metal amorphous thin film to which an element such as n, Au, Cu, Mo, Al or Ni is added.

Fig. 1 shows 4mm on a Co disk with a diameter of 110mm and a thickness of 1mm.
The perpendicular magnetic anisotropy energy of a Gd-Co amorphous thin film prepared by the ion beam sputtering method using a composite target in which Gd pieces and Gd ₂ O ₃ pieces each having a thickness of 4 mm and a thickness of 1 mm are uniformly arranged. The relationship of the magnitude of magnetization is shown. The sputtering conditions are: substrate: Si substrate, sputtering gas pressure (Ar gas): 1.
9 × 10 ⁻² Pa, accelerating voltage: 1.1 kV, ion current amount: 60 mA, sputtering time: 40 minutes, and a thin film having a thickness of about 0.4 μm was prepared.

As shown in FIG. 1, the target rare earth component (Gd,
Gd ₂ O ₃₎ higher the ratio of Gd ₂ O ₃ increases in the large perpendicular magnetic anisotropy energy is obtained. Further, when the area ratio of Gd and G ₂ O ₃ is constant, the larger the area ratio of Co, the larger the saturation magnetization. That is, Gd, Gd ₂ O ₃ and Co
A thin film having desired perpendicular magnetic anisotropy energy and saturation magnetization can be obtained by adjusting the area ratio of.

FIG. 2 shows the growth rate dependence of the perpendicular magnetic anisotropy energy of the Gd-Co amorphous magnetic thin film produced by the above method. The amount of ion current was changed to control the growth rate of the thin film. The sputtering time was set so that the film thickness was about 0.4 μm. The other spatula conditions are the same as the above-mentioned conditions. The perpendicular magnetic anisotropy energy does not depend on the growth rate and has a constant magnitude.

Fig. 3 shows 4 mm on a Fe disk with a diameter of 110 mm and a thickness of 1 mm.
× 4mm, 1mm thick Tb piece, TbF ₃ piece and Tb piece
Using the composite Tagetsuto disposed respectively pieces and Tb ₄ O ₇ small pieces, showing a perpendicular magnetic anisotropy energy of Tb-Fe amorphous magnetic thin films prepared by RF sputter method. The horizontal axis is the rare earth metal component (Tb + TbF ₃ ,
Tb + Tb ₄ O ₇ ), a rare earth metal compound (Tb
F _3, shows the percentage of Tb ₄ O _7). Also in Tb-Fe amorphous magnetic thin film, TbF ₃ and Tb ₄ O occupying the Tagetsuto
_The perpendicular magnetic anisotropy energy increases as the ratio of ₇ increases.

〔The invention's effect〕

As described above, according to the present invention, since the compound of the rare earth metal containing the reactive gas element is used as a part of the target, it is possible to easily increase the perpendicular magnetic anisotropy energy and control it with good reproducibility. . It is possible to control the perpendicular magnetic anisotropy with high precision even when a very thin amorphous magnetic thin film having different magnetic properties is laminated in multiple layers.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the perpendicular magnetic anisotropy energy and the magnetization of an amorphous thin film of Gd—Co produced by using Gd ₂ O ₃ as a part of the target, and FIG. 2 is the perpendicular magnetic anisotropy. Figure 3 shows the dependence of energy on the growth rate. Figure 3 shows Tb-Fe.
It is a diagram showing the dependence on the ratio of TbF _3, Tb ₄ O ₇ in Tagetsuto the perpendicular magnetic anisotropy energy in amorphous thin film.

Claims (3)

[Claims] 1. A method for producing an amorphous magnetic thin film composed of a rare earth metal and a transition metal by a sputtering method, wherein a compound of a rare earth metal containing a reactive gas element is used as a part of the target. Of manufacturing a magnetic thin film. 2. The method for producing an amorphous magnetic thin film according to claim 1, wherein the rare earth metal compound accounts for 20% or more of the rare earth metal component in the target. 3. A patent using at least one compound selected from the group consisting of oxides, nitrides, chlorides, fluorides and hydrides as the compound of the rare earth metal containing the reactive gas element. The method for producing an amorphous magnetic thin film according to claim 1.