JP2000199056A - Rare earth-ferromagnetic metallic target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rare earth-ferromagnetic metallic target capable of increasing the utilizing efficiency more than the conventional case while securing the uniformity of the compositional distribution of a thin film to be formed at the time of sputtering. SOLUTION: This invention relates to a rare earth-ferromagnetic metallic target consisting essentially of at least one kind of rare earth elements and at least one kind of ferromagnetic metallic elements selected from (Co, Fe and Ni), in which at least one kind of powder contg. intermetallic compds. of the rare earth elements and ferromagnetic metallic elements is sintered, has a structure consisting essentially of rare earth phases substantially composed of rare earth elements, ferromagnetic metallic phases consisting essentially of ferromagnetic metallic metals and intermetallic compd. phases of rare earth elements and ferromagnetic metallic elements, and in which voids are dispersed, and the void volume of the target is 5 to 20%. Preferably, the powder contg. the intermetallic compd. phases of rare earth elements and ferromagnetic metallic elements has a compsn. showing the eutectic crystals of rare earth elements and ferromagnetic metallic elements. In the target, the maximum permeability can be controlled to <=10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth-ferromagnetic metal target used for forming a magneto-optical recording medium.

[0002]

2. Description of the Related Art Rare earth-ferromagnetic metal-based amorphous films used for information storage media and the like have various types of magneto-optical recording media because they have a small saturation magnetization and a perpendicular magnetization film can be obtained, and the medium noise is low. Research and development have been performed. This rare earth-ferromagnetic metal-based amorphous film is usually manufactured by a technique called magnetron sputtering. In this method, for example, a sputtering target adjusted to have a desired composition is used, a leakage magnetic flux is generated on the surface of the target, and plasma such as Ar is concentrated on the target surface by the leakage magnetic flux, so that the target surface is efficiently sputtered. Is what you do. Then, a thin film can be obtained on the substrate by attaching the sputtered particles sputtered by the plasma to the substrate.

[0003]

In the magnetron sputtering method described above, it is a major problem how to efficiently obtain a leakage magnetic flux on the target surface and increase the utilization efficiency of the target. As one of techniques for increasing the leakage magnetic flux, Japanese Patent Application Laid-Open No. 2-200778 discloses that the porosity of a rare-earth alloy ferromagnetic target is set to 1 to 60%.
Techniques for reducing the maximum magnetic permeability have been proposed. This method is effective as a method for reducing the maximum magnetic permeability. However, simply lowering the maximum magnetic permeability is not sufficient as a target for forming a magneto-optical recording medium.

For example, when a rare-earth-ferromagnetic metal-based target is to be formed into a thin film for a magneto-optical recording medium, unlike a normal target, it does not have a uniform phase structure but a rare-earth element phase. It has been known that the composition of a thin film to be formed is more uniform when the existence ratio of the intermetallic compound phase composed of a rare earth element and a ferromagnetic metal and the ferromagnetic metal phase is controlled to be present. ing.

As a target corresponding to this phenomenon, for example, as disclosed in Japanese Patent Application Laid-Open No. 62-70550, a rare earth element powder and an iron powder which is a ferromagnetic powder are sintered, and then the rare earth element and the ferromagnetic powder are heated. A target in which the amount of an intermetallic compound phase with an element is controlled is known. Further, the present applicant discloses in Japanese Patent Application Laid-Open No. 1-25977 that the eutectic structure of a rare earth element and a ferromagnetic metal, that is, the interphase between a rare earth element phase (α phase of a rare earth element) and a rare earth metal and a ferromagnetic metal, Proposal of a method of sintering a raw material powder having a structure of a compound phase and a ferromagnetic metal powder to make each of an intermetallic compound phase composed of a rare earth element and a ferromagnetic metal and a ferromagnetic metal phase exist. I have.

Furthermore, the present applicant has proposed a method of miniaturizing ferromagnetic metal particles (Japanese Patent Laid-Open No. 5-2719) as a method for preventing a decrease in the utilization efficiency of a target whose texture is controlled as described above.
No. 15, JP-A-6-184740) and a method of adding a small amount of a rare earth element to a ferromagnetic metal phase present in the structure (JP-A-5-320888, JP-A-7-90567). Each of these methods is an effective method in reducing the maximum magnetic permeability.

[0007] However, there is a demand for further improvement in utilization efficiency, and there has been a case where it is not sufficient to achieve both utilization efficiency and uniformity of the composition distribution of a thin film to be formed. Therefore, an object of the present invention is to provide a rare earth-ferromagnetic metal-based target capable of further improving the utilization efficiency as compared with the conventional one while ensuring uniform composition distribution of a thin film formed during sputtering.

[0008]

The present inventors can control the composition ratio of a rare earth metal phase, a ferromagnetic metal phase, an intermetallic compound phase of a rare earth element and a ferromagnetic metal element, and further reduce the maximum magnetic permeability. The method was studied. By forming a compound of a rare earth element and a ferromagnetic metal in advance as a raw material, even if the voids are dispersed in the target structure to lower the maximum magnetic permeability, the metal phase, the ferromagnetic metal phase, the rare earth element And the composition ratio of the intermetallic compound phase with the ferromagnetic metal element can be easily adjusted,
The inventors have found that a thin film having a uniform composition can be obtained, and have reached the present invention.

That is, the present invention provides at least one rare earth element and at least one rare earth element selected from (Co, Fe, Ni).
A rare earth-ferromagnetic metal-based target containing at least one ferromagnetic metal element as a main component, wherein at least one powder containing an intermetallic compound of the rare earth element and the ferromagnetic metal element is sintered; Rare earth phase composed of a rare earth element, a ferromagnetic metal phase mainly composed of a ferromagnetic metal, an intermetallic compound phase mainly composed of a rare earth element and a ferromagnetic metal element, and from a structure in which voids are dispersed in the structure. And a porosity of the target of 4 to 20%.

In the present invention, the rare earth element is preferably
The above-mentioned powder containing an intermetallic compound phase composed of a ferromagnetic metal element has a composition that expresses a eutectic of a rare earth element and a ferromagnetic metal element. The target of the present invention described above can have a maximum magnetic permeability of 10 or less.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An important feature of the present invention is that, as described above, a porosity of 5 to 5 is obtained by using a powder in which an intermetallic compound of a rare earth element and a ferromagnetic metal element is present in a raw material powder.
20% of the target has been obtained. For example, when sintering a rare earth element powder and a ferromagnetic metal powder as raw materials, the reduction of vacancies by sintering and the generation of an intermetallic compound by the reaction between the rare earth element and the ferromagnetic metal proceed simultaneously. At this time, the highly reactive rare earth element powder rapidly reacts with the ferromagnetic metal powder and becomes denser while increasing the intermetallic compound phase. Therefore, the adjustment of the amount of the intermetallic compound phase and the amount of voids due to the progress of sintering becomes extremely severe.

On the other hand, when a powder in which an intermetallic compound of a rare earth element and a ferromagnetic metal element is present in the raw material powder as in the present invention, the difference in concentration between the raw materials at the sintering interface is reduced, and Since the compound phase does not increase rapidly, it is easy to control the amount of vacancies. Furthermore, if a predetermined amount of an intermetallic compound is previously present in the raw material powder and sintering is performed at a temperature at which a liquid phase does not appear during sintering, there is almost no formation of an intermetallic compound during sintering and formation of voids. Therefore, there is also an advantage that a predetermined phase ratio can be obtained by substantially controlling only the density. Needless to say, at this time, if necessary, a ferromagnetic metal or a rare earth metal, which is insufficient in the amount of the ferromagnetic metal phase and the rare earth phase as the raw material powder, is mixed and sintered.

In a more preferred embodiment of the present invention, the powder containing the intermetallic compound phase composed of a rare earth element and a ferromagnetic metal element has a composition that expresses a eutectic of the rare earth element and the ferromagnetic metal element. . Since the eutectic point of the rare earth element and the intermetallic compound composed of the rare earth element and the ferromagnetic metal element is lower than that of the rare earth metal phase and the ferromagnetic metal phase, the sintering temperature can be lowered, and the sintering temperature can be reduced. This is because sintering can proceed while suppressing the reaction during sintering, and the porosity can be easily adjusted.

In the present invention, the porosity is 5-20.
The percentage is that if the porosity is less than 5%, it does not contribute much to the decrease in the maximum magnetic permeability, and if it exceeds 20%, the number of abnormal discharges (number of arcs generated) during sputtering increases sharply. To do that. Preferably it is 6 to 10%. In the target of the present invention, for example, A
One or more elements selected from the group consisting of 1, Ti, Cr, Nb, and Ta can be contained. These elements are elements that are often introduced as elements that are effective in improving the corrosion resistance of the thin film to be formed. These additional elements may be introduced as a simple substance or as an alloy with a ferromagnetic metal or a rare earth element.

[0015]

EXAMPLES (Example 1) Tb-40Fe (at%) eutectic structure powder, pure Fe powder, pure C obtained by the atomizing method
o powder and Fe-16Cr (at%) alloy powder to Fe-2
The powder mixed to be 1.5Tb-7.0Co-3.0Cr (at%) was subjected to hot isostatic pressing to obtain 10%.
Sintering was performed at 0 MPa, 3 hours, at 500 ° C. and 600 ° C., to obtain a target.

FIG. 1 shows a 50-fold microstructure of the target sintered at 500 ° C., and FIG. 2 shows a 50-fold microstructure of the target sintered at 600 ° C. Each porosity was determined by the following equation from the density ρt obtained by measuring the density of the melted material having the same composition by the Archimedes method and the density ρ obtained in the same manner for the manufactured target. Table 1 shows the results. Porosity = (ρt−ρ) × 100 / ρt The maximum magnetic permeability was determined by measuring the magnetic properties. Table 1 shows the results.

[0017]

[Table 1]

Each target was set to an Ar pressure of 0.3 P
a, input power 500W, T / S distance 60mm, film thickness 1μ
A film was formed aiming at m, and composition analysis was performed at five points at intervals of 10 mm from the center of the substrate. Table 2 shows the maximum and minimum values of the Tb composition in the composition analysis. Table 2 also shows the number of abnormal discharges (number of arcs) during 5 minutes of sputtering.

[0019]

[Table 2]

As shown in FIGS. 1 and 2, the target of the present invention manufactured by changing the sintering temperature hardly generates a compound at the interface between the raw materials. Further, it can be seen that by adjusting the sintering temperature as shown in Table 1, targets having different porosity can be obtained, and at the same time, the maximum magnetic permeability can be reduced. In addition, as shown in Table 2, it can be confirmed that the Tb concentration distribution is almost uniform in both targets.

(Example 2) Fe-21.5Tb-7.0Co-3.0Cr under the raw material powders and sintering conditions shown in Table 3.
(At%) target was produced. However, the raw material powder was produced by an atomizing method. Each of the targets had a structure in which an intermetallic compound phase, a ferromagnetic metal phase, and a rare earth metal phase were substantially present.

[0022]

[Table 3]

Table 4 shows the porosity and the maximum magnetic permeability of the produced target. Each target was subjected to Ar pressure 0.3 Pa, input power 500 W, T / S distance 60 mm,
A film was formed with the aim of a film thickness of 1 μm, and composition analysis was performed at five points at intervals of 10 mm from the center of the substrate. Table 5 shows the maximum and minimum values of the Tb composition in the composition analysis. Table 5 also shows the number of abnormal discharges (number of arcs) during 5 minutes of sputtering.

[0024]

[Table 4]

[0025]

[Table 5]

From Tables 3 and 4, it can be confirmed that the target of the present invention has a low maximum magnetic permeability, and the Tb concentration distribution during film formation is almost uniform. It can also be seen that if the porosity of the target is greater than 4%, the maximum magnetic permeability increases, and if it exceeds 20%, an arc is generated.

[0027]

According to the present invention, it is possible to provide a rare earth-transition metal based target having a low maximum magnetic permeability suitable for magnetron sputtering while maintaining the phase structure and the sputtering characteristics for determining the composition distribution of the thin film to be formed. It has become possible.

[Brief description of the drawings]

FIG. 1 is a photograph showing a metal microstructure of a target of the present invention.

FIG. 2 is a photograph showing another metal microstructure of the target of the present invention.

Claims (3)

[Claims] (1) at least one rare earth element;
o, Fe, Ni) is a rare earth-ferromagnetic metal target mainly containing at least one ferromagnetic metal element selected from the group consisting of at least one ferromagnetic metal element, and at least one containing an intermetallic compound of a rare earth element and a ferromagnetic metal element. One kind of powder is sintered, a rare earth phase substantially composed of a rare earth element, a ferromagnetic metal phase mainly composed of a ferromagnetic metal, an intermetallic compound phase of a rare earth element and a ferromagnetic metal element mainly, and Consisting of a structure in which voids are dispersed in the structure, and the porosity of the target is 5 to 20
% Rare earth-ferromagnetic metal target. 2. The powder according to claim 1, wherein the powder containing the intermetallic compound phase of the rare earth element and the ferromagnetic metal element has a composition exhibiting a eutectic of the rare earth element and the ferromagnetic metal element. The rare earth-ferromagnetic metal-based target described in the above. 3. The rare earth-ferromagnetic metal-based target according to claim 1, wherein the maximum magnetic permeability is 10 or less.