JP2000212735A - Sputtering target material composed of cobalt alloy and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an alloy target material in which the generation of sticking caused by inclusions in the target material called as particles is hard to occur by controlling the all maximum lengths of inclusions present therein to the length equal to or below the specified one. SOLUTION: A cobalt alloy ingot by a vacuum induction melting method is remelted by a vacuum arc melting method. This ingot is forged, rolled and thereafter machined to produce a cobalt alloy target material. By controlling the conditions of the vacuum induction melting, the conditions of the vacuum arc melting method or the like, the cobalt alloy target material in which the all maximum lengths of inclusions present therein is <=20 μm can be obtd. By this cobalt alloy target material, the generation of adhesion caused by inclusions in the target material called as particles at the time of sputtering is made rare. As the inclusions include oxides, nitrides or the like, they influence on the generation of particles, and, in the case the all maximum lengths thereof is <=20 μm, the number of particles remarkably decreases.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a sputtering target material made of a cobalt alloy and a method of manufacturing the same, and in particular, a thin film made of a cobalt alloy used as a magnetic recording material (hereinafter referred to as a cobalt alloy for magnetic recording). It belongs to the technical field related to a sputtering target material (hereinafter, a cobalt alloy target material) made of a cobalt alloy suitable for forming a thin film) and a method for producing the same.

[0002]

2. Description of the Related Art A cobalt alloy target material used for forming a cobalt alloy thin film for magnetic recording is usually manufactured through steps of melting, casting, forging, rolling and machining by a vacuum induction melting method.

[0003] However, according to the conventional cobalt alloy target material manufactured in this manner, during sputtering, adhesion by inclusions called "particles" in the target material occurs, or further, the adhesion occurs. Therefore, the quality of the formed cobalt alloy thin film may be affected. That is, inclusions in the target material scatter from the target and directly adhere to the cobalt alloy thin film formed on the substrate, or
The heat conduction is hindered by the inclusions immediately below, and the temperature rises and the target piece immediately above the inclusions melted away adheres to the substrate, or atoms sputtered out of the target are directly above the inclusions on the target surface again Adheres in the form of a film, and this adhered substance is melted and scattered from the target, and adheres to the substrate in the form of particles (ie, so-called particles), or the adhered substance is separated from the cobalt alloy thin film. However, as a result, there may be a problem that defects are generated in the cobalt alloy thin film.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object of the present invention is to prevent the occurrence of adhesion by inclusions in a target material called particles during sputtering. An object of the present invention is to provide a cobalt alloy target material and a method for manufacturing the same.

[0005]

In order to achieve the above object, a cobalt alloy target material (a sputtering target material made of a cobalt alloy) and a method of manufacturing the same according to the present invention are described. , And a method of manufacturing a cobalt alloy target material according to claim 2, which has the following configuration.

That is, the cobalt alloy target material according to the first aspect is a sputtering target material made of a cobalt alloy in which the maximum length of all the inclusions is 20 μm or less (first invention).

According to a second aspect of the present invention, there is provided a method for manufacturing a sputtering target material comprising a cobalt alloy, wherein an ingot for manufacturing the material is manufactured by a melting casting method including a vacuum arc melting step. A second aspect of the present invention is a method for producing a sputtering target material comprising a cobalt alloy.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is implemented, for example, as follows. An ingot made of a cobalt alloy is obtained by a vacuum induction melting method, and the ingot is remelted by a vacuum arc melting method. The obtained ingot is forged, rolled and then machined to produce a cobalt alloy target material. At this time, by adjusting the conditions of the vacuum induction melting and the conditions of the vacuum arc melting method, it is possible to obtain a cobalt alloy target material in which the maximum lengths of the internal inclusions are all 20 μm or less. That is, the cobalt alloy target material according to the present invention is obtained.

In such a form, the method for producing a cobalt alloy target material according to the present invention is carried out, and the cobalt alloy target material according to the present invention is obtained. The thus obtained cobalt alloy target material is used as a sputtering target material for forming a cobalt alloy thin film such as a cobalt alloy thin film for magnetic recording.

Hereinafter, the function and effect of the present invention will be mainly described.

The present inventors have prepared cobalt alloy target materials having inclusions of various sizes by various induction melting methods, and performed sputtering using these as a sputtering target, and carefully examined the situation at the time of sputtering. investigated.

As a result, the maximum length (length of the maximum length portion) of the inclusions existing in the cobalt alloy target material is all
It has been found that when the particle size is 20 μm or less, the number of particles is drastically reduced, and the generation of particles (attachment by inclusions in the target material) is rare and hard to occur.

The present invention has been completed based on this finding, and the cobalt alloy target material according to the present invention is a sputtering target material composed of a cobalt alloy in which the maximum length of the inclusions is 20 μm or less. Therefore, according to the cobalt alloy target material according to the present invention, adhesion by inclusions called “particles” in the target material during sputtering is rare and hard to occur (first invention).

Here, the maximum length of the internal inclusions is
The maximum length is 20 μm or less.
This is because if there is an inclusion exceeding m, particles having a size that causes a problem on the device due to the inclusions are likely to be generated, and the suppression of the generation of particles becomes insufficient.

When the maximum length of the internal inclusions is less than 20 μm, particles are rarely generated,
Unlikely to happen. In particular, all of the inclusions have a maximum length of 10 μm
In the following cases, particles are hardly generated and extremely unlikely to occur.

Inclusions include oxides and nitrides, all of which affect the generation of particles. When all of the maximum lengths are 20 μm or less, the number of particles is drastically reduced.

In producing a cobalt alloy target material according to the present invention in which the maximum length of all the internal inclusions is 20 μm or less, a vacuum induction melting method is used to obtain an ingot by using a vacuum induction melting method as a melting method. Sometimes it is desirable to apply a method of adding a flux that absorbs inclusions or a method of filtering a molten metal obtained by vacuum induction melting. This is because applying such a method makes it easier to obtain a cobalt alloy target material in which the maximum lengths of the inclusions are all 20 μm or less.

Further, when a method of remelting the ingot obtained by once melting and casting by the vacuum arc melting method (VAR method) is adopted as the ingot manufacturing method, the maximum length of the inclusions is 20%.
The cobalt alloy target material according to the present invention having a size of μm or less is particularly easily obtained. This is because even if there is a relatively large inclusion such as a maximum length of more than 20 μm in the ingot before the vacuum arc melting, the inclusion may be broken by the arc during remelting by the vacuum arc melting method. Because the inclusions are separated by floating (ie, the inclusions float in the molten metal and are separated at the top of the ingot), the inclusions having a maximum length of more than 20 μm can be extremely reduced and can be almost eliminated. is there.
This also lowers the oxygen concentration, often to 10 ppm or less.

In view of the above, as a method for producing a cobalt alloy target material according to the present invention, a cobalt alloy for producing a cobalt alloy target material is produced by a melting casting method including a vacuum arc melting step. A method for manufacturing a target material is employed (second invention). According to this manufacturing method, as described above, the cobalt alloy target material according to the present invention in which the maximum lengths of the inclusions are all 20 μm or less is particularly easily obtained, which is excellent in this point.

The method for producing a cobalt alloy target material according to the present invention requires that a melting and casting method include a vacuum arc melting step. Therefore, it is necessary to perform re-melting by a vacuum arc melting method. The method for producing the ingot before melting is not particularly limited, and a vacuum melting method or an air melting method can be used.

In the present invention, the maximum length of the inclusion is the length of the maximum length of the inclusion. For example,
When the shape of the inclusion is spherical, it is the diameter, and when it is a substantially rectangular parallelepiped, it is the length of the maximum side. The phrase “the maximum length of all the internal inclusions is 20 μm or less” means that any of the internal inclusions in the material has a maximum length of 20 μm or less.

The cobalt alloy composition of the cobalt alloy target material according to the present invention is not particularly limited, and is selected according to the composition of the cobalt alloy thin film to be formed.

[0023]

EXAMPLES (Examples 1 to 3 and Comparative Examples 1 to 3) A Co-13 at% Cr-4 at% Ta alloy was melted by a vacuum induction melting method.
An ingot of a Co-13at% Cr-4at% Ta alloy was produced. At this time, the oxygen level was varied. This ingot was forged, rolled, and machined to produce a φ6 inch cobalt alloy target material.

Sputtering was performed using this cobalt alloy target material, and the occurrence frequency of particles was investigated. On the other hand, the maximum length of the inclusions present in the cobalt alloy target material was investigated.

At this time, regarding the investigation of the maximum length of the inclusions, a method of measuring a size of the inclusions by collecting a microscopic sample from a cobalt alloy target material, polishing the sample, and observing the sample with an optical microscope is used. went.

The sputtering was performed under the sputtering conditions shown in Table 1 for 10 minutes. Thus, a cobalt alloy thin film having a thickness of 3 μm was formed on the substrate. In order to investigate the frequency of generation of particles, the surface of the cobalt alloy thin film formed on the substrate was observed using an optical microscope, and particles having a size (maximum length): 3 μm or more (adhered matter and adhered matter) were observed. The number of peeling marks was measured. Here, the reason for measuring particles having a size of 3 μm or more is as follows.
In particular, particles having a size of 3 μm or more seriously impair the performance of the thin film and cause a problem.

The causes of the particles include not only the case where the inclusions scatter directly, but also the case where the inclusions are crushed and scattered, or the base material portion other than the inclusions due to the presence of the inclusions, for example, just above the inclusions. In the case where the element is detached, the detachment of the reattachment may be considered. In these cases, particles smaller than the size of the inclusion are generated. Among such particles, those having a size of 3 μm or more are particularly problematic.

[0028]

[Table 1]

[0029]

[Table 2]

Example 4 Co-13 was obtained by a vacuum induction melting method.
at% Cr-4 At% Ta alloy is melted to form Co-13at% Cr-4
An ingot of an at% Ta alloy was produced, and the ingot was melted again by a vacuum arc melting method. The ingot obtained by the remelting was forged, rolled, and machined to produce a φ6 inch-shaped cobalt alloy target material.

Using this cobalt alloy target material, sputtering was performed in the same manner as in Examples 1 to 3 and Comparative Examples 1 to 3, and the occurrence frequency of particles was investigated in the same manner. On the other hand, the maximum length of the inclusions present in the cobalt alloy target material was determined in Examples 1 to 3.
3. Investigation was performed in the same manner as in Comparative Examples 1 to 3.

(Results of Investigation) Table 2 shows the results of investigation of the maximum length of inclusions and the frequency of particle generation in Examples 1 to 3, Comparative Examples 1 to 3, and Example 4. The results are shown in FIG. 1 as a relationship between the maximum length of inclusions and the frequency of occurrence of particles (the number of particles having a size of 3 μm or more (per φ4 inch substrate)).

As can be seen from Table 1, in the case of Comparative Example 1,
The maximum length of the inclusions existing in the cobalt alloy target material is 60 μm, and the frequency of generation of particles is extremely high. In the case of Comparative Examples 2 and 3, the maximum length of the inclusions was smaller and the frequency of generation of particles was less than that in the case of Comparative Example 1, but the maximum lengths of the inclusions were 30 μm and 25 μm. Frequently, particle generation is not sufficiently suppressed.

On the other hand, in Examples 1 to 4, no inclusions having a maximum length of more than 20 μm were observed, and the maximum lengths of the inclusions were 20 μm, 15 μm, 15 μm and 8 μm, and particles were generated. Infrequent.

FIG. 1 shows that as the maximum length of the inclusions existing in the cobalt alloy target material decreases, the frequency of generation of particles decreases, and when the maximum lengths of the inclusions are all 20 μm or less. Indicates that the frequency of occurrence of particles is 0 and that no particles are generated.

In the above Examples 1 to 4 and Comparative Examples 1 to 3, the Co-13 at% Cr-4 at% Ta alloy was used as the cobalt alloy as the cobalt alloy target material, and the above results were obtained. However, similar results are obtained when a cobalt alloy of another composition is used instead of the cobalt alloy.

[0037]

According to the cobalt alloy target material (sputtering target material made of a cobalt alloy) according to the present invention, particles are less likely to be generated during sputtering. Therefore, it is possible to form a cobalt alloy thin film by sputtering without causing performance degradation due to particles, and to improve the performance of the cobalt alloy thin film.

According to the method for producing a cobalt alloy target material according to the present invention, the maximum length of the internal inclusions is
The cobalt alloy target material according to the present invention having a size of 20 μm or less is obtained, and the reliability and ease of obtaining such a cobalt alloy target material are improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the maximum length of inclusions existing in a cobalt alloy target material and the frequency of generation of particles according to examples and comparative examples of the present invention.

Claims (2)

[Claims] 1. The maximum length of all internal inclusions is 20 μm.
A sputtering target material comprising the following cobalt alloy. 2. A method for producing a sputtering target material comprising a cobalt alloy, wherein the ingot for producing the material is produced by a melting casting method including a vacuum arc melting step. Manufacturing method.