JP4026767B2 - Co-Cr-Pt-B alloy sputtering target and method for producing the same - Google Patents

Description

  The present invention relates to a Co—Cr—Pt—B alloy sputtering target having no uniform pores and a uniform fine cast structure, and a method for producing the same.

In recent years, Co—Cr—Pt—B based alloys have been used as sputtering targets for forming magnetic films of hard disks.
In order to form a film by sputtering, an electric field is generated by applying a high voltage between these substrate and target under an inert gas atmosphere, usually facing a target consisting of a positive electrode and a negative electrode. To be done.
By the application of the high voltage, the ionized electrons collide with the inert gas to form a plasma, the cations in the plasma collide with the target (negative electrode) surface, and the target atoms are knocked out, This is based on the principle that the projected atoms adhere to the opposing substrate surface to form a film.
Such sputtering methods include a high frequency sputtering (RF) method, a magnetron sputtering method, a DC (direct current) sputtering method, and the like, which are used as appropriate depending on the target material and film formation conditions.

Generally, when manufacturing a sputtering target, it is required to have a uniform and fine structure and be free from defects such as pores. This is because when the target structure is non-uniform and there are many defects, the defects are reflected in the sputtering film formation, and a uniform film is not formed, resulting in a film with poor performance. In addition, there is a problem that the generation of particles increases when the sputtered film is formed.
For this reason, after melt-casting a target material, rolling and the like are performed to try to obtain a uniform and dense processed structure (see, for example, Patent Document 1).

However, the casting of a Co—Cr—Pt—B alloy is an extremely hard and brittle material, so that it is very difficult to perform rolling.
Even if such processing could be realized, there was a problem that yield was poor and productivity was poor. In addition, there is a problem that defects and structural non-uniformity generated in the casting stage remain after rolling.
JP 2002-69625 A

  The present invention relates to a Co-Cr-Pt-B alloy sputtering target having no internal pores and a uniform fine cast structure and a method for producing the same, and enables the production of the target stably and at low cost. The object is to prevent or suppress the generation of particles and increase the product yield of film formation.

In order to solve the above-mentioned problems, the present inventors have conducted intensive research. As a result, by optimizing the casting conditions of the Co—Cr—Pt—B alloy, there is no internal pore, and the casting is fine and uniform. The organization was obtained, and the knowledge that a film with good quality can be formed and the manufacturing yield can be remarkably improved was obtained.
The present invention is based on this finding,
1) Co—Cr—Pt—, characterized in that the diameter of the dendrite branch is 100 μm or less, does not have a cellular structure, and has a fine cast structure in which the layer thickness of the eutectic structure is 50 μm or less. B-based alloy sputtering target,
2) The sputtering target according to claim 1, wherein the maximum magnetic permeability (μmax) is 20 or less.

The present invention also includes 3) a diameter of the dendrite branch of 100 μm or less, no cellular structure, and a fine cast structure in which the layer thickness of the eutectic structure is 50 μm or less. Co-Cr-Pt-B alloy sputtering target manufacturing method characterized by being 15 mm or less, 4) Dendritic branch diameter is 100 μm or less, has no cellular structure, and has a eutectic structure A method for producing a Co—Cr—Pt—B alloy sputtering target, comprising a fine cast structure having a layer thickness of 50 μm or less, and cast using a mold made of a copper surface plate and aluminum titanate, 5) A method for producing a sputtering target according to 3), characterized by casting using a copper platen and a mold made of aluminum titanate, 6) The method for producing a sputtering target according to any one of 3) to 5), wherein the hot water temperature is cast at a melting point + 100 ° C. or higher, and 7) pouring of a bottom hole diameter of φ10 mm or less at the upper part of the mold gate A method for producing a sputtering target according to any one of 3) to 6), wherein a tundish provided with a nozzle is provided and poured into a mold through the pouring nozzle, and 8) directly below the pouring nozzle. In addition, an aluminum titanate plate is provided, and the method for producing a sputtering target according to any one of 4) to 7), 9) Rolling or forging cold working the cast ingot to 10% or less. The method for producing a sputtering target according to any one of 3) to 9), 10) The maximum magnetic permeability (μmax) is 20 or less, 3) to The manufacturing method of the sputtering target in any one of 10) is provided.

In the present invention, by optimizing the casting conditions of the Co—Cr—Pt—B alloy, there is no pore inside the sputtering target, and a fine and uniform casting structure can be obtained, thereby forming a film of good quality. And it has the outstanding effect that a manufacturing yield can be improved remarkably. Further, since it has a uniform and fine structure and has no defects such as pores, it has the effect of significantly reducing the generation of particles when forming a sputtered film.

As main materials of the Co—Cr—Pt—B alloy sputtering target of the present invention, Co—Cr—Pt comprising Cr: 1 to 40 at%, Pt: 1 to 30 at%, B: 10 to 25 at%, and the balance Co. Co-Cr-Pt-B made of -B alloy, Cr: 1 to 40 at%, Pt: 1 to 30 at%, B: 9 to 25 at%, Cu: 1 to 10 at%, B + Cu: 10 to 26 at%, balance Co Co-Cr-Pt-B made of Cu alloy, Cr: 1 to 40 at%, Pt: 1 to 30 at%, B: 1 to 25 at%, Ta: 1 to 10 at%, B + Ta: 3 to 26 at%, balance Co -Ta alloy etc. can be mentioned.
These materials are useful as a sputtering target for forming a magnetic film of a hard disk.

The Co—Cr—Pt—B alloy sputtering target of the present invention has a fine cast structure in which the diameter of the dendrite branch is 100 μm or less and the layer thickness of the eutectic structure part is 50 μm or less. Further, the target of the present invention has a maximum magnetic permeability (μmax) of 20 or less.
Since the target of the present invention has such a uniform and fine structure and has no defects such as pores, there is an effect that the generation of particles is remarkably reduced when a sputtered film is formed.

In the production of the Co—Cr—Pt—B alloy sputtering target of the present invention, the casting ingot has a thickness of 15 mm or less so that pores are not generated in the ingot as an ingot substantially close to the product thickness, and fine casting is performed. Form an organization. This fine structure of the ingot without defects is extremely important for forming a homogeneous and good quality film.
Furthermore, the present invention is cast by using a mold made of copper plate (bottom only) and aluminum titanate _(Al 2 TiO _5). The thermal conductivity of copper is 452 W / m · K, and the thermal conductivity of aluminum titanate is 2.42 W / m · K. This large difference in thermal conductivity is very important.

FIG. 1 is a schematic diagram showing the movement of the pores 3 when cast into a copper surface plate 1 and an upper mold 2 made of aluminum titanate.
That is, as shown in FIG. 1, due to the difference in thermal conductivity between copper and aluminum titanate, solidification starts from a copper surface plate (bottom) 1 and proceeds to the aluminum titanate side of the upper mold 2. The final solidification is directly under the aluminum titanate mold 2, and the generation of pores 3 due to the solidification shrinkage can be concentrated directly under the aluminum titanate mold 2 (ingot top side).
Since the lower bottom portion and the upper bottom portion of the solidified ingot are removed by cutting, the target has a uniform structure free from defects such as pores. This cast structure is shown in FIG.
In addition, aluminum titanate has a small thermal expansion coefficient (0.5 × 10 ⁻⁶ / ° C.), and therefore has a feature that it is not cracked by a rapid temperature change during pouring.

In casting, it is desirable to cast at a tapping temperature of melting point + 100 ° C or higher. As a result, the molten metal can be given sufficient fluidity to cause defects such as pores to float upward. Moreover, as shown in FIG.3 and FIG.4, the internal pore 3 can be concentrated on the hot water supply part 4 by making the pouring gate part into the hot water supply part 4. As shown in FIG.
An aluminum titanate plate 6 may be installed in place of copper at the surface plate position of the pouring position. Thereby, reaction with a cast metal and copper can be suppressed. A schematic illustration of these structures is shown in FIG.

Furthermore, the tendish 5 provided with the pouring nozzle of bottom hole diameter (phi) 10 mm or less is provided in the upper part of the pouring gate part of a mold, and it can pour into the mold 2 through this pouring nozzle. This makes it possible to remove inclusions and supply a stable amount of hot water, to prevent hot water from rampaging in the mold, and to reduce the inclusion of inclusions or bubbles.
As shown in FIG. 2, the sputtering target manufactured as described above has a uniform and fine cast structure in which the diameter of the dendrite branch is 100 μm or less and the layer thickness of the eutectic structure part is 50 μm or less.

Furthermore, the present invention can perform cold working such as rolling or forging of a cast ingot to 10% or less. As a result, the magnetic properties of the target material can be further controlled.
With the target of the present invention, a sputtering target having a maximum magnetic permeability (μmax) of 20 or less is obtained. In addition, since the target of the present invention has a uniform and fine structure and is free from defects such as pores, the generation of particles is significantly reduced when a sputtered film is formed.

  Hereinafter, description will be made based on Examples and Comparative Examples. In addition, a present Example is an example to the last, and is not restrict | limited at all by this example. In other words, the present invention is limited only by the scope of the claims, and includes various modifications other than the examples included in the present invention.

(Example 1 and Comparative Example 1-3)
A Co—Cr—Pt—B alloy raw material consisting of Cr: 12 at%, Pt: 12.5 at%, B: 14 at%, and the balance Co was melted at high frequency (vacuum). This was cast at a temperature of melting point + 100 ° C. using a copper surface plate and an upper mold of the material shown in Table 1 to obtain an ingot having a thickness of 15 mm. Comparative Examples 1-3 are a case where a mold material other than aluminum titanate is used and a case where no upper mold is used.
The presence of pores in the ingot thickness direction and the state of breakage of the mold were observed. The results are similarly shown in Table 1. In addition, it shows in Table 2 with reference to the thermal conductivity and thermal expansion coefficient of the molding material used by the Example and the comparative example.

As is apparent from Table 1, when the upper mold was not used (Comparative Example 1) and when cobalt was used as the mold (Comparative Example 2), the pores existed inside the ingot, resulting in a defective ingot. Similarly, alumina (Comparative Example 3) also had pores inside the ingot, and the alumina was broken.
On the other hand, when the aluminum titanate of Example 1 was used, it concentrated on the upper part (upper bottom) of the mold, that is, the top of the mold, and a good ingot was obtained. As shown in Table 2, this is considered to be due to the low thermal conductivity of aluminum titanate as compared with Comparative Example 1-3. From the above, it can be seen that aluminum titanate is optimal as the upper mold material.

(Example 2, Comparative Example 4-5)
Next, when casting the same material, copper was used for the surface plate, and aluminum titanate was used for the upper mold, and a hot water portion was provided to observe the position of the pore when the tapping temperature was changed. .
The results are shown in Table 3. As is apparent from Table 3, when the tapping temperature was less than the melting point + 100 ° C. (Comparative Examples 4 and 5), the pores did not concentrate on the hot water, resulting in insufficient movement of bubbles. Therefore, it turns out that it is desirable that the tapping temperature is a melting point + 100 ° C. or higher.

In the present invention, by optimizing the casting conditions of the Co—Cr—Pt—B alloy, there is no pore inside the target, and a fine and uniform cast structure can be obtained. By sputtering using the target thus manufactured, a film with good quality can be formed, and the manufacturing yield can be remarkably improved.
It is possible to obtain a Co—Cr—Pt—B alloy thin film having excellent characteristics as a target for forming an electronic component thin film, and is particularly suitable for a magnetic film of a hard disk.

It is a schematic diagram which shows the movement of a pore at the time of casting to the upper mold which consists of a copper surface plate and an aluminum titanate. It is a microscope picture which shows the casting structure of a target. It is the conceptual diagram which the pore concentrated on the feeder part. It is a conceptual explanatory drawing of the mold which provided the tendish provided with the pouring nozzle in the upper part of the pouring gate part of a mold.

Explanation of symbols

1. 1. A copper surface plate Upper mold 2. Pore 4 4. Hot water section Tundish Aluminum titanate plate

Claims (10)

Co-Cr-Pt-B system characterized in that the diameter of the dendrite branch is 100 μm or less, does not have a cellular structure, and has a fine cast structure in which the layer thickness of the eutectic structure is 50 μm or less Alloy sputtering target.   2. The sputtering target according to claim 1, wherein the maximum magnetic permeability (μmax) is 20 or less. The dendritic branch has a diameter of 100 μm or less, does not have a cellular structure, has a fine cast structure with a eutectic structure layer thickness of 50 μm or less, and has a cast ingot thickness of 15 mm or less. A method for producing a Co—Cr—Pt—B alloy sputtering target. The dendrite branch diameter is 100 μm or less, has no cellular structure, has a eutectic structure layer thickness of 50 μm or less, and uses a mold made of copper surface plate and aluminum titanate. And producing a Co—Cr—Pt—B alloy sputtering target.   4. The method for producing a sputtering target according to claim 3, wherein casting is performed using a mold made of a copper surface plate and aluminum titanate.   The method for producing a sputtering target according to any one of claims 3 to 5, wherein the hot water temperature is cast at a melting point of + 100 ° C or higher.   A tundish provided with a pouring nozzle having a bottom hole diameter of φ10 mm or less is provided at the upper part of the pouring gate part of the mold, and pouring into the mold through the pouring nozzle. The manufacturing method of the sputtering target of description.   The method for producing a sputtering target according to any one of claims 4 to 7, wherein an aluminum titanate plate is installed directly under the pouring nozzle.   The method for producing a sputtering target according to any one of claims 3 to 9, wherein the cast ingot is subjected to cold working of rolling or forging at 10% or less.   The method of manufacturing a sputtering target according to claim 3, wherein the maximum magnetic permeability (μmax) is 20 or less.

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