JPH10306368A - Co series cast target and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an inexpensive and easily producible Co cast target in which the dispersion of the magnetic properties of the target itself is suppressed and to provide the method for producing the same. SOLUTION: This target is the one essentially consisting of Co, contg. the group 4A or 5A elements forming intermetallic compounds with Co by above the solid solution limits and subjected to precision casting substantially into a target shape. It preferably applys to a target contg. Pt in particular. Furthermore, the dispersion of leakage magnetic flux density measured in the sputtering face of the target is preferably regulated to <=2%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a Co-based casting target used for forming a magnetic recording film and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Development of a Co-based magnetic film used for an information storage medium such as a computer having a high coercive force has been demanded due to a demand for a high recording density of the medium. The S / N ratio is also important as the recording / reproducing characteristics. In order to obtain such characteristics, a Co-based magnetic film containing various additive elements instead of pure Co has been developed. For example,
Co-Cr-Ta, Co-Ni-Cr, Co-Cr
Thin films containing various additives such as -Ta-Pt-based, Co-Ni-Cr-Pt-based, and B, Ti, W, and Mo are known. The above-mentioned thin film is usually manufactured by a technique called magnetron sputtering.
In this method, for example, a sputtering target adjusted so as to have a desired composition is used, a leakage magnetic flux is generated on the target surface, and plasma such as Ar is concentrated on the target surface by the leakage magnetic flux, and 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 recent years, magnetic heads for extracting information from a recording medium have been improved, and it has become possible to extract information even with a magnetic recording area of a smaller range than before. Therefore, it is required for a medium for recording information to produce a thin film having a high coercive force in which the information is not deteriorated even when recording is performed at a higher density. The above-mentioned additional elements such as Cr and Ta are mainly for increasing the coercive force of the thin film, and increasing the amount of these additional elements is performed as one measure for increasing the coercive force. In order to obtain a thin film with an increased amount of Cr, Ta or the like,
As a sputtering target, it is necessary to manufacture an alloy target in which an additive element is increased.

[0004] However, an increase in the amount of Cr, Ta or the like deteriorates plastic workability in obtaining a target, and makes hot working difficult. In general, when using an alloy that is difficult to plastically process as a target, the molten metal is cast into a mold to produce a cast ingot, and the obtained ingot is sliced. The method of manufacturing a plurality of sheets is applied. Also, using the powder sintering method,
A technique of machining a sintered ingot sintered to a predetermined size has also been used.

[0005] The present inventors have reported that a target with an increased amount of the 4A and 5A groups, that is, Ti, Zr, Hf, V, Nb, and Ta, forms an intermetallic compound with Co, and this compound is a starting point of cracking. Therefore, it was confirmed that plastic working was more difficult. Then, an ingot was produced by a casting method instead of a costly sintering method for a target that generates such an intermetallic compound, and an attempt was made to produce the target by slicing and hollowing. However, when a target is obtained by machining from an ingot produced by a general casting method, a Co-based sputtering target produced by the above-mentioned intermetallic compound,
There is a new problem that the magnetic properties of the sputtering target itself vary within the sputtering surface of the target.

As described above, in magnetron sputtering, it is necessary to concentrate plasma due to magnetic flux leakage, but if the magnetic characteristics of the target itself vary,
The leakage magnetic flux is disturbed, which causes the sputtering to be disturbed. This is a phenomenon called erosion failure, which causes the target to become unusable before the expected life, and has become a major problem in expensive Co-based targets. SUMMARY OF THE INVENTION An object of the present invention is to provide a Co-based cast target which suppresses variations in magnetic properties of the target itself, is inexpensive and easy to manufacture, and a method of manufacturing the same.

[0007]

SUMMARY OF THE INVENTION The present inventor has studied an improvement in the casting method in terms of ease of manufacture. The variation in the magnetic properties of the target itself is due to the segregation of the generated intermetallic compound with Co during solidification in the 4A and 5A groups, that is, in targets with increased amounts of Ti, Zr, Hf, V, Nb, and Ta. I found something to do. And as a result of further study, by applying the precision casting method, 4
The present inventors have found that an intermetallic compound of a group A, 5A and Co can be uniformly and finely dispersed in a structure, and as a result, a variation in magnetic properties of a target itself can be suppressed.

That is, the present invention relates to a target mainly composed of Co, which contains a Group 4A or Group 5A element which forms an intermetallic compound with Co beyond its solid solubility limit, and has a substantially precise target shape. This is a Co-based casting target that is cast.

In the present invention, it is particularly preferable to apply to a target containing Pt. Further, it is desirable that the variation of the leakage magnetic flux density measured on the sputtering surface of the target of the present invention be within 2%.

The above-mentioned target is made of, for example, an alloy melt mainly containing Co and containing an amount of a Group 4A or Group 5A element which forms an intermetallic compound with Co in an amount exceeding the solid solubility limit in a solidified state. 1350-1500 ° C
Then, it can be obtained by pouring into a precision casting mold having a target outer shape as a cavity preheated to 500 to 1100 ° C.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, an important feature of the present invention is that precision casting is used to obtain a Co-based target containing elements of the 4A or 5A group beyond the solid solubility limit. It is in. The precision casting referred to in the present invention means a material that is substantially cast into a target shape. In the conventional casting method, the solidification volume has to be increased due to the necessity of a feeder, etc., and casting in an unheated mold results in a variation in solidification rate, which promotes segregation of intermetallic compounds. there were. In the present invention, the precision casting technique of casting directly into the target shape minimizes the solidification volume, and by preheating the mold, suppresses segregation of intermetallic compounds and suppresses variations in magnetic properties. is there. The target of the present invention can be suppressed to within 2%, more preferably within 1%, preferably by the application of the precision casting method, when evaluated by the variation of the leakage magnetic flux density.

In the present invention, another advantage of applying the precision casting method is that the amount of expensive Co, 4A, 5A or other additive element can be minimized. That is, in the precision casting method, since the product is cast so as to have substantially the target shape, the product can be obtained by processing to the extent of removing the deteriorated layer on the surface. That is, in the conventional casting target cut out from the ingot, a large amount of residual material is generated, but this is eliminated. In particular, although a target containing a large amount of Pt has recently been used, Pt is particularly expensive, and the present invention, which hardly generates residual material, is advantageous in terms of cost. In addition, in the case of a target which needs to be hollowed out, such as a target having a different shape such as a donut shape, it is advantageous in terms of reducing residual material.

In the present invention, the compositional range is not specified because the solid solubility limit of Co of the group 4A or 5A element to Co differs depending on the element. For example, Ta, V, Ti
Are approximately 4.5 at% and 22.4 at%, respectively.
% And 14 at%. Further, the effect of the present invention can be more clearly obtained when the group 4A or group 5A is contained by 0.5 at% or more than the solid solubility limit described above. Further, the composition of the target of the present invention contains Cr at 15 at% or less and N
It is desirable to contain i at 20 at% or less and Pt at 30 at% or less.

In order to obtain the target of the present invention, specifically, Co is mainly used and forms an intermetallic compound with Co.
An alloy melt containing an element of group A or group 5A exceeding the solid solubility limit in the solidified state is prepared at 500 to 1100 ° C.
The molten metal is poured into a precision casting mold having a target outer shape as a preheated cavity. Casting into a preheated mold in advance in this way improves the flowability of the molten metal during pouring and suppresses the variation in the solidification rate after pouring, so that a more uniform structure can be obtained. A ceramic mold can be used as the mold. The preheating temperature is 50
If the temperature is lower than 0 ° C., the effect is small.
１1100 ° C.

The temperature of the molten metal to be poured is 13
50 ° C. or higher is preferred. If it is less than this, fluidity of the molten metal is lost and casting becomes difficult. Also 1500
If the temperature exceeds ℃, it takes a long time to solidify and segregation easily occurs.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in the schematic view of FIG. 1, a precision shell having a runner 3 extending from a sprue cup 4 as a trunk, and having a plurality of branch gates 2 having a cavity 1 having a target external shape formed in a plurality of spouts 2. Using the casting mold, casting to the targets shown in Table 1 was performed. The cavity size of the target portion is φ130 × 8 t (mm) and a shape having a cylindrical through hole of 47 (mm) in the center. The casting conditions are a molten metal temperature of 1420 ° C. at the start of pouring and a ceramic shell heating temperature of 1000 ° C. After casting, the sprue was cut, and the altered layer on the surface was removed to obtain a doughnut-shaped target having a diameter of 127 x 6.35 t (mm) and a cylindrical hole of 50 mm in the center. As a comparative example, casting was performed using an iron mold provided with a mold part of φ160 × 40 and a feeder part of φ100 × 30 (mm), and finished to the same target dimensions as in the present invention example by machining.

In order to measure the magnetic properties of the target, U
The leakage magnetic flux density of the target material was measured by placing a Gauss meter probe facing the U-shaped magnet and inserting the target into the gap between the magnet and the probe. U
The distance between the U-shaped magnet and the Gauss meter was adjusted so that the magnetic flux density without a target inserted was 30 mT. The measurement of the leakage magnetic flux was performed at intervals of 30 degrees at a circumferential position having a diameter of 90 mm. The results are shown in Table 1.

[0018]

[Table 1]

As shown in Table 1, the target material of the present invention has less variation in leakage magnetic flux density as compared with a normal casting target. This is considered to be because the temperature distribution occurred during solidification because the mold was not heated in a normal casting target. In order to evaluate the effect on the erosion of the target during magnetron sputtering with respect to the dispersion of the actual leakage magnetic flux distribution,
Sputtering was performed with a magnetron sputtering apparatus having a circular magnet disposed on the back. As a result, the erosion region 5 in the target of the present invention showed a circular erosion region along the shape of the magnet as shown in FIG. 2, but the target of the comparative example showed the erosion region 5 as shown in FIG. Is shifted up to about 3mm from the circle,
Erosion was progressing abnormally. The abnormal progression of the ash confirmed in the comparative example is undesirable because it leads to an increase in abnormal discharge during sputtering and a shortened life of the target.

[0020]

According to the present invention, variations in the magnetic properties of the target itself due to the formation of the compound can be suppressed, and the life of the expensive Co-based target can be extended. Further, by applying the precision casting method, the generation of residual material is small, and the cost can be significantly reduced. Therefore, the present invention can be an indispensable technique particularly for a Co-based target that often adds an effective additive element such as Pt.

[Brief description of the drawings]

FIG. 1 is a view showing an example of a precision casting mold used for manufacturing a target of the present invention.

FIG. 2 is a diagram showing an erosion state of a target of the present invention.

FIG. 3 is a diagram showing an erosion state of a target of a comparative example.

[Explanation of symbols]

1. Cavity, 2. Gate, 3 Runner, 4. Gate cup, 5. Erosion area

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Kawakami 2107-2 Yasugi-cho, Yasugi City, Shimane Prefecture Inside the Yasugi Plant, Hitachi Metals, Ltd. (72) Inventor Junji Kurumi 1240-2 Iijimacho, Yasugi City, Shimane Prefecture Yasu Corporation Inside Hitachi Metals Precision

Claims (4)

[Claims] 1. A target mainly composed of Co,
A Co-based casting target comprising an element of Group 4A or Group 5A forming an intermetallic compound with Co in excess of the solid solubility limit and being substantially precision-cast into a target shape. 2. The Co-based casting target according to claim 1, comprising Pt. 3. The Co-based casting target according to claim 1, wherein the variation of the leakage magnetic flux density measured on the sputtering surface of the target is within 2%. 4. An alloy melt containing Co as a main component and containing an amount of a Group 4A or Group 5A element that forms an intermetallic compound with Co in an amount exceeding the solid solubility limit in a solidified state, at a melt temperature of 1350 to 1500 ° C. A method of manufacturing a Co-based casting target, comprising pouring into a precision casting mold having a target external shape as a cavity preheated to 500 to 1100 ° C.