JP2000038660A - CoPt SPUTTERING TARGET, ITS PRODUCTION AND CoPt-MAGNETIC RECORDING MEDIUM - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CoPt sputtering target, by which the formation of element distribution in the plane of the medium can be suppressed when it is used in the formation of film, the method for production of the same, and the magnet recording medium. SOLUTION: A CoPt sputtering target containing Co as a main component contains elements selected from Ni and the elements of groups IVa, Va and VIa in addition to Pt, and gives a X-ray diffraction pattern, wherein the diffraction peaks show that the elements in the target are each present as a substantially metallic element single form. The magnetic recording medium having little dispersion of the composition in the plane can be obtained by sputtering the target. The target is produced, e.g. by low-temp. sintering a compact composed of Co-powder, Pt-powder and elemental simple substances selected from Ni and the elements of groups IVa, Va and VIa at 400-1,000 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sputtering target used for forming a CoPt-based alloy which is a recording layer of a magnetic recording medium, a method of manufacturing the same, and a CoPt-based magnetic recording medium.

[0002]

2. Description of the Related Art In recent years, the amount of information processed on a computer has increased with the development of the information society, and it has become necessary to record and reproduce information at a higher density than in the past.
Currently, a hard disk, which is an external storage device of a personal computer, has an underlayer on a substrate such as an Al alloy or glass,
The mainstream is a multilayer structure having a recording layer. Recent magnetic recording media require higher coercive force, higher squareness ratio, and lower noise in order to perform high-density recording as compared to conventional magnetic recording media. Pt that has the effect of increasing the coercive force of the recording layer
CoPt-based alloys typified by CoCrPt and CoCrTaPt, to which Cr is added, are becoming mainstream.

The above-mentioned recording layer is formed by a magnetron sputtering method using an alloy target. In general, when magnetron sputtering is performed using a ferromagnetic target such as the above-mentioned Co alloy, a target is used. The magnetic flux from the magnet arranged on the back surface hardly leaks to the surface of the target, the plasma is locally generated, and the target is partially consumed, so that the use efficiency is reduced.
For this reason, various methods have been proposed to improve the use efficiency of the target.

[0004] For example, Japanese Patent Publication No. 2-49384 discloses a method in which strain is imparted to the inside of a Co alloy by cold working to change the crystal structure, thereby improving magnetic properties and improving use efficiency. JP-A-8-25270 discloses a method of changing the crystal structure by subjecting a Co-based alloy target to heat treatment after rolling or the like, and lowering the magnetic permeability of the target by precipitating an intermetallic compound phase at crystal grain boundaries. Is disclosed.

There is another problem that the magnetic properties of the film become non-uniform due to the disturbance of the leakage magnetic flux due to the non-uniformity of the target structure. In particular, in the case of an alloy containing a large amount of elements having different atomic weights, such as a CoCrPtTa alloy target, casting segregation is likely to occur during melt casting. Further, it is difficult to homogenize the target structure because the plastic workability deteriorates due to the formation of the intermetallic compound.

Accordingly, various methods have been proposed for the purpose of making the target structure uniform. For example, JP-A-5-8
No. 6456 discloses a method in which a melted ingot is packed, heat treated, HIP (hot isostatic pressing) is performed, and further rolling is performed.
o as the main component, 5-20 atomic% of Cr and 10-55 Pt
Atomic%, Ni and Ta are 1 to 15 atomic%, and rare earth element is 1
It is disclosed that by performing forging, hot rolling, and cold rolling after melting and casting with an alloy containing 0 to 1500 ppm, it is possible to homogenize the structure and improve the magnetic permeability.

In Japanese Patent Application Laid-Open No. 5-247641, Co is mainly used, Cr is 4 to 18 atomic%, and Pt is 0.5 to 16 atomic%.
There is disclosed a method of homogenizing a target structure by sintering an alloy powder containing 0.1 to 8 atomic% of atomic%, Nb, Ta or the like. As described above, the improvements that have conventionally been made to Co-based alloy targets have been limited to those aimed at lowering the magnetic permeability and improving the uniformity of the target structure in order to improve the use efficiency of the target.

[0008]

SUMMARY OF THE INVENTION The present inventor has developed a stationary facing type sputtering apparatus which forms a film by arranging a circular substrate at a position facing a circular cathode, which is a typical structure of a magnetic disk manufacturing apparatus. The coercive force of the film changes in the radial direction of the substrate during the evaluation of the magnetic properties of the film formed using the above-mentioned melting casting method or a CoPt-based alloy target alloyed by sintering the alloy powder. Faced a previously unknown problem. This problem is a serious problem that seriously affects the recording / reproducing characteristics of the magnetic disk.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an object to provide a magnetic recording medium having a recording layer having high uniformity in film composition distribution and excellent recording and reproduction characteristics, a CoPt-based target for forming the same, and Production method and Co
An object of the present invention is to provide a Pt-based magnetic recording medium.

[0010]

As a result of a detailed investigation on this problem, the present inventors have found that the film composition changes continuously in the radial direction of the substrate, and particularly as the distance from the target erosion portion increases. It was found that the amount of Pt in the film was relatively high. This tendency was found to correspond to a change in the coercive force of the film. Next, the present inventor conducted a detailed study on the element distribution of the film by changing the target structure in order to solve the above-described problem. As a result, the non-uniformity of the element distribution of the film was found to be a target having an alloyed structure. It was found to be a unique problem. It was also found that homogenization of the target alloy structure did not improve at all. Based on these findings, the present inventor makes the individual target constituent elements into a single state without alloying or a structure joined in a state close to it,
The inventors have found that the element distribution of the film is made uniform, and have reached the present invention.

That is, the present invention is as follows. Co
A target material mainly composed of Ni, an element selected from the group consisting of Ni, group 4a, group 5a and group 6a, and Pt
And a CoPt-based sputtering target showing that the diffraction peak observed in the X-ray diffraction pattern is substantially due to a single metal element.

The structure of the target of the present invention which can make the element distribution of the film uniform is a target material mainly composed of Co, and is substantially composed of Ni, Group 4a element, Group 5a element and Group 6a element. A phase consisting essentially of an element selected from the group consisting of: a phase consisting essentially of Pt; and a phase consisting essentially of Co, having a structure in which the layer thickness is substantially 50 μm or less at each boundary. It is desirable that a bonding phase be formed.

In the present invention, Ni, a 4a element, 5
The maximum major axis length of each of the phase composed of a simple substance selected from the group a element and the group 6a element and the phase composed of Pt is substantially 50.
It is desirable that the thickness be 0 μm or less. Also, a 4a group element,
As a phase composed of a simple substance selected from the group 5a element and the group 6a element, a Cr phase and a Ta phase are preferable. In this case, the preferred composition of the present invention has a Cr content of 0.1 to 25 atomic%, a Pt content of 0.1 to 20 atomic%, and a Ta content of 0.1 to 15 atomic%.

The above-described target of the present invention is, for example, C
o powder, Pt powder and Ni, Group 4a element, Group 5a element,
It can be obtained by weighing and mixing powders composed of elemental elements selected from Group 6a elements and sintering them at a temperature of 400 to 1000 ° C.

By using the target of the present invention, a novel CoPt-based magnetic recording medium can be obtained in which the difference in the analysis value of the Pt content measured in the radial direction of the disk is ± 10% or less.

[0016]

An important feature of the target of the present invention is that the individual elements constituting the target exist in a single state without forming an alloy such as a solid solution or an intermetallic compound, or the target constitutes a target. In this case, the diffusion bonding layer, which is the boundary layer of each phase, has a thickness of substantially 50 μm or less.

In this way, by preventing the formation of an alloy as much as possible, it is possible to suppress the occurrence of element distribution in the plane of the medium when the film is formed. Although the reason for this is unknown, the following is conceivable. First, when a single metal exists, the direction of the sputtered particles sputtered at the time of sputtering is approximated as a metal element, so that an in-plane distribution hardly occurs. On the other hand, when alloyed, due to the formation of covalent bond compounds and lattice distortion, the difference in the direction of sputtered particles as sputtered particles between the constituent elements becomes larger than in the case where the metal element exists alone, and the element becomes in-plane. It is considered that distribution has occurred.

It is preferable to reduce as much as possible the alloy phase which causes the element distribution of the film composition. That is, if each phase is alloyed by diffusion or reaction, the effect of the present invention cannot be obtained. Therefore, it is preferable to minimize the mixing ratio of the elements of the other phases into the individual phases. The thickness of the diffusion bonding layer formed at the boundary between the individual phases is preferably as thin as possible, and may be substantially 50 μm or less, preferably 30 μm or less, and more preferably 10 μm or less. Further, if the phase composed of an element other than Co has a large particle size, the surface irregularities become severe as the sputtering time elapses, and the change in the film composition accompanying the progress of erosion increases. Therefore, the maximum major axis of the phase composed of an element other than Co is preferably finer, preferably 500 μm or less, and more preferably 100 μm or less.

The composition of the target is mainly composed of Co, which basically secures magnetic properties, and has an increased magnetic anisotropy.
It is essential to add Pt to improve the coercive force. Further, Ni, a 4a group element,
An element selected from a group a element and a group 6a element is contained.
Ni has the effect of improving the coercive force of the film and the magnetic properties, and can be added. Group 4a element, 5a
Group elements and Group 6a elements include film grain refinement and segregation structure,
This is because there is an effect of improving the crystal orientation and a large effect of improving the magnetic characteristics of the recording layer. In particular, Cr and Ta are more preferable because of their high effect of improving the magnetic properties of the film. In this case, the Cr content is 0.1 to 25 atomic%, the Pt content is 0.1 to 20 atomic%, and the Ta content is 0.1 to 15 atomic%.
It is preferable that The reason is that if it is out of this range, the magnetic properties of the film deteriorate. In addition, oxygen contained in the target is preferably reduced as much as possible because it causes deterioration of the magnetic properties of the film.
00 ppm or less, more preferably 800 ppm
It is desirable to make the following.

The target of the present invention can be manufactured by, for example, a powder sintering method. As a raw material powder, a pure metal powder made into a powder by a method such as a mechanical pulverization method, a gas atomization method, or an arc melt method is used, and the powder is weighed to have a desired composition and mixed.

This mixed powder is sintered at 400 to 1000 ° C. The sintering temperature is determined in this way because diffusion is not enough at 400 ° C or less, voids remain even after sintering and cause abnormal discharge. This is because the ratio of the phases performed increases. In particular, the sintering temperature is preferably set to the lower limit at which a necessary and sufficient sintered body density can be obtained. In addition, by performing pressure sintering such as HIP, hot pressing, and hot extrusion during sintering, a sintered body having fewer defects such as voids in the target structure can be obtained as compared with simple sintering.

By using the target according to the present invention, it is possible to obtain a magnetic recording medium, for example, a novel magnetic recording medium having a reduced element distribution on the recording surface of a hard disk. Specifically, it is possible to provide a CoPt-based magnetic recording medium in which the difference in the analysis value of the Pt content measured in the radial direction of the disk is ± 10% or less, preferably ± 5% or less.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to embodiments. (Example 1) Pure metal powder having a purity of 99.9% or more having the specifications shown in Table 1 was weighed so as to have a desired composition, and mixed by a rocking mixer for 30 minutes. These mixed powders are filled in a soft iron HIP can, and while the HIP can is heated at 400 ° C. or more, the oil diffusion pump is used to evacuate to a pressure of 10−1 Pa or less, followed by degassing and sealing. Pressure sintering was performed under the conditions shown in Table 1. Next, the HIP can was removed by machining to obtain a target material of the present invention of φ100 × 4t.

The microstructure of Sample 1 shown in FIG. 1 was a structure in which phases of Cr, Pt, and Ta were dispersed in a Co matrix, and a diffusion phase of a maximum of 20 μm was formed at the boundary between the phases. In addition, similar to the X-ray diffraction pattern of the target of Sample 1 shown in FIG. Although an unidentifiable peak was confirmed at the left end of the chart in FIG. 2, the intensity was very small, indicating that the chart shown in FIG. 2 was substantially a simple metal. When the same structure examination as that of the sample 1 was performed on the target of the present invention, each was substantially a simple metal. That is, although a diffusion bonding layer was formed at the boundary between the phases, it was confirmed that the diffusion bonding layer was minute and each constituent element was present in a single-phase state.

[0025]

[Table 1]

(Comparative Example) Co, Cr, Ta, and Pt raw materials were weighed so as to have a desired composition, vacuum-melted to form an alloy ingot, and hot-rolled to obtain a plate material, which was then machined. Thus, a target material of φ100 × 4t was obtained. In the X-ray diffraction patterns of these targets, diffraction peaks due to the matrix mainly composed of Co and the Co-Ta intermetallic compound were confirmed, and no peaks matching Cr alone, Ta alone, or Pt alone were found, and the alloy was completely alloyed. Has been confirmed. Further, pure Co powder and pure C powder
After r powder, pure Ta powder, and pure Pt powder were weighed and filled in a mixed HIP can, a target having a HIP temperature of 1250 ° C was prepared. In the microstructure of this target, the layer thickness of the diffusion bonding layer is increased as compared with the above-mentioned present invention, and Co is included in the X-ray diffraction pattern in addition to the peaks corresponding to Cr alone, Ta alone, and Pt alone. A peak considered to be an intermetallic compound was observed, and it was confirmed that alloying of a part of the target structure was progressing.

(Evaluation of Film Deposition) The targets of the present invention and the comparative example described above were mounted on a sputtering apparatus having the substrate and target arrangement shown in FIG. 3 and evacuated to 10 −4 Pa or less. Introduce gas to 0.3Pa,
A power of 500 W was applied from a DC power supply to form a thin film having a thickness of 1 μm on the slide glass. Place this slide glass on the substrate edge (X = 50 m) from the substrate center (X = 0 mm).
The film was cut at 10 mm intervals until m), and the film composition was analyzed by EPMA. Next, for each sample, the film composition analysis value at a position dmm from the center of the substrate was determined for each element by C _A (X
= D) (atomic%), the deviation from the film composition analysis value at the center of the substrate (X = 0 mm) was evaluated by the following equation. Shift amount _{(%) = 100 × {C} A (X = d) -C A (X = 0)}
÷ C _A (X = 0) From the difference between the maximum value and the minimum value of the shift amount of each element shown in Table 2, the shift amount of Pt is particularly large in the film formed using the target of the comparative example. On the other hand, it can be seen that the films formed using the target of the present invention have a deviation of ± 10% or less for all elements.

[0028]

[Table 2]

The variation in the radial direction of the substrate between the element according to the present invention and the target of the comparative example in the radial direction of the substrate is typically as shown in FIGS. 4 and 5, respectively. In the film formed by using the target of the present invention, in particular, the amount of Pt in the film outside the erosion portion (X = 30 mm) is increased, while all the elements in the film are formed. It can be seen that the distribution is nearly uniform.

[0030]

According to the present invention, the CoP obtained by the conventional manufacturing method is used.
This makes it possible to solve the non-uniformity of the film composition, which was a problem of the magnetic recording medium formed by the t-type target, and is an indispensable technique for improving the quality of the magnetic recording medium.

[Brief description of the drawings]

FIG. 1 is an optical micrograph of a metal microstructure of Sample 1 in an example of the present invention.

FIG. 2 is a view showing an X-ray diffraction pattern of Sample 1 in an example of the present invention.

FIG. 3 is a schematic diagram showing a configuration of a sputtering apparatus used in an embodiment of the present invention.

FIG. 4 is a diagram showing a film composition distribution of a CoCrTaPt film formed using a target sample 1 according to the present invention.

FIG. 5 is a diagram showing a film composition distribution of a CoCrTaPt film formed using a target sample 6 according to a comparative example.

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Claims (7)

[Claims] 1. A target material mainly composed of Co, which contains Ni, an element selected from group 4a, group 5a, and group 6a, and Pt, and a diffraction peak confirmed in an X-ray diffraction pattern. Is substantially a single metal element. 2. A target material mainly composed of Co, which is a phase substantially composed of a single element selected from Ni, a group 4a element, a group 5a element and a group 6a element, a phase substantially composed of Pt, and The phase substantially consisting of Co has a structure joined to each other, and has a layer thickness of substantially 50 at each boundary.
A CoPt-based sputtering target, wherein a diffusion bonding phase of not more than μm is formed. 3. The maximum major axis of a phase substantially composed of a single element selected from Ni, a group 4a element, a group 5a element, and a group 6a element, and a phase substantially composed of Pt, is substantially 500 μm or less. C according to claim 1 or 2, characterized in that
oPt-based sputtering target. 4. The CoPt-based sputtering target according to claim 3, wherein the phase composed of a simple substance selected from the group 4a element, the group 5a element and the group 6a element is a Cr phase and a Ta phase. 5. A Cr content of 0.1 to 25 at%, Pt
Content is 0.1 to 20 atomic%, Ta content is 0.1 to 1
5. The CoP according to claim 4, wherein the content is 5 atomic%.
t-based sputtering target. 6. A method comprising weighing and mixing a Co powder, a Pt powder, and a powder composed of a single element selected from the group consisting of Ni, Group 4a, Group 5a and Group 6a, and sintering at a temperature of 400 to 1000 ° C. Of producing a CoPt-based sputtering target. 7. A CoPt-based magnetic recording medium characterized in that the difference in the analysis value of the Pt content measured in the radial direction of the disk is ± 10% or less.