JP4968449B2 - Sputtering target for forming high-density magnetic recording medium film with less generation of particles - Google Patents

Description

  The present invention relates to a magnetic recording film applied to a high-density magnetic recording medium of a hard disk, particularly a high-density magnetic recording medium film generation with less particles for forming a magnetic recording film used for a medium of a high-density perpendicular magnetic recording system. The present invention relates to a sputtering target for use.

Hard disk devices are generally used as external recording devices such as computers and digital home appliances, and further improvement in recording density is required. Therefore, in recent years, attention has been paid to a high-density magnetic recording method capable of realizing ultra-high density recording. Unlike the conventional in-plane recording system, this high-density magnetic recording system is said to have a stable recording magnetization as the density increases in principle, and has already been put into practical use. A CoCrPt—Ta ₂ O ₅ granular magnetic recording film is used as one of the materials applied to the recording layer of this high density magnetic recording hard disk medium, and the CoCrPt—Ta ₂ O ₅ granular magnetic recording film is made of Cr and It is known to produce by a magnetron sputtering method using a sputtering target having a mixed phase of a Co-based sintered alloy phase containing Pt and a tantalum oxide phase (see, for example, Patent Document 1).
This sputtering target is prepared by mixing and mixing a commercially available Co-based alloy powder containing Cr and Pt or a Co-based alloy powder containing Cr and Pt prepared by rapid solidification and a tantalum oxide powder, followed by vacuum hot pressing or hot static It can be considered to be produced by hydraulic pressing.
JP 2006-24346 A

  However, a conventional sputtering target for forming a magnetic recording medium film in which tantalum oxide is uniformly dispersed in a base material generates many particles when performing magnetron sputtering. Was demanded.

Accordingly, the present inventors have studied to obtain a sputtering target for forming a magnetic recording medium film with less generation of particles when performing magnetron sputtering. as a result,
(A) Oxygen: 2 to 40 atomic%, Cr: 5 to 20 atomic%, Pt: 5 to 25 atomic%, Ta: 0.5 to 15 atomic%, the balance: component composition consisting of Co and inevitable impurities In a sputtering target for forming a high-density magnetic recording medium film made of a sintered body having an oxide, a target in which oxide particles composed of Cr, Ta, and oxygen are uniformly dispersed in the substrate has a significantly smaller generation of particles during magnetron sputtering. (B) The oxide particles composed of Cr, Ta and oxygen contain Cr: 12 to 20 atomic% and Ta: 14 to 22 atomic% when the total of Cr, Ta and oxygen is 100 atomic%. , The remainder is oxide particles made of oxygen,
(C) Finer oxide particles composed of Cr, Ta, and oxygen that are uniformly dispersed in the substrate are preferably finer, and have an absolute maximum length (maximum distance between any two points on the particle contour). The number of oxide particles exceeding 25 μm preferably has a particle size distribution of 5% or less.
(D) The high-density magnetic recording medium film-forming sputtering target is preferably such that the density of the sintered body is closer to the theoretical density, more preferably a sintered body having a relative density of 95% or more. I gained knowledge.

This invention has been made based on such knowledge,
(1) Oxygen: 2 to 40 atomic%, Cr: 5 to 20 atomic%, Pt: 5 to 25 atomic%, Ta: 0.5 to 15 atomic%, the balance: component composition consisting of Co and inevitable impurities A target having a structure in which oxide particles composed of Cr, Ta, and oxygen are uniformly dispersed in the target substrate, and the oxide particles composed of Cr, Ta, and oxygen are When the total of Cr, Ta and oxygen is 100 atomic%, Cr: 12 to 20 atomic%, Ta: 14 to 22 atomic%, and the rest is oxide particles consisting of oxygen. Sputtering target for forming a density magnetic recording medium film,
(2) The oxide particles comprising Cr, Ta, and oxygen have a particle size distribution in which the number of oxide particles having an absolute maximum length exceeding 25 μm is 5% or less, and high density magnetic recording with less generation of particles according to (1). Sputtering target for medium film formation,
(3) The sintered body is characterized by the sputtering target for forming a high-density magnetic recording medium film with less generation of particles according to (1) or (2), wherein the sintered body has a relative density of 95% or more. Is.
The relative density of the sintered body described in (3) above is a value obtained by dividing the bulk density of the sintered body by the theoretical density and multiplying by 100. The theoretical density of the sintered body is uniform for each element and molecule. It is a value calculated as follows assuming that no reaction or diffusion occurs. That is, when the composition of the sintered body is expressed as Co _a Cr _b Pt _c (Ta ₂ O ₅ ) _d (a, b, c, d are weight%), the theoretical density ρ _{t of the} sintered body is
ρ _t = 100 / (a / ρ _Co + b / ρ _Cr + c / ρ _Pt + d / ρ _Ta 2 _{O 5} ) (where ρ _Co = 8.92, ρ _Cr = 7.19, ρ _Pt = 21.45, ρ _Ta2O5 = 4.25, these are the theoretical densities of each element and oxide).
Therefore, the relative density R of the sintered body is obtained by R = ρ / ρ _t × 100 from the bulk density ρ and the theoretical density ρ _{t of the} sintered body.

In order to manufacture the sputtering target for forming a high density magnetic recording medium film with less particle generation according to the present invention, Co powder, Pt powder, Cr powder and Ta ₂ O ₅ powder are prepared as raw powders. Part and Ta ₂ O ₅ powder were mixed by a ball mill, and the resulting mixed powder was heat treated in the atmosphere at a temperature of 800 to 1300 ° C. and then pulverized to make the total of Cr, Ta and oxygen 100 atomic%. In this case, an oxide powder containing Cr: 12 to 20 atomic% and Ta: 14 to 22 atomic% and the balance being oxygen is prepared, and Co powder, Pt powder and Cr powder are added to the oxide powder with oxygen: 2 to 2 It contains 40 atomic%, Cr: 5 to 20 atomic%, Pt: 5 to 25 atomic%, Ta: 0.5 to 15 atomic%, and the balance: a component composition consisting of Co and inevitable impurities. Were mixed together to prepare a mixed powder, the mixed powder obtained temperature: 1000 to 1250 ° C., pressure: 150 MPa or more, can be prepared by holding over 1 hour.

The content of Cr contained in the oxide particles composed of Cr, Ta and oxygen uniformly dispersed in the base material of the sputtering target for forming a high density magnetic recording medium film with less generation of particles according to the present invention is defined as Cr, Ta and oxygen. The reason why Cr is 12 to 20 atomic% when the total amount is 100 atomic% is not preferable because the number of particles generated is increased when Cr is less than 12 atomic%, whereas it is obtained when Cr exceeds 20 atomic%. This is because the magnetic properties of the sputtered film deteriorate, which is not preferable.
The reason why Ta is set to 14 to 22 atomic% is not preferable when Ta is less than 14 atomic% because the magnetic properties of the sputtering film are deteriorated. On the other hand, when Ta exceeds 22 atomic%, the number of particles generated is large. This is because it is not preferable.
The reason why the generation of particles is reduced by changing the oxide particles dispersed in the target from Ta ₂ O ₅ to an oxide containing Cr and Ta is that the oxide particles contain Cr, so It is presumed that the adhesion with the Co alloy contained is improved and the oxide particles are less likely to be peeled off and dropped off during sputtering.
The oxide particles composed of Cr, Ta and oxygen uniformly dispersed in the target substrate are preferably dispersed as fine particles, and the number of oxide particles having an absolute maximum length exceeding 25 μm is 5% or less. Preferably there is. This is because if the number of oxide particles having an absolute maximum length exceeding 25 μm exceeds 5%, the number of oxide particles having a large particle diameter increases and the generation of particles increases, which is not preferable.

In addition, as a component composition of the sputtering target for forming a high-density magnetic recording medium film, oxygen: 2 to 40 atomic%, Cr: 5 to 20 atomic%, Pt: 5 to 25 atomic%, Ta: 0.5 to 15 atomic% Since it is a known component composition to have a component composition consisting of Co and the balance: Co and unavoidable impurities, description of the reason for limitation will be omitted.

  The sputtering target for forming a high-density magnetic recording medium film according to the present invention reduces the generation of particles during magnetron sputtering, thereby reducing the number of defective high-density magnetic recording medium films and reducing the cost. It can greatly contribute to the development of industries such as computers and digital home appliances.

Example Commercially available 50% particle size: 6 μm Co powder, 50% particle size: 20 μm Pt powder, 50% particle size: 30 μm Cr powder, 50% particle size: 3 μm Ta ₂ O ₅ powder as raw material powder Prepared.
Furthermore, a part of the Cr powder and Ta ₂ O ₅ powder were mixed with a ball mill, and the obtained mixed powder was heat treated at 1000 ° C. for 24 hours in the atmosphere, and then further pulverized. Oxide powders A to K having the component compositions and particle sizes shown in Table 1 were prepared and prepared.

These prepared raw material powders were blended in the proportions shown in Table 2, and the obtained blended powder was put into a 10-liter container together with zirconium oxide balls, and the atmosphere of this container was replaced with Ar gas, and then the container was sealed. . This container is rotated by a ball mill for 16 hours and mixed to prepare a mixed powder, and this mixed powder is filled in a vacuum hot press apparatus, and is maintained in a vacuum atmosphere at a temperature of 1200 ° C., a pressure of 15 MPa, and a 3 hour holding condition. A plate-like hot press body having the component composition shown in Table 2 was produced by vacuum hot pressing.
The plate-like hot press body was cut into a plate having a diameter of 152.4 mm and a thickness of 5 mm, and then joined to a copper backing plate to prepare the inventive targets 1 to 10 and comparative targets 1 to 3.

Conventional Example Further, Co powder, Pt powder, Cr powder, and Ta ₂ O ₅ powder prepared in the examples were blended in the proportions shown in Table 2, and put into a 10-liter container together with zirconium oxide balls. After replacing the atmosphere with Ar gas, the container was sealed. The container was rotated by a ball mill for 16 hours and mixed to prepare a mixed powder. The mixed powder thus obtained was filled in a vacuum hot press apparatus, and the component composition shown in Table 2 was obtained by vacuum hot pressing in a vacuum atmosphere under conditions of temperature: 1200 ° C., pressure: 15 MPa, and 3 hours. A plate-like hot press body having a thickness of 10 was produced, and the relative density of the plate-like hot press body was measured. The results are shown in Table 2. Next, this plate-like hot press body was cut into a plate having a diameter of 152.4 mm and a thickness of 5 mm, and then joined to a copper backing plate to produce a conventional target.

The relative densities (= bulk density / theoretical density × 100) of the inventive targets 1 to 10, the comparative targets 1 to 3 and the conventional target thus prepared were measured, and the results are shown in Table 2. Further, the present invention targets 1 to 10, the comparative targets 1 to 3 and a part of the conventional target are cut, embedded in resin, polished, and the polished surface is observed with a scanning electron microscope (SEM). Take 10 SEM photographs (COMPO images) at random from the cross section at a magnification of 1000 times, and import these SEM photographs as bitmap format image files into a personal computer so as not to degrade the image quality. The absolute maximum length was measured for all the oxide particles that were read and binarized by the processing software (Mitani Corporation, Win Roof) and black in the SEM photograph. Care was taken that the binarization conditions were as close as possible to the shape of the original oxide particles. For calibration of the length at the time of measurement, a scale bar of an SEM image was used. The absolute maximum lengths of all the measured oxide particles were statistically processed and the proportion of particles of 25 μm or more was measured. The results are shown in Table 2.
Further, the component composition of the oxide particles uniformly dispersed in the substrate was subjected to field emission EPMA (JXA-8500F manufactured by JEOL Ltd.), acceleration voltage: 15 kV, irradiation current: 5 × 10 ⁻⁸ A, analysis spot diameter The composition quantitative analysis of Cr, Ta, and O was performed under the condition of setting value: 0 (substantial electron beam diameter is about 0.5 μm), and the results are shown in Table 2.

These inventive targets 1 to 10, comparative targets 1 to 3 and conventional targets are mounted on a commercially available sputtering apparatus,
Ultimate vacuum: <5 × 10 −5 Pa,
Power: DC 800W,
Ar gas: 6.0 Pa,
Target-substrate distance: 60 mm,
Substrate heating: None,
Pre-sputtering is performed for 5 hours under the conditions described above, and after removing the surface processing layer on the target surface, the chamber is once opened to clean the chamber members such as the deposition prevention plate, and then the vacuum is drawn until the above vacuum degree is reached again. Was done. After evacuation, pre-sputtering was performed for 30 minutes to remove the atmospheric adsorption components and the metal oxide layer on the target surface, and then a high-density magnetic recording medium film was formed on a 4-inch Si wafer. After the film formation, the number of particles of 1 μm or more adhering to the wafer surface was measured with a commercially available foreign substance inspection apparatus, and the results are shown in Table 2.

  From the results shown in Table 2, it can be seen that the inventive targets 1 to 10 generate significantly fewer particles during sputtering than the conventional target. However, it can be seen that the target produced by Comparative Methods 1 to 3 under conditions outside the scope of the present invention is not preferable because the generation of particles is slightly increased.

Claims (3)

Oxygen: 2 to 40 atom%, Cr: 5 to 20 atom%, Pt: 5 to 25 atom%, Ta: 0.5 to 15 atom%, and the balance: a component composition comprising Co and inevitable impurities In the target composed of a solid body, the target substrate has a structure in which oxide particles composed of Cr, Ta, and oxygen are uniformly dispersed. The oxide particles composed of Cr, Ta, and oxygen include When the total amount of oxygen is 100 atomic%, Cr: 12 to 20 atomic%, Ta: 14 to 22 atomic%, and the rest is oxide particles composed of oxygen. A sputtering target for forming a density magnetic recording medium film. 2. The high density magnetic material with less particle generation according to claim 1, wherein the oxide particles comprising Cr, Ta and oxygen have a particle size distribution in which the number of oxide particles having an absolute maximum length exceeding 25 μm is 5% or less. A sputtering target for forming a recording medium film. 3. The sputtering target for forming a high density magnetic recording medium film with less generation of particles according to claim 1, wherein the sintered body is a sintered body having a relative density of 95% or more.