CN112739846A

CN112739846A - Sputtering target and powder for producing sputtering target

Info

Publication number: CN112739846A
Application number: CN201980060775.9A
Authority: CN
Inventors: 岩渊靖幸; 佐藤敦; 下宿彰; 清水正义
Original assignee: JX Nippon Mining and Metals Corp
Current assignee: JX Nippon Mining and Metals Corp
Priority date: 2018-09-25
Filing date: 2019-05-16
Publication date: 2021-04-30
Also published as: MY197929A; TW202012666A; TWI727334B; WO2020066114A1; SG11202102759VA; JPWO2020066114A1; JP7072664B2

Abstract

The invention provides a sputtering target containing Ru and boron. The sputtering target comprises Ru as a main component and has a melting point ratio of B₂O₃High and boron-containing composite oxides.

Description

Sputtering target and powder for producing sputtering target

Technical Field

The present invention relates to a sputtering target and a powder for producing the sputtering target. And more particularly, to a Ru-containing sputtering target and a powder for manufacturing the sputtering target.

Background

In the field of magnetic recording represented by hard disk drives, as a material of a magnetic thin film responsible for recording, a material based on a ferromagnetic metal Co, Fe, or Ni is used. For example, a ferromagnetic alloy of Co-Cr system or Co-Cr-Pt system containing Co as a main component is used for a recording layer of a hard disk adopting an in-plane magnetic recording system.

In recent years, high capacity magnetic recording in hard disk drives and the like has been advanced. In order to achieve such a high capacity, it is important to improve the separability of crystal grains in the magnetic recording layer, thereby reducing the interaction between the crystal grains.

Patent document 1 discloses an underlayer of a Ru-xCoO alloy. Patent document 1 discloses that the second underlayer 150b has an effect of forming grain boundaries of oxides to promote the separation of particles, and also to improve the crystal orientation of Ru constituting the underlayer 150 and the main recording layer 160.

Patent document 2 discloses a perpendicular magnetic recording medium including a nonmagnetic intermediate layer and a magnetic layer. In addition, patent document 2 discloses that Ru is used for the 1 st nonmagnetic intermediate layer, and a CoCr alloy is used for the 2 nd nonmagnetic intermediate layer.

Patent document 3 discloses a perpendicular magnetic recording medium including a perpendicular magnetic layer composed of at least a 1 st magnetic layer and a 2 nd magnetic layer stacked alternately on a nonmagnetic substrate with a underlayer interposed therebetween. Further, patent document 3 discloses that the underlayer is made of Ru containing oxygen.

Patent document 4 discloses a sputtering target capable of forming a Ru film or a Ru oxide thin film having high adhesion to a substrate such as a plug or a barrier metal and having low resistivity when used as an electrode.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2012 and 009086

Patent document 2: japanese patent laid-open publication No. 2009-134804

Patent document 3: japanese patent laid-open publication No. 2005-243093

Patent document 4: japanese patent laid-open publication No. 2002-167668

Disclosure of Invention

Technical problem to be solved by the invention

The intermediate layer present under the magnetic recording layer plays an important role in order to improve the separability. If Ru grains are present in the intermediate layer, the grains of the magnetic recording layer grow starting from the Ru grains. In addition, if Ru oxide and Ru-B are used as the intermediate layer, magnetic recording characteristics can be improved. Based on such knowledge, the present inventors have studied the combination of Ru and boron oxide. The purpose is to obtain a structure in which boron oxide is arranged around Ru crystal grains. Therefore, although a method of co-sputtering Ru and boron oxide is also considered, sputtering a single sputtering target containing both is more advantageous in terms of manufacturing steps.

Therefore, the present inventors have first studied to produce a sputtering target containing Ru and a boron oxide. As a result, the following points were found. In order to manufacture a sputtering target, the material must be subjected to Hot Pressing (HP) and/or Hot Isostatic Pressing (HIP). At this point, the material is at a high temperature. The inventors have found that when B is used₂O₃When used as boron oxide, B is added₂O₃Has a low melting point and is thus subjected to HP and/or HIP treatment B₂O₃May be lost from the material. As a result, the amount of boron oxide remaining in the sintered body is significantly reduced. Therefore, B cannot be used in the production of a sputtering target containing Ru and boron oxide₂O₃. In view of the above, an object of the present invention is to provide a sputtering target containing Ru and a boron oxide.

Means for solving the problems

The present inventors have further studied and found that B can be substituted by B₂O₃When a specific complex boron oxide is used, boron remains in the sintered body. The reason why the residue is considered to be caused is that the melting point ratio B is used₂O₃Higher boron oxide, and therefore lower bleed during HP and/or HIP treatment.

The present invention has been completed based on the above knowledge, and in one aspect, the present invention includes the following inventions.

(invention 1)

A sputtering target comprises Ru as a main component and has a melting point ratio of B₂O₃High and boron-containing composite oxides.

(invention 2)

The sputtering target according to invention 1, wherein the content of B is 0.01 wt% or more.

(invention 3)

The sputtering target according to invention 1 or 2, wherein the relative density is 90% or more.

(invention 4)

The sputtering target according to any one of inventions 1 to 3, which contains 1 or more kinds of elements selected from Co, Cr, Mn and Ti as constituent elements in addition to Ru, B and O.

(invention 5)

The sputtering target according to any one of inventions 1 to 4, wherein the melting point of the composite oxide is 750 ℃ or higher.

(invention 6)

The sputtering target according to any one of inventions 1 to 5, wherein the composite oxide is selected from the group consisting of Co₂B₂O₅、CrBO₃、TiBO₃And Mn₃B₂O₆1 or more of the group.

(invention 7)

A powder of a composite oxide for use in the production of a sputtering target, said composite oxide having a melting point ratio B₂O₃Higher and boron-containing composite oxides.

(invention 8)

The powder according to invention 7, wherein the melting point of the composite oxide is 750 ℃ or higher.

(invention 9)

The powder according to invention 7 or 8, wherein the composite oxide is selected from the group consisting of Co₂B₂O₅、CrBO₃、TiBO₃And Mn₃B₂O₆1 or more of the group.

(invention 10)

The powder according to any one of claims 7 to 9, wherein the specific surface area is 0.5 to 80m²(iii)/g, particle diameter of 0.3 to 15 μm and/or concentration of impurities of 10000wtppm or less.

ADVANTAGEOUS EFFECTS OF INVENTION

In one aspect, a sputtering target of the present disclosure, comprises Ru and B. Thus, simultaneous sputtering is not required, and there is an advantage in terms of manufacturing steps.

Drawings

FIG. 1 shows the use of Ru powder and Co powder in one embodiment₂B₂O₅SEM photograph of the powder produced target. The portion of the box in the figure represents a portion of the oxide analyzed by EDS.

Detailed Description

Hereinafter, specific embodiments for carrying out the disclosed invention will be described. The following description is intended only to facilitate an understanding of the disclosed invention. I.e. not intended to limit the scope of the invention.

1. Sputtering target

In one embodiment, the present disclosure relates to a sputtering target.

1-1. Composition of sputtering target

In one embodiment, the sputtering target contains at least Ru and a composite oxide. Further, Ru is a main component of the sputtering target.

Here, the main component is an element having the largest content (at%) among metal elements. Typically, the main component means containing 50 at% or more.

In addition, theThe composite oxide contains boron and has a melting point ratio of B₂O₃A high compound. Thus, with use of B₂O₃In the case of manufacturing a sputtering target, B can be left in the sintered body more than in the case of manufacturing a sputtering target. Therefore, the crystal separability of Ru after sputtering can be improved.

In one embodiment, the content of Ru may be 80.0-99.8 wt%. By 80.0 wt% or more, the Ru crystal grains required for the grain growth of the recording layer can be sufficiently ensured in the intermediate layer after film formation. When the content is 99.8 at% or less, the content of B for separating the crystal grains of Ru can be sufficiently secured in the intermediate layer after film formation. The lower limit of the Ru content is preferably 90.0 wt% or more, more preferably 95 wt% or more. The upper limit of the Ru content is preferably 99.5 wt% or less, more preferably 99.0 wt% or less.

In one embodiment, the content of B is 0.01 wt% or more. When the content is 0.01 wt% or more, the content of B for separating the crystal grains of Ru can be sufficiently secured in the intermediate layer after film formation. The upper limit of the content of B is not particularly limited, and may be typically 3.0 wt% or less from the viewpoint of maintaining the properties of Ru. The lower limit of the content of B is preferably 0.05 wt% or more, more preferably 0.15 wt% or more.

In one embodiment, the sputtering target may contain 1 or more selected from Co, Cr, Mn, and Ti in addition to the Ru, B, and O described above. These elements can form a composite oxide with B. And, the complex oxide, with B₂O₃Compared with a higher melting point. Therefore, the possibility of melting and loss in heat treatment (e.g., HIP, HP, etc.) during manufacturing is low.

The content of 1 or more elements selected from Co, Cr, Mn and Ti is not particularly limited, and is preferably determined by the stoichiometric ratio of the element to B to form a composite oxide.

Similarly, the content of O is not particularly limited, and is preferably determined in accordance with the stoichiometric ratio of the compound oxide to B.

For example, when the composite oxide is Co₂B₂O₅In the case of (1), inWhen the weight of the entire composite oxide was taken as 100%, Co was 53.70 wt%, B was 9.85 wt%, and O was 36.45 wt%. Therefore, assuming that the weight of the entire sputtering target is 100% and the content of B in the entire sputtering target is 0.01 wt% or more, Co is 0.054 wt% or more and O is 0.036 wt% or more.

In one embodiment, the sputtering target may be composed of the following elements:

Ru；B；

more than 1 selected from Co, Cr, Mn and Ti; and O.

In one embodiment, the sputtering target may contain inevitable impurities in addition to the above elements. The content of inevitable impurities is 10000wtppm or less, preferably 5000wtppm or less (total amount of all inevitable impurity elements).

Elemental analysis (and quantitative analysis) of the sputtering target can be performed by methods known in the art. For example, the following method can be used. For example, the sputtering target itself or a leftover of a sintered body (a fragment left when processed into a sputtering target shape) can be used as a sample. First, about 5g of a sample is sampled from a portion as close to the center of the sputtering target as possible and powdered. O, N, C, the powder was heated and gasified, and then measured by far infrared absorption (TC 600 manufactured by LECO). Boron and a metal element were dissolved in a powder with an acid or the like, and analyzed by using an ICP emission spectrometry apparatus (SPS 3100HV manufactured by hitachi high-tech company). Alternatively, the constituent elements may be analyzed by EDS (S-3700N manufactured by Hitachi high-tech Co., Ltd.), or EMPA (JXA-8500F manufactured by Japan Electron Co., Ltd.).

1-2. Boron-containing composite oxides in sputtering targets

In one embodiment, the boron-containing composite oxide includes a composite oxide of B and O with a metal element. The reason why such a composite oxide is used is that the melting point is higher than that of B₂O₃High, the possibility of loss through heat treatment is low.More preferably, the boron-containing composite oxide has a melting point of 750 ℃ or higher (preferably 1000 ℃ or higher). The upper limit value is not particularly limited, and is typically 1300 ℃ or lower.

The metal element constituting the boron-containing composite oxide is preferably 1 or more selected from Co, Cr, Mn, and Ti, but is not limited thereto. The reason why these metal elements are preferred is that the possibility of adversely affecting the crystallinity of Ru is low. For example, Co has an hcp crystal structure similar to that of Ru, and therefore does not affect the crystallinity of Ru. Cr, Ti and Mn do not react with Ru even when they are rich in Ru, and therefore do not affect the crystallinity of Ru.

Specific examples of the boron-containing composite oxide include compounds selected from the group consisting of Co₂B₂O₅、CrBO₃、TiBO₃And Mn₃B₂O₆1 or more of the group, but not limited thereto.

The presence or absence of the boron-containing composite oxide can be confirmed by EDS or EPMA.

1-3. Relative density of sputtering target

In one embodiment, the relative density of the sputtering target may be 90% or more, preferably 98% or more. This can further reduce the generation of arc. The relative density referred to in the present specification means a ratio of a measured density to a theoretical density. The measured density is a value measured by an archimedes method using pure water as a solvent. Theoretical density, as described below, the elemental densities of the raw materials were respectively multiplied by the mixing mass ratio, and the obtained values were summed.

Theoretical density { (theoretical density of component n × mixed mass ratio) }

In order to manufacture a sputtering target having a high relative density, it is necessary to apply pressure at a high temperature as described below. However, the material contains an image B₂O₃In the case of a low-melting B compound, B₂O₃It melts with heat treatment and is worn. If the pressure is reduced, on the other hand, the relative density is reduced,can not meet the requirement standard of products. Therefore, it is very significant that a sputtering target containing B and having a high relative density can be obtained.

2. Powder of sputtering target

2-1. Characteristics of the powder

In one embodiment, the present disclosure relates to a powder for use in the manufacture of a sputtering target, and the use of the powder. The powder is composed of boron-containing composite oxide. Preferably, the boron-containing composite oxide has a melting point of 750 ℃ or higher (more preferably 1000 ℃ or higher). The upper limit is not particularly limited, but is typically 1300 ℃ or lower. The metal element constituting the boron-containing composite oxide of the powder is preferably 1 or more selected from Co, Cr, Mn, and Ti, but is not limited thereto. Specific examples of the boron-containing composite oxide include compounds selected from the group consisting of Co and Co₂B₂O₅、CrBO₃、TiBO₃And Mn₃B₂O₆1 or more of the group, but not limited thereto.

In one embodiment, the particle diameter D50 of the powder is 0.3 to 15 μm. By using these dimensions, a sputtering target of good quality can be manufactured. The lower limit of D50 is preferably 0.8 μm or more, more preferably 1.0 μm or more. The upper limit of D50 is preferably 10 μm or less, more preferably 5 μm or less.

The particle size of the powder is a particle size at which the cumulative value is 50% (D50) based on the volume value in the particle size distribution obtained by the laser diffraction/scattering method. For example, the particle diameter can be measured by dispersing the powder in a solvent of ethanol using a particle size distribution measuring apparatus of type LA-920 manufactured by HORIBA.

In one embodiment, the powder has a low impurity concentration. The reason for this is that impurities adversely affect the sputtering target after production. For example, the impurities include Ti (limited to a complex oxide of Co, Cr, or Mn), Al, N, and C. The total concentration of these is 10000wtppm or less, preferably 5000wtppm or less. For the analysis of the impurity concentration, the infrared absorption method, the ICP emission spectrometer, GDMS (glow discharge mass spectrometry), and the like described above can be used.

In one embodiment, the powder has a specific surface area of 0.5 to 80m²(ii) in terms of/g. By obtaining such a specific surface area, a sputtering target of good quality can be produced. The lower limit of the specific surface area is preferably 0.8m²A value of at least g, more preferably 1.5m²More than g. The upper limit of the specific surface area is preferably 50m²A ratio of 35m or less per gram²The ratio of the carbon atoms to the carbon atoms is less than g.

The specific surface area in the present specification means a value measured according to the following procedure:

degassing the subject substance at 200 ℃ for 2 hours

Monosorb manufactured by Quantachrome corporation, measured by the BET method (1-point method) using a mixed gas of He70 at% to N230 at% as an adsorption gas.

2-2. Method for producing boron-containing composite oxide powder

First, a powder containing an oxide of at least one of Co, Cr, Ti, and Mn and an oxide containing B is prepared. Commercially available powders can be used as the powder. These powders are mixed and then heat-treated at a temperature not higher than the melting point to produce the powder. In addition, in order to form a powder suitable for manufacturing a sputtering target, a pulverization step can be added after the synthesis.

The method of mixing and pulverizing is not particularly limited, and known methods such as mortar mixing and ball milling can be used.

The step of performing heat treatment may also use a known method.

3. Method for manufacturing sputtering target

In one embodiment, the present disclosure relates to a method of manufacturing a sputtering target. The method comprises at least the following steps.

A step of mixing Ru powder and boron-containing composite oxide powder

Step of pressure sintering the mixed powder

3-1. Mixing

First, Ru powder and boron-containing composite oxide powder are prepared. As the Ru powder, a commercially available powder can be used. Preferably, a powder suitable for manufacturing a sputtering target (e.g., low impurity, etc.) is used. On the other hand, as described above, the boron-containing composite oxide powder may use a boron-containing composite oxide having a melting point of 750 ℃ or higher (preferably 1000 ℃ or higher).

The method for mixing the two is not particularly limited, and known methods such as mortar mixing and ball milling can be used.

3-2. Pressure sintering

The mixed powder can be filled in a mold or the like and sintered. Examples of the pressing method in sintering include Hot Pressing (HP) and/or Hot Isostatic Pressing (HIP).

The treatment temperature during hot pressing may be 750 to 1200 ℃. The lower limit of the treatment temperature is preferably 900 ℃ or higher. The upper limit of the treatment temperature is preferably 1100 ℃ or lower. The holding pressure during sintering is preferably 150kgf/cm²Within the above pressure range.

The treatment temperature during hot isostatic pressing may be 750 to 1200 ℃. The lower limit of the treatment temperature is preferably 900 ℃ or higher. The upper limit of the treatment temperature is preferably 1100 ℃ or lower. The holding pressure during sintering is preferably 1000kgf/cm²Within the above pressure range.

3-3. Others

After the above-mentioned mixing and sintering, further machining is performed to finally form a desired shape.

4. Use of sputtering targets

4-1. Film formation

The sputtering target obtained by the above-described steps can be used to form a film. The conditions for sputtering may be those known in the art, and typically, the following conditions are used.

Sputtering conditions

A sputtering device: c3010 manufactured by Canon Anelva corporation

Input power is 100 to 1kW (e.g., 1kW),

ar gas pressure is 1 to 10Pa (e.g., 1.7Pa),

pre-sputtering 0.5 to 2kWhr (e.g., 2kWhr)

4-2. Magnetic recording medium

By performing sputtering under the above conditions, an intermediate layer for the magnetic recording layer can be formed. By applying this layer, a magnetic recording medium can be manufactured.

For example, the production can be performed by the following steps. First, a substrate is prepared. On the substrate, a layer having a composition of NiW or NiFeW is formed. Next, a pure Ru layer is formed on the NiW layer or the NiFeW layer. Thereafter, by sputtering using the sputtering target, a layer composed of a complex oxide containing Ru and boron can be formed as an intermediate layer. Then, a magnetic recording layer is formed over the intermediate layer. On the magnetic recording layer, a layer known in the art, such as a protective layer and a lubricant layer, can be provided. Further, a layer known in the art, such as an adhesion layer mainly composed of CrTi and NiTa, a soft magnetic layer mainly composed of FeCoTa, FeCoNb, FeCoMo, or the like, and a Ru layer for promoting antiferromagnetic coupling in the middle of the soft magnetic layer, may be provided below the NiW layer.

In the perpendicular magnetic recording medium obtained by the above method, the irregularities at the interface between Ru and the recording layer are relatively small, the magnetic separation between the magnetic particles of the recording layer is good, and the magnetic anisotropy of the magnetic particles can be improved, so that the recording density of the HDD using the medium can be improved.

Examples

5. Examples of the embodiments

5-1. Manufacture of sputtering targets

Ruthenium powder (purity 99.9 wt%) and boron-containing composite oxide powder (purity 99 wt%) were prepared. As the boron-containing complex oxide, Co was prepared₂B₂O₅、CrBO₃、TiBO₃And Mn₃B₂O₆4 of these (examples 1 to 4), and B₂O₃(comparative example). The content of the boron-containing complex oxide is shown in Table1 in the above-mentioned "B target composition value wt%", ruthenium powder and boron-containing composite oxide powder are mixed. Next, the mixture was filled into a carbon mold and hot-pressed. The hot pressing conditions are Ar atmosphere, sintering temperature is 1000 ℃, and sintering pressure is 300kg/cm²And the sintering time is 2 hours. The sintered body taken out of the hot-pressed mold is subjected to Hot Isostatic Pressing (HIP). The hot isostatic pressing sintering is carried out at 1100 deg.C for 2 hr, while gradually increasing Ar gas pressure from the start of heating to 1500kgf/cm at 1100 deg.C²Pressurization is performed. The obtained sintered body was cut into a desired size to obtain a disk-shaped sputtering target.

Further, a sputtering target (reference example) was obtained by using only ruthenium powder (purity: 99.9 wt%) and producing the sputtering target under the same conditions as described above.

Immediately after hot pressing and after hot isostatic pressing sintering, the density of the sintered body was measured, and the relative density was calculated.

The amount of boron was analyzed by an ICP emission spectrometry (SPS 3100HV, manufactured by hitachi high-tech company).

The results are shown in table 1.

[ TABLE 1 ]

In example 1, mixing was performed so that the B amount was 0.55 wt%, and a sputtering target was manufactured. The B content in the sputtering target as a finished product was 0.49 wt%. Thus, B remains after hot pressing and hot isostatic pressing sintering. Examples 2 to 4 also show the same tendency.

5-2. Presence of boron-containing complex oxides

In examples 1 to 4, the structure of the sputtering target was observed by SEM (FIG. 1). In addition, quantitative analysis was performed on a part of the oxide to be observed (block part of FIG. 1) using EDS (S-3700N manufactured by Hitachi high tech Co., Ltd.). The results are shown in table 2.

[ TABLE 2 ]

In example 1, Co, B, and O were detected in the same region. Thus, the presence of Co is shown₂B₂O₅The composite oxide of (3). Hereinafter, it is shown that the required composite oxide (CrBO) is present in examples 2 to 4 in the same manner₃、TiBO₃And Mn₃B₂O₆)。

The specific embodiments of the present invention have been described above. The above embodiments are merely specific examples of the present invention, and the present invention is not limited to the above embodiments. For example, the technical features disclosed in one of the above embodiments can be applied to other embodiments. In addition, unless otherwise specified, some steps can be replaced by other sequences of steps for a particular method, and more steps can be added between a particular 2 steps. The scope of the invention is defined by the scope of the claims.

Claims

1. A sputtering target comprises Ru as a main component and has a melting point ratio of B₂O₃High and boron-containing composite oxides.

2. The sputtering target according to claim 1, wherein the content of B is 0.01 wt% or more.

3. A sputtering target according to claim 1 or 2, wherein the relative density of the target is 90% or more.

4. The sputtering target according to any one of claims 1 to 3, wherein 1 or more selected from Co, Cr, Mn and Ti are contained as constituent elements in addition to Ru, B and O.

5. The sputtering target according to any one of claims 1 to 4, wherein the melting point of the composite oxide is 750 ℃ or higher.

6. A sputter target according to any one of claims 1 to 5, whereby said composite oxide is selected from the group consisting of Co₂B₂O₅、CrBO₃、TiBO₃And Mn₃B₂O₆1 or more of the group.

7. A powder of a composite oxide for use in the production of a sputtering target, wherein the composite oxide has a melting point ratio B₂O₃High and boron-containing composite oxides.

8. The powder according to claim 7, wherein the melting point of the composite oxide is 750 ℃ or higher.

9. The powder according to claim 7 or 8, wherein the composite oxide is selected from the group consisting of Co₂B₂O₅、CrBO₃、TiBO₃And Mn₃B₂O₆1 or more of the group.

10. The powder according to any one of claims 7 to 9, wherein the specific surface area is 0.5 to 80m²A particle size of 0.3 to 15 μm/g, and/or an impurity concentration of 10000wtppm or less.