JP7072664B2 - Sputtering target and manufacturing method of sputtering target - Google Patents

Description

The present disclosure relates to a sputtering target and a method for manufacturing the sputtering target. More specifically, the present invention relates to a sputtering target containing Ru and a method for manufacturing the sputtering target.

In the field of magnetic recording represented by a hard disk drive, a material based on the ferromagnetic metals Co, Fe, or Ni is used as the material of the magnetic thin film responsible for recording. For example, a Co—Cr-based or Co—Cr—Pt-based ferromagnetic alloy containing Co as a main component has been used for the recording layer of a hard disk that employs an in-plane magnetic recording method.

In recent years, the capacity of magnetic recording of hard disk drives and the like has been increasing. In order to realize this high capacity, it is important to improve the separability of the 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. Further, in Patent Document 1, crystal grain boundaries formed by oxides are formed in the second base layer 150b to promote separability between particles, and the crystal orientation of Ru and the main recording layer 160 constituting the base layer 150. It is disclosed that it also has an effect of improving.

Patent Document 2 discloses a vertical magnetic recording medium including a non-magnetic intermediate layer and a magnetic layer. Further, Patent Document 2 discloses Ru as the first non-magnetic intermediate layer and CoCr alloy as the second non-magnetic intermediate layer.

In Patent Document 3, at least a vertical magnetic layer formed by alternately laminating a first magnetic layer and a second magnetic layer on a non-magnetic substrate is provided via a base layer. The recording medium is disclosed. Further, Patent Document 3 discloses that the underlying layer 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 a small specific resistance when used as an electrode.

Japanese Unexamined Patent Publication No. 2012-09086 Japanese Unexamined Patent Publication No. 2009-134804 Japanese Unexamined Patent Publication No. 2005-243093 Japanese Unexamined Patent Publication No. 2002-167668

The intermediate layer underneath the magnetic recording layer plays an important role in improving the separability. When Ru crystal grains are present in the intermediate layer, the crystal grains in the magnetic recording layer grow from the Ru crystal grains as a starting point. Further, when Ru oxide and Ru-B are used as an intermediate layer, the magnetic recording characteristics are improved. Based on these findings, the present inventors examined the combination of Ru and boron oxide. The purpose of this is to obtain a structure in which a boron oxide is arranged around Ru crystal grains. Here, although a method of co-sputtering Ru and boron oxide can be considered, a single sputtering target containing both is more advantageous in terms of the manufacturing process.

Therefore, the present inventors first examined the production of a sputtering target containing Ru and a boron oxide. As a result, we found the following points. In order to manufacture a sputtering target, it is necessary to apply a treatment such as hot pressing (HP) and / or hot isotropic pressure pressurization (HIP) to the material. At this time, the material is exposed to high temperatures. When B ₂ O ₃ was used as the boron oxide, the present inventors had a low melting point _, so that _{B 2 O 3} was discharged from the material by HP and / or HIP treatment. As a result, the amount of boron oxide remaining in the sintered body has been significantly reduced. Therefore, B ₂ O ₃ could not be used in the production of sputtering targets containing Ru and boron oxide. In view of the above circumstances, it is an object of the present disclosure to provide a sputtering target containing Ru and a boron oxide.

As a result of further studies, the present inventors have found that when a specific composite boron oxide is used instead of B ₂ O ₃ , boron remains in the sintered body. It is considered that the reason for the residual is that the amount lost during the HP and / or HIP treatment could be reduced by using the boron oxide having a melting point higher than that of B ₂ O ₃ .

The present invention has been completed based on the above findings and includes the following inventions in one aspect.
(Invention 1)
A sputtering target containing Ru as a main component, which has a melting point higher than that of B ₂ O ₃ and contains a composite oxide containing boron.
(Invention 2)
The sputtering target according to the invention 1, wherein the content of B is 0.01 wt% or more.
(Invention 3)
The sputtering target according to the invention 1 or 2, wherein the relative density is 90% or more.
(Invention 4)
The sputtering target according to any one of the inventions 1 to 3, further comprising one or more selected from Co, Cr, Mn, and Ti as constituent elements in addition to Ru, B, and O. target.
(Invention 5)
The target according to any one of the inventions 1 to 4, wherein the composite oxide has a melting point of 750 ° C. or higher.
(Invention 6)
The sputtering target according to any one of the inventions 1 to 5, wherein the composite oxide is selected from the group consisting of Co ₂ B ₂ O ₅ , CrBO ₃ , TiBO ₃ and Mn ₃ B ₂ O ₆ . The target, which is more than a species.
(Invention 7)
A powder of a composite oxide for use in the production of a sputtering target, wherein the composite oxide is a composite oxide having a melting point higher than that of B ₂ O ₃ and containing boron.
(Invention 8)
The powder according to the invention 7, wherein the composite oxide has a melting point of 750 ° C. or higher.
(Invention 9)
The powder according to the invention 7 or 8, wherein the composite oxide is one or more selected from the group consisting of Co ₂ B ₂ O ₅ , CrBO ₃ , TiBO ₃ and Mn ₃ B ₂ O ₆ . , The powder.
(Invention 10)
The powder according to any one of the inventions 7 to 9, having a specific surface area of 0.5 to 80 m ² / g, a particle size of 0.3 to 15 μm, and / or a concentration as an impurity. The powder, which is 10,000 wtppm or less.

In one aspect, the sputtering targets of the present disclosure include Ru and B. This eliminates the need for co-sputtering and is advantageous in the manufacturing process.

In one embodiment, it is an SEM photograph in a target produced using Ru powder and Co ₂ B ₂ O ₅ powder. The square part represents a part of the oxide analyzed by EDS.

Hereinafter, specific embodiments for carrying out the invention of the present disclosure will be described. The following description is intended to facilitate understanding of the inventions of the present disclosure. That is, it is not intended to limit the scope of the present invention.

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

1-1. Sputtering Target Composition In one embodiment, the sputtering target comprises at least Ru and a composite oxide. Ru is the main component of the sputtering target.

Here, the principal component means an element having the largest content (at%) among the metal elements. Typically, the principal component may mean 50 at% or more.

Further, the composite oxide is a compound containing boron and having a melting point higher than that of B ₂ O ₃ . As a result, more B can be left in the sintered body as compared with the case where the sputtering target is manufactured using B ₂ O ₃ . Therefore, the crystal separability of Ru after sputtering is improved.

In one embodiment, the Ru content may be 80.0-99.8 wt%. When the content is 80.0 wt% or more, it is possible to sufficiently secure the Ru crystal grains necessary for the growth of the crystal grains in the recording layer in the intermediate layer after the film formation. When the content is 99.8 wt% or less, it is possible to secure a sufficient B content in the intermediate layer after film formation to separate Ru crystal grains. 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, it is possible to secure a sufficient B content in the intermediate layer after film formation to separate Ru crystal grains. The upper limit of the content of B is not particularly limited, but may be typically 3.0 wt% or less from the viewpoint of maintaining the characteristics 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, in addition to the Ru, B and O described above, the sputtering target can include one or more selected from Co, Cr, Mn, and Ti. These elements can form a composite oxide with B. The composite oxide has a higher melting point than B ₂ O ₃ . Therefore, there is a low possibility that the product will be melted and lost due to heat treatment during manufacturing (eg, HIP, HP, etc.).

The content of one or more elements selected from Co, Cr, Mn, and Ti is not particularly limited, but is preferably a content according to the stoichiometric ratio of forming a composite oxide with B.

Similarly, the content of O is not particularly limited, but is preferably a content according to the stoichiometric ratio of forming a composite oxide with B.
For example, when the composite oxide is Co ₂ B ₂ O ₅ , when the total weight of the composite oxide is 100%, Co is 53.70 wt%, B is 9.85 wt%, and O is 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. Become.

In one embodiment, the sputtering target may be composed of the following elements:
Ru;
B;
One or more selected from Co, Cr, Mn, and Ti; and O.

In one embodiment, the sputtering target may contain unavoidable impurities in addition to the elements described above. The content as an unavoidable impurity is 10,000 wtppm or less, preferably 5000 wtppm or less (total amount of all unavoidable impurity elements).

Elemental analysis (and quantification) of the sputtering target can be performed by methods known in the art. For example, it can be performed by the following method. For example, the sputtering target itself or the scraps of the sintered body (cut pieces left over when processing into the shape of the sputtering target) can be used as a sample. First, a sample of about 5 g collected from a location as close to the center of the sputtering target as possible is pulverized. O, N and C can be measured by heating the powder and gasifying it, and then using an infrared absorption method (TC600 manufactured by LECO). For boron and metal elements, the powder is dissolved with an acid or the like and analyzed using an ICP emission spectrophotometer (SPS3100HV manufactured by Hitachi High-Tech Science Co., Ltd.). Alternatively, the constituent elements may be analyzed by EDS (S-3700N manufactured by Hitachi High-Technologies Corporation) or EPMA (JXA-8500F manufactured by JEOL Ltd.).

1-2. Boron-Containing Composite Oxides in Sputtering Targets In one embodiment, the boron-containing composite oxide comprises a composite oxide composed of B, O and a metal element. The reason for using such a composite oxide is that it has a higher melting point than the above-mentioned B ₂ O ₃ and is less likely to be lost by heat treatment. More preferably, the melting point of the composite oxide containing boron may be 750 ° C. or higher (preferably 1000 ° C. or higher). The upper limit is not particularly limited, but is typically 1300 ° C. or lower.

The metal element constituting the composite oxide containing boron preferably includes, but is not limited to, one or more selected from Co, Cr, Mn, and Ti. The reason why these metal elements are preferable is that they are unlikely to adversely affect the crystallinity of Ru. For example, Co has the same hcp crystal structure as Ru, so it does not affect the crystallinity of Ru. When Cr, Ti, and Mn are abundant in Ru, they do not react with Ru and do not affect the crystallinity of Ru.

Specific examples of the composite oxide containing boron include, but are not limited to, one or more selected from the group consisting of Co ₂ B ₂ O ₅ , CrBO ₃ , TiBO ₃ and Mn ₃ B ₂ O ₆ .

The presence or absence of the above-mentioned 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. As a result, the occurrence of arcing is further suppressed. The relative density referred to in the present specification refers to the ratio between the measured density and the theoretical density. The measured density refers to the value measured by the Archimedes method using pure water as a solvent. The theoretical density is the sum of the obtained values by multiplying each of the elemental densities of the raw materials by the mixed mass ratio as described below.
Theoretical density = Σ {(theoretical density of component n x mixed mass ratio)}

In order to manufacture a sputtering target with a high relative density, it is necessary to apply pressure at a high temperature as described later. However, when a B compound having a low melting point such as B ₂ O ₃ is contained in the material, B ₂ O ₃ is melted and lost due to the heat treatment. On the other hand, if the pressure is lowered, the relative density becomes low and the required level of the product cannot be passed. Therefore, it is significant that a sputtering target containing B and having a high relative density can be realized.

2. 2. Sputtering target powder
2-1. Powder Properties In one embodiment, the present disclosure relates to powders for producing sputtering targets and the use of such powders. The component of the powder is a composite oxide containing boron. Preferably, the melting point of the composite oxide containing boron is 750 ° C. or higher (more preferably 1000 ° C. or higher). The upper limit is not particularly limited, but is typically 1300 ° C. or lower. The metal element constituting the complex oxide containing boron in the powder preferably includes, but is not limited to, one or more selected from Co, Cr, Mn, and Ti. Specific examples of the composite oxide containing boron include, but are limited to, one or more selected from the group consisting of Co ₂ B ₂ O ₅ , CrBO ₃ , TiBO ₃ and Mn ₃ B ₂ O ₆ . Not done.

In one embodiment, the powder may have a particle size D50 of 0.3 to 15 μm. With these sizes, a good quality sputtering target can be manufactured. The lower limit of D50 is preferably 0.8 μm or more, and more preferably 1.0 μm or more. The upper limit of D50 is preferably 10 μm or less, and more preferably 5 μm or less.

The particle size of the powder means the particle size at an integrated value of 50% (D50) based on the volume value in the particle size distribution obtained by the laser diffraction / scattering method. For example, the particle size can be measured by dispersing the powder in an ethanol solvent using a particle size distribution measuring device of model 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, examples of the impurities include Ti (limited to the case of a composite oxide of Co, Cr, or Mn), Al, N, C, and the like. The total concentration of these may be 10,000 wtppm or less, preferably 5000 wtppm or less. The impurity concentration can be analyzed by using the above-mentioned infrared absorption method, ICP emission spectroscopic analyzer, GDMS (glow discharge mass spectrometry) and the like.

In one embodiment, the specific surface area of the powder may be 0.5-80 m ² / g. With these specific surface areas, a good quality sputtering target can be manufactured. The lower limit of the specific surface area is preferably 0.8 m ² / g or more, and more preferably 1.5 m ² / g or more. The upper limit of the specific surface area is preferably 50 m ² / g or less, and more preferably 35 m ² / g or less.

In addition, the specific surface area in this specification refers to the value measured by the following procedure:
-Degas the target substance at 200 ° C. for 2 hours.-Measure by the BET method (1 point method) using a mixed gas of He70at% -N230at% as an adsorbed gas in a Monosorb manufactured by Kantachrome.

2-2. Method for Producing Composite Oxide Powder Containing Boron First, an oxide containing at least one of Co, Cr, Ti and Mn and a powder of an oxide containing B are prepared. Commercially available products may be used as these powders. These powders are mixed and then heat-treated at a temperature below the melting point to prepare the powder. Further, in order to obtain a powder suitable for producing a sputtering target, a pulverization step can be added after the synthesis.

The method of mixing and crushing is not particularly limited, and known means such as mortar mixing and ball mill may be used.

A known means may be used for the step of performing the heat treatment.

3. 3. Method for Manufacturing Sputtering Targets In one embodiment, the present disclosure relates to a method for manufacturing a sputtering target. The method comprises at least the following steps.
-Step of mixing Ru powder and powder of composite oxide containing boron-Step of pressure sintering the mixed powder

3-1. Mixing First, a Ru powder and a powder of a composite oxide containing boron are prepared. As the Ru powder, a commercially available product may be used. Preferably, a powder suitable for producing a sputtering target is used (eg, low impurities, etc.). On the other hand, as the powder of the composite oxide containing boron, as described above, the composite oxide containing boron having a melting point of 750 ° C. or higher (preferably 1000 ° C. or higher) may be used.

The method of mixing the two is not particularly limited, and known means such as mortar mixing and ball mill may be used.

3-2. Pressure sintering The above-mentioned mixed powder can be filled in a mold or the like and sintered. Examples of the pressurizing method at the time of sintering include hot pressing (HP) and / or hot isotropic pressure pressurization (HIP).

The processing temperature during hot pressing may be 750 to 1200 ° C. The lower limit of the treatment temperature may be preferably 900 ° C. or higher. The upper limit of the treatment temperature may be preferably 1100 ° C. or lower. The holding pressure at the time of sintering is preferably in a pressure range of 150 kgf / cm ² or more.

The treatment temperature during hot isotropic pressure pressurization may be 750 to 1200 ° C. The lower limit of the treatment temperature may be preferably 900 ° C. or higher. The upper limit of the treatment temperature may be preferably 1100 ° C. or lower. The holding pressure at the time of sintering is preferably in the pressure range of 1000 kgf / cm ² or more.

3-3. In addition , after undergoing the above mixing and sintering, further machining may be performed to finish the desired shape.

4. Use of sputtering target
4-1. Film formation A film can be formed using the sputtering target obtained in the above step. As the sputtering conditions, conditions known in the art may be adopted, and typically, they are as follows.
Sputtering conditions Sputtering equipment: C3010 manufactured by Canon Angelva
Input power 100 to 1 kW (for example, 1 kW),
Ar gas pressure 1 to 10 Pa (for example, 1.7 Pa),
Pre-sputtering 0.5-2kWhr (eg 2kWhr)

4-2. Magnetic recording medium By sputtering under the above conditions, an intermediate layer for the magnetic recording layer can be formed. By applying this, a magnetic recording medium can be manufactured.
For example, it can be manufactured by the following procedure. First, prepare the board. A layer containing NiW or NiFeW is formed on the substrate. Next, a pure Ru layer is formed on the NiW layer or the NiFeW layer. Then, by sputtering using the above-mentioned sputtering target, a layer composed of Ru and a composite oxide containing boron can be formed as an intermediate layer. Then, a magnetic recording layer is formed on the intermediate layer. A layer known in the art such as a protective layer and a lubricating layer can be provided on the magnetic recording layer. Further, under the NiW layer, an adhesion layer containing CrTi or NiTa as a main component, a soft magnetic layer containing FeCoTa, FeCoNb, FeCoMo or the like as a main component, and a Ru layer promoting an antiferromagnetic bond between the soft magnetic layers. A layer known in the art such as, etc. can be provided.

In the vertical magnetic recording medium obtained by the above method, the unevenness at the interface between Ru and the recording layer is relatively small, the magnetic separation between the magnetic particles in the recording layer is good, and the magnetic anisotropy of the magnetic particles is increased. Therefore, the recording density of the HDD using this can be improved.

5. Example
5-1. Production of Sputtering Target A ruthenium powder (purity 99.9 wt%) and a composite oxide powder containing boron (purity 99 wt%) were prepared. Regarding the composite oxide containing boron, four types of Co ₂ B ₂ O ₅ , CrBO ₃ , TiBO ₃ , and Mn ₃ B ₂ O ₆ (Examples 1 to 4) and B ₂ O ₃ (comparative example) were used. Prepared. The ruthenium powder and the composite oxide powder containing boron were mixed so that the content of the composite oxide containing boron was "B target composition value wt%" shown in Table 1. The mixture was then filled into a carbon mold and hot pressed. The hot press conditions were an Ar atmosphere, a sintering temperature of 1000 ° C., a sintering pressure of 300 kg / cm ² , and a sintering time of 2 hours. The sintered body taken out from the hot press mold was subjected to hot hydrostatic pressure sintering (HIP). The conditions for hot hydrostatic pressure sintering were a holding temperature of 1100 ° C. and a holding time of 2 hours, and the gas pressure of Ar gas was gradually increased from the start of temperature rise and pressurized at 1500 kgf / cm ² while holding at 1100 ° C. .. The obtained sintered body was cut to a desired size to obtain a disk-shaped sputtering target.

Further, it was produced under the same conditions as above using only ruthenium powder (purity 99.9 wt%) to obtain a sputtering target (reference example).

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

The amount of boron was analyzed using an ICP emission spectrophotometer (SPS3100HV manufactured by Hitachi High-Tech Science Corporation).

The results are shown in Table 1.

In Example 1, a sputtering target was manufactured by mixing the amount of B so as to be 0.55 wt%. The B content in the resulting sputtering target was 0.49 wt%. Therefore, it was shown that B remained even after hot pressing and hot hydrostatic pressure sintering. Similar trends were shown in Examples 2-4.

5-2. Existence of Composite Oxide Containing Boron For Examples 1 to 4, the sputtering target structure was observed by SEM (FIG. 1). In addition, a part of the observed oxide (square part in FIG. 1) was quantitatively analyzed using EDS (S-3700N manufactured by Hitachi High-Technologies Corporation). The results are shown in Table 2.

In Example 1, Co, B and O were detected in the same compartment. Therefore, it was shown that a composite oxide of Co ₂ B ₂ O ₅ is present. Similarly, it was shown that the desired composite oxides (CrBO ₃ , TiBO ₃ and Mn ₃ B ₂ O ₆ ) are present in Examples 2 to 4 as well.

The specific embodiment of the present invention has been described above. The above embodiment is merely a specific example of the present invention, and the present invention is not limited to the above embodiment. For example, the technical features disclosed in one of the above embodiments can be applied to other embodiments. Further, unless otherwise specified, for a specific method, it is possible to replace some steps with the order of other steps, and a further step may be added between the two specific steps. The scope of the present invention is defined by the claims.

Claims (16)

A sputtering target containing Ru as a main component _, which has a melting point higher _than that of B2O3 and contains a composite oxide containing boron. The target according to claim 1, wherein the content of B is 0.01 wt% or more. The sputtering target according to claim 1 or 2, wherein the relative density is 90% or more. The sputtering target according to any one of claims 1 to 3, further comprising one or more selected from Co, Cr, Mn, and Ti as constituent elements in addition to Ru, B, and O. The target. The target according to any one of claims 1 to 4, wherein the composite oxide has a melting point of 750 ° C. or higher. The sputtering target according to any one of claims 1 to 5, wherein the composite oxide is selected from the group consisting of Co ₂ B ₂ O ₅ , CrBO ₃ , TiBO ₃ and Mn ₃ B ₂ O ₆ . The target, which is one or more. (Delete) (Delete) (Delete) (Delete) A method for producing a sputtering target containing Ru as a main component, which comprises a step of mixing the Ru with a composite oxide having a melting point higher _than that of _B2O3 and containing boron. .. The method for manufacturing a sputtering target according to claim 11, wherein the content of B in the sputtering target is 0.01 wt% or more. The method for manufacturing a sputtering target according to claim 11 or 12, wherein the relative density of the sputtering target is 90% or more. The method for manufacturing a sputtering target according to any one of claims 11 to 13, wherein the sputtering target is selected from Co, Cr, Mn, and Ti as constituent elements in addition to Ru, B, and O. A method for manufacturing a sputtering target, further comprising one or more of the above. The method for producing a sputtering target according to any one of claims 11 to 14, wherein the melting point of the composite oxide is 750 ° C. or higher. The method for producing a sputtering target according to any one of claims 11 to 15, wherein the composite oxide consists of a group consisting of Co ₂ B ₂ O ₅ , CrBO ₃ , TiBO ₃ and Mn ₃ B ₂ O ₆ . A method for producing the sputtering target, which is one or more selected.

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