TW202325873A - Sputtering target member, sputtering target assembly, and film forming method - Google Patents

Abstract

Provided is a sputtering target member which is for a magnetic recording layer and can suppress the generation of particles. This sputtering target member for a magnetic recording layer contains 10-70 mol% of Co, 5-30 mol% of Pt, 1.5-10 mol% of carbide, and 0-30 mol% in total of one or two more non-magnetic materials selected from among carbon, oxide, nitride, and carbonitride.

Description

Sputtering target component, sputtering target assembly, and film forming method

In one Embodiment, this invention relates to the sputtering target member for magnetic recording layers. In another embodiment, this invention is related with the sputtering target unit provided with such a sputtering target member. In still another embodiment, the present invention relates to a film forming method using such a sputtering target member.

In the field of magnetic recording typified by hard disk drives, materials using Co, Fe or Ni as a base material of ferromagnetic metals have been used as materials for magnetic thin films that function as recordings. For example, in the recording layer of a hard disk employing a perpendicular magnetic recording method that has been practically used in recent years, a Co-Pt-based ferromagnetic alloy containing Co as a main component, in which non-magnetic particles such as oxide particles and carbon particles are dispersed, is generally used. composite material. In the recording layer, the granular structure in which the magnetic particles are magnetically separated by the non-magnetic particles is miniaturized, and thus the recording amount per unit area increases.

From the viewpoint of high productivity, the magnetic thin film is usually produced by sputtering a sputtering target composed of the above materials using a magnetron sputtering apparatus. Therefore, conventionally, technical development of the sputtering target for magnetic thin film formation has been performed from various viewpoints.

Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2013-37730 ) discloses a sputtering target in which metals (magnetic metals, noble metals) and carbon constituting an L1 _0- type ordered alloy of FePt are mixed.

In this document, in order to be able to suppress the expansion of the head spacing of the magnetic recording medium and increase the recording density, a method for manufacturing a perpendicular magnetic recording medium is disclosed, which is characterized in that it includes:

(1) On a non-magnetic substrate, a magnetic recording layer comprising crystal grains of an ordered alloy and a grain boundary layer composed of carbon is formed, and a protective layer precursor composed of carbon present on the magnetic recording layer is formed. step,

(2) a step of irradiating the protective layer precursor with hydrocarbon-based ions generated by plasma discharging a hydrocarbon-based gas so that the protective layer precursor becomes a protective layer,

The hydrocarbon-based ions have an energy of 300 eV or more when they reach the protective layer precursor.

Patent Document 2 (International Publication No. 2014/132746) discloses a FePt—C sputtering target containing Fe, Pt, and C, which is characterized in that it has a structure in which primary particles including unavoidable impurities C is dispersed in the FePt-based alloy phase containing 33 at% to 60 at% of Pt and the balance consisting of Fe and unavoidable impurities without contacting each other. According to Patent Document 2, it is considered that this FePt—C-based sputtering target has few fine particles.

Patent Document 3 (Japanese Publication No. 2018-172770) discloses a sputtering target made of a ferromagnetic material, which contains a total of more than 70mol% of Metal Co and metal Pt, containing 0 mol% to 20 mol% of metal Cr, having: a Co particle phase containing 90 mol% or more of metal Co and an average particle size of 30 to 300 μm; and, in terms of molar ratio, Co: Pt=Y: Co-Pt alloy particle phase containing a total of 70 mol% or more of metal Co and metal Pt under the condition of 100-Y (20≤Y≤60.5) and having an average particle size of 7 μm or less. Patent Document 3 discloses a sputtering target made of a ferromagnetic material, which contains a total of 25 mol% or less of one or more than two selected from the group consisting of carbon, oxides, nitrides, carbides, and carbonitrides. It is considered that the ferromagnetic material sputtering target has a high leakage magnetic flux due to the method of making the Co-Pt alloy phase finer and the Co phase coarser, and it can also suppress the particle size during sputtering. produce.

Patent Document 4 (International Publication No. 2012/081340) proposes a step of adding 10 wtppm or more of B (boron) in addition to SiO ₂ to a sputtering target for a magnetic recording film. It is considered that by suppressing the formation of cristobalite that causes particles to be generated during sputtering, target microcracks and particle generation during sputtering can be suppressed, and burn-in time can be shortened.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2013-37730

Patent Document 2: International Publication No. 2014/132746

Patent Document 3: Japanese Patent Laid-Open No. 2018-172770

Patent Document 4: International Publication No. 2012/081340

The technical problem to be solved by the invention

In recent years, when forming a magnetic recording layer, the substrate is heated in advance (eg, about 200° C.). The main purpose is to improve the crystallinity of the magnetic particles, but as a secondary influence, the oxide particles may diffuse toward the magnetic particles, and the magnetic properties after film formation may be lowered. Therefore, it is conceivable to use carbon as a grain boundary material stable even at high temperatures. However, when only carbon is added, the fine particles proliferate and the yield decreases significantly. Strategies to reduce particulates by employing the techniques described in the prior art documents mentioned above are feasible, but there are limits. Therefore, from the viewpoint of increasing the options of technology and further expanding the possibility of technology development, it would be useful if particles can be reduced through a different approach.

Therefore, in one embodiment of the present invention, an object to be solved is to provide a sputtering target member for a magnetic recording layer capable of suppressing the generation of fine particles from a viewpoint different from the conventional art described above. In another embodiment of the present invention, the technical problem to be solved is to provide a sputtering target assembly including such a sputtering target component. In another embodiment of the present invention, the technical problem to be solved is to provide a film forming method using such a sputtering target member.

Solutions to technical problems

As a result of earnest research by the present inventors to solve the above-mentioned technical problems, it was found that the use of a Co—Pt-based sputtering target member having an increased ratio of carbides is effective for suppressing fine particles. The present invention has been accomplished based on the above knowledge, and is exemplified below.

[1]

The sputtering target component for the magnetic recording layer contains: 10 to 70 mol% of Co, 5 to 30 mol% of Pt, 1.5 to 10 mol% of carbides, and contains 0 to 30 mol% of carbon, oxides, and nitrogen in total. One or two or more non-magnetic materials selected from compounds and carbonitrides.

[2]

The sputtering target member for a magnetic recording layer according to [1], wherein the molar ratio of the carbide to the sum of the carbon and the carbide is 0.25 or more.

[3]

The sputtering target member for a magnetic recording layer according to [1] or [2], which contains one or two or more selected from B ₄ C, Cr ₃ C ₂ and TiC as carbides.

[4]

The sputtering target member for a magnetic recording layer according to [3], which contains 1.5 to 10 mol% of one or two or more selected from B ₄ C, Cr ₃ C ₂ and TiC in total.

[5]

The sputtering target member for a magnetic recording layer according to any one of [1] to [4], wherein one or both of Cr, Ru, B, Ti, Si, and Mn are contained in a total of 30 mol% or less. more than one metal element.

[6]

The sputtering target member for a magnetic recording layer according to any one of [1] to [5], wherein the relative density is 90% or more.

[7]

A sputtering target assembly comprising the sputtering target component for a magnetic recording layer according to any one of [1] to [6], and a back pipe or a back plate joined to the sputtering target component.

[8]

A film forming method comprising sputtering the sputtering target member for a magnetic recording layer according to any one of [1] to [6].

The effect of the invention

According to one embodiment of the present invention, since carbides are stable even at high temperatures, influence on magnetic properties after film formation can be suppressed, and a special effect of reducing particles during sputtering can be obtained.

(1. Sputtering target components)

(1-1. Components)

In one embodiment, the sputtering target member of the present invention contains: 10 to 70 mol% of Co, 5 to 30 mol% of Pt, and 1.5 to 10 mol% of carbides, and is selected from carbon, oxides, nitrides, and carbonitrides. One or two or more non-magnetic materials selected from the compound contain 0 to 30 mol% in total. In this component, the ratio of carbides occupying the entire sputtering target member is high, which is advantageous for suppressing particles during sputtering.

From the viewpoint of forming a magnetic recording layer, the concentration of Co in the sputtering target member is preferably 10 to 70 mol%. The concentration of Co can be appropriately adjusted according to the required magnetic properties of the magnetic recording layer. Typically, it can be selected from 20 to 70 mol%, more typically from 30 to 70 mol%, and still more typically from 40 to 60 mol%. It should be noted that Co considered here is metal Co existing as a single substance or metal Co alloyed with other metals such as Pt.

From the viewpoint of forming a magnetic recording layer, the concentration of Pt in the sputtering target member is preferably 5 to 30 mol%. The concentration of Pt can be appropriately adjusted according to the required magnetic properties of the magnetic recording layer, typically 5-25 mol%, more typically 10-25 mol%, still more typically 10-20 mol%. It should be noted that the Pt considered here is metal Pt that exists as a single substance or metal Pt that forms an alloy with another metal such as Co.

The concentration of carbides in the sputtering target member is preferably 1.5 to 10 mol%. The lower limit of the carbide concentration is 1.5 mol% or more, preferably 1.8 mol% or more, and more preferably 2.0 mol% or more, from the viewpoint of enhancing the particle suppression effect during sputtering. However, if the concentration of carbides is too high, the particle suppression effect will also decrease, so the upper limit of the concentration of carbides is 10 mol% or less, preferably 8.0 mol% or less, more preferably 6.0 mol% or less.

The above-mentioned sputtering target member may contain one type of carbide, or may contain two or more types of carbides. As carbides, for example, carbides of one or more elements selected from B, Ca, Cr, Nb, Si, Ta, Ti, W, and Zr can be cited, among which carbides selected from B ₄ C, Cr ₃ One or more selected from C ₂ and TiC, more preferably one or two selected from B ₄ C and Cr ₃ C ₂ , still more preferably B ₄ C.

Therefore, in a preferred embodiment, the above-mentioned sputtering target member contains 1.5 to 10 mol% in total of one or two or more selected from B ₄ C, Cr ₃ C ₂ and TiC, preferably 1.8 to 8.0 mol%, more preferably Contains 2.0~6.0mol%.

In a more preferable embodiment, the above-mentioned sputtering target member contains 1.5 to 10 mol% in total of one or two or more selected from B ₄ C and Cr ₃ C ₂ , preferably 1.8 to 8.0 mol%, more preferably 2.0 to 8.0 mol%. 6.0mol%.

In a still more preferable embodiment, the above-mentioned sputtering target member contains 1.5 to 10 mol % of B ₄ C, preferably 1.8 to 8.0 mol %, more preferably 2.0 to 6.0 mol %.

In the above sputtering target member, from the viewpoint of adjusting the magnetic properties of the magnetic recording layer, a nonmagnetic material other than carbide may be added. Specifically, one or more nonmagnetic materials selected from carbon, oxides, nitrides, and carbonitrides can contain 0 to 30 mol% in total, preferably 0 to 25 mol%, more preferably 0 to 20 mol %.

Examples of oxides include Al, B, Ba, Be, Ca, Ce, Co, Cr, Dy, Er, Eu, Ga, Gd, Ho, Li, Mg, Mn, Nb, Nd, Pr, Sc , Si, Sm, Sr, Ta, Tb, Ti, V, Y, Zn, and Zr are oxides of one or more elements selected. Among the oxides, oxides of one or two or more elements selected from B, Co, Cr, Si, and Ti are preferable.

Examples of nitrides include one or two or more nitrides of elements selected from Al, B, Ca, Nb, Si, Ta, Ti, and Zr.

Examples of carbonitrides include one or two or more carbonitrides of elements selected from Ti, Cr, V, and Zr.

From the viewpoint of effectively suppressing particles during sputtering, in the above sputtering target member, the molar ratio of carbides to the total of carbon and carbides is preferably 0.25 or more, more preferably 0.4 or more, still more preferably 0.6 or more, more preferably 0.8 or more, and most preferably 1.0.

The above-mentioned sputtering target, as the third element, one or two or more metal elements selected from Cr, Ru, B, Ti, Si and Mn have a total content of 30 mol% or less, for example, 0.01 to 20 mol%, and typically may contain 0.05～10mol%. These are metals added as needed in order to improve the characteristics of the magnetic recording layer. The compounding ratio can be adjusted in various ways within the above-mentioned range, and all can maintain effective characteristics as a magnetic recording layer. It should be noted that in the present invention, B is also treated as a metal. In the case where the above-mentioned third elements are not elemental metals or alloys, but exist in the form of carbides, oxides, nitrides or carbonitrides, they are not the third elements specified here, but shall be regarded as the above-mentioned handling of non-magnetic materials.

(1-2. Relative density)

In one embodiment of the sputtering target member of the present invention, the relative density is preferably 90% or more, more preferably 95% or more. The relative density can be, for example, 90% to 100%. This reduces the occurrence of abnormal discharge (arcing) during film formation, and a uniform thin film can be produced. In this specification, the relative density is a value obtained by dividing the actually measured density of the sputtering target member by the calculated density (also referred to as theoretical density). The measured density was determined by the Archimedes method. The calculated density is the density when it is assumed that the components of the raw material powder of the target member are mixed without diffusing or reacting with each other, and is calculated by the following formula.

Formula: Calculation density = Σ (the molecular weight of the constituents of the raw powder × the molar concentration of the constituents of the raw powder) / Σ (the molecular weight of the constituents of the raw powder × the molar concentration of the constituents of the raw powder / the molar concentration of the constituents of the raw powder Document Value Density)

Here, Σ means the sum of all components of the target member except impurities.

The sputtering target part, if necessary, can be bonded to a substrate such as a back plate or a back tube, and installed in a sputtering apparatus as a sputtering target assembly. A sputtering target member may be directly mounted in a sputtering apparatus as a sputtering target without using a base material.

(2. Preparation method)

The sputtering target member of the present invention can be produced using a powder sintering method, for example, by the following method.

First, raw material powders are prepared according to the composition of the target sputtering target part. As the raw material powder, for example, in addition to Co powder, Pt powder, and carbide powder, one or more non-magnetic materials selected from carbon powder, oxide powder, nitride powder, and carbonitride powder can be cited. of powder. In addition, one or two or more metal powders selected from Cr, Ru, B, Ti, Si, and Mn may be prepared.

The purity of the raw material powder is preferably 90 mol% or higher, more preferably 95 mol% or higher, still more preferably 99.9 mol% or higher. In a typical embodiment, the raw material powder does not contain other components other than the indicated components and unavoidable impurities.

The upper limit of the median diameter (D50) of the raw material powder is preferably 200 μm or less, more preferably 100 μm or less, still more preferably 50 μm or less, and still more preferably 10 μm or less in order to achieve a uniform structure. In addition, the lower limit of the median diameter of the raw material powder is preferably 0.1 μm or more, more preferably 0.3 μm or more, still more preferably 0.5 μm or more, for the reason of preventing oxidation of the raw material powder. The median diameter can be adjusted by crushing or sieving.

Next, the prepared raw material powder is weighed to obtain a desired component, and pulverization and mixing are combined using a known method such as a ball mill to obtain a mixed powder. At this time, it is preferable to enclose an inert gas in the crushing container to suppress oxidation of the raw material powder as much as possible. Examples of the inert gas include Ar and N ₂ gas.

The upper limit of the median diameter (D50) of the mixed powder is preferably 20 μm or less, more preferably 10 μm or less, and still more preferably 5 μm or less in order to achieve a uniform structure. In addition, the lower limit of the median diameter of the mixed powder is preferably 0.1 μm or more, more preferably 0.3 μm or more, still more preferably 0.5 μm or more, for the reason of preventing oxidation of the mixed powder.

In the present invention, the median diameter of each raw material powder and mixed powder refers to the particle diameter (D50) at which the volume-based cumulative value of the particle size distribution obtained by the laser diffraction and scattering method is 50%. In the examples, the powder was dispersed in an ethanol solvent and measured using a particle size distribution measuring device model LA-920 manufactured by Horiba Seisakusho. Refractive index, using the value of cobalt metal.

The mixed powder obtained in this way is molded and sintered in a vacuum atmosphere or an inert gas atmosphere using a hot press method. In addition, various pressure sintering methods such as the plasma discharge sintering method can be used in addition to the above-mentioned hot pressing method. In particular, hot isostatic pressing (HIP) is effective for increasing the density of the sintered body. From the viewpoint of increasing the density of the sintered body, hot pressing and hot isostatic pressing (HIP) are preferably performed in this order.

The upper limit of the holding temperature during sintering varies depending on the target composition, but is preferably 1500°C or lower, more preferably 1400°C or lower, and still more preferably 1200°C or lower in order to prevent coarsening of crystal grains. In addition, the lower limit of the holding temperature during sintering is preferably 600°C or higher, more preferably 650°C or higher, and still more preferably 700°C or higher in order to avoid a decrease in the density of the sintered body.

The lower limit of the pressing pressure during sintering is preferably 10 MPa or more, more preferably 15 MPa or more, and still more preferably 20 MPa or more in order to promote sintering. In addition, the upper limit of the pressing pressure during sintering is preferably 70 MPa or less, more preferably 50 MPa or less, and still more preferably 40 MPa or less in consideration of the strength of the mold.

In order to increase the density of the sintered body, the lower limit of the sintering time is preferably 0.1 hour or more, more preferably 0.2 hour or more, still more preferably 0.5 hour or more. In addition, in order to prevent coarsening of crystal grains, the upper limit of the sintering time is preferably 10 hours or less, more preferably 5 hours or less, and still more preferably 2 hours or less.

The sputtering target member according to one embodiment of the present invention can be produced by forming the obtained sintered body into a desired shape using a lathe. The shape of the target is not particularly limited, and examples thereof include a flat plate (including a disc shape and a rectangular plate shape) and a cylindrical shape. In one embodiment, the sputtering target member of the present invention is particularly useful as a sputtering target member for forming a magnetic thin film having a granular structure.

(3. Film forming method)

In one embodiment, the present invention provides a film forming method including the step of performing sputtering using the above-mentioned sputtering target member. Sputtering conditions can be appropriately set.

[Example]

Hereinafter, examples and comparative examples of the present invention are shown together, but the examples and comparative examples are provided for better understanding of the present invention and its advantages, and are not intended to limit the present invention.

(1. Production of sputtering target components)

As raw material powders, the following powders were prepared. All are high-purity products of 99.9% by mass or more, and do not contain other components other than the indicated components and unavoidable impurities. Screening can be performed to properly adjust the median diameter of these powders.

Co powder: median diameter (D50) = 3.3 μm

Pt powder: median diameter (D50) = 21.8 μm

Cr powder: median diameter (D50) = 2.7 μm

B powder: Median diameter (D50) = 3.9 μm

C powder: median diameter (D50) = 25.5 μm

B ₄ C powder: Median diameter (D50) = 0.5 μm

Cr ₃ C ₂ powder: median diameter (D50) = 1.2 μm

TiC powder: median diameter (D50) = 5.1 μm

B ₂ O ₃ powder: Median diameter (D50) = 0.5 μm

_TiO2 powder: median diameter (D50) = 0.9 μm

CoO powder: median diameter (D50) = 2.1 μm

Next, the above-mentioned raw material powders were generally pulverized while mixing them using zirconia balls as pulverizing media and using a ball mill so that the molar ratios of the raw material components described in Table 1 were obtained according to the test numbers. The median diameters (D50) of the obtained mixed powders were all about 0.5 to 5.0 μm. Next, the obtained mixed powder was filled in a mold made of carbon, and sintered by hot pressing in a vacuum atmosphere and hot isostatic pressing (HIP) in an Ar atmosphere. Hot pressing is carried out at a holding temperature of 800-1100° C. and a pressing pressure of 20-30 MPa for 1-2 hours. In order to increase the density, hot isostatic pressing (HIP) is performed after hot pressing. Thereafter, the HIPed sintered body was ground using a general-purpose lathe and a surface milling machine to obtain a disk-shaped sputtering target member with a diameter of 180 mm and a thickness of 5 mm.

(2. Relative density)

For each sputtering target member obtained through the above steps, the relative density was measured according to the method described above (relative density=measured density/theoretical density×100%). The results are shown in Table 1.

〔Table 1-1〕

[Table 1-2]

(3. Number of particles)

Each sputtering target member obtained through the above steps was mounted on a magnetron sputtering device (C-3010 sputtering system manufactured by Canon Anelva Co., Ltd.), and sputtering was performed. The conditions for sputtering were 1kW input power, 1.7Pa Ar gas pressure, pre-sputtering for a total of 2 hours, and then film formation on a silicon substrate with a diameter of 4 feet for 20 seconds. Then, the number of particles with a particle diameter of 0.07 μm or more adhering to the substrate was measured by a surface foreign matter inspection device (Candela CS920 manufactured by KLA-Tencor Corporation). The results are shown in Table 2.

〔Table 2〕

Comparing Example 1, Example 2, and Comparative Example 1 having the same components except for carbon and carbides, they were the same in that the molar concentration of the C source was 2 mol%. However, compared with Comparative Example 1 using only carbon as the C source, the number of fine particles in Example 1 and Example 2 using only carbide as the C source was smaller. Comparing Example 1 with Example 2, it can be seen that the use of B ₄ C as the carbide drastically reduces the number of particles.

Comparing Example 3, Example 4, Comparative Example 2, and Comparative Example 3 having the same components except for carbon and carbides, they were the same in that the molar concentration of the C source was 5 mol%. However, Comparative Example 2, Example 3, and Example 4 in which carbide was used as the C source were smaller in number of particles than in Comparative Example 3 in which only carbon was used as the C source. Comparing Comparative Example 2, Example 3, and Example 4, it can be seen that as the content ratio of carbides increases, the number of particles decreases. In addition, compared with Comparative Example 2 having a carbide concentration of less than 1.5 mol%, the decrease in the number of particles in Examples 3 and 4 having a carbide concentration of 1.5 mol% or more is more remarkable.

The above description is only a preferred feasible embodiment of the present invention, and all equivalent changes made by applying the description of the present invention and the scope of the patent application should be included in the scope of the patent of the present invention.

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Claims (8)

A sputtering target component for a magnetic recording layer, containing: 10 to 70 mol% of Co, 5 to 30 mol% of Pt, 1.5 to 10 mol% of carbides, and a total of 0 to 30 mol% of carbon, oxides, and nitrogen One or two or more non-magnetic materials selected from compounds and carbonitrides. The sputtering target member for a magnetic recording layer according to claim 1, wherein the molar ratio of the carbide to the sum of the carbon and the carbide is 0.25 or more. The sputtering target member for a magnetic recording layer according to claim 1 or 2, which contains one or two or more selected from B ₄ C, Cr ₃ C ₂ and TiC as carbides. The sputtering target member for a magnetic recording layer according to Claim 3, which contains 1.5 to 10 mol% of one or two or more selected from B ₄ C, Cr ₃ C ₂ and TiC in total. The sputtering target member for a magnetic recording layer according to claim 1 or 2, wherein one or two or more metal elements selected from Cr, Ru, B, Ti, Si, and Mn are contained in a total of 30 mol% or less. The sputtering target member for a magnetic recording layer according to claim 1 or 2, wherein the relative density of the sputtering target member for a magnetic recording layer is 90% or more. A sputtering target assembly comprising the sputtering target component for a magnetic recording layer according to any one of Claims 1 to 6, and a back tube or a back plate joined to the sputtering target component. A film forming method comprising sputtering the sputtering target member for a magnetic recording layer according to any one of Claims 1 to 6.