Sputtering target and sputtering target assembly

Abstract

To provide a sputtering target and a sputtering target assembly capable of favorably suppressing occurrence of cracks and fractures during a manufacturing process.SOLUTION: A sputtering target having (1) Fe, (2) Pt, (3) one or more elements selected from Ag, Au, B, Co, Cr, Cu, Ga, Ge, Mn, Mo, Nb, Ni, Pd, Re, Rh, Ru, Si, Sn, Ta, W, V, and Zn, and (4) the remainder, the atomic ratio between (1) Fe and (2) Pt being 34-55 at%, the total concentration of (1) Fe and (2) Pt being 50 mol% or above, the total content of the elements (3) being 0.5-15 mol%, the remainder (4) being an oxide and optionally including impurities, the volume ratio of the oxide being 40 vol.% or more, and having a bending strength of 300 MPa or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a sputtering target and a sputtering target assembly, and mainly relates to a sputtering target for manufacturing a film of an HDD.

Background Art

[0002] For the layers constituting a hard disk drive (HDD) adopting a perpendicular magnetic recording method, for example, materials based on Co, Fe, and Ni which are ferromagnetic metals are used. For the recording layer, composite materials composed of ferromagnetic alloys such as Co-Cr-based, Co-Pt-based, Co-Cr-Pt-based, Fe-Pt-based, etc. with Co or Fe as the main component and non-magnetic inorganic materials are often used. Thin films of magnetic recording media such as such hard disk drives are often produced by sputtering a sputtering target containing the above materials as components due to high productivity.

[0003] In general, the manufacturing of a sputtering target first obtains a sintered body by hot pressing a mixture obtained by pulverizing and mixing raw material powders. After that, HIP (Hot Isostatic Pressing) processing may be performed to improve the density of the sintered body. The sintered body thus obtained is processed by a lathe to manufacture a target having a predetermined shape (Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] As mentioned above, composite materials consisting of ferromagnetic alloys such as Fe-Pt and non-magnetic inorganic materials are useful as recording layers for HDDs. However, when manufacturing a sintered body with a structure in which oxides are dispersed in a base metal containing Fe and Pt as a sputtering target for such a recording layer, the sintered body with this composition is relatively brittle, and there is a problem of cracks and fractures occurring during the manufacturing process.

[0006] Therefore, the object of the embodiments of the present invention is to provide a sputtering target and a sputtering target assembly that can effectively suppress the occurrence of cracks and fractures during the manufacturing process. [Means for solving the problem]

[0007] The above problems are solved by the present invention, which is defined as follows. 1. (1) Fe, (2) Pt, (3) one or more elements selected from Ag, Au, B, Co, Cr, Cu, Ga, Ge, Mn, Mo, Nb, Ni, Pd, Re, Rh, Ru, Si, Sn, Ta, W, V, Zn, and (4) the remainder. The atomic ratio of (1) Fe to (2) Pt is 34-55 at%, The total concentration of (1) Fe and (2) Pt is 50 mol% or more. The total content of the elements in (3) above is 0.5 to 15 mol%, The remainder of (4) above is an oxide, which may selectively contain impurities, and the volume fraction of the oxide is 40 vol.% or more. A sputtering target with a bending strength of 300 MPa or more. 2. The sputtering target according to claim 1, wherein the oxide contains an oxide of Si. 3. The sputtering target according to 2, wherein the oxide further contains one or more oxides of elements selected from Al, B, Ba, Be, Ca, Ce, Cr, Dy, Er, Eu, Ga, Gd, Ho, Li, Mg, Mn, Nb, Nd, Pr, Sc, Sm, Sr, Ta, Tb, Ti, V, Y, Zn, and Zr. 4. A sputtering target as described in any of items 1 to 3 above, A backing plate bonded to the sputtering target, A sputtering target assembly equipped with the following features. [Effects of the Invention]

[0008] According to embodiments of the present invention, it is possible to provide a sputtering target and a sputtering target assembly that can effectively suppress the occurrence of cracks and fractures during the manufacturing process. [Modes for carrying out the invention]

[0009] Next, embodiments for carrying out the present invention will be described in detail. The present invention is not limited to the following embodiments, and it should be understood that appropriate design changes, improvements, etc., can be made based on the ordinary knowledge of those skilled in the art, without departing from the spirit of the invention.

[0010] <Sputtering target> The shape of the sputtering target according to the embodiment of the present invention is not particularly limited, but may be flat (including disc-shaped or rectangular plate-shaped), cylindrical, or any other shape.

[0011] A sputtering target according to an embodiment of the present invention comprises (1) Fe, (2) Pt, (3) one or more elements selected from Ag, Au, B, Co, Cr, Cu, Ga, Ge, Mn, Mo, Nb, Ni, Pd, Re, Rh, Ru, Si, Sn, Ta, W, V, and Zn, and (4) the remainder. The remainder of (4) is an oxide and may selectively contain impurities. A sputtering target according to an embodiment of the present invention has a metallic phase containing Fe and Pt, which are ferromagnetic materials, and a phase containing oxides other than the metallic phase, and can be given the function of a magnetic thin film.

[0012] In the sputtering target according to the embodiment of the present invention, the atomic ratio of Fe to Pt is 34 to 55 at%. That is, the atomic ratio of Fe to Pt in the sputtering target is Fe 100-X Pt X In this case, X satisfies 34 ≤ X ≤ 55. The function of the magnetic thin film is improved when Fe and Pt in the sputtering target satisfy this atomic ratio. The atomic ratio of Fe and Pt is preferably 40 ≤ X ≤ 53, and more preferably 44 ≤ X ≤ 51.

[0013] In the sputtering target according to the embodiment of the present invention, the total concentration of Fe and Pt is 50 mol% or more. When the total concentration of Fe and Pt in the sputtering target is 50 mol% or more, the magnetic properties are improved. There is no particular upper limit to the total concentration of Fe and Pt, but from the viewpoint of ensuring grain boundary material, 80 mol% or less is preferred. Furthermore, the total concentration of Fe and Pt is more preferably 50 to 75 mol%, and even more preferably 50 to 70 mol%.

[0014] The sputtering target according to the embodiment of the present invention has a total content of 0.5 to 15 mol% of one or more elements selected from Ag, Au, B, Co, Cr, Cu, Ga, Ge, Mn, Mo, Nb, Ni, Pd, Re, Rh, Ru, Si, Sn, Ta, W, V, and Zn. These elements, together with Fe and Pt, are components of the metallic phase, and their inclusion at 0.5 to 15 mol% further improves the magnetic properties of the sputtering target, which has Fe and Pt as its basic components. The content of these elements is more preferably 2 to 13 mol%, and even more preferably 4 to 11 mol%.

[0015] The sputtering target according to the embodiment of the present invention is a remainder oxide and may selectively contain impurities. When SiO2 is used as the oxide, a particularly preferable magnetic thin film can be obtained. In addition to SiO2, the oxide may further contain one or more oxides of elements selected from Al, B, Ba, Be, Ca, Ce, Cr, Dy, Er, Eu, Ga, Gd, Ho, Li, Mg, Mn, Nb, Nd, Pr, Sc, Sm, Sr, Ta, Tb, Ti, V, Y, Zn, and Zr in order to further improve the magnetic properties.

[0016] In the sputtering target according to the embodiment of the present invention, the volume fraction of oxide is 40 vol.% or more. When the volume fraction of oxide in the sputtering target is 40 vol.% or more, the magnetic properties are further improved. There is no particular upper limit to the volume fraction of oxide in the sputtering target, but from the viewpoint that the magnetic properties deteriorate if there is too much oxide, 60 vol.% or less is preferred. Furthermore, the volume fraction of oxide in the sputtering target is more preferably 40 to 55 vol.%, and even more preferably 40 to 50 vol.%. The volume fraction of oxide can be calculated from the composition of the target, and the volume of each component contained in the target is calculated as (content of each material: mol) × (molecular weight of each material: g / mol) × (reciprocal of density of each material: cm) 3 It is calculated using the formula ( / g). Next, the volume fraction of oxides can be calculated by dividing the total volume of oxides alone by the total volume of all components.

[0017] Examples of impurities selectively contained in the remainder of the sputtering target according to the embodiments of the present invention include metal elements not contained in the elements (1) to (3) above, and simple substances or compounds of elements such as C or N from gas components such as carbon dioxide and nitrogen in the atmosphere. The content rate of impurities selectively contained in the remainder of the sputtering target according to the embodiments of the present invention may be 0.5 mol% or less, or may be 0.15 mol% or less. Further, the impurities can be analyzed by collecting an analysis sample from the sputtering target and using an infrared absorption method, an ICP emission spectroscopic analyzer, GDMS (glow discharge mass spectrometry), or the like. The amount and shape of the analysis sample vary depending on the analysis method employed, and the optimal amount and shape of each method can be selected.

[0018] The sputtering target according to the embodiments of the present invention has a flexural strength of 300 MPa or more. When the flexural strength is 300 MPa or more, generation of cracks and fractures in the manufacturing process can be satisfactorily suppressed. The flexural strength is obtained by preparing seven test pieces as described later, measuring the three-point flexural strength, and calculating the average value thereof. Here, the three-point flexural strength indicates the maximum flexural stress when a load is applied to a sample by a predetermined method and the sample breaks. The breakage of the sample occurs when cracks progress from one surface of the sample to the other surface. That is, when the maximum flexural stress is high, it means that the sample does not break up to the high maximum flexural stress. Therefore, when the maximum flexural stress is high, it is considered that cracks are less likely to progress from one surface to the other surface. That is, by increasing the flexural strength, a target can be obtained in which cracks and fractures are less likely to progress, and even when stress such as bending is applied in the manufacturing process, cracks and fractures are less likely to progress, so it is considered that generation of cracks and fractures can be satisfactorily suppressed. The sputtering target according to the embodiments of the present invention preferably has a flexural strength of 350 MPa or more, more preferably 400 MPa or more, still more preferably 450 MPa or more, and still more preferably 500 MPa or more.

[0019] The bending strength of the sputtering target according to an embodiment of the present invention can be measured as follows. First, cut out the sputtering target and prepare seven test pieces. As a specific example of the cutting method, after machining the sputtering target to a thickness of 3 mm by lathe machining, cut it out to a size of 4 mm × 35 mm by wire electrical discharge machining. Since the surface is oxidized, polish the surface with #120 abrasive paper to remove the oxide film and prepare the sample. Next, measure the three-point bending strength of the test piece under the following measurement conditions, and take the average value as the bending strength of the sputtering target. <Measurement conditions> A tabletop material testing machine (STB-1225S) manufactured by A&D Company can be used as the measuring device. The measurement of the bending strength of the sputtering target according to an embodiment of the present invention can be performed by referring to JIS R 1601:2008 "Test Method for Flexural Strength of Fine Ceramics". Table 1 shows the measurement conditions for the bending strength of the sputtering target according to an embodiment of the present invention and the measurement conditions for the bending strength described in JIS R 1601:2008. As shown in Table 1, only for "Radius of curvature of the support", "Length of the test piece", "Parallelism", "Edges of the test piece", "Roughness Ra of the test piece", and "Number of test pieces", the measurement conditions for the bending strength of the sputtering target according to an embodiment of the present invention are different from the measurement conditions for the bending strength described in JIS R 1601:2008.

[0020]

Table 1

[0021] <Sputtering target assembly> The sputtering target according to an embodiment of the present invention may be joined to a backing plate as needed to form a sputtering target assembly. This sputtering target assembly can be mounted on a sputtering apparatus for use. Indium or indium tin can be used as the brazing material. Alternatively, the sputtering target according to an embodiment of the present invention may be mounted directly on the sputtering apparatus without using a backing plate. The material of the backing plate is not particularly limited and can be Cu, Ti, Mo, or alloys containing at least one of these (for example, Cu-Ni-Si alloy (e.g., C18000), CuZn alloy, CuCr alloy), etc. The material of the backing plate preferably has high thermal conductivity, and from this viewpoint, Cu is preferred.

[0022] <Method for manufacturing a sputtering target> The following describes in detail a method for manufacturing a sputtering target according to an embodiment of the present invention. A sputtering target according to an embodiment of the present invention can be manufactured by powder sintering. First, powders of each metal element are prepared. Alternatively, alloy powders of these metals (e.g., Fe-Pt powder) may be used instead of individual metal element powders. The purity of these raw materials is usually 2N (99% by mass) or higher, preferably 3N (99.9% by mass) or higher, and more preferably 4N (99.99% by mass) or higher. If the purity is lower than 2N, the sintered body will contain many impurities, which may result in the inability to obtain the desired physical properties (e.g., generation of particles due to arcing). These raw materials can be appropriately prepared based on the desired composition and purity of the sintered body.

[0023] These metal powders are then weighed to the desired composition and mixed using a mixing device, which also grinds them. Non-magnetic particles may also be mixed with the metal powders at this stage. A ball mill, mortar and pestle, etc., can be used as the mixing device, but it is preferable to use a powerful mixing method such as a ball mill. Also, considering the problem of oxidation during mixing, it is preferable to mix in an inert gas atmosphere or in a vacuum. The mixing time should be 0.1 to 48 hours. By increasing the mixing time of the raw materials, the oxide size of the oxide phase can be reduced, thereby increasing the bending strength of the sputtering target. Oxides are known to have lower toughness compared to metals. In sintered bodies having a structure in which oxides are dispersed in the base metal, crack initiation often occurs in the oxide phase, which has low toughness. By making these oxide particles finer and finely dispersing them, the proportion of relatively coarse oxides present in the sintered body is reduced, and crack initiation can be suppressed, thereby improving the bending strength. On the other hand, by shortening the mixing time of the raw materials, the oxide size of the oxide phase can be increased. From this viewpoint, the bending strength of the sputtering target can be controlled by adjusting the mixing time of the raw materials.

[0024] The mixed powder obtained in this way is molded and sintered using a hot press to produce a sintered body. Molding and sintering are not limited to hot pressing; plasma discharge sintering and hot hydrostatic sintering can also be used. The sintering conditions are 650 to 1400°C for 0.5 to 12 hours. Increasing the sintering temperature and / or the sintering time will increase the size of the oxide in the oxide phase. On the other hand, decreasing the sintering temperature and / or the sintering time will decrease the size of the oxide in the oxide phase. From this perspective, the size of the oxide in the oxide phase is controlled by adjusting the sintering temperature and sintering time, thereby controlling the bending strength of the sputtering target.

[0025] Subsequently, the sintered body removed from the hot press is subjected to HIP (Hot Isostatic Pressing). HIP is an effective method for improving the density of the sintered body. The holding temperature during HIP is 650-1100°C, the holding time is 0.5-12 hours, and the applied pressure is 100 MPa or more. Then, the sintered body obtained in this way is machined on a lathe to the desired shape to create a sputtering target.

[0026] <Method for forming thin films using a sputtering target> Using a sputtering target according to an embodiment of the present invention, thin films constituting magnetic recording media can be formed, primarily. Specifically, a sputtering apparatus is used to sputter the surface of the sputtering target with accelerated argon ions, releasing particles (sputtered particles) from the sputtering target. These sputtered particles are then deposited onto the surface of a substrate pre-positioned opposite, thereby forming a thin film on the substrate surface. The sputtering conditions can be appropriately set depending on the desired film thickness, composition, and other factors. [Examples]

[0027] Examples of the present invention are shown below, but these examples are provided to better understand the present invention and its advantages, and are not intended to limit the invention.

[0028] <Example 1> The sputtering target according to Example 1 was manufactured by the following manufacturing method. Fe powder, Pt powder, Ag powder, and SiO2 powder were prepared as raw material powders and weighed so that the composition was (30~45)Fe-(30~45)Pt-(5~15)Ag-(5~25)SiO2 (mol%). The raw material powders were prepared so that the total composition was 100 mol%. Amorphous SiO2 powder was used at this time. Next, the weighed Fe powder, Pt powder, Ag powder, and SiO2 powder were placed together with zirconia balls in a 5L ball mill pot and mixed for 4 hours.

[0029] Next, the mixed powder removed from the ball mill pot was filled into a carbon mold and hot-pressed. The hot-pressing conditions were a vacuum atmosphere, a heating rate of 300°C / hour, a holding temperature (sintering temperature) of 900°C, and a holding time (sintering time) of 2 hours. Pressurization was maintained at 30 MPa from the start of heating until the end of holding. After the end of holding, it was allowed to cool naturally in the chamber. Subsequently, the sintered body removed from the hot-press mold was subjected to HIP processing. The HIP processing conditions were a heating rate of 300°C / hour, a holding temperature of 850°C, and a holding time of 2 hours. The gas pressure of Ar gas was gradually increased from the start of heating, and pressurization was maintained at 150 MPa during holding. After the end of holding, it was allowed to cool naturally in the furnace. This produced the sputtering target according to Example 1.

[0030] <Example 2, Comparative Example 1> The sputtering targets for Example 2 and Comparative Example 1 were prepared in the same manner as in Example 1. The mixing time of the raw material powder, the hot press temperature, and the HIP holding temperature were carried out under the conditions shown in Table 2.

[0031] • Volume fraction of oxides The volume fraction of an oxide is evaluated by multiplying the volume of each component contained in the target by (content of each material: mol) × (molecular weight of each material: g / mol) × (reciprocal density of each material: cm³). 3 The volume fraction of oxides was calculated using the formula ( / g). Next, the volume fraction of oxides was calculated by dividing the total volume of oxides alone by the total volume of all components.

[0032] • Bending strength Seven test pieces were prepared by cutting out samples from a sputtering target. The cutting method involved machining the sputtering target to a thickness of 3 mm using a lathe, and then cutting it into 4 mm x 35 mm pieces using electrical discharge wire machining. Subsequently, since the surface was oxidized, the surface was polished with #120 grit sandpaper to remove the oxide film and prepare the samples. Next, the bending strength at three points was measured under the following measurement conditions, and the average value was taken as the bending strength of the sputtering target. <Measurement conditions> A benchtop material testing machine (STB-1225S) manufactured by A&D Company, Limited was used as the measuring device. The bending strength of the sputtering target in this test example was measured in reference to JIS R 1601:2008 "Test method for bending strength of fine ceramics" and carried out according to the "measurement conditions of this embodiment" shown in Table 1 above. That is, as shown in Table 1 above, the measurement conditions for the bending strength of the sputtering target in this test example differ from the measurement conditions for bending strength described in JIS R 1601:2008 only in terms of "radius of curvature of support", "length of test piece", "parallelism", "edge of test piece", "roughness Ra of test piece", and "number of test pieces".

[0033] • Crack For each example and comparative example, the sputtering target was visually inspected to determine whether any cracks were present or not. This evaluation was used to determine whether the occurrence of cracks and fractures during the manufacturing process was suppressed.

[0034] [Table 2]

[0035] <Consideration> According to Table 2, the sputtering targets in Examples 1 and 2 each contained (1) Fe, (2) Pt, (3) one or more elements selected from Ag, Au, B, Co, Cr, Cu, Ga, Ge, Mn, Mo, Nb, Ni, Pd, Re, Rh, Ru, Si, Sn, Ta, W, V, and Zn, and (4) the remainder. The atomic ratio of (1) Fe to (2) Pt was 34-55 at%, the total concentration of (1) Fe to (2) Pt was 50 mol% or more, the total content of the elements in (3) was 0.5-15 mol%, the remainder in (4) was an oxide, the volume fraction of the oxide was 40 vol.% or more, and the bending strength was 300 MPa or more. As a result, the occurrence of cracks and fractures during the manufacturing process was suppressed. In contrast, Comparative Example 1 had a bending strength of less than 300 MPa. As a result, cracks and fractures occurred during the manufacturing process.

Claims

1. (1) Fe, (2) Pt, (3) one or more elements selected from Ag, Au, B, Co, Cr, Cu, Ga, Ge, Mn, Mo, Nb, Ni, Pd, Re, Rh, Ru, Si, Sn, Ta, W, V, Zn, and (4) the remainder. The atomic ratio of (1) Fe to (2) Pt is 34 to 55 at%, The total concentration of (1) Fe and (2) Pt is 50 mol% or more. The total content of the elements in (3) above is 0.5 to 15 mol%, The remainder of (4) above is an oxide, which may selectively contain impurities, the volume fraction of the oxide is 40 vol.% or more, and the oxide contains SiO2. A sputtering target with a bending strength of 300 MPa or more.

2. The sputtering target according to claim 1, wherein the oxide further contains one or more oxides of elements selected from Al, B, Ba, Be, Ca, Ce, Cr, Dy, Er, Eu, Ga, Gd, Ho, Li, Mg, Mn, Nb, Nd, Pr, Sc, Sm, Sr, Ta, Tb, Ti, V, Y, Zn, and Zr.

3. A sputtering target according to claim 1 or 2, A backing plate bonded to the sputtering target, A sputtering target assembly equipped with the following features.

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