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 sputtering targets and sputtering target assemblies, and primarily to sputtering targets for the production of films for HDDs. [Background technology]

[0002] The layers constituting hard disk drives (HDDs) that employ perpendicular magnetic recording are made of materials based on ferromagnetic metals such as Co, Fe, and Ni, and the recording layer is often made of a composite material consisting of a ferromagnetic alloy, such as a Co-Cr, Co-Pt, Co-Cr-Pt, or Fe-Pt alloy, with Co or Fe as the main component, and a non-magnetic inorganic material. Thin films for magnetic recording media such as hard disk drives are often produced by sputtering a sputtering target containing the above materials, due to their high productivity.

[0003] In general, sputtering targets are manufactured by first crushing and mixing raw material powders, and then hot-pressing the resulting mixture to obtain a sintered body. To increase the density of the sintered body, HIP (Hot Isostatic Pressing) processing may then be performed. The sintered body thus obtained is then machined on a lathe to produce a target of a desired shape (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6030271 [Patent Document 2] Patent No. 6305881 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, a composite material composed of a ferromagnetic alloy such as an Fe-Pt alloy and a nonmagnetic inorganic material is useful as a recording layer for HDDs. However, when a sintered body having a structure in which oxides are dispersed in a base metal containing Fe and Pt is produced as a sputtering target for producing such a recording layer, the sintered body having this composition is relatively brittle, and there is a problem that cracks and breakage occur during the production process.

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

[0007] The above problems are solved by the present invention, which is specified as follows. 1. A composition comprising: (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 balance; the atomic ratio of the (1) Fe to the (2) Pt is 34 to 55 at %, the total concentration of the (1) Fe and the (2) Pt is 50 mol% or more, the total content of the element (3) is 0.5 to 15 mol%, The remainder of the (4) is an oxide, which may selectively contain impurities, and the volume fraction of the oxide is 40 vol.% or more, A sputtering target having a bending strength of 300 MPa or more. 2. The sputtering target according to 1 above, wherein the oxide contains an oxide of Si. 3. The sputtering target according to 2 above, 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 according to any one of 1 to 3 above, a backing plate bonded to the sputtering target; 1. A sputtering target assembly comprising: [Effects of the Invention]

[0008] According to the 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 breakage during the manufacturing process. DETAILED DESCRIPTION OF THE INVENTION

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

[0010] <Sputtering target> The shape of the sputtering target according to the embodiment of the present invention is not particularly limited, and may be a flat plate (including a disk or rectangular plate), a cylindrical shape, 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 balance. The balance in (4) is an oxide and may selectively contain impurities. The sputtering target according to an embodiment of the present invention comprises a metal phase containing ferromagnetic materials Fe and Pt, and a phase other than the metal phase containing an oxide, and can function as 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 as follows: 100-X Pt X In this case, X satisfies the relationship 34≦X≦55. When the Fe and Pt in the sputtering target satisfy this atomic ratio, the function as a magnetic thin film is improved. The atomic ratio of Fe to Pt is preferably 40≦X≦53, and more preferably 44≦X≦51.

[0013] The sputtering target according to an embodiment of the present invention has a total concentration of Fe and Pt of 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, it is preferably 80 mol% or less. Furthermore, the total concentration of Fe and Pt is more preferably 50 to 75 mol%, and even more preferably 50 to 70 mol%.

[0014] A sputtering target according to an embodiment of the present invention contains 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 in a total content of 0.5 to 15 mol%. These elements, along with Fe and Pt, are components of the metal phase, and containing 0.5 to 15 mol% further improves the magnetic properties of a sputtering target primarily composed of Fe and Pt. 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 an embodiment of the present invention may contain, as the remainder, an oxide and may selectively contain impurities. A particularly preferable magnetic thin film can be obtained by using SiO2 as the oxide. Furthermore, 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 to further improve magnetic properties.

[0016] The sputtering target according to the embodiment of the present invention has an oxide volume fraction of 40 vol.% or more. When the oxide volume fraction in the sputtering target is 40 vol.% or more, the magnetic properties are further improved. There is no particular upper limit to the oxide volume fraction in the sputtering target, but from the viewpoint that an excessive amount of oxide deteriorates the magnetic properties, it is preferably 60 vol.% or less. Furthermore, the oxide volume fraction in the sputtering target is more preferably 40 to 55 vol.%, and even more preferably 40 to 50 vol.%. The oxide volume fraction can be calculated from the composition of the target, and the volume of each component contained in the target is calculated by multiplying the volume of each component by (content of each material: mol) x (molecular weight of each material: g / mol) x (reciprocal of density of each material: cm 3 Next, the volume fraction of oxides can be calculated by dividing the total volume of only oxides by the total volume of all components.

[0017] Impurities selectively contained in the remainder of the sputtering target according to the embodiment of the present invention include metal elements not included 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 of the impurities selectively contained in the remainder of the sputtering target according to the embodiment of the present invention may be 0.5 mol% or less, or may be 0.15 mol% or less. Furthermore, impurities can be analyzed by collecting an analytical sample from the sputtering target and using infrared absorption spectroscopy, an ICP optical emission spectrometer, GDMS (glow discharge mass spectrometry), or the like. The amount and shape of the analytical sample vary depending on the analytical method used, and the optimal amount and shape for each method can be selected.

[0018] The sputtering target according to an embodiment of the present invention has a bending strength of 300 MPa or more. A bending strength of 300 MPa or more can effectively suppress the occurrence of cracks and breakage during the manufacturing process. The bending strength was measured by preparing seven test specimens, measuring their three-point bending strength, and calculating the average value, as described below. Here, the three-point bending strength indicates the maximum bending stress when a load is applied to a sample by a predetermined method, causing the sample to break. Breaking of a sample occurs when a crack propagates from one surface of the sample to the other surface. In other words, a high maximum bending stress means that the sample will not break even up to a high maximum bending stress. Therefore, it is believed that a high maximum bending stress makes it difficult for a crack to propagate from one surface to the other surface. In other words, by increasing the bending strength, a target can be obtained that is less susceptible to crack and breakage propagation, and cracks and breakage are less likely to propagate even when stress such as bending is applied during the manufacturing process, which is believed to effectively suppress the occurrence of cracks and breakage. The sputtering target according to the embodiment of the present invention preferably has a bending strength of 350 MPa or more, more preferably 400 MPa or more, even more preferably 450 MPa or more, and even more preferably 500 MPa or more.

[0019] The bending strength of the sputtering target according to the embodiment of the present invention can be measured as follows. First, seven test pieces are prepared by cutting out the sputtering target. As a specific example of the cutting method, the sputtering target is machined to a thickness of 3 mm using a lathe, and then cut into pieces measuring 4 mm x 35 mm using electrical discharge wire machining. Since the surface is oxidized, the surface is polished with #120 abrasive paper to remove the oxide film and prepare the sample. Next, the three-point bending strength of the test piece is measured under the following measurement conditions, and the average value is taken as the bending strength of the sputtering target. <Measurement conditions> A benchtop material testing machine (STB-1225S) manufactured by A&D Corporation can be used as the measuring device. Measurement of the bending strength of the sputtering target according to the embodiment of the present invention can be performed with reference to JIS R 1601:2008, "Test Method for Bending Strength of Fine Ceramics." Table 1 shows the conditions for measuring the bending strength of the sputtering target according to the embodiment of the present invention and the conditions for measuring bending strength specified in JIS R 1601:2008. As shown in Table 1, the conditions for measuring the bending strength of the sputtering target according to the embodiment of the present invention differ from the conditions for measuring bending strength specified in JIS R 1601:2008 only with respect to the "radius of curvature of the support," "test piece length," "parallelism," "edge of the test piece," "roughness Ra of the test piece," and "number of test pieces."

[0020] [Table 1]

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

[0022] <Method for manufacturing sputtering targets> A method for producing a sputtering target according to an embodiment of the present invention will be described in detail below. The sputtering target according to the embodiment of the present invention can be produced by a powder sintering method. First, powders of the respective metal elements are prepared. Alternatively, alloy powders of these metals (e.g., Fe-Pt powder) may be used instead of the powders of the respective metal elements. 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 compact will contain a large amount of impurities, which may result in problems such as the failure to obtain the desired physical properties (e.g., generation of particles due to arcing). These raw materials can be appropriately prepared based on the composition and purity of the desired sintered compact.

[0023] These metal powders are then weighed to achieve the desired composition and mixed using a mixer, which also serves as a mill. Non-magnetic particles may also be mixed with the metal powder at this stage. Mixing devices such as a ball mill or mortar can be used, but a powerful mixing method such as a ball mill is preferable. Considering the risk of oxidation during mixing, mixing is preferably performed in an inert gas atmosphere or vacuum. The mixing time is set to 0.1 to 48 hours. Increasing the mixing time of the raw materials can reduce the size of the oxides in the oxide phase, thereby increasing the bending strength of the sputtering target. Oxides are known to have lower toughness than metals. In sintered compacts with a structure in which oxides are dispersed in the base metal, cracks often originate from the oxide phase, which has low toughness. By dispersing these oxide particles more finely, the proportion of relatively coarse oxides in the sintered compact is reduced, suppressing crack generation and improving bending strength. On the other hand, shortening the mixing time of the raw materials can increase the size of the oxides in the oxide phase. From this perspective, the bending strength of the sputtering target can be controlled by adjusting the mixing time of the raw materials.

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

[0025] The sintered body is then removed from the hot press and subjected to HIP (Hot Isostatic Pressing). HIP is an effective method for increasing 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 pressure is 100 MPa or more. The sintered body thus obtained is then machined into the desired shape on a lathe to produce a sputtering target.

[0026] <Film formation method using sputtering targets> The sputtering target according to the embodiment of the present invention can be used to form a thin film that mainly constitutes a magnetic recording medium. Specifically, a sputtering device is used to sputter the surface of the sputtering target with accelerated argon ions, releasing particles (sputtered particles) from the sputtering target, and depositing the sputtered particles on the surface of a substrate previously positioned opposite the sputtering target, thereby forming a thin film on the surface of the substrate. Sputtering conditions can be appropriately set depending on the desired film thickness, composition, etc. [Example]

[0027] The following examples of the present invention are provided for a better understanding of the present invention and its advantages, but 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 out to have a composition of (30-45)Fe-(30-45)Pt-(5-15)Ag-(5-25)SiO2 (mol%). The raw material powders were adjusted so that the total composition was 100 mol%. Amorphous SiO2 powder was used. Next, the weighed Fe powder, Pt powder, Ag powder, and SiO2 powder were placed in a 5 L ball mill pot along with zirconia balls 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. A pressure of 30 MPa was applied from the start of heating to the end of holding. After the holding time was completed, the sintered body was allowed to cool naturally in the chamber. Thereafter, the sintered body removed from the hot-pressing 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 Ar gas pressure was gradually increased from the start of heating, and a pressure of 150 MPa was applied during the holding time. After the holding time was completed, the body was allowed to cool naturally in the furnace. In this way, a sputtering target according to Example 1 was produced.

[0030] <Example 2, Comparative Example 1> The sputtering targets of Example 2 and Comparative Example 1 were produced in the same manner as in Example 1. The mixing time of the raw material powders, the hot pressing temperature, and the HIP holding temperature were set under the conditions shown in Table 2.

[0031] Oxide volume ratio The oxide volume fraction was evaluated by calculating the volume of each component contained in the target as follows: (content of each material: mol) x (molecular weight of each material: g / mol) x (reciprocal of density of each material: cm 3 Next, the volume fraction of oxides was calculated by dividing the total volume of oxides by the total volume of all components.

[0032] Bending strength Seven test pieces were prepared by cutting out a sample of the sputtering target. The sputtering target was machined to a thickness of 3 mm using a lathe, and then cut into pieces measuring 4 mm x 35 mm using electrical discharge wire machining. Next, since the surface was oxidized, the surface was polished with #120 abrasive paper to remove the oxide film, and the sample was prepared. Next, the three-point bending strength 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 Corporation was used as the measuring device. The bending strength of the sputtering target according to this test example was measured with reference to JIS R 1601:2008 "Test method for bending strength of fine ceramics," and was carried out under 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 according to this test example differ from the bending strength measurement conditions described in JIS R 1601:2008 only for the "radius of curvature of the support," "test piece length," "parallelism," "edge of the test piece," "roughness Ra of the test piece," and "number of test pieces."

[0033] Cracks The surface of each of the sputtering targets of the examples and comparative examples was visually inspected to determine whether or not any cracks were present. Based on this evaluation, it was determined whether or not the occurrence of cracks or breakage during the manufacturing process was suppressed.

[0034] [Table 2]

[0035] <Consideration> According to Table 2, the sputtering targets according to 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 balance, in which the atomic ratio of (1) Fe to (2) Pt was 34 to 55 at%, the total concentration of (1) Fe and (2) Pt was 50 mol% or more, the total content of (3) element was 0.5 to 15 mol%, the balance of (4) was an oxide, the volume fraction of the oxide was 40 vol.% or more, and the bending strength was 300 MPa or more. Therefore, the occurrence of cracks and breakage during the manufacturing process was suppressed. In contrast, the bending strength of Comparative Example 1 was less than 300 MPa, which resulted in cracks and breakage 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, and Zn; and (4) the balance, the atomic ratio of the (1) Fe to the (2) Pt is 34 to 55 at %, The total concentration of the (1) Fe and the (2) Pt is 50 mol% or more, the total content of the element (3) is 0.5 to 15 mol%, The remainder of the (4) is an oxide, which may selectively contain impurities, and the volume fraction of the oxide is 40 vol.% or more, A sputtering target having a bending strength of 300 MPa or more.

2. The sputtering target of claim 1 , wherein the oxide comprises an oxide of Si.

3. 3. The sputtering target according to claim 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. The sputtering target according to any one of claims 1 to 3, a backing plate bonded to the sputtering target; 1. A sputtering target assembly comprising:

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