Mgo-tio sintered body target and method for manufacturing the same

Abstract

The present invention relates to a MgO-TiO sintered body target and a method for producing the same. A MgO-TiO sintered body containing 25 to 90 mol% of TiO, and the remainder containing MgO and inevitable impurities. The present invention aims to provide a high-density target capable of performing direct current (DC) sputtering with less powder generation at a high film deposition rate and a method for producing the same.

Description

[0001] This application is a divisional application of Chinese patent application No. 201480002503.0, filed on March 4, 2014. Technical Field

[0002] This invention relates to magnesium oxide-based targets for forming magnesium oxide layers in electronic devices such as magnetic recording media for disk drives and tunnel magnetoresistance (TMR) elements, and methods for manufacturing the same. In particular, it relates to sintered magnesium oxide-based targets for sputtering that are conductive and have high density, and methods for manufacturing the same. Background Technology

[0003] In recent years, with the miniaturization and high recording density of hard disks, research and development of magnetic recording media have been carried out, especially various improvements to the magnetic layer and substrate layer. The recording density of hard disks is increasing rapidly year by year, and it is believed that the current areal density of 600 Gbit / square inch will eventually reach 1 Tbit / square inch. When the recording density reaches 1 Tbit / square inch, the size of the recording bit will be less than 10 nm. At this point, it is foreseeable that paramagnetism caused by thermal fluctuations will become a problem, and it is also foreseeable that the materials currently used, such as those that improve crystal magnetic anisotropy by adding Pt to Co-Cr based alloys, will be insufficient. This is because magnetic particles that stably exhibit strong magnetism at a size of less than 10 nm require even higher crystal magnetic anisotropy.

[0004] For the reasons mentioned above, the FePt phase with an L10 structure has attracted attention as an ultra-high density recording medium material. The FePt phase with an L10 structure exhibits high crystal magnetic anisotropy and excellent corrosion resistance and oxidation resistance, thus it is expected to be a suitable material for magnetic recording medium applications. Furthermore, when using the FePt phase as an ultra-high density recording medium material, it is necessary to develop techniques to disperse ordered FePt magnetic particles in a way that aligns them with the highest possible density in a magnetically isolated state. To impart magnetic anisotropy to the FePt thin film, it is necessary to control the crystal orientation, which can be easily achieved by selecting a single-crystal substrate. It has been reported that magnesium oxide films are suitable as the substrate layer for FePt layers in order to achieve a perpendicular alignment of the magnetization orientation axis.

[0005] In addition, magnesium oxide films used as insulating layers (tunnel barriers) for magnetic heads (for hard disks) and TMR elements used in MRAM are also known. These magnesium oxide films were previously formed by vacuum evaporation, but recently, sputtering has been used to fabricate magnesium oxide films to easily simplify the manufacturing process and achieve large-area fabrication. The following are prior art documents.

[0006] Patent document 1 disclosed a magnesium oxide target, which is a magnesium oxide target composed of a sintered magnesium oxide body with a purity of 99.9% or higher and a relative density of 99% or higher. It has a microstructure with an average particle size of less than 60 μm and circular pores with an average particle size of less than 2 μm within the grains, and is capable of handling... Sputtering film formation speeds of over / minute are achieved. This is based on the following method: high-purity magnesium oxide powder is mixed with magnesium oxide micro-powder with an average particle size of less than 100 nm, followed by shaping, and then the shaped body undergoes primary and secondary sintering.

[0007] Patent document 2 discloses a magnesium oxide target, characterized in that it is composed of a sintered magnesium oxide body with a relative density of 99% or higher, and can be obtained by sputtering in an Ar atmosphere or an Ar-O2 mixed atmosphere. A film-forming rate of over / minute was proposed, and the following method was suggested: high-density magnesium oxide powder with an average particle size of 0.1–2 μm was subjected to a film-forming rate of 3 t / cm. 2 CIP forming is performed under the above pressure, and the resulting molded body is then sintered.

[0008] Patent document 3 described above discloses a target made of magnesium oxide, which is a magnesium oxide target composed of a sintered magnesium oxide body with a magnesium oxide purity of 99.9% or higher and a relative density of 99.0% or higher, capable of withstanding... The invention describes a sputtering film formation rate of over / minute and a method for forming a high-purity magnesium oxide powder by adding mixed fused magnesium oxide powder and magnesium oxide micro powder with an average particle size of less than 100 nm, followed by primary and secondary sintering of the formed body. It also describes the ability to form magnesium oxide films with good orientation, crystallinity and film properties at high film formation rates using sputtering.

[0009] The aforementioned patent document 4 proposes a target with MgO as the main component and its manufacturing method. The target has the objectives of low discharge voltage, sputter resistance during discharge, fast discharge response and insulation. In order to be used as a protective film for the dielectric layer of Ac type PDP, La particles, Y particles and Sc particles are dispersed into the target with MgO as the main component.

[0010] The above-mentioned patent document 5 proposes the following scheme: For a target with MgO as the main component, in order to improve the strength, fracture toughness and thermal shock resistance, LaB6 particles are dispersed in the MgO matrix, and reduction treatment in a reducing gas atmosphere before sintering, first sintering at a specified temperature and second sintering are performed.

[0011] Patent document 6 describes a method for manufacturing a target with MgO as the main component, specifying a relative density and an average grain diameter of 0.5–100 μm, and dispersing rare earth elements Sc, Y, La, Ce, Gd, Yb, and Nd into the MgO matrix. Patent document 7 proposes a method for manufacturing a high-density sintered body by sintering compacted MgO powder using a discharge plasma sintering method.

[0012] Patent documents 8 and 9 above propose the following scheme: to achieve an ultimate density of 3.568 g / cm³ 3 Good mechanical properties and thermal conductivity, and reduced atmospheric pollution caused by gas generation. By uniaxial pressure sintering, a large number of (111)-plane oriented MgO sintered bodies are obtained. MgO raw material powder with a particle size of less than 1 μm is uniaxially pressure sintered and then heat-treated at a temperature above 1273 K in an oxygen atmosphere. In this case, the raw material powder is MgO, and the method of increasing density is limited by the sintering conditions.

[0013] Patent document 10 proposes a target for forming a large-scale and uniform MgO film, and proposes the following scheme: The average grain diameter, density, flexural strength, and average roughness of the target surface centerline are specified, and the particle size of the raw material powder is made less than 1 μm. Then, after a granulation process, sintering is performed under specified load and temperature, and surface finishing is carried out to make the average roughness Ra of the target centerline less than 1 μm. Furthermore, patent document 11 describes forming a non-magnetic seed layer composed of any one of the following materials having a NaCl structure: MgO, NiO, TiO, or Ti carbides, between a non-magnetic substrate and a non-magnetic base layer in a perpendicular magnetic recording medium.

[0014] Existing technical documents

[0015] Patent documents

[0016] Patent Document 1: Japanese Patent Application Publication No. 10-130827

[0017] Patent Document 2: Japanese Patent Application Publication No. 10-130828

[0018] Patent Document 3: Japanese Patent Application Publication No. 10-158826

[0019] Patent Document 4: Japanese Patent Application Publication No. 10-237636

[0020] Patent Document 5: Japanese Patent Application Publication No. 11-6058

[0021] Patent Document 6: Japanese Patent Application Publication No. 11-335824

[0022] Patent Document 7: Japanese Patent Application Publication No. 11-139862

[0023] Patent Document 8: Japanese Patent Application Publication No. 2009-173502

[0024] Patent Document 9: International Publication No. WO2009 / 096384 (Single Volume)

[0025] Patent Document 10: Japanese Patent Application Publication No. 2000-169956

[0026] Patent Document 11: Japanese Patent Application Publication No. 2004-213869 Summary of the Invention

[0027] The problem that the invention aims to solve

[0028] In recent years, the demand for magnesium oxide films has been increasing for applications in electronic devices such as magnetic recording media for disk drives (hard disk drives) and tunneling magnetoresistance (TMR) elements. Since magnesium oxide is an insulating material, high-frequency (RF) sputtering is typically used. However, RF sputtering suffers from the following problems: slow film formation speed results in poor productivity, and the formation of dust particles degrades the film quality. Therefore, the objective of this invention is to provide a high-density target for direct current (DC) sputtering with fast film formation speed and low dust generation, as well as a method for manufacturing the same.

[0029] means for solving problems

[0030] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that by preparing a target containing a composite oxide of conductive titanium dioxide (TiO) mixed with magnesium oxide (MgO) having the same NaCl-type crystal structure and a lattice constant close to that of magnesium oxide, a conductive sintered body can be obtained, which can be DC sputtered. Moreover, the obtained film has the same crystal structure as magnesium oxide, so its function as a substrate layer is not impaired.

[0031] Based on the above findings, the present invention provides the following solutions.

[0032] 1) A MgO-TiO sintered body containing 25 to 90 mol% TiO, with the remainder consisting of MgO and unavoidable impurities.

[0033] 2) The MgO-TiO sintered body as described in 1) above is characterized in that its relative density is 95% or higher.

[0034] 3) The MgO-TiO sintered body as described in 1) or 2) above is characterized in that its bulk resistivity is below 10 Ω·cm.

[0035] 4) The MgO-TiO sintered body as described in any one of 1) to 3) above, characterized in that it contains two phases, TiO and MgO, and the region of the MgO phase with a longest diameter of 50 μm or more is 10 or less per mm. 2 .

[0036] 5) A method for manufacturing a MgO-TiO sintered body, comprising a method for manufacturing a sputtering sintered body containing 25 mol% or more and 90 mol% or less TiO in MgO, characterized in that a raw material powder comprising MgO powder with an average particle size of 10 μm or less and TiO powder with an average particle size of 50 μm or less is mixed, and the mixed raw material powder is subjected to a temperature of 1250–1450 °C and a temperature of 200 kgf / cm². 2 The MgO-TiO sintered body is produced by hot pressing under the above pressure.

[0037] Invention Effects

[0038] This invention provides a high-density magnesium oxide-based sintered body with low bulk resistivity. When used as a target, it offers the following advantages: film formation is significantly improved due to the ability to form a film via DC sputtering, and the amount of powder generated is low due to stable sputtering. Furthermore, it reduces the cost of the equipment by eliminating the need for the expensive RF power supply required for RF sputtering. Attached Figure Description

[0039] Figure 1 The image is a tissue image obtained by observing the target in Example 2 using a laser microscope.

[0040] Figure 2 The tissue image obtained by observing the target in Example 2 using a laser microscope (the image shows the tissue obtained by observing the target in Example 2 using a laser microscope). Figure 1 (Image scaled down by approximately 1 / 5). Detailed Implementation

[0041] One of the features of the MgO-TiO sintered body of the present invention is the addition of TiO to MgO. By adding conductive TiO, a conductive sintered body containing MgO-TiO can be obtained. Therefore, sputtering targets made using this sintered body can be used for DC sputtering, and the amount of powder particles generated during sputtering can be reduced.

[0042] As shown above, this invention imparts conductivity to the sintered body by adding conductive TiO, enabling DC sputtering. Importantly, the TiO possesses the same NaCl-type crystal structure as MgO and has a lattice constant close to that of MgO. It is an oxide like MgO but does not react with MgO to form intermediate compounds. Therefore, the film formed by sputtering exhibits superior performance compared to conventional films made solely of magnesium oxide, without compromising its properties.

[0043] In addition to TiO, other conductive materials that can be used in this invention include TiN, TiC, CrN, NbN, NbC, TaN, TaC, ZrN, ZrC, VN, and VC. From the perspective of lattice constant alone, TiC, VC, WC, and TiN are promising. However, these carbides or nitrides contain a large amount of oxygen impurities in their raw material powder. When mixed with MgO and sintered, these impurities may decompose, reduce the oxygen in MgO, or form intermediate compounds with MgO, which is believed to impair the original properties (lattice constant, etc.) of MgO, TiC, VC, WC, and TiN.

[0044] In the MgO-TiO sintered body of the present invention, the TiO content is 25 mol% or more and 90 mol% or less, preferably 35 mol% or more and 70 mol% or less. When it is less than 25 mol%, it is difficult to obtain a bulk resistance that can be DC sputtered. On the other hand, when it exceeds 90 mol%, the properties of the formed film are close to those of pure TiO, and the desired properties cannot be obtained, so it is not preferred.

[0045] It should be noted that in this invention, the addition of other materials is also included as long as DC sputtering can be performed without significantly altering the properties of the film.

[0046] Furthermore, for the MgO-TiO sintered body of the present invention, a relative density of 95% or higher is preferred. A relative density of 98% or higher is more preferable. When such a high-density sintered body is used as a sputtering target, the amount of powder generated during sputtering can be reduced.

[0047] Furthermore, for the MgO-TiO sintered body of the present invention, a bulk resistivity of 10 Ω·cm or less is preferred. More preferably, it is 0.01 Ω·cm or less. When using a sintered body with such a low bulk resistivity as a sputtering target, more stable DC sputtering can be performed. As a result, the film formation rate can be accelerated compared to conventional RF sputtering, thus improving productivity.

[0048] It should be noted that even if the volume resistivity exceeds the range mentioned above, it should be understood that as long as DC sputtering can be performed, it is included in this invention.

[0049] Furthermore, in the MgO-TiO sintered body of the present invention, there are two phases, TiO and MgO, and the region with the longest diameter of the MgO phase being 50 μm or more is preferably 10 or less per 1 mm. 2 More preferably, the number of regions with a longest diameter of 30 μm or more in the MgO phase is less than 25 per 1 mm. 2 Preferably, the TiO phase is dispersed in a mesh-like structure.

[0050] This invention relates to sintered bodies containing MgO and TiO with significantly different electrical conductivity. When a coarse MgO phase is present, abnormal discharges originating from it are prone to occur. By maximally reducing the region of such coarse MgO phase, abnormal discharges originating from the coarse MgO phase can be suppressed. It should be noted that the longest diameter of the MgO phase refers to the maximum length of the MgO phase particles forming on the polished surface of a sample taken from a portion of the target.

[0051] The MgO-TiO sintered body of the present invention can be prepared by the following method.

[0052] First, prepare MgO powder and TiO powder as raw materials. Preferably, use MgO powder with an average particle size of 10 μm or less and TiO powder with an average particle size of 50 μm or less. Particle sizes exceeding these ranges are difficult to mix uniformly, leading to segregation and coarsening of crystals, and are therefore not preferred. For the particle size of the raw material powders, finer particle sizes are preferable, but TiO is difficult to refine; from a production point of view, an average particle size of 1 μm or more is preferred.

[0053] Then, these raw material powders are weighed to obtain the specified molar ratio, and pulverized and mixed using known means such as a ball mill.

[0054] The resulting mixed powder is formed and sintered in a vacuum or inert gas atmosphere by hot pressing. In addition to hot pressing, various pressure sintering methods, such as spark plasma sintering, can also be used. In particular, hot isostatic pressing is effective in increasing the density of the sintered body. The holding temperature during sintering is preferably set to 1250–1450°C. Furthermore, the holding pressure during sintering is preferably set to 200 kgf / cm³. 2 The pressure range mentioned above.

[0055] Furthermore, in this invention, the sintered body obtained thereby is processed into a desired shape by grinding or the like, thereby enabling the fabrication of a sputtering target. The sputtering target manufactured in this way can perform DC sputtering, thus significantly increasing the film formation rate and greatly improving productivity. In addition, since the amount of powder particles generated during sputtering can be reduced, it has the excellent effect of improving the yield of the film during formation.

[0056] Example

[0057] The following description is based on embodiments and comparative examples. It should be noted that this embodiment is merely one example, and the present invention is not limited to this example in any way. That is, the present invention is limited only by the claims and includes various modifications other than those included in the embodiments.

[0058] (Example 1)

[0059] As raw material powders, MgO powder with an average particle size of 1 μm and a purity of 4N (99.99%) and TiO powder with an average particle size of 30 μm and a purity of 3N (99.9%) were prepared. Then, these raw material powders were blended to obtain the composition ratios shown in Table 1.

[0060] Then, the weighed powder and the pulverizing media zirconia balls are sealed in a 10-liter ball mill jar under an Ar atmosphere and mixed and pulverized for more than 20 hours to ensure that the two powders are evenly dispersed.

[0061] The powder removed from the container is then filled into a 180mm diameter graphite mold, and shaped and sintered using a hot press. The hot pressing conditions are: vacuum atmosphere, holding temperature 1400℃, and a pressure of 250 kgf / cm² from the start of heating to the end of holding. 2 The pressure is increased.

[0062] The density of the sintered body thus produced was determined using the Archimedes method, yielding a relative density of 98%. Here, relative density is the value obtained by dividing the measured density of the target by the calculated density (also known as theoretical density). Calculated density is the density assuming that the constituent components of the target do not diffuse or react with each other, expressed as: Calculated density = Σ(molecular weight of constituent component × molar ratio of constituent component) / Σ(molecular weight of constituent component × molar ratio of constituent component / theoretical density of constituent component). It should be noted that the theoretical density of MgO is 3.585 g / cm³. 3 The theoretical density of TiO is 4.93 g / cm³. 3 The same applies to the following examples and comparative examples.

[0063] Furthermore, the bulk resistivity of the sintered body was measured using the four-terminal method, and the result was 0.01 Ω·cm. Additionally, the cross-section of the sintered body was polished, and the central part was observed using a laser microscope. The results showed that both MgO and TiO phases were observed, with 5 MgO phases per mm having a maximum diameter of 50 μm or more and 5 MgO phases per mm having a maximum diameter of 30 μm or more. 2 15 pieces / mm 2 .

[0064] In addition, the sintered body was polished into a target shape using a grinding machine to create a disc-shaped target. This target was then mounted on a DC sputtering apparatus and sputtered. The sputtering conditions were set as follows: sputtering power: 0.5 kW, Ar gas pressure: 5 Pa, and film deposition on the silicon substrate for 30 seconds. Furthermore, the number of powder particles adhering to the substrate was measured using a particle counter. The number of powder particles at this point was 120.

[0065] Table 1

[0066]

[0067] (Example 2)

[0068] As raw material powders, MgO powder with an average particle size of 1 μm and a purity of 4N (99.99%) and TiO powder with an average particle size of 20 μm and a purity of 3N (99.9%) were prepared. Then, these raw material powders were blended to obtain the composition ratios shown in Table 1.

[0069] Then, the weighed powder and the pulverizing media zirconia balls are sealed in a 10-liter ball mill jar under an Ar atmosphere and mixed and pulverized for more than 20 hours to ensure that the two powders are evenly dispersed.

[0070] The powder removed from the container is then filled into a 180mm diameter graphite mold, and shaped and sintered using a hot press. The hot pressing conditions are: vacuum atmosphere, holding temperature 1400℃, and a pressure of 300 kgf / cm² from the start of heating to the end of holding. 2 The pressure is increased.

[0071] The density of the sintered body thus produced was determined using the Archimedes method, yielding a relative density of 98%. Furthermore, the volume resistivity of the sintered body was measured using the four-terminal method, resulting in a value of 0.003 Ω·cm. Additionally, the cross-section of the sintered body was polished, and the central portion was observed using a laser microscope. The results are shown below. Figure 1 .like Figure 1 As shown, two phases were observed: MgO (dark gray area) and TiO (light gray area). Furthermore, regions of the MgO phase with a longest diameter exceeding 50 μm and exceeding 30 μm are shown below. Figure 2 The images shown are 1 and 2 respectively. Convert this image area to 1 mm. 2 When the area is 3 / mm, they are respectively 2 5 pieces / mm 2 It should be noted that in other embodiments and comparative examples (excluding Comparative Example 1), when compared with... Figure 1 In tissue images at the same magnification, it was also confirmed that the tissue consisted of two phases: MgO and TiO. Figure 2In the image region at the same magnification, count the number of MgO phases with a longest diameter of 50 μm or more and 30 μm or more, and convert them to per 1 mm. 2 The area is used as the number of units per unit area.

[0072] In addition, the sintered body was polished into a target shape using a grinding machine to create a disc-shaped target. This target was then mounted on a DC sputtering apparatus and sputtered. The sputtering conditions were set as follows: sputtering power: 0.5 kW, Ar gas pressure: 5 Pa, and film deposition on the silicon substrate for 30 seconds. The number of powder particles adhering to the substrate was then measured using a particle counter. The number of powder particles at this point was 51.

[0073] (Example 3)

[0074] As raw material powders, MgO powder with an average particle size of 1 μm and a purity of 4N (99.99%) and TiO powder with an average particle size of 30 μm and a purity of 3N (99.9%) were prepared. Then, these raw material powders were blended to obtain the composition ratios shown in Table 1.

[0075] Then, the weighed powder and the pulverizing media zirconia balls are sealed in a 10-liter ball mill jar under an Ar atmosphere and mixed and pulverized for more than 20 hours to ensure that the two powders are evenly dispersed.

[0076] The powder removed from the container is then filled into a 180mm diameter graphite mold, and shaped and sintered using a hot press. The hot pressing conditions are: vacuum atmosphere, holding temperature 1400℃, and a pressure of 250 kgf / cm² from the start of heating to the end of holding. 2 The pressure is increased.

[0077] The density of the sintered body was determined using the Archimedes method, yielding a relative density of 99.5%. Furthermore, the volume resistivity of the sintered body was measured using the four-terminal method, resulting in a value of 0.002 Ω·cm. Additionally, the cross-section of the sintered body was polished, and the central portion was observed using a laser microscope. Both MgO and TiO phases were observed, with 0 MgO phases per mm having a maximum diameter of 50 μm or more, and 0 MgO phases per mm having a maximum diameter of 30 μm or more. 2 5 pieces / mm 2 .

[0078] In addition, the sintered body was polished into a target shape using a grinding machine to create a disc-shaped target. This target was then mounted on a DC sputtering apparatus and sputtered. The sputtering conditions were set as follows: sputtering power: 0.5 kW, Ar gas pressure: 5 Pa, and film deposition on the silicon substrate for 30 seconds. The number of powder particles adhering to the substrate was then measured using a particle counter. The number of powder particles at this point was 46.

[0079] (Example 4)

[0080] As raw material powders, MgO powder with an average particle size of 1 μm and a purity of 4N (99.99%) and TiO powder with an average particle size of 30 μm and a purity of 3N (99.9%) were prepared. Then, these raw material powders were blended to obtain the composition ratios shown in Table 1.

[0081] Then, the weighed powder and the pulverizing media zirconia balls were sealed in a 10-liter ball mill jar under an Ar atmosphere and rotated for 10 hours to mix and pulverize, so that the two powders were evenly dispersed.

[0082] The powder removed from the container is then filled into a 180mm diameter graphite mold, and shaped and sintered using a hot press. The hot pressing conditions are: vacuum atmosphere, holding temperature 1400℃, and a pressure of 250 kgf / cm² from the start of heating to the end of holding. 2 The pressure is increased.

[0083] The density of the sintered body was determined using the Archimedes method, yielding a relative density of 99.5%. Furthermore, the volume resistivity of the sintered body was measured using the four-terminal method, resulting in a value of 0.0005 Ω·cm. Additionally, the cross-section of the sintered body was polished, and the central portion was observed using a laser microscope. Both MgO and TiO phases were observed, with 0 MgO phases per mm having a maximum diameter of 50 μm or more, and 0 MgO phases per mm having a maximum diameter of 30 μm or more. 2 0 pieces / mm 2 .

[0084] In addition, the sintered body was polished into a target shape using a grinding machine to create a disc-shaped target. This target was then mounted on a DC sputtering apparatus and sputtered. The sputtering conditions were set as follows: sputtering power: 0.5 kW, Ar gas pressure: 5 Pa, and film deposition on the silicon substrate for 30 seconds. The number of powder particles adhering to the substrate was then measured using a particle counter. The number of powder particles at this point was 22.

[0085] (Comparative Example 1)

[0086] As raw material, only MgO powder with an average particle size of 1 μm and a purity of 4N (99.99%) was prepared. Then, the powder was sealed together with zirconia balls as grinding media in a 10-liter ball mill jar and ground for 10 hours.

[0087] The powder removed from the container is then filled into a 180mm diameter graphite mold, and shaped and sintered using a hot press. The hot pressing conditions are: vacuum atmosphere, holding temperature 1500℃, and a pressure of 300 kgf / cm² from the start of heating to the end of holding. 2 The pressure is increased.

[0088] The density of the sintered body produced in this way was determined using the Archimedes method, and the result showed a relative density of 99%. Additionally, the volume resistivity of the sintered body was measured using the four-terminal method, but the resistance value was too high to be measured.

[0089] The sintered body is machined into a target shape using a lathe to create a disc-shaped target. It is then mounted on a DC sputtering apparatus and sputtered, but DC sputtering is not permitted.

[0090] (Comparative Example 2)

[0091] As raw material powders, MgO powder with an average particle size of 1 μm and a purity of 4N (99.99%) and TiO powder with an average particle size of 25 μm and a purity of 3N (99.9%) were prepared. Then, these raw material powders were blended to obtain the composition ratios shown in Table 1.

[0092] Then, the weighed powder and the pulverizing media zirconia balls are sealed in a 10-liter ball mill jar under an Ar atmosphere and mixed and pulverized for more than 20 hours to ensure that the two powders are evenly dispersed.

[0093] The powder removed from the container is then filled into a 180mm diameter graphite mold, and shaped and sintered using a hot press. The hot pressing conditions are: vacuum atmosphere, holding temperature 1400℃, and a pressure of 300 kgf / cm² from the start of heating to the end of holding. 2 The pressure is increased.

[0094] The density of the sintered body produced was measured using the Archimedes method, yielding a relative density of 96%. However, the volume resistivity of the sintered body was not measured using the four-terminal method due to high resistance values. Furthermore, the cross-section of the sintered body was polished, and the central portion was observed using a laser microscope. This revealed both MgO and TiO phases, with 13 MgO phases per mm having a maximum diameter of 50 μm or more and 13 MgO phases per mm having a maximum diameter of 30 μm or more. 2 35 pieces / mm 2 .

[0095] The sintered body is polished into a target shape using a grinding machine to create a disc-shaped target. This target is then mounted on a DC sputtering apparatus and sputtered, but DC sputtering cannot be performed.

[0096] (Comparative Example 3)

[0097] As raw material powders, MgO powder with an average particle size of 1 μm and a purity of 4N (99.99%) and TiO powder with an average particle size of 100 μm and a purity of 3N (99.9%) were prepared. Then, these raw material powders were blended to obtain the composition ratios shown in Table 1.

[0098] Then, the weighed powder and the pulverizing media zirconia balls were sealed in a 10-liter ball mill jar under an Ar atmosphere and mixed and pulverized for 5 hours to ensure that the two powders were evenly dispersed.

[0099] The powder removed from the container is then filled into a 180mm diameter graphite mold, and shaped and sintered using a hot press. The hot pressing conditions are: vacuum atmosphere, holding temperature 1400℃, and a pressure of 300 kgf / cm² from the start of heating to the end of holding. 2 The pressure is increased.

[0100] The density of the sintered body was measured using the Archimedes method, yielding a relative density of 97%. Furthermore, the volume resistivity of the sintered body was measured using the four-terminal method, resulting in a value of 0.007 Ω·cm. Additionally, the cross-section of the sintered body was polished, and the central portion was observed using a laser microscope. This revealed both MgO and TiO phases, with 25 MgO phases per mm having a maximum diameter of 50 μm or more and 25 MgO phases per mm having a maximum diameter of 30 μm or more. 2 53 pieces / mm 2 .

[0101] In addition, the sintered body was polished into a target shape using a grinding machine to create a disc-shaped target. This target was then mounted on a DC sputtering apparatus and sputtered. The sputtering conditions were set as follows: sputtering power: 0.5 kW, Ar gas pressure: 5 Pa, and film deposition on the silicon substrate for 30 seconds. The number of powder particles adhering to the substrate was then measured using a particle counter. The particle count was 2000.

[0102] (Comparative Example 4)

[0103] As raw material powders, MgO powder with an average particle size of 1 μm and a purity of 4N (99.99%) and TiO powder with an average particle size of 100 μm and a purity of 3N (99.9%) were prepared. Then, these raw material powders were blended to obtain the composition ratios shown in Table 1.

[0104] Then, the weighed powder and the pulverizing media zirconia balls were sealed in a 10-liter ball mill jar under an Ar atmosphere and mixed and pulverized for 5 hours to ensure that the two powders were evenly dispersed.

[0105] The powder removed from the container is then filled into a 180mm diameter graphite mold, and shaped and sintered using a hot press. The hot pressing conditions are: vacuum atmosphere, holding temperature 1400℃, and a pressure of 300 kgf / cm² from the start of heating to the end of holding. 2 The pressure is increased.

[0106] The density of the sintered body was determined using the Archimedes method, yielding a relative density of 99.5%. Furthermore, the volume resistivity of the sintered body was measured using the four-terminal method, resulting in a value of 0.002 Ω·cm. Additionally, the cross-section of the sintered body was polished and observed using a laser microscope, revealing both MgO and TiO phases. The MgO phase exhibited 15 regions per mm with a maximum diameter of 50 μm or more and 15 regions per mm with a maximum diameter of 30 μm or more. 2 41 pieces / mm 2 .

[0107] In addition, the sintered body was polished into a target shape using a grinding machine to create a disc-shaped target. This target was then mounted on a DC sputtering apparatus and sputtered. The sputtering conditions were set as follows: sputtering power: 0.5 kW, Ar gas pressure: 5 Pa, and film deposition on the silicon substrate for 30 seconds. The number of powder particles adhering to the substrate was then measured using a particle counter. The number of powder particles at this point was 500.

[0108] Industrial practicality

[0109] The MgO-TiO sintered body of the present invention can be DC sputtered, thus significantly increasing the film formation rate compared to conventional RF sputtering of MgO sintered bodies, resulting in a significant improvement in productivity. Furthermore, since DC sputtering can be achieved using inexpensive DC power supplies, existing equipment can be directly utilized, reducing equipment investment costs.

[0110] As can be seen from the above, the MgO-TiO sintered body of the present invention is useful as a magnesium oxide-based sputtering target for forming thin films for electronic devices such as magnetic recording media for disk drives and tunnel magnetoresistance (TMR) elements. Furthermore, as a conductive ceramic material that conventional insulating MgO cannot achieve, it can also be used in new fields such as static electricity elimination and heat-resistant components.

Claims

1. A MgO-TiO sintered sputtering target, which is a sintered sputtering target for DC sputtering, contains 25-90 mol% TiO, with the remainder being MgO and unavoidable impurities, and contains two phases, TiO and MgO, wherein the MgO phase has fewer than 10 regions with a longest diameter of 50 μm or more per mm. 2 Furthermore, the number of regions with a longest diameter of 30 μm or more in this MgO phase is less than 25 per 1 mm. 2 The TiO phase is dispersed in a mesh-like manner.

2. The MgO-TiO sintered sputtering target as described in claim 1, characterized in that, The TiO content is 50–90 mol.

3. The MgO-TiO sintered sputtering target as described in claim 1, characterized in that, The TiO content is 70–90 mol.

4. The MgO-TiO sintered sputtering target according to any one of claims 1 to 3, characterized in that, The relative density is over 95%.

5. The MgO-TiO sintered sputtering target according to any one of claims 1 to 3, characterized in that, The volume resistivity is below 10 Ω·cm.

6. The MgO-TiO sintered sputtering target according to any one of claims 1 to 3, characterized in that, The volume resistivity is below 0.01 Ω·cm.

7. The MgO-TiO sintered sputtering target as described in claim 1, characterized in that, Two phases, TiO and MgO, exist, and the number of regions with a longest diameter of 50 μm or more in the MgO phase is less than 5 per 1 mm. 2 .

8. The MgO-TiO sintered sputtering target as described in claim 1, characterized in that, Two phases, TiO and MgO, exist, and the number of regions with a longest diameter of 30 μm or more in the MgO phase is less than 15 per 1 mm. 2 .

9. A method for manufacturing a MgO-TiO sintered body sputtering target, wherein the MgO-TiO sintered body sputtering target is the MgO-TiO sintered body sputtering target as described in claim 1, and the manufacturing method is a method for manufacturing a sintered body sputtering target for DC sputtering containing 10 mol% or more and 90 mol% or less TiO in MgO, characterized in that... A raw material powder comprising MgO powder with an average particle size of less than 10 μm and TiO powder with an average particle size of less than 50 μm is mixed, and the mixed raw material powder is subjected to a temperature of 1250–1450 °C and a pressure of 200 kgf / cm³. 2 The MgO-TiO sintered body is produced by hot pressing under the above pressure.

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