Cr-Si sintered body

Abstract

To provide a Cr-Si sintered body made from chromium silicide (CrSi2) and silicon (Si) to have high strength.SOLUTION: Provided is a Cr-Si sintered body including chromium (Cr) and silicon (Si), the Cr-Si sintered body being characterized in that the crystal structure assigned by x-ray diffraction is configured from chromium silicide (CrSi2) and silicon (Si), a CrSi2 phase is present at 60 wt.% or higher in bulk, the sintered body density is 95% or higher, and the average grain size of the CrSi2 phase is 60 μm or lower.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a Cr-Si-based sintered body for thin film formation.

Background Art

[0002] In recent years, silicides such as CrSi2 have been used as thin films in many places such as semiconductors and solar cells due to their characteristics. Industrially, the sputtering method is often adopted for the production of thin films. However, a composition containing a silicide such as CrSi2 generally has low strength and there is a phenomenon of cracking during the processing of the sputtering target and during the discharge of film formation, and it is known to be difficult to use as a sputtering target. Therefore, in Patent Document 1, a sputtering target of a crystalline phase of Cr and Si is produced by the spraying method. However, in the spraying method, the strength is not sufficiently increased where the distribution of Cr is small, and the sputtering target produced by the spraying method using a powder of a silicide phase has not been strengthened.

[0003] Also, in Patent Document 2, a composition having a fine eutectic structure is produced by the melting method. However, in the melting method, the ratio of the eutectic structure is small, and high strength cannot be achieved in a composition in which a large amount of primary crystals are present. Furthermore, when the size is increased, it becomes difficult to control the crystal structure due to the difference in the cooling rate, and the unevenness of strength becomes large.

[0004] Furthermore, in Patent Documents 3 and 4, since the silicide phase is brittle, there is no mention of a system containing a large amount of silicide.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

[0006] The object of the present invention is to provide a high-strength Cr-Si sintered body containing Cr (chromium) and silicon (Si). [Means for solving the problem]

[0007] The inventors of the present invention have diligently investigated the manufacturing process for Cr-Si sintered bodies composed of chromium silicide (CrSi2) and silicon (Si) in stoichiometric composition, and having a specific amount or more of the CrSi2 phase. As a result, they have discovered that high-strength Cr-Si sintered bodies can be obtained by using rapidly cooled alloy powders such as gas atomized powder, and have completed the present invention.

[0008] In other words, embodiments of the present invention are as follows. (1) A Cr-Si sintered body containing Cr (chromium) and silicon (Si), characterized in that the crystal structure assigned by X-ray diffraction consists of chromium silicide (CrSi2) and silicon (Si), the CrSi2 phase is present in a bulk amount of 60 wt% or more, the sintered body density is 95% or more, and the average particle size of the CrSi2 phase is 60 μm or less. (2) The Cr-Si sintered body according to (1), characterized in that it has a flexural strength of 100 MPa or more. (3) The Cr-Si sintered body according to (1) or (2), characterized in that the amount of oxygen in the bulk is 1 wt% or less. (4) A sputtering target characterized by being made of a Cr-Si sintered body as described in any of (1) to (3). A method for manufacturing a thin film, characterized by sputtering using the sputtering target described in (5)(4).

[0009] The present invention will be described in detail below.

[0010] The present invention is a Cr-Si sintered body containing Cr (chromium) and silicon (Si), characterized in that the crystal structure assigned by X-ray diffraction consists of chromium silicide (CrSi2) and silicon (Si), the CrSi2 phase is present in a bulk amount of 60 wt% or more, the sintered body density is 95% or more, and the average particle size of the CrSi2 phase is 60 μm or less.

[0011] The crystalline phase of the Cr-Si sintered body of the present invention is characterized by being composed of a chromium silicide (CrSi2) phase and a silicon (Si) phase as determined by XRD. If the silicification reaction does not proceed sufficiently and other silicide phases (Cr3Si, Cr5Si3, CrSi) or chromium (Cr) phases that should not normally be present in the composition are locally present, microcracks will be inherent due to density differences, making the sintered body prone to cracking, especially in large bodies, and preventing the production of sintered bodies with good yield. Furthermore, if high power is applied to such a sintered body during sputtering, cracks are likely to occur during discharge, which reduces the productivity of the film deposition process and is therefore undesirable.

[0012] The Cr-Si-based sintered body of the present invention is characterized by the presence of 60 wt% or more of CrSi2 phase in the bulk. Preferably, it is 70 wt% or more, and particularly preferably 80 wt% or more.

[0013] The sintered body density of the Cr-Si-based sintered body of the present invention is characterized by a relative density of 95% or higher. If the sintered body density is lower than 95%, the strength decreases. Furthermore, since the frequency of arcing increases when used as a sputtering target, the density is preferably 97% or higher, and more preferably 98% or higher.

[0014] Furthermore, the particle size of the chromium silicide in the Cr-Si sintered body of the present invention is 60 μm or less. When the particle size exceeds 60 μm, the strength decreases rapidly. To obtain stable high strength, the particle size is preferably 1 to 60 μm, more preferably 1 to 20 μm, and particularly preferably 1 to 10 μm.

[0015] The amount of oxygen in the bulk of the Cr-Si sintered body of the present invention is preferably 1 wt% or less, more preferably 0.5 wt% or less, more preferably 0.1 wt% or less, and even more preferably 0.05 wt% or less, from the viewpoint of particle generation when formed into a film and the yield of film-backed products.

[0016] The flexural strength of the Cr-Si sintered body of the present invention is preferably 100 MPa or higher, more preferably 100 to 500 MPa, even more preferably 150 to 500 MPa, and particularly preferably 200 to 500 MPa. Higher strength of the sintered body reduces the likelihood of cracking during grinding and bonding processes, resulting in higher yield and better productivity. Furthermore, cracking is less likely to occur even when high power is applied during sputtering.

[0017] The Cr-Si sintered body of the present invention may contain 1 wt% or less in total amount of unavoidable metal impurities other than Cr (chromium) and silicon (Si), preferably 0.5 wt% or less, more preferably 0.05 wt%, and even more preferably 0.01 wt% or less.

[0018] In addition to chromium (Cr) and silicon (Si), unavoidable metal impurities such as Fe, Ni, Al, Mn, and Cu may be present in a total amount of 1 wt% or less, preferably 0.5 wt% or less, more preferably 0.05 wt%, and even more preferably 0.01 wt% or less.

[0019] As individual elements, Fe may be contained at 0.1 wt% or less, preferably 0.05 wt% or less, more preferably 0.01 wt% or less. Ni may be contained at 0.01 wt% or less, preferably 0.005 wt% or less, more preferably 0.001 wt% or less. Al may be contained at 0.1 wt% or less, preferably 0.05 wt% or less, more preferably 0.01 wt% or less. Mn may be contained at 0.005 wt% or less, preferably 0.001 wt% or less, more preferably 0.005 wt% or less. Cu may be contained at 0.01 wt% or less, preferably 0.005 wt% or less, more preferably 0.001 wt% or less.

[0020] Next, the manufacturing method of the Cr—Si sintered body of the present invention will be described.

[0021] The manufacturing method of the Cr—Si sintered body of the present invention can be manufactured by a process including: (1) an alloy raw material preparation step using chromium and silicon by a gas atomization method, an arc melting method, etc.; and (2) a firing step of firing the obtained raw material powder at a pressure of 50 MPa or less and a firing temperature of 1100°C to 1300°C using a pressure firing furnace such as a hot press furnace.

[0022] Hereinafter, the manufacturing method of the Cr—Si sintered body of the present invention will be described for each step.

[0023] (1) Alloy raw material preparation step Chromium and silicon are used as raw materials. The purity of the raw materials is preferably 99.9% or more, more preferably 99.99% or more. If a large amount of impurities is contained, it will cause abnormal grain growth in the firing step and be a source of particles during film formation. Also, it is preferable that the amount of oxygen in the raw materials is small. If the amount of oxygen in the raw materials is large, the amount of oxygen in the sputtering target will finally increase, which will cause the generation of particles.

[0024] The synthetic raw material powder can be manufactured by a gas atomization method or an arc melting method.

[0025] It is preferable to rapidly cool the alloy raw material powder by gas atomization or other methods to produce a powder with a fine structure. In particular, particles produced by gas atomization become spherical, approximately several tens of micrometers in size, and the powder contains fine CrSi2 phase and Si phase within the sphere. Due to the small surface area and fine grain size, the sintered body after firing can be made low in oxygen and high in strength. High-strength bulk can also be produced by mixing fine powder, but the oxygen content will be high. Conversely, mixing coarse grains can reduce oxygen levels, but the strength will be lower. Other raw material preparation methods include rapid cooling methods such as quenching thin strips and arc melting.

[0026] The conditions for the gas atomization method are preferably set to a melting temperature of +50 to 300°C. More preferably, it is set to +100 to 250°C. Here, the melting temperature is the temperature at which the raw material powder melts, and is usually 1300 to 1500°C. If the difference from the melting temperature is small, the phase with the higher melting point of the two crystalline phases precipitates first, making particle refinement difficult. On the other hand, if the difference from the melting temperature is large, the particles sinter together after atomization and adhere to the wall surface, resulting in poor powder recovery.

[0027] Furthermore, it is preferable to manage the powder after gas atomization in a vacuum or in an inert atmosphere such as nitrogen or argon. If the powder is left in the atmosphere, oxidation will occur from the surface, increasing the amount of oxygen in the powder.

[0028] The arc power is crucial for arc melting. It determines whether materials with large melting point differences can be alloyed. For example, in the case of chromium and silicon, the melting point of chromium is 1863°C and the melting point of silicon is 1414°C, so the arc power needs to be 50-200A for melting. If the arc current is too high, the amount of chromium sublimation increases, so the arc melting power is preferably in the range of 50-150A.

[0029] (2) Firing process Next, it is preferable to use a pressurized furnace such as a hot press furnace to process the resulting powder. In a non-pressurized furnace, it is difficult to increase the density due to the low diffusion coefficient of silicon.

[0030] The hot press pressure during firing is preferably 50 MPa or less. If it exceeds 50 MPa, it becomes difficult to prepare a hot press mold that can withstand the pressure. When producing large sintered bodies, the hot press pressure is preferably 5 to 50 MPa, more preferably 5 to 20 MPa, and particularly preferably 5 to 10 MPa.

[0031] The firing temperature should be between 1100°C and 1300°C. Below 1100°C, the density will not increase sufficiently, and above 1300°C, there is a possibility of melting depending on the pressure of the hot press. Furthermore, the cooling rate is not particularly limited and can be determined as appropriate considering the capacity of the sintering furnace, the size and shape of the sintered body, its tendency to crack, etc.

[0032] The holding time during firing should be between 1 and 5 hours. If the holding time is shorter than 1 hour, temperature unevenness will occur inside the furnace and the hot press mold, making it difficult to obtain a uniform structure. Conversely, if the holding time is too long, productivity will decrease.

[0033] There are no particular restrictions on the atmosphere during firing, but a vacuum or an inert atmosphere such as argon is preferred.

[0034] The Cr-Si sintered body of the present invention can be ground into a plate shape using machining equipment such as a surface grinder, cylindrical grinder, lathe, cutting machine, and machining center.

[0035] The Cr-Si sintered body of the present invention can be used as a sputtering target. As a method for manufacturing the sputtering target, a sputtering target can be obtained by bonding the Cr-Si sintered body to a backing plate and backing tube made of oxygen-free copper or titanium, etc., using indium solder or the like, as needed.

[0036] Furthermore, thin films can also be manufactured by sputtering using the obtained sputtering target. [Effects of the Invention]

[0037] The Cr-Si sintered body of the present invention has high strength, and when used as a sputtering target, it does not crack even under high power, enabling high productivity. Furthermore, because it has a low oxygen content, it is possible to reduce particle size during film formation. [Brief explanation of the drawing]

[0038] [Figure 1] X-ray analysis diagrams of Example 1 and Comparative Example 3 [Examples]

[0039] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. The measurements in these examples were performed as follows. (1) Density of the sintered body The relative density of the sintered body was determined by the Archimedes method in accordance with JIS R 1634. The degree was measured and the relative density was determined by dividing it by the true density. The true density of the sintered body is the weight of the CrSi2 phase. Let a[g] be the weight of the Si phase and b[g] be the weight of the Si phase, and their respective true densities be 4.98[g / cm³]. 3 ], 2.3 [g / cm³] 3 It was calculated using the arithmetic mean expressed by the following formula. d = (a + b) / ((a / 4.98) + (b / 2.3) (2) X-ray diffraction test The X-ray diffraction patterns of mirror-polished sintered body samples were measured in the range of 2θ = 20 to 70°.

[0040] Scanning method: Step scan method (FT method) X-ray source:CuKα Power: 40kV, 40mA Step width: 0.01° (3) Sintered body grain size The sintered body was polished to a mirror finish, observed with a scanning electron microscope, and the particle size of the sintered body was measured using the diameter method from the resulting sintered body microstructure image. At least three arbitrary points were observed, and more than 300 particles were measured. (Observation conditions for scanning electron microscope) Acceleration voltage: 10kV (4) Transverse bending strength Measurements were taken in accordance with JIS R 1601. (Measurement conditions for bending strength) Test method: 3-point bending test Distance between fulcrums: 30mm Sample size: 3 x 4 x 40 mm Head speed: 0.5 mm / min. (5) Analysis of oxygen levels The analytical data was obtained from samples cut from any part of the sintered body after grinding the surface by at least 1 mm following firing.

[0041] Measurement method: Impulse furnace melting - infrared absorption spectroscopy Equipment: LECO TC436 Oxygen / Nitrogen Analyzer (6) Analysis of metal impurity content The analytical data was obtained from samples cut from any part of the sintered body after grinding the surface by at least 1 mm following firing.

[0042] Measurement method: Glow discharge mass spectrometry (GDMS) (Example 1) Cr flakes (4N): 42 wt% and Si flakes (5N): 58 wt% were melted in a carbon crucible, and powder was prepared by gas atomization at a melting temperature of 1650°C. The powder was then sieved under air (sieve size: 300 μm) to adjust its particle size.

[0043] Next, this powder was placed in a carbon mold (53 mmΦ) and fired using a hot press method to obtain a sintered body. (Firing conditions) Firing furnace: Hot press furnace Heating rate: 200°C / hour Heating atmosphere: Vacuum / Depressurized atmosphere Firing temperature: 1250℃ Pressure: 10 MPa Baking time: 3 hours A sintered body with a size of 53 mmΦ × 7 mmt and no microcracks was obtained. The properties of the sintered body are shown in Table 1.

[0044] (Examples 2-5) A sintered body was prepared using the same method as in Example 1, except that the firing conditions were changed. The sintered body properties are shown in Table 1.

[0045] (Example 6) Cr flakes (4N): 29 wt% and Si flakes (5N): 71 wt% were melted by arc melting at an output of 100 A. The resulting bulk was crushed in a mortar and pestle and fired under the conditions of Example 3. The properties of the sintered body are shown in Table 1.

[0046] (Example 7) 42 wt% Cr flakes (4N) and 58 wt% Si flakes (5N) were melted in a carbon crucible, and powder was prepared by gas atomization at a melting temperature of 1650°C. The powder was then sieved (sieve size: 300 μm) in a glove box (oxygen concentration: 0.1 wt% or less) to adjust the particle size.

[0047] Next, this powder was placed in a carbon mold (53 mmΦ) and fired using a hot press method to obtain a sintered body. (Firing conditions) Firing furnace: Hot press furnace Heating rate: 200°C / hour Heating atmosphere: Vacuum / Depressurized atmosphere Firing temperature: 1200℃ Pressure: 20 MPa Baking time: 3 hours A sintered body with a size of 53 mmΦ × 7 mmt and no microcracks was obtained. The properties of the sintered body are shown in Table 1.

[0048] Furthermore, GDMS analysis revealed that the total amount of metal impurities other than Cr and Si was 0.034 wt% or less, with individual impurity amounts being 0.0066 wt% for Fe, 0.00082 wt% for Ni, 0.000048 wt% for Al, 0.00011 wt% for Mn, and 0.000051 wt% for Cu. (Example 8) Cr flakes (4N): 29 wt% and Si flakes (5N): 71 wt% were melted in a carbon crucible, and powder was prepared by gas atomization at a melting temperature of 1540°C. The powder was then sieved (sieve size: 300 μm) in a glove box (oxygen concentration: 0.1 wt% or less) to adjust the particle size.

[0049] Next, this powder was placed in a carbon mold (53 mmΦ) and fired using a hot press method to obtain a sintered body. (Firing conditions) Firing furnace: Hot press furnace Heating rate: 200°C / hour Heating atmosphere: Vacuum / Depressurized atmosphere Firing temperature: 1200℃ Pressure: 20 MPa Baking time: 3 hours A sintered body with a size of 53 mmΦ × 7 mmt and no microcracks was obtained. The properties of the sintered body are shown in Table 1. Furthermore, the amount of metal impurities was analyzed by GDMS, and the total amount of metal impurities other than Cr and Si was 0.026 wt% or less, with the individual impurity amounts being 0.0027 wt% for Fe, 0.00039 wt% for Ni, 0.000022 wt% for Al, 0.000041 wt% for Mn, and 0.000012 wt% for Cu. (Example 9) A sintered body was prepared using the same method as in Example 8, except that the firing conditions were changed. The sintered body properties are shown in Table 1. (Example 10) 47 wt% Cr flakes (4N) and 53 wt% Si flakes (5N) were melted in a carbon crucible, and powder was prepared by gas atomization at a melting temperature of 1540°C. The powder was then sieved (sieve size: 300 μm) in a glove box (oxygen concentration: 0.1 wt% or less) to adjust the particle size.

[0050] Next, this powder was placed in a carbon mold (53 mmΦ) and fired using a hot press method to obtain a sintered body. (Firing conditions) Firing furnace: Hot press furnace Heating rate: 200°C / hour Heating atmosphere: Vacuum / Depressurized atmosphere Firing temperature: 1200℃ Pressure: 20 MPa Baking time: 3 hours A sintered body with a size of 53 mmΦ × 7 mmt and no microcracks was obtained. The properties of the sintered body are shown in Table 1. Furthermore, the amount of metal impurities was analyzed by GDMS, and the total amount of metal impurities other than Cr and Si was 0.03 wt% or less, with the individual impurity amounts being 0.0062 wt% for Fe, 0.00078 wt% for Ni, 0.000035 wt% for Al, 0.000068 wt% for Mn, and 0.000041 wt% for Cu.

[0051] (Example 11) A sintered body was prepared in the same manner as in Example 10, except that the firing conditions were changed. The sintered body properties are shown in Table 1. (Comparative Example 1) Cr flakes (4N): 42 wt% and Si flakes (5N): 58 wt% were melted by arc melting. The properties of the bulk obtained after melting are shown in Table 1. (Comparative Example 2) The bulk material prepared in Comparative Example 1 was crushed in a mortar and pestle and then processed by the hot press method. The sintered body characteristics are shown in Table 1. (Comparative Example 3) Cr powder (45 μm) and Si powder (9 μm) were mixed using a V-type mixing method, and the mixed powder was hot-pressed to produce a sintered body. The properties of the sintered body are shown in Table 1. (Comparative Example 4) Powders prepared by gas atomization were fired under modified firing conditions. The sintered body characteristics are shown in Table 1. (Comparative Example 5) Cr flakes (4N): 29 wt% and Si flakes (5N): 71 wt% were melted by arc melting. The properties of the bulk obtained after melting are shown in Table 1.

[0052] [Table 1]

Claims

1. The Cr-Si sintered body, containing Cr (chromium) and silicon (Si), comprises an alloy raw material preparation step of obtaining raw material powder by gas atomization using chromium and silicon, and a sintering step of hot pressing the raw material powder at a pressure of 50 MPa or less and a sintering temperature of 1100°C to 1300°C, wherein the crystal structure assigned by X-ray diffraction is chromium silicide (CrSi ２ ), composed of silicon (Si), CrSi ２ A method for producing a Cr-Si sintered body, characterized in that the phase is present in the bulk at a concentration of 60 wt% or more, the sintered body density is 95% or more, and the average particle size of the Cr-Si sintered body is 60 μm or less.

2. The method for producing a Cr-Si sintered body according to claim 1, characterized in that the firing time in the firing step is within 1 to 5 hours.

3. The method for producing a Cr-Si sintered body according to claim 1 or 2, characterized in that the atmosphere during firing is an inert atmosphere in the firing step.

4. The method for producing a Cr-Si sintered body according to claim 1 or 2, characterized in that the purity of chromium and silicon in the alloy raw material preparation step is 99.9% or higher.

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