METHOD FOR PRODUCING Cr-Si-BASED SINTERED BODY

Abstract

To provide a method for producing a Cr-Si-based sintered body having high mechanical strength.SOLUTION: A method for producing a Cr-Si-based sintered body comprises the steps of: preparing alloy powder from pure chromium and pure silicon by a gas atomization method; and obtaining a Cr-Si-based sintered body by sintering the alloy powder at 1100-1400°C under a pressure of 50 MPa or less. The sintered body includes a crystalline CrSi2 phase and a crystalline Si phase. The content of the Si phase in the sintered body is 40 mass% or more. The relative density of the sintered body to the true density of the sintered body is 95% or more. The average crystal grain size in the CrSi2 phase is 40 μm or less and the average crystal grain size in the Si phase is 30 μm or less. The total content of the impurities in the sintered body is 200 mass ppm or less, where the impurities include at least one selected from the group consisting of Mn, Fe, Mg, Ca, Sr, and Ba.SELECTED DRAWING: None

Description

[Technical field]

[0001] One aspect of the present invention relates to a Cr-Si based sintered body used for forming a thin film, a sputtering target, and a method for producing a thin film. [Background technology]

[0002] In recent years, silicides such as CrSi2 have been used as thin films in many technical fields, such as semiconductors, solar cells, automotive sensors, and home appliance sensors, because they have a high resistivity (unit: Ω·cm) that does not change easily with temperature changes. Sputtering methods are often used in the industrial production of thin films. However, compositions containing silicides generally have low mechanical strength, so that sputtering targets containing silicides are prone to cracking during discharge during processing and film formation of the sputtering target. Therefore, conventional compositions containing silicides are difficult to use as sputtering targets. The following Patent Document 1 discloses a method for producing a sputtering target containing crystalline phases of chromium (Cr) and silicon (Si) by a thermal spraying method in order to improve the mechanical strength of the sputtering target. However, in the sputtering target produced by the thermal spraying method, the mechanical strength is not sufficiently increased in the areas where the Cr content is low. In addition, in the method described in Patent Document 1, the sputtering target is produced by a thermal spraying method using silicide powder, so the mechanical strength of the sputtering target is not sufficiently increased.

[0003] The following Patent Document 2 discloses a method for producing a composition having a fine eutectic structure containing Si and silicide by a melting method. However, in a composition produced by the melting method, the proportion of the eutectic structure is low and a large amount of primary crystals is present, so the mechanical strength of the composition is not sufficiently increased. When such a composition is made large, it becomes difficult to control the crystal structure due to differences in the cooling rate within the composition, and the mechanical strength of the composition becomes uneven.

[0004] The following Patent Documents 3 and 4 also disclose sputtering targets containing silicide. However, Patent Document 3 does not disclose the content of impurities in the sputtering target. Patent Document 4 discloses the respective contents of oxygen and carbon in the sputtering target. Patent Document 4 also discloses a process of mechanically pulverizing silicide powder in the manufacturing process of the sputtering target. However, Patent Document 4 does not disclose the content of metal impurities that deteriorate the semiconductor film characteristics. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-82314 [Patent Document 2] Japan Special Publication No. 2013-502368 [Patent Document 3] Japanese Patent Publication No. 2002-173765 [Patent Document 4] Japanese Patent Publication No. 2003-167324 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of one aspect of the present invention is to provide a Cr-Si-based sintered body containing Cr and Si and having high mechanical strength, a sputtering target including the sintered body, and a method for producing a thin film using the sputtering target. [Means for solving the problem]

[0007] The present inventors have conducted extensive research into a manufacturing process for a Cr-Si sintered body that is composed of a chromium silicide (CrSi2) phase and a Si phase in a stoichiometric composition and contains a specific amount or more of the Si phase. As a result, the present inventors have found that a Cr-Si sintered body having high mechanical strength can be obtained by using a rapidly cooled alloy powder such as a gas atomized powder, and have completed the present invention.

[0008] That is, a Cr-Si sintered body, a sputtering target, and a method for producing a thin film according to one aspect of the present invention are as follows. (1) A Cr-Si-based sintered body containing chromium (Cr) and silicon (Si), characterized in that the crystal structure determined by X-ray diffraction is composed of chromium silicide (CrSi2) and silicon (Si), the Si phase is present in the bulk at 40 mass% or more, the sintered body density is 95% or more, the average grain size of the CrSi2 phase is 40 μm or less, the average grain size of the Si phase is 30 μm or less, and the total impurity amount of Mn+Fe+Mg+Ca+Sr+Ba is 200 ppm or less. That is, a Cr-Si sintered material according to one aspect of the present invention is a Cr-Si sintered material containing Cr and Si, the Cr-Si sintered material containing a crystalline CrSi2 phase and a crystalline Si phase, the content of the Si phase in the Cr-Si sintered material is 40 mass% or more, the relative density of the Cr-Si sintered material with respect to the true density of the Cr-Si sintered material is 95% or more, the average crystal grain size of the CrSi2 phase is 40 μm or less, the average crystal grain size of the Si phase is 30 μm or less, the total content of impurities in the Cr-Si sintered material is 200 mass ppm or less, and the impurities are at least one element selected from the group consisting of manganese (Mn), iron (Fe), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). (2) The Cr-Si sintered body according to (1), characterized in that the flexural strength is 100 MPa or more. In other words, the flexural strength of the Cr-Si sintered body according to one aspect of the present invention may be 100 MPa or more. (3) A Cr-Si sintered body according to either (1) or (2), characterized in that the amount of oxygen in the bulk is 1 mass % or less. That is, the oxygen content in the Cr-Si sintered body according to one aspect of the present invention may be 1 mass % or less. (4) A sputtering target comprising the Cr-Si sintered body according to any one of (1) to (3). That is, a sputtering target according to one aspect of the present invention contains the above-mentioned Cr-Si sintered body. (5) A method for producing a thin film, comprising sputtering using the sputtering target according to (4). That is, a method for producing a thin film according to one aspect of the present invention includes a step of forming a thin film by sputtering using the above-mentioned sputtering target. Effect of the Invention

[0009] According to one aspect of the present invention, there are provided a Cr-Si-based sintered body containing Cr and Si and having high mechanical strength, a sputtering target containing the sintered body, and a method for producing a thin film using the sputtering target. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In the following, preferred embodiments of the present invention will be described. The present invention is not limited to the following embodiments. The "mass%" described below may be rephrased as "weight% (wt%)." The Cr-Si sintered body described below may be rephrased as "bulk."

[0011] The Cr-Si sintered body according to the present embodiment contains Cr and Si. The Cr-Si sintered body contains a crystalline CrSi2 phase and a crystalline Si phase. The content of the Si phase in the Cr-Si sintered body is 40 mass% or more. The relative density of the Cr-Si sintered body with respect to the true density of the Cr-Si sintered body is 95% or more. The average crystal grain size of the CrSi2 phase is 40 μm or less, and the average crystal grain size of the Si phase is 30 μm or less. The total content of impurities in the Cr-Si sintered body is 200 mass ppm or less, and the impurities are at least one element selected from the group consisting of Mn, Fe, Mg, Ca, Sr, and Ba. The sputtering target according to this embodiment contains the above-mentioned Cr-Si sintered body. A method for producing a thin film according to one aspect of the present invention includes a step of forming a thin film by sputtering using the above-described sputtering target. Since the Cr-Si sintered body according to the present embodiment has excellent mechanical strength, the sputtering target according to the present embodiment is unlikely to crack during high-output sputtering, and therefore the method for producing a thin film by sputtering using the sputtering target according to the present embodiment can achieve high productivity. The details of this embodiment are as follows.

[0012] The CrSi2 phase, the Si phase, and their crystal structures in the Cr-Si sintered body may be detected and identified by an X-ray diffraction (XRD) method. The crystal structure of the CrSi2 phase belongs to a hexagonal crystal system. The crystal structure of the Si phase (diamond structure) belongs to a cubic crystal system. The CrSi2 phase and the Si phase may be mixed in the Cr-Si sintered body. The CrSi2 phase may include one or more crystal grains made of CrSi2. The Si phase may include one or more crystal grains made of Si. The Cr-Si sintered body may consist of only the CrSi2 phase and the Si phase. When the Cr-Si sintered body consists of only the CrSi2 phase and the Si phase, the Cr-Si sintered body is likely to have high mechanical strength. In the case where the silicidation reaction of Cr in the Cr-Si sintered body does not proceed sufficiently and other silicide phases (Cr3Si, Cr5Si3, CrSi, etc.) and / or chromium (Cr) phases that should not exist in the stoichiometric ratio are locally present in the Cr-Si sintered body, microcracks due to density differences in the Cr-Si sintered body are present in the Cr-Si sintered body, and especially large Cr-Si sintered bodies are easily cracked, making it difficult to manufacture such Cr-Si sintered bodies at a high yield rate. In addition, when high power is supplied to a sputtering target made of a Cr-Si sintered body containing other silicide phases and / or chromium phases, the Cr-Si sintered body is easily cracked during discharge, reducing the productivity of the film formation process. However, as long as the Cr-Si-based sintered body has sufficiently high mechanical strength and cracking of the sputtering target during sputtering is sufficiently suppressed, the Cr-Si-based sintered body may contain, in addition to the CrSi2 phase and the Si phase, at least one of a small amount of other silicide phase and a small amount of chromium phase.

[0013] The content of the Si phase in the Cr-Si sintered body is 40% by mass or more and 99% by mass or less. The content of the Si phase in the Cr-Si sintered body may be preferably 60% by mass or more and 99% by mass or less, more preferably 80% by mass or more and 99% by mass or less. The higher the content of the Si phase, the higher the resistivity of the Cr-Si sintered body, and it is possible to produce a thin film with high resistivity. For the same reason, the content of the Si phase in the Cr-Si sintered body may be 48.7% by mass or more and 62.6% by mass or less. The content of the CrSi2 phase in the Cr-Si sintered body may be 1% by mass or more and 60% by mass or less, preferably 1% by mass or more and 40% by mass or less, more preferably 1% by mass or more and 20% by mass or less. The smaller the content of the CrSi2 phase, the higher the resistivity of the Cr-Si sintered body, and it is possible to produce a thin film with high resistivity. However, if the content of the CrSi2 phase is too small, the Cr-Si sintered body is unlikely to have a resistivity that is unlikely to change with temperature changes. For the same reason, the content of the CrSi2 phase in the Cr-Si sintered body may be 37.4% by mass or more and 51.3% by mass or less.

[0014] The relative density of the Cr-Si sintered body to the true density of the Cr-Si sintered body is 95% or more and 100% or less. If the relative density is lower than 95%, the mechanical strength of the Cr-Si sintered body decreases. If abnormal discharge (arcing) occurs during film formation by sputtering, the surface of the sputtering target melts or scatters, and particle defects (particles) occur in the thin film. Particle defects (particles) are coarse particles that are not vaporized during sputtering and are detached from the sputtering target and attached to the thin film. Since the frequency of occurrence of arcing and particle defects (particles) is easily suppressed, the relative density of the Cr-Si sintered body may be preferably 97% or more and 100% or less, more preferably 98% or more and 100% or less. For the same reason, the relative density of the Cr-Si sintered body may be 98.4% or more and 99.9% or less.

[0015] The average cystal grain size of the CrSi2 phase is 1 μm or more and 40 μm or less. If the average cystal grain size of the CrSi2 phase is larger than 40 μm, the mechanical strength of the Cr-Si sintered body drops sharply. Since a stable high mechanical strength is easily obtained, the average cystal grain size of the CrSi2 phase may be preferably 1 μm or more and 20 μm or less, more preferably 1 μm or more and 10 μm or less. For the same reason, the average cystal grain size of the CrSi2 phase may be 3 μm or more and 4 μm or less. The average crystal grain size of the Si phase is 1 μm or more and 30 μm or less. If the average crystal grain size of the Si phase is larger than 30 μm, the mechanical strength of the Cr-Si sintered body drops sharply. Since a stable high mechanical strength is easily obtained, the average crystal grain size of the Si phase may be preferably 1 μm or more and 20 μm or less, more preferably 1 μm or more and 10 μm or less. For the same reason, the average crystal grain size of the Si phase may be 3 μm or more and 5 μm or less. The average crystal grain size of each of the CrSi2 phase and the Si phase may be measured in a backscattered electron image of the surface or cross section of the polished Cr-Si-based sintered body. The backscattered electron image of the surface or cross section of the Cr-Si-based sintered body may be taken by a scanning electron microscope (SEM). The crystal grains of each of the CrSi2 phase and the Si phase in the backscattered electron image may be identified by the difference in crystal structure. The crystal structure and crystal orientation of each of the crystal grains of the CrSi2 phase and the Si phase may be identified based on an electron backscattered diffraction (EBSD) pattern measured by the SEM. The crystal grains of each of the CrSi2 phase and the Si phase in the backscattered electron image may be identified by the difference in composition (the presence or absence of Cr). The composition of each of the crystal grains of the CrSi2 phase and the Si phase may be identified by an energy dispersive X-ray spectroscopy (EDS) device attached to the SEM or an electron probe microanalyzer (EPMA). The grain size of each of the CrSi2 phase and the Si phase may be measured by a diameter method. That is, the grain size of the CrSi2 phase may be the diameter of a circle (equivalent circle diameter) having the same area as the cross-sectional area of ​​one grain of the CrSi2 phase exposed on the surface or cross-section of the Cr-Si sintered body. The grain size of the Si phase may be the diameter of a circle (equivalent circle diameter) having the same area as the cross-sectional area of ​​one grain of the Si phase exposed on the surface or cross-section of the Cr-Si sintered body. The areas of the grain sizes of each of the CrSi2 phase and the Si phase may be measured by commercially available image analysis software. The sum of the cross-sectional areas of the crystal grains of the CrSi2 phase in the backscattered electron image of the Cr-Si sintered body may be represented as s1. The true density of the CrSi2 phase may be represented as d1. The sum of the cross-sectional areas of the crystal grains of the Si phase in the backscattered electron image of the Cr-Si sintered body may be represented as s2. The true density of the Si phase may be represented as d2. The content (unit: mass%) of the CrSi2 phase in the Cr-Si sintered body may be approximately equal to (d1×s1) / {(d1×s1)+(d2×s2)}. The content (unit: mass%) of the Si phase in the Cr-Si sintered body may be approximately equal to (d2×s2) / {(d1×s1)+(d2×s2)}. As described above, the contents of the CrSi2 phase and the Si phase in the Cr-Si sintered body may be specified based on the sum of the cross-sectional areas of the crystal grains of the CrSi2 phase and the Si phase.

[0016] Since the occurrence of particle defects (particles) in the thin film is easily suppressed and the yield rate of the thin film is increased, the oxygen content in the Cr-Si sintered body may be 0 mass% or more and 1 mass% or less, preferably 0 mass% or more and 0.5 mass% or less, more preferably 0 mass% or more and 0.1 mass% or less, and most preferably 0 mass% or more and 0.05 mass% or less. For the same reason, the oxygen content in the Cr-Si sintered body may be 0.02 mass% or more and 0.07 mass% or less.

[0017] The flexural strength of the Cr-Si sintered body may be preferably 100 MPa or more and 500 MPa or less, more preferably 150 MPa or more and 500 MPa or less, and most preferably 200 MPa or more and 500 MPa or less. The higher the flexural strength of the Cr-Si sintered body, the less likely the Cr-Si sintered body is to break during the manufacturing process of the sputtering target, such as grinding and bonding, and the higher the yield rate of the sputtering target and the higher the productivity of the sputtering target. In addition, when the flexural strength of the Cr-Si sintered body is high, the sputtering target is less likely to break even if high power is supplied to the sputtering target during sputtering. For the same reason, the flexural strength of the Cr-Si sintered body may be 151 MPa or more and 291 MPa or less. The flexural strength of the Cr-Si sintered body is one of the indicators of the mechanical strength of the Cr-Si sintered body.

[0018] The total content of impurities in the Cr-Si sintered body is 0 mass ppm or more and 200 mass ppm or less, and the impurities are at least one element selected from the group consisting of Mn, Fe, Mg, Ca, Sr, and Ba. That is, the total content of Mn, Fe, Mg, Ca, Sr, and Ba in the Cr-Si sintered body is 200 mass ppm or less. By making the total content of impurities 200 mass ppm or less, the Cr-Si sintered body has high mechanical strength, and the occurrence of particle defects (particles) in the thin film is sufficiently suppressed. For the same reason, the total content of the above impurities in the Cr-Si sintered body may be preferably 0 mass ppm or more and 100 mass ppm or less, more preferably 0 mass ppm or more and 50 mass ppm or less. For the same reason, the total content of the above impurities in the Cr-Si sintered body may be 19.78 mass ppm or more and 31.00 mass ppm or less.

[0019] Since the Cr-Si sintered body tends to have high mechanical strength and tends to suppress the occurrence of particle defects (particles) in the thin film, the total content of Fe and Mn in the Cr-Si sintered body may be preferably 0 ppm by mass or more and 100 ppm by mass or less, more preferably 0 ppm by mass or more and 50 ppm by mass or less, or 19.29 ppm by mass or more and 30.49 ppm by mass or less.

[0020] Since the Cr-Si sintered body tends to have high mechanical strength and tends to suppress the occurrence of particle defects (particles) in the thin film, the total content of Mg, Ca, Sr and Ba in the Cr-Si sintered body may be preferably 0 mass ppm or more and 3 mass ppm or less, more preferably 0 mass ppm or more and 2 mass ppm or less, or 0.49 mass ppm or more and 2.99 mass ppm or less.

[0021] A method for producing a Cr-Si sintered body according to this embodiment will be described below.

[0022] The method for producing a Cr-Si based sintered body according to this embodiment includes the steps of: (1) preparing an alloy powder in which both the CrSi2 phase and the Si phase are contained within one alloy particle; and (2) sintering the alloy powder at a sintering temperature of 1100 to 1400°C while applying a pressure of 50 MPa or less to the alloy powder, thereby obtaining a Cr-Si based sintered body.

[0023] Hereinafter, each step of the method for producing the Cr-Si sintered body will be described.

[0024] (1) Preparation of alloy powder Pure chromium and pure silicon are used as raw materials for the alloy powder. The purity of each of the pure chromium and pure silicon is preferably 99.9% by mass or more, more preferably 99.99% by mass or more, and most preferably 99.999% by mass or more. By preparing the alloy powder from high-purity pure chromium and pure silicon, it is possible to manufacture a Cr-Si sintered body in which the total content of the above impurities in the Cr-Si sintered body is 200 mass ppm or less. The impurities in each raw material cause abnormal grain growth in the sintering process. Furthermore, the impurities in each raw material are a source of particle defects (particles) during film formation by sputtering of the Cr-Si sintered body. It is preferable that the oxygen content in each raw material is small. The higher the oxygen content in each raw material, the higher the oxygen content in the Cr-Si sintered body, and particle defects (particles) are more likely to occur during film formation by sputtering. To produce a Cr-Si sintered body having a Si phase content of 40% by mass or more, the proportion of pure silicon in the raw alloy powder may be preferably 71% by mass to 99% by mass, or 75% by mass to 82% by mass. For the same reason, the proportion of pure chromium in the raw alloy powder may be preferably 1% by mass to 29% by mass, or 18% by mass to 25% by mass.

[0025] In the alloy powder preparation process, the alloy powder is produced through a process of rapidly cooling the liquid phase of an alloy containing chromium and silicon by gas atomization, quenched ribbon (strip casting), arc melting, etc. In particular, the alloy powder is preferably produced by gas atomization.

[0026] In the gas atomization method, molten metal is obtained from pure chromium and pure silicon by high-frequency induction melting. The molten metal is dropped into a chamber filled with an inert gas. By blowing high-pressure gas onto the dropped molten metal, many fine droplets are formed from the molten metal, and each droplet is rapidly cooled in the chamber. As a result, an alloy powder containing a fine crystal structure is obtained. In particular, each alloy particle constituting the alloy powder formed by the gas atomization method is a nearly spherical particle with a diameter of about several tens of μm. In one alloy particle formed by the gas atomization method, fine crystal grains of the CrSi2 phase with an average crystal grain size of 40 μm or less and the Si phase with an average crystal grain size of 30 μm or less are formed. The specific surface area of ​​the spherical alloy particle is smaller than that of alloy particles having other shapes, and the crystal grains in the alloy particle are fine. As a result, the oxidation of the alloy particles during the manufacturing process of the Cr-Si sintered body is suppressed, the oxygen content in the Cr-Si sintered body is reduced, and the mechanical strength of the Cr-Si sintered body is increased. In the case of a Cr-Si sintered body produced by mixing and sintering fine powders smaller than the above-mentioned spherical particles, the mechanical strength is high, but the oxygen content is high. In contrast, in the case of a Cr-Si sintered body produced by mixing and sintering coarse powders larger than the above-mentioned spherical particles, the oxygen content is low, but the mechanical strength is low. In order to produce a Cr-Si sintered body in which the average crystal grain size of the CrSi2 phase is 40 μm or less and the average crystal grain size of the Si phase is 30 μm or less, the grain size of the alloy powder may be preferably 1 μm or more and 300 μm or less.

[0027] The temperature of the molten metal in the gas atomization method is preferably melting temperature + 50 ° C or more and melting temperature + 300 ° C or less, more preferably melting temperature + 100 ° C or more and melting temperature + 250 ° C or less. Here, "melting temperature" means the temperature at which both pure chromium and pure silicon melt. The melting temperature is usually 1300 ° C or more and 1500 ° C or less. When the difference between the melting temperature and the temperature of the molten metal is small, the crystal phase with the higher melting point of the CrSi2 phase and the Si phase is likely to precipitate first, making it difficult to refine the crystal grains of each phase. On the other hand, when the difference between the melting temperature and the temperature of the molten metal is large, the alloy particles are likely to sinter with each other after atomization, and the alloy particles are likely to adhere to the inner wall surface of the chamber, resulting in a decrease in the recovery rate of the alloy powder.

[0028] The alloy powder obtained by the gas atomization method is preferably stored in a vacuum or in an inert atmosphere. The inert atmosphere may be an inert gas such as nitrogen or argon. If the alloy powder is stored in air, the surface of the alloy powder is easily oxidized, and the oxygen content in the alloy powder increases.

[0029] As a condition for the arc melting method, the output of the arc is important. Whether or not chromium and silicon, which have a large difference in melting point, can be alloyed is determined by the output of the arc. Since the melting point of chromium is 1863°C and the melting point of silicon is 1414°C, in order to alloy chromium and silicon, it is necessary to melt chromium and silicon with an arc current of 50 to 200A. If the arc current is too high, the amount of chromium sublimation increases. In order to suppress the sublimation of chromium, it is preferable that the arc current is 50A or more and 150A or less.

[0030] (2) Firing process (hot press method) In the sintering step, the alloy powder is preferably sintered in a pressure sintering furnace such as a hot press furnace. When the alloy powder is sintered in a non-pressure furnace, it is difficult to densify the Cr-Si sintered body due to the low diffusion coefficient of silicon.

[0031] The pressure applied to the alloy powder in the sintering step (sintering pressure) is preferably 50 MPa or less. If the sintering pressure exceeds 50 MPa, it is difficult to prepare a mold that can withstand the sintering pressure. When a large Cr-Si sintered body is produced, the sintering pressure is preferably 20 MPa or less, more preferably 10 MPa or less.

[0032] The temperature of the alloy powder in the sintering step (sintering temperature) is 1100°C or more and 1400°C or less. If the sintering temperature is less than 1100°C, the density of the Cr-Si sintered body is not sufficiently increased. If the sintering temperature exceeds 1400°C, the alloy powder may melt depending on the sintering pressure. In addition, the cooling rate of the Cr-Si sintered body after being heated at the above sintering temperature is not particularly limited. The cooling rate can be appropriately determined taking into consideration the capacity of the sintering furnace, the size and shape of the Cr-Si sintered body, and the fragility of the Cr-Si sintered body.

[0033] The time (sintering time) for which the sintering pressure and sintering temperature are held at the above values ​​is from 1 hour to 5 hours. If the sintering time is shorter than 1 hour, temperature unevenness is likely to occur in the sintering furnace and the mold, and it is difficult to uniformly form a crystal structure composed of the CrSi2 phase and the Si phase in the Cr-Si sintered body. In contrast, if the sintering time is longer than 5 hours, the productivity of the Cr-Si sintered body is reduced. By controlling the sintering pressure, sintering temperature and sintering time within the above ranges, a Cr-Si sintered body having a relative density of 95% or more can be produced.

[0034] The atmosphere for the sintering step is not particularly limited, but in order to suppress oxidation of the Cr-Si sintered body, the atmosphere for the sintering step is preferably a vacuum or an inert atmosphere such as argon.

[0035] The Cr-Si sintered body produced by the above method may be processed (grinded or cut) to form a plate-shaped Cr-Si sintered body. The processing means for the Cr-Si sintered body may be a machining machine such as a surface grinder, a cylindrical grinder, a lathe, a cutting machine, or a machining center.

[0036] In the method for producing a sputtering target containing a Cr-Si-based sintered body, the Cr-Si-based sintered body may be bonded to a backing plate or a backing tube as necessary. The backing plate and the backing tube may each be made of oxygen-free copper or titanium. The bonding between the Cr-Si-based sintered body and the backing plate or the backing tube may be bonded using indium (In) solder or the like.

[0037] The composition of the thin film produced from the sputtering target containing the Cr-Si-based sintered body may be substantially the same as the composition of the Cr-Si-based sintered body. The thin film may further contain other additive elements (dopants, etc.) in addition to Cr and Si. EXAMPLES

[0038] The present invention will be described in detail with reference to the following examples and comparative examples. The present invention is not limited to the following examples. The "sintered body" described below means a Cr-Si sintered body. The "wt" (weight) described below may be rephrased as mass. In the examples and comparative examples, the following measurements were carried out.

[0039] (1) Relative density of sintered body The relative density of the sintered body was measured by a method conforming to JIS R 1634. The bulk density d' of the sintered body was measured by the Archimedes method. The relative density of the sintered body is the bulk density d' of the sintered body divided by the true density d of the sintered body (d' / d). The true density d of the sintered body is the arithmetic mean represented by the following formula A. a in formula A is the weight (unit: g) of the CrSi2 phase contained in the sintered body. b in formula A is the weight (unit: g) of the Si phase contained in the sintered body. 4.98 in formula A is the true density of the CrSi2 phase (unit: g / cm 3 ) in the formula A is the true density of the Si phase (g / cm 3 ). d=(a+b) / {(a / 4.98)+(b / 2.3)} (A)

[0040] (2) Average grain size <CrSi2 phase> The backscattered electron image of the surface of the sintered body that had been mirror-polished was taken by a scanning electron microscope. The backscattered electron image was taken at at least three locations within the surface of the sintered body. The particle size of each of 300 or more CrSi2 phase crystal grains in the backscattered electron image was measured by the diameter method. That is, the particle size of each crystal grain is the equivalent circle diameter. By the above method, the average crystal grain size of the CrSi2 phase was measured. <Si phase> The backscattered electron image of the surface of the sintered body that had been mirror-polished was taken by an electrolytic emission type scanning electron microscope equipped with an EBSD pattern measuring device. The backscattered electron image was taken at at least three locations within the surface of the sintered body. The particle size of each of 300 or more Si phase crystal grains in the backscattered electron image was measured by the diameter method. That is, the particle size of each crystal grain is the equivalent circle diameter. A crystal interface with an azimuth difference of 5° or more was determined to be a grain boundary. By the above method, the average crystal grain size of the Si phase was measured. (Observation conditions of the scanning electron microscope) Accelerating voltage: 20 kV

[0041] (3) Flexural strength The flexural strength of the sintered body was measured by a method conforming to JIS R 1601. (Measurement conditions of the flexural strength) Test method: Three-point bending test Distance between supports: 30 mm Sample size: 3 × 4 × 40 mm Crosshead speed: 0.5 mm / min.

[0042] (4) Analysis of the oxygen content in the sintered body After grinding 1 mm or more of the surface of the sintered body, the oxygen content in a sample cut out from an arbitrary part of the sintered body was measured. Measurement method: Impulse furnace melting-infrared absorption method Apparatus: LECO TC436 oxygen / nitrogen analyzer

[0043] (5) Analysis of the content of metallic impurities in the sintered body After grinding the surface of the sintered body by 1 mm or more, a sample was cut out from any part of the sintered body. The content of each element (including impurities) in the sample was measured. Measurement method: Glow discharge mass spectrometry (GDMS)

[0044] (6) Sputtering test (Examples 4 to 6 and Comparative Examples 1 to 3) A disk was cut out from any location of the sintered body. The size of the disk was 10.16 cmφ. A sputtering target was made from the disk by indium bonding. A thin film was formed on the surface of a substrate by a sputtering test using this sputtering target. The size of the substrate was 5 cm × 5 cm. The target was checked for cracks after sputtering. The number of particle defects (number of particles) formed on the surface of the substrate after sputtering was counted.

[0045] Example 1 By gas atomization, alloy powder (raw powder) was produced from 18wt% Cr flakes and 82wt% Si flakes. The purity of the Cr flakes was 4N (99.99wt%). The purity of the Si flakes was 5N (99.999wt%). In the gas atomization method, Cr flakes and Si flakes were melted in a carbon crucible to produce a molten metal at 1600°C. The alloy powder obtained by the gas atomization method was classified using a sieve in the atmosphere to adjust the particle size of the alloy powder. The mesh size of the sieve was 300μm. In other words, alloy powder with a particle size of 300μm or less was collected.

[0046] The alloy powder was placed in a carbon mold and sintered by hot pressing to obtain a sintered body. The carbon mold had a diameter of 53 mm. The hot pressing was performed under the following conditions. The sintered body had a diameter of 53 mm and a thickness of 7 mm. No microcracks were formed in the sintered body. (Firing conditions) Firing furnace: Hot press furnace Heating rate: 200℃ / hour Heating atmosphere: vacuum (reduced pressure atmosphere) Firing temperature: 1300℃ Firing pressure: 30MPa Baking time: 3 hours

[0047] Example 2 In the gas atomization method of Example 2, alloy powder was produced from 25 wt% Cr flakes and 75 wt% Si flakes. The temperature of the molten metal in the gas atomization method of Example 2 was 1550° C. The firing pressure in Example 2 was 10 MPa. Except for the above, the sintered body of Example 2 was produced in the same manner as in Example 1. In the sintered body of Example 2, no microcracks were formed.

[0048] Example 3 The firing temperature and firing pressure in the hot non-resist method of Example 3 are shown in the following Table 1. The sintered body of Example 3 was produced in the same manner as in Example 2, except for the firing temperature and firing pressure. No microcracks were formed in the sintered body of Example 3.

[0049] Example 4 The firing temperature in the hot pressing method of Example 4 is shown in Table 1 below. In the hot pressing method of Example 4, a sintered body was produced using a mold of a different size from that of Example 1. The size of the sintered body of Example 4 was 130 mmφ×7 mmt. Except for these details, the sintered body of Example 4 was produced in the same manner as Example 1. No microcracks were formed in the sintered body of Example 4.

[0050] Example 5 In the hot pressing method of Example 5, a sintered body was produced using a mold of a different size from that of Example 1. The size of the sintered body of Example 5 was 130 mmφ×7 mmt. Except for these details, the sintered body of Example 5 was produced in the same manner as in Example 3. No microcracks were formed in the sintered body of Example 5.

[0051] Example 6 In the hot pressing method of Example 6, a sintered body was produced using a mold of a different size from that of Example 1. The size of the sintered body of Example 6 was 130 mmφ×7 mmt. In the gas atomizing method of Example 6, an alloy powder was produced from 20 wt% Cr flakes and 80 wt% Si flakes. The sintering temperature, sintering pressure and sintering time in the hot pressing method of Example 6 are shown in Table 1 below. Except for the above, the sintered body of Example 6 was produced in the same manner as in Example 1. In the sintered body of Example 6, no microcracks were formed.

[0052] Comparative Example 1 In Comparative Example 1, the gas atomization method was not used. The raw material powder of Comparative Example 1 was produced by firing and pulverizing a mixture of Cr powder and Si powder. The mixture of Cr powder and Si powder was fired at 1250°C. The purity of the Cr powder was 4N (99.99wt%). The purity of the Si powder was 5N (99.999wt%). After the Fe can containing the raw material powder was vacuum degassed, the Fe can was sealed by welding. The raw material powder in the Fe can was fired by a hot isostatic press (HIP) method to obtain a sintered body of Comparative Example 1. The firing temperature, firing pressure, and firing time in the HIP method are shown in Table 1 below.

[0053] Comparative Example 2 In Comparative Example 2, gas atomization was not performed. The raw powder of Comparative Example 2 was prepared by mixing CrSi2 powder and Si powder. This raw powder was sintered by hot pressing to obtain the sintered body of Comparative Example 2. The purity of the Si powder was 5N (99.999wt%). The Cr content in the raw powder of Comparative Example 2 is shown in Table 1 below. The Si content in the raw powder of Comparative Example 2 is shown in Table 1 below. A sintered body of Comparative Example 2 was produced in the same manner as in Example 4, except for the above points.

[0054] Comparative Example 3 In Comparative Example 3, gas atomization was not performed. The raw material powder of Comparative Example 3 was produced by mixing Cr powder and Si powder. This raw material powder was sintered by hot pressing to obtain the sintered body of Comparative Example 3. The purity of the Cr powder was 4N (99.99wt%). The purity of the Si powder was 5N (99.999wt%). The Cr content in the raw material powder of Comparative Example 3 is shown in Table 1 below. The Si content in the raw material powder of Comparative Example 3 is shown in Table 1 below. A sintered body of Comparative Example 3 was produced in the same manner as in Example 4, except for the above points.

[0055] The sintered bodies of Examples 1 to 6 and Comparative Examples 1 to 3 were composed of a crystalline CrSi2 phase and a crystalline Si phase. The contents of the Si phase in the sintered bodies of Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Table 1 below. The manufacturing methods of the sintered bodies of Examples 1 to 6 and Comparative Examples 1 to 3 are outlined in Table 1 below. The results of the above measurements on the sintered bodies of Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Tables 1 and 2 below. In Table 2 below, "ppm" means wt ppm.

[0056] [Table 1]

[0057] [Table 2]

[0058] The Cr-Si sintered bodies of Examples 1 to 6 were superior in flexural strength to the Cr-Si sintered bodies of Comparative Examples 1 to 3. The Cr-Si sintered bodies of Examples 4 to 6 were superior to the Cr-Si sintered bodies of Comparative Examples 1 to 3 in that they were less likely to crack during sputtering and could suppress particle defects (number of particles) in the thin film. [Industrial Applicability]

[0059] For example, the Cr-Si-based sintered body according to one aspect of the present invention may be used as a thin film material (sputtering target) for semiconductors, solar cells, automotive sensors, or home appliance sensors.

Claims

1. A preparation step of preparing an alloy powder from pure chromium and pure silicon by a gas atomization method; a sintering step of sintering the alloy powder at a sintering temperature of 1100 to 1400° C. while pressing the alloy powder at a pressure of 50 MPa or less to obtain a Cr-Si-based sintered body containing Cr and Si; Equipped with The Cr-Si sintered body is a crystalline CrSi ２ phase and a crystalline Si phase, The content of the Si phase in the Cr-Si sintered body is 40 mass% or more, The relative density of the Cr-Si sintered body to the true density of the Cr-Si sintered body is 95% or more; The CrSi ２ The average grain size of the phase is 40 μm or less, The average grain size of the Si phase is 30 μm or less, The total content of impurities in the Cr-Si sintered body is 200 ppm by mass or less, The impurity is at least one element selected from the group consisting of Mn, Fe, Mg, Ca, Sr and Ba. A method for producing a Cr-Si sintered body.

2. The firing time of the firing step is 1 hour or more and 5 hours or less. The method for producing the Cr-Si sintered body according to claim 1.

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

4. The purity of the pure chromium is 99.9% by mass or more, The purity of the pure silicon is 99.9% by mass or more. The method for producing the Cr-Si sintered body according to any one of claims 1 to 3.

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