Method for manufacturing Cr-Si sintered bodies

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 sintered body, a sputtering target, and a method for manufacturing a thin film, which are used for forming a thin film or the like.

Background Art

[0002] In recent years, silicides such as CrSi2 have a high resistivity (unit: Ω·cm) that hardly changes with temperature changes, and thus are used as thin films in many technical fields such as semiconductors, solar cells, automotive sensors, and household appliance sensors. In industrial thin film manufacturing, the sputtering method is frequently used. However, generally, since the mechanical strength of a composition containing a silicide is low, a sputtering target containing a silicide is likely to crack during processing of the sputtering target and during discharge during film formation. Therefore, it is difficult to use a conventional composition containing a silicide as a sputtering target. Patent Document 1 below discloses a method for manufacturing a sputtering target containing a crystal phase of chromium (Cr) and silicon (Si) by a spraying method in order to improve the mechanical strength of the sputtering target. However, in a sputtering target manufactured by the spraying method, at a location where the Cr content is low, the mechanical strength does not increase sufficiently. Further, in the method described in Patent Document 1, since the sputtering target is produced by a spraying method using a silicide powder, the mechanical strength of the sputtering target does not increase sufficiently.

[0003] Patent Document 2 below discloses a method for manufacturing a composition having a fine eutectic structure containing Si and a silicide by a melting method. However, in the composition manufactured by the melting method, since the ratio of the eutectic structure is low and a large amount of primary crystals are present, the mechanical strength of the composition does not increase sufficiently. When such a composition is enlarged, it becomes difficult to control the crystal structure due to differences in the cooling rate within the composition, and the variation in the mechanical strength in the composition becomes large.

[0004] Patent documents 3 and 4 below also disclose sputtering targets containing silicide. However, Patent document 3 does not describe the content of impurities in the sputtering target. Patent document 4 describes the content of oxygen and carbon, respectively, in the sputtering target. Alternatively, Patent document 4 describes a step in the manufacturing process of the sputtering target in which silicide powder is mechanically pulverized. However, Patent document 4 does not describe the content of metal impurities that degrade semiconductor film properties. [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 [Overview of the project] [Problems that the invention aims to solve]

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

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

[0008] In other words, the method for manufacturing a Cr-Si-based sintered body, a sputtering target, and a thin film according to one aspect of the present invention is as follows. (1) A Cr-Si sintered body containing chromium (Cr) and silicon (Si), characterized in that the crystal structure assigned by X-ray diffraction consists of chromium silicide (CrSi2) and silicon (Si), the Si phase is present in bulk at a concentration of 40% by mass or more, the sintered body density is 95% or more, the average particle size of the CrSi2 phase is 40 μm or less and the average particle size of the Si phase is 30 μm or less, and the total amount of impurities of Mn + Fe + Mg + Ca + Sr + Ba is 200 ppm or less. In other words, a Cr-Si sintered material according to one aspect of the present invention is a Cr-Si sintered material containing Cr and Si, wherein the Cr-Si sintered material contains a crystalline CrSi2 phase and a crystalline Si phase, the Si phase content in the Cr-Si sintered material is 40% by mass or more, the relative density of the Cr-Si sintered material to the true density of the Cr-Si sintered material 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, the total impurity content in the Cr-Si sintered material is 200 ppm by mass 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 it has a flexural strength of 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) The Cr-Si sintered body according to either (1) or (2), characterized in that the amount of oxygen in the bulk is 1% by mass or less. In other words, the oxygen content in the Cr-Si sintered body according to one aspect of the present invention may be 1% by mass or less. (4) A sputtering target characterized by being made of a Cr-Si sintered body as described in any of (1) to (3). In other words, a sputtering target according to one aspect of the present invention includes the above-mentioned Cr-Si sintered body. (5) A method for manufacturing a thin film, characterized by sputtering using the sputtering target described in (4). In other words, a method for manufacturing a thin film according to one aspect of the present invention comprises the step of forming a thin film by sputtering using the above-mentioned sputtering target. [Effects of the Invention]

[0009] According to one aspect of the present invention, a Cr-Si sintered body containing Cr and Si and having high mechanical strength, a sputtering target containing the sintered body, and a method for manufacturing a thin film using the sputtering target are provided. [Modes for carrying out the invention]

[0010] Preferred embodiments of the present invention are described below. The present invention is not limited to the embodiments described below. "Mass %" as described below may be replaced with "weight % (wt%)". The Cr-Si sintered body described below may be replaced with "bulk".

[0011] The Cr-Si sintered body according to this embodiment contains Cr and Si. The Cr-Si sintered body contains a crystalline CrSi2 phase and a crystalline Si phase. The Si phase content in the Cr-Si sintered body is 40% by mass or more. The relative density of the Cr-Si sintered body to its true density is 95% or more. The average grain size of the CrSi2 phase is 40 μm or less, and the average grain size of the Si phase is 30 μm or less. The total impurity content in the Cr-Si sintered body is 200 ppm by mass 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 includes the above-mentioned Cr-Si sintered body. A method for manufacturing a thin film according to one aspect of the present invention comprises the step of forming a thin film by sputtering using the above-described sputtering target. Because the Cr-Si sintered body according to this embodiment has excellent mechanical strength, the sputtering target according to this embodiment is less prone to cracking during sputtering under high power. Therefore, high productivity can be achieved in the method for manufacturing thin films by sputtering using the sputtering target according to this embodiment. Details of this embodiment are as follows.

[0012] The CrSi2 phase, Si phase, and their crystal structures in a Cr-Si sintered body may be detected and identified by X-ray diffraction (XRD). The crystal structure of the CrSi2 phase belongs to the hexagonal system. The crystal structure of the Si phase (diamond structure) belongs to the cubic system. The CrSi2 phase and Si phase may be mixed in the Cr-Si sintered body. The CrSi2 phase may contain one or more crystal grains made of CrSi2. The Si phase may contain one or more crystal grains made of Si. The Cr-Si sintered body may consist only of the CrSi2 phase and the Si phase. When the Cr-Si sintered body consists only of the CrSi2 phase and the Si phase, the Cr-Si sintered body tends to have high mechanical strength. If the silicification reaction of Cr in a 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 stoichiometric ratios are locally present in the Cr-Si sintered body, microcracks caused by density differences within the Cr-Si sintered body will be inherent in the Cr-Si sintered body. Large Cr-Si sintered bodies, in particular, are prone to cracking, making it difficult to manufacture such Cr-Si sintered bodies with a high yield rate. Furthermore, if 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 prone to cracking during discharge, reducing the productivity of the film deposition process. However, as long as the Cr—Si sintered body has sufficiently high mechanical strength and the cracking of the sputtering target during sputtering is sufficiently suppressed, the Cr—Si sintered body may contain at least one of a small amount of other silicide phases and a small amount of chromium phase in addition to the CrSi₂ phase and the Si phase.

[0013] The content of the Si phase in the Cr—Si sintered body is 40% to 99% by mass. The content of the Si phase in the Cr—Si sintered body is preferably 60% to 99% by mass, more preferably 80% to 99% by mass. 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 having a high resistivity. For the same reason, the content of the Si phase in the Cr—Si sintered body may be 48.7% to 62.6% by mass. The content of the CrSi₂ phase in the Cr—Si sintered body is 1% to 60% by mass, preferably 1% to 40% by mass, more preferably 1% to 20% by mass. The lower 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 having a high resistivity. However, when the content of the CrSi₂ phase is too small, the Cr—Si sintered body is unlikely to have a resistivity that hardly changes with temperature changes. For the same reason, the content of the CrSi₂ phase in the Cr—Si sintered body may be 37.4% to 51.3% by mass.

[0014] The relative density of a Cr-Si sintered body to its true density is preferably 95% to 100%. If the relative density is lower than 95%, the mechanical strength of the Cr-Si sintered body decreases. If abnormal discharge (arking) occurs during film deposition by sputtering, the surface of the sputtering target melts or scatters, and particle defects occur in the thin film. Particle defects are coarse particles that detach from the sputtering target without vaporizing during sputtering and adhere to the thin film. To easily suppress the frequency of arcing and particle defects, the relative density of the Cr-Si sintered body may be preferably 97% to 100%, more preferably 98% to 100%. For similar reasons, the relative density of the Cr-Si sintered body may be 98.4% to 99.9%.

[0015] The average crystalline grain size of the CrSi2 phase is between 1 μm and 40 μm. If the average crystalline grain size of the CrSi2 phase exceeds 40 μm, the mechanical strength of the Cr-Si sintered body decreases sharply. To ensure stable and high mechanical strength, the average crystalline grain size of the CrSi2 phase is preferably between 1 μm and 20 μm, and more preferably between 1 μm and 10 μm. For similar reasons, the average crystalline grain size of the CrSi2 phase may be between 3 μm and 4 μm. The average grain size of the Si phase is between 1 μm and 30 μm. If the average grain size of the Si phase exceeds 30 μm, the mechanical strength of the Cr-Si sintered body decreases sharply. To ensure stable and high mechanical strength, the average grain size of the Si phase is preferably between 1 μm and 20 μm, more preferably between 1 μm and 10 μm. For similar reasons, the average grain size of the Si phase may be between 3 μm and 5 μm. 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 sintered body. The backscattered electron image of the surface or cross-section of the Cr—Si 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 the crystal grains of each of the CrSi2 phase and the Si phase may be specified based on an electron backscatter diffraction (EBSD) pattern measured by SEM. The crystal grains of each of the CrSi2 phase and the Si phase in the backscattered electron image may also be identified by the difference in composition (presence or absence of Cr). The composition of the crystal grains of each of the CrSi2 phase and the Si phase may be specified by an energy dispersive X-ray spectroscopy (EDS) apparatus attached to the SEM or an electron probe microanalyzer (EPMA). The crystal grain size of each of the CrSi2 phase and the Si phase may be measured by the diameter method. That is, the crystal grain size of the CrSi2 phase may be the diameter (equivalent circle diameter) of a circle having the same area as the cross-sectional area of one crystal grain of the CrSi2 phase exposed on the surface or cross-section of the Cr—Si sintered body. The crystal grain size of the Si phase may be the diameter (equivalent circle diameter) of a circle having the same area as the cross-sectional area of one crystal grain of the Si phase exposed on the surface or cross-section of the Cr—Si sintered body. The area of the crystal grain size of each of the CrSi2 phase and the Si phase may be measured by commercially available image analysis software. The total cross-sectional area 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 total cross-sectional area 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, based on the total cross-sectional area of the crystal grains of each of the CrSi2 phase and the Si phase, the content of each of the CrSi2 phase and the Si phase in the Cr—Si sintered body may be specified.

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

[0017] The flexural strength of the Cr-Si sintered body is preferably 100 MPa to 500 MPa, more preferably 150 MPa to 500 MPa, and most preferably 200 MPa to 500 MPa. The higher the flexural strength of the Cr-Si sintered body, the less likely it is to crack during the manufacturing process of sputtering targets, such as grinding and bonding, resulting in a higher yield rate of sputtering targets and improved productivity. Furthermore, if the flexural strength of the Cr-Si sintered body is high, the sputtering target is less likely to crack even if high power is supplied to it during sputtering. For similar reasons, the flexural strength of the Cr-Si sintered body may be 151 MPa to 291 MPa. The flexural strength of the Cr-Si sintered body is one indicator of the mechanical strength of the Cr-Si sintered body.

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

[0019] Since Cr-Si sintered bodies tend to have high mechanical strength and the generation of particle defects (particles) in thin films is easily suppressed, the total content of Fe and Mn in Cr-Si sintered bodies may preferably be 0 ppm to 100 ppm by mass, more preferably 0 ppm to 50 ppm by mass, or 19.29 ppm to 30.49 ppm by mass.

[0020] Since Cr-Si sintered bodies tend to have high mechanical strength and the generation of particle defects (particles) in thin films is easily suppressed, the total content of Mg, Ca, Sr, and Ba in Cr-Si sintered bodies may preferably be 0 ppm to 3 ppm by mass, more preferably 0 ppm to 2 ppm by mass, or 0.49 ppm to 2.99 ppm by mass.

[0021] The following describes a method for manufacturing a Cr-Si-based sintered body according to this embodiment.

[0022] The method for producing a Cr-Si 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 a single alloy particle, and (2) obtaining a Cr-Si sintered body by sintering the alloy powder at a firing temperature of 1100 to 1400°C while pressurizing the alloy powder at a pressure of 50 MPa or less.

[0023] The manufacturing method for Cr-Si sintered bodies is described below, step by step.

[0024] (1) Preparation process of alloy powder Pure chromium and pure silicon are used as raw materials for the alloy powder. The purity of the pure chromium and pure silicon is preferably 99.9% by mass or higher, more preferably 99.99% by mass or higher, and most preferably 99.999% by mass or higher. By preparing alloy powder from high-purity pure chromium and pure silicon, a Cr-Si sintered body can be manufactured in which the total content of the above-mentioned impurities in the Cr-Si sintered body is 200 ppm by mass or less. Impurities in each raw material cause abnormal grain growth during the firing process. Furthermore, impurities in each raw material become a source of particle defects during film formation of the Cr-Si sintered body by sputtering. It is preferable that the oxygen content in each raw material be low. The higher the oxygen content in each raw material, the higher the oxygen content in the Cr-Si sintered body, and the more likely particle defects are 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 materials of the alloy powder may preferably be 71% by mass or more and 99% by mass or less, or 75% by mass or more and 82% by mass or less. For similar reasons, the proportion of pure chromium in the raw materials of the alloy powder may preferably be 1% by mass or more and 29% by mass or less, or 18% by mass or more and 25% by mass or less.

[0025] In the alloy powder preparation process, the alloy powder is produced by rapidly cooling the liquid phase of the alloy containing chromium and silicon using methods such as gas atomization, rapid strip casting, or arc melting. In particular, the alloy powder is preferably produced by the gas atomization method.

[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 inert gas. By blowing high-pressure gas onto the dropped molten metal, numerous 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 crystalline structure is obtained. In particular, each alloy particle constituting the alloy powder formed by the gas atomization method is a roughly spherical particle with a diameter of several tens of micrometers. Within a single 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 ​​spherical alloy particles is smaller than that of alloy particles with other shapes, and the crystal grains within the alloy particles are fine. As a result, oxidation of alloy particles during the manufacturing process of Cr-Si sintered bodies is suppressed, the oxygen content in Cr-Si sintered bodies is reduced, and the mechanical strength of Cr-Si sintered bodies is increased. In the case of a Cr-Si sintered body produced by mixing and firing fine powder smaller than the spherical particles described above, 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 firing coarse powder larger than the spherical particles described above, the oxygen content is low, but the mechanical strength is low. In order to produce a Cr-Si sintered body in which the average grain size of the CrSi2 phase is 40 μm or less and the average grain size of the Si phase is 30 μm or less, the grain size of the alloy powder may preferably be between 1 μm and 300 μm.

[0027] In the gas atomization method, the temperature of the molten metal is preferably between the melting temperature + 50°C and above, and between the melting temperature + 300°C, more preferably between the melting temperature + 100°C and above, and between the melting temperature + 250°C. Here, "melting temperature" refers to the temperature at which both pure chromium and pure silicon melt. The melting temperature is usually between 1300°C and 1500°C. When the difference between the melting temperature and the temperature of the molten metal is small, the crystalline phase with the higher melting point among the CrSi2 phase and Si phase tends 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 tend to sinter with each other after atomization, the alloy particles tend to adhere to the inner wall surface of the chamber, and the recovery rate of the alloy powder decreases.

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

[0029] In arc melting, the arc power is a crucial condition. The arc power determines whether chromium and silicon, which have a large difference in melting points, can be alloyed. Since the melting point of chromium is 1863°C and the melting point of silicon is 1414°C, it is necessary to melt chromium and silicon with an arc current of 50 to 200 A in order to alloy them. If the arc current is too high, the amount of chromium sublimation will increase. To suppress chromium sublimation, it is preferable that the arc current is between 50 A and 150 A.

[0030] (2) Firing process (hot press method) In the firing process, it is preferable to fire the above-mentioned alloy powder in a pressurized firing furnace such as a hot press furnace. When the alloy powder is fired in a non-pressurized furnace, it is difficult to increase the density of the Cr-Si sintered body due to the low diffusion coefficient of silicon.

[0031] The pressure applied to the alloy powder during the firing process (firing pressure) is preferably 50 MPa or less. If the firing pressure exceeds 50 MPa, it is difficult to prepare a mold that can withstand the firing pressure. When large Cr-Si sintered bodies are manufactured, the firing pressure is preferably 20 MPa or less, more preferably 10 MPa or less.

[0032] The temperature of the alloy powder during the firing process (firing temperature) is between 1100°C and 1400°C. If the firing temperature is below 1100°C, the density of the Cr-Si sintered body will not increase sufficiently. If the firing temperature exceeds 1400°C, the alloy powder may melt depending on the firing pressure. Furthermore, the cooling rate of the Cr-Si sintered body after heating at the above firing temperature is not particularly limited. The cooling rate can be appropriately determined considering the capacity of the sintering furnace, the size and shape of the Cr-Si sintered body, and the tendency of the Cr-Si sintered body to crack, etc.

[0033] The firing pressure and firing temperature must be maintained at the above values ​​for a firing time of 1 to 5 hours. If the firing time is shorter than 1 hour, temperature variations are likely to occur in the firing furnace and mold, making it difficult to uniformly form a crystalline structure composed of CrSi2 phase and Si phase within the Cr-Si sintered body. Conversely, if the firing time is longer than 5 hours, the productivity of the Cr-Si sintered body will be reduced. By controlling the firing pressure, firing temperature, and firing time within the above range, a Cr-Si sintered body with a relative density of 95% or higher can be manufactured.

[0034] The atmosphere during the firing process is not particularly limited. However, to suppress oxidation of the Cr-Si sintered body, the atmosphere during the firing process is preferably a vacuum or an inert atmosphere such as argon.

[0035] A plate-shaped Cr-Si sintered body may be formed by processing (grinding or cutting, etc.) the Cr-Si sintered body produced by the above method. The processing means for the Cr-Si sintered body may be a surface grinder, cylindrical grinder, lathe, cutting machine, or machining center.

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

[0037] The composition of a thin film produced from a sputtering target containing a Cr-Si sintered body may be approximately the same as that of the Cr-Si sintered body. The thin film may further contain other additive elements (such as dopants) in addition to Cr and Si. [Examples]

[0038] The present invention will be described in detail by the following examples and comparative examples. The present invention is not limited to the following examples. The term "sintered body" as used below means a Cr-Si sintered body. The term "wt" (weight) as used below may be replaced with "mass". The following measurements were performed in the examples and comparative examples.

[0039] (1) Relative density of the sintered body The relative density of the sintered body was measured according to the method compliant with 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 value obtained by dividing the bulk density d' of the sintered body 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. In formula A, a is the weight (in g) of the CrSi2 phase contained in the sintered body. In formula A, b is the weight (in g) of the Si phase contained in the sintered body. In formula A, 4.98 is the true density (in g / cm³) of the CrSi2 phase. 3 ) is the true density of the Si phase (g / cm³). In equation A, 2.3 is the true density of the Si phase (g / cm³). 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 after mirror polishing 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 more than 300 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 after mirror polishing 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 more than 300 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 as a grain boundary. By the above method, the average crystal grain size of the Si phase was measured. (Observation conditions of scanning electron microscope) Acceleration 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 flexural strength) Test method: Three-point bending test Span distance: 30 mm Specimen size: 3 × 4 × 40 mm Crosshead speed: 0.5 mm / min.

[0042] (4) Analysis of 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 to a depth of 1 mm or more, a sample was cut from an arbitrary 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 (for Examples 4-6 and Comparative Examples 1-3) A disc was cut from an arbitrary location on the sintered body. The size of the disc was 10.16 cm in diameter. A sputtering target was fabricated from the disc by indium bonding. A sputtering test using this sputtering target formed a thin film on the surface of the substrate. The size of the substrate was 5 cm x 5 cm. The target was examined for cracks after sputtering. The number of particle defects (particle count) formed on the surface of the substrate after sputtering was counted.

[0045] (Example 1) Alloy powder (raw material powder) was prepared from 18 wt% Cr flakes and 82 wt% Si flakes using the gas atomization method. The purity of the Cr flakes was 4N (99.99 wt%). The purity of the Si flakes was 5N (99.999 wt%). In the gas atomization method, molten metal was prepared at 1600°C by melting the Cr flakes and Si flakes in a carbon crucible. The particle size of the alloy powder obtained by the gas atomization method was adjusted by classifying it using a sieve under atmospheric pressure. The sieve opening size was 300 μm. In other words, alloy powder with a particle size of 300 μm or less was recovered.

[0046] The alloy powder, placed in a carbon mold, was fired by a hot-pressing method to obtain a sintered body. The carbon mold had a diameter of 53 mm. The hot-pressing method was carried out 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°C / hour Heating atmosphere: Vacuum (reduced pressure atmosphere) Firing temperature: 1300℃ Firing pressure: 30 MPa Baking time: 3 hours

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

[0048] (Example 3) The firing temperature and firing pressure in the hot firing method of Example 3 are shown in Table 1 below. 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-press method of Example 4 is shown in Table 1 below. In the hot-press method of Example 4, a sintered body was produced using a mold of a different size than that used in Example 1. The size of the sintered body of Example 4 was 130 mmφ × 7 mmt. The sintered body of Example 4 was produced in the same manner as in Example 1, except for these differences. No microcracks were formed in the sintered body of Example 4.

[0050] (Example 5) In the hot-press method of Example 5, a sintered body was produced using a mold of a different size than that used in Example 1. The size of the sintered body in Example 5 was 130 mmφ × 7 mmt. The sintered body of Example 5 was produced in the same manner as in Example 3, except for these differences. No microcracks were formed in the sintered body of Example 5.

[0051] (Example 6) In the hot-press method of Example 6, a sintered body was produced using a mold of a different size than that used in Example 1. The size of the sintered body in Example 6 was 130 mmφ × 7 mmt. In the gas atomization method of Example 6, alloy powder was produced from 20 wt% Cr flakes and 80 wt% Si flakes. The firing temperature, firing pressure, and firing time in the hot-press method of Example 6 are shown in Table 1 below. Except for the above-mentioned points, the sintered body of Example 6 was fabricated in the same manner as in Example 1. No microcracks were formed in the sintered body of Example 6.

[0052] (Comparative Example 1) In Comparative Example 1, the gas atomization method was not used. The raw material powder for Comparative Example 1 was prepared by calcining and grinding a mixture of Cr powder and Si powder. The mixture of Cr powder and Si powder was calcined at 1250°C. The purity of the Cr powder was 4N (99.99 wt%). The purity of the Si powder was 5N (99.999 wt%). After vacuum degassing of the Fe can containing the above raw material powder, the Fe can was sealed by welding. The raw material powder in the Fe can was calcined by the Hot Isostatic Press (HIP) method to obtain the sintered body of Comparative Example 1. The calcination temperature, calcination pressure, and calcination time in the HIP method are shown in Table 1 below.

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

[0054] (Comparative Example 3) In Comparative Example 3, the gas atomization method was not used. The raw material powder for Comparative Example 3 was prepared by mixing Cr powder and Si powder. This raw material powder was fired by the hot press method to obtain the sintered body for Comparative Example 3. The purity of the Cr powder was 4N (99.99 wt%). The purity of the Si powder was 5N (99.999 wt%). 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. Except for the points mentioned above, the sintered body of Comparative Example 3 was produced in the same manner as in Example 4.

[0055] The sintered bodies of Examples 1-6 and Comparative Examples 1-3 each consisted of a crystalline CrSi2 phase and a crystalline Si phase. The Si phase content in the sintered bodies of Examples 1-6 and Comparative Examples 1-3 is shown in Table 1 below. An overview of the manufacturing methods for the sintered bodies of Examples 1-6 and Comparative Examples 1-3 is shown in Table 1 below. The results of the above measurements for the sintered bodies of Examples 1-6 and Comparative Examples 1-3 are shown in Tables 1 and 2 below. In Table 2 below, "ppm" means wt ppm.

[0056] [Table 1]

[0057] [Table 2]

[0058] Each of the Cr-Si sintered bodies in Examples 1 to 6 exhibited superior flexural strength compared to each of the Cr-Si sintered bodies in Comparative Examples 1 to 3. Each of the Cr-Si sintered bodies in Examples 4 to 6 was superior to each of the Cr-Si sintered bodies in Comparative Examples 1 to 3 in that it was less prone to cracking during sputtering and suppressed particle defects (number of particles) in the thin film. [Industrial applicability]

[0059] For example, a Cr-Si 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. Preparation steps include preparing alloy powders from pure chromium and pure silicon by gas atomization, A firing step to obtain a Cr-Si sintered body containing Cr and Si by firing the alloy powder at a firing temperature of 1100 to 1400°C while pressurizing the alloy powder at a pressure of 50 MPa or less, Equipped with, The Cr-Si sintered body is made of crystalline CrSi ２ It includes phases and crystalline Si phases, The Si phase content in the Cr-Si sintered body is 40% by mass or more. The relative density of the Cr-Si sintered body to its true density is 95% or more. The aforementioned CrSi ２ The average crystal 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 amount 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 manufacturing a Cr-Si sintered body.

2. The firing time for the aforementioned firing process is between 1 hour and 5 hours. A method for producing a Cr-Si sintered body according to claim 1.

3. The atmosphere during the firing process is an inert atmosphere. A method for producing a Cr-Si sintered body according to claim 1 or 2.

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

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