Polycrystalline silicon carbide molded body and method for producing same

Abstract

The present invention provides a polycrystalline silicon carbide molded body and a method for producing the same. The polycrystalline silicon carbide molded body is a plate-like body having a nitrogen content of more than 1000 mass ppm but no more than 5000 mass ppm, a resistivity of 0.0100 Ω⋅cm or below, and a thickness of 200 μm to 1000 μm. The average particle diameter of silicon carbide crystals on a first main surface of the plate-like body is 6.0 μm to 25.0 μm, the average particle diameter of silicon carbide crystals on a second main surface of the plate-like body is 6.0 μm to 25.0 μm, and the average particle diameter of silicon carbide crystals from the first main surface to the second main surface of the plate-like body is 6.0 μm to 25.0 μm. The average value of the difference between the particle diameter of the silicon carbide crystals on the first main surface of the plate-like body and the particle diameter of the silicon carbide crystals on the second main surface is 0.1 μm to 1.5 μm.

Description

Polycrystalline silicon carbide molded body and method for manufacturing the same

[0001] The present invention relates to a polycrystalline silicon carbide molded body and a method for producing the same.

[0002] Molded articles made of silicon carbide (SiC) (silicon carbide molded articles) have excellent properties such as heat resistance, corrosion resistance, and strength, and are used in a variety of applications. For example, Patent Documents 1 and 2 describe the use of silicon carbide as components for plasma etching equipment such as edge rings, electrode plates, and heaters used in semiconductor manufacturing.

[0003] Furthermore, Patent Document 3 discloses a semiconductor substrate comprising a single-crystal silicon carbide substrate and a polycrystalline silicon carbide substrate, wherein the single-crystal silicon carbide substrate and the polycrystalline silicon carbide substrate are bonded together via a predetermined interface layer.

[0004] Silicon carbide is a compound with strong covalent bonds, making it difficult to sinter. Therefore, it is difficult to obtain dense molded bodies using conventional sintering methods. Furthermore, when manufacturing silicon carbide molded bodies using sintering methods, a sintering aid is usually added to the powder raw material before sintering, making it difficult to obtain high-purity and high-density silicon carbide molded bodies.

[0005] For this reason, a manufacturing method utilizing the CVD (Chemical Vapor Deposition) method has been adopted as a method for producing silicon carbide molded bodies. The CVD method is a method of directly synthesizing a solid from a gas by supplying raw material gas onto a heated substrate and depositing a film. According to the CVD method, a dense molded body can be obtained without adding sintering aids. For example, Patent Document 4 discloses a technique for obtaining a polycrystalline silicon carbide molded body by the CVD method.

[0006] Japanese Patent Publication No. 2001-316821, Japanese Patent Publication No. 2001-220237, Japanese Patent No. 6387375, Japanese Patent No. 7155089

[0007] Polycrystalline silicon carbide molded bodies require various properties depending on their application. For example, as described in Patent Documents 1 and 2, when a polycrystalline silicon carbide molded body is used as a component for a plasma etching apparatus, a polycrystalline silicon carbide molded body with low resistivity is required in order to dissipate static electricity and generate plasma gas uniformly. Furthermore, when a polycrystalline silicon carbide molded body is used as a component for a plasma etching apparatus, a flat polycrystalline silicon carbide molded body is required.

[0008] Furthermore, as described in Patent Document 3, a flat polycrystalline silicon carbide molded body is necessary for joining a polycrystalline silicon carbide molded body to a single-crystal silicon carbide substrate. Also, when an electric current path is formed across the bonding surface between the polycrystalline silicon carbide molded body and the single-crystal silicon carbide substrate, a polycrystalline silicon carbide molded body with low resistivity is required.

[0009] To meet these demands, a polycrystalline silicon carbide molded body with low resistivity and flatness has been proposed, as described in Patent Document 4.

[0010] The inventors of the present invention conceived of increasing the nitrogen content in the resulting polycrystalline silicon carbide molded body by introducing nitrogen gas into the atmosphere during the manufacturing of the polycrystalline silicon carbide molded body, in order to produce a polycrystalline silicon carbide molded body with low resistivity.

[0011] However, the inventors investigated and found that when nitrogen gas is introduced to the polycrystalline silicon carbide molded body so that the nitrogen content exceeds 1000 ppm by mass, and film deposition is continued under the same conditions from the initial stage of deposition, the silicon carbide crystal particles tend to enlarge due to nucleation growth. This results in a significant difference between the particle size of the silicon carbide crystals on the first main surface and the particle size of the silicon carbide crystals on the second main surface, which has a major impact on residual stress, warping, and other factors.

[0012] Further, as the polycrystalline silicon carbide compact, for example, a plate-like body with a thickness of 200 μm or more is required. However, since the polycrystalline silicon carbide compact has a bias in the growth manner in the thickness direction, when the polycrystalline silicon carbide compact is a plate-like body with a thickness of 200 μm or more, (1) it is likely to cause a bias in the nitrogen concentration in the obtained polycrystalline silicon carbide compact, (2) it cannot reach the desired nitrogen content, and (3) warpage occurs due to a large difference in the particle diameter of the silicon carbide crystals on the first main surface and the particle diameter of the silicon carbide crystals on the second main surface, residual stress, etc. It has also been found.

[0013] The present invention has been made in view of the above circumstances, and the problem to be solved by the present invention is to provide a polycrystalline silicon carbide compact having excellent flatness and a method for producing the same, despite having a low resistivity, a high nitrogen content, and a large thickness.

[0014] As a result of further studies by the present inventors to solve the above problems, it has been found that a polycrystalline silicon carbide compact in which the particle diameter of the silicon carbide crystals is appropriately controlled has excellent flatness despite having a low resistivity, a high nitrogen content, and a large thickness.

[0015] Furthermore, as a result of diligent research by the present inventors, in the initial film formation step by CVD, a mixed gas consisting of a raw material gas, nitrogen gas, and a carrier gas is introduced into the atmosphere inside the CVD furnace at a constant partial pressure of the first mixed gas, and argon gas is introduced into the atmosphere inside the CVD furnace at a constant partial pressure of the first argon gas to form a polycrystalline silicon carbide film on the substrate. Subsequently, in the next step, the mixed gas is introduced into the atmosphere inside the CVD furnace while increasing the partial pressure of the mixed gas from the partial pressure of the first mixed gas to the partial pressure of the second mixed gas at a constant rate, and argon gas is introduced into the atmosphere inside the CVD furnace while decreasing the partial pressure of the argon gas from the partial pressure of the first argon gas to the partial pressure of the second argon gas at a constant rate, thereby forming another polycrystalline silicon carbide film on the polycrystalline silicon carbide film. We have found that a polycrystalline silicon carbide molded body (plate-like body) can be produced by a method in which the partial pressure of the first argon gas is 30 kPa to 100 kPa, and the pressure of the total gas, consisting of a mixed gas of a raw material gas, nitrogen gas, and carrier gas, and argon gas, in the first and second steps is 95 kPa to 106 kPa, thereby achieving a high nitrogen uptake rate in the polycrystalline silicon carbide film and obtaining a polycrystalline silicon carbide molded body with low resistivity.

[0016] In the above manufacturing method, when forming a polycrystalline silicon carbide film by introducing a mixed gas consisting of a raw material gas, nitrogen gas, and a carrier gas, by using argon gas, which is inert at both room temperature and high temperature, together with this mixed gas, it is possible to stably control the partial pressure of the mixed gas and the argon gas even when forming a film at high temperature by the CVD method, and as a result, nitrogen can be stably introduced into the polycrystalline silicon carbide film.

[0017] Furthermore, as a result of diligent research by the present inventors, it has been found that the above manufacturing method makes it possible to homogenize the particle size of silicon carbide crystals on the first main surface of the polycrystalline silicon carbide molded body, the particle size of silicon carbide crystals on the second main surface of the polycrystalline silicon carbide molded body, and the particle size of silicon carbide crystals extending from the first main surface to the second main surface of the polycrystalline silicon carbide molded body. This reduces residual stress and makes it possible to obtain a polycrystalline silicon carbide molded body in which warping is suppressed.

[0018] Based on the above findings, the present invention is as follows: [1a] A polycrystalline silicon carbide molded body, wherein the nitrogen content is greater than 1,000 ppm by mass and less than or equal to 5,000 ppm by mass, the resistivity is 0.0100 Ω・cm or less, and the plate-like body has a thickness of 200 μm to 1,000 μm, the average particle diameter of the silicon carbide crystals on the first main surface of the plate-like body is 6.0 to 25.0 μm, the average particle diameter of the silicon carbide crystals on the second main surface of the plate-like body is 6.0 to 25.0 μm, the average particle diameter of the silicon carbide crystals extending from the first main surface to the second main surface of the plate-like body is 6.0 to 25.0 μm, and the average difference between the particle diameter of the silicon carbide crystals on the first main surface and the particle diameter of the silicon carbide crystals on the second main surface at a position corresponding to the first main surface is 0.1 μm to 1.5 μm. [2a] The polycrystalline silicon carbide molded body according to [1a], wherein the rate of variation is defined as the ratio of the average value of the difference between the particle diameter of silicon carbide crystals on the first main surface and the particle diameter of silicon carbide crystals on the second main surface at a position corresponding to the first main surface to the average particle diameter of silicon carbide crystals extending from the first main surface to the second main surface, and the rate of variation is 0.1% to 10.0%. [3a] The polycrystalline silicon carbide molded body according to [1a], wherein the average value of the difference between the residual stress on the first main surface measured by X-ray diffraction and the residual stress on the second main surface at a position corresponding to the first main surface is 10 to 80 MPa. [4a] The polycrystalline silicon carbide molded body according to any one of [1a] to [3a], wherein the amount of warpage is 5 μm to 50 μm.[5a] A method for producing a polycrystalline silicon carbide molded body according to any one of [1a] to [4a], comprising: a film formation step of introducing a mixed gas consisting of a raw material gas, nitrogen gas and a carrier gas and argon gas into an atmosphere and forming a polycrystalline silicon carbide film on a substrate by a CVD method; and a molding step of forming the polycrystalline silicon carbide film to obtain a polycrystalline silicon carbide molded body, wherein the film formation step of forming the polycrystalline silicon carbide film includes a first step and a second step, in which, with respect to the gas pressure of the entire gas consisting of the mixed gas and the argon gas, the mixed gas is introduced into the atmosphere at a first mixed gas partial pressure and the argon gas is introduced at a first argon gas partial pressure, and a first polycrystalline silicon carbide film is formed on the substrate, and then, In the second step, the partial pressure of the argon gas is decreased at a constant rate from the first partial pressure of the argon gas to the second partial pressure of the argon gas, while the partial pressure of the mixed gas is increased at a constant rate from the first partial pressure of the mixed gas to the second partial pressure of the mixed gas, while the mixed gas and the argon gas are introduced into the atmosphere to form a second silicon carbide film on the first polycrystalline silicon carbide film, wherein the partial pressure of the first argon gas is 30 kPa to 100 kPa, and in the first and second steps, the pressure of the total gas consisting of a mixed gas comprising a raw material gas, nitrogen gas, and carrier gas, and argon gas, is 95 kPa to 106 kPa.

[0019] In other words, the present invention is as follows. Note that the above [1a] to [5a] correspond to the following [1b] to [5b], respectively. [1b] A polycrystalline silicon carbide molded body, wherein the nitrogen content is greater than 1,000 ppm by mass and 5,000 ppm by mass or less, the resistivity is 0.0100 Ω·cm or less, and the thickness is 200 μm to 1,000 μm, the average particle diameter of the silicon carbide crystals on the first main surface of the plate-like body is 6.0 μm to 25.0 μm, the average particle diameter of the silicon carbide crystals on the second main surface of the plate-like body is 6.0 μm to 25.0 μm, the average particle diameter of the silicon carbide crystals extending from the first main surface to the second main surface of the plate-like body is 6.0 μm to 25.0 μm, and the average difference between the particle diameter of the silicon carbide crystals on the first main surface of the plate-like body and the particle diameter of the silicon carbide crystals on the second main surface is 0.1 μm to 1.5 μm. [2b] The polycrystalline silicon carbide molded body according to [1b], wherein the variation rate calculated from the following formula: Variance rate (%) = 100 × (mean value of Δd) / d3 (wherein the formula, the mean value of Δd is the mean value of the difference (μm) between the particle size (μm) of silicon carbide crystals on the first main surface of the plate-like body and the particle size (μm) of silicon carbide crystals on the second main surface, and d3 is the mean particle size of silicon carbide crystals extending from the first main surface to the second main surface of the plate-like body.) is 0.1% to 10.0%. [3b] The polycrystalline silicon carbide molded body according to [1b] or [2b], wherein the mean value of the difference between the residual stress on the first main surface and the residual stress on the second main surface of the plate-like body, measured by X-ray diffraction, is 10 MPa to 80 MPa. [4b] A polycrystalline silicon carbide molded body according to any one of [1b] to [3b], wherein the amount of warpage is 5 μm to 50 μm.[5b] A method for producing a polycrystalline silicon carbide molded body as described in any one of [1b] to [4b] above, comprising the steps of: introducing a mixed gas consisting of a raw material gas, nitrogen gas, and a carrier gas, and argon gas into the atmosphere inside a CVD furnace to form a polycrystalline silicon carbide film on a substrate by a CVD method; and processing the polycrystalline silicon carbide film to obtain a polycrystalline silicon carbide molded body, wherein the step of forming the polycrystalline silicon carbide film comprises a first step and a second step, in which the mixed gas is introduced into the atmosphere inside a CVD furnace at a constant partial pressure of a first mixed gas, and argon gas is introduced into the atmosphere inside a CVD furnace at a constant partial pressure of a first argon gas to form a polycrystalline silicon carbide film on a substrate, A method comprising the following steps: in the second step, the mixed gas is introduced into the atmosphere of the CVD furnace while increasing the partial pressure of the mixed gas from the partial pressure of the first mixed gas to the partial pressure of the second mixed gas at a constant rate, and the argon gas is introduced into the atmosphere of the CVD furnace while decreasing the partial pressure of the argon gas from the partial pressure of the first argon gas to the partial pressure of the second argon gas at a constant rate, thereby forming a further polycrystalline silicon carbide film on the polycrystalline silicon carbide film formed in the first step, wherein the partial pressure of the first argon gas is 30 kPa to 100 kPa, and in the first and second steps, the pressure of the total gas, consisting of a mixed gas composed of a raw material gas, nitrogen gas, and carrier gas, and argon gas, is 95 kPa to 106 kPa.

[0020] According to the present invention, a polycrystalline silicon carbide molded body with excellent flatness can be obtained despite having low resistivity, high nitrogen content, and a large thickness.

[0021] This figure shows an example of a manufacturing apparatus for the polycrystalline silicon carbide molded body of the present invention. This figure shows an example of a measurement position for the particle size of the polycrystalline silicon carbide molded body of the present invention. This figure shows an example of a measurement position for the residual stress of the polycrystalline silicon carbide molded body of the present invention. This figure illustrates the process of forming a polycrystalline silicon carbide film on the polycrystalline silicon carbide molded body of the present invention. This figure shows a radial cross-section of an isotropic graphite substrate on which a polycrystalline silicon carbide film has been formed. This figure illustrates the process of obtaining a polycrystalline silicon carbide molded body from a laminate of an isotropic graphite substrate and a polycrystalline silicon carbide film.

[0022] First, the polycrystalline silicon carbide molded body of the present invention will be described. The polycrystalline silicon carbide molded body of the present invention is a plate-like body having a nitrogen content of more than 1,000 ppm by mass and 5,000 ppm by mass or less, a resistivity of 0.0100 Ω·cm or less, and a thickness of 200 μm to 1,000 μm, wherein the average particle diameter of the silicon carbide crystals on the first main surface of the plate-like body is 6.0 μm to 25.0 μm, the average particle diameter of the silicon carbide crystals on the second main surface of the plate-like body is 6.0 μm to 25.0 μm, the average particle diameter of the silicon carbide crystals extending from the first main surface to the second main surface of the plate-like body is 6.0 μm to 25.0 μm, and the average difference between the particle diameter of the silicon carbide crystals on the first main surface of the plate-like body and the particle diameter of the silicon carbide crystals on the second main surface is 0.1 μm to 1.5 μm.

[0023] The nitrogen content of the polycrystalline silicon carbide molded body (plate-like body) of the present invention is greater than 1,000 ppm by mass and less than or equal to 5,000 ppm by mass. Note that the nitrogen content value is relative to the entire polycrystalline silicon carbide molded body.

[0024] From the viewpoint of low resistivity, the nitrogen content of the polycrystalline silicon carbide molded body is preferably 1200 ppm by mass or more, more preferably 1400 ppm by mass or more, and even more preferably 1600 ppm by mass or more.

[0025] Furthermore, from the viewpoint of ease of controlling the particle size of silicon carbide crystals, the nitrogen content of the polycrystalline silicon carbide molded body is preferably 4800 ppm by mass or less, more preferably 4600 ppm by mass or less, and even more preferably 4400 ppm by mass or less.

[0026] By adjusting the nitrogen content of the polycrystalline silicon carbide molded body of the present invention to within the above range, low resistivity and low warpage can be obtained. In this specification and the claims (hereinafter collectively referred to as "this specification"), the nitrogen content value in the polycrystalline silicon carbide molded body is a value measured and calculated by the following method.

[0027] (Measurement and calculation of nitrogen content) The approximate center portions of the first and second main surfaces of the polycrystalline silicon carbide molded body (plate-like body) are cut out, and the nitrogen content on the first main surface and the nitrogen content on the second main surface are measured once each using an ATOMIKA SIMS 4000. The arithmetic mean of these measurements is taken as the nitrogen content of the polycrystalline silicon carbide molded body.

[0028] In this specification, the main surface of a polycrystalline silicon carbide molded body (plate-like body) means the surface having the largest area of ​​the plate-like body. In this specification, the first main surface and the second main surface of a polycrystalline silicon carbide molded body (plate-like body) generally refer to the front surface and the back surface of the plate-like body. For example, if the first main surface is the front surface, then the second main surface is the other back surface. The reverse is also possible. That is, if the second main surface is the front surface, then the first main surface is the other back surface. Also, for example, the first main surface of a polycrystalline silicon carbide molded body is the main surface formed on the substrate side during manufacturing by the CVD method, and the second main surface of a polycrystalline silicon carbide molded body is the growth surface (the main surface opposite to the first main surface) during manufacturing by the CVD method. The reverse is also possible.

[0029] The silicon carbide crystals constituting the polycrystalline silicon carbide molded body of the present invention are thought to be composed of silicon carbide crystals in which some of the carbon atoms (C) in the silicon carbide crystals are replaced by nitrogen atoms (N), which are n-type dopants. It is believed that the replacement of carbon atoms (C) in silicon carbide with nitrogen atoms (N) increases the number of free electrons, thereby lowering the resistivity of the polycrystalline silicon carbide molded body.

[0030] The resistivity of the polycrystalline silicon carbide molded body (plate-like body) of the present invention is 0.0100 Ω·cm or less. The resistivity of the polycrystalline silicon carbide molded body may be 0.0000 Ω·cm.

[0031] From the viewpoint of ease of manufacturing the polycrystalline silicon carbide molded body, the resistivity is preferably 0.0001 Ω·cm or higher, more preferably 0.0002 Ω·cm or higher, and even more preferably 0.0003 Ω·cm or higher. Since a lower resistivity is preferable, the resistivity is preferably 0.0070 Ω·cm or lower, more preferably 0.0050 Ω·cm or lower, and even more preferably 0.0030 Ω·cm or lower.

[0032] For example, when the polycrystalline silicon carbide molded body of the present invention, which has low resistivity, is used as a component for a plasma etching apparatus, it becomes easier to dissipate static electricity and generate plasma gas uniformly. Furthermore, when a current path is formed to cross the junction surface between the polycrystalline silicon carbide molded body and the single-crystal silicon carbide substrate, using the polycrystalline silicon carbide molded body of the present invention, which has low resistivity, can reduce the potential barrier (contact resistance) at the junction surface and easily improve the responsiveness of the device. In this specification, the resistivity value of the polycrystalline silicon carbide molded body is a value measured and calculated by the following method.

[0033] (Measurement and Calculation of Resistivity) In accordance with JIS K7194, the resistivity of the approximate center of the first main surface and the second main surface of the polycrystalline silicon carbide molded body (plate-like body) is measured once each using the four-probe method with a "Rolestar GP MCP-T610" manufactured by Mitsubishi Chemical Analytech Co., Ltd., and the arithmetic mean of these measurements is taken as the resistivity of the polycrystalline silicon carbide molded body.

[0034] The thickness of the polycrystalline silicon carbide molded body (plate-like body) of the present invention is 200 μm to 1000 μm. When the polycrystalline silicon carbide molded body of the present invention is used for the applications disclosed in the above-mentioned Patent Documents 1 to 4, the thickness is preferably 205 μm or more, more preferably 210 μm or more, and even more preferably 215 μm or more, from the viewpoint of ease of handling and ensuring strength. Furthermore, from the viewpoint of reducing the particle size and warpage of the silicon carbide crystals, the thickness is preferably 990 μm or less, more preferably 985 μm or less, even more preferably 980 μm or less, and particularly preferably 900 μm or less.

[0035] In this specification, the thickness of the polycrystalline silicon carbide molded body (plate-like body) is the arithmetic mean calculated by measuring the distance between the first main surface and the second main surface of the polycrystalline silicon carbide molded body at five locations (see Figure 3) as described in the section below, "Measurement and calculation of the average value of the difference between the residual stress on the first main surface and the residual stress on the second main surface," using a micrometer.

[0036] The average particle size of silicon carbide crystals on the first main surface of the polycrystalline silicon carbide molded body (plate-like body) of the present invention is 6.0 μm to 25.0 μm. From the viewpoint of ease of manufacturing the polycrystalline silicon carbide molded body, the average particle size of silicon carbide crystals on the first main surface is preferably 8.0 μm or more, more preferably 9.0 μm or more, and even more preferably 10.0 μm or more. Furthermore, from the viewpoint of reducing warpage, the average particle size of silicon carbide crystals on the first main surface is preferably 20.0 μm or less, more preferably 19.0 μm or less, and even more preferably 18.0 μm or less.

[0037] The average particle size of silicon carbide crystals on the second main surface of the polycrystalline silicon carbide molded body (plate-like body) of the present invention is 6.0 μm to 25.0 μm. From the viewpoint of ease of manufacturing the polycrystalline silicon carbide molded body, the average particle size of silicon carbide crystals on the second main surface is preferably 8.0 μm or more, more preferably 9.0 μm or more, and even more preferably 10.0 μm or more. Furthermore, from the viewpoint of reducing warpage, the average particle size of silicon carbide crystals on the second main surface is preferably 20.0 μm or less, more preferably 19.0 μm or less, and even more preferably 18.0 μm or less.

[0038] The average particle size of silicon carbide crystals extending from the first main surface to the second main surface of the polycrystalline silicon carbide molded body (plate-like body) of the present invention is 6.0 μm to 25.0 μm. From the viewpoint of ease of manufacturing the polycrystalline silicon carbide molded body, the average particle size of silicon carbide crystals extending from the first main surface to the second main surface is preferably 8.0 μm or more, more preferably 9.0 μm or more, and even more preferably 10.0 μm or more. Furthermore, from the viewpoint of reducing warpage, the average particle size of silicon carbide crystals extending from the first main surface to the second main surface is preferably 20.0 μm or less, more preferably 19.0 μm or less, and even more preferably 18.0 μm or less.

[0039] The average difference between the particle size of silicon carbide crystals on the first main surface and the particle size of silicon carbide crystals on the second main surface of the polycrystalline silicon carbide molded body (plate-like body) of the present invention is 0.1 μm to 1.5 μm. From the viewpoint of ease of manufacturing the crystalline silicon carbide molded body, the average value is preferably 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.3 μm or more. Furthermore, from the viewpoint of reducing warpage, the average value is preferably 1.5 μm or less, more preferably 1.4 μm or less, and even more preferably 1.3 μm or less.

[0040] In the polycrystalline silicon carbide molded body (plate-like body) of the present invention as described above, the particle size of the silicon carbide crystals is made uniform throughout the entire thickness direction from the first main surface to the second main surface. As a result, the difference between the residual stress on the first main surface and the residual stress on the second main surface is reduced, which is thought to reduce the occurrence of warping.

[0041] In the polycrystalline silicon carbide molded body of the present invention, it is preferable that the variation rate calculated from the following formula: Variance rate (%) = 100 × (average value of Δd) / d3 (wherein the formula, the average value of Δd is the average value (μm) of the difference between the particle diameter (μm) of silicon carbide crystals on the first main surface of the polycrystalline silicon carbide molded body (plate-like body) and the particle diameter of silicon carbide crystals on the second main surface, and d3 is the average particle diameter of silicon carbide crystals extending from the first main surface to the second main surface of the polycrystalline silicon carbide molded body (plate-like body)) is 0.1% to 10.0%.

[0042] From the viewpoint of ease of manufacturing the polycrystalline silicon carbide molded body, the above fluctuation rate is preferably 0.2% or more, more preferably 0.3% or more, and even more preferably 0.4% or more. Furthermore, from the viewpoint of reducing the amount of warping, the above fluctuation rate is preferably 8.0% or less, more preferably 7.0% or less, and even more preferably 6.0% or less.

[0043] By controlling the above fluctuation rate of the polycrystalline silicon carbide molded article of the present invention within the above range, the difference in residual stress between the first main surface and the second main surface can be reduced, thereby suitably reducing warpage.

[0044] In this specification, the following values ​​are measured and calculated by the following methods: (1) the average particle diameter of silicon carbide crystals on the first main surface of the polycrystalline silicon carbide molded body (plate-like body) (sometimes referred to as "d1" in this specification), (2) the average particle diameter of silicon carbide crystals on the second main surface of the polycrystalline silicon carbide molded body (plate-like body) (sometimes referred to as "d2" in this specification), (3) the average particle diameter of silicon carbide crystals extending from the first main surface to the second main surface of the polycrystalline silicon carbide molded body (plate-like body) (sometimes referred to as "d3" in this specification), and (4) the average value of the difference between the particle diameter of silicon carbide crystals on the first main surface and the particle diameter of silicon carbide crystals on the second main surface of the polycrystalline silicon carbide molded body (plate-like body) (sometimes referred to as "average value of Δd" in this specification).

[0045] (Measurement and calculation of the average values ​​of d1, d2, d3, and Δd) For the first main surface, the second main surface, and the surface approximately in the center of the polycrystalline silicon carbide molded body (plate-like body) when the polycrystalline silicon carbide molded body is ground in the thickness direction (hereinafter sometimes abbreviated as "approximately central surface"), a crystal orientation map with respect to the direction normal to the main surface of the polycrystalline silicon carbide molded body is obtained by electron beam backscatter diffraction (EBSD method). Details of the measurement conditions are as follows. (Measurement conditions) Pretreatment: Chemical mechanical polishing Measurement device: FE-SEM (JEOL Ltd. "JSM-7900F") EBSD (OXFORD Corporation "AZtecHKL") Image analysis software: AZtec Crystal Measurement voltage: 20kV Measurement tilt angle: 70° Measurement magnification: 100x Measurement interval: 1.4μm Crystal system to be evaluated: 3C type SiC (space group 216) Threshold: 10°

[0046] Using the crystal orientation map obtained by the above method, the average cross-sectional area of ​​each silicon carbide crystal particle is calculated by the area fraction method for the entire field of view (800 μm × 600 μm) at each observation position on the first and second main surfaces of the polycrystalline silicon carbide molded body (plate-like body). The sum of the values ​​obtained by multiplying the area of ​​each silicon carbide crystal particle by the ratio of the area of ​​each silicon carbide crystal particle to the total area of ​​each observation field of view is calculated, and this is taken as the particle diameter of the silicon carbide crystal at each observation position. Specifically, the particle diameter of the silicon carbide crystal at each observation position is calculated by analyzing the data using image analysis software attached to the EBSD instrument.

[0047] On the first and second main surfaces, measurements are taken at three observation positions to obtain a crystal orientation map. For example, if the polycrystalline silicon carbide molded body is a plate-like body having a disc shape with a diameter of 150 mm (hereinafter sometimes abbreviated as "plate-like body 1"), the observation positions are (1) the center, (2) 30 mm radially from the center, and (3) 65 mm from the center (Figure 2).

[0048] The particle size of the silicon carbide crystals on the first main surface obtained at the positions (1) to (3) above is d1, respectively. １, d1 ２ and d1 ３ are used, and the particle diameters of the silicon carbide crystals on the second main surface obtained at the positions of (1) to (3) above are made d2 １ , d2 ２ and d2 ３ respectively. In FIG. 2, the "first main surface" and the "second main surface" are described as the "first surface" and the "second surface" respectively, and "d1 １ to d1 ３ " and "d2 １ to d2 ３ " are described as "d11 to d13" and "d21 to d23" respectively.

[0049] The arithmetic mean value of d1 １ , d1 ２ and d1 ３ calculated as described above is taken as the "average particle diameter (d1) of the silicon carbide crystals on the first main surface", and the arithmetic mean value of d2 １ , d2 ２ and d2 ３ is taken as the "average particle diameter (d2) of the silicon carbide crystals on the second main surface".

[0050] If the particle diameters of the silicon carbide crystals on the first main surface, the second main surface, and the surface of the substantially central part are all of the same degree, it can be said that the particle diameters of the silicon carbide crystals are substantially uniform regardless of where the polycrystalline silicon carbide compact (or polycrystalline silicon carbide film) is measured. Therefore, the arithmetic mean value ((d1 + d2) / 2) of the "average particle diameter (d1) of the silicon carbide crystals on the first main surface" and the "average particle diameter (d2) of the silicon carbide crystals on the second main surface" is taken as the "average particle diameter (d3) of the silicon carbide crystals from the first main surface to the second main surface".

[0051] Further, (1) the absolute value of the difference between d1 １ and d2 １ (|d2 １ - d1 １ |), (2) the absolute value of the difference between d1 ２ and d2 ２ (|d2 ２ - d1 ２ |), and (3) the absolute value of the difference between d1 ３ and d2 ３The absolute value of the difference (|d²) ３ -d1 ３ The following are calculated for each of the above, and their arithmetic mean is defined as "the average difference (Δd) between the particle size of silicon carbide crystals on the first main surface and the particle size of silicon carbide crystals on the second main surface."

[0052] If the polycrystalline silicon carbide molded body is a plate-like body having a disc shape with a diameter of not 150 mm (sometimes abbreviated as "plate-like body 2" in this specification), then at the three locations of plate-like body 2 that exist in the same proportion as the three locations of plate-like body 1 (Figure 2), d1 １ ~d1 ３ and d2 １ ~d2 ３ The following are calculated, and d1, d2, etc. are calculated from these.

[0053] When the polycrystalline silicon carbide molded body is a rectangular plate-like body (sometimes abbreviated as "plate-like body 3" in this specification), d1 is present at three locations on plate-like body 3 that are present in the same proportion as the three locations on plate-like body 1 (Figure 2). １ ~d1 ３ and d2 １ ~d2 ３ The following are calculated, and d1, d2, etc. are calculated from these.

[0054] The average difference between the residual stress on the first main surface and the residual stress on the second main surface of the polycrystalline silicon carbide molded body (plate-like body) of the present invention, as measured by X-ray diffraction, is preferably 10 MPa to 80 MPa.

[0055] The residual stresses on the first main surface and the second main surface of the polycrystalline silicon carbide molded body (plate-like body) of the present invention, as measured by X-ray diffraction, are thought to be due to the size and orientation of the silicon carbide crystal grains on the first and second main surfaces, respectively.

[0056] From the viewpoint of ease of manufacturing the polycrystalline silicon carbide molded body, the average value of the difference between the residual stress on the first main surface and the residual stress on the second main surface is preferably 20 MPa or more, more preferably 23 MPa or more, and even more preferably 25 MPa or more. Furthermore, from the viewpoint of reducing warpage, the average value of the difference between the residual stress on the first main surface and the residual stress on the second main surface is preferably 70 MPa or less, more preferably 60 MPa or less, and even more preferably 50 MPa or less.

[0057] By controlling the average value of the difference between the residual stress on the first main surface and the residual stress on the second main surface of the polycrystalline silicon carbide molded body (plate-like body) of the present invention, measured by X-ray diffraction, to within the above range, warping can be further suppressed, and a polycrystalline silicon carbide molded body with excellent flatness can be obtained.

[0058] In this specification, the average value of the difference between the residual stress on the first main surface and the residual stress on the second main surface of a polycrystalline silicon carbide molded body (plate-like body), measured by X-ray diffraction, is the arithmetic mean value measured and calculated by the following X-ray diffraction method: (A) Calculate the residual stress at five locations on the first main surface; (B) Calculate the residual stress at five locations on the second main surface corresponding to the five locations mentioned above; (C) Calculate the absolute value of the difference between the residual stress on the first main surface and the residual stress on the second main surface at the corresponding positions obtained in (A) and (B); and (D) Calculate the arithmetic mean value from the absolute values ​​of the differences at the five locations obtained in (C), and this is referred to as the "average value of the difference between the residual stress on the first main surface and the residual stress on the second main surface of a polycrystalline silicon carbide molded body (plate-like body), measured by X-ray diffraction."

[0059] For example, if the polycrystalline silicon carbide molded body is a plate-like body having a disc shape with a diameter of 150 mm (hereinafter sometimes abbreviated as "plate-like body 1"), the "five locations on the main surface" in (A) above are (1) 65 mm to the left radially from the center, (2) 30 mm to the left radially from the center, (3) the center, (4) 30 mm to the right radially from the center, and (5) 65 mm to the right radially from the center (Figure 3). The "five locations on the second main surface corresponding to the five locations" in (B) above are the locations where, when the polycrystalline silicon carbide molded body is placed so that the first main surface is in contact with a horizontal surface, perpendicular lines are drawn to the measurement positions of residual stress on the first main surface at the five locations (i.e., (1) to (5) above), and these perpendicular lines intersect with the second main surface (Figure 3). In Figure 3, the "first main surface" and the "second main surface" are referred to as "first surface" and "second surface," respectively.

[0060] If the polycrystalline silicon carbide molded body is a plate-like body having a disc shape with a diameter of 150 mm or less (hereinafter abbreviated as "plate-like body 2"), the "residual stress on the first main surface" and the "residual stress on the second main surface" are measured and calculated at five locations on plate-like body 2 that exist in the same proportion as the five locations on plate-like body 1 (Figure 3), and the "average value of the difference between the residual stress on the first main surface and the residual stress on the second main surface, measured by X-ray diffraction" is calculated.

[0061] When the polycrystalline silicon carbide molded body is a rectangular plate-like body (hereinafter abbreviated as "plate-like body 3"), the "residual stress on the first main surface" and the "residual stress on the second main surface" are measured and calculated at five locations on plate-like body 3 that exist in the same proportion as the five locations on plate-like body 1 (Figure 3), and the "average value of the difference between the residual stress on the first main surface and the residual stress on the second main surface, measured by X-ray diffraction" is calculated.

[0062] (Measurement and calculation of residual stress) Using the Rigaku SmartLab fully automated multi-purpose X-ray diffractometer under the following conditions, (i) measurement by X-ray diffraction and (ii) sin ２The residual stresses on the first and second main surfaces of the polycrystalline silicon carbide molded body are calculated using the ψ method. Under the following conditions, ψ represents the angle between the diffraction plane normal direction and the sample plane normal direction. X-ray: Cu tube, Kα, 40kV, 20mA Diffraction plane 2θ: 3C-SiC(511) plane Unstrained angle: 133.60 degrees Scanning range: 129.20 degrees to 138.00 degrees Counting time: 270 seconds / ψ Number of ψ angle measurement points: 7 points Young's modulus (E) of polycrystalline silicon carbide molded body: 450,000 MPa Poisson's ratio (v): 0.16 Measurement location (See Figure 3 (when the polycrystalline silicon carbide molded body is a plate-like body with a disc shape of 150 mm in diameter))

[0063] When the polycrystalline silicon carbide molded body is a plate-like body having a disc shape with a diameter of 150 mm (Figure 3), the residual stress (RS1) on the first main surface at the five locations mentioned above is １ ~RS1 ５ ) and residual stress on the second main surface (RS2 １ ~RS2 ５ The absolute value of the difference between ) and |RS² １ -RS1 １ |,|RS2 ２ -RS1 ２ |,|RS2 ３ -RS1 ３ |,|RS2 ４ -RS1 ４ |, and |RS2 ５ -RS1 ５ | is calculated, and the arithmetic mean of these is defined as "the average difference between the residual stress on the first main surface and the residual stress on the second main surface of the polycrystalline silicon carbide molded body (plate-like body), measured by X-ray diffraction." Note that in Figure 3, "RS1 １ ~RS1 ５ " and "RS2 １ ~RS2 ５ These will be referred to as "RS11-RS15" and "RS21-RS25," respectively.

[0064] Residual stress at the five locations on the first main surface (RS1 １ ~RS1 ５From this, the arithmetic mean of residual stress on the first main surface (hereinafter sometimes abbreviated as "mean value of RS1") and the standard deviation of residual stress on the first main surface (hereinafter sometimes abbreviated as "σRS1") can be calculated. Using the mean value of RS1 and σRS1, the coefficient of variation of residual stress on the first main surface (hereinafter sometimes abbreviated as "CVRS1") can be calculated by the following formula (the units of "σRS1" and "mean value of RS1" in the following formula are both "MPa"): CVRS1 (%) = 100 × (σRS1 / mean value of RS1)

[0065] Similarly, the residual stress at the five locations on the second main surface (RS2 １ ~RS2 ５ From this, the arithmetic mean of residual stress on the second main surface (hereinafter sometimes abbreviated as "mean value of RS2") and the standard deviation of residual stress on the second main surface (hereinafter sometimes abbreviated as "σRS2") can be calculated. Using the mean value of RS2 and σRS2, the coefficient of variation of residual stress on the second main surface (hereinafter sometimes abbreviated as "CVRS2") can be calculated by the following formula (the units of "σRS2" and "mean value of RS2" in the following formula are both "MPa"): CVRS2 (%) = 100 × (σRS2 / mean value of RS2)

[0066] CVRS1 and CVRS2 are each preferably 2.0% to 20.0%, more preferably 3.0% to 19.0%, and even more preferably 4.0% to 18.0%. The values ​​of CVRS1 and CVRS2 may be the same or different.

[0067] By adjusting CVRS1 and CVRS2 within the above range, a polycrystalline silicon carbide molded body with even greater flatness can be obtained.

[0068] The curvature of the polycrystalline silicon carbide molded body (plate-like body) of the present invention is preferably 5 μm to 50 μm. From the viewpoint of ease of manufacturing the polycrystalline silicon carbide molded body, the curvature is preferably 6 μm or more, more preferably 7 μm or more, and even more preferably 8 μm or more. Since a smaller curvature is preferable, the curvature is preferably 49 μm or less, more preferably 48 μm or less, and even more preferably 47 μm or less.

[0069] The polycrystalline silicon carbide molded body of the present invention exhibits low warping and excellent flatness despite having a high nitrogen content (over 1000 ppm by mass) and a large thickness (200 μm or more).

[0070] In this specification, the value of the warpage of the polycrystalline silicon carbide molded body is the value measured using an optical interference warpage measuring device (for example, the "FlatMaster 200XRA-Industrial" manufactured by Corning Tropel).

[0071] The silicon carbide in the polycrystalline silicon carbide molded body of the present invention adopts a polycrystalline crystalline form. Examples of such crystalline forms include the 3C type, 2H type, 4H type, 15R type, and others, which are polytypes (crystalline polymorphs) of SiC crystals. In this specification, the polycrystalline form of the silicon carbide molded body can be determined from the X-ray diffraction spectrum, and the content ratio of each polytype in the polycrystalline silicon carbide molded body can be calculated by the integrated intensity ratio of the main peaks obtained by X-ray diffraction.

[0072] The polycrystalline silicon carbide molded body of the present invention is a plate-like body. Its shape can be, for example, a disc shape, a flat plate shape, etc. When the polycrystalline silicon carbide molded body of the present invention has a disc shape, its diameter is preferably 100 mm to 360 mm, more preferably 125 mm to 340 mm, and even more preferably 130 mm to 320 mm. When the polycrystalline silicon carbide molded body of the present invention has a disc shape, its specific diameter can be, for example, 130 mm, 150 mm, 200 mm, or 300 mm, depending on its application.

[0073] The polycrystalline silicon carbide molded body of the present invention can be suitably manufactured by the manufacturing method of the present invention described later.

[0074] The polycrystalline silicon carbide molded body of the present invention can be suitably used in applications requiring high flatness and low resistivity. For example, the polycrystalline silicon carbide molded body of the present invention can be used as an edge ring, electrode plate, heater, etc., as a component for plasma etching equipment during semiconductor manufacturing. Furthermore, the polycrystalline silicon carbide molded body of the present invention can be used as a dummy wafer as a component for semiconductor heat treatment equipment during semiconductor manufacturing. When the polycrystalline silicon carbide molded body of the present invention is used as a dummy wafer, it is preferable that the polycrystalline silicon carbide molded body of the present invention has a thickness of, for example, about 300 μm to 1000 μm.

[0075] The polycrystalline silicon carbide molded body of the present invention exhibits low warping and excellent flatness despite having a high nitrogen content, low resistivity, and large thickness.

[0076] Next, a method for producing the polycrystalline silicon carbide molded body of the present invention (hereinafter sometimes abbreviated as "the manufacturing method of the present invention") will be described.

[0077] The manufacturing method of the present invention includes a step of forming a polycrystalline silicon carbide film on a substrate by CVD by introducing a mixed gas consisting of a raw material gas, nitrogen gas, and a carrier gas, and argon gas into the atmosphere inside a CVD furnace (hereinafter sometimes abbreviated as "film formation step"), and a step of processing the polycrystalline silicon carbide film to obtain a polycrystalline silicon carbide molded body (hereinafter sometimes abbreviated as "processing step"), wherein the film formation step includes a first step and a second step, in which the mixed gas is introduced into the atmosphere inside a CVD furnace at a constant partial pressure of a first mixed gas, and argon gas is introduced into the atmosphere inside a CVD furnace at a constant partial pressure of a first argon gas to form a polycrystalline silicon carbide film on a substrate, In the second step, the mixed gas is introduced into the atmosphere inside the CVD furnace while increasing the partial pressure of the mixed gas from the partial pressure of the first mixed gas to the partial pressure of the second mixed gas at a constant rate, and the argon gas is introduced into the atmosphere inside the CVD furnace while decreasing the partial pressure of the argon gas from the partial pressure of the first argon gas to the partial pressure of the second argon gas at a constant rate, thereby forming a further polycrystalline silicon carbide film on the polycrystalline silicon carbide film formed in the first step, characterized in that the partial pressure of the first argon gas is 30 kPa to 100 kPa, and in the first and second steps, the pressure of the total gas, consisting of a mixed gas composed of a raw material gas, nitrogen gas, and carrier gas, and argon gas, is 95 kPa to 106 kPa.

[0078] In the film deposition process, a mixed gas consisting of a raw material gas, nitrogen gas, and a carrier gas is used. The raw material gas is not particularly limited as long as it is a gas that supplies Si (silicon) and C (carbon), and may be a one-component gas (a gas containing both Si and C in its molecule) or a two-component gas (a mixture of a component gas containing Si in its molecule and a component gas containing C in its molecule). Furthermore, one-component gases may be used alone or in combination of two or more. Also, one-component gases and two-component gases may be used in combination. Furthermore, in a two-component gas, one component gas containing Si in its molecule may be used alone or in combination of two or more. Furthermore, in a two-component gas, one component gas containing C in its molecule may be used alone or in combination of two or more.

[0079] Examples of one-component gases include methyltrichlorosilane (MTS), trichlorophenylsilane, dichloromethylsilane, dichlorodimethylsilane, and chlorotrimethylsilane. Examples of two-component gases include mixtures of silane gas and hydrocarbon gas. Examples of silane gases include trichlorosilane and monosilane. Only one type of silane gas may be used, or two or more types may be used in combination.

[0080] The carrier gas used in the film deposition process is not particularly limited, but hydrogen gas is one example.

[0081] In the film deposition process, a mixed gas obtained by mixing the source gas, nitrogen gas, and carrier gas is introduced into the atmosphere inside the CVD furnace. For this mixing, a mixer can be used, for example.

[0082] In the film deposition process, argon gas is introduced into the atmosphere inside the CVD furnace. In this film deposition process, the nitrogen content and particle size of the silicon carbide crystals in the resulting polycrystalline silicon carbide molded body can be adjusted by adjusting the supply amounts of the aforementioned mixed gas (i.e., a mixture of raw material gas, nitrogen gas, and carrier gas) and argon gas.

[0083] Figure 1 shows an example of a manufacturing apparatus for a polycrystalline silicon carbide molded body according to the present invention. The manufacturing apparatus shown in Figure 1 is equipped with a CVD furnace 1 and a mixer 3. Carrier gas C, raw gas R which is the source of silicon carbide, and nitrogen gas N are supplied to the mixer 3 and mixed to produce a mixed gas. The mixed gas is supplied from the mixer 3 to the CVD furnace 1, in which a plurality of isotropic graphite substrates 2 are arranged. The shape of the isotropic graphite substrate 2 can be, for example, a disc shape. Argon gas Ar is supplied to the CVD furnace 1 along with the mixed gas.

[0084] The film deposition process may optionally include a third step, as described below, in addition to the first and second steps. As shown in Figure 3, the film deposition process is carried out sequentially in the first, second, and third (optional) steps.

[0085] The mixing ratios of the raw material gas, nitrogen gas, and carrier gas in the mixed gas supplied in the first, second, and third (optional) steps may differ, but from the viewpoint of controlling the amount of nitrogen taken up in the polycrystalline silicon carbide film and the particle size of the silicon carbide crystals, it is preferable that the mixing ratios remain constant.

[0086] In the first, second, and third (optional) steps, independently, the ratio of the partial pressure of the raw material gas to the partial pressure of the mixed gas (i.e., a mixture of raw material gas, nitrogen gas, and carrier gas) (partial pressure of raw material gas / partial pressure of mixed gas) is preferably 0.01 to 0.10, more preferably 0.02 to 0.09, and even more preferably 0.03 to 0.08.

[0087] In the first, second, and third (optional) steps, independently, the ratio of the partial pressure of nitrogen gas to the partial pressure of the mixed gas (i.e., a mixture of raw material gas, nitrogen gas, and carrier gas) (partial pressure of nitrogen gas / partial pressure of mixed gas) is preferably 0.10 to 0.50, more preferably 0.15 to 0.45, and even more preferably 0.20 to 0.40.

[0088] In the first, second, and third (optional) steps, independently, the ratio of the partial pressure of the carrier gas to the partial pressure of the mixed gas (i.e., a mixture of raw material gas, nitrogen gas, and carrier gas) (partial pressure of carrier gas / partial pressure of mixed gas) is preferably 0.50 to 0.80, more preferably 0.55 to 0.75, and even more preferably 0.60 to 0.70.

[0089] In the first, second, and third (optional) steps, the atmospheric pressure inside the CVD furnace (i.e., the pressure of the total gas consisting of the mixed gas and argon gas) must be 95 kPa to 106 kPa. The pressure is preferably 96 kPa to 105 kPa, and more preferably 97 kPa to 104 kPa.

[0090] In the first step, a mixed gas is introduced into the atmosphere inside the CVD furnace at a constant partial pressure of a first mixed gas, and argon gas is introduced into the atmosphere inside the CVD furnace at a constant partial pressure of a first argon gas to form a polycrystalline silicon carbide film on the substrate.

[0091] Generally, in a mixed gas A consisting of gas 1 and gas 2, the partial pressure of gas 1 refers to the pressure when gas 1 occupies the same volume as mixed gas A on its own. The same applies to mixed gases with three or more components (for example, mixed gas B consisting of gas 1, gas 2, and gas 3). Also, according to Dalton's law of partial pressures, "pressure of mixed gas A" = "partial pressure of gas 1 + partial pressure of gas 2". Therefore, "pressure (partial pressure) of a mixed gas consisting of raw material gas, nitrogen gas, and carrier gas" = "partial pressure of raw material gas + partial pressure of nitrogen gas + partial pressure of carrier gas". Furthermore, "pressure of the total gas consisting of the mixed gas and argon gas" = "partial pressure of mixed gas + partial pressure of argon gas".

[0092] The partial pressure of the first mixed gas is preferably 5 kPa to 70 kPa, more preferably 10 kPa to 50 kPa, and even more preferably 15 kPa to 40 kPa.

[0093] The partial pressure of the first argon gas must be between 30 kPa and 100 kPa. Preferably, the partial pressure is between 40 kPa and 90 kPa, and more preferably between 50 kPa and 85 kPa.

[0094] The ratio of the partial pressure of the first argon gas to the pressure of the total gas consisting of the mixed gas and argon gas in the first step (partial pressure of the first argon gas / total gas pressure) is preferably 0.300 to 1.000, more preferably 0.400 to 0.900, and even more preferably 0.500 to 0.800.

[0095] The time t1 of the first step is not particularly limited, but is preferably more than 0% and 15% or less, more preferably 2% or more and 12% or less, and even more preferably 3% or more and 10% or less, relative to the film formation time T (i.e., the sum of the time t1 of the first step, the time t2 of the second step, and the time t3 of the third step (optional step)).

[0096] In the first step, a polycrystalline silicon carbide film is formed on the substrate. When manufacturing using the manufacturing apparatus shown in Figure 1, a mixed gas and argon gas are supplied to the atmosphere inside the CVD furnace 1, and a polycrystalline silicon carbide film is formed on each isotropic graphite substrate 2 by the CVD method. In addition, nitrogen from the nitrogen-containing gas in the mixed gas is doped into the polycrystalline silicon carbide film. The exhaust gas Ex discharged after the reaction is sent to an exhaust gas treatment device (not shown).

[0097] In the second step following the first step, the mixed gas is introduced into the atmosphere inside the CVD furnace while increasing the partial pressure of the mixed gas from the partial pressure of the first mixed gas to the partial pressure of the second mixed gas at a constant rate, and the argon gas is introduced into the atmosphere inside the CVD furnace while decreasing the partial pressure of the argon gas from the partial pressure of the first argon gas to the partial pressure of the second argon gas at a constant rate, thereby forming a further polycrystalline silicon carbide film on the polycrystalline silicon carbide film formed in the first step.

[0098] The partial pressure of the second mixed gas is preferably 5.0 kPa to 101.3 kPa, more preferably 10.0 kPa to 90.0 kPa, and even more preferably 20.0 kPa to 80.0 kPa.

[0099] The partial pressure of the second argon gas is preferably 0.0 to 100.0 kPa, more preferably 0.5 kPa to 90.0 kPa, and even more preferably 1.0 kPa to 80.0 kPa.

[0100] At the end of the second step, the ratio of the partial pressure of the second argon gas to the pressure of the total gas, which consists of the mixed gas and argon gas (partial pressure of the second argon gas / total gas pressure), is preferably 0 to 1.000, more preferably 0.300 to 0.900, and even more preferably 0.500 to 0.800. A ratio of 0 means that the partial pressure of the second argon gas is 0.

[0101] In the second step, as shown in Figure 4, the partial pressure of the mixed gas is increased at a constant rate from the partial pressure of the first mixed gas to the partial pressure of the second mixed gas, and the partial pressure of the argon gas is decreased at a constant rate from the partial pressure of the first argon gas to the partial pressure of the second argon gas. In the second step, while changing the partial pressure of the mixed gas and the argon gas at a constant rate in this manner, the mixed gas and the argon gas are introduced into the atmosphere inside the CVD furnace to form another polycrystalline silicon carbide film on top of the polycrystalline silicon carbide film formed in the first step.

[0102] The ratio of the partial pressure of the first argon gas to the partial pressure of the nitrogen gas at the start of the first and second steps (partial pressure of the first argon gas / partial pressure of nitrogen gas) is preferably 1.0 or higher, more preferably 3.0 or higher, and even more preferably 5.0 or higher.

[0103] The ratio of the partial pressure of the first argon gas to the partial pressure of the nitrogen gas (partial pressure of the first argon gas / partial pressure of nitrogen gas) at the start of the first and second steps is not particularly limited, but is preferably 50.0 or less, more preferably 40.0 or less, and even more preferably 30.0 or less.

[0104] By adjusting the ratio of the partial pressure of the first argon gas to the partial pressure of the nitrogen gas at the start of the first and second steps so that it falls within the above range, the polycrystalline silicon carbide molded body of the present invention can be easily manufactured.

[0105] The time t2 of the second step is not particularly limited, but is preferably 70% or more and less than 100% of the film formation time T (i.e., the sum of the time t1 of the first step, the time t2 of the second step, and the time t3 of the third step (optional step)), more preferably 76% or more and 96%, and even more preferably 80% or more and 94%.

[0106] In the second step, a polycrystalline silicon carbide film is formed on top of the polycrystalline silicon carbide film formed in the first step. When manufacturing using the production apparatus shown in Figure 1, a mixed gas and argon gas are supplied to the atmosphere of the CVD furnace 1, and a polycrystalline silicon carbide film is formed on top of the polycrystalline silicon carbide film formed in the first step by the CVD method. In addition, nitrogen derived from the nitrogen gas in the mixed gas is doped into the polycrystalline silicon carbide film. The exhaust gas Ex discharged after the reaction is sent to an exhaust gas treatment device (not shown).

[0107] As described above, when polycrystalline silicon carbide molded bodies are manufactured by the CVD method, if the nitrogen content in the polycrystalline silicon carbide molded body exceeds 1000 ppm by mass, the silicon carbide crystals tend to grow larger due to nucleation. As a result, the difference between the particle size of silicon carbide crystals on the first main surface and the particle size of silicon carbide crystals on the second main surface becomes significant, and the residual stress and warpage of the resulting polycrystalline silicon carbide molded body increase.

[0108] In contrast, in the manufacturing method of the present invention, as described above, the partial pressure of the first argon gas at the start of the first and second steps is set to 30 kPa to 100 kPa, and in the second step, the partial pressure of the mixed gas and the partial pressure of the argon gas are changed at a constant rate while forming a polycrystalline silicon carbide film. This makes it possible to homogenize the particle size of the silicon carbide crystals and reduce the residual stress and warpage of the resulting polycrystalline silicon carbide molded body.

[0109] In other words, in the manufacturing method of the present invention, the partial pressure of the first argon gas at the start of the first and second steps is set to 30 kPa to 100 kPa, and in the second step, the partial pressure of the mixed gas (i.e., a mixture of raw material gas, nitrogen gas, and carrier gas) is increased by a constant rate, thereby increasing the amount of nitrogen incorporated into the resulting polycrystalline silicon carbide film by a constant rate, achieving a high nitrogen content, and as a result, a polycrystalline silicon carbide film with low resistivity can be obtained.

[0110] Furthermore, the manufacturing method of the present invention makes it possible to achieve uniformity in the particle size of silicon carbide crystals by processing as described above. As a result, residual stress is reduced, and a polycrystalline silicon carbide molded body with less warping can be obtained.

[0111] In the manufacturing method of the present invention, after the second step, as a third step, the mixed gas may be introduced into the atmosphere of the CVD furnace at a constant partial pressure of the second mixed gas, and the argon gas may be introduced into the atmosphere of the CVD furnace at a constant partial pressure of the second argon gas, thereby forming a further polycrystalline silicon carbide film on the polycrystalline silicon carbide film formed in the second step. However, the third step is an optional step and may not be performed.

[0112] In the third step, the partial pressure of the second mixed gas is preferably 80.0 kPa to 101.3 kPa, more preferably 90.0 kPa to 100.8 kPa, and even more preferably 95.0 kPa to 100.3 kPa.

[0113] In the third step, the partial pressure of the second argon gas is preferably 0 to 1.0 kPa, more preferably 0 to 0.5 kPa, and even more preferably 0 to 0.1 kPa. A partial pressure of 0 for the second argon gas means that no argon gas is supplied in the third step.

[0114] In the third step, the ratio of the partial pressure of the second argon gas to the pressure of the total gas, which consists of the mixed gas and argon gas (partial pressure of the second argon gas / total gas pressure), is preferably 0 to 0.010, more preferably 0 to 0.008, and even more preferably 0.000 to 0.006. A ratio of 0 means that the partial pressure of the second argon gas is 0, i.e., no argon gas is supplied in the third step.

[0115] The time t3 of the third step is not particularly limited, but is preferably 0 to 15%, more preferably 2% to 12%, and even more preferably 3% to 10% of the film formation time T (i.e., the sum of the time t1 of the first step, the time t2 of the second step, and the time t3 of the third step (optional step)).

[0116] In the manufacturing method of the present invention, the film formation time T (i.e., the sum of the time t1 of the first step, the time t2 of the second step, and the time t3 of the third step (optional step)) is not particularly limited, but is preferably 2 to 180 hours, more preferably 30 to 150 hours, and even more preferably 40 to 100 hours.

[0117] In the first, second, and third (optional) steps, the reaction temperature of the gas in the CVD furnace is preferably 1100°C to 1900°C, more preferably 1200°C to 1700°C, and even more preferably 1400°C to 1600°C.

[0118] In the manufacturing method of the present invention, a polycrystalline silicon carbide molded body is obtained by processing the polycrystalline silicon carbide film obtained in the film formation process. The specific processing steps and methods are described below.

[0119] A laminate of isotropic graphite substrate 2 and polycrystalline silicon carbide film is removed from the CVD furnace 1 of the manufacturing apparatus shown in Figure 1.

[0120] Figure 5 shows a radial cross-section of an isotropic graphite substrate 2 having a center line O-O', on which a polycrystalline silicon carbide film 4 is formed. Here, the polycrystalline silicon carbide film 4 is formed on the isotropic graphite substrate 2 so as to cover its entire surface.

[0121] To extract the desired polycrystalline silicon carbide molded body from the isotropic graphite substrate 2 on which the polycrystalline silicon carbide film 4 is formed, for example, the outer periphery is first processed. Specifically, along the break line A-A' shown in Figure 5, only the outer periphery of the isotropic graphite substrate 2 on which the polycrystalline silicon carbide film 4 is formed is removed.

[0122] Next, the isotropic graphite substrate 2, on which the polycrystalline silicon carbide film 4 is formed, is cut in two in the thickness direction along the line that divides the thickness of the isotropic graphite substrate 2 equally (i.e., the break line B-B' shown in Figure 5).

[0123] As a result, a laminate of isotropic graphite substrate 2 and polycrystalline silicon carbide film 4 is obtained, as shown on the left of Figure 6. Furthermore, only the isotropic graphite substrate 2 is removed from the laminate by oxidation, shot blasting, etc., to obtain the polycrystalline silicon carbide film 4, as shown in the center of Figure 6. Subsequently, the exposed surface of the polycrystalline silicon carbide film 4 is ground by grinding, etc. As a result, the desired polycrystalline silicon carbide molded body 10 is obtained, as shown on the right of Figure 6.

[0124] According to the present invention, a polycrystalline silicon carbide molded body with excellent flatness can be obtained despite having low resistivity, high nitrogen content, and a large thickness.

[0125] Next, the present invention will be described in more detail with reference to examples, but these are merely illustrative and not intended to limit the present invention.

[0126] (Example 1) An isotropic graphite substrate with a diameter of 160 mm and a thickness of 5 mm was placed inside a CVD furnace. Methyltrichlorosilane (MTS) gas (raw material gas) and nitrogen (N) were added to the atmosphere inside the CVD furnace. ２ ) gas, and hydrogen (H ２ A mixed gas consisting of a carrier gas and argon (Ar) gas was introduced, and a polycrystalline silicon carbide film was formed on an isotropic graphite substrate by heating at 1410°C.

[0127] The process was divided into three stages: the first 1.6 hours from the start of film deposition, the second 76.8 hours from the end of the first stage, and the third 1.6 hours from the end of the second stage. Throughout all stages, the pressure of the total gas, consisting of the mixed gas (i.e., a mixture of raw material gas, nitrogen gas, and carrier gas) and argon gas, was controlled to 101.3 kPa.

[0128] Throughout the entire process, the proportions of methyltrichlorosilane, nitrogen, and hydrogen in the mixed gas were kept constant (partial pressure ratio: methyltrichlorosilane:nitrogen:hydrogen = 8.1:100.0:51.8).

[0129] (First step) The partial pressure of the first mixed gas was kept constant at 20.2 kPa, and the partial pressure of the first argon gas was kept constant at 81.1 kPa.

[0130] (Second step) While maintaining the overall gas pressure of the mixed gas (i.e., a mixture of raw material gas, nitrogen gas, and carrier gas) and argon gas at a constant 101.3 kPa, the partial pressure of the argon gas was decreased at a constant rate from the partial pressure of the first argon gas so that the partial pressure of the argon gas would be 0.0 kPa (partial pressure of the second argon gas) at the end of the second step. Furthermore, the partial pressure of the mixed gas was increased at a constant rate from the partial pressure of the first mixed gas so that the partial pressure of the mixed gas would be 101.3 kPa (partial pressure of the second mixed gas) at the end of the second step.

[0131] (Third step) The partial pressure of the second mixed gas was maintained at 101.3 kPa, and the partial pressure of the second argon gas was maintained at 0.0 kPa. In other words, no argon gas was supplied in the third step.

[0132] The partial pressures (kPa) of each gas at the start of the first and second processes, and the partial pressure of the first argon gas / partial pressure of nitrogen gas (indicated as "Ar / N" in the table below) ２ (This should be noted as follows:) The partial pressures (kPa) of each gas at the end of the second process and in the third process should be listed in Table 1.

[0133] After the film deposition process, consisting of the first, second, and third steps, which totaled 80 hours, was completed, the laminate of the polycrystalline silicon carbide film and the isotropic graphite substrate was removed from the CVD furnace, and the outer perimeter was processed and the laminate was divided. Furthermore, the isotropic graphite substrate was removed to obtain a disc-shaped polycrystalline silicon carbide molded body with a diameter of 150 mm and a thickness of 530 μm.

[0134] The main surface on the isotropic graphite substrate side of the obtained polycrystalline silicon carbide molded body was designated as the first main surface, and the main surface on the opposite side (growth surface) was designated as the second main surface. In the first stage of surface grinding, the first main surface and the second main surface were each surface-ground by 25 μm, thereby obtaining a disc-shaped polycrystalline silicon carbide molded body with a diameter of 150 mm and a thickness of 480 μm.

[0135] Next, in the second stage of surface grinding, the first main surface and the second main surface were surface-ground by 25 μm each using a finer grit than that used in the first stage of surface grinding, thereby obtaining a disc-shaped polycrystalline silicon carbide molded body with a diameter of 150 mm and a thickness of 430 μm.

[0136] In the first and second stages of surface grinding, it is not necessarily required that both sides be ground by the same amount of 25 μm each, as described above. However, it is preferable to grind both sides simultaneously with the same amount of material to shorten the grinding process time.

[0137] The obtained molded body was confirmed to be a polycrystalline silicon carbide molded body by diffraction spectroscopy.

[0138] The nitrogen content (mass ppm), resistivity (Ω·cm), thickness (μm), and warpage (μm) of the obtained polycrystalline silicon carbide molded body (plate-like body) were measured and calculated. The results are shown in Tables 2 and 3.

[0139] For the obtained polycrystalline silicon carbide molded body (plate-like body), the average particle diameter of silicon carbide crystals on the first main surface (indicated as "d1" in the table below), the average particle diameter of silicon carbide crystals on the second main surface (indicated as "d2" in the table below), the average particle diameter of silicon carbide crystals spanning from the first main surface to the second main surface (indicated as "d3" in the table below), the average difference between the particle diameter of silicon carbide crystals on the first main surface and the particle diameter of silicon carbide crystals on the second main surface (indicated as "average value of Δd" in the table below), and the rate of variation (= 100 × (average value of Δd) / d3) were calculated. The results are shown in Table 2.

[0140] Although not shown in Table 2, after all evaluations were completed, the second main surface of the polycrystalline silicon carbide molded body was planar-ground up to approximately the center in the thickness direction, and the average particle size of the silicon carbide crystals was measured on the surface at that location. It was confirmed that the average particle size on the first main surface, the average particle size on the second main surface, and the average particle size on the surface approximately in the center were all of similar proportions.

[0141] By the manufacturing method of the present invention described above, the particle size of the silicon carbide crystals constituting the polycrystalline silicon carbide film can be controlled to be within a predetermined range, thereby preventing a large difference in the particle size of the silicon carbide crystals between the first main surface and the second main surface. As a result, the particle size of the silicon carbide crystals from the first main surface to the second main surface is substantially constant within a predetermined range.

[0142] Furthermore, the coefficient of variation of residual stress on the first main surface (indicated as "CVRS1" in the table below), the coefficient of variation of residual stress on the second main surface (indicated as "CVRS2" in the table below), and the average value of the difference between the residual stress on the first main surface and the residual stress on the second main surface (indicated as "average value of ΔRS" in the table below) were calculated for the obtained polycrystalline silicon carbide molded body (plate-like body) using X-ray diffraction. The results are shown in Table 3.

[0143] (Examples 2-4 and Comparative Examples 1-3) Disk-shaped polycrystalline silicon carbide molded bodies with a diameter of 150 mm and a thickness of 430 μm were obtained in the same manner as in Example 1, except that the film was formed under the conditions shown in Table 1. The obtained polycrystalline silicon carbide molded bodies were confirmed to be polycrystalline silicon carbide molded bodies by diffraction spectroscopy. The results of measurements and calculations of various properties of the obtained polycrystalline silicon carbide molded bodies are shown in Tables 2 and 3.

[0144]

[0145]

[0146]

[0147] The results in Table 2 show that the polycrystalline silicon carbide molded bodies obtained in Examples 1 to 4 have low resistivity due to their high nitrogen content.

[0148] Furthermore, the average particle size of the silicon carbide crystals on the first main surface of the polycrystalline silicon carbide molded bodies obtained in Examples 1 to 4 is within an appropriate range as defined in the present invention. As a result, despite the high nitrogen content and large thickness, the residual stress on the first main surface, the residual stress on the second main surface, and the difference between the residual stress on the first main surface and the residual stress on the second main surface are reduced, resulting in less warping and excellent flatness.

[0149] Furthermore, the results in Table 1 show that in Examples 1 to 4, which satisfy the requirements of the manufacturing method of the present invention, a polycrystalline silicon carbide molded body with excellent performance can be obtained.

[0150] On the other hand, as shown in Table 2, the polycrystalline silicon carbide molded body obtained in Comparative Example 1 had a low nitrogen content and high resistivity. Furthermore, the polycrystalline silicon carbide molded bodies obtained in Comparative Examples 2 and 3 had a large amount of warping and poor flatness because the average value of the difference between the particle size of silicon carbide crystals on the first main surface and the particle size of silicon carbide crystals on the second main surface (average value of Δd) was large.

[0151] Furthermore, as shown in the results in Table 1, comparative examples 1 to 3, which did not satisfy the requirements of the manufacturing method of the present invention, did not yield polycrystalline silicon carbide molded articles with the desired performance.

[0152] According to the present invention, a polycrystalline silicon carbide molded body with excellent flatness can be obtained despite having low resistivity, high nitrogen content, and a large thickness. The polycrystalline silicon carbide molded body of the present invention is useful as a component for plasma etching equipment and the like.

[0153] This application is based on Japanese Patent Application No. 2024-171230, the contents of which are fully incorporated herein.

[0154] 1 CVD furnace 2 Isotropic graphite substrate 3 Mixer 4 Polycrystalline silicon carbide film 10 Polycrystalline silicon carbide molded body Ar Argon gas C Carrier gas R Raw material gas N Nitrogen gas A-A' Fracture line B-B' Fracture line O-O' Center line

Claims

A polycrystalline silicon carbide molded body, The nitrogen content is greater than 1000 ppm by mass and less than or equal to 5000 ppm by mass. The resistivity is 0.0100 Ω·cm or less, and The thickness is between 200 μm and 1000 μm. It is a plate-like body, The average particle size of silicon carbide crystals on the first main surface of the plate-like body is 6.0 μm to 25.0 μm. The average particle size of silicon carbide crystals on the second main surface of the plate-like body is 6.0 μm to 25.0 μm. The average particle size of silicon carbide crystals from the first main surface to the second main surface of the plate-like body is 6.0 μm to 25.0 μm, and The average difference between the particle size of silicon carbide crystals on the first main surface of the plate-like body and the particle size of silicon carbide crystals on the second main surface is between 0.1 μm and 1.5 μm. Polycrystalline silicon carbide molded body. 　 The following formula: Rate of change (%) = 100 × (mean value of Δd) / d3 (In the formula, the average value of Δd is the average difference (μm) between the particle size (μm) of silicon carbide crystals on the first main surface of the plate-like body and the particle size (μm) of silicon carbide crystals on the second main surface, and d3 is the average particle size of silicon carbide crystals extending from the first main surface to the second main surface of the plate-like body.) The polycrystalline silicon carbide molded body according to claim 1, wherein the rate of variation calculated from is 0.1% to 10.0%. The polycrystalline silicon carbide molded body according to claim 1 or 2, wherein the average value of the difference between the residual stress on the first main surface and the residual stress on the second main surface of the plate-like body, as measured by X-ray diffraction, is 10 MPa to 80 MPa. 　 A polycrystalline silicon carbide molded body according to claim 1 or 2, wherein the amount of warping is 5 μm to 50 μm. 　 A method for producing a polycrystalline silicon carbide molded body according to claim 1, A process of introducing a mixed gas consisting of a raw material gas, nitrogen gas, and a carrier gas, along with argon gas, into the atmosphere inside a CVD furnace, and forming a polycrystalline silicon carbide film on a substrate by the CVD method, The process involves processing a polycrystalline silicon carbide film to obtain a polycrystalline silicon carbide molded body. Includes, The process of forming a polycrystalline silicon carbide film includes a first step and a second step, In the first step, a mixed gas is introduced into the atmosphere inside the CVD furnace at a constant partial pressure of a first mixed gas, and argon gas is introduced into the atmosphere inside the CVD furnace at a constant partial pressure of a first argon gas to form a polycrystalline silicon carbide film on the substrate. In the second step, the mixed gas is introduced into the atmosphere inside the CVD furnace while increasing the partial pressure of the mixed gas from the partial pressure of the first mixed gas to the partial pressure of the second mixed gas at a constant rate, and the argon gas is introduced into the atmosphere inside the CVD furnace while decreasing the partial pressure of the argon gas from the partial pressure of the first argon gas to the partial pressure of the second argon gas at a constant rate, thereby forming a further polycrystalline silicon carbide film on the polycrystalline silicon carbide film formed in the first step. The partial pressure of the first argon gas is 30 kPa to 100 kPa, and In the first and second processes, the pressure of the total gas, which consists of a mixed gas comprising a raw material gas, nitrogen gas, and carrier gas, and argon gas, is between 95 kPa and 106 kPa. method.

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