Alumina sintered body, method for producing alumina sintered body, member, and plasma treatment device

Abstract

Provided is an alumina sintered body having excellent dust-generating resistance of an yttrium-based protective film formed on the surface thereof.　In this alumina sintered body, the number of pores in at least one surface is at most 12,000 pores / mm2, the open porosity is preferably at most 0.30%, the purity is preferably at least 99.20 mass%, the bending strength is preferably at least 320 MPa, the density is preferably at least 3.80 g / cm3, the maximum diameter of the pores is preferably at most 15.00 μm, the maximum depth of the pores is preferably at most 15.00 μm, and the area ratio of the pores in the surface is preferably at most 5.000%.

Description

Alumina sintered body, method for manufacturing alumina sintered body, member, and plasma processing apparatus

[0001] The present invention relates to an alumina sintered body, a method for manufacturing an alumina sintered body, a member, and a plasma processing apparatus.

[0002] Patent Document 1 discloses a "member" including, in this order, a "substrate" made of aluminum oxide (alumina) or the like and an "yttrium-based protective film" containing yttrium oxide ([Claim 1], [Claim 9], and [Claim 10]).

[0003] Furthermore, Patent Document 1 describes that the "yttrium-based protective film" is formed on the surface (film-forming surface) of the "substrate" by ion-assisted deposition (IAD) (

[0056] ), and that the "yttrium-based protective film" thus formed has excellent plasma resistance (

[0015] ).

[0004] Furthermore, Patent Document 1 also describes that the "yttrium-based protective film" has excellent plasma resistance, and therefore the "component" is used for the top plate of a plasma etching device (

[0054] ).

[0005] WO 2024 / 038674

[0006] Parts constituting a plasma processing apparatus such as a plasma etching apparatus (especially parts such as a top plate constituting the inner surface of the apparatus) may be required to have good dust generation resistance, for example, to prevent foreign matter from adhering to an object (such as a semiconductor device) undergoing plasma processing inside the apparatus.

[0007] The inventors have found through their investigations that, depending on the state (particularly the surface state) of the alumina sintered body used as the "substrate," the "yttrium-based protective film" formed on its surface (film-forming surface) by the IAD method may not have sufficient dust-generation resistance.

[0008] The present invention has been made in view of the above points, and an object of the present invention is to provide an alumina sintered body having an yttrium-based protective film formed on the surface thereof that has excellent dust generation resistance.

[0009] As a result of extensive research, the present inventors have found that the above object can be achieved by adopting the following configuration, and have completed the present invention. That is, the present invention provides the following [1] to

[20] . [1] The number of pores on at least one surface is 12,000 / mm ２ [2] The alumina sintered body according to the above item [1], having an open porosity of 0.30% or less. [3] The alumina sintered body according to the above item [1] or [2], having a purity of 99.20% by mass or more. [4] The alumina sintered body according to any one of the above items [1] to [3], having a bending strength of 320 MPa or more. [5] The alumina sintered body according to the above item [1] to [3], having a density of 3.80 g / cm ３ [6] The alumina sintered body according to any one of [1] to [4] above, wherein the maximum diameter of the pores is 15.00 μm or less and the maximum depth of the pores is 15.00 μm or less. [7] The alumina sintered body according to any one of [1] to [6] above, wherein the area ratio of the pores on the surface is 5.000% or less. [8] The alumina sintered body according to any one of [1] to [7] above, wherein the thermal conductivity is 25 W / (m·K) or more. [9] The alumina sintered body according to any one of [1] to [7] above, wherein the dielectric loss tangent at 10 GHz is 10.00×10 －４

[10] The alumina sintered body according to any one of the above items [1] to [8], wherein the number of black dots on the surface is 50 / m or less. ２The alumina sintered body according to any one of the above [1] to [9], which is the following:

[11] The alumina sintered body according to any one of the above [1] to

[10] , which is in the form of a disk having a diameter of 100 to 800 mm and a thickness of 10 to 40 mm.

[12] The alumina sintered body according to any one of the above [1] to

[11] , which is used as a substrate on the surface of which a yttrium-based protective film is formed by ion-assisted deposition.

[13] A method for producing the alumina sintered body according to any one of [1] to

[12] above, comprising: grinding an unprocessed alumina sintered body to form a ground surface having a flatness of 0.100 mm or less; polishing the ground surface using an abrasive containing abrasive grains, wherein the abrasive grains have an average grain size (median grain size) of 1 to 60 μm and the material of the abrasive grains is at least one selected from the group consisting of diamond, cubic boron nitride, silicon carbide, boron carbide, aluminum oxide, silicon oxide, tungsten carbide, and zircon.

[14] A member comprising a substrate and a yttrium-based protective film in this order, wherein the substrate is the alumina sintered body according to [1] above, and the number of needle-like crystal groups in the yttrium-based protective film is 10,000 / mm ２

[15] The yttrium-based protective film contains yttrium oxide, and in the XRD pattern, Y appears at 2θ=28.5 to 29.5°. ２ O ３ The intensity of the peak due to Al appearing at 2θ = 34.5 to 35.5° is a ２ O ３

[16] The member according to the above

[14] , wherein the coverage c expressed by the following formula (1) is 0.10 or more, where b is the intensity of the peak derived from

[16] . ２１ pieces / cm ３

[17] The member according to any one of

[14] to

[16] above, wherein the yttrium-based protective film has a Vickers hardness of 800 HV or more.

[18] The yttrium-based protective film contains yttrium oxide, and the yttrium-based protective film is ２ O ３The member according to any one of

[14] to

[17] above, wherein the orientation degree of the (222) plane is 50.0% or more.

[19] The member according to any one of

[14] to

[18] above, which is used inside a plasma processing apparatus.

[20] A plasma processing apparatus comprising the member according to any one of

[14] to

[18] above as a part constituting the inner surface.

[0010] According to the present invention, it is possible to provide an alumina sintered body having an yttrium-based protective film formed on the surface thereof that is excellent in dust generation resistance.

[0011] 1 is a schematic diagram showing an example of a member. FIG. 2 is a schematic diagram showing an apparatus used for producing an yttrium-based protective film.

[0012] The meanings of terms used in the present invention are as follows: A numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0013] [Alumina Sintered Body] In this embodiment, the number of pores is small on at least one surface (film-forming surface) among the surfaces of the alumina sintered body. The yttrium-based protective film formed by the IAD method is excellent in plasma resistance, and also excellent in dust generation resistance because it is formed on the film-forming surface of the alumina sintered body of this embodiment. The reason for this is not clear, but is presumed to be as follows.

[0014] First, when forming a yttrium-based protective film by the IAD method, the deposition surface of the substrate is irradiated with ions while the evaporation source (Y ２ O ３ (e.g., ions) are evaporated. This forms a film of granular crystals on the film-forming surface of the substrate. If pores are present on the film-forming surface of the substrate, the irradiated ions have difficulty entering the pores, and the ions are not uniformly irradiated, resulting in the formation of crystals with a large aspect ratio (needle-shaped crystals). These needle-shaped crystals are prone to peeling off from the surrounding granular crystals, causing dust generation. However, in this embodiment, there are few pores present on the film-forming surface of the substrate (alumina sintered body), so fewer needle-shaped crystals are formed, and as a result, dust generation is suppressed. In other words, the film has excellent dust generation resistance.

[0015] The alumina sintered body will be described in more detail below.

[0016] <Pores> First, the pores present on the film-forming surface of the alumina sintered body (the surface on which the yttrium-based protective film is formed) will be described.

[0017] <Number of pores> The number of pores on the film-forming surface of the alumina sintered body is specifically 12,000 pores / mm ２ The dust generation resistance of the formed yttrium protective film is superior, and therefore, the dust generation rate is 10,000 particles / mm ２ Preferably, 9,000 pieces / mm or less ２ More preferably, 8,000 pieces / mm ２ More preferably, 7,000 pieces / mm ２ Further, for the reason that the number of black dots described later is reduced, 6,500 pieces / mm ２ Particularly preferred is 6,000 pieces / mm ２ The most preferable value is 50 pores / mm2 or less. The lower limit is not particularly limited. ２ or more, and 100 pieces / mm ２ or more, and 150 pieces / mm ２ or more, and 200 pieces / mm ２ or more, and 300 pieces / mm ２ It may be more than that.

[0018] <<Maximum Pore Diameter>> The maximum pore diameter on the film-forming surface of the alumina sintered body is preferably 15.00 μm or less, more preferably 13.00 μm or less, even more preferably 10.00 μm or less, particularly preferably 7.00 μm or less, and most preferably 5.00 μm or less, because the dust-emission resistance of the formed yttrium-based protective film is superior. The lower limit is not particularly limited. The maximum pore diameter on the film-forming surface of the alumina sintered body is, for example, 0.10 μm or more, and may be 0.30 μm or more, 0.50 μm or more, 0.80 μm or more, 1.00 μm or more, or 1.20 μm or more.

[0019] <<Maximum Pore Depth>> The maximum pore depth on the film-forming surface of the alumina sintered body is preferably 15.00 μm or less, more preferably 13.00 μm or less, even more preferably 10.00 μm or less, even more preferably 7.00 μm or less, particularly preferably 6.00 μm or less, and most preferably 5.00 μm or less, because the dust-emission resistance of the formed yttrium-based protective film is superior. The lower limit is not particularly limited. The maximum pore depth on the film-forming surface of the alumina sintered body is, for example, 0.10 μm or more, may be 0.30 μm or more, 0.50 μm or more, 0.80 μm or more, 1.00 μm or more, or may be 1.20 μm or more.

[0020] <<Pore Area Ratio>> The pore area ratio on the film-forming surface of the alumina sintered body is preferably 5.000% or less, more preferably 3.000% or less, even more preferably 1.000% or less, and particularly preferably 0.500% or less, because the dust-emission resistance of the formed yttrium-based protective film is superior. The lower limit is not particularly limited. The pore area ratio on the film-forming surface of the alumina sintered body is, for example, 0.003% or more, or may be 0.010% or more, 0.030% or more, 0.040% or more, 0.050% or more, or 0.100% or more.

[0021] <<Measurement Method>> Using a Keyence laser microscope VK-X3000 (objective lens magnification: 50x), ten arbitrary locations on the surface (coating surface) of the alumina sintered body are photographed to obtain ten images (size of one field of view: 284 μm × 213 μm). Using the software in the instrument, the number, diameter, depth, and area ratio of pores with a depth of 0.5 μm or more in each image are determined. The number of pores is calculated by averaging the ten images, and the result is expressed as a 1 mm ２ The converted value is used to calculate the number of pores in the alumina sintered body (unit: pores / mm ２) for the pore area ratio, the average value of the 10 images is calculated, and the obtained value is used as the pore area ratio (unit: %) of the alumina sintered body. For the pore diameter, the maximum value is extracted from the 10 images, and the extracted maximum value is used as the maximum pore diameter (unit: μm) of the alumina sintered body. For the pore depth, the maximum value is extracted from the 10 images, and the extracted maximum value is used as the maximum pore depth (unit: μm) of the alumina sintered body.

[0022] <Number of black dots> If there are many black dots on the film-forming surface of the alumina sintered body (substrate), the appearance of the alumina sintered body may be impaired, or the yttrium-based protective film to be formed may be prone to dust generation. Therefore, from the viewpoint of appearance and dust generation resistance, it is preferable that there are few black dots. Specifically, the number of black dots on the film-forming surface of the alumina sintered body is 50 / m ２ Preferably, 40 pieces / m or less ２ More preferably, 30 or less per m ２ More preferably, 20 pieces / m or less ２ Particularly preferred is 10 pieces / m ２ The lower limit is not particularly limited, and is most preferably 0 pieces / m ２ It is assumed that the black spots are formed by the inclusion of organic impurities, for example.

[0023] The number of black dots is measured using an optical microscope. More specifically, the entire surface of the alumina sintered body on which the film is formed is observed using a Nikon NEXIV, and black-colored areas having a circle equivalent diameter of 50 μm or more are counted as black dots. ２ Convert to the number of pieces per unit.

[0024] <Composition> Next, the composition (content of metal oxides) of the alumina sintered body will be described.

[0025] 《Purity: Al ２ O ３Content of the alumina sintered body is, for example, 99.00% by mass or more, preferably 99.10% by mass or more, more preferably 99.20% by mass or more, even more preferably 99.30% by mass or more, even more preferably 99.40% by mass or more, particularly preferably 99.50% by mass or more, and most preferably 99.60% by mass or more. Meanwhile, by adding a trace amount of metal oxide to alumina, a denser alumina sintered body can be obtained. To produce a highly dense alumina sintered body without adding any metal oxide, the pressure and firing temperature during production must be increased, which tends to increase costs. Therefore, from the viewpoint of achieving both denseness and cost, the purity of the alumina sintered body is preferably 99.99% by mass or less, more preferably 99.89% by mass or less, even more preferably 99.79% by mass or less, and particularly preferably 99.69% by mass or less. The purity of the alumina sintered body is determined by the Al content of the alumina sintered body. ２ O ３ means the content of

[0026] MgO and SiO ２ Total content of MgO and SiO in the alumina sintered body ２ The total content of MgO and SiO is preferably 8,000 ppm by mass or less, more preferably 7,500 ppm by mass or less, still more preferably 7,000 ppm by mass or less, and particularly preferably 6,500 ppm by mass or less. ２ The total content of is preferably 0 ppm by mass or more, more preferably 300 ppm by mass or more, still more preferably 1,000 ppm by mass or more, and particularly preferably 2,000 ppm by mass or more, for the reason of improving the density of the alumina sintered body.

[0027] <TiO ２ Content of TiO in alumina sintered body ２ The content of TiO is preferably 3,000 ppm by mass or less, more preferably 2,000 ppm by mass or less, further preferably 1,500 ppm by mass or less, and particularly preferably 1,200 ppm by mass or less, because this can reduce the number of pores. ２The content is, for example, 0 mass ppm or more, may be 5 mass ppm or more, or may be 10 mass ppm or more.

[0028] <Impurity Content> The impurity content in the alumina sintered body is preferably 2,800 mass ppm or less, more preferably 2,300 mass ppm or less, even more preferably 2,100 mass ppm or less, and particularly preferably 1,800 mass ppm or less, because the number of pores can be reduced. On the other hand, the impurity content may be, for example, 0 mass ppm or more, 50 mass ppm or more, 100 mass ppm or more, or 1,000 mass ppm or more. The impurities may be, for example, the above-mentioned Al ２ O ３ , MgO, SiO ２ and TiO ２ Metal oxides other than those mentioned above include Fe, ２ O ３ , Na ２ Examples include O.

[0029] <<Measurement Method>> The content of the above-mentioned components (metal oxides) in the alumina sintered body is measured using inductively coupled plasma mass spectrometry (ICP-MS). More specifically, the content of a metal element (e.g., Al) is determined by ICP-MS, and this is then compared with the content of the corresponding metal oxide (e.g., Al ２ O ３ ) is considered to be the content of

[0030] <Density> The density of the alumina sintered body is set to 3.70 g / cm because the number of pores can be reduced. ３ More preferably, 3.75 g / cm ３ More preferably, 3.80 g / cm ３ More preferably, 3.85 g / cm ３ On the other hand, the density of the alumina sintered body is, for example, 4.00 g / cm ３ or less, 3.95 g / cm ３ or less, 3.93 g / cm ３ or less, 3.90 g / cm ３ The density of the alumina sintered body is determined from its mass and volume.

[0031] <Open Porosity> The open porosity of the alumina sintered body is preferably 0.30% or less, more preferably 0.25% or less, even more preferably 0.20% or less, and even more preferably 0.15% or less, because this allows the number of pores to be reduced. The lower limit is not particularly limited. The open porosity of the alumina sintered body is, for example, 0.01% or more, or may be 0.02% or more, or may be 0.05% or more.

[0032] The open porosity is determined in accordance with the calculation method for open porosity described in JIS R 1634:1998 "Method for measuring density and open porosity of sintered fine ceramics."

[0033] <Thermal Conductivity> Depending on the application, the alumina sintered body preferably has high thermal conductivity. Specifically, the thermal conductivity of the alumina sintered body is preferably 25 W / (m K) or more, more preferably 27 W / (m K) or more, even more preferably 28 W / (m K) or more, particularly preferably 29 W / (m K) or more, and most preferably 30 W / (m K) or more. The thermal conductivity of the alumina sintered body is determined in accordance with JIS R 1611:2010 "Method for measuring thermal diffusivity, specific heat capacity, and thermal conductivity of fine ceramics by the flash method."

[0034] <Dielectric loss tangent> Depending on the application, it is preferable that the alumina sintered body has a small dielectric loss. Specifically, the dielectric loss tangent (tan δ) of the alumina sintered body at 10 GHz is 10.00 × 10 －４ The following is preferred: 6.00 x 10 －４ More preferably, 3.00 x 10 －４ More preferably, 1.00 x 10 －４ The lower limit is not particularly limited, and is, for example, 0.10 × 10 －４ The dielectric loss tangent is measured in accordance with JIS C 2138:2007 "Electrical insulating materials - Measuring method of relative permittivity and dielectric loss tangent."

[0035] <Bending strength> The bending strength of the alumina sintered body is preferably 250 MPa or more, more preferably 290 MPa or more, even more preferably 320 MPa or more, and particularly preferably 350 MPa or more. There is no particular upper limit, and the bending strength of the alumina sintered body is, for example, 420 MPa or less, or may be 390 MPa or less, or may be 370 MPa or less. The bending strength of the alumina sintered body is a three-point bending strength, and is determined in accordance with JIS R 1601:2008 "Test method for room temperature bending strength of fine ceramics."

[0036] <Shape> The shape of the alumina sintered body is not particularly limited, and examples thereof include flat, disc, ring, dome, concave, and convex shapes, and is appropriately selected depending on the application. The alumina sintered body may have a through-hole in a portion thereof or may be chamfered. The thickness of the alumina sintered body (the thickness of the thickest portion of the alumina sintered body (hereinafter the same)) is, for example, 5 mm or more, and may be 10 mm or more. On the other hand, the thickness of the alumina sintered body may be, for example, 40 mm or less, and may be 35 mm or less. For example, when the substrate is disc-shaped, the diameter of the substrate may be, for example, 100 mm or more, 200 mm or more, 300 mm or more, 400 mm or more, or 500 mm or more. On the other hand, in this case, the diameter of the substrate may be, for example, 800 mm or less, and may be 600 mm or less. The size (thickness, diameter, etc.) of the alumina sintered body is measured using a three-dimensional measuring machine.

[0037] <Surface Roughness (Ra)> The surface roughness (arithmetic mean roughness Ra) of the coating surface of the alumina sintered body is preferably 0.100 μm or less, more preferably 0.080 μm or less, even more preferably 0.070 μm or less, even more preferably 0.060 μm or less, particularly preferably 0.050 μm or less, particularly preferably 0.040 μm or less, more particularly preferably 0.030 μm or less, and most preferably 0.020 μm or less. On the other hand, the lower limit is not particularly limited, and may be, for example, 0.001 μm or more, 0.005 μm or more, or even 0.010 μm or more. The surface roughness (arithmetic mean roughness Ra) of the coating surface is measured in accordance with JIS B 0601:2001.

[0038] [Method for manufacturing alumina sintered body] Next, a method for manufacturing the alumina sintered body of this embodiment will be described. Briefly, a raw alumina sintered body is subjected to a grinding process to form a ground surface, which will be described later. Next, the formed ground surface is subjected to a polishing process using abrasive grains. As a result, the alumina sintered body of this embodiment is obtained as a final product.

[0039] <Preparation of raw alumina sintered body> First, at least alumina (Al ２ O ３ A binder is added to raw material powder containing magnesia (MgO), silica (SiO ２ ), titania (TiO ２ The raw material powder may contain a metal oxide powder such as ZnO, ZnS, ZnO ...

[0040] Next, the granulated powder is molded to obtain a molded body. For molding, known methods such as cold isostatic pressing (CIP) molding and press molding are used. For example, in the case of CIP molding, the granulated powder is filled into a mold, and a molded body is produced while applying pressure. The pressure applied when producing the molded body is preferably 100 MPa or more, more preferably 200 MPa or more, and even more preferably 300 MPa or more, and preferably 600 MPa or less, more preferably 500 MPa or less, and even more preferably 400 MPa or less.

[0041] Next, the compact is degreased and then fired. This sinters the alumina contained in the raw material powder, resulting in a green alumina sintered body. Degreasing is performed, for example, by heating the compact in an air atmosphere at a temperature of 400 to 800°C for 1 to 10 hours. Firing is performed, for example, by heating the degreased compact in a hydrogen atmosphere at a temperature of 1,400 to 1,900°C for 1 to 20 hours.

[0042] The shape of the unprocessed product is not particularly limited and is appropriately selected depending on the shape of the final product (the alumina sintered body of the present embodiment). For example, if the shape of the final product is a disk, a disk-shaped unprocessed product having a greater thickness is prepared.

[0043] <Grinding> Next, the prepared unprocessed alumina sintered body is subjected to grinding. In the grinding process, for example, a flat unprocessed body (alumina sintered body) is ground in the thickness direction until it reaches the thickness of the final product. In this way, a ground surface is formed on the unprocessed body. The ground surface will be the surface on which the film is formed on the final product.

[0044] The smaller the flatness of the ground surface formed by grinding, the more uniformly the ground surface can be polished by the polishing process described later, resulting in a final product with fewer pores.Therefore, the flatness of the ground surface is preferably 0.100 mm or less, more preferably 0.050 mm or less, even more preferably 0.030 mm or less, particularly preferably 0.020 mm or less, and most preferably 0.010 mm or less.Although the lower limit is not particularly limited, from the viewpoint of cost-effectiveness, the flatness of the ground surface is preferably 0.005 mm or more.

[0045] The flatness is measured using a three-dimensional measuring machine (CRYSTA-Apex V9106, manufactured by Mitutoyo Corporation). A total of 12 flatness measurement points are set: four points 20 mm away from the center point of the grinding surface, four points 100 mm away, and four points 10 mm away from the edge toward the center point. If it is not possible to set some of the 12 points in this way, arbitrary points are set as measurement points for those points.

[0046] The alumina sintered body to be ground has low toughness, so it is preferable to select the conditions for grinding to obtain a ground surface with low flatness, taking into consideration the physical and thermal shocks caused by the grinding process.

[0047] An example of a device used for grinding is a grinding machine. Grinding machines include vertical-axis surface grinding machines and horizontal-axis surface grinding machines, with vertical-axis surface grinding machines being preferred. A vertical-axis surface grinding machine is a machine in which a grinding wheel attached to a vertical axis rotates while descending (or ascending) to perform grinding. Compared to a horizontal-axis surface grinding machine, the contact surface between the grinding wheel and the workpiece is larger and the pressure per unit area on the workpiece is smaller, making it easier to form a ground surface with low flatness.

[0048] Examples of grinding wheels used in grinding include resin-bonded grinding wheels, vitrified-bonded grinding wheels, metal-bonded grinding wheels, and electroplated grinding wheels, with metal-bonded grinding wheels being preferred. Metal-bonded grinding wheels have high processing efficiency and are less likely to cause processing damage to the workpiece, making it easier to form a ground surface with low flatness. Furthermore, compared to, for example, resin-bonded grinding wheels, they are less worn and therefore more cost-effective.

[0049] The grain size (number) of the grinding stone used in the grinding process is appropriately selected depending on the equipment to be used, and examples thereof include #140 to #2000.

[0050] Grinding is preferably performed in multiple stages using two or more types of grinding stones with different grit sizes (numbers), because this makes it easier to form a ground surface with low flatness. For example, first, a #140 to #360 grinding stone (a coarse grinding stone) is used to grind the raw product to a thickness of the desired thickness + 400 μm (rough grinding for the purpose of shape adjustment). Next, a #400 to #1000 grinding stone (a fine grinding stone) is used to grind the raw product to the desired thickness (precision grinding for the purpose of removing scratches and residual cracks). This allows for efficient grinding while minimizing processing damage.

[0051] The rotation speed of the grindstone and the cutting depth are appropriately selected depending on the equipment and grindstone used, but the rotation speed of the grindstone is preferably 1,000 to 3,000 rpm, more preferably 1,300 to 1,600 rpm. The cutting depth is preferably 1 to 5 μm per rotation.

[0052] Furthermore, because it is easy to form a ground surface with low flatness, it is preferable to perform micro-grinding after grinding the unprocessed product to a thickness several μm greater than the desired thickness. In micro-grinding, the amount of workpiece ground is preferably 0.1 μm or more, more preferably 0.5 μm or more, and preferably 10.0 μm or less, more preferably 5.0 μm or less, and even more preferably 1.0 μm or less. The cutting depth is preferably 0.005 to 0.100 μm per cut, more preferably 0.010 to 0.030 μm per cut.

[0053] Furthermore, because it is easier to form a ground surface with low flatness, it is preferable to further perform finish processing after grinding the unprocessed product to the desired thickness. In finish processing, the cutting depth is set to 0 μm per rotation, and the workpiece (object to be processed) is held while the grinding wheel is rotating. This reduces deterioration of flatness due to warping or deflection of the workpiece or vibration inherent to the device, allowing for the formation of a ground surface with low flatness. The grit size (number) of the grinding wheel used in finish processing is preferably #400 to #2000, and more preferably #800 to #1200. The holding time in finish processing is preferably 15 minutes or more, more preferably 25 minutes or more, even more preferably 35 minutes or more, and even more preferably 45 minutes or more. On the other hand, there is no particular upper limit to this holding time, and it may be, for example, 600 minutes or less, 500 minutes or less, or 400 minutes or less.

[0054] In order to reduce the temperature rise of the workpiece and discharge chips, it is preferable to use a grinding fluid during grinding. Because of their high cooling effect and ease of post-processing, water-soluble grinding fluids that are dissolved in water are preferred, and chemical solution-type water-soluble grinding fluids are particularly preferred.

[0055] In order to prevent warping of the workpiece (object to be machined), grinding may be performed not only on one side of the workpiece but also on both the top and bottom sides.

[0056] <Polishing> Next, the ground surface is polished using an abrasive containing abrasive grains. The ground surface (polished surface) that has been polished becomes the coating surface of the final product. In this way, an alumina sintered body having a coating surface with few pores is obtained as the final product.

[0057] An example of an apparatus used for polishing is a lapping apparatus. A lapping apparatus polishes (lapping polishes) a workpiece (object to be processed) by rotating it while applying pressure with platens (upper and lower platens) while a liquid abrasive containing abrasive grains is flowing through it. Examples of materials for the platens include SUS, iron, copper, tin, other metals, resins containing fillers, and ceramics. However, copper, which has good thermal conductivity, is preferred from the viewpoint of suppressing thermal damage to the workpiece.

[0058] Note that polishing may be performed after lapping. In polishing, a soft material such as felt is attached to a surface plate, and a liquid abrasive containing abrasive grains is poured over the surface, similar to lapping.

[0059] The abrasive grain material contained in the abrasive may be, for example, at least one selected from the group consisting of diamond, cubic boron nitride (CBN), silicon carbide, boron carbide, aluminum oxide (alumina), silicon oxide (silica), tungsten carbide, and zircon. Of these, diamond, silicon carbide, or alumina is preferred, with diamond being more preferred, because the workpiece (object to be machined) is an alumina sintered body. By selecting abrasive grains that are harder than the workpiece, deformation of the workpiece can be suppressed, improving polishing accuracy.

[0060] If the abrasive grains contain a large amount of impurity metals (titanium, iron, etc.), the hardness of the abrasive grains decreases, and processing performance tends to deteriorate. Therefore, the content of impurity metals (at least one selected from the group consisting of titanium and iron) in the abrasive grains is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[0061] The average particle size (median particle size) of the abrasive grains is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 6 μm or more. On the other hand, the average particle size (median particle size) of the abrasive grains is preferably 60 μm or less, more preferably 30 μm or less, and even more preferably 15 μm or less. Two or more types of abrasive grains with different average particle sizes (median particle sizes) may be mixed. This may increase the number of abrasive grains that act on polishing or improve the retention of abrasive grains, thereby improving processing efficiency.

[0062] The time required for polishing one grinding surface is preferably 10 minutes or more, more preferably 60 minutes or more, while in consideration of processing efficiency, this time is preferably 600 minutes or less, more preferably 360 minutes or less.

[0063] [Yttrium-based protective film] Next, the yttrium-based protective film formed by the IAD method on the film formation surface of the alumina sintered body of the present embodiment will be described. The yttrium-based protective film of the present embodiment has excellent plasma resistance and, as described above, also has excellent dust generation resistance.

[0064] <Number of needle-like crystal groups> As described above, the yttrium protective film is usually formed as a film of granular crystals on the film-forming surface of the substrate (alumina sintered body) by the IAD method, but if there are many pores on the film-forming surface, needle-like crystals are likely to be formed, and these needle-like crystals are likely to cause dust generation. Therefore, in order to achieve excellent dust generation resistance, it is preferable that the yttrium protective film of this embodiment has few needle-like crystals present on its surface.

[0065] Specifically, the number of needle-like crystals is 10,000 pieces / mm ２ Preferably, 8,000 pieces / mm or less ２More preferably, 6,000 pieces / mm ２ More preferably, 5,000 pieces / mm ２ More preferably, 4,200 particles / mm or less ２ Particularly preferred is 3,000 pieces / mm ２ Highly preferred is 2,000 pieces / mm ２ On the other hand, the number of needle-like crystal groups is most preferably 0 / mm ２ is preferable, but 10 pieces / mm ２ or more, and may be 100 pieces / mm ２ It may be more than that.

[0066] Here, the term "acicular crystal group" generally refers to one or more acicular crystals. More specifically, the number of acicular crystal groups is determined as follows.

[0067] First, the yttrium protective film is cut together with the substrate (alumina sintered body) so that the surface size of the yttrium protective film is 20 mm x 20 mm. Next, a platinum (Pt) thin film with a thickness of 3 to 5 nm is formed on the surface of the yttrium protective film to obtain a coated surface. The coated surface is then observed at a magnification of 30,000 times using a scanning electron microscope (SEM). More specifically, SEM images of 3,000 random fields (size of one field: 4 μm x 3 μm) on the coated surface are obtained using the SEM. The obtained SEM images are analyzed using image analysis software (ImageJ, manufactured by the National Institute of Health) to determine whether or not needle-like crystals are present in each SEM image. Here, among the crystals (crystal grains) in the SEM image, those with a ratio of the long side to the short side (long side / short side) of 1 or more and less than 5 are called "granular crystals," and those with a ratio of the long side to the short side (long side / short side) of 5 or more are called "acid crystals." Based on the number of SEM images in which needle crystals exist, ２ The number of needle-like crystals present per unit area is calculated. At this time, the decimal point is rounded off. For example, if there are three SEM images in which one or more needle-like crystals are observed out of 3,000 SEM images, the size of one SEM image is 0.000012 mm. ２(= 0.004 mm x 0.003 mm), so 0.036 mm ２ (=0.000012mm ２ In this case, there are three groups of needle-like crystals in the 1 mm ２ There are 83 groups of needle-like crystals per mm. ２ is.

[0068] <Thickness> The thickness of the yttrium protective film is, for example, 0.3 μm or more, preferably 1.0 μm or more, more preferably 1.5 μm or more, even more preferably 5.0 μm or more, and particularly preferably 10.0 μm or more. On the other hand, the thickness of the yttrium protective film is, for example, 300.0 μm or less, preferably 200.0 μm or less, more preferably 100.0 μm or less, even more preferably 50.0 μm or less, and particularly preferably 30.0 μm or less.

[0069] The thickness of the yttrium-based protective film is measured as follows: a cross section of the yttrium-based protective film is observed using a scanning electron microscope (SEM), the thickness of the yttrium-based protective film is measured at any five points, and the average value of the five measured points is taken as the thickness (unit: μm) of the yttrium-based protective film.

[0070] <Vickers Hardness> Because the plasma resistance of the yttrium-based protective film is excellent, the Vickers hardness of the yttrium-based protective film is preferably 800 HV or more, more preferably 900 HV or more, even more preferably 1000 HV or more, particularly preferably 1100 HV or more, and most preferably 1300 HV or more. On the other hand, the Vickers hardness of the yttrium-based protective film may be, for example, 1800 HV or less, or 1600 HV or less.

[0071] In order to set the Vickers hardness within the above range, it is preferable to produce an yttrium-based protective film by the production method described below.

[0072] The Vickers hardness of the yttrium-based protective film is determined in accordance with JIS Z 2244:2009 "Vickers hardness test - Test method." More specifically, it is the Vickers hardness (HV0.005) determined when a test force of 4.9 mN (0.049 N) is applied using a micro Vickers hardness tester (HM-220, manufactured by Mitutoyo Corporation) with a diamond indenter having a facing angle of 136°.

[0073] <Porosity> Because the plasma resistance of the yttrium-based protective film is excellent, the porosity of the yttrium-based protective film is preferably less than 0.50% by volume, more preferably 0.30% by volume or less, even more preferably 0.20% by volume or less, and particularly preferably 0.10% by volume or less.

[0074] In order to set the porosity within the above range, it is preferable to produce the yttrium-based protective film by the production method described below.

[0075] The porosity of the yttrium-based protective film is determined as follows. First, a focused ion beam (FIB) is used to perform a slope process in the thickness direction at an angle of 52° from the surface of the yttrium-based protective film toward the substrate on a portion of the yttrium-based protective film and a substrate described later, thereby exposing a cross section. The exposed cross section is observed at a magnification of 20,000 times using a field emission scanning electron microscope (FE-SEM), and cross-sectional images are taken. Cross-sectional images are taken at multiple locations. Specifically, for example, when the yttrium-based protective film is circular, images are taken at a total of five points, including one point at the center of the surface of the yttrium-based protective film and four points located 10 mm away from the outer periphery, and the size of the cross-sectional images is 6 μm × 5 μm. When the thickness of the yttrium-based protective film is 5 μm or more, cross-sectional images are taken at multiple locations so that the entire cross section of the yttrium-based protective film can be observed in the thickness direction. Subsequently, the obtained cross-sectional image is analyzed using image analysis software (ImageJ, manufactured by the National Institute of Health) to identify the area of ​​the pore portion in the cross-sectional image. The ratio of the area of ​​the pore portion to the area of ​​the entire cross section of the yttrium protective film is calculated, and this is regarded as the porosity (unit: volume%) of the yttrium protective film. Note that for pores that are so fine that they cannot be detected by image analysis software (pores with a pore diameter of 20 nm or less), their area is regarded as 0.

[0076] <Composition> The yttrium protective film is, for example, yttrium oxide (Y ２ O ３ In this case, the Y of the yttrium protective film ２ O ３ The content of Y is preferably 95% by mass or more, more preferably 98% by mass or more, and may be 100% by mass. ２ O ３ Yttrium-based protective film produced using only ２ O ３ The content satisfies the above range.

[0077] <Degree of Orientation> In order to prevent cracks (including wrinkles) from occurring in the yttrium-based protective film, the Y of the yttrium-based protective film is ２ O ３ The higher the orientation degree of the (222) plane (hereinafter also simply referred to as "orientation degree"), the better. Therefore, the orientation degree of the yttrium-based protective film is, for example, 50.0% or more, preferably 65.0% or more, more preferably 80.0% or more, even more preferably 85.0% or more, even more preferably 90.0% or more, particularly preferably 93.0% or more, more particularly preferably 95.0% or more, very preferably 98.0% or more, and most preferably 99.0% or more. In order to set the orientation degree within the above range, it is preferable to manufacture the yttrium-based protective film by the manufacturing method described below. The orientation degree is determined by measuring the degree of orientation of the Y in the XRD pattern of the yttrium-based protective film. ２ O ３ The peak intensity of the (222) plane is the ratio (unit: %) of the peak intensity of the (222) plane to the total peak intensity of each plane being 100.

[0078] The XRD pattern of the yttrium protective film was obtained by XRD measurement in micro-area 2D (two-dimensional) mode using an X-ray diffractometer (D8 DISCOVER Plus, manufactured by Bruker) under the following conditions: X-ray source: CuKα ray (output: 45 kV, current: 120 mA) Scanning range: 2θ = 10° to 80° Step time: 0.2 s / step Scan speed: 10° / min Step width: 0.02° Detector: Multimode detector EIGER (2D mode) Incident optical system: Multilayer mirror + 1.0 mmφ microslit + 1.0 mmφ collimator Receiving optical system: OPEN

[0079] <Coating Degree c> The surface of the yttrium-based protective film formed on the film-forming surface of the substrate (alumina sintered body) is subjected to XRD measurement under the above conditions to obtain an XRD pattern. ２ O ３ The peak due to Y ２ O ３In this case, it is preferable that the intensity of the yttrium protective film (Y ２ O ３ ) is the substrate (Al ２ O ３ Specifically, the Y θ appearing at 2θ=28.5 to 29.5° is ２ O ３ The intensity of the peak due to Al appearing at 2θ = 34.5 to 35.5° is a ２ O ３ When the intensity of the peak derived from is b, the coverage c represented by the following formula (1) is preferably 0.10 or more, more preferably 0.30 or more, even more preferably 0.50 or more, particularly preferably 0.70 or more, and most preferably 0.90 or more. The upper limit of the coverage c is 1.00. c=a / (a+b) (1)

[0080] <Crystallite size> For example, particles (particles) that fall off from a member exposed to plasma can adhere to a semiconductor substrate and become foreign matter that causes defects in the circuit. At this time, the smaller the particle size, the more the occurrence of defects can be suppressed. Therefore, the crystallite size of the yttrium protective film is preferably 40.0 nm or less, more preferably 30.0 nm or less, even more preferably 20.0 nm or less, particularly preferably 15.0 nm or less, and most preferably 10.0 nm or less.

[0081] On the other hand, the larger the crystallite size of the yttrium protective film, the smaller the change in crystallite size when heated, making it more stable and resulting in excellent heat resistance. From this viewpoint, the crystallite size of the yttrium protective film is preferably 6.0 nm or more, more preferably 6.5 nm or more, and even more preferably 7.0 nm or more.

[0082] In order to set the crystallite size within the above range, it is preferable to produce the yttrium-based protective film by the production method described below.

[0083] The crystallite size of the yttrium-based protective film is determined using Scherrer's equation based on the XRD pattern data obtained by XRD measurement of a mirror-polished yttrium-based protective film.

[0084] <Number of Hydrogen Atoms> It is preferable that the number of hydrogen atoms in the yttrium-based protective film is small. This results in excellent plasma resistance of the yttrium-based protective film. The reason for this is presumed to be as follows: If there is a large amount of hydrogen in the yttrium-based protective film, this hydrogen is more likely to react with fluorine contained in the plasma (or the gas used to generate the plasma), and as a result, the yttrium-based protective film is more likely to be damaged. On the other hand, if there is less hydrogen in the yttrium-based protective film, the reaction with fluorine is relatively reduced, and damage to the yttrium-based protective film is suppressed.

[0085] Specifically, the number of hydrogen atoms in the yttrium protective film is 5.00×10 ２１ pieces / cm ３ The following is preferred: 4.00 x 10 ２１ pieces / cm ３ More preferably, 3.00 x 10 ２１ pieces / cm ３ More preferably, 2.50 x 10 ２１ pieces / cm ３ More preferably, the following is true: 2.00 x 10 ２１ pieces / cm ３ Even more preferably, the following is true: 1.50 x 10 ２１ pieces / cm ３ The following is particularly preferred: 1.00 x 10 ２１ pieces / cm ３ The following is particularly preferred: 0.50 x 10 ２１ pieces / cm ３ Highly preferred is 0.30 x 10 ２１ pieces / cm ３ The following are most preferred:

[0086] The hydrogen in the yttrium-based protective film is likely to be due to the influence of moisture contained in the substrate, which will be described later. In particular, when the substrate is made of ceramics (such as sintered alumina), the number of hydrogen atoms in the formed yttrium-based protective film can be reduced by heating (preheating) the substrate before forming the yttrium-based protective film.

[0087] On the other hand, the number of hydrogen atoms in the yttrium protective film is, for example, 0.02×10 ２１ pieces / cm ３ or more, 0.04 × 10２１ pieces / cm ３ It may be more than that.

[0088] The number of hydrogen atoms in the yttrium protective film was measured using a secondary ion mass spectrometer (model IMS-6f, manufactured by Ametec Co., Ltd.) to measure the number of hydrogen atoms in the yttrium protective film by measuring the primary ion species Cs ＋ The measurement is performed under the conditions of a primary acceleration voltage of 15.0 kV, a detection area of ​​φ8 μm, and a measurement depth of 500 nm.

[0089] <Compressive Stress> The stress (internal stress, residual stress) of the yttrium protective film is preferably compressive stress rather than tensile stress. The compressive stress of the yttrium protective film is preferably 100 MPa or more, more preferably 300 MPa or more, even more preferably 500 MPa or more, particularly preferably 700 MPa or more, and most preferably 1,200 MPa or more. On the other hand, the compressive stress of the yttrium protective film is preferably 1,700 MPa or less, more preferably 1,600 MPa or less, even more preferably 1,500 MPa or less, and particularly preferably 1,400 MPa or less.

[0090] The compressive stress of the yttrium-based protective film is determined as follows: A yttrium-based protective film is formed on a quartz glass substrate, and the surface shape of the formed yttrium-based protective film is measured using a surface shape measuring device (Surfcom NEX 241 SD2-13, manufactured by Tokyo Seimitsu Co., Ltd.), and the compressive stress (film stress σ) of the yttrium-based protective film is determined using Stoney's formula (the following formula): σ=Yd ２ / (6c(1-ν)t) In the above formula, σ is film stress, Y is Young's modulus of the substrate, d is thickness of the substrate, ν is Poisson's ratio of the substrate, t is thickness of the yttrium protective film, and c is radius of curvature.

[0091] [Members] Next, the members of this embodiment will be described. First, the members of this embodiment will be roughly described based on FIG.

[0092] FIG. 1 is a schematic diagram showing an example of a member 6. As shown in FIG. 1, in the member 6, the yttrium-based protective film 4 is formed on a film-forming surface 5a of a substrate 5. That is, the member 6 has the substrate 5 and the yttrium-based protective film 4, in this order. The alumina sintered body of the present embodiment described above is used as the substrate 5. The yttrium-based protective film 4 is also as described above. That is, the substrate 5 and the yttrium-based protective film 4 have already been described, and therefore will not be described here.

[0093] <Use of Member> The member is used, for example, as a component constituting a plasma processing apparatus, in particular as a component such as a top plate constituting the inner surface of the plasma processing apparatus. Examples of plasma processing apparatuses include plasma etching apparatuses, plasma CVD apparatuses, plasma ALD apparatuses, and plasma modification apparatuses, and these apparatuses are used, for example, in the manufacture of semiconductor devices. However, the use of the member is not limited to these.

[0094] [Method of Manufacturing Yttrium-Based Protective Film and Member] Next, a method of manufacturing the yttrium-based protective film of this embodiment will be described. The following description also serves as a description of a method of manufacturing the member of this embodiment.

[0095] In this embodiment, an ion-assisted deposition (IAD) method is used. Schematically, in a vacuum, an evaporation source (Y ２ O ３ , Y.F. ３ The yttrium protective film is formed by evaporating the yttrium-based protective film.

[0096] By using the IAD method, a very dense yttrium-based protective film can be formed. That is, the resulting yttrium-based protective film has a small porosity. In contrast, yttrium-based protective films obtained by methods such as thermal spraying, aerosol deposition (AD), and ion plating (IP) tend to have many remaining pores.

[0097] <Apparatus Configuration> FIG. 2 is a schematic diagram showing an apparatus used to produce an yttrium-based protective film. The apparatus shown in FIG. 2 has a chamber 11. The interior of the chamber 11 can be evacuated by driving a vacuum pump (not shown). Inside the chamber 11, crucibles 12 and 13 and an ion gun 14 are arranged, and a holder 17 is arranged above them. The holder 17 is integrated with a support shaft 16 and rotates with the rotation of the support shaft 16. A heater 15 is arranged around the holder 17. The holder 17 holds the above-mentioned substrate 5 with its film-forming surface facing downward. The substrate 5 held by the holder 17 rotates with the rotation of the holder 17 while being heated by the heater 15. Furthermore, quartz-crystal film thickness monitors 18 and 19 are attached to the chamber 11.

[0098] <Formation of Yttrium-Based Protective Film> In the apparatus shown in FIG. 2, a protective film of yttrium oxide (Y ２ O ３ First, the evaporation source Y is placed in one or both of the crucibles 12 and 13. ２ O ３ After the substrate 5 is held by the holder 17, the inside of the chamber 11 is evacuated to a vacuum. Next, the heater 15 is driven while the holder 17 is rotated. This causes the substrate 5 to rotate while being heated. In this state, ion-assisted deposition is performed to form a film on the substrate 5. That is, while ions (ion beam) are irradiated from the ion gun 14, the evaporation source Y filled in one or both of the crucibles 12 and 13 is evacuated. ２ O ３ The evaporation source is melted and evaporated by irradiating it with an electron beam (not shown). In this way, the evaporated evaporation source adheres to the film-forming surface of the substrate 5, and yttrium oxide (Y ２ O ３ ) is formed.

[0099] The ions irradiated by the ion gun 14 are preferably ions of at least one element selected from the group consisting of oxygen, argon, neon, krypton, and xenon. It is more preferable to use ions of at least two elements selected from the group consisting of oxygen, argon, neon, krypton, and xenon, and it is even more preferable to use oxygen and argon ions in combination.

[0100] <Pressure in the Chamber> Film formation is performed in a vacuum. Specifically, the pressure inside the chamber 11 is 6×10 －２ Pa or less is preferable, and 5 × 10 －２ Pa or less is more preferable, and 3×10 －２ On the other hand, the pressure inside the chamber 11 is preferably 1×10 Pa or less. －６ Pa or more is preferable, and 1×10 －５ Pa or more is preferable, and 1×10 －４ Pa or more is more preferable.

[0101] <<Temperature of Substrate>> Because a yttrium-based protective film having excellent plasma resistance can be easily formed, the temperature of the substrate 5 heated by the heater 15 during film formation is preferably 200° C. or higher, more preferably 250° C. or higher, and even more preferably 300° C. or higher. On the other hand, this temperature is preferably 700° C. or lower, preferably 650° C. or lower, and more preferably 600° C. or lower.

[0102] <<Film Formation Rate>> The rate at which the evaporation sources in the crucibles 12 and 13 evaporate and a film is formed (film formation rate) is monitored in advance using quartz film thickness monitors 18 and 19, respectively. The film formation rate is adjusted by controlling the conditions of the electron beam irradiated onto the evaporation sources and the conditions of the ion beam from the ion gun 14 (current value, current density, etc.). During the formation of the yttrium protective film, the film formation rate (unit: nm / min) of each evaporation source is adjusted to a desired value.

[0103] Evaporation source Y ２ O ３The deposition rate of the evaporation source Y is preferably 1.00 nm / min or more, more preferably 1.50 nm / min or more, even more preferably 2.00 nm / min or more, and particularly preferably 2.50 nm / min or more. ２ O ３ The film formation rate is preferably 20.00 nm / min or less, more preferably 15.00 nm / min or less, even more preferably 10.00 nm / min or less, even more preferably 5.00 nm / min or less, and particularly preferably 3.50 nm / min or less.

[0104] <Ion Irradiation Conditions> The distance between the ion gun 14 and the substrate 5 is preferably 700 mm or more, more preferably 750 mm or more, still more preferably 800 mm or more, and particularly preferably 850 mm or more. For the same reason, the distance between the ion gun 14 and the substrate 5 is preferably 1,050 mm or less, and more preferably 1,000 mm or less.

[0105] The current value of the ion beam is preferably 1,000 mA or more, more preferably 1,500 mA or more, while the current value of the ion beam is preferably 3,000 mA or less, more preferably 2,500 mA or less.

[0106] The ion beam current density was 40 μA / cm ２ More than 65 μA / cm is preferable. ２ More preferably, 75 μA / cm ２ More preferably, 77 μA / cm ２ On the other hand, the ion beam current density is preferably 140 μA / cm ２ Preferably, 120 μA / cm or less ２ More preferably, 100 μA / cm or less ２ The following is even more preferred:

[0107] <<Ar / O Ratio>> As described above, it is preferable to use a combination of argon ions and oxygen ions as ions irradiated from the ion gun 14. In this case, the Ar / O ratio, which is the ratio of the amount of argon (Ar) ions to the amount of oxygen (O) ions, is preferably greater than 2 / 50, more preferably greater than 4 / 50, and particularly preferably greater than 4 / 50. On the other hand, the Ar / O ratio is, for example, 25 / 50 or less, preferably 20 / 50 or less, more preferably 15 / 50 or less, and even more preferably 12 / 50 or less.

[0108] The Ar / O ratio is the amount of argon (Ar) ions (unit: W / m) irradiated from the ion gun 14 toward the substrate 5. ２ ), and the amount of oxygen (O) ions (unit: W / m) irradiated from the ion gun 14 toward the substrate 5. ２ ) where "W / m ２ " is a unit of kinetic energy (ion energy flux) across a unit area in a unit time.

[0109] <Preheating of substrate> Because the crystal water of the substrate is less likely to be contained in the yttrium-based protective film, it is preferable to heat the substrate at a high temperature (preheating) before forming the yttrium-based protective film. The preheating temperature is preferably 300°C or higher, more preferably 400°C or higher, even more preferably 450°C or higher, and particularly preferably 500°C or higher. On the other hand, the preheating temperature is, for example, 800°C or lower, preferably 750°C or lower, and more preferably 700°C or lower.

[0110] The preheating time is preferably 60 minutes or more, more preferably 120 minutes or more, even more preferably 240 minutes or more, and particularly preferably 480 minutes or more, while the preheating time is preferably 1200 minutes or less, more preferably 1000 minutes or less, even more preferably 800 minutes or less, and particularly preferably 600 minutes or less.

[0111] The pre-heating atmosphere is, for example, the air atmosphere.

[0112] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples described below. Examples 1 to 16 are examples, and Examples 17 to 19 are comparative examples.

[0113] <Production of Alumina Sintered Body> An alumina sintered body having the properties shown in Table 1 below was produced as follows.

[0114] <<Preparation of raw alumina sintered body>> Al ２ O ３ powder, MgO powder, SiO ２ Powder and TiO ２ Powder (Fe as impurities ２ O ３ and Na ２ The raw material powder was prepared by mixing the raw material powder and the sintered body (including 0) to obtain the composition shown in Table 1 below. PVA was added as a binder to the raw material powder to prepare a granulated powder. The prepared granulated powder was filled into a molding die, and a compact was fabricated by CIP molding at a pressure of 120 MPa. The fabricated compact was degreased by heating at 600°C for 5 hours in an air atmosphere. The degreased compact was then sintered by heating at 1,550°C for 10 hours in a hydrogen atmosphere. In this way, a green alumina sintered body was produced. Other conditions included an average particle size of 0.3 to 2 μm for the raw material powder, 1 to 3 parts by mass of binder added per 100 parts by mass of the raw material powder, and the particle size of the granulated powder used in CIP molding was appropriately adjusted within the range of 30 to 200 μm.

[0115] <Grinding> Next, the unprocessed alumina sintered body was ground using a vertical axis surface grinding machine to form a ground surface with the flatness shown in Table 1 below. A metal-bonded grinding wheel was used as the grinding wheel, and a chemical solution-type water-soluble grinding fluid was used as the grinding fluid. More specifically, rough grinding (cut depth: 3 μm / pass) was first performed using a #200 grinding wheel, followed by precision grinding (cut depth: 2 μm / pass) using a #1000 grinding wheel, and then fine grinding (cut depth: 0.020 μm / pass) using a #1000 grinding wheel. Subsequently, finish grinding with a cut depth of 0 μm / pass was performed using a #1000 grinding wheel for the holding time shown in Table 1 below. Other conditions included a grinding wheel rotation speed of 1,400 rpm.

[0116] <<Polishing>> Next, the formed ground surface was polished using an abrasive containing abrasive grains (material: diamond) with an average particle size shown in Table 1 below. The polishing was performed using a lapping device (platen material: copper). In this way, an alumina sintered body was manufactured. The manufactured alumina sintered body has the ground surface (polished surface) that has been polished as a film formation surface. As another condition, the time for polishing the ground surface was appropriately adjusted so that the properties (number of pores, etc.) of the obtained alumina sintered body would be as shown in Table 1 below.

[0117] <Production of Member> Next, using the produced alumina sintered body as a substrate, an yttrium-based protective film was formed in the apparatus described with reference to FIG. 2, thereby producing a member.

[0118] More specifically, first, the substrate was held on a holder in a chamber and preheated in the air at the preheating temperature shown in Table 1 below for 600 minutes.

[0119] Thereafter, an yttrium-based protective film was formed on the deposition surface of the substrate using the IAD method under the manufacturing conditions shown in Table 1. Manufacturing conditions not listed in Table 1 included a distance of 950 mm between the ion gun and the substrate, and an ion beam current of 2,000 mA. When forming the yttrium-based protective film, argon (Ar) ions and oxygen (O) ions were irradiated from the ion gun toward the substrate at an Ar / O ratio of 6 / 50.

[0120] The yttrium-based protective film thus formed was subjected to the measurements shown in Table 1 below using the methods described above. The results are shown in Table 1 below.

[0121] <Plasma Resistance (Etching Amount)> The yttrium-based protective film of the manufactured member was subjected to plasma etching to evaluate plasma resistance. More specifically, the member was first cut into a size of 20 mm x 20 mm x 2 mm so that the surface size of the yttrium-based protective film was 20 mm x 20 mm. Next, half of the surface was covered with polyimide tape (P-222 manufactured by Nitto Denko Corporation) with a total thickness of 100 μm. In this way, a sample was prepared. Thereafter, the sample was placed on the stage of a plasma etching device (EXAM manufactured by Shinko Seiki Co., Ltd.), and CF ４ / O ２ Plasma etching was carried out using a mixed gas of Ar / Ar. The output was 550 W, the pressure was 3 Pa, and the etching time was 60 minutes. After etching, the polyimide tape was peeled off, and the step between the covered surface and the exposed surface was measured using a stylus surface profiler, Dektak-XT (manufactured by ULVAC, Inc.). Measurements were carried out at three points, and the average value of the three points was calculated as the amount of etching (unit: nm). The results are shown in Table 1 below. The smaller the amount of etching, the better the plasma resistance can be evaluated.

[0122] <Dust generation resistance (number of particles)> First, the manufactured member was cut to prepare a sample. More specifically, the member was cut into a size of 20 mm x 20 mm x 2 mm so that the surface size of the yttrium protective film was 20 mm x 20 mm. Next, a disk-shaped silicon wafer with a diameter of 6 inches (150 mm) was placed on the stage of a plasma etching device (EXAM manufactured by Shinko Seiki Co., Ltd.), and the sample was placed at the center position on the surface. Thereafter, CF ４ / O ２ Plasma etching was performed using a mixed gas of Ar and Ar. The output was 550 W, the pressure was 3 Pa, and the etching time was 60 minutes. After etching, the silicon wafer and sample were removed from the plasma etching device, and then a particle inspection device (LODAS manufactured by LAZIN) was used to detect particles with a diameter of 100 nm or more attached to the silicon wafer. The number of particles was counted, excluding the 3 mm wide outer periphery and the 40 mm diameter central portion (including the portion where the sample was placed) of the silicon wafer. The results are shown in Table 1 below. The lower the particle count, the better the dust generation resistance can be evaluated.

[0123]

[0124]

[0125]

[0126] <Summary of Evaluation Results> As shown in Table 1 above, the number of pores on the film formation surface was 12,000 / mm ２ In Examples 1 to 16, which used the following alumina sintered body as the substrate, the dust generation resistance of the yttrium-based protective film was better than in Examples 17 to 19, which did not satisfy this requirement.

[0127] The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2024-075872 filed on May 8, 2024 are hereby incorporated by reference as the disclosure of the present invention.

[0128] 4: Yttrium protective film 5: Substrate 5a: Film formation surface 6: Member 11: Chamber 12, 13: Crucible 14: Ion gun 15: Heater 16: Support shaft 17: Holder 18, 19: Quartz film thickness monitor

Claims

1. The number of pores on at least one surface is 12,000 / mm ２ The following is an alumina sintered body.

2. The alumina sintered body according to claim 1, having an open porosity of 0.30% or less.

3. The alumina sintered body according to claim 1, having a purity of 99.20% by mass or more.

4. The alumina sintered body according to claim 1, having a bending strength of 320 MPa or more.

5. Density is 3.80 g / cm ３ The alumina sintered body according to claim 1 .

6. The alumina sintered body according to claim 1, wherein the maximum diameter of the pores is 15.00 μm or less, and the maximum depth of the pores is 15.00 μm or less.

7. The alumina sintered body according to claim 1, wherein the area ratio of the pores on the surface is 5.000% or less.

8. The alumina sintered body according to claim 1, having a thermal conductivity of 25 W / (m·K) or more.

9. The dielectric loss tangent at 10 GHz is 10.00 x 10 －４ The alumina sintered body according to claim 1, wherein:

10. The number of black dots on the surface is 50 / m ２ The alumina sintered body according to claim 1, wherein:

11. The alumina sintered body according to claim 1, which is in the form of a disk having a diameter of 100 to 800 mm and a thickness of 10 to 40 mm.

12. The alumina sintered body according to claim 1, which is used as a substrate on the surface of which a protective yttrium film is formed by ion-assisted deposition.

13. A method for producing an alumina sintered body according to any one of claims 1 to 12, comprising: grinding an unprocessed alumina sintered body to form a ground surface having a flatness of 0.100 mm or less; polishing the ground surface using an abrasive containing abrasive grains; the abrasive grains have an average grain size (median grain size) of 1 to 60 μm; and the material of the abrasive grains is at least one selected from the group consisting of diamond, cubic boron nitride, silicon carbide, boron carbide, aluminum oxide, silicon oxide, tungsten carbide, and zircon.

14. A member comprising a substrate and an yttrium-based protective film in this order, wherein the substrate is the alumina sintered body according to claim 1, and the number of needle-like crystal groups in the yttrium-based protective film is 10,000 pieces / mm ２ The following are the components.

15. The yttrium-based protective film contains yttrium oxide, and in the XRD pattern, Y appears at 2θ=28.5 to 29.5°. ２ O ３ The intensity of the peak due to Al appearing at 2θ = 34.5 to 35.5° is a ２ O ３ The member according to claim 14, wherein the coverage c represented by the following formula (1) is 0.10 or more, where b is the intensity of the peak derived from the above formula (1): c = a / (a + b) (1) 16. The number of hydrogen atoms in the yttrium protective film is 5.00 × 10 ２１ pieces / cm ３ 15. The member of claim 14, wherein:

17. The member according to claim 14, wherein the yttrium-based protective film has a Vickers hardness of 800 HV or more.

18. The yttrium-based protective film contains yttrium oxide, and the yttrium-based protective film is Y ２ O ３ The member according to claim 14, wherein the orientation degree of the (222) plane is 50.0% or more.

19. The component of claim 14 used inside a plasma processing device.

20. A plasma processing apparatus comprising the member according to any one of claims 14 to 18 as a component constituting the inner surface.

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